Note: Descriptions are shown in the official language in which they were submitted.
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BAR CODE READER WITH AN INTEGRATED SCANNING
COMPONENT MODULE MOUNTABLE ON PRINTED CIRCUIT
BOARD
(This is a divisional application of Canadian application 2,255,186
filed December 2, 1998.)
BACKGROUND OF THE INVENTION:
Field of the Invention:
The present invention relates generally to a high-speed scanning
arrangement, and particularly although not exclusively to such a scanning
arrangement for use in hand-held or fixed optical scanners such as bar code
scanners. In one embodiment the invention relates to a bar code reader with an
integrated scanning component module mountable on a printed circuit board.
Description of the Related Art:
Various optical readers and optical scanners have been developed
heretofore to optically read bar code symbols applied to objects in order to
identify the object by optically reading the symbol thereon. The bar code
symbol itself is a coded pattern comprised of a series of bars of various
widths
and spaced apart from one another to bound spaces of various widths, the bars
and spaces having different light reflecting properties. The readers and
scanners electro-optically decoded the coded patterns to multiple digit
representations descriptive of the objects. Scanners of this general type have
been disclosed, for example, in U.S. Patent Nos. 4,251,798; 4,360,798;
4,369,361; 4,387,297; 4,593,186; 4,496,831; 4,409,470; 4,808,804;
4,816,661; 4,816,660; and 4,871,904, all of said patents having been assigned
to the same assignee as the instant invention and being hereby incorporated
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herein by reference:
As disclosed in the above-identified patents and applications, a
particularly advantageous embodiment of such a scanner resided, inter alia, in
emitting a light beam, preferably a laser beam, emitted from a light source,
preferably a gas laser or a laser diode, and in directing the laser beam to a
symbol to be read. En route to the symbol, the laser beam was directed to, and
reflected off, a light reflector of a scanning component. The scanning
component moved the reflector in a cyclical fashion and caused the laser beam
to repetitively scan the symbol. The symbol reflected the laser beam incident
thereon. A portion of the incident light reflected off the symbol was
collected
and detected by a detector component, e.g. a photodiode, of the scanner. The
photodiode had a field of view, and the detected light over the field of view
was
decoded by electrical decode circuitry into data desciprive of the symbol for
subsequent processing. The cyclically movable reflector swept the laser beam
across the symbol and/or swept the field of view during scanning.
U.S. Patent Nos. 4,387,297 and 4,496;831 disclose a high speed scanning
component including an electric motor operative for reciprocatingly
oscillating
a reflector in opposite circumferential, directions- relative to an output
shaft of
the motor. Electrical power is continuously applied to the motor during
scanning. The light beam which impinges on the light reflector is rapidly
swept across a symbol to be scanned in a predetermined cyclical manner. The
scanning component comprises at least one scan means for sweeping the
symbol along a predetermined direction (X-axis) lengthwise thereof. The
scanning component may also comprise another scan means for sweeping the
symbol along a transverse direction (Y-axis) which is substantially orthogonal
to the predetermined direction, to thereby generate a raster-type scan pattern
over the symbol. In addition to a single scan line and the raster-type
pattern,
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other types of scan patterns are also possible, such as, x-shaped, Lissajous,
curvilinear (see U.S. Patent 4,871,904), etc. For example, if the X and Y axis
scanning motors are both driven such that the light reflectors are driven at a
sinusoidallyvarying rate of speed, then the scan pattern at the reference
plant
S will be a Lissajous-type pattern for omni-directional scanning of the
symbols.
The use of two separate scanning motors and control means to produce the
multi-axis and omni-directional scanning pattern increases material and labor
costs as well as the amount of electtical power needed to operate the scatmer.
In addition, the relatively complicated motor shaft and bea.ring arnangements
of
the scanning components may result in a useful life that is inadequate for
some
applications.
European patent application 456,095 also discloses various prior art
types of high speed scanning arrangements, as do US patents 5,280,165 and
5,367,151.
SUMMARY OF THE RVF' ~~,'~'I'ION=
Objects of the Invention;
It is a general object of the present invention to enhance the state-of the-
art of high speed scanning a=rangements, and particularly although not
exclusively for such arrangernents for use in optical scanners for reading
indicia
of differing light reflectivity, particularly laser scanners for reading bar
code
symbols.
A fu.rther object of the present invention is to provide an inexpensive,
robust and easily replaceable scanning arrangement.
Yet atiother object of the invention is to increase the working lifetime of
the scanning components.
Yet another object is to provide a robust, low cost, hand-held optical
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scanner.
Yet a further object is to provide a means for determining when a scanner
has been exposed to high levels of mechanical shock.
Yet a further object is to attempt to alleviate high levels of mechanical
shock.
