Note: Descriptions are shown in the official language in which they were submitted.
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APPARATUS AND METHODS FOR DETECTING OBSCURED FEATURES
Related Applications
[0001] This application claims priority to U.S. Patent Application No.
16/360,913,
entitled "APPARATUS AND METHODS FOR DETECTING OBSCURED
FEATURES," filed 21 March 2019, the disclosure of which is hereby incorporated
herein in its entirety by reference.
Technical Field
[0002] The present disclosure relates generally to devices to detect a
presence of
obscured features behind opaque, solid surfaces, and more specifically to
devices to
locate beams and studs behind walls and joists beneath floors.
Background
[0003] Locating obscured features such as beams, studs, joists and other
elements behind walls and beneath floors is a common problem encountered
during
construction, repair and home improvement activities. For example, often a
desire
arises to cut or drill into a wall, floor, or other supported surface with the
aim of
creating an opening in the surface while avoiding the underlying support
elements. In
these instances, knowing where the support elements are positioned before
beginning can be desirable so as to avoid cutting or drilling into the support
elements. On other occasions, one may desire to anchor a heavy object such as
a
picture or shelf to a support element obscured by a supported surface. In
these
cases, it is often desirable to install a fastener through the supported
surface in
alignment with an underlying support element. However, with the wall, floor or
supported surface in place, the location of the support element is not
visually
detectable.
[0004] A variety of rudimentary techniques have been employed in the past
with
limited success to address the problem of locating underlying features
obscured by
an overlying surface. These techniques include driving small pilot nails
through
various locations in the overlying surface until an underlying support element
is
encountered and then covering over holes in the surface that did not reveal
the
location of the underlying support element. A less destructive technique
comprises
tapping on the overlying surface with the aim of detecting audible changes in
the
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sound which emanates from the surface when there is a support element beneath
or
behind the area of the surface being tapped. This technique is ineffective,
however,
because the accuracy of the results depends greatly on the judgment and skill
of the
person tapping and listening to search for the underlying support element, and
because the sound emitted by the tapping is heavily influenced by the type and
density of the surface being examined.
[0005] Magnetic detectors have also been employed to find obscured support
elements with the detector relying on the presence of metallic fasteners, such
as
nails or screws, in the wall and support element to trigger a response in the
detector.
However, since metallic fasteners are spaced at discrete locations along the
length
of a support, a magnetic detector may pass over a length of the support where
no
fasteners are located, thereby failing to detect the presence of the obscured
support
element.
[0006] Electronic sensors have also been employed to detect obscured
features
behind opaque surfaces. These detectors sense changes in capacitance on the
examined surface that result from the presence of features positioned behind,
beneath or within the surface. These changes in capacitance are detectable
through
a variety of surfaces such as wood, sheetrock, plaster and gypsum and do not
rely
on the presence of metal fasteners in the surface or obscured feature for
activation
of the sensor. However, conventional electronic detectors may suffer from a
significant shortcoming. Conventional obscured feature detectors may have
difficulty
accurately compensating for the thickness and density of the detected surface,
which
negatively impact accuracy.
Summary
[0007] The present disclosure advantageously addresses one or more of the
aforementioned deficiencies in the field of obscured feature detection by
providing an
accurate, simple to use and inexpensively manufactured obscured feature
detector.
The detector can be employed by placing the device against the examined
surface
and reading the location of all features present beneath the surface where the
device
is positioned. The detector is able to accurately read through different
surface
materials and different surface thicknesses.
[0008] Additional aspects and advantages will be apparent from the
following
detailed description of preferred embodiments, which proceeds with reference
to the
accompanying drawings.
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Brief Description of the Drawings
[0009] FIG. 1 illustrates an advanced obscured feature detector, according
to one
embodiment, placed on a piece of sheetrock and detecting an obscured feature.
[0010] FIG. 2 is a perspective view of the obscured feature detector of
FIG. 1.
[0011] FIG. 3 is an illustrative drawing that shows sensor plates and
activated
indicators of the obscured feature detector of FIG. 1, with the activated
indicators
signaling a position of the hidden obscured feature.
[0012] FIG. 4 is a diagram of a circuit of an obscured feature detector,
according
to one embodiment.
[0013] FIG. 5 is a diagram of a controller of an obscured feature detector,
according to one embodiment.
[0014] FIG. 6 is a cross-sectional view of an obscured feature detector,
according
to one embodiment, including a housing, with light pipes and a button, and a
printed
circuit board.
[0015] FIG. 7 is a prior art obscured feature detector placed on a
comparatively
thinner surface.
[0016] FIG. 8 is a prior art obscured feature detector placed on a
comparatively
thicker surface.
[0017] FIG. 9 shows a side view of a prior art obscured feature detector,
illustrating primary sensing field zones for several sensor plates.
[0018] FIG. 10 shows an elevation view of a bottom surface of a prior art
obscured feature detector, illustrating the primary sensing field zones for
several
sensor plates.
[0019] FIG. 11 is a flow diagram of a method of detecting an obscured
feature
behind a surface, according to one embodiment.
[0020] FIG. 12 is a prior art plate configuration for an obscured feature
detector
with a common plate.
[0021] FIG. 13 is a plate configuration for an obscured feature detector
with a
shortened common plate.
[0022] FIG. 14 illustrates the electric field lines for the prior art plate
configuration
of FIG. 12.
[0023] FIG. 15 illustrates the electric field lines for the plate
configuration of FIG.
13.
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[0024] FIG. 16 illustrates the electric field lines for a sensor plate
array with
multiple common plates.
[0025] FIG. 17 is a flow chart illustrating a method of detecting an
obscured
feature behind a surface with a plate configuration with a shortened ground
plane,
according to one embodiment.
[0026] FIG. 18 illustrates the electric field lines for a sensor plate
array with
narrow end-plates.
[0027] FIG. 19 illustrates the electric field lines for a sensor plate
array with
trapezoidal end-plates.
[0028] FIG. 20 illustrates an obscured feature detector, according to one
embodiment, positioned on a piece of sheetrock and detecting an obscured
feature.
[0029] FIG. 21 is a perspective view of the obscured feature detector of
FIG. 20.
[0030] FIG. 22 is an illustrative drawing that shows sensor plates and
activated
indicators of the obscured feature detector of FIG. 20, with the activated
indicators
signaling a position of the hidden obscured feature.
[0031] FIG. 23 is a diagram of a circuit of an obscured feature detector,
according
to one embodiment.
[0032] FIG. 24 is a diagram of a controller of an obscured feature
detector,
according to one embodiment.
[0033] FIG. 25 illustrates a routing of sensor plate traces of an obscured
feature
detector, according to one embodiment. In the illustrated embodiment, each of
the
sensor plate traces has substantially similar trace length and the traces are
surrounded by an active shield.
[0034] FIG. 26 is a diagram of a sensor plate configuration of an obscured
feature
detector, according to another embodiment.
[0035] FIG. 27 is a cross-sectional view of an obscured feature detector,
according to one embodiment, including a housing, with light pipes and a
button, and
a printed circuit board.
[0036] FIG. 28 illustrates a sensor plate group with four sensor plates.
[0037] FIG. 29 illustrates a sensor plate group with six sensor plates.
[0038] FIG. 30 is a prior art obscured feature detector placed on a
comparatively
thinner surface.
[0039] FIG. 31 is a prior art obscured feature detector placed on a
comparatively
thicker surface.
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[0040] FIG. 32 shows a side view of a prior art obscured feature detector,
illustrating primary sensing field zones for several sensor plates.
[0041] FIG. 33 shows an elevation view of a bottom surface of a prior art
obscured feature detector, illustrating the primary sensing field zones for
several
sensor plates.
[0042] FIG. 34 illustrates a diagrammatic side view of a chassis of a core
apparatus of a surface-conforming obscured feature detector, according to one
embodiment.
[0043] FIG. 35 is a perspective view of the chassis of the core apparatus
of FIG.
34.
[0044] FIG. 36 is a flow diagram of a method of detecting an obscured
feature
behind a surface, according to one embodiment.
[0045] FIG. 37 illustrates two different printed circuit boards in a
stacked
configuration.
[0046] FIG. 38 illustrates a prior art configuration for routing and
shielding the
sensor plate traces from the controller to the sensor plates.
[0047] FIG. 39 is a cross-sectional view of an obscured feature detector,
according to one embodiment, illustrating electric field patterns.
[0048] FIG. 40 is a cross-sectional view of an obscured feature detector,
according to another embodiment, illustrating electric field patterns.
[0049] FIG. 41 is a sensor plate cluster that includes an active shield
center, eight
sensor plates, an active shield plate, and a common plate.
[0050] FIG. 42 is a sensor plate cluster that includes an active shield
center, eight
sensor plates, and an active shield plate.
[0051] FIG. 43 is a side view of an obscured feature detector, according to
one
embodiment, that is placed on a surface and that includes a sensor plate
cluster
similar to that shown in FIG. 42.
[0052] FIG. 44 is a sensor plate cluster that includes eleven sensor
plates, an
active shield plate, and a common plate, and the end sensor plates have less
surface area than the sensor plates that are not at the ends.
[0053] FIG. 45 is a side view of an obscured feature detector, according to
one
embodiment, that is placed on a surface and that includes a sensor plate
cluster
similar to that shown in FIG. 44.
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[0054] FIG. 46 is a side view of an obscured feature detector, according to
another embodiment, that is placed on a surface.
[055] FIG. 47 is a plate configuration for an obscured feature detector,
according
an embodiment of the present disclosure.
[056] FIG. 48 is a plate configuration for an obscured feature detector,
according
to an embodiment of the present disclosure.
[0057] FIG. 49 is a plate configuration for an obscured feature detector,
according
to an embodiment of the present disclosure.
[0058] In the following description, reference is made to the accompanying
drawings that form a part thereof, and in which is shown by way of
illustration
specific exemplary embodiments in which the invention may be practiced. These
embodiments are described in sufficient detail to enable those skilled in the
art to
practice the technology and embodiments described herein, and it is to be
understood that modifications to the various disclosed embodiments may be
made,
and other embodiments may be utilized, without departing from the spirit and
scope
of the present disclosure. The following detailed description is, therefore,
not to be
taken in a limiting sense.
Detailed Description
[0059] Many presently available stud finders (e.g., obscured feature
detectors)
use capacitance to detect obscured features behind a surface. Capacitance is
an
electrical measure of an object's ability to hold or store charge. A common
form of an
energy storage device is the parallel plate capacitor whose capacitance is
approximated by: C = Er CO A/d, where A is the overlapping area of the
parallel
plates, d is the distance between the plates, Er is the relative static
permittivity (or
dielectric constant of the material between the plates), and CO is a constant.
A
dielectric material is an electrical insulator that can be polarized by
applying an
electric field. When a dielectric is placed in an electric field, the
molecules shift from
their average equilibrium positions causing dielectric polarizations. Because
of
dielectric polarizations, positive charges are shifted toward the negative
edge of the
field, and negative charges shift in the opposite direction.
[0060] The dielectric constant (Er) of air is one, while most solid non-
conductive
materials have a dielectric constant greater than one. Generally, it is the
variations in
the dielectric constants of non-conductive solids that enable conventional
capacitive
sensors to work.
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[0061] When the sensor plates on an obscured feature detector are placed on
a
wall at a location with no support behind the wall, the detector measures the
capacitance of the wall and the air behind it. When placed in a position
having a
support behind the wall, the detector then measures the capacitance of the
wall and
the support, which has a higher dielectric constant than air. As a
consequence, the
detector registers an increase in capacitance which can then be used to
trigger an
indicating system.
[0062] In presently available obscured feature detectors a set of identical
sensor
plates are typically arranged in a linear fashion (see, e.g., FIG. 10). Each
of the
sensor plates performs a sensor reading of the surface. The sensor readings
are
then compared. The sensor plates that have the highest sensor readings are
interpreted to be the locations of obscured features. However, sensor plates
that are
near the ends of the group may not respond to obscured features in the same
manner as the plates that are near the center. This issue may be particularly
evident
when the obscured feature detector is moved from a thinner, or less dense,
surface
to a thicker, or more dense, surface.
[0063] Ideally, each of the sensor plates on a thicker surface would have
similar
sensor readings to each other, because the sensor plates are all on the same
surface, with no obscured features present. However, the sensor readings of
the
sensor plates near the ends may see a larger reading increase than the sensor
plates near the center. The sensor plates that are at the ends are alone in
creating
the electric fields that are beyond the group of sensor plates. As a result,
the sensor
plates near the end may respond with a disproportionately higher reading when
placed on a thicker surface. Accordingly, the controller may have difficulty
determining if the elevated sensor readings are due to the presence of an
obscured
feature, or due to the detector being placed on a thicker surface. This
disclosure
provides a solution.
[0064] In obscured feature detectors with multiple sensor plates it is
desirable for
each sensor plate to have a similar response to the same obscured feature. To
ensure a similar response from each sensor plate, proper geometric shape and
arrangement of the sensor plates can ensure an equivalent response to an
obscured
feature. Improved shielding of sensor plate traces may also improve
performance. In
addition, enhanced electrical coupling of the user to the sensing circuit may
provide
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improved performance. Also, a mechanism to ensure that the sensor plates are
flat
against the surface may improve performance.
[0065] The present disclosure is directed to obscured feature detectors and
methods of detecting obscured feature detectors. In the exemplary embodiments,
an
obscured feature detector comprises a group of sensor plates, a multi-layer
printed
circuit board (PCB), a sensing circuit, a controller, a display circuit, a
power
controller, and/or a housing.
[0066] The disclosed embodiments help maintain uniform or near uniform
electric
field lines generated by the group of sensor plates. Specifically, the
electric field of
two end sensor plates in the group of sensor plates is substantially similar
to the
electric field of the non-end sensor plates. The electric fields produced by
the end
sensor plates and the non-end sensor plates may be oriented transverse
relative to
each other.
[0067] The disclosed embodiments enable more accurate identification of a
location of an obscured feature. The disclosed embodiments can also instantly
and
accurately read through a variety of surfaces with different dielectric
constants. In
addition, the presently disclosed embodiments improve the ability to instantly
and
accurately read through a variety of surface thicknesses.
[0068] The disclosed embodiments also create a detector that is easier to
use.
Many prior art detectors require more steps, and more time and more
proficiency, in
order to recalibrate the unit to different surfaces to determine the locations
of
obscured features. The disclosed embodiments provide more reliable sensor
readings. The sensor readings from the sensor plates self-adjust to the
detected
surface and provide a more reliable reading and have the ability to detect
features
more deeply. The sensor readings have significantly less surface-thickness-
induced
reading error. With this reading error removed, the disclosed embodiments can
detect objects more deeply.
[0069] In some embodiments it may be desirable for each sensor plate to
have a
response that is similar to that of other sensor plates in a set of sensor
plates. For
example, in one embodiment, it may be desirable to have the response from each
sensor plate in a group of sensor plates to be similar to the response from
each
other sensor plates of the group. In some embodiments, a similar response may
mean that if the obscured feature detector were to be placed on or against a
first
surface and the readings were recorded to form a first set of readings, then,
if the
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obscured feature detector were to be placed against a second surface (e.g., a
thicker
surface, a denser surface, etc.) and a second set of readings recorded, then
the
difference between the first set of readings and the second set of readings
may be
similar for each of the respective sensor plates.
[0070] Said otherwise, each of the sensor plates of an embodiment of the
obscured feature detector, when placed against a first surface and remote from
any
support structure, et al., may produce a similar reading. For example the
reading
may be 100. If the obscured feature detector is then placed against another
surface
remote from a support structure, et al., and having a different, e.g.,
density,
thickness, dielectric constant, etc., each sensor plate of the obscured
feature
detector may produce a similar value, such as 150, and the difference of the
values
produced by each respective sensor plate may be 50 such that the difference in
values produced by each sensor plate of the group of sensor plates is
essentially
equal in the absence of an obscured feature (e.g., a support structure, etc.).
Any
variation in the values (or differences of values) produced by the group of
sensor
plates may be attributable, therefore, to a presence of an obscured feature
(e.g., a
support structure, etc.).
[0071] In a typical embodiment, the presence of a support structure, e.g.,
a
framing stud, behind a surface against which the obscured feature detector is
placed
may produce a distinct variance in the reading of each sensor plate which
overlies
the support structure behind the surface. For example, a first sensor plate
detecting
a framing stud behind a surface may produce a reading increase of, e.g., 50.
Each
other sensor plate passing or lying over the framing stud may likewise produce
a
reading increase of similar magnitude. Furthermore, each sensor plate may
produce
a similar degree of variance while the particular sensor plate overlies the
support
structure. Furthermore, supporting structures having different
characteristics, e.g.,
density, thickness, material, etc., may produce distinctive variances, each
such
distinctive variance may be similar for each respective sensor plate. Thus,
the
obscured feature detector may serve to both identify a presence of a support
structure and to distinguish to some degree between support structures having
substantial distinctions. For example, steel provides a much stronger signal
than
wood and in some embodiments it may be possible to distinguish between wood
and
steel.
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[0072] A sensor plate of an embodiment may have a rectangular shape, a
trapezoidal shape, a triangular shape, or a complex-geometry shape (e.g., an
asymmetric shape, an irregular shape), in order to produce a more uniform
sensor
field among a plurality of sensor plates in a sensor plate group. In other
words, the
shape of each sensor plate in a sensor plate group may be formed so as to
produce
a similar signal response in each of the sensor plates in the sensor group.
Asymmetric or irregular shapes of at least some of the sensor plates may make
it
possible to achieve a similar response across each of the sensor plates by
allowing
a better tuning for a more similar response. For example, in an embodiment
wherein
the sensor plate group comprises a plurality of sensor plates arranged
generally in a
row, the sensor plates near the center of the row may be uniformly (or
approximately
uniformly) rectangular while each successively distal sensor plate to either
side of
the central rectangular sensor plates may take a different form so as to
"tune" the
signal field across the collection of sensor plates to be more uniform than
may result
from using exclusively a single geometric form for all of the sensor plates. A
preferred shape of each sensor plate, and a preferred configuration of a
collection of
sensor plates of a sensor plate group may be identified through prototype
testing
according to methods known to persons having ordinary skill in the art,
including
physical prototype testing and computer-based simulation testing.
[0073] For example, the shapes of the sensor plates may be determined by
testing physical prototypes by cutting various sensor plate shapes and testing
them.
To find desired sensor plate shapes, various shapes may be tested in various
conditions, such as with different surface thicknesses and on surfaces with
different
dielectric constants. Then the results of various tests would need to be
compared to
determine the magnitude of variation in sensor plate readings. In some
embodiments the sensor plate design that minimizes the variation in readings
across
various test conditions may be selected. The process of testing physical
prototypes
to determine the ideal sensor plate design may be effective, but may be
unusually
burdensome for some embodiments.
[0074] Simulation testing is another example of a way to determine shapes
of
sensor plates. In some embodiments, the shapes of sensor plates may be
determined by simulating them with software, such as by using finite element
analysis software to simulate static electric fields. Other approaches for
analyzing
fields to determine shapes of plates may include method of moments (MoM)
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approaches, finite difference time domain (FDTD) approaches, etc. Available
software can be used to perform these functions. By way of non-limiting
example,
finite element analysis may be used to find sensor plate shapes that provide
the
most similar response across all of the target conditions.
[0075] In some embodiments, different simulation models can be built that
represent different target conditions. For example it may be beneficial to run
models
with three different surface thicknesses, each with three different dielectric
constants,
which would be a total of nine different models. In this way, nine different
target
conditions can be tested. Each model may be tested individually to determine
the
simulated readings on the sensor plates. Then the results of various
simulation tests
can be compared to determine the magnitude of variation in sensor plate
readings.
In some embodiments the sensor plate design that minimizes the variation in
readings may be selected. It may be possible to test different sensor plate
shapes to
determine designs that minimize variation in sensor plate readings across each
of
the target conditions.
[0076] In some embodiments, one approach to prototyping and/or simulation
testing may be to divide the sensor plates into sections and then simulate
individual
sections independently. Those skilled in the art will appreciate that the
concept of
superposition may be relied upon to combine fields resulting from sections by
adding
the fields together to obtain the total resulting fields.
[0077] Prototyping and/or simulation testing may be used to identify ideal
shapes
(potentially including thicknesses and/or constituency) for sensor plates and
ideal
configurations of sensor plates to produce uniform or near-uniform and
consistent
signal responses when used for the purpose of identified obscured features.
[0078] The present disclosure will now be described more fully with
reference to
the accompanying drawings. This disclosure may, however, be embodied in many
different forms and should not be construed as limited to the embodiments set
forth
herein; rather, these embodiments are provided by way of illustration only so
that this
disclosure will be thorough, and fully convey the full scope to those skilled
in the art.
[0079] FIG. 1 illustrates an obscured feature detector 1, according to one
embodiment, placed on a piece of sheetrock 2 (or similar surface) and
detecting an
obscured feature 3. FIG. 2 is a perspective view of the obscured feature
detector 1 of
FIG. 1. FIG. 3 shows a sensor side of the obscured feature detector 1, which
includes a plurality of sensor plates 5 and a shortened common plate 33.
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[0080] With reference to FIGS. 1-3, generally and collectively, the
obscured
feature detector 1 includes three or more sensor plates 5, a sensing circuit
(see FIG.
4), one or more indicators 6, one or more proximity indicators 39, and a
housing 19
to provide or otherwise accommodate a handle 14, an active shield plate 23,
and a
battery cover 28.
[0081] The three or more sensor plates 5 each can take a sensor reading
that
varies based on a proximity of the sensor plate 5 to one or more surrounding
objects
and on a material property of each of the one or more surrounding objects. The
three
or more sensor plates 5 may collectively create a sensing field. Each
individual
sensor plate 5 of the three or more sensor plates 5 may create a corresponding
primary sensing field zone that may be a geometric three-dimensional volume
within
the sensing field where the individual sensor plate 5 contributes more
strongly to the
sensing field than any other of the three or more sensor plates 5. The three
or more
sensor plates 5 may all create primary sensing field zones that are
geometrically
similar. The sensing circuit may couple to the three or more sensor plates 5
to
measure the sensor readings of the three or more sensor plates 5.
[0082] Each sensor plate 5 forms a first end of a corresponding electric
field. The
electric field is produced or received at the sensor plates 5. An area on the
common
plate 33 may form a second end of the corresponding electric field of each
sensor
plate 5. The common plate 33 has a length extending along one side of each of
the
sensor plates 5. The length of the common plate 33 is less than a collective
linear
dimension of the sensor plates 5. In some embodiments, the common plate 33 is
coupled to a non-changing voltage. In some embodiments the common plate 33 is
coupled to the circuit ground. In some embodiments the common plate 33 is
coupled to an alternating signal.
[0083] In some embodiments each sensor plate 5 may be part of a group 7 or
array of sensor plates 5. Each group 7 may include two or more sensor plates 5
and
may also include an active shield plate 23. The sensor plates 5 and active
shield
plate 23 may be on different planes. Nevertheless, if they are driven
simultaneously,
in some embodiments, they may be part of the same group 7 of sensor plates 5.
Each sensor plate 5 has a geometry that is defined by its shape. Each sensor
plate 5
also has a perimeter. In some embodiments the perimeter may be composed of
multiple segments. In some embodiments each segment of the perimeter is either
an
internal border 10 or an external border 11. In some embodiments, if a sensor
plate
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has a segment of the perimeter that is adjacent to the perimeter of the group
7,
then said segment comprises an external border 11. In some embodiments, if a
sensor plate 5 has a segment of the perimeter that is not adjacent to the
perimeter of
the group 7, then said segment comprises an internal border 10.
[0084] In some embodiments to sense the location of an obscured feature 3,
a
sensor plate 5 may be driven with a current source, and the obscured feature
detector 1 measures the time it takes for the sensor plate 5 to reach a
certain
threshold voltage, thereby achieving a sensor reading. In other embodiments a
charge-share mechanism, or sigma delta converter is used to achieve a sensor
reading. Other sensing circuits may also be employed. In other embodiments a
radio frequency signal is placed on the sensor plates 5 to achieve a sensor
reading.
In each of these embodiments a signal is driven on the sensor plate(s) 5 to be
sensed.
[0085] In some embodiments, only a single sensor plate 5 may be driven at a
time. In these embodiments the single sensor plate 5 may be alone in creating
the
sensing field.
[0086] In some embodiments, the group 7 of sensor plates 5 may all be
driven
with the same signal simultaneously. In these embodiments the group 7 of
sensor
plates 5 may create the sensing field. In some embodiments multiple sensor
plates 5
may be driven simultaneously each with the same signal, although possibly only
a
single sensor plate 5 may be sensed. Advantageously driving multiple sensor
plates
5 simultaneously may create field lines that go deeper into an obscured
surface than
may be possible if only a single sensor plate 5 is driven. Deeper field lines
may make
it possible to sense more deeply. In some embodiments the group 7 of sensor
plates
5 and the active shield plate 23 may all be driven with the same signal
simultaneously, which together would create the sensing field.
[0087] Each sensor plate 5 has a primary sensing field zone. In some
embodiments the primary sensing field zone is a geometric three-dimensional
volume of the sensing field and associated field lines where the individual
sensor
plate 5 is able to sense more strongly than the active shield plate 23 (if
present) or
any other sensor plate 5. In some embodiments it is desirable for each sensor
plate
5 to have similar primary sensing field zones. In some embodiments it is
desirable
for each sensor plate 5 to have primary sensing field zones that are
geometrically
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similar and to have similar sensing fields within their respective primary
sensing field
zones.
[0088] FIG. 3 illustrates thirteen sensor plates 5 arranged linearly to
form a
sensor array 7. Each of the sensor plates 5 is rectangular. Each sensor plate
5 is
configured to take a sensor reading that varies based on the proximity of the
sensor
plate 5 to one or more surrounding objects and on a material property of each
of the
one or more surrounding objects.
[0089] In some embodiments, as shown in FIG. 3, the sensor array 7 may
comprise sensor plates 5 that each have a similar geometry. In some
embodiments
the distance between adjacent sensor plates 5 may be approximately 2.0 mm. As
shown, a shortened common plate 33 extends along the sensor array 7 along one
side of each of the sensor plates 5. The length of the shortened common plate
33 is
less than the collective linear dimension of the sensor array 7. In some
embodiments, the shortened common plate 33 may not extend along a side of one
or both of the end sensor plates.
[0090] In FIG. 3 a sensing field may be created collectively by the sensor
plates
5. In some embodiments an active shield plate 23 may contribute to the sensing
field. In the embodiment of FIG. 3 each of the sensor plates 5 may have
similar
primary sensing field zones. In this embodiment, the shortened common plate 33
causes each sensor plate 5 to have primary sensing zones that are more
geometrically similar as explained in more detail with reference to FIGS. 12,
15, and
16. Likewise, each of the sensor plates 5 may also have similar sensing fields
within
their respective primary sensing field zones. As a result, an obscured feature
detector 1 that is built with a configuration of FIG. 3 may offer improved
performance.
