U.S. patent application number 09/897175 was filed with the patent office on 2001-11-29 for bar code scanner with collimated scan volume.
Invention is credited to Knowles, Carl H., Rockstein, George B., Schmidt, Mark C., Wilz, David M. SR..
Application Number | 20010045465 09/897175 |
Document ID | / |
Family ID | 27583795 |
Filed Date | 2001-11-29 |
United States Patent
Application |
20010045465 |
Kind Code |
A1 |
Schmidt, Mark C. ; et
al. |
November 29, 2001 |
Bar code scanner with collimated scan volume
Abstract
An optical scanner comprising an automatic (i.e., triggerless)
portable bar code symbol reading device with an omnidirectional
scanning engine mounted within the head portion of its housing, and
adapted for use with an associated base unit. The bar code symbol
reading device produces a confined scanning volume for
omnidirectional scanning of code symbols presented therein, while
preventing unintentional scanning of code symbols on nearby objects
located outside of the confined scanning volume.
Inventors: |
Schmidt, Mark C.;
(Blackwood, NJ) ; Knowles, Carl H.; (Moorestown,
NJ) ; Wilz, David M. SR.; (Sewell, NJ) ;
Rockstein, George B.; (Audubon, NJ) |
Correspondence
Address: |
Steven R. Bartholomew, Esq.
41st Floor
60 East 42nd Street
New York
NY
10165
US
|
Family ID: |
27583795 |
Appl. No.: |
09/897175 |
Filed: |
July 2, 2001 |
Related U.S. Patent Documents
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Application
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Filing Date |
Patent Number |
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09897175 |
Jul 2, 2001 |
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09626841 |
Jul 27, 2000 |
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6299067 |
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09626841 |
Jul 27, 2000 |
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09444587 |
Nov 22, 1999 |
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6182898 |
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09444587 |
Nov 22, 1999 |
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09204176 |
Dec 3, 1998 |
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6283375 |
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09204176 |
Dec 3, 1998 |
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08645335 |
May 13, 1996 |
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May 13, 1996 |
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Mar 12, 1996 |
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Dec 18, 1995 |
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Aug 17, 1994 |
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Aug 17, 1994 |
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08365193 |
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5557093 |
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08365193 |
Dec 28, 1994 |
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Aug 19, 1994 |
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Nov 17, 1995 |
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08278109 |
Nov 24, 1993 |
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5484992 |
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08278109 |
Nov 24, 1993 |
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08489305 |
Jun 9, 1995 |
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08489305 |
Jun 9, 1995 |
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08476069 |
Jun 7, 1995 |
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5591953 |
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08584135 |
Jan 11, 1996 |
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Current U.S.
Class: |
235/462.45 |
Current CPC
Class: |
G06K 7/10801 20130101;
G06K 2207/1017 20130101; G06K 7/10594 20130101; A61K 39/00
20130101; G06K 7/10871 20130101; G07G 1/0045 20130101; A61K 38/00
20130101; G02B 26/106 20130101; G06K 7/10584 20130101; G02B 26/10
20130101; G06K 7/109 20130101; G06K 7/10861 20130101; G06K
2207/1013 20130101; G06K 7/10603 20130101; G06K 7/10891 20130101;
G06K 7/10673 20130101; G06K 7/10 20130101; G06K 7/10851 20130101;
G06K 7/10693 20130101; G06K 17/0022 20130101; G06K 7/10702
20130101; G06K 7/1443 20130101; G06K 7/10792 20130101; C07K 14/205
20130101; G06K 7/10564 20130101; G06K 7/10811 20130101; G06K
7/10881 20130101; G06K 7/10663 20130101; G06K 2207/1012 20130101;
G06K 7/14 20130101; G07F 9/002 20200501 |
Class at
Publication: |
235/462.45 |
International
Class: |
G06K 007/10 |
Claims
What is claimed is:
1. An optical scanner comprising: (a) a housing having an optically
admissive window through which optical energy of at least one
wavelength can exit said housing, travel towards an object bearing
a code symbol and reflect therefrom, at least a portion of the
reflected optical energy travelling back through the optically
admissive window to enter the housing; wherein the housing has a
central reference axis extending approximately upwards and
downwards in a longitudinal direction; (b) an optical energy
producing mechanism disposed within the housing for producing a
beam of optical energy; (c) a beam sweeping mechanism mounted
within the housing with respect to the central reference axis for
rotation about a rotational axis intersecting the central reference
axis, where the intersection of the rotational axis and the central
reference axis defines a central reference plane; the beam sweeping
mechanism including a plurality of rotating light reflective
surfaces each being disposed at a different acute angle with
respect to the rotational axis, for sequentially sweeping the beam
about the rotational axis along a plurality of different paths; (d)
a stationary array including a plurality of stationary optically
reflective surfaces mounted within the housing with respect to the
central reference axis and disposed substantially underneath said
optically admissive window; wherein at least two of the plurality
of said stationary optically reflective surfaces are substantially
symmetrically disposed on opposite sides of the central reference
plane, and closely adjacent to the beam sweeping mechanism; (e) an
optical energy collection subsystem disposed within the housing,
and including (1) an optical collection element, mounted along the
central reference plane and adjacent at least two of the stationary
optically reflective surfaces, for allowing the beam produced by
the optical energy producing mechanism to pass along a portion of
the central reference plane, to the beam sweeping mechanism, for
sweeping about the rotational axis thereof along the plurality of
different paths, and (2) an optical receiver for receiving optical
energy from the optical collection element at a point substantially
within the central reference plane, detecting the received optical
energy and producing an electrical signal indicative of said
detected optical energy; (f) a signal processor for processing the
electrical signal and producing scan data representative of a
scanned code symbol; (g) a control mechanism for controlling the
operation of the scanner so that, during scanner operation, the
beam produced by the optical energy producing mechanism passes
along a portion of the central reference plane, to at least one of
the rotating optically reflective surfaces of the beam sweeping
mechanism, and as the beam sequentially reflects off a plurality of
the rotating light reflective surfaces, the beam is repeatedly
swept across a plurality of the stationary light reflective
surfaces, thereby producing a plurality of groups of plural scan
lines, respectively, which are projected out through the optically
admissive window and intersect about a projection axis within a
collimated scanning volume having an approximately columnar extent
and extending from adjacent the optically admissive window to at
least about six inches therefrom so as to produce a collimated
projected scanning pattern; and (h) the housing being supportable
relative to an object bearing a code symbol so that when a code
symbol is presented within the collimated scanning volume, (i) the
code symbol is scanned omnidirectionally by the collimated scanning
pattern, (ii) at least a portion of the optical energy reflected
from the scanned code symbol is directed through the optically
admissive window, reflected off at least one of the stationary
optically reflective surfaces, and then reflected off at least one
of the rotating optically reflective surfaces of the beam sweeping
mechanism, and (iii) thereafter, the reflected optical energy is
collected by the optical collection element, and received by the
optical receiver for detection, whereupon the electrical signal is
produced for processing by the signal processor; wherein the
housing permits a user to control the direction of the projection
axis so as to align the collimated scanning volume with the bar
code symbol on the object to be scanned.
2. The scanner of claim 1, wherein the signal processor further
comprises a data processor for decoding the scan data and producing
data representative of the scanned code symbol.
3. The scanner of claim 1, wherein said different acute angles are
selected so that the scan lines in each said group of scan lines
are substantially equidistant from each other throughout at least a
range of distances from the optically admissive window.
4. The scanner of claim 1, wherein the optical energy producing
mechanism comprises a laser diode mounted with respect to the
central reference axis.
5. The scanner of claim 1, wherein said first, second, third, and
fourth stationary light reflective surfaces comprise first, second,
third, and fourth mirrors, respectively.
6. The scanner of claim 1, wherein the housing includes a head
portion and handle portion extending from the head portion, and the
optically admissive window is disposed within the head portion.
7. The scanner of claim 1, wherein the collimated scanning pattern
is oriented along a longitudinal extent of the housing so as to
facilitate scanning of code symbols presented to the collimated
scanning volume.
8. The scanner of claim 1, further comprising a scanner support
stand positionable upon a counter surface, and including a
supporting mechanism for supporting the housing in any one of a
plurality of positions above a counter surface so that the
collimated scanning pattern is projected about the projection axis
above the counter surface in any one of a plurality of orientations
corresponding to the plurality of positions.
9. The scanner of claim 1, further comprising an optical bench
mounted along the central reference axis, wherein the optical bench
includes a shock-mounted support structure upon which the
stationary optically reflective surfaces are mounted.
10. The scanner of claim 1, wherein the optical receiver comprises
a photodetector.
11. The scanner of claim 10, wherein the photodetector is located
on a circuit board, at a height above the beam sweeping mechanism,
substantially within the central reference plane.
12. The scanner of claim 1, wherein said code symbol is a bar code
symbol.
13. The scanner of claim 1, wherein the optical collecting element
is a light collecting mirror having a focal distance, substantially
at which said optical receiver is located.
14. The scanner of claim 1, wherein each scan line in a first group
of scan lines is substantially parallel to each other scan line in
said first group of scan lines, and each scan line in a second
group of scan lines is substantially parallel to each other scan
line in said second group of scan lines.
15. An automatic optical scanning system comprising: a housing
having an optically admissive aperture through which optical energy
of at least one wavelength can exit and enter into the housing; an
object detector in the housing, for detecting an object located in
a scanning volume extending externally from the housing, and
automatically generating an activation signal in response to the
detection of the object located therein; an activatable scan data
reading mechanism in the housing, for reading scan data from a
detected object located in the scanning volume, the scan data
reading mechanism including: an optical beam generator for
generating a beam of optical energy and directing the beam through
the optically admissive aperture and into the scanning volume, a
beam scanner for repeatedly scanning the beam so as to produce a
collimated scanning pattern of approximately columnar extent within
the scanning volume, for scanning a code symbol on the detected
object presented therein, an optical detector for detecting optical
energy reflected off the bar code symbol and passing through the
optically admissive aperture as the beam is repeatedly scanned
within the scanning volume, and a receiver for automatically
producing scan data indicative of the detected optical energy; an
activatable scan data processor for processing produced scan data
so as to detect and decode said bar code symbol on the detected
object, and automatically producing symbol character data
representative of the decoded bar code symbol; and a control
mechanism for controlling the operation of the automatic bar code
symbol reading system; wherein the housing permits the user to
control the direction of the projection axis to align said
approximately columnar scanning volume with the bar code symbol on
the object to be scanned.
16. The scanning system of claim 15, wherein the optical beam
generator comprises a laser diode.
17. The scanning system of claim 15, wherein the bar code symbol
has first and second envelope borders, and wherein said scan data
processor comprises a detector adapted to detect the first and
second envelope borders of said bar code symbol, and a mechanism
for decoding said detected bar code symbol.
18. The scanning system of claim 15, wherein the object detector
comprises a receiver for receiving optical energy reflected from an
object within an object detection field defined external to the
housing and having an essentially volumetric extent, and wherein
the collimated scanning pattern is characterized by at least one
scanning plane having an essentially planar extent, and wherein the
object detection field spatially encompasses at least a portion of
the collimated scanning pattern.
19. The laser scanning system of claim 15, wherein the optical beam
generator is operated in a pulsed mode so as to generate a pulsed
beam, which is directed through the optically admissive aperture
and repeatedly scanned across the collimated scanning pattern and
the bar code symbol on the detected object.
20. The scanning system of claim 19, wherein the object detector
includes a transmitter for transmitting a pulsed signal through a
first optical element and into the scanning volume, a signal
receiver for receiving the transmitted pulse signal reflected off
the object in the scanning volume, and a signal comparator for
comparing the received pulse signal with the transmitted pulse
signal and automatically generating an activation signal indicative
of the presence of the object in the scanning volume.
21. The scanning system of claim 15, wherein the housing comprises
a head portion and a handle portion, and wherein the object
detector and the activatable scan data processor are located in the
head portion.
22. The scanning system of claim 20, wherein the transmitter
comprises an infra-red light source in the housing for producing an
infra-red light pulse which is transmitted through the first
optical element into the scanning volume, and wherein the receiver
comprises an infra-red light detector and a second optical element
for focusing reflected infra-red light pulses onto the infrared
light detector.
23. A scanner comprising: (a) a housing having an optically
admissive window through which optical energy of at least one
wavelength can exit said hand-supportable housing, travel towards
an object bearing a code symbol and reflect therefrom, and at least
a portion of the reflected optical energy travelling back through
the optically admissive window to enter the housing; at least some
of the exited optical energy and at least some of the reflected
optical energy traveling approximately in a longitudinal direction
extending along a central reference axis; (b) an optical energy
beam producing mechanism disposed within the housing for producing
a beam of optical energy; (c) a beam sweeping mechanism mounted
within the housing for rotation about a rotational axis
intersecting the central reference axis, where the intersection of
the rotational axis and the central reference axis defines a
central reference plane; the beam sweeping mechanism having a
plurality of rotating optically reflective surfaces each being
disposed at a different acute angle with respect to the rotational
axis, for sequentially sweeping the beam about the rotational axis
along a plurality of different paths; (d) a stationary array
comprised of a plurality of stationary optically reflective
surfaces mounted within the housing; wherein at least two of the
plurality of the stationary optically reflective surfaces are
symmetrically disposed on opposite sides of the central reference
plane, and adjacent to the beam sweeping mechanism; (e) an optical
energy collection mechanism disposed within the housing, and
including (1) an optical collection element, mounted along the
central reference plane and adjacent at least two of the stationary
optically reflective surfaces, for allowing the beam produced from
the beam producing mechanism to pass along a portion of the central
reference plane, to the beam sweeping mechanism, for sweeping about
the rotational axis thereof along the plurality of different paths,
and (2) an optical receiver for receiving optical energy from the
optical collection element at a point substantially within the
central reference plane, and detecting the received optical energy
and producing an electrical signal indicative of the detected
optical energy; (f) a signal processor for processing the
electrical signal and producing scan data representative of a
scanned code symbol; and (g) a control mechanism for controlling
the operation of the scanner so that, during scanner operation, the
beam produced from the beam producing mechanism passes along a
portion of the central reference plane, to at least one of the
rotating light reflective surfaces of the beam sweeping mechanism,
and as the beam sequentially reflects off a plurality of the
rotating optically reflective surfaces, the beam is repeatedly
swept across a plurality of the stationary optically reflective
surfaces thereby producing a plurality of groups of plural scan
lines, respectively, which are projected out through the optically
admissive window and intersect about a projection axis within a
collimated scanning volume having an approximately columnar extent
and extending from adjacent said optically admissive window to at
least about six inches therefrom so as to produce a collimated
projected scanning pattern.
24. The scanner of claim 23 further comprising a mechanism adapted
for intuitive aiming of the housing such that: (i) the housing is
supportable relative to an object bearing a code symbol wherein,
when a code symbol is presented within the collimated scanning
volume: (i) the code symbol is scanned omnidirectionally by the
collimated scanning pattern, (ii) at least a portion of the optical
energy reflected from said scanned code symbol is directed through
said optically admissive window, reflected off at least one of the
stationary optically reflective surfaces, and then reflected off at
least one of the rotating optically reflective surfaces of the beam
sweeping mechanism, and (iii) thereafter the reflected optical
energy is collected by the optical collection element, and received
by the optical receiver for detection, whereupon the electrical
signal is produced for processing by the signal processor; and
wherein the housing is adapted to permit a user to control the
direction of said projection axis so as to align the collimated
scanning volume with the bar code symbol on the object to be
scanned.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to laser scanning
systems, and more particularly to an automatic bar code symbol
reading system in which an automatic hand-supportable laser scanner
can be interchangeably utilized as either a portable hand-held
laser scanner in an automatic "hands-on" mode of operation, or as a
stationary laser projection scanner in an automatic "hands-free"
mode of operation.
[0003] 2. Brief Description of the Prior Art
[0004] Bar code symbols have become widely used in many commercial
environments such as, for example, point-of-sale (POS) stations in
retail stores and supermarkets, inventory and document tracking,
and diverse data control applications. To meet the growing demands
of this recent technological innovation, bar code symbol readers of
various types have been developed for scanning and decoding bar
code symbol patterns and producing symbol character data for use as
input in automated data processing systems.
[0005] In general, prior art hand-held bar code symbol readers
using laser scanning mechanisms can be classified into two major
categories.
[0006] The first category of hand-held laser-based bar code symbol
readers includes manually-actuated trigger-operated systems having
lightweight, hand-held laser scanners which can be supported in the
hand of the user. The user positions the hand-held laser scanner at
a specified distance from the object bearing the bar code symbol,
manually activates the scanner to initiate reading and then moves
the scanner over other objects bearing bar code symbols to be read.
Prior art bar code symbol readers illustrative of this first
category are disclosed in U.S. Pat. No. 4,387,297 to Swartz; U.S.
Pat. No. 4,575,625 to Knowles; U.S. Pat. No. 4,845,349 to Cherry;
U.S. Pat. No. 4,825,057 to Swartz, et al.; U.S. Pat. No. 4,903,848
to Knowles; U.S. Pat. No. 5,107,100 to Shepard, et al.; U.S. Pat.
No. 5,080,456 to Katz, et al.; and U.S. Pat. No. 5,047,617 to
Shepard, et al.
[0007] The second category of hand-held laser-based bar code symbol
readers includes automatically actuated systems having lightweight
triggerless hand-held laser scanners which can be supported in the
hand of the user. The user positions the hand-held laser scanner,
at a specified distance from the object bearing the bar code the
presence of the object is automatically detected, the presence of
the bar code symbol on the object is detected, and thereafter the
detected bar code symbol automatically read. Prior art illustrative
of this second category of laser-based bar code symbol reading
systems are disclosed in U.S. Pat. No. 4,639,606 to Boles, et al.,
and U.S. Pat. No. 4,933,538 to Heiman, et al.
[0008] While prior art hand-held and stationary laser scanners have
played an important role in the development of the bar code symbol
industry, these devices have, however, suffered from a number of
shortcomings and drawbacks. For example, hand-held laser scanners,
although portable and lightweight, are not always convenient to use
in assembly-line applications where the user processes bar coded
objects over an extended period of time, or where the user requires
the use of both hands in order to manipulate the objects. In some
applications, hand-held laser scanners are difficult to manipulate
while simultaneously moving objects or performing other tasks at a
point-of-sale terminal. Stationary laser scanners, on the other
hand, provide a desired degree of flexibility in many applications
by allowing the user to manipulate bar coded objects with both
hands. However, by their nature, stationary laser scanners render
scanning large, heavy objects a difficult task as such objects must
be manually moved into or through the laser scan field.