According to a first aspect of the invention there is provided a hand-held
electro-optical scanner for reading indicia, comprising: a housing; a scan
assembly
within the housing for scanning an indicium to be read; a detector within the
housing
for detecting light reflected from the indicium being scanned, and for
producing an
electrical signal representative of the indicium; a data transmission coupling
for
transmitting data indicative of the electrical signal away from the housing;
and an
electrically conductive, grounded coating on the coupling for shielding the
coupling
from radio frequency emissions out of the housing.
According to a second aspect of the invention there is provided a hand-held
reader for electro-optically reading indicia, comprising: a gun-shaped housing
having
a hollow, upper body portion extending along a body axis, and a hollow, lower
handle
portion connected to, and extending along a handle axis downwardly away from,
the
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body portion; a generally planar, printed circuit board mounted in the housing
and being
the sole printed circuit board within the housing, the sole board having an
upper region
5 located within the body portion, and a lower region located within the
handle portion, the
sole board extending between the upper and lower regions in a direction
transversely of
the body axis; a light-transmissive window located in the body portion; a scan
module
mounted at the upper region of the sole board, for scanning light passing
through the
window; and a coupler mounted at the lower region of the sole board and being
in
electrical communication with the scan module.
The invention may be carried into practice in a number of ways and
several specific embodiments will now be described, by way of example, with
reference to the accompanying drawings, in which:
BRIEF DESCRIPTION OF THE DRAWINGS:
Figure 1 a is a perspective view of a hand-held optical scanner, suitable
for use with the scanning arrangement of the present invention;
Figure 1 b is a perspective view of a hand-held data-entry/scanning
terminal suitable for use with the scanning arrangement of the present
invention;
Figures 2a and 2b show an embodiment of a scanning arrangement
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according to the present invention;
Figure 3 shows another embodiment;
Figures 4a and 4b are top and side views, respectively, of an alternative
low-cost hand-held scanner;
Figures 5a and 5b are, respectively, views from above and to the side of
the scanning mechanism for use in the embodiment of Figures 4a and 4b;
Figure 6 shows an exemplary PCMCIA card connector, for use with any
of the preceding embodiments;
Figure 7 shows, schematically, an abuse detector for portable electronic
equipment;
Figure 8 is a longitudinal cross-section through the detector of Figure 7;
Figures 9 to 11 are flow diagrams illustrating a method of shock
preparation in portable electronic equipment;
Figure 12 is a partial section through an optics module according to a
further embodiment of the invention;
Figure 13 is a partial view from above of the module of Figure 12;
Figure 14 is a partial view from one end of the module of Figure 12;
Figure 15 is a view from one side of yet a further alternative
embodiment;
.20 Figure 16 shows a further exemplary housing, incorporating an
accelerometer;
Figure 17 shows how the accelerometer signal output is conditioned;
Figure 18 shows the electronic circuitry associated with the embodiment
of Figure 16;
Figure 19 illustrates the operation of the algorithm used in the Figure 16
embodiment;
Figure 20 shows another embodiment of the terminal of Figure lb; and
Figure 21 shows a shock-protected electronic device.
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DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:
Referring now to the drawings, as shown in Figure 1, reference numeral
generally identifies a hand-held scanner having a head 12 and an
5 ergonomically-shaped handle 14. A manually-operable trigger 16 is situated
below the head 12 on an upper, forwardly-facing part of the handle 14. As
known from the above-identified patents incorporated by
reference herein, a light source component, typically, but not necessarily, a
laser, is mounted inside the head 12. The light source emits a light beam
along
10 a transmission path which extends outwardly through a window 18 that faces
indicia, e.g. bar code symbols, to be read. Also mounted within the head is a
photodetector component, e.g. a photodiode, having a field of view, and
operative for collecting reflected light returning through the window 18 along
a
path from the symbol.
A scanner component (to be described in more detail with rreference to
Figure 2) is mounted within the head 12, and is operative for scanning the
symbol andlor the field of view of the photodetector. The scanner component
includes at least one light.reflector positioned in the transmission path
and/or
the return path. The reflector is driven in oscillatory fashion by an
electrically-
operated drive, preferably at the resonant frequency of the scanner component,
thereby producing a scanning light beam.
The photodetector generates an electrical analog signal indicative of the
variable intensity of the reflected light. This analog signal is converted
into a
digital signal by an analog-to-digital converter circuit. This digital signal
is
' conducted to a decode module (not shown) within the scanner. The decode
module decodes the digital signal into data descriptive of the symbol and the
data are passed out along an external cable 20 to an external host device 24,
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normally a host computer. Here the data are stored for further processing.
Instead of the cable 20, the scanner 10 and the external host device 24 may be
in communication by a wireless connection, e.g., a radio link.
In operation, each time a user wishes to have a symbol read, the user
aims the head at the symbol and pulls the trigger 16 to initiate reading of
the
symbol. The trigger 16 is an electrical switch that actuates the drive means.
The symbol is repetitively and rapidly scanned. As soon as the symbol has
been successfully decoded and read, the scanning action is automatically
terminated, thereby enabling the scanner to be directed to the next symbol to
be
read in its respective turn.