When the obscured feature detector 1 is moved from a thin surface to a thicker
surface the sensor readings for each of the sensor plates 5 may have a similar
increase in value.
[0091] In some embodiments a sawtooth-shape border or perimeter may have
the same effective border as a straight-line border that does not have a
sawtooth. In
some embodiments a border with a very slight curve may have the same effective
border as a straight-line border that does not have a slight curve. In some
embodiments a sensor plate 5 with a slot in it has the same effective geometry
as an
otherwise equivalent sensor plate 5 without a slot. In some embodiments a
sensor
plate 5 with a small hole in it may have the same effective geometry as an
equivalent
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sensor plate 5 without a hole. Many other geometries are possible that may be
effectively equivalent to other substantially equivalent geometries. Many
other
borders are possible that may effectively be equivalent to other substantially
equivalent borders. If a geometry or a border has a property that is
effectively
equivalent to another geometry or border, then the two may be considered to be
similar.
[0092] In some embodiments the group 7 of sensor plates 5 is configured
such
that each sensor plate 5 in the group 7 has the same geometry. In some
embodiments each of the sensor plates 5 in the group 7 is radially
symmetrical.
[0093] The plurality of indicators 6 may be toggled between a deactivated
state
and an activated state to indicate a location of a region of relative high
sensor
reading. Activated indicators 4 can indicate the position of the obscured
feature 3.
Proximity indicators 39 can indicate that the obscured feature detector 1 may
be
near the obscured feature 3.
[0094] In FIGS. 1-3, the indicators 6 are positioned on a layer above the
sensor
plates 5. In some embodiments there may be an active shield plate 23 between
the
sensor plates 5 and the indicators 6 so that the indicators 6 do not interfere
with the
function of the sensor plates 5. In some embodiments it may be desirable to
position
the indicators 6 on a layer above the sensor plates 5.
[0095] In some embodiments, a layer of protective material is mounted to
the
bottom of the obscured feature detector housing, such that there is a layer of
protective material between the surface 2 (e.g., sheetrock) and the obscured
feature
detector 1. In some embodiments, the protective material has the interior
substantially filled such that it is substantially free from cavities. In some
embodiments the protective material is unlike felt, Velcro, cloth, or other
materials
that have an interior with cavities. The layer of protective material may
serve the
purpose of protecting the bottom of the obscured feature detector 1 from
damage
due to knocks, bumps, and wear-and-tear. The protective material could be made
from a solid piece of material, such as plastic or other solid non-conductive
materials. A solid layer of plastic may provide a low friction surface that
would allow
the obscured feature detector 1 to slide across the wall. Although some
embodiments of the obscured feature detector 1 do not require sliding to
operate, a
low friction surface may be useful to some users who may choose to move the
obscured feature detector 1 from position to position by sliding it.
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[0096] The protective layer of plastic may be mounted with a pressure
sensitive
adhesive, glue, or other means. The layer of protective material may be a
complete
layer that covers the entire surface; it may be rectangular strips, round
pieces, or
other layers of plastic with other geometries.
[0097] A protective material that is substantially filled such that it is
substantially
free from cavities may build up less static charge than prior art solutions
and may
advantageously provide for more consistent sensor readings.
[0098] In some embodiments the protective material is UHMW-PE (Ultra-High
Molecular Weight Polyethylene). UHMW-PE has a low coefficient of friction.
UHMW-
PE also absorbs very little moisture which may provide increased immunity from
changes in humidity, and may provide enhanced immunity from changes in
humidity.
[0099] FIG. 4 is a diagram of a circuit of an obscured feature detector 1,
according to one embodiment. The circuit includes a multiplexer 18, a power
controller 20, a display circuit 25, a sensing circuit 27, and a controller
60.
[00100] The power controller 20 may include a power source 22 and an on-off
button 24. The power source 22 can comprise an energy source for powering the
indicators 6 and supplying power to a capacitance-to-digital converter 21, and
the
controller 60. In some embodiments, the power source 22 can comprise a DC
battery supply. The on-off switch 24 can be used to activate the controller 60
and
other components of the obscured feature detector 1. In some embodiments, the
on-
off switch 24 comprises a push-button mechanism that activates components of
the
obscured feature detector 1 for a selected time period. In some embodiments
the
push button activates the components such that the components remain activated
until the button is released. In some embodiments the on-off switch 24
comprises a
capacitive sensor that can sense the presence of a finger or thumb over the
button.
In some embodiments, the on-off switch 24 can comprise a toggle switch or
other
types of buttons or switches.
[00101] The display circuit 25 may include one or more indicators 6 that are
electronically coupled to the controller 60.
[00102] The sensing circuit 27 may include a voltage regulator 26 and the
capacitance-to-digital converter 21. In some embodiments, as shown in FIG. 4,
the
sensing circuit 27 comprises a plurality of sensors, the voltage regulator 26,
and the
capacitance-to-digital converter 21. The voltage regulator 26 may be used to
condition the output of the power controller 20, as desired. In some
embodiments the
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voltage regulator 26 is placed as near as possible to the capacitance-to-
digital
converter 21, which may provide a better power source 22 to the capacitance-to-
digital converter 21. The sensing circuit 27 can be electrically coupled to
the
controller 60. One or more sensor plate traces 35, or electrically conductive
paths on
the PCB, may connect the individual sensor plates 5 to the capacitance-to-
digital
converter 21. The connection of the sensor plates 5 to the capacitance-to-
digital
converter 21 may be made via the multiplexer 18. The multiplexer 18 can
individually
connect the sensor plates 5 to the capacitance-to-digital converter 21.
[00103] In some embodiments the multiplexer 18 may connect a single sensor
plate 5 to the sensing circuit 27. In some embodiments, the multiplexer 18 may
connect more than one adjacent sensor plate 5 to the sensing circuit 27. In
some
embodiments, the multiplexer 18 may connect more than one non-adjacent sensor
plate 5 to the sensing circuit 27. In some embodiments, the multiplexer 18 is
configured so that the sensing circuit 27 measures the capacitance of one
sensor
plate 5. In some embodiments, the multiplexer 18 is configured so that the
sensing
circuit 27 measures the aggregate capacitance of two or more sensor plates 5.
[00104] Each individual sensor plate 5 of a group 7 can be independently
connected to the capacitance-to-digital converter 21 via the multiplexer 18.
In some
embodiments, the group 7 itself is composed of layers of copper on a PCB.
[00105] In some embodiments a two-layer PCB is configured as a sensor plate
board 40 (see FIG. 6). In some embodiments a first layer of the sensor plate
board
40 comprises the sensor plates 5, and a second layer of the sensor plate board
40
comprises a shield. In some embodiments, the shield is composed of a layer of
copper that covers the entire surface of the second layer of the PCB. In some
embodiments the layer of copper is covered with a non-conductive layer of
soldermask. In some embodiments there are holes in the layer of soldermask. In
some embodiments, the holes in the layer of soldermask comprise solder pads
that
are suitable for making solder bonds.
[00106] In some embodiments a four-layer PCB is configured as an
interconnection board that has interconnections suitable for connecting
circuitry
components. In some embodiments the interconnection board is configured with
four
layers of interconnections that are suitable for interconnecting the sensing
circuit 27,
the controller 60, and the display circuit 25. In some embodiments one side of
the
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PCB is configured for mounting components, and a second side of the PCB is
configured with solder pads.
[00107] In some embodiments the sensor plates 5 are arranged on a first PCB.
In
some embodiments the interconnection circuitry is arranged on a second PCB. In
some embodiments the first PCB is bonded to the second PCB.
[00108] In some embodiments there are solder pads on the sensor plate board 40
that are complementary with solder pads on an interconnection board. In some
embodiments the sensor plate board 40 and the interconnection board may be
stacked on top of one another and bonded to each other. In some embodiments
the
bonding agent that bonds the two PCBs together may be solder. In some
embodiments solder paste may be used to bond two PCBs together. In some
embodiments, they may be bonded together with solder and the process to bond
them together may be standard SMT (surface mount technology) processes. The
standard SMT process may include using a stencil to place solder paste in the
desired locations. The SMT process may include placing one PCB on top of
another.
In some embodiments pins may be used to ensure proper alignment of the two
PCBs. In some embodiments the final step of the SMT process may involve
running
the stacked PCBs through a reflow oven.
[00109] In some embodiments the sensor plates 5, shield, and circuitry are
placed
on a single PCB. In some embodiments a six-layer PCB is used. In some
embodiments the bottom layer, which is the sixth layer, of the PCB is
configured with
the sensor plates 5. The fifth layer may be an active shield. The top four
layers may
connect the balance of the circuitry.
[00110] In some embodiments the sensor plates 5, shield, and circuitry are
placed
on a single PCB. In some embodiments a four-layer PCB is used. First and
second
layers of the PCB are configured with interconnection circuitry. In some
embodiments the bottom layer, which is the fourth layer, of the PCB is
configured
with the sensor plates 5. The third layer may be an active shield.
[00111] The PCB can be made from a variety of suitable materials, such as, for
example, FR-4, FR-406, or more advanced materials used in radio frequency
circuits, such as Rogers 4003C. Rogers 4003C, and other radio-frequency-class
PCB substrates, may offer improved performance across a broader temperature
and
humidity range.
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[00112] As used herein, the term "module" can describe any given unit of
functionality that can perform in accordance with one or more embodiments of
the
present invention. For example, a module might by implemented using any form
of
hardware or software, or a combination thereof, such as, for example, one or
more
processors, controllers 60, ASICs, PLAs, logical components, software
routines, or
other mechanisms.
[0113] Different processes of reading a capacitance and converting it to a
digital
value, also known as a capacitance-to-digital conversion, are well-described
in the
prior art. The many different methods are not described here, and the reader
is
referred to the prior art for details about different capacitance-to-digital
converter
methods. Some embodiments use a sigma-delta capacitance-to-digital converter,
such as the one that is built into the Analog Devices AD7747 integrated
circuit. Some
embodiments use a charge-sharing method of capacitance-to-digital conversion.
[0114] In some embodiments the voltage regulator 26 may comprise the
ADP150-2.8 from Analog Devices, or the NCP702 from ON Semiconductor, which
provide very low noise. In some embodiments, the controller 60 may comprise
the
C8051 F317 from Silicon Laboratories, or any of many other microcontrollers.
[0115] Detecting obscured features 3 can require a high degree of accuracy,
and
may require more accuracy than the capacitance-to-digital converter 21 may be
able
to provide, if the native capacitance-to-digital converter 21 sensor readings
are used
alone. Native sensor readings are the raw values read from the capacitance-to-
digital converter 21; they are the digital output of the capacitance-to-
digital converter
21.
[0116] Some embodiments perform native reads multiple times, and combine
the
results of the multiple native reads, to create a reading. Some embodiments
perform
native reads multiple times, and combine the results of the multiple native
reads,
using a different configuration for two or more of the native reads to create
a reading.
Some embodiments perform native reads multiple times, and sum or average the
results of the multiple native reads, to create a reading. In some embodiments
this
improves the signal-to-noise ratio. Each native read may involve reading one
sensor
plate 5. A native read could also involve reading a plurality of sensor plates
5, if
multiple sensor plates 5 are multiplexed to the capacitance-to-digital
converter 21. In
some embodiments multiple native reads are combined to create a reading.
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[0117] Summing or averaging multiple native reads may improve the signal-to-
noise ratio, but may not reduce the effect of non-linearities in the
capacitance-to-
digital converter 21. The ideal capacitance-to-digital converter 21 is
perfectly linear,
which means that its native sensor readings increase in direct proportion to
an
increase in the capacitance being sensed. However, many capacitance-to-digital
converters 21 may not be completely linear, such that a change in the input
capacitance does not result in an exactly proportional increase in the native
reading.
These non-linearities may be small, but when a high degree of accuracy is
desired it
may be desirable to implement methods that reduce the effects of the non-
linearities.
[0118] In some embodiments, the ill effects of the non-linearities may be
mitigated by summing multiple native reads, using a slightly different
configuration
for each of the native reads. Some embodiments perform native reads using two
or
more different configurations.
[0119] For example, the bias current is one parameter that can be altered
to
create different configurations. The bias current could be set to normal, or
normal
+20%, normal +35%, or normal +50%. Different bias currents produce different
native sensor readings, even if all other factors remain constant. Since each
native
reading has a different value, presumably each native reading may be subject
to
different non-linearities. Presumably summing or averaging sensor readings
that are
subject to different non-linearities may cause the non-linearities to
partially cancel
each other out, instead of being summed or multiplied.
[0120] In some embodiments there are two separate and independent
capacitance-to-digital converters 21. In some embodiments each of them may
have
different non-linearities. Using both of the capacitance-to-digital converters
21, using
the first converter for some of the reads and using the second converter for
some of
the reads, may mitigate the effect of any single non-linearity.
[0121] Some embodiments perform native reads on each of the sensor plates 5
using each of twelve different configurations.
[0122] After completing the sensor readings, in some embodiments, two
different
calibration algorithms may be performed: first an individual-plate calibration
that
adjusts for individual sensor plate 5 variations, and second a surface
material
calibration that adjusts the sensor readings so that they are tuned to the
surface
density/thickness. Other embodiments may only use one of the two calibration
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algorithms. Some embodiments may use other calibration algorithms. In some
embodiments the calibration algorithms are performed by a calibration module.
[0123] In some embodiments, individual plate calibration is employed first.
With
individual plate calibration, each sensor plate 5 may have its own individual
calibration value. In some embodiments, after the sensor readings are taken,
an
individual plate calibration value is added to, or subtracted from, each of
the sensor
readings. Other embodiments may use multiplication, division, or other
mathematical
functions to perform the individual plate calibration. In some embodiments,
the
individual plate calibration value is stored in non-volatile memory.
Individual plate
calibration compensates for individual sensor plate 5 irregularities, and is
used to
compensate for these irregularities. In some embodiments it is presumed that
after
performing individual plate calibration that the sensor readings will
presumably have
the same calibrated values, if the sensor plate sensor readings are taken
while the
obscured feature detector 1 is on the surface 2 that is similar to the surface
2 the
obscured feature detector 1 was calibrated on. For example, if sensor readings
are
performed on 1/2" sheetrock 2, without any obscured features 3 present, and
the
individual calibration values were created for 1/2" sheetrock 2, then after
performing
individual plate calibration, it is presumed that all the sensor readings
would be
corrected to a common value. If sensor readings are performed on a thicker
material
(such as 5/8" sheetrock 2), a thinner material (such as 3/8" sheetrock 2) or a
different
material (such as 3/4" plywood) then there may be some error in the values.
Surface
material calibration may help correct this error.
[0124] In some embodiments surface material calibration may be used.
[0125] In some embodiments, after calibrating the sensor plate sensor
readings
the obscured feature detector 1 decides if an obscured feature 3 is present.
In some
embodiments the lowest sensor plate reading is subtracted from the highest
sensor
plate reading. If the difference is greater than a threshold value then a
determination
is made that an obscured feature 3 is present.
[0126] If it is determined that no obscured features 3 are present, then
all of the
indicators 6 may be deactivated. If an obscured feature 3 is present then the
obscured feature detector 1 begins the process of determining the position(s)
and
width(s) of the obscured feature(s) 3.
[0127] In some embodiments pattern matching may be employed to determine
which LEDs to activate. In some embodiments a pattern matching module is used
to
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determine the locations of the obscured features 3. The pattern matching
module
compares the calibrated and scaled sensor readings from the sensor plates 5 to
several predetermined patterns. The pattern matching module determines which
predetermined pattern best matches the sensor readings. Then the set of
indicators
6 that corresponds to the best matching pattern is activated. Additional
details about
pattern matching are discussed in the prior art, such as in U.S. Patent No.
8,884,633. Those details will not be repeated here; instead the reader is
encouraged
to refer to them directly.
[0128] In some embodiments the obscured feature detector 1 comprises a
single
capacitance-to-digital converter 21. In some embodiments the sensor plates 5
may
be individually connected to the capacitance-to-digital converter 21. In some
embodiments the sensor plates 5 may be individually connected to the
capacitance-
to-digital converter 21 via the multiplexer 18. In some embodiments more than
one
sensor plate 5 may be connected to the capacitance-to-digital converter 21 at
a time.
In some embodiments multiple adjacent sensor plates 5 may be electrically
connected to the capacitance-to-digital converter 21. In some embodiments
multiple
non-adjacent sensor plates 5 may be connected to the capacitance-to-digital
converter 21. The use of a multiplexer 18 to connect sensor plates 5 to a
single
capacitance-to-digital converter 21 may improve sensor plate 5 to sensor plate
5
consistency of the sensor readings, because the sensor readings from each of
the
sensor plates 5 may be equally affected by variations to the capacitance-to-
digital
converter 21. Factors that may affect the sensor readings from the capacitance-
to-
digital converter 21 may include, but are not limited to, process variations,
temperature variations, voltage variations, electrical noise, aging, and
others.
[0129] In some embodiments, the sensor plate traces 35 are routed such that
each of the sensor plate traces 35 has substantially equal capacitance,
resistance,
and inductance. In some embodiments it is desirable for each of the sensor
plate
traces 35 to have the same electrical properties, so that each of the sensor
plates 5
will respond equivalently to the same detected object(s).
[0130] In some embodiments each of the sensor plate traces 35 from the
capacitance-to-digital converter 21 to each of the sensor plates 5 has
substantially
the same length. In some embodiments two or more of the sensor plate traces 35
from the capacitance-to-digital converter 21 to the sensor plates 5 have
substantially
the same length. In some embodiments sensor plate traces 35 with substantially
the
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same length may have more equivalent capacitances, inductances, and
resistances.
Equal length sensor plate traces 35 may offer enhanced performance because
they
may improve the uniformity of the sensor readings, such that the sensor plates
5
respond more equivalently to the same detected objects, and may provide more
immunity from environmental conditions, such as temperature and humidity.
[0131] In some embodiments each of the sensor plate traces 35, which
comprises electrically conductive paths, has substantially the same width. In
some
embodiments, both the width and the length of each of the sensor plate traces
35 are
substantially equivalent. In some embodiments the sensor plate traces 35 will
have
more than one segment. For example, a first segment of the traces may route
the
sensor plate traces 35 from a capacitance-to-digital converter 21 to a via.
The via
may take the sensor plate trace 35 to a different layer of the PCB, where
there may
be a second segment of the sensor plate trace 35. In some embodiments all of
the
sensor plate traces 35 will have the same length and width, in each segment,
as the
other traces in that segment. In some embodiments two or more of the sensor
plate
traces 35 will have the same width throughout a first segment. In some
embodiments
two or more of the sensor plate traces 35 will have the same width throughout
a
second segment. In some embodiments two or more of the sensor plate traces 35
will have the same length throughout a first segment. In some embodiments two
or
more of the sensor plate traces 35 will have the same length throughout a
second
segment.
[0132] In some embodiments the sensor plate traces 35 comprise multiple
segments. In some embodiments a segment of a sensor plate trace 35 may be the
wire bonds that are within the package of an integrated circuit that route the
signals
from the piece of silicon to the pins of the integrated circuit package. In
some
embodiments a segment of a sensor plate trace 35 may comprise a layer of
copper
on a first layer of a PCB. In some embodiments a segment of a sensor plate
trace 35
may comprise a layer of copper on a second layer of a PCB.
[0133] In some embodiments the capacitance-to-digital converter 21 will
read the
sum of the capacitance on the sensor plates 5 and the capacitance on the
sensor
plate traces 35. In some embodiments, only detecting the sensor readings on
the
sensor plates 5, and not detecting the sensor plate traces 35, may be
preferable.
However, because the sensor plates 5 and sensor plate traces 35 are
electrically
coupled, a means of ensuring stable and uniform capacitance on the sensor
plate
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traces 35 may be desired. For example, it may be desirable to configure the
sensor
plate traces 35 so that their capacitance is uniform and stable. Consequently,
it may
be preferred for the sensor plate traces 35 to be configured so that the
sensor plate
traces 35 do not change. In some embodiments it may be preferred that the
sensor
plate traces 35 do not change relative to each other, such that any change in
the
capacitance on one sensor plate trace 35 is reflected in each of the sensor
plate
traces 35.
[0134] In some embodiments it may be advantageous to shield the sensor
plate
traces 35. Sensor plate trace shielding may protect the sensor plate traces 35
from
external electromagnetic fields. In some embodiments shielding the sensor
plate
traces 35 may also advantageously provide a more consistent environment for
the
sensor plate traces 35 by helping to ensure that each of the sensor plate
traces 35
has an environment that is similar to each of the other sensor plate traces
35.
[0135] In some embodiments each of the sensor plate traces 35 from the
capacitance-to-digital converter 21 to each of the sensor plates 5 has
substantially
the same surroundings. In some embodiments the sensor plate traces 35 are
routed
sufficiently far apart so that capacitive and inductive coupling between the
sensor
plate traces 35 is minimized, and may improve consistency because each of the
sensor plate traces 35 may have surroundings that are more similar to the
other
sensor plate traces 35. In some embodiments each of the sensor plate traces 35
is
shielded on one or both sides with an active shield trace.
[0136] In some embodiments a user may be electrically coupled to the
sensing
circuit 27. In some embodiments the quality of the sensor readings is
increased
when an electrically conductive point of the sensing circuit 27 is coupled to
the user.
Electrically coupling the user to the sensing circuit 27 may provide a
stationary
voltage level for the sensing circuit 27 and may result in higher quality
sensor
readings that have higher sensitivity. For example, a prior art obscured
feature
detector that drives the sensor plates 5 with a 3.0V may in reality only drive
the
sensor plates 5 with a 3.0V signal relative to ground. However, if the ground
is
floating, then driving the sensor plates 5 with 3.0V could result in a 1.5V
signal on
the sensor plates 5 and a -1.5V signal on the ground. In some embodiments the
quality of the sensor readings is not increased when an electrically
conductive point
of the sensing circuit 27 is coupled to the user.
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[0137] In some embodiments electrically coupling the user to the sensing
circuit
27 may result in higher absolute voltage swings on the sensor plates 5, which
may
be due in part to the sensing circuit 27 being held at a stable level. In some
embodiments electrically coupling the user to the sensing circuit 27 may also
result
in sensor readings that are more consistent.
[0138] In some embodiments the user is electrically coupled to the ground
of the
sensing circuit 27, as shown in FIG. 4. In some embodiments the user is
electrically
coupled to the voltage source of the sensing circuit 27. In some embodiments
the
user is electrically coupled to a different electrically conductive point of
sensing
circuit 27.
[0139] In some embodiments the hand of the user may be electrically coupled
to
the sensing circuit 27 by making direct contact with the sensing circuit 27.
In some
embodiments an electrically conductive material, such as a wire, may
electrically
couple the hand of the user to the sensing circuit 27. In some embodiments the
button, which the user would need to touch to activate the obscured feature
detector
1, may comprise an electrically conductive material which may be electrically
coupled to the sensing circuit 27. In some embodiments the button may comprise
aluminum or another electrically conductive material such as tin-plated steel.
In
some embodiments an aluminum button may be anodized, which may provide
pleasing cosmetics.
[0140] In some embodiments the housing 19 (see FIG. 2) of the obscured
feature
detector 1 may comprise an electrically conductive material, such as an
electrically
conductive plastic. In some embodiments only a portion of the housing 19 may
comprise electrically conductive plastic. The electrically conductive housing,
or a
portion of the electrically conductive housing, may be coupled to an
electrically
conductive point in the sensing circuit 27, thereby coupling the user to the
sensing
circuit 27.
[0141] In some embodiments mixing carbon black with the plastic resin may
provide electrically conductive properties. Many thermoplastics, including
polypropylene and polyethylene, become electrically conductive when a carbon
black is mixed into the plastic resin. In some embodiments the conductivity
increases
as the concentration of carbon black is increased, advantageously making it
possible
to control the conductivity of the plastic. In some embodiments a plastic with
a
conductivity that is less than about 25,000 ohms-cm provides sufficiently high
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conductivity to effectively couple the user to the sensing circuit 27. In some
embodiments a higher degree of conductivity may be desired. In some
embodiments
a lower degree of conductivity may be desired. In some embodiments it is
advantageous for the user to be coupled to the sensing circuit by a path with
less
than about 50 mega-ohms.
[0142] In some prior art obscured feature detectors, a change in the
position of
the hand of the user can cause a change in the sensor readings. This may occur
in
some prior art obscured feature detectors because the hand may form a portion
of
the path between the sensor plates 5 and ground. As a result, a change in hand
position can cause a change in the sensor readings of the sensor plates 5.
Disadvantageously, this may reduce the accuracy of the sensor readings.
[0143] If it were possible for the size and position of the hand of the
user to be
constant, it may be possible to do a calibration adjustment to mathematically
remove
the effect of the hand of the user from the raw sensor readings. However, in
practice
this may not be feasible. In practice the size, shape, and position of hands
of
different users may vary too much to make a calibration adjustment practically
possible.
[0144] To improve performance in light of the aforementioned issues, in
some
embodiments a conductive hand guard may be positioned between the hand of the
user and the sensor plates 5. In some embodiments the hand guard may be
grounded to the sensing circuit 27, as illustrated in FIG. 4.
[0145] FIG. 5 is a diagram of the controller 60, according to one
embodiment. The
controller 60 includes a processor 61, a clock 62, random access memory (RAM)
64,
a non-volatile memory 65, and/or another computer-readable medium. The non-
volatile memory 65 may include a program 66 (e.g., in the form of program code
or
computer-executable instructions for performing operations) and calibration
tables
68. In operation, the controller 60 may receive the program 66 and may
synchronize
the functions of the capacitance-to-digital converter 21 and the display
circuit 25 (see
FIG. 4). The non-volatile memory 65 receives and stores the program 66 as well
as
look-up tables (LUT) and calibration tables 68. The program 66 can include a
number of suitable algorithms, such as, for example, an initialization
algorithm, a
calibration algorithm, a pattern-matching algorithm, a multiplexing algorithm,
a
display management algorithm, an active sensor activation algorithm, and a non-
active sensor management algorithm.
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[0146] FIG. 6 is a cross-sectional view of an obscured feature detector,
according
to one embodiment, including a housing, with light pipes and a button, and a
PCB. In
some embodiments, as shown in FIG. 6, a housing 19 comprises an upper housing,
an on-off switch 24, a handle 14, a plurality of light pipes 8, and a power
supply
compartment. In some embodiments a conforming core may be configured to
flexibly
couple the housing 19 to a sensor plate board 40. In some embodiments the
sensor
plate board 40 is a multi-layered PCB with a top layer 44, a second layer 43,
a third
layer 42, and a bottom layer 41. In some embodiments the sensor plate board 40
is
a multi-layered PCB that couples a capacitance-to-digital converter 21, a
display
circuit 25, and a controller 60, as described above with reference to FIG. 4.