[0009] Attempting to eliminate the problems associated with the use
of hand-held and stationary laser scanners, U.S. Pat. No. 4,766,297
to McMillan discloses a bar code symbol scanning system which
combines the advantages of hand-held and stationary fixed laser
scanners into a single scanning system which can be used in either
a hands-on or hands-free mode of operation. The bar code symbol
scanning system in U.S. Pat. No. 4,766,297 includes a portable
hand-held laser scanning device for generating, electrical signals
descriptive of a scanned bar code symbol. In the hands-on mode of
operation, a trigger on the hand-held laser1 scanning device is
manually actuated each time a bar code symbol on an object is to be
read. The system further includes a fixture1 having a head portion
for receiving and supporting the hand-held laser scanning device,
and a base portion above which the head portion is supported at a
predetermined distance. In the hands-free mode of operation, the
hand-held laser scanning device is supported by the fixture head
portion above the fixture base portion in order to allow objects
bearing bar code symbols to pass between the head and base portions
of the fixture. In order to detect the presence of an object
between the head and base portions of the fixture, the fixture also
includes an object sensor operably connected to the hand-held laser
scanning device. When the object sensor senses an object between
the head portion and the base portion, the object sensor
automatically initiates the hand-held laser scanning device
supported in the fixture to read the bar code symbol on the
detected object.
[0010] While the bar code symbol scanning system of U.S. Pat. No.
4,776,297 permits reading of printed bar code information using
either a portable "hands-on" or stationary "hands-free" mode of
operation, this system suffers from several significant
shortcomings and drawbacks as well.
[0011] In particular, in the hands-on mode of operation, scanning
bar code symbols requires manually actuating a trigger each time a
bar code symbol is to be read. In the hands-free mode of operation,
scanning bar code symbols requires passing the object bearing the
bar code between the head and base portions of the fixture.
However, in many instances where both hands are required to
manipulate a bar coded object, the object is too large to be passed
between the head and base portions of the fixture and thus scanning
of the bar code symbol is not possible.
[0012] In an attempt to address such problems, several hand-held
projection laser scanners have been developed for omnidirectional
code symbol scanning. Examples of such systems include the NCR 7890
presentation scanner from the NCR Corporation and the LS9100
omnidirectional laser scanner from Symbol Technologies, inc. While
each of these systems produces an omnidirectional laser scan
pattern from a hand-supportable housing and have hands-free and
hands-on modes of operation, each of these scanning devices suffer
from a number of shortcomings and drawbacks. In particular, the
spatial extent of the laser scan pattern produced from each of
these scanners frequently results in the inadvertent scanning of
code symbols on products placed near the scanner during its
hands-free mode of operation. In the hands-on mode of operation, it
is virtually impossible to use the scanners to read bar code symbol
menus provided in diverse application environments. Moreover, in
each of these scanner designs, the scanner is tethered to its base
unit by a power/signal cord, and the user is required to handle the
scanner housing in an awkward manner in the hands-on mode of
operation, resulting in strain and fatigue and thus a decrease in
productivity. In addition, the control structure provided in each
of these hand-held projection scanners operates the scanner
components in a manner which involves inefficient consumption of
electrical power, and prevents diverse modes of automatic code
symbol reading which would be desired in portable scanning
environments.
[0013] Thus, there is a great need in the bar code symbol reading
art for a bar code symbol reading system which overcomes the above
described shortcomings and drawbacks of prior art devices and
techniques, while providing greater versatility in its use.
OBJECTS AND SUMMARY OF THE INVENTION
[0014] Accordingly, it is a primary object of the present invention
to provide a fully automatic bar code symbol reading system having
an automatic hand-supportable laser scanning device which can be
used at a point-of-sale (POS) station as either a portable
hand-supported laser scanner when operated in its automatic
hands-on mode of operation, or as a stationary laser projection
scanner when operated in its automatic hands-free mode of
operation.
[0015] It is another object of the present invention to provide
such an automatic bar code symbol reading system, wherein a highly
collimated laser scanning pattern is projected from the
hand-supportable device about a projection axis, and comprises
laser scanning planes which intersect within a narrowly confined
scanning volume extending about the projection axis so that bar
code symbols disposed within the scanning volume can be read
omnidirectionally, while inadvertent scanning of bar code symbols
outside of the scanning volume is prevented.
[0016] It is another object of the present invention to provide
such an automatic bar code symbol reading system, wherein the
projection axis about which the narrowly confined scanning volume
extends is substantially coplanar with the longitudinal axis of the
head and if handle portions of the hand-supportable housing.
[0017] It is another object of the present invention to provide an
automatic hand-supportable laser projection scanner having a
center-of-mass which provides easy handling, consistent with
ergonometric design principles, for fatigue-free omnidirectional
scanning of bar code symbols.
[0018] Another object of the present invention to provide automatic
hand-supportable omnidirectional laser protection scanner with a
hand-supportable housing that allows to user to easily control the
direction of its projection axis by way of the handle portion of
the housing, and thus align the narrowly confined scanning volume;
of the scanner with the bar code symbol on the object to be scanned
and identified.
[0019] Another object of the present invention to provide a
portable automatic hand-supportable omnidirectional laser
projection scanner with a power-conserving control system that
provides battery power to the system components of the scanner in
an intelligent manner.
[0020] Another object of the present invention to provide an
automatic hand-supportable omnidirectional laser projection scanner
having a hand-supportable housing with a scan-head that visually,
indicates the direction of the projection axis, for intuitive
hand-supported omnidirectional scanning of bar code symbols within
the narrowly confined scanning volume extending thereabout.
[0021] It is another object of the present invention to provide
such an automatic bar code symbol reading system, in which one or
more bar code symbols on an object can be automatically read in a
consecutive manner.
[0022] A further object is to provide such an automatic bar code
symbol reading device, in which the automatic hand-supportable bar
code (symbol) reading device has an infrared light object detection
field which spatially encompasses at least a portion of its
volumetric scanning field along the operative scanning range of the
device, thereby improving the laser beam pointing efficiency of the
device during the automatic bar code reading process of the present
invention.
[0023] Another object of the present invention is to provide such
an automatic bar code reading system with a scanner support stand
that supports the hand-supportable housing of the device in a
selected mounting position, and permits complete gripping of the
handle portion of the hand-supportable housing prior to removing it
therefrom.
[0024] Another object of the present invention is to provide an
automatic bar code symbol reading system, in which battery power
from a supply within the hand-supportable housing of its portable
bar code symbol reading device is automatically metered out and
provided to the power distribution circuitry thereof for a
predetermined time period which is reset upon the occurrence of
either the manual actuation of an externally mounted power reset
button, the reading (i.e. scanning and decoding) of a valid bar
code symbol, or the placement of the hand-supportable bar code
symbol reading device within its scanner support stand.
[0025] A further object of the present invention is to provide such
an automatic bar code symbol reading device, with a novel automatic
power control circuit that effectively conserves the consumption of
battery power therein, without compromising the operation, or
performance of the device during its diverse modes of automatic
operation.
[0026] It is another object of the present invention is to provide
an automatic hand-supportable bar code reading device having both
long and short-range modes of bar code symbol reading,
automatically selectable in a variety of different ways, (e.g. by,
placing the hand-supportable device within its support stand,
removing it therefrom).
[0027] Another object of the present invention is to provide such a
multi-mode automatic bar code symbol reading device, so that it
can: be used in various bar code symbol reading applications, such
as, for example, charge coupled device (CCD) scanner emulation,
counter-top projection scanning in the hands-free long-range mode
of operation, or the like.
[0028] Another object of the present invention is to provide an
automatic hand-supportable bar code reading device with a
programmably selectable mode of operation that prevents multiple
reading of the same bar code symbol due to dwelling of the laser
scanning beam upon a bar code symbol for an extended period of
time, yet allows a plurality of bar code symbols (e.g. representing
the same UPC) to be read in a consecutive manner even though they
are printed on the same, or apparently the same, object or surface,
as often is the case in inventory scanning applications.
[0029] A further object of the present invention is to provide a
point-of-sale station (POS) incorporating the automatic bar code
symbol reading system of the present invention.
[0030] It is a further object of the present invention is to
provide an automatic hand-supportable bar code reading device
having a control system which has a finite number of states through
which the device may pass during its automatic operation, in
response to diverse conditions automatically detected within the
object detection and scanning fields of the device.
[0031] Another object of the present invention is to provide a
portable, automatic bar code symbol reading device, wherein the
laser beam scanning motor is operated at a lower angular velocity
during its object detection state to conserve battery power
consumption and facilitate rapid steady-state response when the
device is induced into its bar code symbol detection and bar code
symbol reading states of operation.
[0032] Another object of the present invention is to provide a
portable automatic bar code symbol reading device, wherein the
laser beam scanning motor is denergized during its object detection
state to conserve battery power consumption therewhile, and is
momentarily overdriven to facilitate rapid steady-state response
when the device undergoes a transition from the object detection
state to the bar code symbol detection state of operation.
[0033] Another object of the present invention is to provide a
novel mechanism for mounting a projection laser scanning platform
within the head portion of an automatic hand-supportable
omnidirectional projection laser scanner.
[0034] Another object of the present invention is to provide a
novel omnidirectional laser scanning platform for use within an
automatic portable projection laser scanner.
[0035] Another object of the present invention is to provide a bar
code symbol reading system having at least one hand-supportable bar
code symbol reading device which, after each successful reading of
a code symbol, automatically synthesizes and then transmits a data
packet to a base unit positioned within the data transmission range
of the bar code symbol reading device, and upon the successful
receipt of the transmitted data packet and recovery of symbol
character data therefrom, the base unit transmits an acoustical
acknowledgement signal that is perceptible to the user of the bar
code symbol reading device residing within the data transmission
range thereof.
[0036] A further object of the present invention is to provide such
a system with one or more automatic (i.e., triggerless)
hand-supportable laser-based bar code symbol reading devices, each
of which is capable of automatically transmitting data packets to
its base unit after each successful reading of a bar code
symbol.
[0037] A further object of the present invention is to provide such
a bar code symbol reading system in which the hand-supportable bar
code symbol reading device can be used as either a portable
hand-supported laser scanner in an automatic hands-on mode of
operation, or as a stationary laser projection scanner in an
automatic hands-free mode of operation.
[0038] A further object of the present invention is to provide such
a bar code symbol system in which the base unit contains a battery
recharging device that automatically recharges batteries contained
in the hand-supportable device when the hand-supportable device is
supported within the base unit.
[0039] It is another object of the present invention to provide
such an automatic bar code symbol reading system with a mode of
operation that permits the user to automatically read one or more
bar code symbols on an object in a consecutive manner.
[0040] A further object of the present invention is to provide such
an automatic bar code symbol reading system, in which a plurality
of automatic hand-supportable bar code symbol reading devices are
used in conjunction with a plurality of base units, each of which
is assigned to a particular bar code symbol reading device.
[0041] A further object of the present invention is to provide such
an automatic bar code symbol reading system, in which radio
frequency (RF) carrier signals of the same frequency are used by
each hand-supportable bar code symbol reading device to transmit
data packets to respective base units.
[0042] A further object of the present invention is to provide such
an automatic bar code symbol reading system, in which a novel data
packet transmission and reception scheme is used to minimize the
occurrence of data packet interference at each base unit during
data packet reception.
[0043] A further object of the present invention is to provide such
an automatic bar code symbol reading system, in which the novel
data packet transmission and reception scheme enables each base
unit to distinguish data packets associated with consecutively
different bar code symbols read by a particular bar code symbol
reading device, without the transmission of electromagnetic-based
data packet acknowledgment signals after receiving each data packet
at the base unit.
[0044] It is a further object of the present invention to provide
an automatic hand-supportable bar code reading device having a
control system which has a finite number of states through which
the device may pass during its automatic operation, in response to
diverse conditions automatically detected within the object
detection and scan fields of the device.
[0045] It is yet a further object of the present invention to
provide a portable, fully automatic bar code symbol reading system
which is compact, simple to use and versatile.
[0046] Yet a further object of the present invention is to provider
a novel method of reading bar code symbols using an automatic
hand-supportable omnidirectional laser scanning device.
[0047] These and further objects of the present invention will
become apparent hereinafter and in the claims to Invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0048] For a fuller understanding of the Objects of the Invention,
the Detailed Description of the Illustrated Embodiments of the
Present Invention should be read in conjunction with the
accompanying drawings, wherein:
[0049] FIG. 1A is an elevated perspective view of the illustrative
embodiment of the automatic bar code symbol reading system hereof,
with its hand-supportable bar code symbol reading device shown
supported within the scanner support stand portion of its matching
base unit, and arranged for automatic hands-free operation;
[0050] FIG. 1B is an elevated perspective view of the illustrative
embodiment of the automatic bar code symbol reading device hereof,
shown being used in its automatic hands-on mode of operation;
[0051] FIG. 1C is an elevated side view of the illustrative
embodiment of the automatic bar code symbol reading device hereof,
illustrating that the mass balance of the hand-supportable bar code
symbol reading device has been designed to minimize torques about
the point of pivot of the housing which occurs about the user's
index finger in order to maximize its ergonomic handling efficiency
eliminate fatigue during automatic hands-on, omnidirectional laser
scanning operations;
[0052] FIG. 1D is an elevated side view of the illustrative
embodiment of the automatic bar code symbol reading device hereof,
illustrating the spatial alignment of the longitudinal axis of the
head portion of the scanner and the projection axis of the laser
scanning platform contained therein;
[0053] FIG. 1E is an elevated side view of the illustrative
embodiment of the automatic bar code symbol reading device hereof,
shown supported within the scanner support stand portion of its
matching base unit, arranged for automatic hands-free operation in
a first scanning position;
[0054] FIGS. 1F and 1G provide an elevated side view of the
illustrative embodiment of the automatic bar code symbol reading
device hereof, shown supported within the scanner support stand
portion of its matching base unit, arranged for automatic
hands-free operation in a second scanning position;
[0055] FIG. 2A is an elevated side view of the illustrative
embodiment of the automatic bar code symbol reading device of the
present invention, illustrating the spatial relationship between
the object detection and scan fields of the device, and the long
and short-ranges of programmed object detection, bar code presence
detection, and bar code symbol reading;
[0056] FIG. 2B is a plan view of the automatic bar code symbol
reading device taken along line 2A-2A of FIG. 2;
[0057] FIG. 3A is an elevated, cross-sectional side view of the
automatic bar code symbol reading device of the present invention,
taken along its longitudinal axis, showing the various components
contained therein;
[0058] FIG. 3B is an elevated, end view of the automatic bar code
symbol reading device of the present invention, taken along line
3B-3B of FIG. 1D, showing the various components contained
therein;
[0059] FIG. 4 is an elevated side view of the laser scanning
platform of the present invention realized on its shock-mounted
optical bench, removed from the housing of the hand-supportable bar
code symbol reading device of the present invention;
[0060] FIG. 5A is a plan view of the optical bench of the laser
scanning platform of FIG. 4, shown with the stationary array of
mirrors, rotating polygonal mirror and motor removed therefrom for
illustrative purposes;
[0061] FIG. 5B is a view of the laser scanning platform of the
present invention taken along line 5B-5B of FIG. 4;
[0062] FIG. 5C is an elevated side view of the optical bench of
FIG. 5A, shown with the stationary mirror support bracket removed
therefrom for illustrative purposes;
[0063] FIG. 5D is schematic diagram illustrating the physical
layout of components on the analog signal processing board
supported on the optical bench of the laser scanning platform of
FIG. 4;
[0064] FIGS. 6A1, 6A2 and 6B provide a geometrical optics model of
the stationary mirror array of the laser scanning platform of the
illustrative embodiment, graphically defining the various angles
used to configure the stationary mirrors relative to the central
reference plane thereof;
[0065] FIG. 6C is a geometrical optics model of the stationary
mirror array of the laser scanning platform of the illustrative
embodiment, graphically defining the various physical dimensions
stationary mirrors relative to the central reference plane
thereof;
[0066] FIG. 6D is a geometrical optics model of the stationary
mirror array of the laser scanning platform of the illustrative
embodiment, graphically defining the various physical dimensions
stationary mirrors relative to the central reference plane
thereof;
[0067] FIGS. 7A and 7B are cross-sectional views of the 3-D laser
scanning volume of the illustrative embodiment, taken parallel to
the light transmissive window at about 1.0" and 5.0" therefrom;
[0068] FIG. 8 is a system block functional diagram of the automatic
bar code symbol reading system of the present invention,
illustrating the principal components integrated with the control
(sub)-system thereof;
[0069] FIG. 8A is a schematic diagram of the automatic power supply
unit aboard the automatic bar code symbol reading device of the
present invention;
[0070] FIG. 8B is a functional logic diagram of the oscillator
circuit in the Application Specific Integrated Circuit (ASIC) chip
in the automatic bar code symbol reading device of the present
invention;
[0071] FIG. 8C is a timing diagram for the oscillator circuit of
FIG. 8B;
[0072] FIG. 8D is a block functional diagram of the object
detection circuit (i.e., system activation means) in the ASIC chip
in the automatic bar code symbol reading device of the present
invention;
[0073] FIG. 8E is a functional logic diagram of the first control
circuit (C.sub.1) of the control system of the present
invention;
[0074] FIG. 8F is a functional logic diagram of the clock divide
circuit in the first control circuit C.sub.1 of FIG. 8E;
[0075] FIG. 8G is table setting forth Boolean logic expressions for
the enabling signals produced by the first control circuit
C.sub.1;
[0076] FIG. 8H is a functional block diagram of the analog to
digital (A/D) signal conversion circuit in the ASIC chip in the bar
code symbol reading device of the present invention;
[0077] FIG. 8I is a functional logic diagram of the bar code symbol
(presence) detection circuit in the ASIC chip in the bar code
symbol reading device of the present invention;
[0078] FIG. 8J is a functional logic diagram of the clock divide
circuit in the bar code symbol detection circuit of FIG. 8I;
[0079] FIG. 8K is a schematic representation of the time window and
subintervals maintained by the bar code symbol detection circuit
during the bar code symbol detection process,
[0080] FIG. 8L is a functional logic diagram of the second control
circuit (C.sub.2) in the ASIC chip in the automatic bar code symbol
reading device of the present invention;
[0081] FIG. 8M is Boolean logic table defining the functional
relationships among the input and output signals into and out from
the second control circuit C.sub.2 of FIG. 8N;
[0082] FIG. 8N is a schematic representation of the format of each
data packet transmitted from the data packet transmission circuit
of FIG. 9.