In addition, the head need not be a portable hand-held type, as fixedly
mounted heads are also contemplated in this invention. Furthermore, scanners
in accordance with the present invention may have manually operated triggers,
or may alternatively be continuously operated by direct connection to an
electrical source.
The oscillations need only last a second or so, since the multiple
oscillations, rather than time, increase the probability of getting a
successful
decode for a symbol, even a poorly printed one. The resonating reflector has a
predetermined, predictable, known, generally uniform, angular speed for
increased system reliability.
Turning now to Figure lb, there is shown an alternative hand-held
optical scanner, this time taking the form of a scanning terminal 26. The
terminal comprises a hand-held case 28 having a data display screen 30 and a
data input keypad 32. A high speed scanning arrangement within the case 28
produces a scanning light beam which extends outwardly through a window 34
which faces the indicia to be read. Light reflected from the indicia passes
back
through the window 34 and impinges on a photodetector component (not
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shown), for example a photodiode, which creates a returning light output
signal.
The information content within that signal may be stored in an on-board
memory (not shown) or may be downloaded to a remote computer via a data
port 36. Alternatively, the information may be transmitted via a radio
frequency signal produced by an on-board radio transmitter/receiver 38.
Figure 2a shows an embodiment of a high speed scanning arrangement
suitable for use with either of the optical scanners of Figures la and lb. The
arrangement has a flexible beam 50, one end 53 of which is fixedly mounted by
means of a screw 52 to a base support 54. The beam 50 preferably comprises a
generally planar leaf spring, which may be made of Mylar(TI's), a plastics
material, metal, or any other convenient flexible material. At the distal end
55
of the beam 50 is a mounting bracket 56,58 which is secured to the beam by
means of a further screw 60. Secured to one portion 56 of the mounting
bracket is a generally rectangular mirror (62) having a reflective mirror
surface
64. The mirror extends downwardly from the distal end 55 of the beam 50,
generally parallel with the length of the beam, towards the other end of the
beam 53.
Mounted.to the second portion 58 of the mounting bracket, on the other
side of the beam 50 from the mirror, is a permanent magnet 66. This is
positioned generally on an axis 68 of an electromagnetic coil 70, but is
mounted
perpendicular to the axis to save space.
In operation, the coil 70 is driven either with a pulsed electrical signal, or
an AC signal (e.g.,a sine-wave signal), thereby creating a continuous or
repetitive
force on the magnet 66. The force repeatedly moves the magnet into and out of
the coi170, thereby flexing the beam 50 and causing oscillation of the mirror
in
the direction shown by the double-headed arrow 75. Alternatively, the force
may be unidirectional only: for example a repeated pulse may draw the magnet
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into the coil, with the magnet moving in the other direction purely by virtue
of the
resilience of the beam 50. The perpendicular mounting of the magnet 66 means
that it does not protrude beyond the coil 70 when the beam 50 bends to its
fullest
extent.
5 Preferably, the coil 70 is driven so that the scanning arrangement
oscillates at a resonate frequency which is above the fundamental. The
preferred mode of oscillation is a higher order mode, as is shown
schematically
in Figure 2b. In this Figure, the dashed lines 50' represent the rest position
of
the beam 50, and the solid lines represent one of the instantaneous positions
of
10 the beam during oscillation. For the sake of clarity, the mirror and
mounting
bracket are omitted, and the amount of curvature is exaggerated. In this
preferred embodiment, the beam is caused to oscillate in such a way that there
is a fixed node or axis 79 approximately one third of the way along its
length.
The portion of the beam 80 above this point bends as shown, as does the
portion
82 between the axis 79 and the base support 54: however, the node 79 remains
substantially stationary. Other modes of oscillation, other than the
fundamental,
could also be used, depending upon the oscillation frequency required. The
exact frequency will of course depend upon the size and mass of the
components, but in the preferred embodiment the frequency may for example
be between 100 and 200 Hz; or it could be greater than 200 Hz.
By mounting the mirror 62 to the distal end 55 of the beam, and
arranging for it to extend downwardly, parallel to the beam, the mirror center
of
mass 72 may be brought close to the node 79. This allows for high speed
scanning to take place without unduly stressing the beam 50. As will be
appreciated, the mirror 62 is effectively oscillating about a nominal rotation
axis
which is coincident with the node 79. Since the mirror 62 and the magnet 66
are rigidly coupled together, they oscillate as one unit, which simplifies the
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drive signal control.
To further reduce stress on the.beam 50, the mounting bracket 56,58 and
the permanent magnet. 66 are both made relatively small and light in
comparison with the mirror. The fact that the magnet is small, and positioned
far away from the nominal rotation axis 79, allows the coil 70 to provide
enough rotational moment for the start-up time to be extremely rapid (less
than
50 milliseconds).
The relative lengths and masses of the beam 50 and the mirror 62 may be
adjusted, as will be evident to the skilled man in the art, to provide the
required
frequency of oscillation. If necessary, additional weights 74 may be secured
to
the mirror, thereby bringing the overall center of mass 72 close to the
nominal
axis of rotation.