In some
embodiments, the housing 19 comprises plastic. In some embodiments, the
housing
19 comprises ABS plastic. In some embodiments a conductive hand guard 56
shields the user's hand from the sensor plate board 40. In some embodiments
the
hand guard 56 is connected to the ground of a sensing circuit.
[0147] In some embodiments, the handle 14 comprises a gripping surface. In
some embodiments a portion of the gripping surface comprises an elastomer that
makes the handle 14 easier to grip. The handle 14 is preferably positioned so
that
the user's hand does not obscure a view of the indicators 6 when grasping the
handle 14. In some embodiments, the power supply compartment comprises a
cavity
for holding a suitable power supply, such as batteries, and a battery cover
for
accessing the compartment.
[0148] In some embodiments the hand guard 56 may be configured so that
there
are no significant straight-line paths between the sensor plates and the
user's hand.
In some embodiments the housing 19 may be composed of an electrically
conductive material which may comprise the hand guard 56. In some embodiments
the conductive layer of material of the hand guard 56 may be a layer of
conductive
plastic. In some embodiments the conductive layer of material of the hand
guard 56
may be a layer of a different conductive material, such as a conductive paint.
In
some embodiments the conductive layer of material of the hand guard 56 may be
a
sheet of metal that is hidden within the housing 19. In some embodiments the
hand
guard 56 may comprise segments of extruded aluminum that are soldered to the
PCB. In some embodiments the hand guard 56 may comprise tin-plated steel,
which may provide for quick, easy and reliable solder joints. In some
embodiments
an entire layer of a PCB may comprise the hand guard 56, such as the top layer
of
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the PCB (printed circuit board). In some embodiments only a portion of a layer
of a
PCB may comprise the hand guard 56, because in some embodiments it may not be
necessary to for the hand guard 56 to comprise an entire layer. For example, a
ring
around the outside of a PCB may be an effective hand guard 56.
[0149] In some embodiments the hand guard 56 is configured to minimize an
effect of a size and position of the hand. In some embodiments the hand guard
56 is
positioned so that it is near the hand because in some embodiments it may be
most
effective when it is nearest to the hand. In some embodiments the hand guard
56
may be electrically coupled to the ground of a sensing circuit 27 (see FIG.
4). In
some embodiments the hand guard 56 may be coupled to the voltage of the
sensing
circuit 27. In some embodiments a different electrically conductive point of
the
sensing circuit 27 may be electrically coupled to the hand guard 56. In some
embodiments an electrical wire comprises the electrical path between the hand
guard 56 and the sensing circuit 27.
[0150] In prior art obscured feature detectors a set of identical sensor
plates 105
are typically arranged in a linear fashion, such as is shown in FIGS. 7, 8, 9,
and 10.
FIG. 7 is a prior art obscured feature detector 101 placed on a comparatively
thinner
surface 12. FIG. 8 is the prior art obscured feature detector 101 placed on a
comparatively thicker surface 13. FIG. 9 shows a side view of the prior art
obscured
feature detector 101, illustrating primary sensing field zones 15, 16, 17 for
several
sensor plates 105, including sensor plates A, B, C, D, E. FIG. 10 shows an
elevation
view of a bottom surface of the prior art obscured feature detector 101,
illustrating
the primary sensing field zones 15, 16, 17 for sensor plates A, B, C, D, E.
[0151] Referring generally and collectively to FIGS. 7-14, each of the
sensor
plates 105 performs a sensor reading of the surface 2. The sensor readings are
then
compared. The sensor plates 105 that have the highest sensor readings are
interpreted to be the locations of obscured features. However, as shown in
FIGS. 7
and 8, the sensor plates 105 that are near the ends of the group may not
respond to
obscured features in the same manner as the sensor plates 105 that are near
the
center. This issue may be particularly evident when the prior art obscured
feature
detector 101 is moved from the thinner, or less dense, surface 12, to a
thicker, or
more dense, surface 13.
[0152] FIG. 7
shows representative sensor readings of the prior art obscured
feature detector 101 that is placed on the relatively thinner surface 12. The
relatively
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thinner surface 12 could be 0.375-inch-thick sheetrock. FIG. 8 shows
representative
sensor readings of the prior art obscured feature detector 101 that is placed
on a
relatively thicker surface 13. The relatively thicker surface 13 could be
0.625-inch-
thick sheetrock.
[0153] In FIG. 7, the prior art obscured feature detector 101 is placed on
the
relatively thinner surface 12. Each of the sensor plates 105 may have a
calibration
adjustment so that each has a calibrated reading of, for example, 100. If this
same
prior art obscured feature detector 101 is then moved to another surface 13
that is
thicker, or to a surface that has a higher dielectric constant, the sensor
readings
would change. An image of the same prior art obscured feature detector 101 on
the
thicker surface 13 is shown in FIG. 8. Ideally, each of the sensor plates 105
on the
thicker surface 13 would have similar sensor readings to each other, because
they
are all on the same thicker surface 13, with no obscured features present.
However,
it may be observed that the sensor readings of the sensor plates 105 near the
ends
may see a larger reading increase than the sensor plates 105 near the center.
In
FIG. 8, it may be seen that the sensor plates 105 near the center have sensor
readings of 200, but the sensor plates 105 at the ends have sensor readings of
250.
[0154] In the prior art obscured feature detector 101 of FIG. 8, and other
prior art
obscured feature detectors, the sensor plates 105 that are at the ends are
alone in
creating electric fields 9 that extend beyond the edges of the group of sensor
plates
105. As a result, the sensor plates 105 near the end may respond with a
disproportionately higher reading when placed on a thicker surface 13.
Disadvantageously, the controller 60 may have difficulty determining if the
elevated
sensor readings are due to the presence of an obscured feature, or due to the
prior
art obscured feature detector 101 being placed on the thicker surface 13. The
disclosed embodiments may address these and other challenges.
[0155] FIG. 9 illustrates the field lines for the prior art obscured
feature detector
101 of FIGS. 7 and 8. FIG. 9 shows a group of sensor plates 105 and also shows
a
two-dimensional representation of the field lines for each of the sensor
plates 105.
The field lines are shown for illustrative purposes and are a representation
of the
actual sensing field. The field lines drawn are equipotential electric field
lines.
However, this drawing does not limit the scope of the disclosure to this type
of field
alone. Vector electric field lines or magnetic field lines could have been
illustrated in
the drawing and are within the scope of the disclosure. The sensing field may
be an
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electric field, a magnetic field, or an electromagnetic field, which is a
combination of
an electric field and a magnetic field.
[0156] In FIG. 9 there are thirteen sensor plates 105. All of the sensor
plates 105
may be driven with the same signal simultaneously, while one sensor plate 105
at a
time is sensed. Because the sensor plates 105 are driven simultaneously, with
the
same signal, the sensing field is defined by the field created by the group of
sensor
plates 105, as illustrated in FIG. 9. An active shield plane is not
illustrated in the
figure, but an active shield may contribute to the sensing field in some
embodiments.
Five of the sensor plates 105 are labeled A, B, C, D, E. The field lines
emanating
from sensor plate E are primarily parallel to sensor plate E. However, the
field lines
emanating from sensor plate A are not very parallel to sensor plate A. Because
the
field lines do not have similar direction and strength at each point within
the primary
sensing field zone the sensor plates A and E do not have similar sensing
fields
within their primary sensing field zones.
[0157] In contrast, sensor plate D and sensor plate E have similar primary
sensing field zones because the volume of the sensing field where they are
able to
sense effectively and the sensing field within that primary sensing field zone
are
similar. The sensing fields within a primary sensing field zone are similar if
the
direction of the sensing field and strength of the sensing field are similar
at each
point within the primary sensing field zone.
[0158] FIG. 10 illustrates the same concept from a different angle or
perspective.
In FIG. 10 the five sensor plates 105 are again labeled A, B, C, D, E. The
approximate primary sensing field zones for each of the sensor plates 105 are
highlighted. On the two-dimensional drawing of FIG. 10, the primary sensing
field
zone 15 for sensor plate A is indicated by the drawing of the sensing field
lines for
sensor plate A. On the two-dimensional drawing of FIG. 10, the primary sensing
field
zone 16 for sensor plate B is indicated by the drawing of sensing field lines
for
sensor plate B. On the two-dimensional drawing of FIG. 10, the primary sensing
field
zone 17 for sensor plate C is indicated by the drawing of sensing field lines
for
sensor plate C.
[0159] FIGS. 9 and 10 illustrate the primary sensing field zone with a two-
dimensional drawing. However, in reality a three-dimensional primary sensing
field
zone may exist. There may be a three-dimensional zone for each sensor plate
105
that comprises the primary sensing field zone for each given sensor plate 105.
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contrast to the prior art embodiment of FIGS. 9 and 10, in some embodiments of
the
present disclosure the sensor plates 105 may have an equivalent primary
sensing
field zone. Each sensor plate 105 in a group that has an equivalent primary
sensing
field zone may have an equivalent response to change in surfaces. This
disclosure
illustrates some configurations wherein each sensor plate 105 in a group may
have
an equivalent primary sensing field zone. In some embodiments each sensor
plate
105 with a similar primary sensing field zone may have a similar change in
sensor
readings in response to a change in the detected surface.
[0160] FIG. 11 is a flow diagram of a method 200 of detecting an obscured
feature behind a surface, according to one embodiment. A first operation, as
illustrated in the flow diagram in FIG. 11, may be to initialize a detector
202, which
may involve running an initialization algorithm. The detector may be according
to one
of the embodiments described herein. After initialization, the sensor plates
may be
read 204. In some embodiments each of the sensor plates may be read multiple
times, each time using a different configuration. The different configurations
may
comprise different drive currents, different voltage levels, different sensing
thresholds, or other different configuration parameters. Each of these
readings of the
sensor plates may be referred to as native readings. In some embodiments
multiple
native readings may be added together to comprise a reading. In some
embodiments there may be a separate reading for each sensor plate.
[0161] In some embodiments, each of these readings has a calibration 206
adjustment performed that is achieved by adding a predetermined calibration
value
to each reading. In some embodiments, after calibration, the readings for each
of the
sensor plates would be the same if the detector were to be placed on a uniform
surface.
[0162] In some embodiments, the largest sensor plate reading is compared
208
to the lowest sensor plate reading. The difference is then compared 208 to a
threshold value. In some embodiments, if the difference is less than a
predetermined
threshold value, then all of the indicators may be turned off 210, to indicate
that no
stud is present. If the difference is larger than a predetermined threshold
value, then
a determination may be made as to which indicators to activate. In certain
embodiments, the readings may be scaled 212 to a predetermined range, which
may
involve setting the lowest value to a number such as 0 and scaling the largest
reading to a value such as 100. Then all of the intermediate values would be
scaled
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proportionately. The scaled readings may then be compared 214 to predetermined
patterns which are scaled in a similar fashion.
[0163] In some embodiments there may be a set of predetermined patterns.
The
set of predetermined patterns may correspond to different combinations of
hidden
features that the detector may encounter. For example, the set of
predetermined
patterns may correspond to different positions for a single stud. In some
embodiments, the set of predetermined patterns may include positional
combinations
of two studs. A pattern matching algorithm may be employed to determine which
predetermined pattern best matches the reading pattern. The detector may then
activate 216 the indicators that correspond to the best matching predetermined
pattern.
[0164] In other embodiments, after calibrating the sensor plate readings, a
determination is made if an obscured feature is present. The lowest sensor
plate
reading may be subtracted from the highest sensor plate reading. If the
difference is
greater than a threshold value, then a determination is made that an obscured
feature is present. If it is determined that no obscured features are present,
then all
of the indicators may be deactivated. If an obscured feature is present then a
process may begin to determine position(s) and/or width(s) of the obscured
feature(s). In some embodiments, all of the current sensor plate readings may
be
scaled such that the lowest reading is scaled to a predetermined value (such
as 0)
and the maximum reading is scaled to a second predetermined value (such as
100).
All intermediate values may be scaled proportionately. Scaled readings may be
easier to compare to a set of predetermined patterns.
[0165] FIG. 12 is a presently available obscured feature detector 1200
having a
sensor plate group arranged in a typical plate configuration. As shown, the
obscured
feature detector 1200 may comprise three or more sensor plates 1205, a common
plate 1202, and an active shield plate 1223.
[0166] The sensor plates 1205 of the obscured feature detector 1200 are
arranged linearly to form a sensor array 1207. As shown, the sensor plates
1205
may have the same geometry and be evenly spaced. Each sensor plate 1205 has an
internal border extending along at least a portion of an internal border of
one or more
other sensor plates 1205, and an external border disposed at an outer
perimeter of
the sensor array 1207. The linear sensor array includes two end sensor plates
1210,
1212 and at least one non-end sensor plate 1214.
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[0167] Each sensor plate 1205 is configured to take a sensor reading that
varies
based on a proximity of the sensor plate 1205 to one or more surrounding
objects
and on a material property of each of the one or more surrounding objects. To
facilitate the sensor reading, an area of each sensor plate 1205 may form a
first end
of a corresponding electric field.
[0168] The common plate 1202 may form a second end of the corresponding
electric field of each sensor plate 1205. The common plate 1202 has a length
1220
extending along a length 1222 of the sensor array, such that the common plate
1202
extends along one external border of each of the sensor plates 1205. As shown,
the
common plate 1202 extends beyond an entire linear dimension of the sensor
array
1207. Common plates of presently available plate configurations are at least
17 mm
longer than the sensor array, whether due to housing size or shape, shielding
configurations, or other reasons. The electric fields of the end sensor plates
formed
with such longer common plates are non-uniform in comparison to the electric
fields
formed by non-end sensor plates with such longer common plates.
[0169] FIG. 13 is a bottom elevation view of an obscured feature detector
1300
having sensor plate cluster 1301 arranged in an improved plate configuration
with a
shortened common plate 1302. As shown, the obscured feature detector 1300 may
comprise three or more sensor plates 1305, the shortened common plate 1302,
and
an active shield plate 1323.
[0170] The sensor plates 1305 in the embodiment shown are arranged linearly
to
form a sensor array 1307. As shown, the sensor plates 1305 may have the same
geometry and be evenly spaced. In other embodiments, the sensor plates 1305
may
vary in size and/or shape, and may be spaced differently based on the position
of the
sensor plate 1305 in the sensor array 1307. The linear sensor array 1307
includes
two end sensor plates 1310, 1312 and at least one non-end sensor plate 1314.
[0171] Each sensor plate 1305 is configured to take a sensor reading that
varies
based on a proximity of the sensor plate 1305 to one or more surrounding
objects
and on a material property of each of the one or more surrounding objects. To
facilitate the sensor reading, an area of each sensor plate 1305 may form a
first end
of a corresponding electric field.
[0172] The shortened common plate 1302 may form a second end of the
corresponding electric field of each sensor plate. The shortened common plate
1302
has a length 1320 extending along a length 1322 of the sensor array 1307 such
that
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the shortened common plate 1302 extends along the sensor array 1307. In some
embodiments, the shortened common plate 1302 may not extend along one or both
of the end sensor plates 1310, 1312. In some embodiments the length 1320 of
the
shortened common plate 1302 is less than the length of the length of the
sensor
plate cluster 1301. In some embodiments the sensor plate cluster 1301 includes
the
sensor plates 1305. In some embodiments the sensor plate cluster 1301 includes
the sensor plates 1305 and an active shield plate 1323. In some embodiments
the
sensor plate cluster 1301 also includes a common plate 1302 and may also
include
circuitry mounted on the side of the sensor plate cluster 1301 that is
opposite the
sensor plates 1305. In some embodiments the length 1320 of the shortened
common plate 1302 is less than the length of the sensor array 1307. In some
embodiments the length 1320 of the shortened common plate 1302 is less than
the
length of the length of the sensor plate cluster 1301. In some embodiments the
length of the common plate is less than the collective length of the sensor
plates
1305 and the active shield plate 1323. In the embodiment shown, the shortened
common plate 1302 is centered along the sensor array 1307. In some embodiments
the shortened common plate 1302 may be off-centered.
[0173] The active shield plate 1323 is disposed between and separates the
sensor plates 1305 and the shortened common plate 1302. In the embodiment
shown, the active shield plate 1323 surrounds the shortened common plate 1302
along three sides. In other embodiments the active shield plate 1323 may only
run
along the length 1320 of the shortened common plate 1302. However, having the
active shield plate 1323 surround the common plate may decrease the complexity
of
manufacturing.
[0174] In some embodiments, one sensor plate 1305 may be sensed at a time.
In
some embodiments when one sensor plate 1305 is sensed, all of the sensor
plates
1305, including the active shield plate 1323, are driven with the same signal
as the
sensed sensor plate 1305. The sensor array 1307, plus the active shield plate
1323,
when driven together may push the field lines of the corresponding electric
field
deeper into the sensed surface than may be possible if just a single sensor
plate
1305 was driven. In some embodiments this allows field lines from a single
sensor
plate 1305 to penetrate more deeply, and allows a single sensor plate 1305 to
sense
more deeply, than may be possible if a single sensor plate 1305 were driven
alone.
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[0175] FIG. 14 illustrates the electric fields created by the prior art
plate
configuration of the obscured feature detector 1200 of FIG. 12. Each sensor
plate
1205 is configured to provide a primary coupling area 1402, 1412 to form a
first end
of a corresponding electric field 1406, 1408. Further, the common plate 1202
is
configured to provide a corresponding primary coupling area 1404, 1414 to
correspond to a sensor plate 1205 and form a second end of the corresponding
electric field 1406, 1408 of that sensor plate 1205.
[0176] The primary coupling area 1402, 1412 is the area of the sensor plate
1205
where the electric field 1406, 1408 primarily couples. In the illustrated
prior art, the
primary coupling area 1402 of the end sensor plate 1210 is on a line 1420 with
the
corresponding primary coupling area 1404 of the common plate 1202. Similarly,
the
primary coupling area 1404 of the non-end sensor plate 1214 is on a line 1422
with
the corresponding primary coupling area 1414 of the common plate 1202. As
shown,
the line 1420 of the primary coupling area 1402 of the end sensor plate 1210
to the
corresponding primary coupling area 1404 of the common plate 1202 is
approximately parallel with the line 1422 of the corresponding primary
coupling area
1404 of the non-end sensor plate 1214 to the corresponding primary coupling
area
1414 of the common plate 1202.
[0177] As shown, the electric field 1406 formed from the end sensor plate
1210 in
this configuration has a different geometry than the electric field 1408
formed from
the non-end sensor plate 1214. The electric fields generated by surrounding
sensor
plates 1205 affect each other sensor plate 1205. The non-uniform electric
field 1406
is a result of the end sensor plate 1210 not having sensor plates 1205 along
both
sides. The non-uniformity of the electric field 1406 may result in an
inaccurate
detection or a missed detection of obscured features. For example, the
electric field
1406 generated by the end sensor plate 1210 may penetrate more broadly into a
surface than the electric field 1408 generated by the non-end sensor plate
1214.
Because of the different sensing areas, the end sensor plate 1210 may falsely
identify an obscured feature.
[0178] FIG. 15 illustrates the electric fields 1506, 1508 created between
an end
sensor plate 1310 and a non-end sensor plate 1314 in the plate configuration
of the
obscured feature detector 1300 of FIG. 13. Primary coupling areas (e.g., 1502,
1512) may couple the sensor plates 1305 to the shortened common plate 1302.
Each of the sensor plates 1305 is configured to provide a primary coupling
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(e.g., 1502, 1512) to form a first end of a corresponding electric field. The
common
plate 1302 is configured to provide corresponding primary coupling areas
(e.g.,
1504, 1514) that each correspond to a sensor plate 1305 and forms a second end
of
the corresponding electric field of that sensor plate 1305.
[0179] For example, as shown, the end sensor plate 1310 is configured to
provide
the primary coupling area 1502 and the non-end sensor plate 1314 is configured
to
provide the primary coupling area 1512. The common plate 1302 is configured to
provide a corresponding primary coupling area 1504 that corresponds to the
primary
coupling area 1502 of the end sensor plate 1310 and a corresponding primary
coupling area 1514 that corresponds to the primary coupling area 1512 of the
non-
end sensor plate 1314.
[0180] As illustrated, the electric fields 1506, 1508 couple the primary
coupling
areas 1502, 1512 of the sensor plates 1305 to the corresponding primary
coupling
areas 1504, 1524 of the common plate 1302. The primary coupling area 1502 of
the
end sensor plate 1310 is on a first line 1520 with the corresponding primary
coupling
area 1504 of the common plate 1302. Further, the primary coupling area 1512 of
the
non-end sensor plate 1314 is on a second line 1522 with the corresponding
primary
coupling area 1514 of the common plate 1302.
[0181] To achieve similar electric fields, the first line 1520 and the
second line
1522 between the coupling areas of the sensor plates 1305 and the common plate
1302 are non-parallel. The electric fields generated by neighboring sensor
plates
1305 affect each other sensor plate 1305. Because the end sensor plate 1310
only
has one neighboring sensor plate 1305, the electric field 1506 would naturally
travel
a greater distance than the electric field 1508 of the non-end sensor plate
1324. As
shown in FIG. 14, the path of the greater distance may extend beyond the
obscured
feature detector. In contrast, as shown In FIG 15, the shortened common plate
1302
pulls the electric field 1506 into near alignment with the electric field
1508. This may
be because the sizing and placement of the shortened common plate 1302 causes
the electric field 1506 from the end sensor plate 1310 to have more similarity
to the
electric field 1508 to the non-end sensor plate 1314, as compared to prior art
obscured feature detectors.
[0182] In some embodiments the electric field 1506 that corresponds to the
end
sensor plates 1310 has a similar size, shape, direction, and/or geometry as
the
electric field 1508 that corresponds to the non-end sensor plate 1314. In some
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embodiments the electric fields that correspond to each of the sensor plates
1305
have the same size, shape, direction, and/or geometry as each of the other
sensor
plates 1305. In some embodiments, the electric fields that correspond to each
of a
group of sensor plates 1305 have the same size, shape, direction, and/or
geometry.
[0183] In some embodiments similar electric field size, shape, direction,
and/or
geometry results in more consistent readings, because each sensor plate 1305
will
respond more uniformly to a change to surface or to the object(s) being
detected.
The sensor plates 1305 that each respond similarly may be able to better
detect
obscured features that are deeper in a wall, or obscured features that may be
harder
to detect. With similar electric fields the result may be an obscured feature
detector
that can be used on a variety of different surfaces and may perform equally
well on
each of the variety of different surfaces. The result may also be an obscured
feature
detector that can sense more deeply, or more accurately, or both.
[0184] In some embodiments an obscured feature detector may have a common
plate that is less than the collective linear dimension of the three or more
sensor
plates. This configuration may result in forming electric fields that have a
similar size,
shape, and/or geometry. In some embodiments an obscured feature detector may
have a common plate that is less than the collective linear dimension of the
three or
more sensor plates plus 16 millimeters. This configuration of a common plate
less
than a length of the sensor array plus 16 millimeters may result in electric
fields that
have a similar size, shape, direction, and/or geometry. In other words, in
some
embodiments there may be a length that is defined as an array-plus length.
This
array-plus length may be at most 16 millimeters longer than the collective
length of
the sensor array. In some embodiments this array-plus length may be at most
one
and a half times a sensor width longer than the collective length of the
sensor array.
In other words, the length of the common plate may measure longer than the
array
by at most one and a half times a width of a sensor plate (e.g., a width of an
end
sensor plate). An obscured feature detector that has a common plate that is
less
than the array-plus length may be called a shortened common plate. In some
embodiments an obscured feature detector that has a shortened common plate may
have electric fields that each have a more similar size, shape, direction,
and/or
geometry.
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[0185] A result of the increased similarity of the electric fields may be
that the
obscured feature detector can sense more accurately and more deeply into
and/or
through a surface.
[0186] An obscured feature detector with a shortened common plate may have
electric fields that each have a more similar size, shape, direction, and/or
geometry,
as compared to obscured feature detectors with a common plate described in the
prior art. More uniformity in the size, shape, direction, or geometry of the
electric
fields associated with each sensor plate may provide more uniform readings for
each
of the sensor plates. Sensor plates that each have similar electric fields may
each
respond in a more uniform manner to different surface materials and
thicknesses.
For example, one embodiment of an obscured feature detector with a shortened
common plate may be placed on a particular surface, such as a surface of 0.25-
inch-
thick sheetrock. When placed on this surface each of the sensor plates may
each
have the same reading, such as a reading of 100 units, for example. In this
example
if the same obscured feature detector is placed on a different surface, such
as 0.50-
inch-thick sheetrock, each of the readings may change to a different value,
but once
again each of the sensor plate readings may be similar, such as a value of 200
units.
When the readings from each of the sensor plates provide similar readings,
independent of whatever surface the obscured feature detector is placed upon,
any
variation in sensor plate readings may be attributed to the presence of an
obscured
feature. Obscured feature detectors with shortened common plates may maintain
a
greater uniformity in the readings, across different surfaces, than prior art
obscured
feature detectors. Readings that are uniform, independent of the surface, may
make
it possible to sense more accurately and more deeply, identify feature width
more
accurately, and make it possible to sense two objects simultaneously more
precisely.
In some embodiments a shortened common plate may have the advantageous result
of the sensing field for each sensor plate being positioned more precisely in
the
region near the sensor plate. As a result, the obscured feature detector may
sense
more accurately and more deeply.
[0187] In some presently available obscured feature detectors the common
plate
is less than 8.00 millimeters wide. In some embodiments of an improved
obscured
feature detector there may be improved performance if the common plate is more
than 8.00 millimeters wide. Obscured feature detectors that have a common
plate
that is more than 8.00 millimeters wide may have electric fields that each
have a
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more similar size, shape, direction, and/or geometry, as compared to obscured
feature detectors with a common plate described in the prior art.
[0188] As shown in FIG. 15, the obscured feature detector 1300 may have a
primary coupling area 1502 of the end sensor plate 1310 of the sensor array
1307 on
a first line 1520 with the corresponding primary coupling area 1504 of the one
or
more common plates. The obscured feature detector 1300 may also have a primary
coupling area 1512 of the non-end sensor plate 1314 of the sensor array 1307
on a
second line 1522 with a corresponding primary coupling area 1514 of the one or
more common plates. In some embodiments, the first line 1520 and the second
line
1522 are non-parallel. This may result in electric fields that have a more-
similar size,
shape, direction, and geometry.
[0189] In other words, if the origin and termination of the electric field
corresponding to the non-end sensor plate 1314 is on the first line 1520, and
if the
origin and termination of the electric field corresponding to the end sensor
plate 1310
is on the second line 1522, and if the first line 1520 and the second line
1522 are
non-parallel, then the electric fields 1506 corresponding to the end sensor
plates
1310 may be more similar to the electric fields 1508 corresponding to non-end
sensor plates 1314 than would be the case if the first and second lines 1520,
1522
were parallel. The result may be that each of the sensor plates 1305 may have
a
more uniform response to changes in the surface or object being detected. As a
result, the obscured feature detector 1300 may sense more accurately and more
deeply.