[0083] FIG. 9 is a functional block diagram of the data packet
transmission circuit of the bar code symbol reading device of the
present invention;
[0084] FIG. 10 is a schematic representation illustrating several
groups of data packets transmitted from the bar code symbol reading
device hereof in accordance with the principles of data packet
transmission and reception scheme of the present invention;
[0085] FIG. 11 is a schematic representation of an exemplary set
off groups of data packet pseudo-randomly transmitted from
neighboring bar code symbol reading devices, and received at one
base unit in physical proximity therewith;
[0086] FIG. 12 is a schematic representation of an exemplary set of
data packets simultaneously transmitted from three neighboring bar
code symbol reading devices of the present invention, and received
at the associated base units assigned thereto;
[0087] FIGS. 13A, 13AA, 13B, 13C, taken together, show a high level
flow chart of the control process performed by the control
subsystem of the bar code symbol reading device, illustrating
various modes of object detection, bar code presence detection and
bar code symbol reading;
[0088] FIG. 14 is a state transition diagram illustrating the
various states that the automatic hand-supportable bar code symbol
reading device of the illustrative embodiment may undergo during
the course of its programmed operation;
[0089] FIG. 15A is a perspective view of the scanner support stand
portion of the countertop base unit of the present invention;
[0090] FIG. 15B is a perspective view of the base plate portion of
the countertop base unit of the present invention;
[0091] FIG. 16 is a functional block diagram of the data packet
receiving and processing circuitry and the acknowledgment signal
generating circuitry of the present invention realized on the
printed circuit board in the base unit shown in FIGS. 15A to
15C;
[0092] FIG. 16A is a functional block diagram of the radio receiver
subcircuit of the data packet receiving circuit of FIG. 16;
[0093] FIG. 16B is a functional block diagram of the digitally
controlled acoustical acknowledgment signal generating circuit of
the present invention;
[0094] FIGS. 17 and 17A is a flow chart illustrating the steps
undertaken during the control process carried out in the base unit
of FIG. 15A;
[0095] FIG. 18A is perspective view of a point-of-sale (POS)
station according to the present invention, showing the automatic
hand-supportable bar code symbol reading device hereof being used
in its automatic "hands-free" long-range mode of operation; and
[0096] FIG. 18B is a perspective view of the POS station of FIG.
18A, showing the symbol reading device hereof being used in its
automatic "hands-on" short-range mode of operation.
DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT OF THE PRESENT
INVENTION
[0097] As shown in FIGS. 1 to 3B, automatic bar code symbol reading
system 1 of the illustrative embodiment of the present invention
comprises an automatic (i.e., triggerless) portable bar code
(symbol) reading device 2 operably associated with a base unit 3
having a scanner support stand 4 pivotally connected thereto, for
releasably supporting the automatic bar code symbol reading device
2 at any one of a number of positions above of a counter surface at
a Point of Sale (POS) station. In the preferred embodiment, the bar
code symbol reading device 2 is operably connected with its the
base unit 3 by way of a one way electromagnetic link 5 that is
momentarily created between bar code symbol reading device 2 and
its mated base unit 3 after the successful reading of each bar code
symbol by the bar code symbol reading device. Operable
interconnection between the base unit and a host system (e.g.,
electronic cash register system, data collection device, etc.) 6 is
achieved by a flexible multiwire communications cable. 7 extending
from the base unit and plugged directly into the data-input
communications port of the host computer system 6. In the
illustrative embodiment, electrical power from a low voltage direct
current (DC) power supply (not shown) is provided to the base unit
by way of a flexible power cable 8. Notably, this DC power supply
can be realized in host computer system 6 or as a separate DC power
supply adapter pluggable into a conventional 3-prong electrical
socket. In other embodiments of the present invention, cables 7 and
8 can be integrated to provide a single flexible, multi-wire cable
for transmission of power to the base unit and data to the host
system. As will be described in greater detail hereinafter, a
rechargeable battery power supply unit 20 is contained primarily
within the handle portion of the bar code symbol reading device 2
in order to energize the electrical and electro-optical components
within the device.
[0098] As illustrated in FIGS. 1A through 1B, scanner support stand
4 is particularly adapted for receiving and supporting portable bar
code symbol reading device 2 without user support, thus providing a
stationary, automatic hands-free mode of operation. In general,
portable bar code symbol reading device 2 includes an ultra-light
weight hand-supportable housing 9 having a head portion 9A and a
contoured handle portion 9B. As will be described in greater detail
hereinafter, head portion 9A encloses electro-optical components
which are arranged in a novel scanning platform 10 of ultra compact
construction which renders possible the production of a highly
collimated scanning pattern 11 through light transmission window 12
for the purpose of scanning bar code symbols on objects within a
narrowly confined scanning (i.e., 3-D scan field) volume 13, while
preventing unintentional scanning of, bar code symbols on objects
located outside thereof at point of sale (POS) stations. Thus, by
minimizing the amount of counter-space that must be clear (i.e.
free) of bar coded items at point of sale POS stations, the laser
scanner of the present invention provides retailers with greater
counter-space availability for displaying merchandise and the like,
yet without sacrificing the; increase in check-out performance and
worker productivity associated with the use of bar code symbol
scanners at POS stations.
[0099] As illustrated in FIGS. 1 through 1C, the base unit 3
includes a base portion 14 which can be realized in a variety of
different ways. For example, the base portion 14 can be realized,
as a compact stand for support upon a countertop surface as shown
in FIG. 18, or it can be realized as a support mount for vertical
wall-mounting. In either embodiment, the function of the scanner
stand 4 is to support the device in any one of a plurality of
positions above a workspace 19 which may be a counter surface in
POS applications. With this arrangement, the highly collimated
scanning pattern 11 can be projected about the projection axis 17
above the counter surface in any one of a plurality of orientations
corresponding to the plurality of positions.
[0100] As shown in FIGS. 1A and 15A, base portion 14 contains
electronic circuitry realized on a PC board 16 for carrying out
various types of functions, namely: reception of electrical power
from the host system and coupling electrical power to the
rechargeable battery contained within the hand-supportable housing;
reception of data packets transmitted from the automatic bar code
symbol reading device, and processing the same for data recovery;
generation of acoustical and/or optical acknowledgement signals;
and transmission of symbol character data to the host system. Each
of these functions will be described in greater detail hereinafter
with reference to FIGS. 15A and 15B.
[0101] As illustrated in FIGS. 1B and 1C in particular, the head
portion 9A continuously extends into contoured handle portion 9B at
an obtuse angle .alpha. which, in the illustrative embodiment, is
about 115 degrees. It is understood, however, that in other
embodiments obtuse angle a may be in the range of about 100 to
about 150 degrees. As illustrated in FIG. 1C, the mass balance of
the device is particularly designed so that when the device is held
within the user's hand, the index finger of the user is disposed
beneath the head portion of the housing, and provides a pivot point
about which there is substantially zero torque acting upon the
device, preventing it from rotating in either direction about the
index finger. Instead, the resultant force distribution acting upon
the user's hand is aligned in the direction of gravitational
forces, as indicted in FIG. 1C. The effect of this mass-balanced
scanner design is to minimize the torque imposed on the user's
wrists and forearms while using the bar code symbol reading device
in the hands-on mode of operation. This, in turn, minimizes the
amount of energy which the user must expend during hands-on
scanning operations, thereby reducing wrist and arm fatigue and
increasing worker productivity. In addition to the above,
advantages, the hand-supportable housing hereof is sculptured
(i.e., form-fitted) to the human hand so that automatic hands-on;
scanning is rendered easy and effortless. Also, the ergonomic
housing design eliminates the risks of musculoskeletal disorders,
such as carpal tunnel syndrome, which can result from repeated
biomechanical stress commonly associated with pointing prior art
gun-shaped scanners at bar code symbols, and squeezing a trigger to
activate the laser scanning beam, and then releasing the
trigger.
[0102] As best shown in FIGS. 1G, 15A and 15B, stand portion 4 of
the base unit 3 is pivotally supported with respect to the base
portion by way of pivot pins 22A and 22B. In order to releasably
hold the stand portion of the base unit relative to the base
portion thereof in any one of a number of provided scanning
positions, a releasable stand-locking mechanism 23 is provided. As
shown in FIG. 1G, the locking mechanism is realized as a set of
projections 24 formed on the inside surface of the support arms 4A
of the stand portion of the base unit, and a projection-catch 25
formed on the adjacent surface of the base portion. These structure
features of the base unit are shown in FIG. 1G. rhe function of the
projection catch 25 is to releasably engage one of the projections
24 associated with the selected scanning position. Gentle rotation
of the head portion of the scanner while supported in its stand
causes the projection caught in the projection-catch 25 to release
therefrom, allowing the scanner to be repositioned as desired. At
the resulting scanning position, the corresponding projection 24
automatically engages with the projection-catch 25 and locks the
stand portion of the base unit relative to the base portion
thereof. In addition, to allow the base unit to easily rotate
relative to its support surface, the bottom of the base portion is
realized as a turntable structure that allows its bottom section
26A to be stationary relative to the support surface (i.e.
countertop) 27, while the upper section 26B is fixed relative to
the balance of the base portion of the base unit. A pivot 26C is
used to pivotally connect the upper and lower sections together for
easy rotation of the base unit relative to the support surface.
[0103] In FIGS. 1E and 1F, the automatic bar code symbol reading
system of the present invention is arranged in two extreme scanning
configurations during the automatic hands-free mode of system
operation. In these different scanning configurations, the stand
portion of the base unit is arranged differently with respect to
the base portion of the base unit. In FIG. 1E, the stand portion of
the base unit is shown supporting the hand-supportable projection
scanning device hereof so that its narrowly-confined 3-D scanning
volume 13 is projected in a direction slightly off-parallel to the
counter surface upon which the base unit is a supported. In this
hands-free scanning configuration, code symbols on large objects
can be easily scanned by simply presenting the code symbol to the
narrowly-confined scanning volume 13 projected, along the "pointing
direction" (i.e. longitudinal axis) of the head portion of the
scanner housing. In FIG. 1F, the stand portion of the base unit is
shown supporting the hand-supportable projection scanning device
hereof so that its scanning volume is projected downwardly, in a
direction passing through the counter surface upon which the base
unit is supported. In this hands-free scanning configuration, code
symbols on small objects can be easily scanned by simply presenting
to the code symbol to the narrowly-confined scanning volume 13
projected beneath the head portion of the scanner housing.
[0104] As illustrated in FIGS. 2A through 3B, the head portion 9A
of the hand-supportable housing has a light transmission aperture
12A formed in the front portion thereof. As shown, the light
transmission window 12 is mounted over the entire light
transmission aperture. In the preferred embodiment, the spectral
transmission characteristics of the light transmission window are
such that all wavelengths greater (i.e. longer) than slightly less
than 670 nm (e.g. longer than 665 nm) are permitted to exit and
enter the interior volume of the housing with minimum attenuation.
As a result of such characteristics, the visible laser line at 670
nanometers and the infra-red (IR) spectral line at 870 nm (produced
from the object sensing circuitry hereof) are allowed to propagated
through the transmission window, out of the head portion of the
housing, reflect from an object/bar code surface, and return
through the transmission window. Notably, all other surfaces of the
handsupportable housing are opaque to electromagnetic radiation in
the visible band.
[0105] As illustrated in FIGS. 2, and 2A, in particular, the bar
code symbol reading device 2 generates from its laser scanning
platform 10, two different types of fields external to its
hand-supportable housing. As explained below, these fields function
to carry out a novel bar code symbol reading process according to
the principles of the present invention. The first field, referred
to as the "object detection field", indicated by broken and dotted
lines 30, is provided external to the housing for detecting energy
reflected off an object (bearing a bar code symbol) located in the
object detection field. As shown in FIGS. 2A and 2B, the second
field 31, referred to as the "scan field" or "3-D scan field" (i.e.
narrowly-confined scanning volume 13), has a multiplicity of laser
beam scanning planes contained therewithin projected external to
the head portion of the housing. The function of the scanning
volume (i.e. 3-D scan field) is to scan a bar code symbol on an
object automatically detected in the object detection field. In the
preferred embodiment, bar code symbol scanning is achieved using a
scanned visible laser beam which, after reflecting off the bar code
symbol in the scanning volume 13, produces laser scan data that is
collected for the purpose of automatically detecting the bar code
symbol and subsequently reading (i.e., scanning and decoding) the
same.
[0106] In general, detected energy reflected from an object during
object detection can be optical radiation or acoustical energy,
either sensible or non-sensible by the user, and may be either
generated from the automatic bar code reading device or an external
ambient source. However, as will be described in greater detail
hereinafter, the provision of such energy is preferably achieved by
transmitting a wide beam of pulsed infrared (IR) light away from
transmission aperture 11, in a direction substantially parallel to
longitudinal axis 16 of the hand-supportable housing. In the
preferred embodiment, the object detection field, from which such
reflected energy is collected, is designed to have a narrowly
diverging pencil-like geometry of three-dimensional volumetric
expanse, which is spatially coincident with at least a portion of
the transmitted infrared light beam. This feature of the present
invention ensures that an object residing within the object
detection field will be illuminated by the infrared light beam, and
that infrared light reflected therefrom will be directed generally
towards the transmission aperture of the housing where it can be
automatically detected to indicate the presence of the object
within the object detection field. In response to object presence
detection, a visible laser beam is automatically generated within
the interior of the bar code symbol reading device, projected
through the light transmission aperture of the housing and
repeatedly scanned across the scanning volume, within which at
least a portion of the detected object lies. At least a portion of
the scanned laser light beam will be scattered and reflected if the
object and directed back towards and through light transmissive
window 11 for collection and detection within the interior of the
bar code symbol reading device, and subsequently processed in a
manner which will be described in detail hereinafter.
[0107] To ensure that the user can quickly align the visible laser
beam with the bar code symbol on the detected object, the object
detection field of the preferred embodiment is designed to
spatially encompass a significant portion of the 3-D scanning
volume along the operative scanning range of the device, as
illustrated in FIGS. 2A and 2B, for the first illustrative
embodiment of the present invention. This structural feature of the
present invention improves the laser beam pointing efficiency of
the device during the automatic bar code symbol reading
process.
[0108] As best shown in FIGS. 3A and 3B, the laser scanning
platform (i.e., laser scanning engine) 10 of the present invention
is mounted within the head portion of the hand-supportable housing
by way of a three-point shock-absorbing mounting mechanism, which
will be described in greater detail hereinbelow. In the
illustrative embodiment, the hand-supportable housing is realized
as a five-piece split-housing construction comprising: a first
housing portion 9C carrying three spaced-apart mounting posts 29A,
29B and 29C, and providing a battery storage bay 30 for storage of
a (rechargeable) battery supply unit 32; a second housing half 9D
providing posts 31A and 31B which engage with support posts 29A and
29B when the first and second housing halves are brought together;
a battery cover 9E for placement over the battery storage bay 30; a
housing end cap 9F for placement over the ends of the first and
second housing halves; and a housing bumper 9G for supporting the
light transmission window 12 and holding securely together the
front ends of the first and second housing halves when the
subcomponents of the housing are assembled together. Provided
within the battery storage bay, is an electrical socket 33 designed
to receive rechargeable battery 32 when it is installed within the
bay when the bay cover 9E is removed. An electrical wire harness 34
is used to connect the battery socket 33 to a printed circuit (PC)
board 50 supported upon the laser scanning platform 10, carrying
digital scan data processing and control circuitry. Apertures 35A
and 35B are formed in the end portion of the housing handle to
allow electrodes 51A and 51B on the battery 32 to establish
electrical contact with charging electrodes 52A and 52B provided
within the support bay 60 of the stand portion of the base unit
when the scanning device is operated in its hands-free mode of
operation. Preferably, the above-described housing subcomponents
are made from a rugged, lightweight plastic material using
injection-molding techniques well known in the art.
[0109] As will be described in greater detail hereinafter, the data
packet transmission circuit of copending application Ser. No.
08/292,237, now U.S. Pat. No. 5,808,285 is realized on PC board 50,
along with the microprocessor used to implement symbol decoding,
data formatting and system control functions. Electrical power
supplied from rechargeable battery 32 is provided to the digital
signals processing/control board 50 by way of flexible wire harness
34. As shown, a transmitting antenna 53 is operably connected to
the data packet transmission circuit on the digital signal
processing board and is mounted within hand-supportable housing 9
for transmission of a data packet modulated RF carrier signal. The
structure and the functionalities of the automatic bar code symbol
reading system hereof will be described in greater detail
hereinafter with reference to FIGS. 8 to 14.
[0110] In FIG. 4, the laser scanning platform 10 is shown removed
from its housing. As shown, the laser scanning platform comprises
an assembly of subcomponents assembled upon an optical bench 34
with respect to a central longitudinal reference plane 35
referenced in Fogs. SA through 5B, in particular. This subcomponent
assembly comprises: a scanning polygon 36 having four light
reflective surfaces 36A,36B, 36C and 36D, each disposed at an tilt
angle a with respect to the rotational axis of the polygon; an
electrical motor 37 mounted on the optical bench, and having a
rotatable shaft on which polygon 36 is mounted for rotationable
movement therewith; an array of stationary mirrors 38A, 38B, 38C,
38D and 38E fixedly mounted with respect to the optical bench; a
laser beam production module 39, fixedly mounted above the rotating
polygon, for producing a laser beam having a circularized beam
cross-section, and essentially free of astigmatism along its length
of propagation; an analog signal processing board 40, fixedly
mounted over the rotatable polygon, and carrying a photodetector 41
for detecting reflected laser light and producing analog scan data
signals, and analog signal processing control circuits 42 for
performing various functions, including analog scan data signal
processing; a light collecting mirror 43, disposed at a height
above the central stationary mirror 38C, for collecting light rays
reflected off the rotating polygon and focusing the same onto the
photodetector on the analog board; and a beam directing surface 44,
realized as a flat mirror mounted on the light collecting mirror
38C, for directing the laser beam from the laser beam production
module to the rotating polygon disposed therebeneath. As shown,
these subcomponents are mounted relative to the optical bench 34
according to the Specifications set forth in FIGS. 6A through
6B.