In alternative embodiments (not shown) the mirror 64 could be replaced
with any other suitable optical arrangement for diverting a light beam. For
example, instead of the light beam being reflected from the mirror surface 62,
it
could instead be diverted by passing through a lens, a prism, a diffraction
grating, or a holographic optical element. Also, the mirror 62 could be
replaced
with a solid state laser, the scanning motion of the beam being caused by
oscillation of the laser itself.
This last arrangement is shown schematically in Figure 3, in which like
elements are given like reference numerals. In this embodiment, the mirror 62
is replaced with a solid state laser 162 which is mounted to the mounting
bracket 56 by a rigid elongate support 164, extending longitudinally of the
beam.50. The laser 162 includes beam-shaping optics and a stop 166, and
produces an output beam 163. In use, as the beam 50 oscillates (as shown
schematically in Figure 2b) the laser 162 also oscillates, thereby causing a
scanning motion of the laser beam 163. The scanning frequency may be high
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(for example betwoen 100 and 200 Hz).because of the close proximity of the
nominal axis of rotation (the node 79) and the center of mass 168 of the laser
162. Preferably, the support 164 is light but rigid so that it does not affect
substantially the position of the center of mass of the support/laser
assembly.
The embodiment of Figure 3 may be used in combination with the
embodiment of Figure 2a, in optical series, to provide the capability of two
dimensional scanning. Alternatively, the embodiment of Figure 3 may be used
in conjunction with any other known method of one dimensional scanning.
Also, two high speed scanning arrangements of Figure 2 may be used
together, in optical sequence, to create a beam which scans in more than one
direction. In that way, high speed multi-axis scan patterns may be produced
across the indicia to be read. Alternatively, the high speed scanning
arrangement of Figure 2 may be used in association with other known (one-
dimensional) scanning arrangements to produce a similar effect.
In either arrangement, the drive signal applied to the coil 70 preferably
causes continued oscillation at the required frequency. Alternatively,
however,
a single pulse or drive signal could be applied to the coil, simply starting
the
oscillation off, with the scan element then coming naturally to rest in a
damped
manner.
Either of the embodiments of Figures 2 or 3 may be manufactured as a
self-contained scan module or element which may be mounted as a unit within
any type of hand-held or fixed optical scanner, for example those shown in
Figures 1 a or 1 b. In such a modular scanning arrangement, the base support
54
may comprise part of the optical scanner casing, as shown for example at
reference numeral 12 in Figure la or reference numeral 28 in Figure lb. In
such an arrangement, the coil 70 may also be directly mounted to the casing
(with the coil therefore not forming part of the replaceable module).
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Alternatively, the base support 54 of Figures 2 and 3 may comprise a common
mounting bracket to which is secured"not only the beam 50 , but also the coil
70. In that arrangement, the coil 70 forms part of the replaceable module, and
is secured to the casing along with the other scanning components via the
intermediary of the support bracket 54.
Figures 4a and 4b show respectively top and side views of a low cost
housing within which the previously described scanning arrangements may be
incorporated.
The housing of Figure 4 comprises a head portion 200 and a manually-
graspable handle portion 202 having a trigger 204 which can be operated by the
user's finger. A scanning mechanism generally indicated at 206 is located in
the head portion, and provides a scanning laser beam indicated by the dotted
lines 208 which leaves the scanner via a window 210.
The scanning mechanism 206 is surface-mounted to an elongate printed
circuit board (PCB) 212 which extends downwardly into the handle. Power
and/data transfer capabilities are provided via an external lead 214 which
couples to the PCB via a suitable power and/data transfer coupling 216 at the
lower end of the board. The trigger 204 has, within the handle, an elongate
metal tongue 218 which, when the trigger is pressed, applies force to an
ON/OFF micro-switch 220 on the PCB.
The PCB may, in addition, include decode electronics 222 providing for
in-housing decoding of bar code symbols or other indicia which are being read
by the scanner.
Preferably, all of the mechanical and/or electronic components within the
housing, apart from those associated with the trigger 204 and the tongue 218,
are surface mounted to the PCB. The PCB is then simply secured to the
housing by screws or other appropriate couplings 224,226.
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Instead of or in addition to the data cable 214, the scanner may be
provided with a radio communications link 300. In such a case, power may be
provided not via an external lead but rather by an on-board battery pack 302.
In one preferred embodiment, the scanning mechanism 206 may be of
the type shown in Figure 2a or of the type shown in Figure 3. In an
alternative
embodiment, the mechanism may be of the type now to be described with
reference to Figure 5a.
In Figure 5a, the scanning mechanism 206' includes a laser diode 230 that
produces an outgoing laser beam which is reflected from a collection mirror
232
onto an oscillating scanning mirror 234 to produce an outgoing scanning beam
236. Light reflected from the indicia (not shown) being scanned impinges first
on
the scanning mirror 234, then on the collection mirror 232 from which it is
reflected to a photodiode or other photodetector 238. The photodetector
produces
an electrical output signal which travels via the PCB to the PCB electronics
222
(Figure 4b).
