Note: Descriptions are shown in the official language in which they were submitted.
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NON-CONTACT MEASUREMENT DEVICE FOR ACCURATELY
DETERMINING ANGULAR MEASUREMENTS IN RELATION TO PLUMB
AND LEVEL
This application is a continuation-in-part of U.S. Patent Application Serial
No. 09/803,535 filed on March 9, 2001 and claims priority under 35 U.S.C.
~119(e) to United States Provisional Application No. 60/247,270 filed on
November 10, 2000 the specification and drawings of which are hereby
expressly incorporated by reference.
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates generally to a non-contact measurement
device and, more particularly, a hand-held or tool integrated measurement
device for quickly and accurately performing non-contact measurements of
the angle of a surface in relation to plumb or level.
Measurement of dimensions and angles of wood products and
woodworking equipment has up to now been performed through the use of
various mechanical and electronic calipers, squares, protractors, steel rules,
tape measurers, levels, and point range measuring devices. These various
devices suffer from mechanical inaccuracies and human visual limitations
(such as parallax). These devices also require sometimes difficult or
impossible direct physical contact with the object being measured. In
addition, it is often desirable to determine angular measurements, such as the
angle of a flat surface, in relation to plumb and/or level.
Therefore, it is the purpose of the present invention to improve
accuracy, remove most human judgement of measurement results, allow for
measurements that are impossible to perform mechanically, and provide
more convenient, faster measurements than conventional measurement
devices. Furthermore, it is the purpose of the present invention to provide
angular measurements in relation to plumb and/or level.
In accordance with the present invention, a hand-held or tool integrated
measurement device is provided for quickly and accurately performing non-
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contact measurements of angles associated with various objects in a home or
commercial work area. The measurement device generally includes a user
input element, a non-contact sensor, a gravity reference device, an image
processor, and a display element packaged in a portable housing assembly.
In operation, a user initiates the measurement by activating the user input
element associated with the measurement device. The non-contact sensor
receives a trigger signal from the user input element and is operative to
collect image data representative of at least a portion of the surface of a
measured object. Likewise, the gravity reference device receives the trigger
signal from the user input element and is operative to determine a local
gravity vector. The image processor in turn receives the image data from the
non-contact sensor and the local gravity vector from the gravity reference
device. The image data is converted into angular measurement data for the
surface of the measured object in relation to gravity. The display element is
operable to visually display the angular measurement data to the user.
For a more complete understanding of the invention, its objects and
advantages, reference may be had to the following specification. and to the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of a portable non-contact measurement
device in accordance with the present invention;
Figure 2 is a diagram illustrating laser triangulation technology as
employed in an exemplary non-contact sensor;
Figure 3 is a diagram illustrating laser triangulation technology as
employed by the non-contact measurement device of the present invention;
Figure 4 is a block diagram depicting the primary components of the
non-contact measurement device in accordance with the present invention;
Figures 5A and 5B are flow charts depicting an exemplary measurement
cycle for the non-contact measurement device in accordance with the present
invention;
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An exemplary portable measurement device 10 in accordance with the
present invention is shown in Figure 1. The portable measurement device 10 is
housed in a housing assembly 12 which is sized to be hand-held by a user. It
should be appreciated that housing assembly 12 may further include other
design features (such as a handle or a hand-formed gripping area) that
facilitate the portable nature of the measurement device 10. The operation of
the measurement device may be controlled via the user interface elements
integrated into the housing assembly 12. In this preferred embodiment, one or
more push buttons 14 are used to receive input from the user and a display 16
is used to visually output measurement data to the user.
Referring to Figure 2, the portable measurement device 100 is based on
well known laser triangulation technology heretofore employed in various
commercially available non-contact sensors. In general, a non-contact sensor
100 projects one or more planes of laser light 101 towards an object 102. The
laser planes 101 are projected by light source assemblies 107 that preferably
include a laser diode, a laser projection lens assembly and accompanying
electronics for controlling the light source assembly. The points of
intersection
103 of the projected laser plane and the object are then imaged by a
electronic camera assembly 104. The electronic camera assembly 104
preferably comprises an imaging array (e.g, CCD or CMOS), a lens assembly,
and accompanying electronics for controlling the electronic camera assembly.
The image data for a flat object oriented perpendicular to the laser
plane is a nominally straight line as shown in inset 105. Due to the
triangular
relationship between the light source and the electronic camera assembly,
displacement of the object 102 toward or away from the sensor 100 results in
the movement of the image data up and down, respectively. The resolution
of vertical displacement in the image (V) depends on the thickness of the
laser line, the number of pixels in the electronic camera and the overall
signal
to noise ratio of the imaging system. As will be apparent to one skilled in
the
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art, the triangulation angle (at the center of the field) is typically between
15
degrees and 25 degrees. For further details regarding an exemplary non-
contact sensor, reference may be had to the TriCam sensors manufactured
by Perceptron. Inc. of Plymouth, Michigan.