[0111] In FIGS. 5A through 5D, the subcomponents of the laser
scanning platform are shown in greater detail. In particular,
optical bench 34 is shown in FIG. 5A with the scanning motor 37
and, stationary mirror elements 38A through 38E removed for
illustration purposes. As shown, stationary mirror brackets 45 is
mounted upon the optical bench 34 and has five mirror support
elements 45A through 45B, disposed beneath the locations of their
respective mirrors 38A, 38B, 38C, 38D and 38E. As shown in FIG. 5B,
the analog signal processing board 40 is disposed above the
scanning polygon 36 and extends at an acute angle with respect to
the plane of the optical bench. The analog signal processing board
40 is supported in this position and orientation by a pair of
support bracket 46A and 46B. Support brackets 46A and 46B, in turn,
are supported by a pair of support posts 47A and 47B mounted to the
middle portion of the optical bench 34, as shown in FIGS. 5A and
5B. As illustrated in FIG. 4, the position of these support posts
are slightly forward of the rotational axis of the polygon
motor.
[0112] As best shown in FIG. 5A, the transverse axis of the light
collecting mirror 43 is perpendicular to the central reference
plane of the optical bench. The stationary light reflective surface
(i.e. mirror) 38C also has a transverse axis extending
substantially perpendicularly with respect to the central reference
plane 34. Stationary light reflective surfaces 38B and 38D are
symmetrically disposed on opposite sides of the central reference
plane, respectively, and immediately adjacent stationary light
reflective surface 38C. Stationary light reflective surfaces (i.e.
mirrors) 38A and 38E are symmetrically disposed on opposite sides
of the central reference plane, and immediately adjacent stationary
light reflective surfaces 38B and 38D, respectively, and adjacent
rotating polygon 36.
[0113] As best illustrated in FIG. 5C the angle of declination of
the light collecting mirror 43 is selected so that the incident
laser beam thereon from the laser beam production module 38 is
redirected towards the rotating polygon during laser beam scanning
operations. The focal length of the light collecting mirror 43 is,
selected so that collected light rays from the mirror are focused
upon the photodetector 41, centrally mounted upon the analog signal
processing board 40. In the illustrative embodiment, light focusing
mirror 43 is realized from ground-polished glass, or molded
plastic, coated with a mirror-finish by vapor deposition.
[0114] As shown in FIG. 5C, the photodetector 41 and light
collecting mirror 43 are aligned along a common optical axis which
is disposed within the central longitudinal plane. As shown in FIG.
5D, the photodetector 41 is mounted on the analog signal processing
board 40 along with signal processing circuits and signal connector
elements, namely: optical filters 186A; visible laser diode drive
circuitry 178; motor drive circuitry 181; IR preamp circuitry 187;
IR transmit and receive circuitry 106; signal processing circuitry
IC2; scan signal preamplification circuitry 187; microprocessor
port connector 300; and VLD/motor port connector 301. The function
of such components will be described in greater detail
hereinafter.
[0115] The laser beam production module 39 of the laser scanning
platform hereof may be realized in a variety of ways. Preferably,
each embodiment thereof comprises a visible laser diode for
producing a visible laser beam, and associated optics for
circularizing the laser beam and eliminating astigmatism therefrom
along its direction of propagation. In the illustrative embodiment,
the associated optics comprises an aspheric collimating lens, a
beam circularizing prism, and a holographically formed light
diffractive grating configured in such a manner that the
above-described functions are realized during laser beam
production. The manner in which such a laser beam production module
can be constructed without the use of aperture stops is taught in
copending application Ser. No. 08/573,949, now abandoned
incorporated herein by reference.
[0116] The particular parameters used to configure the optical
components of the laser scanning module are schematically
represented in FIGS. 6A1 through 6D. In FIGS. 6A1 and 6A2, a
geometrical optics model is provided for the illustrative,
embodiment of the laser beam scanning platform of the present
invention. Within this geometrical optics model, stationary mirror
surface 38A through 38E are designated by surface parameters S1
through S5, respectively. Each of these mirror surfaces is located
about the central longitudinal plane 35 of the system, which
functions as a reference plane. In the illustrative embodiment, the
distance between the rotational axis of the polygon and the base of
the central mirror surfaces S3 is 34 millimeters in the,
illustrative embodiment, whereas the base-to-base distance between
mirror surfaces S1 and S5 is about 35 millimeters.
[0117] As shown in the geometrical optics model, the angled of
inclination of the four mirrored surfaces on the polygon 36A, 36B,
36C, 36D are set forth in the Table of FIG. 6B. The angle of
elevation f (i.e. bend) of each of the stationary mirrors 38A, 38B,
38C, 38D and 38E are listed in Table of FIG. 6A1. As shown in FIG.
6B, the angle of inclination of the stationary mirrors is
references with respect to the plane of the optical bench. As shown
in FIG. 6A1, the angle of twist a for each stationary mirror is
referenced relative to the central longitudinal plane 35. The twist
angle for the stationary mirrors are set forth in the Table of FIG.
6A1. Notably, as central stationary mirror S3 is disposed
transversely relative to the central longitudinal plane, the twist
angle for this stationary mirror is 90.degree. The laterally
disposed stationary mirrors S2 and S4 have the same twist angle of
43.75.degree., whereas stationary mirrors S1 and S5 have the same
twist angles of 40.5.degree.
[0118] The heightwise and widthwise dimensions of the stationary
reflective surfaces, in part, determine the length of the scanlines
within the scan field. These dimensions are indicated in FIG. 6C
for the illustrative embodiment. Notably, the perimetrical
dimensions of these stationary mirrors are irregular in order to
form a tightly-nested stationary mirror array arranged about the
rotating polygon 36. The exact surface dimensions are indicated in
FIG. 6C. The heightwise and widthwise dimensions of the mirrors on
the rotating polygon are indicated in FIG. GD. When constructed in
accordance with the Specifications disclosed herein, the laser
scanning platform of the illustrative embodiment will produce a
highly collimated set of scanning planes which extend from the
light transmission window and intersect about the projection axis
17 to form a highly collimated scanning pattern within a
narrowly-confined 3-D scanning volume thereabout. Two-dimensional
cross-section characteristics of the resulting laser scanning
pattern at about 1.5 and 6 sinches from the transmission window are
shown in FIGS. 7A and 7B.
[0119] When assembled and configured as described above, the laser
scanning platform 10 is mounted with the upper and lower halves of
the hand-supportable housing 9A and 9B. Mounting is achieved by way
of resiliently securing shock-mounting support posts 29A, 29B and
29C to corresponding mounting holes formed within the optical bench
35 using rubber grommets and screws. As shown in FIG. 7, the
assembled laser scanning platform (i.e. engine) is installed within
the housing in a manner described above. As shown, PC board 5G is
mounted to the underside of the plastic optical bench by way of
mechanical fasteners known in the art. The function of PC board 50
is provide substrate upon which the decode/control processor, RF
data packet transmission circuitry and power. distribution
circuitry of the laser scanning device hereof are realized. In
order that the shock-absorbing mounting system can operate
properly, it is important that sufficient clearance is provided
between the outermost extensions of the scanning platform tand the
interior wall surface of upper portion of the housing. In this way,
the scanning platform is permitted to undergo gross displacements
in the directions of the dominant oscillatory modes of system when
the device is dropped onto the floor, knocked into solid objects
and the like under normal or otherwise expected operating
environments.
[0120] Having described the physical construction of the laser
scanning engine 10 of the present invention, it is appropriate at
this juncture to describe in greater detail the manner in which the
laser scanning pattern is produced from the laser scanning platform
hereof.
[0121] Upon detection of an object within the object detection
field 30, a laser beam is produced from the laser beam production
module 39 and is directed towards beam directing surface 44 mounted
on the light collecting mirror 43. The laser beam reflects from the
beam directing surface 44 towards the mirrored facets on the
rotating scanning polygon 36. As the polygon spins, the incident
laser beam reflects off the rotating mirrors 36A through 36D and
sweeps the laser beam about its rotational axis along a plurality
of different paths which intersect the stationary array of mirrors
38A through 38E on the optical bench. During each revolution of the
scanning polygon, the laser beam reflects off the rotating mirrors
and therewhile is repeatedly swept across the array of stationary
mirrors thereby producing first, second, third, fourth and fifth
groups of plural scan lines, respectively. These plural groups of
scanlines shown in FIGS. 7A and 7B are projected out through the
light transmission window and intersect about the projection axis
17 extending from the light transmission window, and within the
narrowly confined scanning volume 13. In the illustrative
embodiment, the intersection of the laser scanning planes extends
from adjacent (e.g. about 9.5" from) the light transmission window
to at least about 10.0 inches therefrom so as to produce a highly
collimated projected scanning pattern within the narrowly confined
3-D scanning volume. Within this 3-D scanning volume, a bar code,
symbol can be scanned omnidirectionally, while preventing
unintentional scanning of code symbols on objects located outsider
thereof.
[0122] As illustrated in the cross-sectional diagrams of FIGS. 7A
and 7B, there exists a particular relationship among the scanlines
of the laser scanning pattern of the illustrative embodiment. In
particular, each scan line in each group of scan lines is
substantially parallel to each other scan line in that group of
scan lines. As a result, when the code symbol is presented to the
highly collimated scanning pattern projected within narrowly
confined scanning field, the code symbol is automatically scanned
therewithin independent of the orientation of the code symbol
within the scanning field (i.e. scanning volume). At least a
portion of the laser light reflected from the scanned code symbol
is directed through the light transmission window, reflected off
the stationary light reflective surfaces, reflected off the
rotating mirrors, collected by the light focusing mirror, and
received by the photodetector 41, whereupon an electrical signal is
produced for use in decode signal processing. The details of such
signal processing operations, and the preferred means for achieving
the same, can be best understood with a detailed description of the
scan and control data processing circuitry embodied with the laser
scanning device of the present invention.
[0123] As shown in FIG. 8, the automatic bar code symbol reading
system of the present invention comprises the automatic laser
scanning device of the illustrative embodiment in combination with
a number of system components. These additional system components
include: a primary oscillator circuit 101 for producing a primary
clock signal CLK for use by the object detection circuit 107; a
first RC timing network 102 for setting the oscillation frequency,
of the primary oscillator circuit; first control means 104,
realized as a first control circuit C.sub.1, for performing
localized system control functions; a second RC timing network 105
for setting a timer T.sub.1 in control circuit C.sub.1; means
(e.g., an object sensing circuit 106 and an object detection
circuit 107) for producing a first activation control signal
A.sub.1=1 upon the detection of an object bearing a bar code in at
least a portion of the object detection field; a laser beam
scanning mechanism 108 for producing and scanning a visible laser
beam across the bar code symbol on the detected object;
photoreceiving circuit 109 for detecting laser light reflected off
the scanned bar code symbol and producing an electrical signal
D.sub.1 indicative of the detected intensity; a analog-to-digital
(A/D) conversion circuit 110 for converting analog scan data signal
D.sub.1 into a corresponding digital scan data signal D.sub.2; a
bar code presence detection circuit 111 for processing digital scan
data signal D.sub.2 in order to automatically detect the digital
data pattern of a bar code symbol on the detected object and
produce control activation signal A.sub.2=1; a third RC timing
network 112 for setting a timer T.sub.BCD in the bar code symbol
detection circuit; second control means 113, realized as a second
control circuit C.sub.2, for performing local system control
operations in response to the detection of the bar code symbol;
third control means 114, realized as third control module C.sub.3;
a range selection, circuit 115 for supplying range selection
signals to the object detection circuit; second control circuit
C.sub.2 and third control module C.sub.3; timers T.sub.2, T.sub.3,
and T.sub.4 identified by reference numerals 116, 117 and 118,
respectively; a symbol decoding module 119 for processing digital
scan data signal D.sub.2 so as to determine the data represented by
the detected bar code symbol, generate symbol character data
representative thereof, and produce activation control signal
A.sub.3 for use by third control module C.sub.3; a data packet,
synthesis module 120 for synthesizing a group of formatted data
packets for transmission to its mated base unit; and a data packet
transmission circuit 121 for transmitting the group of data packets
synthesized by the data packet synthesis module. As will be
described in greater detail hereinafter, second control circuit
C.sub.2 is capable of "overriding" (i.e., inhibit and/or enable)
first control circuit C.sub.1, whereas third control module C.sub.3
is capable of overriding first and second control circuits C.sub.1
and C.sub.2, respectively. As shown in FIG. 8, such control
override functions are carried out by the generation of control
override signals (i.e., C.sub.2/C.sub.1, C.sub.3/C.sub.2 and
C.sub.3/C.sub.1) transmitted between respective control structures.
Owing to the unique architecture of the control subsystem hereof,
the automatic bar code symbol reading device of the present
invention is capable of versatile performance and ultra-low power
operation. The structure, function and advantages of this control
subsystem architecture will become apparent hereinafter.
[0124] As shown in the schematic diagram of FIG. 8A, battery: power
supply unit 20 contained within the housing of the code symbol
reading device provides electrical power to the components
therewithin in accordance with a programmed mode of intelligent
operation. In the illustrative embodiment, battery power supply
unit 20 comprises a power supply distribution circuit 125,
replaceable or rechargeable batteries 126, and an automatic power
control circuit 130. In the illustrative embodiment, where;
rechargeable batteries are employed, the power supply circuit 20
further includes a secondary inductive coil 127, bridge rectifier
128 and voltage regulation circuit 129. Preferably, all of these,
subcomponents are contained within the hand-supportable housing of
the device, and are configured together as shown in FIG. 8A.
[0125] As illustrated in FIG. 8A, the function of second inductive
coil 128 is to establish an electromagnetic coupling with the
primary inductive coil contained in the base unit associated with
the bar code reading device whenever the device is supported if in
the recharging portion of the base unit. In this configuration,
electrical power is inductively transferred from the primary
inductive coil in the base unit to secondary inductive coil 127,
rectified by bridge rectifier 128, and filtered by voltage
regulation circuit 129 to provide a regulated DC power supply for
recharging rechargeable batteries 126.
[0126] As shown in FIG. 8A, automatic power control circuit 130 is
connected in series between rechargeable battery 126 and power
distribution circuit 125. The function of automatic power control
circuit 130 is to automatic control (i.e. manage) the availability
of battery power to electrically-active components within the bar
code symbol reading device when the device is operated in its
hands-on mode of operation (i.e. removed from the scanner support
stand) under a predefined set of operating conditions. Notably
while power distribution circuit 125 distributes electrical power
throughout the bar code symbol reading device by way of a power
distribution bus, automatic power control circuit 130 globally
enables consumption of electrical power (i.e. the product of
voltage and direct current) by the system components when
activated.
[0127] As shown in FIG. 8A, the automatic power control circuit 130
comprises a number of subcomponents, namely: a DC-to-DC voltage
converter 130A; a power commutation switch 130B; and a resettable
timer circuit 130C. The function of the DC-to-DC voltage converter
103A is to convert the voltage from battery power source 126 to +5
Volts, whereas the function of the power commutation switch 130B is
to selectively commute electrical power from the DC-to-DC converter
130A to the input port of the power distribution circuit 125. The
function of the resettable timer circuit 130C is to control the
power commutation circuit so that battery power is provided to the
power distribution circuit 125 in a power conserving manner without
compromising the performance of the bar code symbol reading system
in its various modes of operation.
[0128] In the illustrative embodiment, DC-to-DC converter 130A is
realized by configuring a low-voltage input, adjustable output
step-up DC-DC converter (e.g. such as the MAX777 IC chip by SLIM
Integrated Products) with an inductor (e.g. 22.0 microHenries) and
two capacitors, to produce a 5.0 Volt output voltage for use in the
bar code symbol reading device. As shown, resettable timer circuit
130C is realized by configuring a comparator circuit 130C1 (e.g. as
provided for example in the LM2903 IC chip by National
Semiconductor) with external resistors R1, R2, R3, R4 and R5 and
charging capacitor C1. The function of the resistors R3 and R5 is
to provide to one inputs of the comparator a positive reference
voltage (i.e. Vref) which is close in magnitude to the battery
voltage Vbattery, with resistor R4 being connected to the output of
the comparitor for hysteresis. The power control switch 130B is
realized by N-channel field effect transistor (FET), wherein the
source terminal is connected to the output port of the DC-to-DC
converter 130A, the drain terminal is connector is connected to the
input port of the power distribution circuitry 125, and the gate
terminal is connected to the output port of the comparitor
130C1.
[0129] In the illustrative embodiment, there are three different
power switching events which will reset the resettable timer
circuit 130C, cause the comparitor thereof to produce a high output
level and drive the N-channel FET into conduction. The first power
switching event comprises manually depressing power reset button
130D mounted on the exterior of the scanner housing. The second
power switching event comprises placing the handle portion of the
scanner housing within the recess of the scanner support stand
hereof, whereby Hall-effect sensor 100 within the handle of the
housing detects magnetic flux produced from permanent magnet 103
within the scanner support stand recess, as shown in FIG. 1E. The
third power switching event comprises successfully reading a bar
code symbol and producing activation signal A3=1.
[0130] In order that such power switching events will effectively
reset the resettable timer circuit 130C, a number of electrical
devices are connected to input port of the resettable timer circuit
130C, effectively realized by resistor R2. In particular, the "good
read" activation signal A3=1 produced by symbol decoding module 119
is provided to the base of a NPN transistor 130C2, which has its
collector terminal connected to one end of resistor R2 and its
emitter terminal connected to electrical ground. As shown, one
terminal of manually depressible power reset button 130D (e.g.
realized as a spring-biased push-type button switch) is connected
to the same end of resistor R2, to which the collector of NPN
transistor 130C2 is connected, while the other terminal of power
set button 130D is connected to electrical ground. Also, one
terminal of stand detector (e.g. Hall-effect sensor 100) is
connected to the same end of resistor R2, to which the collector of
NPN transistor 130C2 is connected, while the other terminal of the
Hall-effect sensor 100 is connected to electrical ground, as shown
in FIG. 8A.
[0131] Battery supply 126 aboard the scanning device is
automatically charged to its normal output voltage (i.e. Vbattery)
by way of battery recharging apparatus 127, 128 and 129. A
predetermined time duration .DELTA.T (e.g. 1 minute, preferably 5
minutes) after the occurrence of a power switching event, power
supply unit 20 attains its steady-state condition. At this state,
capacitor C1 charges through resistor R1, to a voltage above Vref.