The scanning mirror 234 is caused to oscillate back and forth about an
axis 240 by means of a drive signal applied to a coil 242. This interacts with
a
magnet 244 on a rotating member 246 to which the mirror 234 is also secured.
As best shown in Figure 5b, the scanning mechanism is secured to the
PCB 212 by means of an angled mounting bracket 250. A flange 252 of the
mounting bracket is secured to the PCB by one or more screws 254.
An alternative module design is shown in Figures 12 to 14. In this
design, a small optics module carries the mechanical and optical elements,
with
the majority of the electronics being located elsewhere. In the preferred
embodiment, the optics module has an electrical connector for connection to a
printed circuit board (PCB) which carries the electronic components such as
the
laser drive, the motor drive, the digitizer and the decoder.
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Figures 12 to 14 show an exemplary design in which the optics module
generally indicated at 950 comprises a variety of optical and mechanical
components mounted to a base 952. Electrical connections 953 are provided
for coupling the module to a PCB 954.
5 On the module base 952 is mounted a semiconductor laser 962 the output
beam 963 of which passes through a focusing lens 964 before being internally
reflected by a prism 966. The beam then passes through an aperture 968 in a
collector 970 before impinging upon an oscillating scanning mirror 956 to
provide an outgoing scanning laser beam 972. The scanning mirror 956 is
10 arranged to oscillate over an angle of about 28 .. by virtue of the
interaction
between a fixed magnet 958 and an electro-magnet coil 960. Light 974,
reflected from the indicia, impinges back onto the scanning mirror 956 and
onto
the collector 970 which focuses it via an aperture 976 in a housing 978 to a
photodetector 980.
15 Electrical connections, schematically illustrated at 953, 953' and 953",
couple the optics module 950 to the PCB 954. The connections may include
power connections, ground connections, signal/control connections,. and drive
connections for the coil 960 and the laser 962. Signal connections are also
provided enabling the output from the photodetector 980 to be passed to the
PCB 954.
On the PCB 954 are mounted the electronic circuits' 982 for operating the
optics module 950. These may include, for cxample, the laser driver, the motor
drive, the digitizer and the decoder.
Such an arrangement provides for an efficient and convenient
manufacturing operation.
An alternative optics module is shown schematically in Figure 15. In
this arrangement, outgoing laser light from a semiconductor laser 600 passes
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through a focusing, lens 602, an aperture 604 in a collecting minor 606 and
impinges upon*the scanning mirror 668 to form an outgoing scanning beam
610. The scanning mirror 608 is mounted on a Mylar strip 612, and is caused
to oscillate by virtue of the interaction between a permanent magnet 614 and
an
electromagnetic driving coil 616.
Reflected light 618 from the indicia (not shown) being read first
impinges once more onto the scanning mirror 608, and is then focused by
means of the concave collection mirror 606 onto a filter 620 and photodetector
622 assembly.
The optical elements are mounted to a base 624 which carries an
electrical connector 626 via which electrical signals can be transferred to
and
from the module. In particular, the connector 626 may carry power, ground
lines, control signals, drive signals for the coi1616 and (via the additional
coupling 628) for the laser 600. In addition, the connector 626 may include
data lines for transferring from the module data signals representative of
light
received by the photodetector 622.
The base 624 may further include one or more application-specific
integrated circuits 630.
In the embodiments of Figures 12 and 15, the modules may optionally
include some or all of the required electronic components such as a digitizer
and/or a decoder. In such a case, the module is self-contained and simply
plugs
into a generic PCB. The generic PCB then need not carry decode or digitizing
circuitry.
In any of the preceding embodiments, the data and/or other connections
may be made by way of a standard PCMCIA card connector, if desired. For
example, in the embodiment of Figure 4, the data lead 214 may be coupled to
the PCB 212 via a PCMCIA card-type connector. Alternatively, the radio
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frequency transmitter 300 may also be cpupled via this type of connector.
Where a PCMCIA card connector is used, the preferred arrangement is
as shown in Figure 6. In order to prevent radio frequency leakage from a
PCMCIA package, the plastic PCMCIA connector is selectively coated with an
appropriate conductive material such as silver, copper, nickel or gold ink or
paint. Other conductive coatings could of course be envisaged such as, for
example, the coating supplied by Acheson Colloids Company of Ontario,
Canada, under product reference Electrodag 18DB70.
The coating covers the upper surface 410 of the connector, the lower
surface 412 and the front surface 414. The coating at least partially
continues
inside some of the cavities, to make an electrical connection between the
exterior coating and ground. According to the PCMCIA standard, socket
positions 1, 34, 35 and 68 are grounded and the coating may extend into, and
make electrical contact with ground within, any or all of these sockets.
In addition, coating is provided within the other contact load positions,
but no electrical connection is made to the grounded exterior shell coating.