[0190] For example, if the presence of an obscured feature causes one of
the
sensor plates 1305 to have a particular reading when an object is placed in
proximity
to the sensor plate 1305, it would be desirable for each of the sensor plates
1305 to
have the same reading when the obscured feature is placed in the same position
relative to the sensor plate 1305. The uniform response just described may
make it
possible to sense more independently of the surface material or thickness. The
result may be that studs are sensed more accurately, independent of the
surface
material or thickness.
[0191] The plate configuration of the embodiment of an obscured feature
detector
1300 of FIG. 15 causes the electric field 1506 formed from an end sensor plate
1310
and the electric field 1508 formed from a non-end sensor plate 1314 to have a
similar size, shape, or orientation. This is in contrast with the electric
fields shown in
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FIG. 14. The uniformity of the electric fields may increase the accuracy of an
obscured feature detector. The increased accuracy may be a result of the
electric
fields of each sensor plate 1305 taking a similar reading (e.g., a reading
covering a
similar depth and width).
[0192] FIG. 16 illustrates the electric fields 1606, 1608 emitted from an
end
sensor plate 1310 and a non-end sensor plate 1314 for a plate configuration of
an
obscured feature detector 1600 with multiple common plates 1601. As shown, the
multiple common plates 1601 may be sized, configured, and aligned to cause the
electric field 1606 formed from an end sensor plate 1310 to have a similar
size,
shape, and/or orientation to the electric field 1608 formed from a non-end
sensor
plate 1314. The multiple common plates 1601 may be arranged linearly to extend
along the length of the sensor array 1307.
[0193] Just as in FIG. 15, a primary coupling area 1602 of the end sensor
plate
1310 of the sensor array 1307 is on a first line 1620 with a corresponding
primary
coupling area 1604 of the multiple common plates 1601. Further, a primary
coupling
area 1612 of a non-end sensor plate 1314 of the sensor array 1307 is on a
second
line 1622 with the corresponding primary coupling area 1614 of the multiple
common
plates 1601. Due to the positioning of the multiple common plates 1601, the
first line
1620 and the second line 1622 are non-parallel causing the electric field 1606
formed from the end sensor plate 1310 to have a similar geometry to the
electric field
1608 formed from the non-end sensor plate 1314. The uniformity of the electric
fields
1606, 1608 may increase the accuracy of the obscured feature detector 1600.
Each
of the multiple common plates 1601 may be independently activated. In some
embodiments the multiple common plates 1601 may be activated by being coupled
to an unchanging voltage level, such as 0 volts, or 3 volts, or any other
unchanging
voltage level. In some embodiments the multiple common plates 1601 may be
activated by being driven with an alternating voltage.
[0194] FIG. 17 is a flow chart illustrating a method 1700 of detecting an
obscured
feature behind a surface. The method may include taking 1702 a sensor reading
between the three or more sensor plates and a shortened common plate of an
obscured feature detector. The three or more sensor plates may be arranged
linearly
in a sensor array. The sensor reading may be of a region of a sensing field
formed
between the three or more sensor plates and a common plate of the obscured
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feature detector. The common plate may be less than a dimension of the sensor
array.
[0195] The method may further include measuring 1704, via a sensing
circuit, the
sensor readings of the three or more sensor plates, and comparing 1706
measurements of sensor readings in different regions of the sensing field. The
measured sensor reading may be a capacitive reading or an electromagnetic
reading. Further, the method may toggle 1708 indicators from a deactivated
state to
an activated state to indicate a location of a region of the sensing field
having a
relatively high sensor reading.
[0196] FIG. 18 illustrates an obscured feature detector 1800, according to
another
embodiment of the present disclosure, with an alternative configuration of a
plurality
of sensor plates 1805. The obscured feature detector 1800 includes an end
sensor
plate 1874 of a sensor array 1807 that has less area than the non-end sensor
plates.
In this embodiment the end sensor plate 1874 is narrower than the non-end
sensor
plate 1875 of the sensor array 1807. Each sensor plate 1805 in the sensor
array
1807 is configured to be electrically coupled to a common plate 1876 via an
electric
field 1881, 1882. Each sensor plate 1805 in the sensor array 1807 is
configured to
provide a primary coupling area 1879, 1880 that may form a first end of the
electric
field 1881, 1882. Further, the common plate 1876 is configured to provide a
corresponding primary coupling area 1885, 1886 to correspond to each of the
end
sensor plates1874 and the non-end sensor plates 1875 and form a second end of
the corresponding electric field 1881, 1882 of each sensor plate 1805.
[0197] The primary coupling area 1879 of the end sensor plate 1874 is on a
first
line 1883 that extends from the primary coupling area 1879 of the end sensor
plate
1874 to the primary coupling area 1885 of the common plate 1876. The primary
coupling area 1880 of a non-end sensor plate 1875 is on a second line 1884
that
reaches from the primary coupling area 1880 of the non-end sensor plate 1875
to
the primary coupling area 1886 of the common plate 1876.
[0198] In the configuration of FIG. 18, the common plate 1876 has a length
1878
that is greater than the length 1888 of the sensor array 1807. In some
embodiments
the length 1878 of the common plate 1876 may be equal (or closely similar) to
the
length of the shielding plate 1877 located between the common plate 1876 and
the
sensor array 1807. The non-end sensor plates 1875 each have a length 1873 and
width 1871 that are identical (or closely similar) to the length and width of
the other
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non-end sensor plates 1875 in the sensor array 1807. The end sensor plates
1874
have lengths 1872 that are equal (or closely similar) to the lengths 1873 of
the non-
end sensor plates 1875, but widths 1870 that are smaller than the widths 1871
of the
non-end sensor plates 1875.
[0199] As can be appreciated, the total area of the end sensor plate 1874
is less
than that of a non-end sensor plate 1875. The smaller sensor area may make the
end sensor plates less responsive to changes in the surface 2, such that the
responsiveness of the end sensor plates more closely matches the
responsiveness
of the non-end sensor plates. In some prior art obscured feature detectors the
end
sensor plates and the non-end sensor plates each have different responses to
changing surfaces 2, or to changing obscured features 3. This is
responsiveness
issue is discussed in the dialog surrounding FIG. 7 and FIG. 8. The end sensor
plate
1879 may have less area may be less responsive to different surfaces and to
different obscured features, as a result it may have a response that is more
similar to
the non-end sensor plates 1875. Further, the electric field 1881 formed
between an
end sensor plate 1874 and the common plate 1876 will be smaller than were the
width 1870 of the end sensor plate 1874 identical (or closely similar) to the
width
1871 of the non-end sensor plates 1875. In other words, the narrower width
1870 of
the end sensor plate 1874 results in a smaller electric field 1881 that is
more similar
in shape (including more similar in depth into the surface of detection) to
the electric
field 1882 between a non-end sensor plate 1875 and the common plate 1876. In
contrast to the electric field 1406 in FIG. 14 that couples a wide end sensor
plate
1210 to the common plate 1202, the electric field 1881 in FIG. 18 between the
coupling areas 1879, 1880 of a narrow end sensor plate 1874 and the common
plate
1876 does not diverge as drastically as an end sensor plate having the same
width
as a non-end sensor plate 1875. The electric fields 1881 between the end
sensor
plates 1874 and the common plate 1876 are more similar to the electric fields
between non-end sensor plates 1875 and the common plate 1876. As noted
previously, the more similar shape of the electric field 1881, 1882 translates
in more
predictable readings of the sensor plates, and thereby more accurate
detections of
obscured features.
[0200] In various embodiments according to the configuration illustrated by
FIG.
18, if the electric fields 1881, 1882 are relatively similar in size, shape,
direction,
and/or geometry between sensor plates 1874, 1875 in a sensor array 1807, the
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sensor plates 1874, 1875 may each respond similarly to an obstruction in the
path of
their electric fields 1881, 1882. Stated another way, greater uniformity of
the end
electric fields 1881 with the non-end electric fields 1882 enables more
consistent
readings, because each of the sensor plates 1805 will respond more uniformly
to a
change to a surface or to the object(s) being detected. Sensor plates 1805
that each
respond similarly may be able to better detect obscured features that are
deeper in a
wall, or obscured features that may be harder to detect. With similar electric
fields
1881, 1882, an obscured feature detector may result that can be used on a
variety of
different surfaces and may perform equally well on each of the variety of
different
surfaces. The obscured feature detector 1800 with uniform end electric fields
1881
and non-end electric fields 1882 can sense more deeply, or more accurately, or
both.
[0201] FIG. 19 illustrates an obscured feature detector 1900, according to
another
embodiment of the present disclosure, that is similar to FIG. 18 and with an
alternative end sensor plate configuration. The end sensor plates 1981 have a
different shape than the other sensor plates. In the obscured feature detector
1900
of FIG. 19, the end sensor plates 1981 have a trapezoidal shape. In some
embodiments, the end sensor plates 1981 of a shape different than other sensor
plates may enable the end sensor plates 1981 to detect obscured features more
similarly to non-end sensor plates.
[0202] The end sensor plates 1981 may have the same length 1985 as the non-
end sensor plates 1982, but the lower width 1984 is wider than the upper width
1988.
In some embodiments, the lower width 1984 of the end sensor plates 1981 may be
equal to the lower width 1986 of the non-end sensor plates 1982, and the upper
width 1988 of the end sensor plates 1981 may be smaller. In some embodiments,
the lower width 1984 of the end sensor plates 1981 may be greater than the
width
1986 of the non-end sensor plates 1982, and the upper width 1988 of the end
sensor
plates 1981 may be equal to the width 1986 of the non-end sensor plates 1982.
In
some embodiments both the upper 1988 and lower widths 1984 may be greater than
the width 1986 of the non-end sensor plates 1982, and the lower width 1984 of
the
end sensor plates 1981 is greater than the upper width 1988 of the end sensor
plates 1981. In some embodiments both the upper 1988 and lower widths 1984 may
be smaller than the width 1986 of the non-end sensor plates 1982, and the
lower
width 1984 of the end sensor plates 1981 is greater than the upper width 1988
of the
end sensor plates 1981.
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[0203] FIG. 20 illustrates an obscured feature detector 2001, according to
one
embodiment, placed on a piece of sheetrock 2002 (or similar surface) and
detecting
an obscured feature 2003. FIG. 21 is a perspective view of the obscured
feature
detector 2001 of FIG. 20. FIG. 22 shows a sensor side of the obscured feature
detector 2001, which includes a plurality of sensor plates 2205.
[0204] With reference to FIGS. 20-22, generally and collectively, the
obscured
feature detector 2001 includes three or more sensor plates 2205, a sensing
circuit
(see FIG. 23), one or more indicators 2006, one or more proximity indicators
2039,
and a housing 2019 to provide or otherwise accommodate a handle 2014, an
active
shield plate 2623 (see FIG. 26), and a battery cover 2028.
[0205] The three or more sensor plates 2205 each can take a sensor reading
that
varies based on a proximity of the sensor plate 2205 to one or more
surrounding
objects and on a material property of each of the one or more surrounding
objects.
The three or more sensor plates 2205 collectively create a sensing field. Each
individual sensor plate 2205 of the three or more sensor plates 2205 creates a
corresponding primary sensing field zone that may be a geometric three-
dimensional
volume within the sensing field where the individual sensor plate 2205
contributes
more strongly to the sensing field than any other of the three or more sensor
plates
2205. The three or more sensor plates 2205 all create primary sensing field
zones
that are geometrically similar. The sensing circuit couples to the three or
more
sensor plates 2205 to measure the sensor readings of the three or more sensor
plates 2205.
[0206] In some embodiments each sensor plate 2205 may be part of a group
2207 of sensor plates 2205. Each group 2207 may include two or more sensor
plates 2205 and may also include an active shield plate 2623. The sensor
plates
2205 and active shield plate 2623 may be on different planes. Nevertheless, if
they
are driven simultaneously, in some embodiments, they may be part of the same
group 2207 of sensor plates 2205. Each sensor plate 2205 has a geometry that
is
defined by its shape. Each sensor plate 2205 also has a perimeter. In some
embodiments the perimeter may be composed of multiple segments. In some
embodiments each segment of the perimeter is either an internal border 2210 or
an
external border 2211. In some embodiments, if a sensor plate 2205 has a
segment
of the perimeter that is adjacent to the perimeter of the group 2207, then
said
segment comprises an external border 2211. In some embodiments, if a sensor
plate
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2205 has a segment of the perimeter that is not adjacent to the perimeter of
the
group 2207, then said segment comprises an internal border 2210.
[0207] In some embodiments to sense the location of an obscured feature
2003,
a sensor plate 2205 may be driven with a current source, and the obscured
feature
detector 2001 measures the time it takes for the sensor plate 2205 to reach a
certain
threshold voltage, thereby achieving a sensor reading. In other embodiments a
charge-share mechanism is used to achieve a sensor reading. In other
embodiments a radio frequency signal is placed on the sensor plates 2205 to
achieve a sensor reading. In each of these embodiments a signal is driven on
the
sensor plate(s) 2205 to be sensed.
[0208] In some embodiments, only a single sensor plate 2205 may be driven
at a
time. In these embodiments the single sensor plate 2205 may be alone in
creating
the sensing field.
[0209] In some embodiments, a group 2207 of sensor plates 2205 may all be
driven with the same signal simultaneously. In these embodiments the group
2207
of sensor plates 2205 may create the sensing field. In some embodiments
multiple
sensor plates 2205 may be driven simultaneously each with the same signal,
although possibly only a single sensor plate 2205 may be sensed.
Advantageously
driving multiple sensor plates 2205 simultaneously may create field lines that
go
deeper into an obscured surface than may be possible if only a single sensor
plate
2205 is driven. Deeper field lines may make it possible to sense more deeply.
In
some embodiments a group 2207 of sensor plates 2205 and an active shield plate
2623 may all be driven with the same signal simultaneously, which together
would
create the sensing field.
[0210] Each sensor plate 2205 has a primary sensing field zone. In some
embodiments the primary sensing field zone is a geometric three-dimensional
volume of the sensing field and associated field lines where the individual
sensor
plate 2205 is able to sense more strongly than the active shield plate 2623
(if
present) or any other sensor plate 2205. In some embodiments it is desirable
for
each sensor plate 2205 to have similar primary sensing field zones. In some
embodiments it is desirable for each sensor plate 2205 to have primary sensing
field
zones that are geometrically similar and to have similar sensing fields within
their
respective primary sensing field zones.
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[0211] FIG. 22 illustrates a group 2207 of eight sensor plates 2205. Each
of the
eight sensor plates 2205 is triangular. Each triangular sensor plate 2205 has
two
segments that each have internal borders 2210. Each sensor plate 2205 also has
one segment that has an external border 2211.
[0212] In some embodiments, as shown in FIG. 22, the group 2207 may comprise
eight triangular sensor plates 2205 that each have a similar geometry. The
group
2207 of sensor plates 2205 may be arranged within a square area, wherein each
side of the square area is approximately 3 inches long. In some embodiments,
each
of the sensor plates 2205 may be in the shape of an isosceles triangle. In
some
embodiments the sensor plates 2205 may be arranged such that the hypotenuse of
two triangular sensor plates 2205 may be adjacent to each other, as shown in
FIG.
22. In some embodiments two sensor plates 2205 with adjacent hypotenuses may
approximate a square and fit within one quadrant of the group 2207 of sensor
plates
2205. In some embodiments there may be two such triangles positioned in each
quadrant such that the entire group 2207 comprises eight sensor plates 2205,
as
shown in FIG. 22. In some embodiments the distance between adjacent sensor
plates 2205 may be approximately 2.0 mm.
[0213] In FIG. 22 a sensing field may be created collectively by the eight
sensor
plates 2205. In some embodiments an active shield plate 2623 may contribute to
the
sensing field. In the embodiment of FIG. 22 each of the sensor plates 2205 may
have similar primary sensing field zones. In this embodiment, the radial
symmetry of
the sensor plates 2205 may provide each sensor plate 2205 with primary sensing
zones that are geometrically similar. Likewise, each of the sensor plates 2205
may
also have similar sensing fields within their respective primary sensing field
zones.
As a result, an obscured feature detector 2001 that is built with a
configuration of
FIG. 22 may offer improved performance. When the obscured feature detector
2001
is moved from a thin surface to a thicker surface the sensor readings for each
of the
sensor plates 2205 may have a similar increase in value.
[0214] In some embodiments a sawtooth-shape border or perimeter may have
the same effective border as a straight-line border that does not have a
sawtooth. In
some embodiments a border with a very slight curve may have the same effective
border as a straight-line border that does not have a slight curve. In some
embodiments a sensor plate 2205 with a slot in it has the same effective
geometry
as an otherwise equivalent sensor plate 2205 without a slot. In some
embodiments
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a sensor plate 2205 with a small hole in it may have the same effective
geometry as
an equivalent sensor plate 2205 without a hole. Many other geometries are
possible
that may be effectively equivalent to other substantially equivalent
geometries. Many
other borders are possible that may effectively be equivalent to other
substantially
equivalent borders. If a geometry or a border has a property that is
effectively
equivalent to another geometry or border, then the two may be considered to be
similar.
[0215] In some embodiments a group 2207 of sensor plates 2205 is configured
such that each sensor plate 2205 in the group 2207 has the same geometry. In
some embodiments each of the sensor plates 2205 in the group 2207 is radially
symmetrical.
[0216] The plurality of indicators 2006 may be toggled between a deactivated
state
and an activated state to indicate a location within the sensing field of a
region of
relative high sensor reading. Activated indicators 2004 can indicate the
position of
the obscured feature 2003. Proximity indicators 2039 can indicate that the
obscured
feature detector 2001 may be near the obscured feature 2003.
[0217] In FIGS. 20-22, the indicators 2006 are positioned on a layer above
the
sensor plates 2205. In some embodiments there may be an active shield plate
2623
between the sensor plates 2205 and the indicators 2006 so that the indicators
2006
do not interfere with the function of the sensor plates 2205. In some
embodiments it
may be desirable to position the indicators 2006 on a layer above the sensor
plates
2205 so that each of the sensor plates 2205 may have a similar distance from
the
sensor plate 2205 to the edge of a corresponding PCB.
[0218] In some embodiments, a layer of protective material is mounted to
the
bottom of the obscured feature detector 2001, such that there is a layer of
protective
material between the surface 2002 and the obscured feature detector 2001. In
some
embodiments, the protective material has the interior substantially filled
such that it is
substantially free from cavities. In some embodiments the protective material
is
unlike felt, Velcro, cloth, or other materials that have an interior with
cavities. The
layer of protective material may serve the purpose of protecting the bottom of
the
obscured feature detector 2001 from damage due to knocks, bumps, and wear-and-
tear. The protective material could be made from a solid piece of material,
such as
plastic or other solid non-conductive materials. A solid layer of plastic may
provide a
low friction surface that would allow the obscured feature detector 2001 to
slide
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across the wall. Although some embodiments of the obscured feature detector
2001
do not require sliding to operate, a low friction surface may be useful to
some users
who may choose to move the obscured feature detector 2001 from position to
position by sliding it.
[0219] The protective layer of plastic may be mounted with a pressure
sensitive
adhesive, glue, or other means. The layer of protective material may be a
complete
layer that covers the entire surface; it may be rectangular strips, round
pieces, or
other layers of plastic with other geometries.
[0220] A protective material that is substantially filled such that it is
substantially
free from cavities may build up less static charge than prior art solutions
and may
advantageously provide for more consistent sensor readings.
[0221] In some embodiments the protective material is UHMW-PE (Ultra-High
Molecular Weight Polyethylene). UHMW-PE has a low coefficient of friction.
UHMW-
PE also absorbs very little moisture which may provide increased immunity from
changes in humidity, and may provide enhanced immunity from changes in
humidity.
[0222] FIG. 23 is a diagram of a circuit of an obscured feature detector
2301,
according to one embodiment. The circuit includes a multiplexer 2318, a power
controller 2320, a display circuit 2325, a sensing circuit 2327, and a
controller 2360.
[0223] The power controller 2320 may include a power source 2322 and an on-
off
button 2324. The power source 2322 can comprise an energy source for powering
the indicators 2306 and supplying power to a capacitance-to-digital converter
2321,
and the controller 2360. In some embodiments, the power source 2322 can
comprise
a DC battery supply. The on-off switch 2324 can be used to activate the
controller
2360 and other components of the obscured feature detector 2001. In some
embodiments, the on-off switch 2324 comprises a push-button mechanism that
activates components of the obscured feature detector 2001 for a selected time
period. In some embodiments the push button activates the components such that
the components remain activated until the button is released. In some
embodiments
the on-off switch 2324 comprises a capacitive sensor that can sense the
presence of
a finger or thumb over the button. In some embodiments, the on-off switch 2324
can
comprise a toggle switch or other types of buttons or switches.
[0224] The display circuit 2325 may include one or more indicators 2306
that are
electronically coupled to the controller 2360.
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[0225] The sensing circuit 2327 may include a voltage regulator 2326 and
the
capacitance-to-digital converter 2321. In some embodiments, as shown in FIG.
23,
the sensing circuit 2327 comprises a plurality of sensors, the voltage
regulator 2326,
and the capacitance-to-digital converter 2321. The voltage regulator 2326 may
be
used to condition the output of the power controller 2320, as desired. In some
embodiments the voltage regulator 2326 is placed as near as possible to the
capacitance-to-digital converter 2321, which may provide a better power source
2322 to the capacitance-to-digital converter 2321. The sensing circuit 2327
can be
electrically coupled to the controller 2360. One or more sensor plate traces
2335, or
electrically conductive paths on the PCB, may connect the individual sensor
plates
2305 to the capacitance-to-digital converter 2321. The connection of the
sensor
plates 2305 to the capacitance-to-digital converter 2321 may be made via the
multiplexer 2318. The multiplexer 2318 can individually connect the sensor
plates
2305 to the capacitance-to-digital converter 2321.
[0226] In some embodiments the multiplexer 2318 may connect a single sensor
plate 2305 to the sensing circuit 2327. In some embodiments, the multiplexer
2318
may connect more than one adjacent sensor plate 2305 to the sensing circuit
2327.
In some embodiments, the multiplexer 2318 may connect more than one non-
adjacent sensor plate 2305 to the sensing circuit 2327. In some embodiments,
the
multiplexer 2318 is configured so that the sensing circuit 2327 measures the
capacitance of one sensor plate 2305. In some embodiments, the multiplexer
2318 is
configured so that the sensing circuit 2327 measures the aggregate capacitance
of
two or more sensor plates 2305.
[0227] Each individual sensor plate 2305 of a group 2307 can be
independently
connected to the capacitance-to-digital converter 2321 via the multiplexer
2318. In
some embodiments, the group 2307 itself comprises layers of copper on a PCB.
[0228] In some embodiments a two-layer PCB is configured as a sensor plate
board 2740 (see FIGS. 27 and 37). In some embodiments a first layer of the
sensor
plate board 2740 comprises the sensor plates 2305, and a second layer of the
sensor plate board 2740 comprises a shield. In some embodiments, the shield
comprises a layer of copper that covers the entire surface of the second layer
of the
PCB. In some embodiments the layer of copper is covered with a non-conductive
layer of soldermask. In some embodiments there are holes in the layer of
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soldermask. In some embodiments, the holes in the layer of soldermask comprise
solder pads that are suitable for making solder bonds.
[0229] In some embodiments a four-layer PCB is configured as an
interconnection board that has interconnections suitable for connecting
circuitry
components. In some embodiments the interconnection board is configured with
four layers of interconnections that are suitable for interconnecting the
sensing circuit
2327, the controller 2360, and the display circuit 2325. In some embodiments
one
side of the PCB is configured for mounting components, and a second side of
the
PCB is configured with solder pads.
[0230] In some embodiments the sensor plates 2305 are arranged on a first
PCB.
In some embodiments the interconnection circuitry is arranged on a second PCB.
In
some embodiments the first PCB is bonded to the second PCB.
[0231] In some embodiments there are solder pads on the sensor plate board
2740 that are complementary with solder pads on an interconnection board. In
some
embodiments the sensor plate board 2740 and the interconnection board 3751 may
be stacked on top of one another and bonded to each other (e.g., FIG. 37). In
some
embodiments the bonding agent that bonds the two PCBs together may be solder.
In some embodiments solder paste may be used to bond two PCBs together. In
some embodiments, they may be bonded together with solder and the process to
bond them together may be standard SMT processes. The standard SMT process
may include using a stencil to place solder paste in the desired locations.
The SMT
process may include placing one PCB on top of another. In some embodiments
pins
may be used to ensure proper alignment of the two PCBs. In some embodiments
the final step of the SMT process may involve running the stacked PCBs through
a
reflow oven (e.g., FIG. 37 illustrates an interconnection board 3751 stacked
on top of
a sensor plate board 2740).
[0232] In some embodiments the sensor plates 2305, shield, and circuitry
are
placed on a single PCB. In some embodiments a six-layer PCB is used. In some
embodiments the bottom layer, which is the sixth layer, of the PCB is
configured with
sensor plates 2305. The fifth layer may be an active shield. The top four
layers may
connect the balance of the circuitry.
[0233] In some embodiments the sensor plates 2305, shield, and circuitry
are
placed on a single PCB. In some embodiments a four-layer PCB is used. First
and
second layers of the PCB are configured with interconnection circuitry. In
some
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embodiments the bottom layer, which is the fourth layer, of the PCB is
configured
with sensor plates 2305. The third layer may be an active shield.
[0234] The PCB can be made from a variety of suitable materials, such as,
for
example, FR-4, FR-406, or more advanced materials used in radio frequency
circuits, such as Rogers 4003C. Rogers 4003C, and other radio-frequency-class
PCB substrates, may offer improved performance across a broader temperature
and
humidity range.
[0235] As used herein, the term "module" can describe any given unit of
functionality that can perform in accordance with one or more embodiments of
the
present invention. For example, a module might by implemented using any form
of
hardware or software, or a combination thereof, such as, for example, one or
more
processors, controllers 2360, ASICs, PLAs, logical components, software
routines,
or other mechanisms.
[0236] Different processes of reading a capacitance and converting it to a
digital
value, also known as a capacitance-to-digital conversion, are well-described
in the
prior art. The many different methods are not described here, and the reader
is
referred to the prior art for details about different capacitance-to-digital
converter
methods. Some embodiments use a sigma-delta capacitance-to-digital converter,
such as the one that is built into the Analog Devices AD7747 integrated
circuit. Some
embodiments use a charge-sharing method of capacitance-to-digital conversion.
[0237] In some embodiments the voltage regulator 2326 may comprise the
ADP150-2.65 from Analog Devices, or the NCP702 from ON Semiconductor, which
provide very low noise. In some embodiments, the controller 2360 may comprise
the
C8051 F317 from Silicon Laboratories, or any of many other microcontrollers.