This causes the output voltage of the capacitor 130C1 to drop to a
level which disables FET 130B, thereby disabling the supply of
battery power to power distribution circuit 125, and ultimately
disabling the scanning device. Upon the occurrence of any of the
above three "power switching" events described above, capacitor C1
quickly discharges through resistor R2 (i.e. R1>>R1), causing
the output voltage of capacitor 130C1 to go to a level which
enables FET 130B to supply battery power to the power distribution
circuitry 125, and thereby enabling the scanning device for the
predetermined time period (e.g. .DELTA.T greater than 1, preferably
5 minutes). This programmed duration of power supply provides a
time window .DELTA.T, within which the object detection circuit of
the system hereof can automatically detect an object within the
object detection field. Such power resetting operation does not,
however, initiate or otherwise cause laser scanning or bar code
symbol reading operations to commence or cease. Only the
introduction of an object into the object detection field (i.e.
when the resettable timer circuit 130C has been reset) can initiate
or otherwise cause laser scanning or bar code symbol reading
operations to commence.
[0132] A principal advantage of the power control scheme of the
present invention is that it provides automatic power conservation
in automatic code symbol reading applications, while minimally
impacting upon the diverse modes of automatic operation provided by
the system hereof. In particular, provided that the user reads at
least one bar code symbol within the predetermined time duration.
DELTA.T programmed into the bar code symbol reading device, there
is no need to reset the power control circuit hereor. Also, when
the hand-supportable housing of the device is placed (i.e.
supported) within the support recess 60 of scanner support portion
of the base unit, Hall-effect sensor 103 produces a stand detect
signal which continuously causes power control circuit 130 to
supply battery power from continuously recharging battery 126, to
the power distribution circuit 125, thereby enabling continuous
scanner operation in the hands-free mode of operation.
[0133] Range selection circuit 115 may include a manual switch
externally accessible to the housing, which the user can depress to
select long or short-range modes of object detection, bar code
presence detection and/or bar code symbol reading. Alternatively,
Range Selection Circuit 115 can be activated to a particular range
setting by symbol decoding module 119. In this mode of operation,
the range setting can be set by decoding a bar code symbol
predesignated to activate the long or short range modes of
detection, as the case may be.
[0134] In the illustrative embodiment of the present invention,
primary oscillator circuit 101, object detection circuit 107, first
control circuit C.sub.1, analog-to-digital conversion circuit 110,
bar code symbol detection circuit 111, and second control circuit
C.sub.2 are all realized on a single Application Specific
Integrated Circuit (ASIC) chip 133 using microelectronic circuit
fabrication techniques known in the art. In the illustrative
embodiment, the ASIC chip and associated circuits for laser
scanning and light detection and processing functions are mounted
on analog signal processing board 40. Symbol decoding module 119,
data packet synthesis module 120, timers T.sub.2, T.sub.3, T.sub.4,
and T5 and third control module C.sub.3 are realized using a single
programmable device, such as a microprocessor having accessible
program and buffer memory, and external timing circuitry,
collectively depicted by reference numeral 134 in FIG. 8. In the
illustrative embodiment, these components and devices are mounted
on the PC board 50. In the illustrative embodiment, when power
control switch 130 is in its reset (i.e. POWER ON) state, power
from battery power unit 126 is provided to first control circuit
C.sub.1, priffary, oscillator circuit 101 and IR object sensing
circuit 106 and object detection circuit 107 so as to enable their
operation, while only biasing voltages are provided to all other
system components so that they are each initially disabled from
operation. When power control switch 130 is in its POWER OFF state,
power from battery power unit 126 is not commuted to power
distribution circuit 125, and thus not provided to any components
in the system. As will be described in greater detail hereinafter,
provision of electrical power to all other system components occurs
under the management of the control architecture formed by the
interaction of distributed control centers C.sub.1, C.sub.2 and
C.sub.3.
[0135] As shown in FIG. 8, primary clock oscillator circuit 101
supplies a periodic pulsed signal to both the system override
signal detection circuit and the object detection circuit. In the
illustrative embodiment, the primary oscillation circuit is
designed to operate at a low frequency (e.g., about 1.0 Khz) and a
very low duty cycle (e.g., about 1.0%). The "ON" time for the
system override signal producing means and the IR object sensing
circuit is proportional to the duty cycle of the primary
oscillation circuit. This feature allows for minimal operating
current when the bar code symbol reading device is in the object
detection mode and also when the system override signal producing
device is activated (i.e., produces a system override signal).
[0136] As shown in FIG. 8B, primary oscillation circuit 101
comprises a Schmidtt trigger 142, invertors 143 and 144, and a NMOS
Field-Effect Transistor (FET) 145. As shown, the output of trigger
142 is connected to the inputs of both invertors 143 and 144. The
output of invertor 143 produces clock signal CLK which is provided
to system override signal detection circuit 100 and object
detection circuit 107. The primary oscillation circuit is connected
to first RC network 102 which comprises resistors R.sub.1 and
R.sub.2, and capacitor C.sub.1 configured as shown in FIG. 8B. The
function of the RC network 102 is to establish the duty cycle and
the oscillation period of the primary oscillator circuit. As shown,
two time constants (i.e., loads) are established by the network
using capacitor C.sub.1 and resistors R.sub.1 and R.sub.2. The RC
combination of R.sub.1 and C.sub.1 establishes the period of the
oscillator. The ratio of the R.sub.2 to R.sub.1 provides the duty
cycle of the oscillator. The value of R.sub.2 is approximately 100
times smaller than R.sub.1 to establish a 1.0% duty cycle. As shown
in the timing diagram of FIG. 8C, the clock signal CLK remains low
while the V.sub.1=1 signal ramps up. This ramp up time is the time
it takes for the capacitor C.sub.1 to charge through R.sub.1. The
clock signal CLK then goes HIGH for the shorter discharge time of
the capacitor through R.sub.2. By adjusting the duty cycle (i.e.,
increasing or decreasing the value of resistor R.sub.2), the
sensitivity of the object detection circuit can be tuned such that
it activates consistently at a specified distance from the light
transmission a window of the bar code symbol reading device.
[0137] In accordance with the present invention, the purpose of
object detection circuit 107 is to produce a first control
activation signal A.sub.1=1 upon determining that an object (e.g.,
product, document, etc.) is present within the object detection
field of the bar code symbol reading device, and thus at least a
portion of the scan field thereof. As illustrated in FIG. 8, the
object detection circuit is activated (i.e., enabled) by enabling,
signal E.sub.0 supplied from first control circuit C.sub.1, and the
object detection circuit provides the first control circuit C.sub.1
with first control activation signal A.sub.1=1 when an object
residing in the scan field is detected. In the illustrative
embodiment, an "active" technique of automatic object detection is
employed, although it is understood that "passive" techniques may
be used with acceptable results. As shown in FIG. 8, the object
detection means of the system comprises two major subcomponents,
namely object sensing circuit 106 and object detection circuit 107,
both of which are locally controlled by control circuit C.sub.1. In
the illustrative embodiment, object sensing circuit comprises an IR
LED 148 driven by an IR transmitter drive circuit 149, and an IR
phototransistor (or photodiode) 150 activated by an IR receive
biasing circuit 151. As shown in FIGS. 7D and 7F, these components
are arranged and mounted on PC board 41 so as to provide an object
detection field that spatially encompasses the laser scanning
plane, as described above. As shown in FIG. 8, the object detection
circuit 107 produces an enable signal IR DR which is provided to
the IR transmitter drive circuit 149. The signal produced from IR
phototransistor 151, identified as IR REC, is provided as input
signal to the object detection circuit 107 for signal processing in
a manner which will be described in detail below. In the
illustrative embodiment, infrared LED 148 generates a 900 nanometer
signal that is pulsed at the rate of the primary oscillation
circuit 101 (e.g., 1.0 KHZ) when the object detection circuit is
enabled by enable signal E.sub.0 produced from the first control
circuit C.sub.1. Preferably, the duty cycle of the primary
oscillation circuit 101 is less than 1.0% in order to keep the
average current consumption very low.
[0138] As shown in FIG. 3A, in particular, this pulsed optical
signal is transmitted from infrared LED 148 to broadly illuminate
the scan field. When an object is present within the object
detection portion of the scan field, a reflected optical pulse
signal is produced and focussed through focusing lens 153 onto
photodiode 150. The function of photodiode 150 is to receive (i.e.,
sense) the reflected optical pulse signal and, in response thereto,
produce a current signal IR REC.
[0139] As shown in FIG. 8D, produced current signal IR RE (is
provided as input to the current-to-voltage amplifier (e.g.,
transconductance amplifier) 155 in the object detection circuit,
and is converted into a voltage signal Vo. Within the object
detection circuit 107, the infra-red LED drive signal IR DR is
produced as the output of AND gate 157, whose inputs are enabling
signal E.sub.0 supplied from the first control circuit C.sub.1 and
the pulsed clock signal CLK supplied from the primary oscillation
circuit 101.
[0140] As shown in FIG. 8D, enabling signal E.sub.0 is also
provided to current-to-voltage amplifier circuit 155, and the
output voltage signal from AND gate 157 is provided as the second
input to the synchronous transmitter/receiver circuit 156. Notably,
the output voltage signal from AND gate 157 and the output voltage
signal V.sub.0 from the current-to-voltage amplifier correspond to
the IR pulse signal trains transmitted from and received by object
sensing circuit 106. The function of the synchronous
transmitter/receiver circuit is to cyclically compare the output
voltage signal from AND gate 157 and the output voltage signal
V.sub.0 from the current-to-voltage amplifier, and if these voltage
signals synchronously match each other for a minimum of three (3)
consecutive cycles of the primary oscillation circuit 101, then
synchronous transmitter/receiver circuit 156 produces as output, a
first control activation signal A.sub.1=1, indicative that an
object is present in the scan field of the bar code symbol reading
device. Conversely, whenever first control activation signal
A.sub.1=0 is produced, then this condition indicates that an object
is not present in the scan field.
[0141] Alternatively, the automatic bar code reading device of the
present invention can be readily adapted to sense ultrasonic energy
reflected off an object present within the scan field. In such an
alternative embodiment, object sensing circuit 106 is realized as
an ultrasonic energy transmitting/receiving mechanism. In the
housing of the bar code reading device, ultrasonic energy is
generated and transmitted forwardly into the scan field. Then,
ultrasonic energy reflected off an object within the object
detection field is detected adjacent to the transmission window
using an ultrasonic energy detector that produces an analog
electrical signal (i.e., UE REC) indicative of the detected
intensity of received ultrasonic energy. Preferably, a focusing
element is disposed in front of the energy detector in order to
effectively maximize the collection of ultrasonic energy reflected
off objects in the scan field. In such instances, the focusing
element essentially determines the geometrical characteristics of
the object detection field of the device. Consequently, the energy
focusing (i.e., collecting) characteristics of the focusing element
will be selected to provide an object detection field which
spatially encompasses at least a portion of the scan field. The
electrical signal produced from the ultrasonic-energy based object
sensing circuit is provided to object detection circuit 107 for
processing in the manner described above.
[0142] In the illustrative embodiment, object detection circuit 107
is provided with two different modes of detection, namely, a
long-range mode of object detection and a short-range mode of
object detection. As shown in FIGS. 8 and 8D, these modes are set
by range selection circuit 115 using mode enable signal R.sub.1.
When induced into the long-range mode of object detection, object
detection circuit 107 will generate first control activation signal
A.sub.1=1 whenever an object has been detected within the operative
range of the object detection field, independent of the particular
distance at which the object resides from the transmissive window.
When induced into the short-range mode of object detection, the
object detection circuit will generate first activation control
signal A.sub.1=1 only when an object is detected at a distance
within the short-range of the object detection field.
[0143] As schematically indicated in FIGS. 2 and 2A, the long-range
specification for object detection is preferably preselected to be
the full or entire range of sensitivity provided by
current-to-voltage amplifier (e.g., 0 to about 10 inches).
Preferably, the short-range specification for object detection is
preselected to be the reduced range of sensitivity provided by the
IR sensing circuit when mode enable signal E.sub.IRT=1 is provided
to the desensitization port of amplifier 155. In the illustrated
embodiment, the short-range of object detection is about 0 to about
3 inches or so to provide CCD-like scanner emulation. As will
become apparent hereinafter, the inherently limited depth and width
of field associated with the short-range mode of object detection
prevents laser scanning mechanism 108 from flooding the scan field
with laser scanning light and thus inadvertently detecting
undesired bar code symbols. Particular uses to which object
detection range selection can be put, will be described in greater
detail hereinafter.
[0144] As shown in FIG. 8D, the sensitivity (i.e., gain) of
current-to-voltage amplifier 155 is controlled by a sensitivity
control signal E.sub.IRT produced from range control signal
generating circuit 158. In the illustrative embodiment, the
sensitivity control signal E.sub.IRT 160 is produced by a
resistance network whose values are selected using an analog switch
that is responsive to a range select signal R.sub.1 produced by
range selection circuit 115. As such, the sensitivity of the
current-to-voltage amplifier is simply adjusted by selecting one of
two resistance values within the resistance network used to realize
range control signal generating circuit 158. The short range mode
of object detection is enabled by selecting a resistance value that
produces an amplifier gain that is lower than that produced during
the long-range mode, of object detection where detectable objects
can reside further away from the light transmission window of the
bar code symbol reading device.
[0145] In general, first control logic block C.sub.1 provides the
first level of system control. This control circuit activates the
object detection circuit 107 by generating enable signal E.sub.0=1,
it tactivates laser beam scanning circuit 108, photoreceiving
circuit 109 and A/D conversion circuit 110 by generating enable
signal E.sub.1=1, and it activates bar code symbol detection
circuit 111 by generating enable signal E.sub.2=1. In addition, the
first control circuit C.sub.1 provides control lines and signals in
order to control these functions, and provides a system override
function for the low power standby mode of the bar code symbol
reading device. In the illustrative embodiment, the specific
operation of first control circuit C.sub.1 is dependent on the
state of several sets of input signals (i.e., activation control
signal A.sub.0 and A.sub.1, and override signals C.sub.2/C.sub.1,
C.sub.3/C.sub.1-1 and C.sub.3/C.sub.1-2) and an internally
generated digital timer signal B. A preferred logic implementation
of the first control circuit C.sub.1 is set forth in FIGS. 8E and
8F. The functional dependencies among the digital signals in this
circuit are represented by the Boolean logic expressions set forth
in the Table of FIG. 8G, and therefore are sufficient to uniqutely
characterize the operation of first control circuit C.sub.1.
[0146] As shown in FIG. 8E, first control circuit comprises a pair
of logic invertors 161 and 162, a NAND gate 164, a NOR gate 165, an
AND gate 166, and a digital timer circuit 167 which produces as
output, a digital output signal B. As shown, digital timer circuit
167 comprises a flip-flop circuit 170, a NOR gate 171, a clock
divide circuit 173, a comparator (i.e., differential) amplifier
172, and a NPN transistor 174. As illustrated, activation control
signal A.sub.1 is provided to the CLK input of flip-flop 170 by
waly of invertor 161. The QNOT output of the flip-flop is provided
as one input to NOR gate 171, whereas the other input thereof is
connected to the CLK input of clock divide circuit 173 and the
output: of comparator amplifier 172. The output of the NOR gate is
connected to the base of transistor 174, while the emitter thereof
is connected to electrical ground and the collector is connected to
the negative input of comparator amplifier 172 as well as the
second timing network 105, in a manner similar to the
interconnection of first timing network 102 to primary oscillation
circuit 101. Also, the divided clock output (i.e., CLK/2048)
produced from clock divide circuit 173 is provided to the CL input
of flip-flop 170. As shown, the Q output of flip-flop 170 is
connected to the reset (RST) input of the clock divide circuit 173
as well as to one input of NAND gate 164, one input of NOR gate
165, and one input of AND gate 166. Notably, the Q output of the
flip-flop is the digital output signal B indicated in each of the
Boolean expressions set forth in the Table of FIG. 8G.
[0147] As shown in FIG. 8E, the override signal C.sub.2/C.sub.1
from second control circuit C.sub.2 is provided as the input to
invertor 162, whereas the output thereof is provided as the second
input to AND gate 166. The override signal C.sub.3/C.sub.1-1 from
third control module C.sub.3 is provided as the second input to
NAND gate 164, whereas the output thereof produces enable signal
E.sub.0 for activating the object detection circuit 107. The
override signal C.sub.3/C.sub.1=2 is provided to the second input
to NOR gate 165, whereas the output thereof produces enable signal
E.sub.1 for activating laser scanning and photoreceiving circuits
108 and 109 and A/D conversion circuit 110. The output of AND gate
166 produces enable signal E.sub.2 for activating bar code symbol
detection circuit 111.
[0148] Referring to FIG. 8E, the operation of digital timer circuit
will be described. The output voltage of comparator amplifier 172
keeps transistor 174 in its non-conducting state (i.e., OFF), via
NOR gate 171, thus allowing the external RC network 105 to charge
to capacity. When comparator input voltage Vx exceeds reference
voltage VCC/2, the comparator output voltage biases (i.e., switches
ON) transistor 174 so as to begin discharging the RC timing network
105, until input voltage Vx falls below reference voltage VCC/2
upon which the process repeats, thus generating a digital clock
oscillation at the comparator output. The timing cycle of digital
output signal B is initiated by a transition on the activation
control signal A, which toggles flip-flop 170. This toggling action
sets the digital output signal B to its logical HIGH state,
resetting clock divide circuit 173 and starting the digital clocks
oscillator described above by toggling the Q output of flip-flop
170. As shown in FIG. 8F, clock divide circuit 173 is constructed
by cascading eleven flip-flop circuits together in a conventional
manner. Each stage of the clock divider circuit divides the input
clock signal frequency by the factor 2. Thus the clock divider
circuit provides an overall division factor of 2048. When the clock
output CLK/2048 toggles, the flip-flop circuit is cleared thus
setting the digital signal B to logical LOW until the next pulse of
the activation control signal A.sub.1.
[0149] As reflected in the Boolean expressions of FIG. 8G, the
state of each of the enable signals E.sub.0, E.sub.1 and E.sub.2
produced by the first control circuit C.sub.1 is dependent on
whether the bar code symbol reading system is in its override state
of operation. To better, understand the operation of control
circuit C.sub.1, it is helpful to consider a few control strategies
preformed thereby.
[0150] In the override state of operation of the system, enable
signal E.sub.0 can be unconditionally set to E.sub.0=0 by the third
control circuit C.sub.3 setting override signal C.sub.3/C.sub.1=0.
Under such conditions, the object detection circuit is enabled.