The electrically conductive coating is, in addition, in electrical contact
with the PCMCIA top and bottom covers (not shown).
When used with a standard metal card frame assembly, this embodiment
ensures substantial sealing of RF leakage out of the PCMCIA assembly.
The embodiment of Figures 4a and 4b may include an abuse-detector
generally indicated by reference numeral 700, and illustrated in more detail
in
Figures 7 and 8 to which reference should now be made.
The abuse detector 700 comprises a molded plastics material ring 702,
having inwardly-directed spokes 704 which support a central weight 706. The
ring 702, the spokes 704 and the weight 706 may be all of one piece, as is
illustrated in Figure 8 which is a longitudinal cross-section along the
central line
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of one of the spokes. Each spoke 704 is coated with a stress-sensitive coating
708. The unit is secured to a suitable support within the scanner, for example
the PCB 212 in Figure 4b, by means of an annular adhesive coating 708 applied
to one side of the ring 702.
The coating 708 is chosen so that it visibly cracks when the equipment is
subjected to a level of acceleration that exceeds the specified limits of
use(e.g.,
2000g). This occurs by the twisting or longitudinal bending of the spokes 704
as the weight 706 moves slightly with respect to the ring 702. It will be
noted
from Figure 8 that in the preferred embodiment the weight 706 is spaced
slightly forwardly of the PCB, by virtue of a rearwardly-extending annular
boss
on the ring 702, thereby enabling the weight to move freely as the spokes bend
and/or twist.
In an alternative embodiment (not shown) the ring 702 may be secured to
a circular base, which may itself be attached, for example by means of an
adhesive, to the PCB 212.
An abuse meter of the type illustrated in Figures 7 and 8 may be applied
to any type of hand-held equipment, not only bar code, readers. It may have
particular application to. hand-held computer terminals and like equipment
which may, in a busy industrial or commercial environment, be liable to
sustain
accidental shocks.
A rather more sophisticated approach to the problems of unexpected
shock is illustrated in Figures 9 to 11. This proceeds from the recognition
that
although sudden shock, due for example to banging or dropping the device, may
not cause permanent damage, it can cause interruption of the operation of the
electrical process/software within. Such electronic interruptions may cause
data and/or software program loss that may not be easily recoverable.
Accordingly, the embodiment of Figure 4b includes an accelerometer with
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associated circuitry 800 for sensing sudden acceleration of the device and for
automatically causing the computer to pause or to shut down the current
process
before the possible shock causes loss of data and/or disruption of that
process.
A suitable accelerometer for use in all types of hand-held or portable
computer
peripherals is the Model 3031 accelerometer supplied by IC Sensors of
Milpitas, California.
In operation, the accelerometer is designed to detect sudden
accelerations, for example that caused when the device is dropped, and to
alert
the central processing unit (CPU) accordingly. The computer is therefore
warned of a possible imminent shock, allowing all current processing to be
frozen and for the electronics to be shut down before the shock occurs. At the
time of the shock, no processing will be in progress, and hence no electronic
information will be lost due to the shock. Of course, this does not preclude
loss
of capability of the device due to actual physical damage.
Upon indication that the device is accelerating, the CPU is arranged to
enter a low-power "pause" mode in which the current processes, and the status
conditions, are saved. After the impact, the user may reactivate the system
and
can continue the processing, from the point at which it was shut down, without
loss of data.
Shock prediction may also be used to protect physical components from
damage due to a sudden shock. Once the computer has been warned of the
high acceleration rate, it may actuate electro-mechanical devices to provide
additional mechanical protection. For example, a miniature disk drive can be
locked before impact to provide additional protection to the drive head and
platters.
It will be understood that acceleration-detection in three dimensions will
typically be preferred, since the impact may occur at any angle. However, one-
CA 02619584 2008-02-15
dimensional acceleration sensing could suffice if, in a particular
application,
protection from shock is needed only-in a particular direction.
Figure 9 shows the alerting algorithm in more detail. Starting at 910,
acceleration of the device is continually monitored at 912 by the
accelerometer
5 800 (Figure 4b). When the accelerometer determines at step 914 that a
thres-hold is exceeded, an alert is sent at 916 to the CPU, for appropriate
action
to be taken. The accelerometer then continues to monitor the acceleration
level, so that it can signal a return to normal conditions. If the limit was
not
exceeded at step 9 14, monitoring simply continues.
10 Figure 10 shows the flow of the CPU response to an acceleration alert.
Starting at 920, the CPU first, at step 922, sends a message to actuate any
electro-mechanical locking devices to prepare for the shock. At 924 the CPU
then stops all current running programs, and saves the status information of
those processes. Finally, at 926, the CPU puts the computer into a power-down
15 or "sleep" mode.
The recovery from a power-down event caused by an acceleration alert is
illustrated schematically in Figure 11. Starting at 930, when the user wakes
up
the unit (via a keystroke or other input), the CPU then checks at 932 to see
whether the power-down mode it is coming out of was due to an acceleration
20 alert. If not, control then passes at 933 to the normal wake-up routine.