In accordance with the present invention, the portable measuring device
further incorporates a gravity reference device. The portable measuring device
200 illuminates the surface 201 of an object with two projected laser planes
as
shown in Figure 3. The measuring device 200 preferably uses at least two
projected laser planes to improve the accuracy of measurement data. One
skilled in the art will readily recognize that the second laser plane is used
to
eliminate error caused by a non-normal incident angle of the projected laser
plane with the surface of the measured object. In this way, the measuring
device 200 need not be perpendicular to the measure object in order to obtain
accurate angular measurement data for the surface of the measurement
object.
Inset 202 illustrates the image 204 as recorded by the sensor of the
intersection of the two laser planes with the surface 201. The angle 203
between the measured surface 201 of the object and a vector normal to the
sensor will map to an angle in the image 204. The relative distance between
the two lines in the image 204 can be used to mathematically resolve the
angle 205 between the planes of light 206 and the measured surface 201 of
the object. An internal gravity reference produces a local gravity vector 209.
Thus, the angle 207 between the sensor normal vector 208 and the local
gravity vector 209 is also known. Lastly, data from these various angles may
be used to calculate the angle 210 of the measured surface 201 in relation to
the gravity vector 209.
Figure 4 illustrates the basic components associated with the portable
measurement device 10 of the present invention. The portable measurement
device 10 generally includes one or more user input elements 18, a controller
20, a non-contact sensor 22, an image processor 24, a display 26, a gravity
reference device 30, and a power supply (e.g., a battery). It should be
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appreciated that one or more subcomponents from an exemplary non-contact
sensor (rather than a complete sensor unit) may be incorporated into the
portable measurement device 10.
One or more user input elements 18 receive input commands from a
user of the measurement device. Input commands may include power on/off
commands, measurement trigger commands, measurement mode
commands, measurement origin offset commands, etc. The input commands
are in turn communicated to the controller 20. The user input elements 18
may assume a variety of forms, including push buttons, radial knobs, a touch
screen display, or a combination thereof.
The controller 20 controls the overall operation of the measurement
device 10. For instance, the controller 20 interfaces with the non-contact
sensor 22 to facilitate acquisition of image data for a measured object. In
particular, the controller 20 may issue power on/off commands and/or power
setting commands to the light source associated with the non-contact sensor
22. The controller 20 may also issue power on/off commands, measurement
trigger commands, exposure commands, resolution setting commands,
and/or data transfer commands to the imaging array associated with non-
contact sensor 22.
The controller 20 also interfaces with the gravity reference device 30 to
facilitate acquisition of local gravity vector data. An exemplary gravity
reference device suitable for use in this application is marketed under the
brand name EZ-TILT 3000 and manufactured by Advanced Orientation
Systems, Inc. of Linden, New Jersey.
Furthermore, the controller 20 interfaces with the image processor 24.
The image processor 24 is adapted to retrieve image data from the non-
contact sensor 22 and to retrieve gravity vector data from the gravity
reference device 30. The image processor 24 is operable to convert the
image data into measurement data for the measured object. The image
processor 24 includes one or more software algorithms for converting the raw
image data into measurement data as is well known in the art. It is
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envisioned that a different algorithm may be used depending on the type of
measurement being taken (e.g., width of an object, angle between two
adjacent surface, etc.) by the device.
Of particular interest, the image processor 24 is further operable to
convert the image data into angular measurement data for a surface of the
measured object, and then determine the angular measurement of the
surface in relation to the gravity vector. The image processor 24 employs
various software algorithms for determining the angular measurement in
relation to the gravity vector. It is to be understood that the angular
measurement of the surface can be provided to the user in relation to plumb
(vertical) or level (horizontal).
A display 26 embedded into the housing of the measurement device is
used to visually display the measurement data to the user. To do so, the
display is adapted to receive the measurement data from the image processor
24. In addition, the display 26 may further receive input commands from the
controller as to how the dimensional data is to be displayed to the user. The
display 26 may be graphic or numeric and assume a variety of forms, such as
an LED or a LCD.
The portable measurement device 10 may optionally include an
external communication port 28 (e.g., RS-322, USB, wireless port, etc). It is
envisioned that the controller ~20 may transmit measurement data via the
communication port 28 to an external source. In addition, the controller 20
may also receive remote activation commands or updates to the software
algorithms via the communication port 28 from an external source.