Also, when the laser scanning and photoreceiving circuits are
activated (i.e., B=1) and override signal C.sub.3/C.sub.1-1=1, then
enable signal E.sub.0=1 and therefore the object detection circuit
is automatically deactivated. The advantage of this control
strategy is that it is generally not desirable to have both the
laser scanning circuit 108 and photoreceiving circuit 109 and the
object sensing circuit 105 active at the same time, as the
wavelength of the infrared LED 148 typically falls within the
optical input spectrum of the photoreceiving circuit 109. In
addition, less power is consumed when the object detection circuit
107 is inactive (i.e., disabled).
[0151] As illustrated in FIG. 8, laser scanning circuit 108
comprises a solid-state visible laser diode (VLD) 177 driver, by a
conventional driver circuit 178. In the illustrative embodiment,
the wavelength of visible laser light produced from the laser diode
is preferably about 670 nanometers. In order to repeatedly scan the
produced laser beam over the scanning volume, the rotating polygon
is rapidly accelerated to operating speed by motor 37 driven by a
conventional driver circuit 181, as shown. Stationary mirror 44
directs the laser beam from the laser diode to the rotating
polygon. To selectively activate both laser light source 38 and
motor 37, a laser diode and scanning motor enable signal E.sub.1
provided as input to driver circuits 178 and 181. When enable it
signal E.sub.1 is a logical "high" level (i.e., E.sub.1=1) a laser
beam is generated and projected through the light transmissive
window, when the projected laser beam is repeatedly scanned through
the scanning volume, and an optical scan data signal is thereby
produced off the object (and bar code) residing within the scanning
volume. When a laser diode and scanning motor enable signal E.sub.1
is a logical "low" (i.e., E.sub.1=0), there is no laser beam
produced, projected, or scanned across the scanning volume.
[0152] When a bar code symbol is present on the detected object at
the time of scanning, the visible laser beam is automatically
scanned across the bar code symbol within the 3-D scanning volume,
and incident laser light on the bar code symbol will be scattered
and reflected. This scattering/reflection process produces a laser
light return signal of variable intensity which represents a
spatial variation of light reflectivity characteristic of the
pattern of bars and spaces comprising the bar code symbol.
Photoreceiving circuit 109 detects at least a portion of the
reflected laser light of variable intensity and produces an analog
scan data signal Dindicative of the detected light intensity.
[0153] In the illustrative embodiment, photoreceiving circuit 109
generally comprises a number of components, namely: laser light
collection optics (i.e., stationary mirror array 38 and focusing
mirror 43) for focusing reflected laser light for subsequent
detection; photoreceiver 41 (e.g., a silicon photosensor) mounted
onto PC board 40, as shown in FIG. 5D, for detecting laser light
focused by the light collection optics; and frequency selective
filter 186A, mounted in front of photoreceiver 41, for transmitting
thereto only optical radiation having wavelengths up to a small
band above 670 nanometers.
[0154] In order to prevent optical radiation slightly below 670
nanometers from passing through light transmission aperture 12A and
entering the housing, the light transmissive window 68 realized as
a plastic filter lens is installed over the light transmission
aperture of the housing. This plastic filter lens has optical
characteristics which transmit only optical radiation from slightly
below 670 nanometers. In this way, the combination of plastic
filter lens 12 at the transmission aperture and frequency selective
filter 186A before photoreceiver 41 cooperate to form a narrow
band-pass optical filter having a center frequency f.sub.c=670
nanometers. By permitting only optical radiation associated with
the visible laser beam to enter the housing, this optical
arrangement provides improved signal-to-noise ratio for detected
scan data signals D.sub.1. This novel filtering optical arrangement
is disclosed in greater detail in copending application Ser. No.
08/439,224, supra.
[0155] In response to reflected laser light focused onto photo
receiver 41, photoreceiver 41 produces an analog electrical signal
which is proportional to the intensity of the detected laser light.
This analog signal is subsequently amplified by preamplifier 187 to
produce analog scan data signal D.sub.1. In short, laser scanning
circuit 108 and photoreceiving circuit 109 cooperate to generate
analog scan data signals D.sub.1 from the scan field, over time
intervals specified by first control circuit C.sub.1 during normal
modes of operation, and by third control module C.sub.3 during
"control override" modes of operation.
[0156] As illustrated in FIG. 8, analog scan data signal D.sub.1 is
provided as input to A/D conversion circuit 110, shown in FIG. 8H.
In a manner well known in the art, A/D conversion circuit 110
processes analog scan data signal D.sub.1 to provide a digital scan
data signal D.sub.2 which has a waveform that resembles a pulse
width modulated signal, where logical "1" signal levels represent
spaces of the scanned bar code and logical "0" signal levels
represent bars of the scanned bar code. A/D conversion circuit 110
can be realized using any conventional A/D conversion techniques
well known in the art. Digitized scan data signal D.sub.2 is then
provided as input to bar code presence detection circuit 111 and
symbol decoding module 119 for use in performing particular
functions required during the bar code symbol reading process of
the present invention.
[0157] The primary purpose of bar code presence detection circuit
111 is to determine whether a bar code is present in or absent from
the scan field, over time intervals specified by first control
circuit C.sub.1 during normal modes of operation and by third
control module C.sub.3 during control override modes of operation.
In the illustrative embodiment, bar code presence detection circuit
111 indirectly detects the presence of a bar code in the
narrowly-confined scanning volume 13 by detecting its bar code
symbol "envelope". In the illustrative embodiment, a bar code
symbol envelope is deemed present in the scanning volume upon
detecting a corresponding digital pulse sequence in digital signal
D.sub.2 that A/D conversion circuit 110 produces when
photoreceiving circuit 109 detects laser light reflected off a bar
code symbol scanned by the laser beam produced by laser beam
scanning circuit 108. This digital pulse sequence detection process
is achieved by counting the number of digital pulse transitions
(i.e., falling pulse edges) that occur in digital scan data signal
D.sub.2 within a predetermined time period T.sub.1 clocked by the
bar code symbol detection circuit. According to the laws of physics
governing the laser scanning operation, the number of digital
(pulse-width modulated) pulses detectable at photoreceiver 41
during time period T.sub.1 is a function of the distance of the bar
code from the light transmission window 12 at the time of scanning.
Thus a bar code symbol scanned at 6" from the light transmission
window will produce a larger number of digital pulses (i.e.,
digital count) at photoreceiver 41 during time period T.sub.1 than
will the same bar code symbol scanned at 3" from the light
transmission window.
[0158] In the illustrative embodiment, the bar code symbol
detection circuit 111 is provided with the capacity to detect the
presence of a bar code symbol in either the long or short range
portions of the scanning volume, as specified in FIGS. 3 and 3A.
This is achieved by counting the digital pulse transitions present
in digital scan signal D.sub.2 within predetermined time period
T.sub. and producing second control activation signal A.sub.2S
(i.e., A.sub.2S=1) when the counted number of pulse transitions
equals or exceeds a first prespecified digital pulse transition
count corresponding to a bar code symbol scanned in the short range
portion of the scan field, and producing second control activation
signal A.sub.2L (i.e., A.sub.2L=1) when the counted number of pulse
transitions equals or exceeds a second prespecified digital pulse
transition count corresponding to a bar code symbol scanned in the
long range portion of the scanning volume. As shown in FIG. 8, both
of these second control activation signals A.sub.2L and A.sub.2S
are produced and provided as input to second control circuit
C.sub.2. However, second control circuit C.sub.2 selectively
provides (e.g., gates) the second control activation signal that
corresponds to range-mode of operation selected by the user. When
the long range mode of operation has been selected by range
selection circuit 115, the device will automatically undergo a
transition from bar code presence detection state to bar code
symbol reading state upon receiving control activation signal
A.sub.2L=1. Similarly, when the short range mode of operation has
been selected by the range selection circuit 115, the device will
automatically undergo a transition from bar code presence detection
state to bar code symbol reading state upon receiving control
activation signal A.sub.2S=1.
[0159] In the illustrative embodiment, bar code symbol presence
detection circuit 111 comprises a digital pulse transition counter
190 for counting digital pulse transitions during time period
T.sub.1, and a digital clock circuit (i.e., T.sub.BCD circuit) 191
for measuring (i.e., counting) time period T.sub.BCD and producing
a count reset signal CNT RESET at the end of each such time period,
as shown in FIG. 8K. As shown in FIG. 8K, the function of digital
clock circuit 191 is to provide a time period T.sub.BCD (i.e., time
window subdivision) within which the bar code symbol detection
circuit attempts, repeatedly during time period T.sub.1, to detect
a bar code symbol in the scan field. In the preferred embodiment,
T.sub.BCD is about 0.1 seconds, whereas T.sub.1 is about 1.0
second. As shown in FIG. 8I, in order to establish such "bar code
search" time it subintervals within time period T. sub.1, the
digital clock circuit 191 generates the first count reset pulse
signal CNT RESET upon the detection of the first pulse transition
in digital scan data signal D.sub.2. The effect of this reset
signal is to clear or reset the digital pulse transition (falling
edge) counter. Then at the end of each time subinterval T.sub.BCD,
digital clock signal 191 generates another count reset pulse CNT
RESET to reset the digital pulse transition counter. If during time
window T.sub.1, a sufficient number of pulse transitions in signal
D.sub.2 are counted over a subinterval T.sub.BCD, then either
control activation signal A.sub.2L or A.sub.2S, will be set to "1".
In response to the detection of this condition, second control
circuit C.sub.2 automatically enables control activation C.sub.3 in
order to initiate a transition from the bar code symbol detection
state of operation to the bar code symbol reading state of
operation.
[0160] As shown in FIG. 8I, digital pulse transition counter 191 is
formed by wiring together a series of four flip-flop circuits 192
to 195, such that each flip flop divides the clock signal frequency
of the previous stage by a factor of 2. As indicated in the drawing
of FIG. 8I, the Q output of flip flops 192 to 194 represent the
binary digits 2, 4, 8, and 16 respectively, of a binary number
(i.e., counting) system. As shown, enable signal E.sub.2 from first
control circuit C.sub.1 is provided as input to NOR gate 197, while
the second input thereto is the counter reset signal CNT RESET
provided from the digital counter circuit 191. In order to reset or
clear the pulse transition counter circuit 190 upon the generation
of each CNT RESET pulse, the output of the NOR gate 197 is
connected to the clear line (CL) of each flip flop 192 to 195, as
shown.
[0161] As illustrated in FIG. 8, digital clock circuit 191
comprises a flip-flop circuit 198, a NOR gate 199, a clock divide
circuit 200, a comparator 201, and a NPN transistor 202. As
illustrated, digital scan data signal D.sub.2 is directly provided
to the CLK input of flip-flop 198. The QNOT output of the flip-flop
is provides as one input to NOR gate 199, whereas the Q output
thereof is connected to the CLK input of clock divide circuit 200
and the second input of NOR gate 197. The other input of NOR gate
199 is connected to the input line CLK of clock divide circuit 200
and to the output of comparator 201, as shown. The output of the
NOR gate is connected to the base of transistor 202, while the
emitter thereof is connected to electrical ground and the collector
is connected to the negative input of comparator 201 as well as to
the third timing network 112, in a manner similar to the
interconnection of the first timing network 102 to primary
oscillation circuit 101. As shown in FIG. 8J, clock divide circuit
200 is realized as series of five flip-flops 200A to 200E wired
together so as to divide digital clock input signal CLOCK by 32,
and be resettable by pulsing reset line RESET in a conventional
manner.
[0162] When an object is detected in the scan field, first control
circuit C.sub.1 produces enable signal E.sub.2=1 so as to enable
digital pulse transition counter 190 for a time duration of
T.sub.1. As shown, the digital scan data signal D.sub.2
(representing the bars and spaces of the scanned bar code) drives
the clock line of first flip flop 192, as well as the clock line of
flip flop 198 in the T.sub.BCD timer circuit. The first pulse
transition in digital scan data signal D.sub.2 starts digital timer
circuit 191. The production of each count reset pulse CNT RESET
from digital timer circuit 191 automatically clears the digital
pulse transition counter circuit 190, resetting it once again to
count the number of pulse transitions present in the incoming
digital scan data signal D.sub.2 over a new time subinterval
T.sub.BCD. The Q output corresponding to eight pulse transitions
counted during time period TBCD, provides control activation signal
A.sub.2 S for use during the short range mode of operation. The Q
output corresponding to sixteen pulse transitions counted during
time period T.sub.BCD, provides control activation signal A.sub.2L
for use during the long range mode of operation. When the presence
of a bar code in the scan field is detected, second activation
control signal A.sub.2L or A.sub.2S is generated, third control
circuit C.sub.3 is activated and second control circuit C.sub.2 is
overridden by third control circuit C.sub.3 through the
transmission of control override signals (i.e., C.sub.3/C.sub.2
inhibit and C.sub.3/C.sub.1 enable signals) Prom the third control
circuit C.sub.3.
[0163] As illustrated in FIG. 8L, second control circuit C.sub.2 is
realized using logic circuitry consisting of NAND gates 205 to 208,
invertors 209 and 210, NOR gates 211 to 213, NAND gates 214 and
215, AND gate 216, configured together as shown. As shown, second
control activation signals A.sub.2S. and A.sub.2L are provided to
the first inputs of NAND gates 214 and 215, respectively, whereas
the outputs of NOR gates 211 and 212 are provided to the second
inputs of NAND gates 214 and 215 respectively. The outputs of NAND
gates 214 and 215 are provided to the inputs of AND gate 216 and
the output thereof provides enable signal E.sub.3 for enabling
third control module C.sub.3.
[0164] As shown in FIG. 8L, the third control module C.sub.3
provides override signals C.sub.3/C.sub.2-1 and C.sub.3/C.sub.2-2
to the first and second inputs of NAND gate 205 and to the first
input of NAND gate 207 and the first input of NAND gate 208,
respectively. The range selection signal R produced from range
selection circuit 115 is provided as input to NAND gate 206. As
shown, output of NAND gate 205 is provided as the second input to
NAND gate 206. The output of NAND gate 206 is provided as the
second input to NAND gate 207 and the, second input to NAND gate
208. As shown in FIG. 8L, the output of NAND gate 207 is provided
as an input to NOR gate 211 and invertor 209, whereas the output of
NAND gate 208 is provided as inputs to NOR gates 211 and 212 and
invertor 210. The output of invertor 209 is provided as the other
input to NOR gate 212 and one input to NOR gate 213. The output of
invertor 210 is provided as another input to NOR gate 213, whereas
the output thereof provides control override signal
C.sub.2/C.sub.1. So configured, the combinational logic of the
second control circuit C.sub.2 maps its input signals to its output
signals in accordance with the logic table of FIG. 8M.
[0165] Upon entering the bar code symbol reading state, third
control module C.sub.3 provides override control signal
C.sub.3/C.sub.1 to first control circuit C.sub.1 and second control
circuit C.sub.2. In response to control signal C.sub.3/C.sub.1, the
first control circuit C.sub.1 produces enable signal E.sub.1=1
which enables scanning circuit, 109 photo-receiving E circuit 109
and A/D conversion circuit 110. In response to control signal
C.sub.3/C.sub.2, the second control circuit C.sub.2 produces enable
signal E.sub.2=0, which disables bar code symbol detector circuit
111. Thereafter, third control module C.sub.3 produces enable
signal E.sub.4 to enable symbol decoding module 119. In response to
the production of such signals, the symbol decoding module decode
processes, scan line by scan line, the stream of digitized scan
data contained in signal D.sub.2 in an attempt to decode the
detected bar code symbol within the second predetermined time
period T.sub.2 established and monitored by the third control
module C.sub.3. If the symbol decoding module 119 successfully
decodes the detected bar code symbol within time period T.sub.2,
then symbol character data D.sub.3 (representative of the decoded
bar code symbol and typically in ASCII code format) is produced.
Thereupon symbol decoding module 119 produces and provides the
third control activation signal A.sub.3 to the third control module
C.sub.3 in order to induce a transition from the bar code symbol
reading state to the data packet transmission state. In response
thereto, a two distinct events occur. First the third control
module C.sub.3 produces and provides enable signal E.sub.5 to data
packet synthesis module 120. Secondly, symbol decoding module 119
stores symbol character data D.sub.3 in a memory buffer associated
with data packet synthesis module 120.
[0166] In the illustrative embodiment, symbol decoding module 119,
data packet synthesis module 120, and timers T.sub.2, T.sub.3,
T.sub.4 and T.sub.5 are each realized using programmed
microprocessor and accessible memory 134. Similarly, third control
module C.sub.3 and the control functions which it performs at
Blocks to GG in FIGS. 13A and 13C, are realized as a programming
implementation using techniques well known in the art.
[0167] The function of data packet synthesis module 120 is to use
the produced symbol character data to synthesize a group of data
packets for subsequent transmission to its assigned base unit by
way of data packet transmission circuit 121.
[0168] In the illustrative embodiment, each synthesized data packet
is formatted as shown in FIG. 8N. In particular, each data packet
in each data packet group comprises a number of data fields,
namely: Start of Packet Field 220 for containing a digital code
indicating the beginning of the transmitted data packet;
Transmitter Identification Number Field 221 for containing a
digital code representative of the Transmitting Bar Code Symbol
Reader; Data Packet Group Number Field 222 for containing a digital
code (i.e., a first module number) assigned to each particular data
packet group being transmitted; Data Packet Transmission No. Field
223 for containing a digital code (i.e., a second module number)
assigned to each data packet in each data packet group being
transmitted; Symbol Character Data Field 224 for containing digital
code representative of the symbol character data being transmitted
to the base unit; Error Correction Code Field 225 for containing a
digital error correction code for use by the receiving base unit to
determine if error in data packet transmission has occurred; and
End of Packet Field for 226 for containing a digital code
indicating the end of the transmitted data packet.
[0169] After the data packet synthesis module synthesizes a group
of data packets as described above, the third control module
C.sub.3 provides enable signal E.sub.7 to data packet transmission
circuit 121. As illustrated in FIG. 9, the data packet transmission
circuit comprises a carrier signal generation circuit 230, a
carrier signal frequency modulation circuit 231, a power amplifier
232, a matching filter 233, and a quarterwave (1/4) transmitting
antenna element 234. The function of the carrier signal generation
circuit 2303 is to generate a carrier signal having a frequency in
the RF region of the electromagnetic spectrum. In the illustrative
embodiment, the carrier frequency is about 912 Mhz, although it is
understood that this frequency may vary from one embodiment of the
present invention, to another embodiment thereof. As the carrier
signal is being transmitted from transmitting antenna 234,
frequency modulation circuitry 231 modulates the instantaneous
frequency of the carrier signal using the digital data sequence
(i.e., digital data stream) 235 constituting the group of data
packets synthesized by the data packet synthesis module 120. The
function of the power amplifier is to amplify the power of the
transmitted modulated carrier signal so that it may be received by
a base unit of the present invention located within a predetermined
data transmission range (e.g., from about 0 to about 30 feet).