If the power-down was caused by an acceleration alert, the CPU informs
the user at 934 that it experienced an acceleration shutdown. The system then
asks whether the user wishes to continue the application from the point at
which
it was paused. The user's input is checked at 936, and if the user has decided
not to continue from the point at which the process was paused, a top level
routine 937 may then be initiated. On the other hand, if the user does decide
to
continue the application from the paused point, the electro-mechanical locks
are
CA 02619584 2008-02-15
21
removed at 938, and at 940 the procesS status information is re-installed and
the
application continued from the appropriate point.
An alternative and yet more sophisticated approach is illustrated in
Figures 16 to 19. Figure 16 shows a hand-held scanner body 1610 having a
head portion 1620 and a manually-graspable handle portion 1630. The
internal scanning components (not shown) are actuated by means of a digitally-
operated trigger 1640.
Mounted within the handle 1630 is a printed circuit board 1650 which is
coupled by means of a flexible electrical connection 1660 to x, y and z
accelerometers 1670, fixedly secured to the housing.
The PCB 1650 mounts electronic components, shown in Figures 17 and
18, for processing the signals received from the accelerometers 1670.
Figure 17 illustrates the signal processing for the x-channel. An
acceleration a,t applied to the accelerometer 1670x produces a raw output
signal
1708x on the accelerometer output 1710x. This signal is applied to an x-filter
1712x which produces a smoothed output 1714x on the filter output 1716x.
They and z channels are identical.
The three channels already described in connection with Figure 17, may
be seen on the left-hand side of Figure 18. As shown in that drawing, the
filter
output for each channel is applied to one input of a comparator 1802. The
other
input, in each case, is a fixed voltage 1804 representative of an acceleration
of
200g. The respective comparator outputs 1806 are then applied to three
respective inputs of a central OR-gate 1810. This accordingly creates a wake-
up signal on an output 1812 when any one or more of the comparators 1804
have registered an acceleration in excess of 200g. The wake-up signal on the
line 1812 is placed on a bus 1814 which supplies the information respectively
to
x, y and z microprocessors 1816. Analog signals are also supplied to the
CA 02619584 2008-02-15
22
respective microprocessors from the output of the x, y and z filters 1712.
Each
microprocessor has associated with it a corresponding memory 1818. The
memories are coupled with a further bus 1820 to a common output port or data
coupling 1822, whereby the information in the memories.1818 may be
downloaded to a fixed central computer (not shown).
In operation, the individual outputs of the accelerometers are constantly
monitored, and a "wake-up" signal is supplied on the line 1812 if any one or
more of the accelerometers records an acceleration of greater than 200g. In
that
event, data representative of the filter outputs are supplied to the
respective
microprocessors, and may be stored in the memories for further study or
processing. The precise waveform which has triggered the "wake-up" signal
on the line 1812 may still be recovered and stored in memory by virtue of its
having been delayed in transit by a delay element 1824. The respective x, y
and z delay elements may comprise standard delay lines, or may, more
preferably, comprise EEPROMs, arranged to store the incoming signals on a
temporary basis, and to pass them on if and only if a "wake-up" signal is
generated. For example, each EEPROM may store waveforms relating to the
most recent five second period, with previous time periods being constantly
overwritten unless and until a "wake-up" signal is generated, in which case
the
waveforms are passed on to the microprocessors 1816. In. an alternative
embodiment (not shown) the EEPROMs may comprise part of the respective
microprocessors 1816.
In a further development of the idea, additional sensors 1826 may be
provided, for each channel, to supply additional information that may be
useful
to assist in the analysis of the waveforms. For example, it may under some
circumstances be advantageous to retain information relating to the raw (pre-
filtered) signals, and/or the x, y, z attitude of the equipment, over a period
of
CA 02619584 2008-02-15
23
time.
In addition, or alternatively, a fiirther channel (not shown) may be
provided for the storage of additional information such as the ambient
temperature, the temperature of the laser diode, the on/off state of the
scanner,
the frequency/duration of use, or the state of various electronic or
mechanical
components. With this additional information, the device effectively acts as a
"black-box" for an optical scanner, or other electronic equipment, allowing
the
manufacturer or other testing personnel access to a complete device log. If a
user reports that a particular scanner has stopped working, or has developed a
malfunction, it is then an easy matter to download the log via the connector
1822, and to investigate the device's recent history. It may for example may
become evident from the log that the device has been subject to abusive
treatment which has not been reported by the user.
Turning now to Figure 19, there is shown a preferred mode of operation,
which differs slightly from that already discussed in connection with Figure
18,
in that the entire waveform is loaded into memory only if a deceleration of
greater than 500g has been detected; if the detected deceleration is between
200
and 500g, the system simply makes a note of that fact.