[0238] Detecting obscured features 2003 can require a high degree of
accuracy,
and may require more accuracy than the capacitance-to-digital converter 2321
may
be able to provide, if the native capacitance-to-digital converter 2321 sensor
readings are used alone. Native sensor readings are the raw values read from
the
capacitance-to-digital converter 2321; they are the digital output of the
capacitance-
to-digital converter 2321.
[0239] Some embodiments perform native reads multiple times, and combine
the
results of the multiple native reads, to create a reading. Some embodiments
perform
native reads multiple times, and combine the results of the multiple native
reads,
using a different configuration for two or more of the native reads to create
a reading.
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Some embodiments perform native reads multiple times, and sum or average the
results of the multiple native reads, to create a reading. In some embodiments
this
improves the signal-to-noise ratio. Each native read may involve reading one
sensor
plate 2305. A native read could also involve reading a plurality of sensor
plates 2305,
if multiple sensor plates 2305 are multiplexed to the capacitance-to-digital
converter
2321. In some embodiments multiple native reads are combined to create a
reading.
[0240] Summing or averaging multiple native reads may improve the signal-to-
noise ratio, but may not reduce the effect of non-linearities in the
capacitance-to-
digital converter 2321. The ideal capacitance-to-digital converter 2321 is
perfectly
linear, which means that its native sensor readings increase in direct
proportion to an
increase in the capacitance being sensed. However, many capacitance-to-digital
converters 2321 may not be completely linear, such that a change in the input
capacitance does not result in an exactly proportional increase in the native
reading.
These non-linearities may be small, but when a high degree of accuracy is
desired it
may be desirable to implement methods that reduce the effects of the non-
linearities.
[0241] In some embodiments, the ill effects of the non-linearities may be
mitigated by summing multiple native reads, using a slightly different
configuration
for each of the native reads. Some embodiments perform native reads using two
or
more different configurations.
[0242] For example, the bias current is one parameter that can be altered
to
create different configurations. The bias current could be set to normal, or
normal
+20%, normal +35%, or normal +50%. Different bias currents produce different
native sensor readings, even if all other factors remain constant. Since each
native
reading has a different value, presumably each native reading may be subject
to
different non-linearities. Presumably summing or averaging sensor readings
that are
subject to different non-linearities may cause the non-linearities to
partially cancel
each other out, instead of being summed or multiplied.
[0243] In some embodiments there are two separate and independent
capacitance-to-digital converters 2321. In some embodiments each of them may
have different non-linearities. Using both of the capacitance-to-digital
converters
2321, using the first converter for some of the reads and using the second
converter
for some of the reads, may mitigate the effect of any single non-linearity.
[0244] Some embodiments perform native reads on each of the sensor plates
2305 using each of twelve different configurations.
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[0245] After completing the sensor readings, in some embodiments, two
different
calibration algorithms may be performed: first an individual-plate calibration
that
adjusts for individual sensor plate 2305 variations, and second a surface
material
calibration that adjusts the sensor readings so that they are tuned to the
surface
density/thickness. Other embodiments may only use one of the two calibration
algorithms. Some embodiments may use other calibration algorithms. In some
embodiments the calibration algorithms are performed by a calibration module.
[0246] In some embodiments, individual plate calibration is employed first.
With
individual plate calibration, each sensor plate 2305 may have its own
individual
calibration value. In some embodiments, after the sensor readings are taken,
an
individual plate calibration value is added to, or subtracted from, each of
the sensor
readings. Other embodiments may use multiplication, division, or other
mathematical
functions to perform the individual plate calibration. In some embodiments,
the
individual plate calibration value is stored in non-volatile memory.
Individual plate
calibration compensates for individual sensor plate 2305 irregularities, and
is used to
compensate for these irregularities. In some embodiments it is presumed that
after
performing individual plate calibration that the sensor readings will
presumably have
the same calibrated values, if the sensor plate sensor readings are taken
while the
obscured feature detector 2301 is on a surface that is similar to the surface
2002 the
obscured feature detector 2001 was calibrated on (see e.g., FIG. 22). For
example, if
sensor readings are performed on 1/2" sheetrock 2002, without any obscured
features 2003 present, and the individual calibration values were created for
1/2"
sheetrock 2002, then after performing individual plate calibration, it is
presumed that
all the sensor readings would be corrected to a common value. If sensor
readings
are performed on a thicker material (such as 5/8" sheetrock 2002), a thinner
material
(such as 3/8" sheetrock 2002), or a different material (such as 3/4" plywood)
then
there may be some error in the values. Surface material calibration may help
correct
this error.
[0247] In some embodiments surface material calibration may be used.
[0248] In some embodiments, after calibrating the sensor plate sensor
readings
the obscured feature detector 2301 decides if an obscured feature 2003 is
present.
In some embodiments the lowest sensor plate reading is subtracted from the
highest
sensor plate reading. If the difference is greater than a threshold value then
a
determination is made that an obscured feature 2003 is present.
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[0249] If it is determined that no obscured features 2003 are present, then
all of
the indicators 2306 may be deactivated. If an obscured feature 2003 is present
then
the obscured feature detector 2301 begins the process of determining the
position(s)
and width(s) of the obscured feature(s) 2003.
[0250] In some embodiments pattern matching may be employed to determine
which LEDs to activate. In some embodiments a pattern matching module is used
to
determine the locations of the obscured features 2003. The pattern matching
module
compares the calibrated and scaled sensor readings from the sensor plates 2305
to
several predetermined patterns. The pattern matching module determines which
predetermined pattern best matches the sensor readings. Then the set of
indicators
2306 that corresponds to the best matching pattern is activated. Additional
details
about pattern matching are discussed in the prior art, such as in U.S. Patent
No.
8,884,633. Those details will not be repeated here; instead the reader is
encouraged to refer to them directly.
[0251] In some embodiments the obscured feature detector 2301 comprises a
single capacitance-to-digital converter 2321. In some embodiments the sensor
plates 2305 may be individually connected to the capacitance-to-digital
converter
2321. In some embodiments the sensor plates 2305 may be individually connected
to the capacitance-to-digital converter 2321 via the multiplexer 2318. In some
embodiments more than one sensor plate 2305 may be connected to the
capacitance-to-digital converter 2321 at a time. In some embodiments multiple
adjacent sensor plates 2305 may be electrically connected to the capacitance-
to-
digital converter 2321. In some embodiments multiple non-adjacent sensor
plates
2305 may be connected to the capacitance-to-digital converter 2321. The use of
the
multiplexer 2318 to connect sensor plates 2305 to a single capacitance-to-
digital
converter 2321 may improve sensor plate 2305 to sensor plate 2305 consistency
of
the sensor readings, because the sensor readings from each of the sensor
plates
2305 may be equally affected by variations to the capacitance-to-digital
converter
2321. Factors that may affect the sensor readings from the capacitance-to-
digital
converter 2321 may include, but are not limited to, process variations,
temperature
variations, voltage variations, electrical noise, aging, and others.
[0252] In some embodiments, the sensor plate traces 2335 are routed such
that
each of the sensor plate traces 2335 has substantially equal capacitance,
resistance,
and inductance. In some embodiments it is desirable for each of the sensor
plate
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traces 2335 to have the same electrical properties, so that each of the sensor
plates
2305 will respond equivalently to the same detected object(s).
[0253] In some embodiments each of the sensor plate traces 2335 from the
capacitance-to-digital converter 2321 to each of the sensor plates 2305 has
substantially the same length (see, e.g., FIG. 25). In some embodiments two or
more of the sensor plate traces 2335 from the capacitance-to-digital converter
2321
to the sensor plates 2305 have substantially the same length. In some
embodiments
sensor plate traces 2335 with substantially the same length may have more
equivalent capacitances, inductances, and resistances. Equal length sensor
plate
traces 2335 may offer enhanced performance because they may improve the
uniformity of the sensor readings, such that the sensor plates 2305 respond
more
equivalently to the same detected objects, and may provide more immunity from
environmental conditions, such as temperature and humidity.
[0254] In some embodiments each of the sensor plate traces 2335, which
comprises electrically conductive paths, has substantially the same width. In
some
embodiments, both the width and the length of each of the sensor plate traces
2335
are substantially equivalent. In some embodiments the sensor plate traces 2335
will
have more than one segment. For example, a first segment of the traces may
route
the sensor plate traces 2335 from a capacitance-to-digital converter 2321 to a
via.
The via may take the sensor plate trace 2335 to a different layer of the PCB,
where
there may be a second segment of the sensor plate trace 2335. In some
embodiments all of the sensor plate traces 2335 will have the same length and
width, in each segment, as the other traces in that segment. In some
embodiments
two or more of the sensor plate traces 2335 will have the same width
throughout a
first segment. In some embodiments two or more of the sensor plate traces 2335
will
have the same width throughout a second segment. In some embodiments two or
more of the sensor plate traces 2335 will have the same length throughout a
first
segment. In some embodiments two or more of the sensor plate traces 2335 will
have the same length throughout a second segment.
[0255] In some embodiments the sensor plate traces 2335 comprise multiple
segments. In some embodiments a segment of a sensor plate trace 2335 may be
the
wire bonds that are within the package of an integrated circuit that route the
signals
from the piece of silicon to the pins of the integrated circuit package. In
some
embodiments a segment of a sensor plate trace 2335 may comprise a layer of
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copper on a first layer of a PCB. In some embodiments a segment of a sensor
plate
trace 2335 may comprise a layer of copper on a second layer of a PCB.
[0256] In some embodiments the capacitance-to-digital converter 2321 will
read
the sum of the capacitance on the sensor plates 2305 and the capacitance on
the
sensor plate traces 2335. In some embodiments, only detecting the sensor
readings
on the sensor plates 2305, and not detecting the sensor plate traces 2335, may
be
preferable. However, because the sensor plates 2305 and sensor plate traces
2335
are electrically coupled, a means of ensuring stable and uniform capacitance
on the
sensor plate traces 2335 may be desired. For example, it may be desirable to
configure the sensor plate traces 2335 so that their capacitance is uniform
and
stable. Consequently, it may be preferred for the sensor plate traces 2335 to
be
configured so that the sensor plate traces 2335 do not change. In some
embodiments it may be preferred that the sensor plate traces 2335 do not
change
relative to each other, such that any change in the capacitance on one sensor
plate
trace 2335 is reflected in each of the sensor plate traces 2335.
[0257] In some embodiments it may be advantageous to shield the sensor
plate
traces 2335. Sensor plate trace shielding may protect the sensor plate traces
2335
from external electromagnetic fields. In some embodiments shielding the sensor
plate traces 2335 may also advantageously provide a more consistent
environment
for the sensor plate traces 2335 by helping to ensure that each of the sensor
plate
traces 2335 has an environment that is similar to each of the other sensor
plate
traces 2335.
[0258] In some embodiments each of the sensor plate traces 2335 from the
capacitance-to-digital converter 2321 to each of the sensor plates 2305 has
substantially the same surroundings. In some embodiments the sensor plate
traces
2335 are routed sufficiently far apart so that capacitive and inductive
coupling
between the sensor plate traces 2335 is minimized, and may improve consistency
because each of the sensor plate traces 2335 may have surroundings that are
more
similar to the other sensor plate traces 2335. In some embodiments each of the
sensor plate traces 2335 is shielded on one or both sides with an active
shield trace
(see, e.g., FIG. 25).
[0259] In some embodiments a user 2329 may be electrically coupled to the
sensing circuit 2327. In some embodiments the quality of the sensor readings
is
increased when an electrically conductive point of the sensing circuit 2327 is
coupled
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to the user 2329. Electrically coupling the user 2329 to the sensing circuit
2327 may
provide a stationary voltage level for the sensing circuit 2327 and may result
in
higher quality sensor readings that have higher sensitivity. For example, a
prior art
obscured feature detector that drives the sensor plates 2305 with a 3.0V may
in
reality only drive the sensor plates 2305 with a 3.0V signal relative to
ground.
However, if the ground is floating, then driving the sensor plates 2305 with
3.0V
could result in a 1.5V signal on the sensor plates 2305 and a -1.5V signal on
the
ground.
[0260] In some embodiments electrically coupling the user 2329 to the
sensing
circuit 2327 may result in higher absolute voltage swings on the sensor plates
2305,
which may be due in part to the sensing circuit 2327 being held at a stable
level. In
some embodiments electrically coupling the user 2329 to the sensing circuit
2327
may also result in sensor readings that are more consistent.
[0261] In some embodiments the user 2329 is electrically coupled to the
ground
of the sensing circuit 2327, as shown in FIG. 23. In some embodiments the user
2329 is electrically coupled to the voltage source of the sensing circuit
2327. In some
embodiments the user 2329 is electrically coupled to a different electrically
conductive point of sensing circuit 2327.
[0262] In some embodiments the hand of the user 2329 may be electrically
coupled to the sensing circuit 2327 by making direct contact with the sensing
circuit
2327. In some embodiments an electrically conductive material, such as a wire,
may
electrically couple the hand of the user 2329 to the sensing circuit 2327. In
some
embodiments the button, which the user 2329 would need to touch to activate
the
obscured feature detector 2301, may comprise an electrically conductive
material
which may be electrically coupled to the sensing circuit 2327. In some
embodiments
the button may comprise aluminum or another electrically conductive material
such
as tin-plated steel. In some embodiments an aluminum button may be anodized,
which may provide pleasing cosmetics.
[0263] In some embodiments the housing 2019 (see FIG. 21) of the obscured
feature detector 2301 may comprise an electrically conductive material, such
as an
electrically conductive plastic. In some embodiments only a portion of the
housing
2019 may comprise electrically conductive plastic. The electrically conductive
housing, or a portion of the electrically conductive housing, may be coupled
to an
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electrically conductive point in the sensing circuit 2327, thereby coupling
the user
2329 to the sensing circuit 2327.
[0264] In some embodiments mixing carbon black with the plastic resin may
provide electrically conductive properties. Many thermoplastics, including
polypropylene and polyethylene, become electrically conductive when a carbon
black is mixed into the plastic resin. In some embodiments the conductivity
increases as the concentration of carbon black is increased, advantageously
making
it possible to control the conductivity of the plastic. In some embodiments a
plastic
with a conductivity that is less than about 25,000 ohms-cm provides
sufficiently high
conductivity to effectively couple the user 2329 to the sensing circuit 2327.
In some
embodiments a higher degree of conductivity may be desired. In some
embodiments a lower degree of conductivity may be desired. In some embodiments
it is advantageous for the user 2329 to be coupled to the sensing circuit by a
path
with less than about 50 mega-ohms.
[0265] In some prior art obscured feature detectors, a change in the
position of
the hand of the user 2329 can cause a change in the sensor readings. This may
occur in some prior art obscured feature detectors because the hand may form a
portion of the path between the sensor plates 2305 and ground. As a result, a
change in hand position can cause a change in the sensor readings of the
sensor
plates 2305. Disadvantageously, this may reduce the accuracy of the sensor
readings.
[0266] If it were possible for the size and position of the hand of the
user 2329 to
be constant, it may be possible to do a calibration adjustment to
mathematically
remove the effect of the hand of the user 2329 from the raw sensor readings.
However, in practice this may not be feasible. In practice the size, shape,
and
position of hands of different users 2329 may vary too much to make a
calibration
adjustment practically possible.
[0267] To improve performance in light of the aforementioned issues, in
some
embodiments a conductive hand guard may be positioned between the hand of the
user 2329 and the sensor plates 2305. In some embodiments the hand guard may
be grounded to the sensing circuit 2327, as illustrated in FIG. 23.
[0268] FIG. 24 is a diagram of the controller 2360, according to one
embodiment.
The controller 2360 includes a processor 2461, a clock 2462, random access
memory (RAM) 2464, a non-volatile memory 2465, and/or another computer-
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readable medium. The non-volatile memory 2465 may include a program 2466
(e.g.,
in the form of program code or computer-executable instructions for performing
operations) and calibration tables 2468. In operation, the controller 2360 may
receive the program 2466 and may synchronize the functions of the capacitance-
to-
digital converter 2321 and the display circuit 2325 (see FIG. 23). The non-
volatile
memory 2465 receives and stores the program 2466 as well as LUT and
calibration
tables 2468. The program 2466 can include a number of suitable algorithms,
such
as, for example, an initialization algorithm, a calibration algorithm, a
pattern-matching
algorithm, a multiplexing algorithm, a display management algorithm, an active
sensor activation algorithm, and a non-active sensor management algorithm.
[0269] FIG.
25 illustrates a routing of sensor plate traces 2535 of an obscured
feature detector, according to one embodiment. In the illustrated embodiment
of
FIG. 25, each of the sensor plate traces 2535 has substantially similar trace
length
and the sensor plate traces 2535 are surrounded by an active shield trace
2536. In
some embodiments, as shown in FIG. 25, each of the sensor plate traces 2535 is
shielded on one or both sides with the active shield trace 2536. In some
embodiments the active shield trace 2536 is routed at a uniform distance from
the
sensor plate traces 2535 on both sides of each sensor plate trace 2535. In
some
embodiments, the active shield traces 2536 are substantially parallel to the
sensor
plate traces 2535. In some embodiments, the active shield traces 2536 are
positioned such that the active shield traces 2536 shield the sensor plate
traces
2535 from external electromagnetic fields. In some embodiments, the sensor
plate
traces 2535 and active shield traces 2536 are positioned such that the
capacitance
between each sensor plate trace 2535 and each respective active shield trace
2536
is substantially the same for each sensor plate trace 2535 and its respective
active
shield trace 2536. In some embodiments a sensor plate trace 2535 is
accompanied
by two active shield traces 2536, such that one active shield trace 2536 is
positioned
on each side of the sensor plate trace 2535. In some embodiments, a sensor
plate
trace 2535 and an active shield trace 2536 are positioned such that there is a
constant distance between a sensor plate trace 2535 and the respective active
shield trace 2536, along their length. In some embodiments each of the active
shield
traces 2536 is positioned at a uniform distance away from the respective
sensor
plate trace 2535. In some embodiments a segment of each sensor plate trace
2535
and a segment of each active shield trace 2536 comprise copper traces on a
PCB. In
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some embodiments, the sensor plate traces 2535 and active shield traces 2536
are
both located on the same layer of a PCB. In some embodiments, the active
shield
traces 2536 are driven at a fixed voltage level. In some embodiments, the
active
shield traces 2536 are driven at a voltage that is similar to the voltage
driven on the
sensor plate traces 2535.
[0270] In some embodiments the active shield traces 2536 may be routed at a
distance of approximately 0.6 mm from each sensor plate trace 2535, along as
much
of the length of the sensor plate trace 2535 as is possible. In some
embodiments the
sensor plate traces 2535 are approximately 0.15 mm wide throughout one segment
of the sensor plate trace 2535.
[0271] In some embodiments a shield is configured such that there is a
shield
layer above each sensor plate trace 2535 and a shield layer below each sensor
plate
trace 2535. A shield layer in some embodiments is a layer of copper on an
adjacent
layer of a PCB. As a result the sensor plate traces 2535 may shield both on a
layer
above the sensor plate traces 2535 and on a layer below the sensor plate
traces
2535, as well as shielding on either side of the sensor plate traces 2535. In
some
embodiments the shielding above the sensor plate trace 2535, below the sensor
plate trace 2535, and on either side of the sensor plate trace 2535 are all
electrically
coupled to each other.
[0272] In some embodiments the shield is an active shield. An active shield
is a
shield that is driven with the same voltage potential as the sensed sensor
plate(s). In
some embodiments the voltage wave that is driven on the sensor plates 2505 and
shield may have a triangular shape. In some embodiments the voltage wave that
is
driven on the sensor plates 2505 and shield may have a sinusoidal shape. In
some
embodiments the voltage that is driven on the sensor plates 2505 and shield
may
have a different wave shape.
[0273] Presently available obscured feature detectors may include sensor
plate
traces to connect a sensing circuit to sensor plates. In some presently
available
obscured feature detectors no shielding is used to shield the sensor plate
traces
from interferences. These detectors may be configured to keep potential
interferences a safe distance away from the sensor plate traces.
[0274] Other presently available obscured feature detectors may have
shielding
which may shield the sensor plate traces for a portion of the length of the
sensor
plate trace. In some presently available obscured feature detectors up to 82%
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sensor plate trace's length may be shielded. An example of a presently
available
obscured feature detector with shielding is shown in FIG. 38. In presently
available
obscured feature detectors with shielding, a trace may be routed such that
there is a
ground plane on a PCB layer that is beneath the sensor plate trace and a via
that
connects the segment of the sensor plate trace that is on the top layer of the
PCB
with a segment of the sensor plate trace that is on a lower layer of the PCB.
For the
segment of the sensor plate trace that is on a lower layer of the PCB, there
is a first
active shield plane on a layer of the PCB above the sensor plate trace and a
second
active shield plane on a PCB layer below sensor plate trace. The first active
shield
plane, the second active shield plane, and the shield traces are all coupled
together
and are all driven as an active shield. The active shielding may comprise up
to 82%
of the length of the sensor plate trace.
[0275] In these presently available obscured feature detectors, the
material that is
between the trace and the ground plane may absorb humidity. The material under
some of the traces may absorb more humidity than the material that is under
other
traces. As a result, exposure to humidity may cause the relative sensor
readings of
the sensor plate traces to change. In other words, when exposed to humidity
some
of the sensor readings may change more than other sensor plate sensor
readings,
as a result of the humidity. Undesirably, the change is the result of the
humidity
being absorbed between the trace and ground ¨ not as a result of an obscured
feature being present.
[0276] The present disclosure provides improved obscured feature detectors
with
shielding that may shield the sensor plate traces for more than 82% of the
length of
the sensor plate trace.
[0277] FIG. 25 also illustrates an improved method of routing the sensor
plate
traces 2535 that may result in better performance. In FIG. 25 there is a very
short
sensor plate trace 2535 that connects the sensing circuit 2527 to a via 2534.
This
sensor plate trace 2535 may be only one or two millimeters long. It is made as
short
as is practicably possible. The via 2534 connects the segment of the sensor
plate
trace 2535 that is on the top layer of the PCB with a segment of the sensor
plate
trace 2535 that is on a lower layer of the PCB. For the segment of the sensor
plate
trace 2535 that is on a lower layer of the PCB, there is a first active shield
plane
2537 on a layer of the PCB above the sensor plate trace 2535 and a second
active
shield plane 2538 on a PCB layer below sensor plate trace 2535. The first
active
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shield plane 2537, the second active shield plane 2538, and the shield traces
are all
coupled together and are all driven as an active shield.
[0278] When the sensor plate trace 2535 and the active shield trace 2536
are
both driven with the same signal, then they are the same voltage potential,
and the
capacitance between them may become unimportant. As a result, as the PCB
absorbs humidity and the dielectric constant of the PCB changes, these changes
in
the dielectric constant of the PCB may not have an effect upon the sensor
readings.
Changes in the capacitance between the sensor plate trace 2535 and the active
shielding (e.g., the active shield trace 2536) do not affect the sensor
readings. The
result may be that the sensor plate traces 2535 are able to maintain their
calibration
values better, and the obscured feature detector may be able to determine the
locations of the obscured features better.
[0279] FIG. 26 is a diagram of sensor plate configuration of an obscured
feature
detector, according to one embodiment. In this illustrated arrangement each of
the
eleven different sensor plates 2605 have similar primary sensing field zones.
FIG.
26 illustrates a sensor plate group 2607 that includes eleven sensor plates
2605 and
an active shield plate 2623. In this embodiment the group 2607 of eleven
sensor
plates 2605 are on a bottom layer (e.g., a fourth layer) of a PCB. In this
embodiment
the active shield plate 2623 covers the entire third layer of the PCB. In some
embodiments, one sensor plate 2605 may be sensed at a time. In some
embodiments when one sensor plate 2605 is sensed, all of the sensor plates
2605,
including the active shield plate 2623, are driven with the same signal as the
sensed
sensor plate 2605. The group 2607, plus the active shield plate 2623, when
driven
together may push the field lines deeper into the sensed surface than may be
possible if just a single sensor plate 2605 was driven. In some embodiments
this
allows field lines from a single sensor plate 2605 to penetrate more deeply,
and
allows a single sensor plate 2605 to sense more deeply, than may be possible
if a
single sensor plate 2605 were driven alone.
[0280] In the embodiment of FIG. 26, the sensing field may be created by
the
combination of the group 2607 and the active shield plate 2623 when they are
both
driven with the same signal. In this embodiment the similarities in the
configuration
of each of the eleven sensor plates 2605 may provide each sensor plate 2605
with
primary sensing zones that are geometrically similar. Likewise, each of the
sensor
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plates 2605 may also have similar sensing fields within its respective primary
sensing field zones.
[0281] The configuration of the sensor plates 2605 and the active shield
plate
2623 in FIG. 26 helps provide similar primary electric field zones for each of
the
sensor plates 2605. Each of the eleven sensor plates 2605 has a similar
external
border 2611. They also each have a similar area and a similar internal border
2610.
They also each have similar electrical surroundings. Each sensor plate 2605 is
surrounded on either side by either another sensor plate 2605 or the active
shield
plate 2623. Both the active shield plate 2623 and adjacent sensor plates 2605
may
be driven similarly, and as a result they may each provide equivalent
electrical
surroundings. The result may be that each of the eleven sensor plates 2605 in
FIG.
26 has a primary sensing field zone that is geometrically similar.
[0282] The shapes of the eleven the sensor plates 2605 in FIG. 26 are not
identical. Although it may be ideal for the sensor plates 2605 to be
identical, an
adjustment was made to four of the sensor plates 2605 (two sensor plates 2605
at
each end), so that more similar primary sensing field zones may be obtained.
In this
embodiment achieving more equivalent primary sensing field zones may be more
desirable than having identical sensor plate geometries. Nevertheless, all of
the
eleven sensor plates 2605 may have substantially the same area, same external
border 2611, similar internal border 2610 configuration, and similar
electrical
surroundings. This configuration with these similarities may give each sensor
plate
2605 an equivalent primary sensing field zone.
[0283] In some embodiments it may be beneficial to have similar electrical
surroundings that extend beyond the internal borders 2610 of a sensor plate
2605 for
1X to 1.5X the desired sensing depth. For example, if a 1-inch sensing depth
is
desired it may be beneficial to have similar electrical surroundings around
each
sensor plate 2605 for at least 1 inch to 1.5 inches beyond the internal
borders 2610
of each sensor plate 2605.
[0284] FIG. 27 is a cross-sectional view of an obscured feature detector,
according to one embodiment, including a housing 2719, with light pipes 2708
and a
button 2724, and a PCB 2740. In some embodiments, as shown in FIG. 27, a
housing 2719 comprises an upper housing, an on-off switch 2724, a handle 2714,
a
plurality of light pipes 2708, and a power supply compartment. In some
embodiments
a conforming core (see conforming core apparatus 3449 in FIG. 34) may be
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configured to flexibly couple the housing 2719 to a sensor plate board 2740.