[0170] In general, each base unit of the present invention performs
a number of functions. First, the base unit receives the modulated
carrier signal transmitted from a hand-supportable bar code symbol
reading device within the data reception range of the base unit.
Secondly, the base unit demodulates the received carrier signal to
recover the data packet modulated thereunto during signal
transmission. Thirdly, the base unit analyzes each of the recovered
data packets to determine whether the received carrier signal was
transmitted from a hand-supportable bar code symbol reading device
preassigned to the receiving base unit. Fourthly, the base unit
recovers the symbol character data from at least one data packet in
a transmitted group of data packets, and ascertaining the
reliability of the recovered symbol character data. Fifthly, the
base unit generates an acoustical acknowledgement signal SACK that
can be audibly perceived by the operator of the transmitting bar
code symbol reading device while located in the data reception
range of the base unit. Finally, the base unit transmits the
received symbol character data to a host computer system or like
device. Each of these functions will be described in greater detail
during the detailed description of the Main System Control Routine
set forth in FIGS. 13A to 13C.
[0171] In order to better understand the functions performed by the
bar code symbol reading device and base unit of the present
invention, it will be helpful to first describe the principles
underlying the data communication method of the present invention,
and thereafter discuss the role that the base unit plays in
carrying out this communication method.
[0172] In general, one or more bar code symbol reading devices can
be mated (i.e. registered or assigned) to operate with a single
base unit 3. In a first illustrative embodiment of the present
invention, each bar code symbol reading device is a (resultant)
system of bar code symbol reading subsystems installed in physical
proximity with each other. Typically, each system is a point of
sale (POS) station comprising (i) a host computer system interfaced
with a base unit of the present invention and (ii) an automatic
hand-supportable bar code symbol reading device preassigned to one
of the base units. In such an illustrative arrangement, each bar
code symbol reading device is mated (i.e. registered or associated)
with a single base unit by storing a unique, preassigned
"Transmitter Identification Code" in a memory device within the
assigned base unit during a set-up procedure.
[0173] In the illustrative embodiment, the carrier frequency of the
data packet transmitter in each bar code symbol reading device is
substantially the same for all bar code symbol reading devices in
the resultant system. Also, the data packet transmission range of
each bar code symbol reading device will be substantially greater
than the distance between each bar code symbol reading device and a
neighboring base unit to which the bar code symbol reading unit is
not assigned. Consequently, under such operating conditions, at any
instance in time, any base station in the resultant system may
simultaneously receive two or more packet modulated carrier signals
which have been transmitted from two or more bar code symbol
reading devices being used in the resultant system. These bar code
symbol reading devices may include the bar code symbol reading
device preassigned to the particular base unit as well as
neighboring bar code symbol reading devices. Thus due to the
principles of data packet transmission of present invention, there
exists the possibility that any particular base unit may
simultaneously receive two or more different data packets at any
instant in time, thereby creating a "packet interference"
situation.
[0174] In order to ensure that each base unit in the resultant
system is capable of receiving at least one data packet from a data
packet group transmitted by its preassigned bar code symbol reading
device (i.e., without risk of interference from neighboring bar
code symbol reading device transmitters), the unique "data packet
group" transmission scheme shown in FIG. 10 is employed. As shown,
upon the successful reading of a first bar code symbol and the
production of its symbol character data D.sub.3, data packet
synthesis module 120 aboard the bar code symbol reading device
automatically produces a first (i.e., N=1) group of (three) data
packets, each having the packet format shown in FIG. 9. Thereafter,
the data packet transmission circuit 121 uses the digital data bit
stream, representative of the synthesized data packet group, to
modulate a carrier signal transmitted from the hand-supportable bar
code symbol reading device.
[0175] In the illustrative example shown FIG. 10, only the second
and third data packets of the group sent over the modulated carrier
signal are shown as being received by the preassigned base unit. As
shown in this drawing, the base unit transmits the recovered symbol
character data D.sub.3 to its host computer system, upon receiving
the second data packet in the transmitted group of data packets.
Thereafter, the base unit produces an acoustical acknowledgement
signal S.sub.ACK of sufficient intensity that it can be easily
heard by the operator of the bar code symbol reading device that
transmitted the received data packet. The function of the
acoustical acknowledgment signal is to provide the operator with an
audible acknowledgement that the symbol character data D.sub.3
(associated with the recently read bar code symbol) has been
received by the base unit and transmitted to its host computer
system for processing and or subsequent storage. Notably, while the
third data packet N.sub.3 is also received by the base unit, the
available acknowledgement signal S.sub.ACK and symbol character
data transmission is not produced as packet N.sub.3 contains
redundant information already received by the second packet N.sub.2
of the same group.
[0176] In the preferred embodiment, the pitch of the transmitted
acoustical acknowledgement signal S.sub.ACK is uniquely specified
and assigned to a particular bar code symbol reading unit. This way
the operator of each bar code symbol reading (sub) system can
easily recognize (i.e., discern) the audible acoustical
acknowledgement signal produced from the base unit preassigned to
his or her bar code symbol reading device. At the same time, this
pitch assigmnent scheme allows each operator to ignore audible
acoustical acknowledgment signals produced from neighboring base
units not mated with his or her portable bar code symbol reading
device. If after reading a bar code symbol, the operator does not
see the visual "good read" indication light on its device "flash"
or "blink" and immediately thereafter hear its preassigned
acoustical acknowledgement signal emanate from its base unit, then
the operator is implicitly informed that the symbol character data
of the read bar code symbol was not successfully received by the
base unit. In response to such an event, the operator simply
rereads the bar code symbol and awaits to hear the acoustical
acknowledgment signal emanating from the base unit.
[0177] Notably, it may even be desirable in some operating
environments to produce acoustical acknowledgement signals in the
form of a unique series of notes preassigned to a bar code symbol
reading device and its "mated" base unit. The pitch or note
sequence assigned to each mated base unit and bar code symbol
reading device can be stored in a memory (e.g., EPROM) realized in
the base unit, and can be programmed at the time of system set-up
and modified as required. Preferably, each pitch and each note
sequence is selected so that it can be readily distinguished and
recognized by the operator to which it is uniquely directed.
[0178] Also shown in FIG. 10 is the case where the bar code symbol
reading device reads a second bar code symbol and then transmits a
second (N=2) group of data packets. However, due to interference
only the third data packet in the second transmitted group of data
packets is received at the respective base unit. Despite such group
transmission errors (e.g., due to channel corruption or non-radio
transmissive obstructions), the base unit as shown is nevertheless
able to recover the transmitted symbol character data. Upon
receiving the third data packet, recovering the packaged symbol
character data and transmitting the same to the host computer
system, the bar code symbol reading device generates an acoustical
acknowledgement signal having a pitch or note sequence that the
operator can hear and recognize as an indication that the data
packet reception was successful.
[0179] In FIGS. 11 and 12, the data packet transmission and
reception scheme of the present invention is shown for the case of
three station system. In the best case scenario shown in FIG. 11,
the group of data packets transmitted from each bar code symbol
reading device is transmitted at a time when there are no
neighboring bar code symbol reading devices transmitting data
packets. This case will occur most frequently, as the total
transmission times for each group of data packets is selected to be
substantially smaller than the random time durations lapsing
naturally between adjacent data packet transmissions from
neighboring bar code symbol reading devices. This fact is
illustrated in FIG. 11, in which (i) a group of data packets from
bar code reading device No. 1 are transmitted between adjacent
groups of data packet transmitted from bar code symbol reading
devices Nos. 2, 3 and 4 without the occurrence of data packet
interference (i.e., collision). In most instances, the time delay
between consecutive groups of data packets transmitted from any
particular bar code symbol reading device, will be sufficient to
permit a neighboring bar code symbol reading device to transmit at
least one data packet to its base unit without the occurrence of
data packet interference.
[0180] In accordance with the data transmission scheme of the
present invention, data packet interference is minimized by the
random presence of interference-free time slots, during which a
transmitted data packet can be received at its respective base unit
without neighboring packet interference. However, the present
invention employs additional measures to further reduce the
likelihood of data packet interference. Such measures are best
appreciated when considering a high-density data packet
transmission environment, in which a number of closely situated
neighboring bar code symbol readers are each attempting to transmit
a group of data packets to its preassigned base unit. In general,
such operating conditions would present a worst case scenario for,
the data packet transmission scheme of the present invention.
[0181] In the worst case scenario shown in FIG. 12, each of the
four neighboring bar code symbol reading devices is assumed to
consecutively read two bar code symbols and simultaneously begin
the transmission of the first data packet in the first group of
data packets corresponding to the first read bar code symbol. As
mentioned above, each data packet is formatted essentially the same
way, has substantially the same packet width, and is transmitted on
a carrier signal having a frequency which is substantially the same
as all other carrier signals transmitted throughout the system. In
accordance with the principles of the present invention, the data
packet transmission circuit 121 in each bar code symbol reading
device is preprogrammed to transmit adjacent data packets with a
different "time delay", as shown in FIG. 12. This condition is
achieved throughout the resulting system by assigning a different
Packet Time Delay to each having a different Transmitter
Identification Number, and then programming the bar code symbol
reading device with the preassigned Packet Time Delay parameter. As
illustrated in FIG. 12, the value of the Packet Time Delay
parameter programmed in each bar code symbol reading device is
selected so that, when the neighboring bar code symbol reading
devices simultaneously transmit groups of data packets, each base
unit in the resulting system is capable of receiving at least one
data packet (in a group thereof) that has been transmitted from its
preassigned bar code symbol reading device. In general, the data
packet delay scheme of the present invention involves selecting and
programming the Packet Time Delay parameter in each bar code symbol
reading device so that each base unit is periodically provided a
vacant time slot, during which one transmitted data packet in each
group thereof can be received free of "data packet interference",
as shown in FIG. 12. The advantage of providing a packet time delay
among the data packets of each transmitted group thereof is that
rereading and retransmission of bar code symbols is effectively
minimized under the data packet transmission scheme of the present
invention.
[0182] Having described the detailed structure and internal
functions of automatic bar code symbol reading device of the
present invention, the operation of the control system thereof will
now be described while referring to the system block diagram shown
in FIG. 8 and control Blocks A to GG in FIGS. 13A to 13C.
[0183] Beginning at the START block of Main System Control Routine
and proceeding to Block A of FIG. 13A, the bar code symbol reading
system is "initialized". This initialization step involves,
activating system override circuit 100, first control circuit
C.sub.1 and oscillator circuit 101. It also involves deactivating
(i.e., disabling): (i) all external system components except the
range selection circuit 115 and system override signal producing
means 103 (i.e., infrared sensing circuit 105, laser scanning
circuit 108, and photoreceiving circuit 109); (ii) all subcircuits
aboard ASIC chip 133 not associated with the system override
circuit 100, such as object detection circuit 107, A/D conversion
circuitry 110, second control circuit C.sub.2 and bar code presence
detection circuit 111; and (iii) third control module 114, symbol
decoding module 119 and data packet synthesis module 120. In
addition, all timers T.sub.1, T.sub.2, T.sub.3, T.sub.4, and
T.sub.5 are reset to t=0.
[0184] Proceeding to Block B in FIG. 13A, the first control circuit
C.sub.1 checks to determine whether it has received control
activation signal A.sub.0=1 from system override detection circuit
100. If this signal is received, then the first control circuit
C.sub.1 returns to Block A. If control activation signal A.sub.0=1
is not received, then at Block C the first control circuit C.sub.1
activates (i.e., enables) the object detection circuit by producing
E.sub.0. At Block D, the object detection circuit receives either
the long range mode selection signal or the short range mode
selection signal produced by the range selection circuit 115 and
sets the appropriate sensitivity level of the circuit. At Block E,
the first control circuit C.sub.1 determines whether it has
received control activation signal A.sub.1=1, indicating that an
object has been detected within the selected range of the scan
field. If this control activation signal is not received, then at
Block F the first control circuit C.sub.1 determines whether its
has received control activation signal A.sub.0=1. If the first
control circuit C.sub.1 has received control activation signal
A.sub.0=1, then the control system returns to Block A in FIG. 13A,
as shown. If the first control circuit C.sub.1 has not received
control activation signal A.sub.0=1, then the control system
returns to Block E, as shown.
[0185] If at Block E the first control circuit C.sub.1 has received
first control activation signal A.sub.1=1, then at Block G the
first control circuit C.sub.1 (i) deactivates (i.e., disables) the
object sensing circuit and the object detection circuit using
disabling signal E.sub.0=0, (ii) activates (i.e., enables) laser
scanning circuit 108, photoreceiving circuit 109 and A/D signal
conversion circuit 110 using enable signal E.sub.1=1, (iii)
activates bar code detection circuit 111 and second control circuit
C.sub.2 using enable signal E.sub.2=1, and (iv) starts timer
T.sub.1 maintained in the first control circuit C.sub.1. This
permits the bar code symbol reading device to collect and analyze
scan data signals for the purpose of determining whether or not a
bar code is within the scan field. If at Block H the second control
circuit C.sub.2 does not receive control activation signal
A.sub.2S=1 or A.sub.2L=1 from the bar code detection circuit within
time period T.sub.1, indicating that a bar code symbol is detected
in the selected range of the scan field, then the control system
returns to Block A thereby returning system control to the first
control unit C.sub.1, as shown in FIG. 13A. If at Block H the bar
code symbol detection circuit 111 provides the second control
circuit C.sub.2 with control activation signal A.sub.2S=1 or
A.sub.2L=1, as the case may be, then second control circuit C.sub.2
activates (i.e., enables) third control module C.sub.3 (i.e.,
microprocessor 134) using enable signal E.sub.3=1.
[0186] At Block J, the third control module C.sub.3 polls (i.e.,
reads) the parameter R set by range selection circuit 115 and sets
a range limit flag in the symbol decoding module 119. At Block K
third control module C.sub.3 activates the symbol decoding module
119 using enable signal E.sub.4, resets and restarts timer T.sub.2
permitting it to run for a second predetermined time period (e.g.,
0<T.sub.2<1 second), and resets and restarts timer T.sub.3
permitting it to run for a third predetermined time period (e.g.,
0<T.sub.3<5 seconds). At Block L the third control module
checks to determine whether control activation signal A.sub.3=1 is
received from the symbol decoding module 119 within T.sub.2=1
second, indicative that a bar code symbol has been successfully
read (i.e., scanned and decoded) within the allotted time period.
If control activation signal A.sub.3=1 is not received within the
time period T.sub.2=1 second, then at Block M third control module
C.sub.3 checks to determine whether control activating signal
A.sub.2=1 is received. If a bar code symbol is not detected, then
the control system returns to Block A, causing a state transition
from bar code reading to object detection. However, if at Block M
the third control module C.sub.3 receives control activation signal
A.sub.2=1, indicative that a bar code once again is within the scan
field, then at Block N the third control module C.sub.3 checks to
determine whether time period T.sub.3 has elapsed. If it has, then
the control system returns to Block A. If, however, time period
O.ltoreq.T.sub.3.ltoreq.5 seconds has not elapsed, then at Block K
the third control module C.sub.3 resets and restarts timer T.sub.2
to run once again for a time period O.ltoreq.T.sub.2.ltoreq- .1
second, while T.sub.3 continues to run. In essence, this provides
the device at least another opportunity to read a bar code present
within the scan field when the control system is at control Block
L. During typical bar code reading applications, the control system
may progress through the control loop defined by Blocks K-L-M-N-K
several times before a bar code symbol in the scan field is read
within the time period allotted by timer T.sub.3.
[0187] Upon receiving control activation signal A.sub.3=1 from
symbol decoding module 119, indicative that a bar code symbol has
been successfully read, the control system proceeds to Block O in
FIG. 13B. At this stage of the system control process, the third,
control module C.sub.3 continues activation of laser scanning
circuit 108, photoreceiving circuit 109, and A/D conversion circuit
110, while deactivating symbol decoding module 119 and commencing
activation of data packet synthesis module 120. While the laser
beam is continuously scanned across the scan field, the operations
at Blocks P to V described below, are carried out in a high speed
manner under the orchestration of control module C.sub.3.
[0188] As indicated at Block P, data packet synthesis module 120
first sets the Packet Number to "1", and increments the Packet
Group Number from the previous number. Preferably, the data packet
synthesis module keeps track of (i.e., manages) the "Packet Number"
using a first modulo-N counter realized by programmable
microprocessor 134, while it manages the "Packet Group Number"
using a second modulo-M counter also realized by programmed
microprocessor 134. In the illustrative embodiment, the first
modulo counter has a cyclical count range of N=2 (i.e., 0, 1, 2, 0,
1, 2, . . . ), whereas the second modulo counter has a cyclical
count range of M=10 (i.e., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 1, 2, .
. . ). At Block Q, the data packet synthesis module synthesizes or
constructs a data packet having a packet format as shown in FIG. 9,
i.e., consisting of symbol character data, a Transmitter
Identification Number, a Packet Number, a Packet Group Number,
check character, and Packet Start and End (i.e., framing)
Characters. After the data packet has been formed and the digital
data sequence constituting the same is buffered, the third control
module C.sub.3 activates at Block R the data packet transmission
circuit. Thereafter at Block S, the data packet synthesis module
outputs the buffered digital data sequence (of the first
synthesized data packet of the group) to the data packet
transmission circuit, which uses the digital data sequence to
modulate the frequency of the carrier signal as it is being
transmitted from the bar code symbol reading device, to its mated
base unit, as described hereinabove, and then automatically
deactivates itself to conserve power.
[0189] At Block T, the third control module C.sub.3 determines
whether the Packet Number counted by the first module counter is
less than "3". If the Packet Number of the recently transmitted
data packet is less than "3", indicative that at most only two data
packets in a specific group have been transmitted, then at Block U
the data packet synthesis module 120 increments the Packet Number
by +1. At Block V, the third control module then waits for a time
delay T.sub.5 to lapse prior to the control system returning to
Block Q, as shown in FIG. 13B. Notably, the occurrence of time
delay T.sub.5 causes a delay in transmission of the next data
packet in the data packet group. As illustrated in FIG. 12, the
duration of time delay T.sub.5 is a function of the (last two
digits of the) Transmitter Numbers of the current data packet
group, and thus is a function of the bar code symbol reading device
transmitting symbol character data to its mated base unit. For the
case of three data packet groups, time delay T5 will occur between
the transmission of the first and second data packets in a packet
group and between the transmission of the second and third data
packets in the same packet group.