At step 1910, the algorithm is launched as the scanner is powered up. If
the user wishes to upload the information stored in the memories, he requests
an
upload at step 1914, and the upload is effected at 1916. In this diagram, "EE'
represents an erasable EPROM.
If an upload has not been requested, the system goes into a suspended
mode at 1918. It remains in that mode until a "wake-up" signal is supplied at
1920, this telling the system that at least one accelerometer has detected a
deceleration of greater than 200g (compare the "wake-up" signal on the line
1812 of Figure 18).
CA 02619584 2008-02-15
24
At step 1922, an A/D converter is initialized, the corresponding
waveform sampled at 100 sampling points, and the digital values stored in
RAM. A check is then made at 1924 to see whether any of these samples are
representative of decelerations greater than 500g. If not, then control passes
to
box 1926. The current value of the counter representing decelerations of
between 200 and 500g is read, the value is incremented, and the new value is
then stored in EE. Control then passes back to box 1918, to await a further
"wake-up" signal.
If any samples of greater than 500g are found at step 1924, control passes
the box 1928. The entire digitized sample is then stored in EE, and the
pointers
updated, allowing the waveform to be reconstructed at a later stage. Other
relevant information may then be stored, at 1930, such as for example the
temperature. Control then returns to box 1918 and further activity is
suspended
until another "wake-up" signal is detected.
It will of course be appreciated that the equipment and processes
described above, and illustrated in Figures 9 to 11 and 16 to 19 may find
application in many types of portable equipment, not only bar code readers.
Other applications include portable hand-held and notebook computers,
computer terminals and other electronic equipment.
Figure 20 depicts a terminal anaiogous to the one shown in Figure lb in that
it has a display 30 and a keypad 32. However, the window is not located at the
front, but instead a window 210 is located on a bottom wall 211. The scan
module
or engine 206 is mounted on the PCB 212 such that the outgoing laser scan beam
exits the housing at an acute angle on the order of 30 relative to the
horizontal.
The scan beam is not perpendicular or parallel to any outer wall of the
terminal, or
to the PCB 212.
Since hand-held electronic devices are subject to a considerable amount of
mechanical stress due to dropping to hard surfaces, etc., it is important that
the
CA 02619584 2008-02-15
housing be desigited in a durable manner. Another feature of the present
invention, as shown in Figure 21, is to provide an external housing of ahand
held
device such as a lap top computer, a bar code reaader, etc., comprised of
three
distinctsections or components, namely an upper housing 11, a middle housing
13,
5 and a lower housing 15, although such sections may be any three (or more)
segments or regions of the housing. The upper housing and the lower housing
are
made of a relatively rigid thermoplastic such as ABS/PC while the middle
housing
which separates the upper housing and lower housing, is preferably made from a
"semi-rigid" thermoplastic elastometer such as Texin (Texin is a trademark
of
10 Miles Inc., of Pittsburgh, Pennsylvania, relating to a family of urathane
thermo
plastic materials). We use the term "semi-rigid" to describe Texin as a
material
that is a cross between an elastometer, with the properties of high strain and
low
set and a standard theremoplastic, with the properties of high. rigidity and
brittleness.
15 The shape and design of the housing is such that the middle housing
is the first point of contact on a side load that might typically occur when
the
reader is dropped. This portion of the housing, when made from Texin, is
capable
of sustaining relatively large strains without experiencing permanent
deformation.
The large deflection serves to gradually slow down the impact against
sensitive
20 internal components, hence, reducing the shock load, much the same way that
an
internal shock mounting system such as rubber bumpers, would.
The housing can easily be designed to allow the energy absorbent
properties of the middle housing to work for a load directed onto the upper
housing
and a soft boot or "foot" typical of the handle portion of a gun-shaped bar
code
25 reader, would be needed for a bottom load. Another important difference in
this
design is that the optical assembly can be rigidly mounted to the lower
housing for
CA 02619584 2008-02-15
26
accurate mechanical registration. This reduces the likelihood of the common
problem of alignment of a "soft mounted" or suspending optical assembly to the
housing. An additional benefit is the fact that the Texin material has enough
compressibility to provide a moisture and dust proof seal when fastened snugly
to
the other portions of the housing. Thus, if sealing is desired, the need for a
separate gasket is eliminated.
It will be understood that each of the elements described above, or two or
more together, may also find useful applications in other types of
constructions
which differ from those specifically desccribed above. Elements described in
connection with one embodiment may, where compatible, be combined with those
described in connection with another embodiment.
While the invention has been illustrated and described as embodied in a
high speed scanning arrangement, it is not intended to be limited to the
details
shown, since various modifications and structural changes may be made without
departing in any way from the spirit or scope of the present invention.
Without further analysis, the foregoing will so fully reveal the gist of the
present invention that others can, by applying current knowledge, readily
adapt it
for various applications without omitting features that, from the standpoint
of prior
art, fairly constitute essential characteristics of the generic or specific
aspects of
this invention and, therefore, such adaptations should and are intended to be
comprehended within the meaning and range of equivalence of the appended
claims.