In some
embodiments the sensor plate board 2740 is a multi-layered PCB with a top
layer
2744, a second layer 2743, a third layer 2742, and a bottom layer 2741. In
some
embodiments the sensor plate board 2740 is a multi-layered PCB that couples a
capacitance-to-digital converter 2321, a display circuit 2325, and a
controller 2360,
as described above with reference to FIG. 23. In some embodiments, the housing
2719 comprises plastic. In some embodiments, the housing 2719 comprises ABS
plastic. In some embodiments a conductive hand guard 2756 shields the user's
hand from the sensor plate board 2740. In some embodiments the hand guard 2756
is connected to the ground of a sensing circuit.
[0285] In some embodiments, the handle 2714 comprises a gripping surface.
In
some embodiments a portion of the gripping surface comprises an elastomer that
makes the handle 2714 easier to grip. The handle 2714 is preferably positioned
so
that the user's hand does not obscure a view of the indicators 2706 when
grasping
the handle 2714. In some embodiments, the power supply compartment comprises a
cavity for holding a suitable power supply, such as batteries, and a battery
cover for
accessing the compartment.
[0286] In some embodiments the hand guard 2756 may be configured so that
there are no significant straight-line paths between the sensor plates and the
user's
hand. In some embodiments the housing 2719 may be composed of an electrically
conductive material which may comprise the hand guard 2756. In some
embodiments the conductive layer of material of the hand guard 2756 may be a
layer
of conductive plastic. In some embodiments the conductive layer of material of
the
hand guard 2756 may be a layer of a different conductive material, such as a
conductive paint. In some embodiments the conductive layer of material of the
hand
guard 2756 may be a sheet of metal that is hidden within the housing 2719. In
some
embodiments the hand guard 2756 may comprise tin-plated steel, which may
provide for quick, easy and reliable solder joints. In some embodiments an
entire
layer of a PCB may comprise the hand guard 2756. In some embodiments only a
portion of a layer of a PCB may comprise the hand guard 2756, because in some
embodiments it may not be necessary for the hand guard 2756 to comprise an
entire
layer. For example, a ring around the outside of a PCB may be an effective
hand
guard 2756.
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[0287] In some embodiments the hand guard 2756 is configured to minimize an
effect of a size and position of the hand. In some embodiments the hand guard
2756
is positioned so that it is near the hand because in some embodiments it may
be
most effective when it is nearest to the hand. In some embodiments the hand
guard
2756 may be electrically coupled to the ground of a sensing circuit 2327 (see
FIG.
23). In some embodiments the hand guard 2756 may be coupled to the voltage of
the sensing circuit 2327. In some embodiments a different electrically
conductive
point of the sensing circuit 2327 may be electrically coupled to the hand
guard 2756.
In some embodiments an electrical wire comprises the electrical path between
the
hand guard 2756 and the sensing circuit 2327.
[0288] FIG. 28 illustrates a sensor plate group 2801 with four sensor
plates 2805.
In some embodiments, as shown in FIG. 28, the sensor plate group 2801 may
comprise four similar sensor plates 2805. In the embodiment shown in FIG. 28,
each triangular sensor plate 2805 has two sides of a triangle that each form
internal
borders 2810 and one side of the triangle that forms an external border 2811.
The
four sensor plates 2805 in FIG. 28 are each radially symmetrical. From these
four
sensor plates 2805, three different sensing zones may be possible. For
example, if
a vertical stud were disposed at some arbitrary position relative to the
sensor plates
2805, three different readings might appear, each reading relative to one
sensing
zone of the three zones. The first zone might correspond to the sensor plate
on the
left. The second zone might correspond to the top and bottom sensor plates
(e.g. as
can be appreciated, the top and bottom sensor plates would have the same
reading
because they would each sense the same portion of the vertical stud.) The
third
zone might correspond to the right sensor plate. The relative readings for
each of
the three zones could be used to determine the location of the vertical stud.
[0289] FIG. 29 illustrates a sensor plate group 2901 with six sensor plates
2905.
In some embodiments, as shown in FIG. 29, the sensor plate group 2901 may
include six similar sensor plates 2905. In the embodiment shown in FIG. 29,
each
sensor plate 2905 has two straight sides that each form internal borders 2910
and a
straight side that forms an external border 2911. In some embodiments each of
the
sensor plates 2905 have substantially the same area.
[0290] FIGS. 30-32 are views of a prior art obscured feature detector. In
prior art
obscured feature detectors a set of identical sensor plates 3005 are typically
arranged in a linear fashion, such as shown in FIGS. 30, 31, 32, and 33. FIG.
30 is a
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prior art obscured feature detector 3001 placed on a comparatively thinner
surface
3012. FIG. 31 is the prior art obscured feature detector 3001 placed on a
comparatively thicker surface 3113. FIG. 32 shows a side view of the prior art
obscured feature detector 3001, illustrating primary sensing field zones 3215,
3216,
3217 for several sensor plates 3005, including sensor plates A, B, C, D, E.
FIG. 33
shows an elevation view of a bottom surface of the prior art obscured feature
detector 3001, illustrating the primary sensing field zones 3215, 3216, 3217
for
sensor plates A, B, C, D, E.
[0291] Referring generally and collectively to FIGS. 30-33, each of the
sensor
plates 3005 performs a sensor reading of a surface to detect an obscured
feature
behind the surface. The sensor readings are then compared. The sensor plates
3005 that have the highest sensor readings are interpreted to be the locations
of
obscured features. However, as shown in FIGS. 30 and 31, the sensor plates
3005
that are near the ends of the group may not respond to obscured features in
the
same manner as the sensor plates 3005 that are near the center. This issue may
be
particularly evident when the prior art obscured feature detector 3001 is
moved from
the thinner, or less dense, surface 3012 to an thicker, or more dense, surface
3113.
[0292] FIG. 30 shows representative sensor readings of the prior art
obscured
feature detector 3001 that is placed on the relatively thinner surface 3012.
The
relatively thinner surface 3012 could be 0.375-inch-thick sheetrock. FIG. 31
shows
representative sensor readings of the prior art obscured feature detector 3001
that is
placed on a relatively thicker surface 3113. The relatively thicker surface
3113 could
be 0.625-inch-thick sheetrock.
[0293] In FIG. 30, the prior art obscured feature detector 3001 is placed
on the
relatively thinner surface 3012. Each of the sensor plates 3005 may have a
calibration adjustment so that each has a calibrated reading of, for example,
100. If
this same prior art obscured feature detector 3001 is then moved to another
surface
3113 that is thicker, or to a surface that has a higher dielectric constant,
the sensor
readings would change. An image of the same prior art obscured feature
detector
3001 on the thicker surface 3113 is shown in FIG. 31. Ideally, each of the
sensor
plates 3005 on the thicker surface 3113 would have similar sensor readings to
each
other, because they are all on the same thicker surface 3113, with no obscured
features present. However, it may be observed that the sensor readings of the
sensor plates 3005 near the ends may see a larger reading increase than the
sensor
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plates 3005 near the center. In FIG. 31, it may be seen that the sensor plates
3005
near the center have sensor readings of 200, but the sensor plates 3005 at the
ends
have sensor readings of 250.
[0294] In the prior art obscured feature detector 3001 of FIG. 31, and
other prior
art obscured feature detectors, the sensor plates 3005 that are at the ends
are alone
in creating electric fields 3009 that extend beyond the edges of the group of
sensor
plates 3005. As a result, the sensor plates 3005 near the end may respond with
a
disproportionately higher reading when placed on a thicker surface 3113.
Disadvantageously, the controller 2360 may have difficulty determining if the
elevated sensor readings are due to the presence of an obscured feature, or
due to
the prior art obscured feature detector 3001 being placed on the thicker
surface
3113. The disclosed embodiments may address these and other challenges.
[0295] FIG. 32 illustrates the field lines for the prior art obscured
feature detector
3001 of FIGS. 30 and 31. FIG. 32 shows a group of sensor plates 3005 and also
shows a two-dimensional representation of the field lines for each of the
sensor
plates 3005. The field lines are shown for illustrative purposes and are a
representation of the actual sensing field. The field lines drawn are
equipotential
electric field lines. However, this drawing does not limit the scope of the
disclosure
to this type of field alone. Vector electric field lines or magnetic field
lines could have
been illustrated in the drawing and are within the scope of the disclosure.
The
sensing field may be an electric field, a magnetic field, or an
electromagnetic field,
which is a combination of an electric field and a magnetic field.
[0296] In FIG. 32 there are thirteen sensor plates 3005. All of the sensor
plates
3005 may be driven with the same signal simultaneously, while one sensor plate
3005 at a time is sensed. Because the sensor plates 3005 are driven
simultaneously, with the same signal, the sensing field is defined by the
field created
by the group of sensor plates 3005, as illustrated in FIG. 32. An active
shield plane
is not illustrated in the figure, but an active shield may contribute to the
sensing field
in some embodiments. Five of the sensor plates 3005 are labeled A, B, C, D, E.
The field lines emanating from sensor plate E are primarily parallel to sensor
plate E.
However, the field lines emanating from sensor plate A are not very parallel
to
sensor plate A. Because the field lines do not have similar direction and
strength at
each point within the primary sensing field zone the sensor plates A and E do
not
have similar sensing fields within their primary sensing field zones.
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[0297] In contrast, sensor plate D and sensor plate E have similar primary
sensing field zones because the volume of the sensing field where they are
able to
sense effectively and the sensing field within that primary sensing field zone
are
similar. The sensing fields within a primary sensing field zone are similar if
the
direction of the sensing field and strength of the sensing field are similar
at each
point within the primary sensing field zone.
[0298] FIG. 33 illustrates the same concept from a different angle or
perspective.
In FIG. 33 the five sensor plates 3005 are again labeled A, B, C, D, E. The
approximate primary sensing field zones for each of the sensor plates 3005 are
highlighted. On the two-dimensional drawing of FIG. 33, the primary sensing
field
zone 3215 for sensor plate A is indicated by the drawing of the sensing field
lines for
sensor plate A. On the two-dimensional drawing of FIG. 33, the primary sensing
field zone 3216 for sensor plate B is indicated by the drawing of sensing
field lines
for sensor plate B. On the two-dimensional drawing of FIG. 33, the primary
sensing
field zone 3217 for sensor plate C is indicated by the drawing of sensing
field lines
for sensor plate C.
[0299] FIGS. 32 and 33 illustrate the primary sensing field zone with a two-
dimensional drawing. However, in reality a three-dimensional primary sensing
field
zone may exist. There may be a three-dimensional zone for each sensor plate
3005
that comprises the primary sensing field zone for each given sensor plate
3005. In
contrast to the prior art embodiment of FIGS. 32 and 33, in some embodiments
of
the present disclosure the sensor plates 3005 may have an equivalent primary
sensing field zone. Each sensor plate 3005 in a group that has an equivalent
primary
sensing field zone may have an equivalent response to change in surfaces. This
disclosure illustrates some configurations wherein each sensor plate 3005 in a
group
may have an equivalent primary sensing field zone. In some embodiments each
sensor plate 3005 with a similar primary sensing field zone may have a similar
change in sensor readings in response to a change in the detected surface. In
some
embodiments the sensor plates 3005 in a group of sensor plates 3005 are each
radially symmetrical.
[0300] FIG. 34 illustrates a diagrammatic side view of a chassis of a
conforming
core apparatus 3449 of a surface-conforming obscured feature detector,
according
to one embodiment. FIG. 35 is a perspective view of the chassis of the
conforming
core apparatus 3449 of FIG. 34.
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[0301] The present disclosure provides various embodiments of a surface-
conform ing obscured feature detector. Conventional detectors have sensor
plates
2205 that are rigidly connected together, and as a result the size of obscured
feature
detectors typically remains relatively small to function on the curved
surfaces that are
typical of many architectural surfaces. The surface-conforming obscured
feature
detectors disclosed herein conform to the contour of a surface, minimize air
gaps,
and are able to be larger feature detectors that can offer a variety of
performance
improvements. The improvements described in the present disclosure are
applicable
to both conventional detectors that are relatively small and to larger feature
detectors.
[0302] In some embodiments, the obscured feature detector has one or more
flexible PCBs, such as a sensor plate board 2740, that can bend to match the
contour of the surface to be detected. The flexible PCBs comprise a flexible
substrate. Other flexible substrates can also be used that can be made of
wood,
paper, plastic, or other flexible materials. Rigid flex PCBs can also be used.
[0303] The one or more PCBs can be flexibly connected to the housing 2019
using a flexible medium such as foam rubber, springs, gel, hinges, pivot
points, an
encapsulated fluid such as air, or other suitable compressible or flexible
media. In
some embodiments the housing 2019 is able to flex. In some embodiments the
housing 2019 is partially flexible. In some embodiments the housing 2019 has
integrated plastic leaf springs or other types of springs or features that
provide
flexibility. In some embodiments of the obscured feature detector 2001, the
sensor
plates 2205 can be mounted on a PCB that is mounted external to the housing
2019.
In some embodiments the PCB is connected to the housing 2019 via a foam rubber
ring. In some embodiments, the foam rubber ring is about 7 mm thick and is
formed
approximately in the shape of a ring that is about 6 mm wide along the long
side and
about 5 mm thick along the short side, and approximately follows the perimeter
of
the housing 2019. A permanent adhesive, such as a pressure sensitive acrylic
adhesive, can be used to bond the foam rubber ring to the housing 2019 and to
the
PCB.
[0304] In some embodiments, the foam rubber ring is compressible and the
PCB
is flexible, allowing the obscured feature detector 2001 to conform to
curvature and
irregularities of the surface 2002 against which it is placed. A variety of
flexible
and/or compressible materials can be suitable for the flexible medium.
Ethylene
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propylene diene monomer (EPDM) foam rubber that is rated for 25% compression
under about 1.5 pounds per square inch of pressure can be used. Other types of
foam rubber such as polyurethane foam or silicon rubber foam can also be used.
In
some embodiments it is desirable that the flexible medium attached between the
PCB substrate and the housing 2019 not be electrically conductive or partially
conductive, at least not to the extent that it would interfere with operation
of the
obscured feature detector 2001.
[0305] In some embodiments, the conforming core apparatus 3449, such as
shown in FIGS. 34 and 35, can flexibly connect the housing 2019 to the PCB. In
some embodiments the conforming core apparatus 3449 may have two or more
pivots 3452. In some embodiments the pivots 3452 are flexible joints. In some
embodiments the pivots 3452 are ball joints. In some embodiments the pivots
3452
are hinges. In some embodiments the pivots 3452 are living hinges. A living
hinge
is a thin flexible hinge made from the same material as the two rigid pieces
it
connects. In some embodiments the pivots 3452 may be any of many other
flexible
mechanisms.
[0306] In some embodiments the conforming core apparatus 3449 comprises a
main shaft 3453, as illustrated in FIGS. 34 and 36. In some embodiments the
main
shaft 3453 comprises a shaft member. In some embodiments the main shaft 3453
comprises a shaft member and two pivots 3452. In some embodiments each pivot
3452 of the main shaft 3453 couples the main shaft 3453 to a minor shaft 3454.
In
some embodiments each minor shaft 3454 comprises a shaft member and three
pivots 3452. In some embodiments of the minor shaft 3454 there is one pivot
3452
near the center of each minor shaft 3454 and there are two additional pivots
3452,
one at each end of the minor shaft 3454. In some embodiments there are four
feet
3455 coupled to the main shaft 3453. In some embodiments each foot 3455 has a
pivot 3452. In some embodiments the pivots 3452 at each of the ends of the two
minor shafts 3454 are coupled to a pivot 3452 in each of the four feet 3455.
In some
embodiments each foot 3455 is coupled to the PCB. In some embodiments the PCB
can flex to match the contour of the surface 2002.
[0307] In some embodiments the feet 3455 couple the PCB to the minor shaft
3454 as shown in FIGS. 34 and 35.
[0308] In some embodiments the conforming core apparatus 3449 comprises the
main shaft 3453, two minor shafts 3454, and four feet 3455. In some
embodiments
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there are six pivots 3452 in the conforming core apparatus 3449. In some
embodiments there are more than six pivots 3452. In some embodiments there are
less than six pivots 3452.
[0309] In some embodiments, as shown in FIG. 35, all of the pivots 3452 are
living hinges, such that the entire conforming core apparatus 3449 comprises
one
single piece of injection molded plastic.
[0310] FIG. 36 is a flow diagram of a method 3600 of detecting an obscured
feature behind a surface, according to one embodiment. A first operation, as
illustrated in the flow diagram in FIG. 36, may be to initialize 3602 a
detector, which
may involve running an initialization algorithm. The detector may be according
to
one of the embodiments described herein. After initialization, the sensor
plates may
be read 3604. In some embodiments each of the sensor plates may be read
multiple
times, each time using a different configuration. The different configurations
may
comprise different drive currents, different voltage levels, different sensing
thresholds, or other different configuration parameters. Each of these
readings of
the sensor plates may be referred to as native readings. In some embodiments
multiple native readings may be added together to comprise a reading. In some
embodiments there may be a separate reading for each sensor plate.
[0311] In some embodiments, each of these readings has a calibration 3606
adjustment performed that is achieved by adding a predetermined calibration
value
to each reading. In some embodiments, after calibration, the readings for each
of the
sensor plates would be the same if the detector were to be placed on a uniform
surface.
[0312] In some embodiments, the largest sensor plate reading is compared
3608
to the lowest sensor plate reading. The difference is then compared 3608 to a
threshold value. In some embodiments, if the difference is less than a
predetermined threshold value, then all of the indicators may be turned off
3610, to
indicate that no stud is present. If the difference is larger than a
predetermined
threshold value, then a determination may be made as to which indicators to
activate. In certain embodiments, the readings may be scaled 3612 to a
predetermine range, which may involve setting the lowest value to a number
such as
0 and scaling the largest reading to a value such as 100. Then all of the
intermediate values would be scaled proportionately. The scaled readings may
then
be compared 3614 to predetermined patterns which are scaled in a similar
fashion.
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[0313] In some embodiments there may be a set of predetermine patterns. The
set of predetermined patterns may correspond to different combinations of
hidden
features that the detector may encounter. For example, the set of
predetermined
patterns may correspond to different positions for a single stud. In some
embodiments, the set of predetermined patterns may include positional
combinations
of two studs. A pattern matching algorithm may be employed to determine which
predetermined pattern best matches the reading pattern. The detector may then
activate 3616 the indicators that correspond to the best matching
predetermined
pattern.
[0314] In other embodiments, after calibrating the sensor plate readings, a
determination is made if an obscured feature is present. The lowest sensor
plate
reading may be subtracted from the highest sensor plate reading. If the
difference is
greater than a threshold value, then a determination is made that an obscured
feature is present. If it is determined that no obscured features are present,
then all
of the indicators may be deactivated. If an obscured feature is present then a
process may begin to determine position(s) and/or width(s) of the obscured
feature(s). In some embodiments, all of the current sensor plate readings may
be
scaled such that the lowest reading is scaled to a predetermined value (such
as 0)
and the maximum reading is scaled to a second predetermined value (such as
100).
All intermediate values may be scaled proportionately. Scaled readings may be
easier to compare to a set of predetermined patterns.
[0315] FIG. 37 illustrates two different PCBs in a stacked configuration,
according
to one embodiment of the present disclosure. A sensor plate board 3740 and an
interconnection board 3751 may be stacked on top of one another and bonded to
each other. The sensor plate board 3740 may include one or more sensor plates.
The interconnection board 3751 may include the plurality of indicators 3706.
The
sensor plate board 3740 and/or the interconnection board 3751 may be PCBs or
otherwise integrated into a PCB. In some embodiments the bonding agent that
bonds the two PCBs 3740, 3751 together may be solder. In some embodiments
solder paste may be used to bond the two PCBs 3740, 3751 together. In some
embodiments, they may be bonded together with solder and the process to bond
them together may be standard SMT processes. The SMT process may include
placing one PCB on top of another. In some embodiments, pins may be used to
ensure proper alignment of the two PCBs 3740, 3751. In some embodiments the
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final step of the SMT process may involve running the stacked PCBs 3740, 3751
through a reflow oven.
[0316] In other embodiments, both the sensor plates and the circuitry may
be
assembled on a single PCB. A 1.6-mm-thick PCB with four layers of copper can
be
used. In some embodiments the first layer of copper is on the upper surface
and all
of the electrical components are soldered to this layer. The second layer of
copper
can be at a position that is about 0.35 mm below the first layer of copper,
such that
there is about 0.35 mm of PCB substrate between the first and second layers of
copper. The third layer of copper can be at a position that is about 0.1 mm
below the
second layer of copper, such that there is about 0.1 mm of PCB substrate
between
the second and third layers of copper. A fourth layer of copper can be at a
position
that is about 0.35 mm below the third layer of copper, such that there is
about 0.1
mm of PCB substrate between the third and fourth layers of copper. In some
embodiments vias can be drilled to selectively connect the four layers of
copper.
[0317] In some embodiments a final layer of substrate material that is 0.8
mm
thick can be placed to cover the fourth layer of copper. In some embodiments,
no
holes are drilled through the 0.8-mm-thick layer of substrate. The 0.8-mm-
thick layer
of substrate may help protect the circuit from electrostatic discharge.
Alternatively, a
layer of plastic, or other non-conductive material, can be used to shield the
circuit
from electrostatic discharge and to physically protect the PCB. In some
embodiments, a layer of plastic can be used in addition to a protective layer
of circuit
board substrate. It is to be understood that the layers and thicknesses
indicated here
are only exemplary of one embodiment. Other combinations of layers and
thicknesses, and materials, can also be used.
[0318] In some embodiments the sensor plates can be placed on the fourth
layer
of copper. A shield to electrically protect the sensor plates from electrical
interference from ambient conditions, including the user's hand, may be used.
In
some embodiments the shield may be placed on the first layer of copper. In
some
embodiments, a solid shield may cover substantially all of the shield's area,
instead
of using a mesh, stripes, or another pattern that may provide less than
substantially
all of the shield's area.
[0319] In some embodiments the electrically conductive paths that link the
sensor
plates to the capacitance-to-digital converter comprise sensor plate traces.
In some
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embodiments the sensor plate traces are placed primarily on the second layer
of
copper, and shields for the signals are placed on the first and fourth layers
of copper.
[0320] In some embodiments, the interconnection boards 3751 that are
soldered
to the sensor plate board 3740 are covered with a layer of epoxy, a glob of
epoxy, or
another conformal coating which may improve the reliability of solder joints.
In some
embodiments the interconnection boards 3751 on the sensor plate board 3740 are
wire bonded to the PCB with chip-on-board technology. The chip-on-board
technology may involve the steps of (1) attaching bare die to the PCB, (2)
wire
bonding (electrically connecting signals on the bare die to the PCB), and (3)
covering
the bare die and wire bonds with a coating of epoxy or other appropriate
material.
The chip-on-board technology may improve the reliability of solder joints.
[0321] In some embodiments integrated circuits that have packages with
external
leads are used such as QFP packages, TSOP packages, SOIC packages, QSOP
packages, or others. Components that have external leads may improve solder
joint
reliability.
[0322] FIG. 38 illustrates a prior art configuration for routing and
shielding sensor
plate traces 3835 from the controller of a sensing circuit 3827 to sensor
plates 3805.
In this prior art, the sensor plate trace 3835 is routed such that there is a
ground
plane 3833 on a PCB layer that is beneath the sensor plate trace 3835. A via
3834
connects the segment of the sensor plate trace 3835 that is on the top layer
of the
PCB with a segment of the sensor plate trace 3835 that is on a lower layer of
the
PCB. For the segment of the sensor plate trace 3835 that is on a lower layer
of the
PCB, there is a first active shield plane 3837 on a layer of the PCB above the
sensor
plate trace 3835 and a second active shield plane 3838 on a PCB layer below
sensor plate trace 3835. The first active shield plane 3837, the second active
shield
plane 3838, and shield traces 3836 are all coupled together and are all driven
as an
active shield. In the prior art the active shielding may comprise up to 82% of
the
length of the sensor plate trace 3835.
[0323] In these prior art detectors, the material that is between the
sensor plate
trace 3835 and the ground plane 3833 may absorb humidity. The material under
some of the sensor plate traces 3835 may absorb more humidity than the
material
that is under other sensor plate traces 3835. As a result, exposure to
humidity may
cause the relative sensor readings of the sensor plate traces 3835 to change.
In
other words, when exposed to humidity some of the sensor plate 3805 sensor
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readings may change more than other sensor plate 3805 sensor readings, as a
result of the humidity. Undesirably, the change is the result of the humidity
being
absorbed between the sensor plate trace 3835 and ground ¨ not as a result of
an
obscured feature being present. Improved obscured feature detectors, according
to
the present disclosure, may shield the sensor plate traces 3835 for more than
82%
of the length of the sensor plate trace 3835.
[00324] FIG. 39 is a cross-sectional view of an obscured feature detector
3901,
according to another embodiment, illustrating electric field patterns. FIG. 39
shows
an orientation of the electric field lines 3904, 3905 according to previously
mentioned
embodiments, where the electric field lines 3904, 3905 curve around the side
of the
obscured feature detector 3901. FIG. 39 shows an obscured feature detector
3901
that has the electric field lines 3904, 3905 extending from the sensor plates
3908
and ending on a common plate(s) 3906, 3907. There the sensor plates 3908 are
located on the bottom of the obscured feature detector 3901 and the common
plate(s) 3906, 3907 is located on the sides of the obscured feature detector
3901. A
shielding plate 3909 (e.g. an active shield) is disposed between the sensor
plates
3908 and the common plate(s) 3906, 3907, causing the electric field lines
3904,
3905 to extend down, outward, and up around the sides of the obscured feature
detector 3901.
[00325] The common plate(s) 3906, 3907 may comprise a single plate or a number
of different plates that are electrically connected, thereby maintaining a
uniform
voltage while extending along various sides of the obscured feature detector
3901.
To ensure that the electric field lines 3904, 3905 do not extend in a straight
line from
the sensor plates 3908 to the common plate(s) 3906, 3907 or otherwise
penetrate
the obscured feature detector 3901, a shielding plate 3909 may be positioned
between the sensor plates 3908 and the common plate(s) 3906, 3907. The
shielding
plate 3909 may hold the same charge or voltage as the sensor plates 3908 so
that
the capacitance between them may become unimportant. If the shielding plate
3909
has the same voltage or charge as the sensor plates 3908, the electric field
lines
3904, 3905 coming from the sensor plates 3908 will not be drawn to the
shielding
plate 3909, and will curve around it in order to reach a plate with a
different potential
such as the common plate(s) 3906, 3907. The shielding plate 3909 may be
positioned advantageously to cause the electric field lines 3904, 3905 to be
directed
around the edges or sides of the obscured feature detector 3901. For example,
in
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some embodiments the shielding plate 3909 may be located on a layer directly
above the sensor plates 3908 and cover the entire area of the sensor plates
3908.