A typical measurement cycle for the above-described measurement
device 10 is depicted in Figure 5. Initially, device preparation steps are
performed by the user. In step 400, the user selects the measurement mode
for the device. The measurement mode indicates the type of measurement
that is to be taken (e.g., width of an object, angle between two adjacent
surfaces, angle of a surface in relation to the gravity vector, etc.) by the
device. As will be apparent to one skilled in the art, the measurement mode
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determines the algorithm used to convert the image data into measurement
data as well as dictates the how the measurement data will be displayed to
the user. In addition, the sensor is powered on by the user in step 402. As a
result, the measure laser plane and possibly an auxiliary alignment beam are
projected from the measurement device 10.
Next, the user directs the measurement device towards the object to
be measured in step 404. In particular, the measurement device is positioned
such that the measured object falls within the field of view of the non-
contact
sensor. It is envisioned that an auxiliary laser light source may be used to
assist the user in localizing the measured object within the center of the
field
of view of the sensor.
The user can then trigger a measurement as shown in step 406. By
activating the applicable user input element, a trigger command is generated
and sent to the controller. In response to the trigger command, the controller
sets the camera exposure to some predefined value and then commands the
camera to capture image data at step 408. It is also envisioned that the user
may set the camera exposure via the user input elements as part of the
above-described device preparation process.
In a preferred embodiment of the present invention, the image data
may be partially processed to determine correctness of the exposure setting
as shown in step 410. One skilled the art will readily recognize that the
exposure setting is dependent on various factors such as the angle of
incidence and the material of the measured object. The adequacy of the
exposure is evaluated in step 412. If the exposure setting for the camera is
not correct, the controller may estimate the correct setting at step 416 and
adjust the exposure setting at step 418 before commanding the camera to
take another image. This process may be repeated until an accurate
exposure setting cycle is obtained. It is envisioned that no more than two
cycles would be needed in a typical application in order to achieve an
accurate exposure setting. Moreover, it is expected that the time for this
iterative process is much less than one second. In the event that no exposure
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setting is deemed to be adequate after some predefined number of iterations
or some predefined threshold time, then a fault indicator is provided to the
user at step 414.
If the exposure setting is deemed to be acceptable, then the image
data is fully processed in step 420. To do so, the image data is transferred
from the sensor to the image processor. The image processor in turn
converts the image data to measurement data using the applicable algorithm,
and applies the gravity sensor data. In step 422, the measurement data is
visually displayed to the user. In addition to the measurement data, a visual
indicator of the measurement mode as well as a visual representation of the
measured object may also be displayed to the user. In step 424, the
measurement data may be stored for subsequent processing in a memory
space residing on the device, or for possible transfer to a computer. The
above-described measurement cycle (or some portion thereof) may be
repeated to obtain additional measurement data.
Lastly, the measurement device may be powered down upon
completion of the measurement cycle at step 426. After some predefined
time period of inactivity, it is envisioned that the sensor will power down to
a
standby mode. In the standby mode, the display is still readable until the
measurement device is completely turned off. It is to be understood that only
the relevant steps of the measurement cycle are discussed above, but that
other software-implemented instructions may be needed to control and
manage the overall operation of the portable measurement device.
It should also be appreciated that the portable nature of the
measurement device 10 allows it to be placed on any flat surface (e.g., on a
workbench or on the floor), mounted in a stand, or positioned in other areas
of a typical work environment, such that the housing assembly of the device
serves as a reference plane for the measurement data.
Typical applications for the hand-held measurement device of the
present invention include, but are not limited to: measurement of the angle of
a nearby object, such as a wooden post, beam, or construction wall as it is
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raised into place to determine the point at which the object is perpendicular
to
the earth's surface; determination of when a nearby flat surface, such as a
tabletop, is directly level with the earth's surface; or determination of the
angle
of any nearby object, whether stationary or moving, in relation to gravity.
Thus, the measurement device may be used in any application where a
mechanical bubble level or electro-mechanical level is used. In addition, the
measurement device may be used in applications where said levels cannot
be used because of space limitations, or because the object being leveled is
too hot or too delicate to touch. Other types of specific applications
include,
but are not limited to: leveling refrigeration units; hanging cabinets;
installing
indoor and outdoor doors; installing windows; leveling floors; determining
grade and slope; and determining roof pitch.
From the foregoing, it will be appreciated that the present invention
provides a significant advance in the art of portable measurement devices.
The invention quickly and accurately performs non-contact measurements of
dimensions and/or angles associated with various objects in a home or
commercial work area. Of particular importance, the present invention
determines angular measurement data for the surface of an object in relation
to plumb or level. While the invention has been described in its presently
preferred form, it will be understood that the invention is capable of
modification without departing from the spirit of the invention as set forth
in
the appended claims.
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