In some embodiments, the shielding plate 3909 may then extend around the ends
(or extremes) of the sensor plates 3908 and lower itself until the portion of
the
shielding plate 3909 that extends beyond the area of the sensor plates 3908
lies on
the same plane as the sensor plates 3908. The portion of the shielding plate
3909
that is on the same plane as the sensor plates 3908 may then extend to the
extreme
ends of the obscured feature detector 3901, thereby forming a lip 3910 around
the
sensor plates 3908. Ideally, the shielding plate 3909 would cause the electric
field
lines 3904, 3905 to reach from the sensor plates 3908 to the common plate(s)
3906,
3907 only by curving around the sides of the obscured feature detector 3901.
[0326] In some applications, it may be desirable to have the electric field
lines
3904, 3905 diverge from the obstructed feature detector 3901 such that they
circle
around the side of the obscured feature detector 3901. If the electric field
lines 3904,
3905 are allowed to curve around the sides of the obscured feature detector
3901,
they may be able to penetrate further into a surface than were they confined
to the
area directly in front of the sensor plates, which may cause the sensor plates
3908 to
yield more accurate or consistent readings. In some applications, it may be
desirable to sense around the sides of the obscured feature detector 3901,
rather
than only directly in front of the sensor plates 3908.
[00327] FIG. 40 is a cross-sectional view of an obscured feature detector
4001,
according to another embodiment, illustrating electric field patterns. FIG. 40
shows
an orientation of the electric field lines 4004, 4005 curving out and up and
around the
sides of the obscured feature detector 4001. The obscured feature detector
4001
includes a housing 4019, and a sensor plate board 4040 (e.g., a PCB). In some
embodiments, the housing 4019 may comprise an upper housing, an on-off switch
4024, a handle 4014, and a plurality of light pipes 4018. The sensor plate
board
4040 may be a multi-layered PCB with a top layer 4044, a second layer 4043, a
third
layer that may be an active shield 4009, and a bottom layer that includes
sensor
plates 4008. Additional components of the sensor plate board 4040 may include
components described above with reference to FIG. 23.
[00328] FIG. 40 shows an obscured feature detector 4001 that forms electric
field
lines 4004, 4005 extending from sensor plates 4008 and ending on one or more
common plates 4006. The sensor plates 4008 are positioned on the bottom of the
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obscured feature detector 4001 and the one or more common plates 4006 are
located on a different plane from the sensor plates 4008, to be positioned a
greater
distance from a surface through which the obscured feature detector 4001 may
be
detecting an obscured feature. The common plate(s) 4006 may comprise a single
plate or a number of different plates that are electrically connected, thereby
maintaining a uniform voltage. A shielding plate 4009 (e.g. an active shield)
is
disposed between the sensor plates 4008 and the common plate(s) 4006. Electric
fields (represented by electric field lines 4004, 4005) form between the
sensor plates
4008 and the common plate(s) 4006, and the shielding plate 4009 causes the
electric field lines 4004, 4005 to extend down, outward, and up around the
sides of
the obscured feature detector 4001. Stated otherwise, the shielding plate 4009
restricts the electric field lines 4004, 4005 from extending in a straight
line from the
sensor plates 4008 to the common plate(s) 4006, 4007.
[0329] The shielding plate 4009 may be and active shield driven at the same
charge or voltage as the sensor plates 4008 so that the capacitance between
the
shielding plate 4009 and the sensor plates 4008 may be nominal and non-
impactful
to the sensing of the sensor plates 4008. If the shielding plate 4009 has the
same
voltage or charge as the sensor plates 4008, the electric field lines 4004,
4005
generated from the sensor plates 4008 will not be drawn to the shielding plate
4009,
and will curve around it in order to reach a plate with a different potential,
such as the
common plate(s) 4006. As noted, the shielding plate 4009 may be positioned
advantageously to cause the electric field lines 4004, 4005 to be directed
downward
and then out and around the edges or sides of the obscured feature detector
4001.
For example, in some embodiments the shielding plate 4009 may be located on a
layer directly above (e.g., away from a surface through which the obscured
feature
detector 4001 may be detecting an object) the sensor plates 4008 and cover the
entire area of the sensor plates 4008.
[0330] By configuring the electric field lines 4004, 4005 to curve around
the sides
of the obscured feature detector 4001, the electric field lines 4004, 4005 may
be able
to penetrate further into a sensed object 4090 and/or further into a surface
to sense
an obscured object than were they confined to the area directly in front of
the sensor
plates. Deeper penetration of the electric field lines 4004, 4005 enables the
sensor
plates 4008 to yield more accurate and/or consistent readings, particularly as
a
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thickness of the sensed object 4090 and/or a thickness of a surface of
detection
changes.
[0331] The embodiments herein may be used for a variety of purposes other
than
detecting obscured features. FIG. 40 provides an illustrative example of using
an
embodiment of an obscured feature detector 4001 for sensing an object 4090.
For
example, in a manufacturing or production-line environment that involves the
handling or testing of biological products, a disclosed embodiment may be
employed
to detect whether or not a product has changed its electro-chemical
properties. If, to
further the example, the product at hand is a type of produce such as a fruit
or
vegetable, the product may change its dielectric properties (such as its
relative static
permeability) as it decomposes or varies its ripeness. Since capacitance is a
function of the relative static permeability (otherwise known as the
dielectric
constant) of the material between two capacitive plates, the capacitance
measured
by the embodiment may vary when products of different ripeness pass through
the
sensing fields. In this example, an obscured feature detector according to one
embodiment of the present disclosure may be used to sense whether or not a
product is within a desired specification of ripeness. Since the obscured
feature
detector may use a multitude of sensor plates, the measurement may be able to
provide more resolution of detail than what would be possible if only a single
pair of
capacitive plates were being used.
[0332] Another application of the disclosed embodiments may involve the
investigation of the electrical properties of various materials. In some
situations, it
may be important to determine some electrical properties of a material without
altering the position, shape, or structural integrity of the material. A
disclosed
embodiment on or near the material at hand may measure the capacitance and
possibly compare the measurement to that of a reference material. The
capacitance
measured, or the difference in capacitances when compared against a reference
material, may yield a variety of details regarding the electrical properties
of the
material at hand.
[0333] The disclosed embodiments may also be used to provide details about
the
curvature or shape of a surface. If a disclosed embodiment is utilized along a
curved
or angled surface, for example, sensor plate readings may yield different
values
depending on a distance of the sensor plate from the surface. From the
variations in
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sensor values, the disclosed embodiments may be able to provide insight with
regards to the gradient or angle of the surface.
[0334] The sensor values may also vary according to the texture of the
material
within the sensing field. For example, if the material at hand is porous,
grainy,
rough, smooth, fibrous, or otherwise textured, the disclosed embodiments may
be
employed to provide details about that texture. In some applications, it may
be
possible to use the disclosed embodiments to make inferences regarding the
density
of a given material, or to determine other quality characteristics of a
product that
dependent upon its dielectric constant.
[0335] Another application of the disclosed embodiments may involve
determining if a container is filled to the proper level, or if it has the
right quantity of
items.
[0336] FIG. 41 is a view of a sensor plate cluster 4100 that includes
sensor plates
4013, an active shield plate 4102, an active shield center 4101, and a common
ring
4105. FIG. 41 shows eight sensor plates 4103. The sensor plates 4103 are
arranged radially around a center location. In operation the sensor plates
4103, the
active shield plate 4102, and the active shield center 4101 may all be driven
simultaneously with a common signal. The sensor plates 4103, the active shield
plate 4102, and the active shield center 4101 may not be electrically coupled
to each
other, but because they are each driven with the same signal the electric
field that
they create may be equivalent to the electric field that would be created if
they were
each coupled to each other. Together they may form the first end of a common
electric field.
[0337] There is a common ring 4105 that may form the second end of the
common electric field. In some embodiments the common ring 4105 is driven with
0
volts. In other embodiments it may be driven with a different unchanging
voltage, or
with an alternating voltage. Although there is common electric field that is
created by
the sensor plates 4103, the active shield plate 4102, and active shield center
4101
all driving together, nevertheless each element contributes to a particular
portion of
the common electric field. For example, the portion of the electric field that
is driven
from the sensor plate 4103 on the lower-left side of the sensor plate cluster
4100 will
be located primarily in the lower-left side of the sensor plate cluster 4100.
For
example, the field lines from the lower-left sensor plate 4110 may originate
at that
particular sensor plate 4110. The field lines from the lower-left sensor plate
4110 will
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surrounded by field lines from the active shield center 4101, and field lines
from the
active shield plate 4102, and field lines from neighboring sensor plates. It
is as
though the field lines from the lower left sensor plate 4110 are being guided
by the
field lines from the surrounding elements in the sensor plate cluster 4100.
For
example, the field lines from the neighboring sensor plates will bound the
lower-left
sensor plate 4110 field lines on either side. The field lines from the active
shield
plate 4102 will bound the field lines from the lower-left sensor plate 4110 on
the top
(where the top is the part of field that is furthest from the plane of the
sensor plates).
Likewise the field lines from the active shield plate 4012 will bound the
field lines
from the lower-left sensor plate 4110 on the bottom. If the relative
geometries and
positions of surrounding elements change the field lines from the lower-left
sensor
plate will likewise change.
[0338] By configuring surrounding electric fields, a product designer can
control
what is being sensed because each sensor plate will primarily sense in the
path of its
respective electric fields. Using this technique it is possible to control
where the
electric fields will be located. For example, to sense less of the material
(e.g., the
surface) that is close to the plane of a sensor plate 4103, a product designer
may
increase the active shield plate distance 4104 (e.g., a dimension of a
separation
between a sensor plate 4103 and the common ring 4105). For example, a product
designer may choose to reduce the size of the sensor plates 4103 by
simultaneously
increasing the active shield plate distance 4104. Implementing this design
change
will raise the lower bound on the sensor plate field lines such that the
sensed field
lines are located along an arc that is further (e.g., deeper into the sensed
surface)
from the plane of the sensor plate 4103. It may be advantageous to avoid
sensing
inconsistencies in the surface. For example, if the surface was a wall made of
sheetrock there could be inconsistencies could be due to air bubbles in the
sheetrock, variations in surface texture, inconsistencies in the paint,
inconsistencies
due to seams between sheets of sheetrock, or other factors. In some
embodiments
it may be preferable to sense less of the inconsistencies in the surface so
that
sensor plate readings would be more representative of obscured features that
may
be further from the plane of the sensor plate 4103, which it may be desirable
to read.
[0339] FIG. 42 is an alternate sensor plate cluster 4200 that includes
sensor
plates 4203, an active shield plate 4202, and an active shield center 4201.
The
sensor plate cluster 4200 of FIG. 42 may be used in the obscured feature
detector
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shown 4300 in FIG. 43. The embodiments illustrated in FIGS. 42 and 43 may
function very similarly to the configuration in FIG. 41, with a difference
being the
location of the common plate on the opposite side of the PCB. Positioning the
common plate on the opposite side of the PCB may cause the field lines to
extend
deeper into the surface and may drive the field lines further across a broader
spectrum of an obscured feature. As a result, obscured feature detectors that
include the design of FIG. 42 and FIG. 43 may sense more deeply into a sensed
surface, and may sense over a broader area compared to the configuration in
FIG.
41.
[0340] FIG. 43 is a side view of an embodiment of an obscured feature
detector
4300 that may use the sensor plate cluster 4200 shown in FIG. 42. The obscured
feature detector 4300 is positioned on a surface 2. There is a handle 4314 by
which
a user can grasp the device and a button 4324 that the user may actuate or
otherwise manipulate to turn on the obscured feature detector 4300. A light
pipe
4318 may guide the light from the indicators 4316 on a PCB 4330 to a location
where the user may view the light from the indicators 4316. The PCB 4330 may
include be four layers. The top layer 4344 may include a majority of circuitry
of the
PCB 4330. A second layer 4343 of the PCB 4330 may include various routing of
signals. The third layer may comprise an active shield layer 4202. The active
shield layer 4202 may cover or otherwise encompass nearly the entire third
layer of
the PCB 4330, thereby shielding the sensor plates 4203 from the sensing
circuitry of
the top layer 4344. The sensor plates 4203 may be disposed on the fourth
layer.
There is also an active shield center 4201 that is in the center of the PCB
4330 on
the fourth layer.
[0341] In one embodiment, the sensor plates 4203, the active shield center
4201,
and the active shield layer 4202 are all driven with the same signal. In other
words,
each is driven with signals that have the same voltage at the same point in
time.
Because they are driven together, they create an electric field together. As a
result
the electric field that is created is the same electric field that may be
created if the
active shield layer 4202, and sensor plates 4203, and active shield center
4201 were
all electrically coupled to each other, because they are each driven with the
same
signal. Together the active shield layer 4202, and sensor plates 4203, and
active
shield center 4201 all form a first end of an electric field. The electric
fields 4304,
4305 may all have a second end of the electric field at a hand guard common
plate
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4306. In this embodiment, edge electric fields 4305 that are near the edge of
the
sensor plate cluster 4200 are driven by the active shield layer 4202. These
edge
electric fields 4305 may originate at the active shield layer 4302 that is
near the
edge. In this embodiment they penetrate the surface 2, then wrap around and
terminate at the hand guard common plate 4306. In some embodiments the hand
guard common plate 4306 is driven with 0 volts. In other embodiments, the hand
guard common plate 4306 may be driven with a different unchanging voltage, or
with
an alternating voltage. These edge electric fields 4305 may not penetrate
deeply
enough to pass through the obscured feature 3. Because these electric fields
only
penetrate the surface 2 and may not penetrate deeply enough to reach the
obscured
features, the edge electric fields may only vary depending upon the properties
of the
surface 2. For example if there are inconsistencies in the surface 2, the edge
electric field 4305 will experience a corresponding change. Advantageously,
the
edge electric field 4305 may not be sensed by the sensor plates 4305.
[0342] For many applications the sensor plaster cluster 4200 shown in FIG.
42
may function better than the sensor plate cluster shown in FIG. 22. The sensor
plate
cluster 4200 shown in FIG. 42 may avoid sensing some of the surface
inconsistencies so that the sensor plate readings are better focused on the
obscured
features that may be further from the plane of the sensor plates 4203. This
will
advantageously allow the obscured feature detector 4300 to sense more
accurately
and more deeply.
[0343] FIG. 44 is a sensor plate cluster 4413 of an obscured feature
detector,
according to one embodiment. The sensor plate cluster 4413 includes multiple
sensor plates 4404, 4405, 4406. The sensor plates 4404, 4405, 4406 are
configured
to form the first end of an electric field. A common plate 4401 is configured
to form a
second end of the electric field. An active shield plate 4410 is disposed
between the
sensor plates 4404, 4405, 4406 and the common plate 4401 and is driven with a
voltage. In this embodiment of FIG. 44, the end sensor plates 4404 have less
surface area than the non-end sensor plates 4406. There is a common plate
width
4412, and an active shield plate width 4411, and a non-end sensor plate width
4407,
and an end sensor plate width 4408. There is also an active shield region
plate
4403. The active shield region plate 4403 may be on a different plane. In FIG.
44
the active shield region plate 4403 is represented by the white space on the
printed
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circuit board because in the illustrated embodiment it is on a different layer
of the
PCB.
[0344] In this illustrated embodiment of FIG. 44, the sensor plates 4404,
4405,
4406 are driven with a signal. The active shield plate 4410 and active shield
region
plate 4403 are driven with the same signal as the sensor plates 4404, 4405,
4406.
Likewise when one sensor plate 4404, 4405, 4406 is sensed the other sensor
plates
4404, 4405, 4406 in the array are driven with the same voltage signal.
[0345] The smaller sensor area of the end sensor plates 4404 may make the end
sensor plates 4404 less responsive to changes in a surface 2, such that the
responsiveness of the end sensor plates 4404 more closely matches the
responsiveness of the non-end sensor plates 4405, 4406. Further, an electric
field
formed between an end sensor plate 4404 and the common plate 4401 will be
smaller than were the surface area end sensor plate 4404 identical (or closely
similar) to the surface area of the non-end sensor plates 4405, 4406. In other
words,
the smaller surface area of the end sensor plate 4404 results in a smaller
electric
field that is more similar in shape (including more similar in depth into the
surface of
detection) to the electric field between a non-end sensor plate 4405, 4406 and
the
common plate 4401. An electric field between a smaller area end sensor plate
4404
and the common plate 4401 does not diverge as drastically as an end sensor
plate
having the same surface area as a non-end sensor plate. The electric fields
between the end sensor plates 4404 and the common plate 4401 are more similar
to
the electric fields between non-end sensor plates 4405, 4406 and the common
plate
4401. As noted previously, the more similar shape of the electric field
translates in
more predictable readings of the sensor plates, and thereby more accurate
detections of obscured features.
[0346] FIG. 45 is a side view of an obscured feature detector 4500 that may
use
the sensor plate cluster 4413 that is shown in FIG. 44. The obscured feature
detector 4500 includes a handle 14 that a user may grip to grasp the device,
and a
button 24 that can be actuated to turn on the obscured feature detector 4500.
In
FIG. 45, the obscured feature detector 4500 is positioned on a surface 2.
[0347] A light pipe 8 may guide the light from the indicators 6 on the PCB
to a
location where the user may view the light from the indicators 6. The obscured
feature detector 4500 may include a four-layer PCB 4510. Most of the sensing
circuitry, which is not shown, may be disposed on the top layer 44 of the PCB
4510.
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The second layer 43 of the PCB 4510 may include various routing of signals. A
third
layer of the PCB 4510 includes an active shield layer 4513. On the fourth
layer are
disposed sensor plates 4406, a common plate 4401, and an active shield plate
4410.
[0348] In one embodiment, the sensor plates 4406, the active shield plate
4410,
and the active shield layer 4513 are all driven with the same voltage signal.
In other
words, each is driven with signals that have substantially the same voltage at
the
same point in time. As they are driven together, they create an electric field
together. As a result the electric field that is created may be the same
electric field
that would be created if the active shield layer 4513, and sensor plates 4406,
and
active shield plate 4410 were all electrically coupled to each other, because
they are
each driven with the same signal. Together the active shield layer 4513, and
sensor
plates 4406, and active shield plate 4410 all form a first end of an electric
field. The
electric fields 4501, 4502, 4503, 4504, 4505 may all have a second end at the
common plate 4401.
[0349] In the embodiment shown in FIG. 45 there are five electric field
lines 4501,
4502, 4503, 4504, and 4505 that are illustrated. There are three sensed
electric field
lines 4501, 4502, and 4503. There are likewise two un-sensed electric field
lines
4504, 4505. In the embodiment shown in FIG. 45 it may be desirable to sense
objects in the obscured feature region 4508, and to avoid sensing the surface
2.
[0350] Although all of the electric field lines comprise a common electric
field only
the portion of the field that is driven by the sensor plates 4406 may be
sensed. The
electric fields 4504, 4505 that are driven by the active shield plate 4410 may
not
penetrate deeply enough to pass through the obscured feature 3. Because these
electric fields 4504, 4505 only penetrate the surface 2 and may not penetrate
deeply
enough to reach the obscured features, a reading of the un-sensed electric
fields
4504, 4505 may only vary depending upon the properties of the surface 2. For
example if there are inconsistencies in the surface 2 the un-sensed electric
field
4504 and 4505 will experience a corresponding change. Advantageously the un-
sensed electric fields 4504 and 4505 may not be sensed by the sensor plates
4406.
[0351] A product designer can vary the relative sizes of the different
components,
namely the sensor plates 4406, the active shield plate 4410, and the common
plate
4401, to target the sensing at the desired depth. For example, if the surface
2 is
relatively thin it may be desirable to have an active shield plate 4410 that
is relatively
narrow so that only a very small portion of the field will not be sensed.
Likewise, to
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detect obscured features that are further from the sensor plates 4406, or to
sense
through a thicker surface 2, it may be desirable to have an active shield
plate 4410
that is relatively wide so that the sensing field is directed deeper. Likewise
to sense
through a surface 2 with a lot of inconsistency it may be preferred to have a
wider
active shield plate 4410 so that the sensed fields sense less of the surface
2.
[0352] It is understood that the sensed electric field lines 4501, 4502,
4503 will
need to pass through the surface 2 twice in order to detect an obscured
feature 3.
So the sensor plate 4406 readings will be vulnerable to inconsistencies in the
surface 2 in the region where these field lines pass. Fortunately, however, by
not
sensing field lines that only pass through the surface 2 the quality of the
sensing may
be improved. The result being that the sensor plates 4406 can better identify
a
location of obscured features 3 because the readings may not be clouded by
inconsistencies in the surface 2. The result being that it is possible to be
selective
about where what material is being sensed.
[0353] In order to be effective, the active shield plate 4410 may be
positioned
between the common plate 4401 at the sensor plates 4404, 4405, 4406 so that
the
electric fields generated from the active shield plate 4410 may in effect push
the
sensed field lines deeper into and through the surface 2. The width of the
active
shield plate 4410 may vary by application. It may be recommended for many
applications that the minimum dimension for the active shield plate width is
about
18% of the total width of the sum of the width of the non-end sensor plate
width
4407, plus the active shield plate width 4411, plus common plate width 4412.
For
many applications a suitable active shield plate width may be much larger. For
example 30% may improve performance in many applications, and 40% may be an
additional improvement. Likewise values for the active shield plate width that
are
closer to 50% of the total width of the sum of the width of the non-end sensor
plate
width 4407, plus the active shield plate width 4411, plus common plate width
4412
may be ideal for many applications.
[0354] In terms of hard dimensions a 13 millimeter wide active shield plate
width
may be a minimal dimension, with better performance at 20 millimeters, 25
millimeters, or 30 millimeters wide. Those skilled in the art can determine
the
dimensions suitable for a particular application.
[0355] In some embodiments the active shield, which may be on the active
shield
plate 4410, is driven with a voltage signal that is the same as the voltage
signal on
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the sensor plates 4406. In some embodiments the active shield is driven with
an
unchanging voltage, such as OV. In some embodiments the active shield is
driven
with a voltage signal that is a ratio of the sensor plate voltage signal,
wherein the
ratio may be more than one, or less than one, such that the active shield
voltage
signal may be larger than the sensor plate voltage signal or less than the
sensor
plate voltage signal. In some embodiments the active shield is positioned
between
the common plate 4401 and the sensor plates 4406. If the active shield voltage
signal is greater than the sensor plate voltage signal it may have the effect
of driving
the sensor plate electric fields deeper into the surface. Likewise if the
active shield
voltage signal is less than the sensor plate voltage signal it may have the
effect of
driving the sensor plate electric fields less deeply into the surface. In some
embodiments the magnitude of the active shield voltage level can be changed by
the
user, or by the controller to sense at different depths. In some embodiments
an
image of the obscured features at different depths can be ascertained by
performing
multiple sensor plate reads with different active shield voltage signals. Such
readings may also be performed by an array of sensor plates in a linear, or
grid-like
array to create an image of obscured features.
[0356] FIG. 46 is a side view of an obscured feature detector 4600, which
is
similar to the obscured feature detector 4500 of FIG. 45. A difference between
the
obscured feature detector 4500 in FIG. 45 and the obscured feature detector
4600 of
FIG. 46 is the position of the common plate 4620 relative to the sensor plates
4606
and active shield plates 4610. In the obscured feature detector 4600 in FIG.
46 the
active shield layer 4613 is substantially between the sensor plates 4606 and
the
common plate 4620. The obscured feature detector 4600 in FIG. 46 may be
configured to cause the field lines (e.g., the electric fields 4601, 4602,
4603, 4604,
4605) to penetrate more deeply into the surface, and may enable obscured
feature
detectors that can sense more deeply, or that have a smaller size. In the
embodiment illustrated in FIG. 46 the field lines travel more than 180 degrees
along
an arc between the common plate 4620 and the sensor plates 4606. In some
embodiments the common plate 4620 and sensor plates 4606 are on opposite sides
of the active shield 4613. In some embodiments the common plate 4620 and
sensor plates 4606 are on opposite sides of the printed circuit board 4610.
[0357] The obscured feature detector 4600 includes a handle 14 that a user
may
grip to grasp the device, and a button 24 that can be actuated to turn on the
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obscured feature detector 4500. In FIG. 46, the obscured feature detector 4600
is
positioned on a surface 2.
[0358] A light pipe 8 may guide the light from the indicators 6 on a PCB
4610 to a
location where the user may view the light from the indicators 6. The obscured
feature detector 4600 may include a four-layer PCB 4610. Most of the sensing
circuitry, which is not shown, may be disposed on the top layer 44 of the PCB
4610.
The second layer 43 of the PCB 4610 may include various routing of signals. A
third
layer of the PCB 4610 may include an active shield layer 4613. On the fourth
layer
are disposed sensor plates 4606, and an active shield plate 4610.
[0359] In one embodiment, the sensor plates 4606, the active shield plate
4610,
and the active shield layer 4613 are all driven with the same voltage signal.
In other
words, each is driven with signals that have substantially the same voltage at
the
same point in time. As they are driven together, they create an electric field
together. As a result the electric field that is created may be the same
electric field
that would be created if the active shield layer 4613, and sensor plates 4606,
and
active shield plate 4610 were all electrically coupled to each other, because
they are
each driven with the same signal. Together the active shield layer 4613, and
sensor
plates 4606, and active shield plate 4410 all form a first end of an electric
field 4601,
4602, 4603, 4604, 4605. Each electric field 4601, 4602, 4603, 4604, 4605 may
all
have a second end at the common plate 4620.
[0360] In the embodiment shown in FIG. 46, five electric field lines 4601,
4602,
4603, 4604, 4605 are illustrated. There are three sensed electric field lines
4601,
4602, 4603. There are likewise two un-sensed electric field lines 4604, 4605.
In the
embodiment shown in FIG. 46 it may be desirable to sense objects in the
obscured
feature region 4608, and to avoid sensing the surface 2.
[0361] Although all of the electric field lines 4601, 4602, 4603, 4604,
4605
comprise a common electric field only the portion of the field that is driven
by the
sensor plates 4606 may be sensed. The electric fields 4604, 4605 that are
driven by
the active shield plate 4610 may not penetrate deeply enough to pass through
an
obscured feature 3. Because these electric fields 4604, 4605 only penetrate
the
surface 2 and may not penetrate deeply enough to reach the obscured features,
a
reading of the un-sensed electric fields 4604, 4605 may only vary depending
upon
the properties of the surface 2. For example if there are inconsistencies in
the
surface 2 the un-sensed electric field 4604 and 4605 will experience a
corresponding
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change. Advantageously the un-sensed electric fields 4604 and 4605 may not be
sensed by the sensor plates 4606.
[0362] A product designer can vary the relative sizes of the different
components,
namely the sensor plates 4606, the active shield plate 4610, and the common
plate
4620, to target the sensing at the desired depth. For example, if the surface
2 is
relatively thin it may be desirable to have an active shield plate 4610 that
is relatively
narrow so that only a very small portion of the field will not be sensed.
Likewise, to
detect obscured features that are further from the sensor plates 4606, or to
sense
through a thicker surface 2, it may be desirable to have an active shield
plate 4610
that is relatively wide so that the sensing field is directed deeper. Likewise
to sense
through a surface 2 with a lot of inconsistency it may be preferred to have a
wider
active shield plate 4610 so that the sensed fields sense less of the surface
2. In
some embodiments the designer may select the area to be sensed by changing the
size and position of the sensor plates 4606, active shield plate 4610, and
common
plate 4620.
[0363] FIG. 47 illustrates a plate configuration for an obscured feature
detector
4700, according to an embodiment of the present disclosure. The obscured
feature
detector 4700 includes a ground plate 4701, a lower active shield plate 4702,
an
upper active shield plate 4707, and a set of sensor plates 4703. A bottom PCB
layer
of a sensing board of the obscured feature detector 4700 comprises the ground
plate
4701, the lower active shield plate 4702, and the set of sensor plates 4703. A
PCB
layer adjacent to and above the bottom PCB layer comprises the upper active
shield
plate 4707.
[0364] The set of sensor plates 4703 comprises a plurality of individual
sensor
plates 4704, 4705, 4706, which may be arranged in a row. In the embodiment of
FIG. 47, at least one of the sensor plates of the set of sensor plates 4703
may be
irregular and/or asymmetric in form (e.g., shape). In at least the embodiment
of FIG.
47, each of at least three sensor plates has a different sensor plate shape.
For
example, each of the sensor plates 4704, 4705, 4706 takes a complex,
asymmetric
polygonal shape. More particularly, the first sensor plate 4704 has a first
shape that
is distinctive from the shape of each other sensor plate (and symmetrically
mirrored
to the last sensor plate). Similarly, the second sensor plate 4705 has a
second
shape that is distinctive from the shape of each of the other sensor plates
(and
symmetrically mirrored to the penultimate sensor plate). In the embodiment of
FIG.
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47, this pattern may repeat except for a group of similarly shaped sensor
plates at or
towards a center of the set of sensor plates 4703. By way of further example,
the
sensor plate 4706, a third-from-the-end sensor plate, is defined by a shape
that is
different from the shape of the sensor plates at the center of the set of
sensor plates
4703. In the embodiment of FIG. 47, each of the four sensor plates
sequentially from
an end of the set of sensor plates 4703 has a shape different from each of the
sensor plates of the four sensor plates, and also different from the shape of
the
center plates. Additionally, each of the four sensor plates sequentially from
the end
of the row of sensor plates in the set of sensor plates 4703 is defined by
eight or
more sides. Furthermore, each of the sensor plates 4704, 4705, 4706 has a
reverse-
symmetry counterpart at the opposite end of the set of sensor plates 4703. A
sensor
plate, e.g., the sensor plate 4704, may vary in width along its length. A
shape of a
sensor plate, such as the sensor plate 4704 may be defined by six or more
linear
sides. A sensor plate may be defined by eight or more linear sides. A sensor
plate
may be defined by a shape having at least one curved side or portion. In an
embodiment, the collection of varied shape sensor plates in the set of sensor
plates
4703 may be mirrored along a central axis so as to form a bilaterally
symmetric set
of sensor plates. In another embodiment, the set of sensor plates 4703 may be
bilaterally asymmetric.
[0365] At least one of the sensor plates of set of sensor plates 4703 may
couple
with a common plate (e.g., ground). In one embodiment, at least one sensor
plate
may couple with more than one common plate. In some embodiments, the sensor
plates 4704, 4705, 4706 may form a first end of the sensed electric field. In
some
embodiments, the ground plate 4701 may form a second end of the sensed
electric
field. In some embodiments, all of the sensor plates in the set of sensor
plates 4703
may be driven simultaneously. In some embodiments, the sensor plates of the
set of
sensor plates 4703 may be sensed one at a time. The lower active shield plate
4702
and the upper active shield plate 4707 may be driven simultaneously with the
set of
sensor plates 4703 with a signal that is similar to the signal applied to the
set of
sensor plates 4703.
[0366] In the embodiment of FIG. 47, the set of sensor plates 4703 is
driven and
forms the first end of a sensed electric field, and the ground plate 4701
forms the
second end of the sensed electric field. In another embodiment, the ground
plate
4701 may serve as one end of the electric field and may be replaced with a
driven
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source, and the set of sensor plates 4703 may hold another potential (e.g.,
ground)
to form the second end of the electric field. In another embodiment, sensing
of the
electric field may occur as between two or more sensor plates of the set of
sensor
plates 4703 and absent a ground (e.g., a ground plate).
[0367] FIG. 48 is a plate configuration for an obscured feature detector
4800,
according to an embodiment of the present disclosure. The obscured feature
detector 4800 includes a ground plate 4801, a lower active shield plate 4802,
an
upper active shield plate 4807, and a set of sensor plates 4803. A bottom PCB
layer
of a sensing board of an obscured feature detector 4800 comprises the ground
plate
4801, the lower active shield plate 4802, and the set of sensor plates 4803. A
PCB
layer adjacent to and above the bottom PCB layer comprises the upper active
shield
plate 4807.
[0368] The set of sensor plates 4803 comprises a plurality of twelve
individual
sensor plates, including the sensor plates 4804, 4805, 4806. In the embodiment
of
FIG. 48, each of the sensor plates 4804, 4805, 4806 takes a complex,
asymmetric
and irregular polygonal shape. Furthermore each of the sensor plates 4804,
4805,
4806 has a reverse-symmetry counterpart at the opposite end of the set of
sensor
plates 4803. At a medial portion of the set of sensor plates 4803 are four
sensor
plates each having a regular rectangular shape.
[0369] In some embodiments, all of the sensor plates in the set of sensor
plates
4803 may be driven simultaneously, and only one sensor plate in the set of
sensor
plates 4803 is driven at a time. The lower active shield plate 4802 and the
upper
active shield plate 4807 may also be driven simultaneously with the set of
sensor
plates 4803 with a signal that is similar to the signal on the set of sensor
plates 4803.
[0370] In an embodiment, the ground plate 4801 may not be coupled to a
circuit
ground, but may be electrically coupled to a driving source, a sensing source,
or
both. In an embodiment, the sensor plates of the set of sensor plates 4803 may
be
electrically coupled to a driving source, a sensing source, or both.
[0371] FIG. 49 is a plate configuration for an obscured feature detector
4900,
according to an embodiment of the present disclosure. The sensing zone 4900
includes a ground plate 4901, a lower active shield plate 4908, an upper
active
shield plate 4907, and a plurality of sensor plates 4904, 4905, 4906, 4909,
4910,
4911. A bottom PCB layer of a sensing board of an obscured feature detector
comprises the ground plate 4901, the lower active shield plate 4902, and the
sensor
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plates 4904, 4905, 4906, 4909, 4910, 4911. A PCB layer adjacent to and above
the
bottom PCB layer comprises the upper active shield plate 4907.
[0372] A second sensor plate reading comprises a combination of a reading
from
the sensor plate 4905 and a reading from the sensor plate 4911. A third sensor
plate reading similarly comprises a combination of a reading from the sensor
plate
4906 and a reading from the sensor plate 4910. In other words, a reading from
the
sensor plate 4904 comprises a first sensor plate reading, a combination of
readings
from the sensor plates 4905, 4911 comprises a second sensor plate reading, a
combination of readings from the sensor plates 4906, 4911 comprises a third
sensor
plate reading, and a reading from the sensor plate 4909 comprises a fourth
sensor
plate reading. Each of the sensor plates 4904, 4905, 4906, 4909, 4910, 4911
may
be driven simultaneously. Each of the four sensor plate readings may be
sampled
individually.
The lower active shield plate 4908 and the upper active shield plate 4907 may
be
driven simultaneously with the sensor plates 4904, 4905, 4906, 4909, 4910,
4911
and with a signal similar to the signal driving the sensor plates 4904, 4905,
4906,
4909, 4910, 4911. The ground plate 4901 may form an end of a sensed electric
field.
[0373] EXAMPLES
[0374] The following are some example embodiments within the scope of the
disclosure. In order to avoid complexity in providing the disclosure, not all
of the
examples listed below are separately and explicitly disclosed as having been
contemplated herein as combinable with all of the others of the examples
listed
below and other embodiments disclosed hereinabove. Unless one of ordinary
skill in
the art would understand that these examples listed below, and the above
disclosed
embodiments, are not combinable, it is contemplated within the scope of the
disclosure that such examples and embodiments are combinable.
[0375] Example 1. An obscured feature detector comprising: three or more
sensor plates arranged linearly to form a sensor array, each of the three or
more
sensor plates configured to form a first end of a corresponding electric field
and to
take a sensor reading of the corresponding electric field, wherein the
corresponding
electric field varies based on a proximity of the sensor plate to one or more
surrounding objects and on a material property of each of the one or more
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surrounding objects, wherein an end sensor plate at an end of the sensor array
has
a smaller area than a non-end sensor plate that is not at the end of the
sensor array;
a common plate to form a second end of the corresponding electric field of one
or
more sensor plates of the three or more sensor plates; a sensing circuit
coupled to
the three or more sensor plates, the sensing circuit being configured to
measure the
sensor readings on the three or more sensor plates; and an indicator to be
toggled
between a deactivated state and an activated state to indicate a location of a
region
of relative high sensor reading.
[0376] Example 2. The obscured feature detector of Example 1, wherein each
of
the sensor plates form an electric field with a single common plate of the one
or
more common plates.
[0377] Example 3. The obscured feature detector of Example 1, wherein the
three or more sensor plates are each driven with the same signal
simultaneously.
[0378] Example 4. The obscured feature detector of Example 1, wherein the
end
sensor plate is configured such that the corresponding electric field formed
by the
end sensor plate is geometrically similar to the corresponding electric field
formed by
a middle sensor plate.
[0379] Example 5. The obscured feature detector of Example 1, wherein the
sensor array and the common plate lie in a common plane that is to be parallel
to a
surface that obscures a detected feature at a time of detection.
[0380] Example 6. The obscured feature detector of Example 5, wherein the
three or more sensor plates are each driven with the same signal
simultaneously.
[0381] Example 7. The obscured feature detector of Example 5, wherein the
three or more sensor plates are each driven with the same signal
simultaneously and
wherein the sensing circuit measures the sensor reading of one of the three or
more
sensor plates.
[0382] Example 8. The obscured feature detector of Example 1, further
comprising an active shield, wherein the three sensor plates and the active
shield
are each driven with the same signal simultaneously.
[0383] Example 9. The obscured feature detector of Example 1, wherein the
three sensor plates and an active shield are each driven with the same signal
simultaneously and wherein the sensing circuit measures the sensor reading of
only
one of the sensor plates.
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[0384] Example 10. The obscured feature detector of Example 1, wherein the
common plate comprises a set of multiple individual plates, each individual
plate
forming a second end of the corresponding electric field of a sensor plate of
the three
or more sensor plates.
[0385] Example 11. The obscured feature detector of Example 10, wherein
each
of the multiple individual plates is independently activated.
[0386] Example 12. The obscured feature detector of Example 1, wherein a
width dimension of the end plate is less than a width dimension of the non-end
sensor plate.
[0387] Example 13. The obscured feature detector of Example 1, wherein a
width dimension of a first end of the end plate is less than a width dimension
of a
second end of the end plate.
[0388] Example 14. The obscured feature detector of Example 1, wherein all
non-end sensor plates of the three or more sensor plates have the same
dimensions.
[0389] Example 15. The obscured feature detector of Example 1, wherein a
voltage signal is driven on the common plate, wherein a reading is taken on a
sensor
plate of the three or more sensor plates, and wherein the reading is relative
to the
capacitance between the common plate and the sensor plate.
[0390] Example 16. An obscured feature detector comprising: three or more
sensor plates arranged linearly to form a sensor array, each of the sensor
plate
configured to form a first end of a corresponding electric field and to take a
sensor
reading of the corresponding electric field, wherein the corresponding
electric field
varies based on a proximity of the sensor plate to one or more surrounding
objects
and on a material property of each of the one or more surrounding objects,
wherein
each end sensor plate at an end of the sensor array has dimensions different
from
dimensions of a non-end sensor plate that is not at the end of the sensor
array, the
dimensions of the end sensor plates configured such that the corresponding
electric
field formed by each of the end sensor plates is geometrically similar to the
corresponding electric field formed by a middle sensor plate; a common plate
to form
a second end of the corresponding electric field of one or more sensor plates
on the
three or more sensor plates; a sensing circuit coupled to the three or more
sensor
plates, the sensing circuit being configured to measure the sensor readings of
the
three or more sensor plates; and an indicator to be toggled between a
deactivated
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state and an activated state to indicate a location of a region of relative
high sensor
reading.
[0391] Example 17. A method of detecting an obscured feature behind a
surface,
comprising: taking a sensor reading of three or more sensor plates of an
obscured
feature detector that is disposed on a surface, the three or more sensor
plates
arranged linearly in a sensor array, wherein an end sensor plate has a smaller
area
than a non-end sensor plate, and wherein the sensor reading is taken of a
region of
a sensing field formed between the three or more sensor plates and a common
plate
of the obscured feature detector; measuring, via a sensing circuit, the sensor
readings of the three or more sensor plates; comparing measurements of sensor
readings in different regions of the sensing field; and toggling an indicator
from a
deactivated state to an activated state to indicate a location of a region of
the
sensing field having a relatively high sensor reading.
[0392] Example 18. An obscured feature detector comprising: three or more
sensor plates arranged along a length to form a sensor array, each of the
three or
more sensor plates configured to form a first end of a corresponding electric
field and
to take a sensor reading of the corresponding electric field, wherein the
corresponding electric field varies based on a proximity of the sensor plate
to one or
more surrounding objects and on a material property of each of the one or more
surrounding objects, a common plate to form a second end of the corresponding
electric field of one or more sensor plates of the three or more sensor
plates; an
active shield plate that is driven with a voltage signal, wherein the active
shield plate
is positioned between the sensor plates and the common plate, and wherein the
active shield has a width dimension that is measured perpendicular to the
length of
the sensor array, wherein the active shield width is more than 18% of a
combined
width of the common plate, the active shield zone, and a sensor plate of the
three or
more sensor plates; a sensing circuit coupled to the three or more sensor
plates, the
sensing circuit being configured to measure the sensor readings on the three
or
more sensor plates; and an indicator to be toggled between a deactivated state
and
an activated state to indicate a location of a region of relative high sensor
reading.
[0393] Example 19. An obscured feature detector comprising: three or more
sensor plates arranged along a length to form a sensor array, each of the
three or
more sensor plates configured to form a first end of a corresponding electric
field and
to take a sensor reading of the corresponding electric field, wherein the
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corresponding electric field varies based on a proximity of the sensor plate
to one or
more surrounding objects and on a material property of each of the one or more
surrounding objects, a common plate to form a second end of the corresponding
electric field of one or more sensor plates of the three or more sensor
plates; an
active shield plate that is driven with a voltage, wherein the active shield
plate is
configured to influence the electric fields between the three or more sensor
plates
and the common plate, and wherein the active shield has a width that is
perpendicular to the length of the sensor array, wherein the active shield
plate width
is more than 18% of the combined width of the common plate, the active shield
zone,
and a sensor plate; a sensing circuit coupled to the three or more sensor
plates, the
sensing circuit being configured to measure the sensor readings on the three
or
more sensor plates; and an indicator to be toggled between a deactivated state
and
an activated state to indicate a location of a region of relative high sensor
reading.
[0394] Example 20. An obscured feature detector comprising: three or more
sensor plates arranged along a length to form a sensor array, each of the
three or
more sensor plates configured to form a first end of a corresponding electric
field and
to take a sensor reading of the corresponding electric field, wherein the
corresponding electric field varies based on a proximity of the sensor plate
to one or
more surrounding objects and on a material property of each of the one or more
surrounding objects; a common plate to form a second end of the corresponding
electric field of one or more sensor plates of the three or more sensor
plates; an
active shield plate that is driven with a voltage, wherein the active shield
is
configured to influence the electric fields between the three or more sensor
plates
and the common plate, and wherein the active shield plate has a width that is
perpendicular to the length of the sensor array, wherein the active shield
width is
more than 13 millimeters wide; a sensing circuit coupled to the three or more
sensor
plates, the sensing circuit being configured to measure the sensor readings of
the
three or more sensor plates; and an indicator to be toggled between a
deactivated
state and an activated state to indicate a location of a region of relative
high sensor
reading.
[0395] Example 21. An obscured feature detector comprising: a group of
three or
more sensor plates arranged radially around a center point, each sensor plate
of the
three or more sensor plates to form a first end of a corresponding electric
field and to
take a sensor reading of the corresponding electric field that varies based on
a
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proximity of the sensor plate to one or more surrounding objects and on a
material
property of each of the one or more surrounding objects; a common plate to
form a
second end of the corresponding electric field of one or more sensor plates of
the
three or more sensor plates; one or more active shield plates driven with a
voltage
and positioned outside of a perimeter of the group of three or more sensor
plates;
and a sensing circuit coupled to the three or more sensor plates, the sensing
circuit
being configured to measure the sensor readings of the three or more sensor
plates.
[0396] Example 22. The obscured feature detector of Example 21, wherein the
common plate is a ring disposed around the one or more active shield plates.
[0397] Example 23. The obscured feature detector of Example 21, wherein
multiple sensor plates of the three or more sensor plates are driven with the
same
signal simultaneously.
[0398] Example 24. The obscured feature detector of Example 21, wherein
multiple sensor plates of the three or more sensor plates and the one or more
active
shield plates are each driven with the same signal simultaneously.
[0399] Example 25. The obscured feature detector of Example 21, wherein
increasing the voltage on the one or more active shield plates causes the
field lines
from a sensor plate of the three or more sensor plates to take a path to the
common
plate that is further from the plane of the three or more sensor plates.
[0400] Example 26. The obscured feature detector of Example 21, wherein the
one or more active shield plates are driven with a static voltage level.
[0401] Example 27. The obscured feature detector of Example 21, wherein the
one or more active shield plates are driven with a non-static voltage level.
[0402] Example 28. The obscured feature detector of Example 21, wherein the
voltage signal on the one or more active shield plate matches a voltage signal
that is
on a sensor plate of the three or more sensor plates.
[0403] Example 29. The obscured feature detector of Example 21, wherein the
voltage signal on the one or more active shield plates is a ratio of the
voltage signal
that is on a sensor plate of the three or more sensor plates.
[0404] Example 30. The obscured feature detector of Example 21, wherein the
active shield plate, the common plate, and the three or more sensor plates are
substantially in the same plane.
[0405] Example 31. The obscured feature detector of Example 21, wherein a
voltage signal is driven on the common plate, and wherein a reading is taken
on a
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sensor plate of the three or more plates and the reading is relative to a
capacitance
between the common plate and the sensor plate.
[0406] Example 32. An obscured feature detector comprising: a group of two
or
more sensor plates arranged radially around a center point, each sensor plate
of the
two or more sensor plates to form a first end of a corresponding electric
field and to
take a sensor reading of the corresponding electric field that varies based on
a
proximity of the sensor plate to one or more surrounding objects and on a
material
property of each of the one or more surrounding objects; a common plate to
form a
second end of the corresponding electric field of one or more sensor plates;
one or
more active shield plates to be driven with a voltage and positioned outside
of the
perimeter of the group of two or more sensor plates; and a sensing circuit
coupled to
the two or more sensor plates, the sensing circuit being configured to measure
the
sensor readings of the two or more sensor plates.
[0407] Example 33. An obscured feature detector comprising: a common plate
positioned at a center point of a bottom of the obscured feature detector; one
or
more active shield plates driven with a voltage and arranged radially around
the
common plate; three or more sensor plates arranged radially around the one or
more
active shield plates, each sensor plate to form a corresponding electric field
with the
common plate, each sensor plate to take a sensor reading of the corresponding
electric field that varies based on a proximity of the sensor plate to one or
more
surrounding objects and on a material property of each of the one or more
surrounding objects; and a sensing circuit coupled to the three or more sensor
plates, the sensing circuit being configured to measure the sensor readings of
the
three or more sensor plates.
[0408] Example 34. An obscured feature detector according to any of the
forgoing examples having a plurality of sensor plates arranged in a row,
wherein the
sensor plate at each end of the row of sensor plates is defined by a shape
having six
or more sides.
[0409] Example 35. The obscured feature detector of Example 34, wherein the
sensor plate medially adjacent to either end sensor plate in the row of sensor
plates
is defined by a shape having at least six sides.
[0410] Example 36. The obscured feature detector of Example 35, wherein the
sensor plate next medially adjacent (or third from end) is defined by a shape
having
at least six sides.
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[0411] Example 37. The obscured feature detector of Example 36, wherein the
sensor plate next medially adjacent (or fourth from end) is defined by a shape
having
at least six sides.
[0412] Example 38. An obscured feature detector according to any of
Examples
34, 35, 36, and 37, wherein at least two medially disposed sensor plates are
of a
regular rectilinear shape.
[0413] Example 39. An obscured feature detector according to any of
Examples
34, 35, 36, and 37, wherein at least two medially disposed sensor plates are
of an
irregular rectilinear symmetric shape.
[0414] Example 40. An obscured feature detector according to any of
Examples
38 and 39, wherein the row of sensor detectors is bilaterally symmetric.
[0415] Example 41. An obscured feature detector according to any of
Examples
38 and 39, wherein the row of sensor detectors is bilaterally asymmetric.
[0416] Example 42. An obscured feature detector according to any of
Examples
40 and 41, wherein at least one sensor plate is defined by a curvilinear side
or side
portion.
[0417] Example 43. An obscured feature detector, according to any of
Examples
40 and 41, wherein the set of sensor plates are arranged in an array not of a
linear
row form.
[0418] Example 44. An obscured feature detector according to any of
Examples
40 and 41, wherein a first pair of sensor plates provide readings which are
combined
to be interpreted as a reading as from a single sensor plate.
[0419] Example 45. The obscured feature detector of Example 44, wherein a
second pair of sensor plates provide readings which are combined to be
interpreted
as a reading as from a single sensor plate.
[0420] Example 46. An obscured feature detector comprising: a sensor plate
array including three or more sensor plates, each of the three or more sensor
plates
configured to form a first end of a corresponding electric field and to take a
sensor
reading of the corresponding electric field, wherein the corresponding
electric field
varies based on a proximity of the sensor plate to one or more surrounding
objects
and on a material property of each of the one or more surrounding objects, the
three
or more sensor plates including: a first sensor plate that has a first shape,
a second
sensor plate that has a second shape that is different from the first shape of
the first
sensor plate; one or more common plates to form a second end of the
corresponding
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electric field of one or more sensor plates of the three or more sensor
plates; a
sensing circuit coupled to the three or more sensor plates, the sensing
circuit
configured to measure the sensor readings on the three or more sensor plates;
and
an indicator to be toggled between a deactivated state and an activated state
to
indicate a location of a region of relative high sensor reading.
[0421] Example 47. The obscured feature detector of Example 46, wherein at
least one of the three or more sensor plates is asymmetrical.
[0422] Example 48. The obscured feature detector of Example 46, wherein a
sensor plate of the three or more sensor plates has more than four linear
sides.
[0423] Example 49. The obscured feature detector of Example 46, wherein at
least one of the three or more sensor plates varies in width along a length of
the at
least one of the three or more sensor plates sensor plate.
[0424] Example 50. The obscured feature detector of Example 46, wherein the
three or more sensor plates comprise at least three different sensor plate
shapes.
[0425] Example 51. The obscured feature detector of Example 46, wherein at
least
one of the three or more sensor plates is defined by six or more linear sides.
[0426] Example 52. The obscured feature detector of Example 46, wherein at
least
one of the three or more sensor plates is defined by eight or more linear
sides.
[0427] Example 53. The obscured feature detector of Example 46, wherein the
sensor plate array is bilaterally symmetrical.
[0428] Example 54. The obscured feature detector of Example 46, wherein the
sensor plate array is bilaterally asymmetrical.
[0429] Example 55. The obscured feature detector of Example 46, wherein at
least
one of the three or more sensor plates couples to more than one common plate.
[0430] Example 56. The obscured feature detector of Example 46, wherein at
least
one of the three or more sensor plates is defined by at least one curved side.
[0431] Example 57. An obscured feature detector comprising: a sensor plate
array
including three or more sensor plates arranged in a geometric pattern having
one or
more ends, each of the three or more sensor plates configured to form a first
end of
a corresponding electric field and to take a sensor reading of the
corresponding
electric field, wherein the corresponding electric field varies based on a
proximity of
the sensor plate to one or more surrounding objects and on a material property
of
each of the one or more surrounding objects, the three or more sensor plates
including: one or more middle plates, and end plates at each end of the
geometric
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pattern, at least one of the end plates having an end shape that is different
from a
middle shape of the one or more middle plates; one or more common plates to
form
a second end of the corresponding electric field of one or more sensor plates
of the
three or more sensor plates; a sensing circuit coupled to the three or more
sensor
plates, the sensing circuit configured to measure the sensor readings on the
three or
more sensor plates; and an indicator to be toggled between a deactivated state
and
an activated state to indicate a location of a region of relative high sensor
reading.
[0432] Example 58. The obscured feature detector of Example 57, wherein the
geometric pattern includes a row of sensor plates including the three or more
sensor
plates.
[0433] Example 59. The obscured feature detector of Example 58, wherein the
three
or more sensor plates include one or more second-to-end plates adjacent to the
one
or more end plates, at least one of the one or more second-to-end plates
having a
second-to-end shape that is different from the middle shape of the one or more
middle plates.
[0434] Example 60. The obscured feature detector of Example 59, wherein the
second to end shape is different from the end shape of the at least one of the
one or
more end plates.
[0435] Example 61. The obscured feature detector of Example 59, wherein the
three
or more sensor plates include one or more third-to-end plates adjacent to the
second-to-end plates, at least one of the third-to-end plates having a third-
to-end
shape that is different from the middle shape of the one or more middle
plates.
[0436] Example 62. The obscured feature detector of Example 61, wherein the
third-
to-end shape is different from the second-to-end shape and the end shape.
[0437] Example 63. The obscured feature detector of Example 61, wherein the
three
or more sensor plates include one or more fourth-to-end plates adjacent to the
one
or more third-to-end plates, at least one of the one or more fourth-to-end
plates
having a fourth-to-end shape that is different from the middle shape of the
one or
more middle plates.
[0438] Example 64. The obscured feature detector of Example 63, wherein the
fourth-to-end shape is different from the third-to-end shape, the second-to-
end
shape, and the end shape.
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[0439] Example 65. The obscured feature detector of Example 63, wherein the
end
shape, the second-to-end shape, the third-to-end shape, and the fourth-to-end
shape
are each defined by eight or more linear sides.
[0440] It will be apparent to those having skill in the art that many
changes may
be made to the details of the above-described embodiments without departing
from
the underlying principles of the disclosure. The scope of the present
disclosure
should, therefore, be determined only by the following claims.
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