[0190] Returning to Block Q, the data packet synthesis module
synthesizes or constructs the second data packet in the same data
packet group. After the second data packet has been formed and the
digital data sequence constituting the same is buffered, the third
control module C.sub.3 reactivates at Block R the data packet
transmission circuit. Thereafter at Block S, the data packet
synthesis module outputs the buffered digital data sequence (of the
second synthesized data packet) to the data packet transmission
circuit, which uses the digital data sequence to modulate the
frequency of the carrier signal as it is being transmitted from the
bar code symbol reading device, to its mated base unit, and
thereafter automatically deactivates itself. When at Block T third
control module C.sub.3 determines that the Packet Number is equal
to "3", the control system advances to Block W in FIG. 13C.
[0191] At Block W in FIG. 13C, the third control module C.sub.3
continues activation of laser scanning circuit 108 photoreceiving
circuit 109, and A/D conversion circuit 110 using control override
signals C.sub.3/C.sub.1, and deactivates symbol decoding module
119, data packet synthesis module 120 and the data packet
transmission circuit 121 using disable signals E.sub.4=0, E.sub.5=0
and E.sub.6=0, respectively. Then at Block X the third control
module C.sub.3 determines whether control activation signal
A.sub.1=1, indicating that an object is present in the selected
range of the scan field. If this control activation signal is not
provided to the third control module C.sub.3 then the control
system returns to Block A, as shown. If control activation signal
A.sub.1=1 is received, then at Block Y the third control module
C.sub.3 reactivates the bar code symbol detection circuit using
override signal C.sub.3/C.sub.2, and resets and restarts timer
T.sub.3 to start running over its predetermined time period, i.e.,
0<T.sub.3<5 seconds, and resets and restart timer T.sub.4 for
a predetermined time period 0<T.sub.4<3 seconds.
[0192] At Block Z in FIG. 13C, the third control module C.sub.3
then determines whether control activation signal A.sub.2=1 is
produced from the bar code symbol detection circuit 111 within time
period T.sub.4, indicating that a bar code symbol is present in the
selected range of the scan field during this time period. If this
signal is not produced within time period T.sub.4, then at Block AA
the third control module C.sub.3 deactivates the bar code symbol
detection circuit using override signal C.sub.3/C.sub.2, and
reactivates the bar code symbol decoding module 119 using enable
signal E.sub.4=1. At Block BB, the third control module C.sub.3
resets and restarts timer T.sub.2 to run over its predetermined
time period, i.e., 0<T.sub.2<1 second. At Block CC the third
control module C.sub.3 determines whether control activation signal
A.sub.3=1 is produced by the symbol decoding module within time
period T.sub.2, indicating that the detected bar code symbol has
been successfully decoded within this time period. If this control
activation signal is not produced within time period T.sub.2, then
at Block DD the third control module C.sub.3 determines whether
control activation signal A.sub.2=1 is being produced from the bar
code symbol detection circuit, indicating that either the same or
another bar code symbol resides within the selected range of the
scan field. If control activation signal A.sub.2=1 is not being
produced, then the control system returns to Block A, as shown.
However, if this control signal is being produced, then at Block EE
the third control module C.sub.3 determines whether or not timer
T.sub.3 has lapsed, indicating that time window to read a bar code
symbol without redetecting the object on which it is disposed, is
closed. When this condition exists, the control system returns to
Block BB FIG. 13A. However, it time remains on timer T.sub.3, then
at Block A in the third control module C.sub.3 resets and restarts
timer T.sub.2 and returns to Block CC. As mentioned above, the
control system may flow through the control loop defined by Blocks
BB-CC-DD-EE-BB a number of times prior to reading a bar code within
time period T.sub.3.
[0193] When the symbol decoding module produces control activation
signal A.sub.3=1 within time period T.sub.2, the third control
module C.sub.3 determines at Block FF whether the decoded bar code
symbol is different from the previously decoded bar code symbol. If
the decoded bar code symbol is different than the previously
decoded bar code symbol, then the control system returns to Block 0
in FIG. 13B. If the currently decoded bar code symbol is not
different than the previously decoded bar code symbol, then the
third control module C.sub.3 determines whether timer T.sub.3 has
lapsed. If the timer T.sub.3 has not lapsed, then the control
system returns to Block BB and reenters the control flow defined at
Blocks BB through GG, attempting once again to detect and read a
bar code symbol on the detected object. However, if at Block GG
timer T.sub.3 has lapsed, then the control system returns to Block
A in FIG. 13A.
[0194] Having described the operation of the illustrative
embodiment of the automatic hand-supportable bar code reading
device of the present invention, it will be helpful to describe at
this juncture the various conditions which cause state transitions
to occur during its operation. In this regard, reference is made to
FIG. 14 which provides a state transition diagram for the it
illustrative embodiment.
[0195] As illustrated in FIG. 14, the automatic hand-supportable
bar code reading device of the present invention has four basic
states of operation namely: object detection, bar code symbol
presence detection, bar code symbol reading, and symbol character
data transmission/storage. The nature of each of these states has
been described above in great detail.
[0196] Transitions between the various states are indicated by
directional arrows. Besides each set of directional arrows are
transition conditions expressed in terms of control activation 11
signals (e.g., A.sub.1, A.sub.2S or A.sub.2L and A.sub.3, and where
appropriate, state time intervals (e.g., T.sub.1, T.sub.2, T.sub.3,
T.sub.4, and T.sub.5) Conveniently, the state diagram of FIG. 14
expresses most simply the four basic operations occurring during
the control flow within the system control program of FIGS. 13A to
13C. Significantly, the control activation signals A.sub.1,
A.sub.2S A.sub.2L and A.sub.3 in FIG. 14 indicate which events
within the object detection and/or scan fields can operate to
effect a state transition within the allotted time frame(s), where
prescribed.
[0197] Referring now to FIGS. 15 to 15C, the base unit of the
illustrative embodiment of the present invention will be described
in greater detail.
[0198] In order to perform the data packet reception, processing,
retransmission, and acknowledgement functions of base unit 3
described above, a circuit board 270 is mounted within the interior
volume of support stand portion 14. In the illustrated embodiment,
PC board 270 is populated with electronic circuitry and devices for
realizing each of the functions represented by the block shown in
the system diagram of FIG. 16. As shown in FIG. 15A, flexible
communication and power supply cables 7 and 8 are routed through
aperture 271 formed in the lower portion of side wall of the
support frame, and connect to the electronic circuitry on PC board
270.
[0199] In FIG. 16, the system architecture of base unit 3 is
schematically represented. As shown, base unit 3 comprises a number
hardware and software components, namely: a power supply circuit
273; a receiving antenna element 274; an RF carrier signal receiver
circuit 275 base unit identification number storage unit 276; a
data packet storage buffer 277; a base unit system controller 278;
a data packet frame check module 279; a transmitter number
identification module 280; a data packet number identification
module 281; a symbol character data extractions module 282; a data
format conversion module 283; a serial data transmission circuit
284; and an acoustical acknowledgement signal generation circuit
285. In the illustrative embodiment, a programmed microprocessor
and associated memory (i.e., ROM and RAM), indicated by reference
numeral 286, are used to realize the base unit system controller
278 and each of the above-described data processing modules 277 to
283. The details of such a programming implementation are known by
those with ordinary skill in the art to which the present invention
pertains.
[0200] As shown in FIG. 16, receiving antenna element 274 is
electrically coupled to an input signal port of radio receiver
circuit 275 in a conventional manner. In general, the function of
radio receiver circuit 275 is to receive and process the
data-packet modulated carrier signal transmitted from a remote bar
code symbol reader to its mated base unit. The radio receiver
circuit of the illustrative embodiment can be realized by
configuring several commercially available IC chips together,
although it is understood that there are certainly other ways in
which to realize the basic functions of this circuit. As shown in
FIG. 16A, receiving antenna 274 is connected to a matching filter
circuit 287 realized using miniature inductive and capacitive
components. The matching filter circuit is tuned to pass a 912 MHz
RF carrier signal transmitted from the data packet transmission
circuit 121 of the bar code symbol reading device. The output of
matching filter circuit 287 is connected to the input of a first IC
chip 288 which converts (i.e., translates) the frequency spectrum
of the received modulated carrier signal down to an intermediate
frequency band, for subsequent signal processing. In the
illustrative embodiment, the first IC chip 288 is realized using
the MAF2001 IC chip from Motorola, Inc., and provides a low noise
amplifier 289, an double balanced mixer 290. A local oscillator 292
is needed to provide a local oscillator signal of about 922.7 MHZ
for use in frequency down-conversion in the double balanced mixer
290. Typically, a matching filter 291 is commonly required between
local oscillator 292 and mixer 290. As shown in FIG. 16A, the
output of the first IC chip is provided to a band-pass filter 293
tuned to about 10.7 MHZ, the intermediate frequency band of each
base unit. The intermediate signal is then provided as input to a
second IC chip 294. In the illustrative embodiment, the second IC
chip 294 is realized using the MC13156 IC chip commercially
available from Motorola, and provides inter alia an amplification
circuit, a quadrature demodulation circuit 295, a binary
thresholding circuit 296, and carrier signal detection circuit 297.
The function of the second IC chip is four-fold. The first function
of the second IC chip is to filter and amplify the intermediate
signal to produce in-phase and quadrature phase signal components
for use in digital data recovery. The second function of the second
IC chip is to recover an analog data signal at the base band
portion of the spectrum, by providing the in-phase and
quadrature-phase signal components to the quadrature demodulation
circuit 295. Suitable quadrature demodulation circuitry for use in
practicing the present invention is disclosed in U.S. Pat. No.
4,979,230 to Marz, which is incorporated herein by reference in its
entirety. As illustrated in FIG. 16A, the third function of the
second IC chip is to convert the analog data signal produced from
quadrature demodulation circuit 295 into a digital data signal
using a binary-level thresholding circuit 296. The fourth function
of the second IC chip is to analyze the incoming signal from the
output of band-pass filter 293 in order to detect the incoming
carrier signal and produce a carrier detect signal A.sub.7 to the
base unit system controller 278. In order to produce a CMOS
compatible signal, the recovered digital data signal produced from
second IC chip 294 is amplified by a current amplification circuit
298 that is operative whenever a carrier signal is detected (i.e.,
A.sub.7=1). As shown in FIG. 16, the output of current
amplification, circuit 298 is a serial data stream that is clocked
into data packet storage buffer 277 under the control of base unit
system controller 278. In general, the data packet storage buffer
277 can be realized using a commercially available Universal
Asynchronous Receiver/Transmitter (UART) device. The primary
function of data packet buffer memory 277 is to buffer bytes of
digital data in the produced digital data stream.
[0201] In the illustrative embodiment, it necessary to provide a
means within the base unit housing, to recharge the batteries
contained within the hand-supportable housing of the portable bar
code symbol reading device. Typically, DC electrical power will be
available from the host computer system 6, to which, the base unit
is operably connected by way of flexible cables 7 and 8. An
electrical arrangement for achieving this function is set forth in
FIG. 16. As shown, power supply circuit 273 aboard the base unit of
the present invention comprises a conventional current chopper
circuit 299, a high-pass electrical filter 300 in parallel
therewith, and a primary inductive coil 301 in parallel with the
high-pass electrical filter. Low voltage DC electrical power
provided from the host computer system by way of power cable 8 is
provided to direct current (DC) chopper circuit 299, which is
realized on PC board 270 using high-speed current switching
circuits. The function of current chopper circuit 299 is to convert
the input DC voltage to the circuit into a high-frequency
triangular-type (time-varying) waveform, consisting of varilous
harmonic signal components. The function of the high-pass
electrical filter is to filter out the lower frequency signal
components and only pass the higher frequency signal components to
the inductive coil 301. As such, the high frequency electrical
currents permitted to flow through inductive coil 301 induce a high
voltage thereacross and produce time-varying magnetic flux (i.e.,
lines of force). In accordance with well known principles of
electrical energy transfer, the produced magnetic flux transfers
electrical power from the base unit to the rechargeable battery
aboard the bar code symbol reading device, whenever the primary and
secondary inductive coils aboard the base unit and the mated device
are electromagnetically coupled by the magnetic flux. In order to
maximize energy transfer between the base unit and its mated device
during battery recharging operations, high permeability materials
and well known principles of magnetic circuit design can be used,
to increase the amount of magnetic flux coupling the primary and
secondary inductive coils of the battery recharging circuit.
[0202] Referring to FIG. 16, the function of each of the data
processing modules of base unit 3 will now be described in
detail.
[0203] Upon reception of an incoming carrier signal and the
recovery of the digital data stream therefrom, base unit system
controller 278 orchestrates the processing of the recovered digital
data stream. As shown in FIG. 16, the operation of data processing
modules 279, 280, 281, 282 and 283 are enabled by the production of
enable signals E.sub.PFC, E.sub.TID, E.sub.DPID, E.sub.DE, and
E.sub.DFC, respectively, from the base unit system controller.
[0204] The primary function of data packet frame check module 279
is to analyze all of the data bytes in the received data packet,
including the Start and End of Packet Fields, and determine whether
a complete frame (i.e., packet) of digital data bytes has been
recovered from the incoming modulated carrier signal. If so, then
data packet frame check module 279 produces activation control
signal A.sub.PFC=1, which is provided to the base unit system
controller, as shown in FIG. 16.
[0205] The primary function of the transmitter number
identification module 280 is to analyze the data bytes in the
Transmitter ID Field of the received data packet and determine the
Transmitter ID Number preassigned to the bar code reading device
that transmitted the data packet received by the base unit. If the
Transmitter ID Number of the received data packet matches the
preassigned Base Unit Identification No. stored in non-volatile
memory (i.e., EPROM) 302 aboard the base unit, then the transmitter
number identification module generates control activation signal
A.sub.TID=1, which is provided to the base unit system
controller.
[0206] The primary function of the packet number identification
module 281 is to analyze the data bytes in the Packet Number Field
of the received data packet and determine the Packet Number of the
data packet received by the base unit. This module then advises the
base unit system controller that, a different packet number was
received, representing a new group (e.g., now seen) by producing an
encoded signal A.sub.DPID during the system control process.
[0207] The primary function of the symbol character data extraction
module 282 is to analyze the data bytes in the Symbol Character
Data Field of the received data packet, determine the code
represented by the symbol character data, and provided this symbol
character data to the data format conversion module 283 under the
control of the base unit system controller during the system
control process.
[0208] The primary function of the data format conversion module
283 is to convert the format of the recovered symbol character
data, into a data format that can be used by the Lost computer
symbol 6 that is to ultimately receive and use the symbol character
data. In the bar code symbol reading system of first illustrative
embodiment, the data format conversion is from ASCII format to
RS232 format, although it is understood that other inversions may
occur in alternative embodiment of the present if invention.
Typically, the data format conversion process is carried out using
a data format conversion table which contains the appropriate data
structure conversions.
[0209] The primary function of the serial data transmission circuit
284 is to accept the format-converted symbol character data from
the data format conversion module 283, and transmit the same :1 as
a serial data stream over data communication cable 7, to the data
input port of the host computer system 6 (e.g., cash register, data
collection device, inventory computer). Preferably, an RS-232 data
communication protocol is used to facilitate the data transfer
process. Thus the construction of serial data transmission circuit
284 is conventional and the details thereof are well within the
knowledge of those with ordinary skill in the art.
[0210] The primary function of acoustical acknowledgement signal
generation circuit 285 is to produce an acoustical acknowledgement
signal SA in response to the successful recovery of symbol
character data from a transmitted data packet. The purpose of the
acoustical acknowledgement signal is to notify the user that the
transmitted data packet has been successfully received by its mated
base unit. In the illustrative embodiment, the intensity of the
acoustical acknowledgement signal is such that the remotely
situated user of the portable bar code symbol reader can easily
hear the acoustical acknowledgement signal in an expected work
environment having an average noise floor of at least about 50
decibels. Preferably, the pitch of the acoustical acknowledgement
signal is within the range of about 1 to about 10 kilohertz, in
order to exploit the sensitivity characteristics of the human
auditory apparatus of the user. In the exemplary embodiment, the
pitch is about 2.5 kilohertz. Under such conditions, the intensity
of such an acoustical acknowledgement signal at its point of
generation will typically need to have an output signal power of
about 70 decibels in order to be heard by the user in a working
environment having an average noise floor of about 50 decibels and
an average noise ceiling of about 100 decibels. Acoustical
acknowledgement signals of such character can be produced from
acoustical acknowledgement signal generation circuit 285, shown in
FIG. 16.
[0211] As shown in FIG. 16B, acoustical acknowledgement signal
generation circuit 285 comprises a number of subcomponents, namely:
a decoder circuit 305; a voltage controlled oscillator (VCO) driver
circuit 306; a VCO circuit 307; an output amplifier circuit 308;
and a piezo-electric type electro-acoustic transducer 303 having an
output signal bandwidth in the audible range. The operation (i.e.,
duration) of the acoustical acknowledgment signal generation
circuit 285 is controlled by base unit system controller 278 using
enable signal E.sub.AA. In the illustrative embodiment, enable
signal E.sub.AA is a digital word encoded to represent one of a
number of possible audible pitches or tones that are to be
generated upon each successful reception of a transmitted data
packet at a mated base station. The function of decoder circuit 305
is to decode the enable signal EAA produced by the base unit system
controller and produce a set of voltage signals {V.sub.1 1, V2, . .
. , Vn} which correspond to a specified pitch sequence to be
produced by eleclro-acoustic transducer 309. The function of VCO
driver circuit 306 is to sequentially drive VCO circuit 307 with
the produced set of voltages {V.sub.1 1, V2, . . . , Vn} so that
VCO circuit produces over a short time period (e.g., 0.5-1.5
seconds), a set of electrical signals having frequencies that
correspond to the specified pitch sequence to be produced from the
electro-acoustic transducer 309. The function of amplifier circuit
308 is to amplify these electrical, signals, whereas the function
of electro-acoustical transducer 309 is to convert the amplified
electrical signal set into the specified pitch sequence for the
user to clearly hear in the expected operating environment. As
shown in FIGS. 1 and 15A, the base housing is preferably provided
with an aperture or sound port 304 so as to permit the energy of
the acoustical signal from transducer 309 to freely emanate to the
ambient environment of the user. In particular application, it may
be desired or necessary to produce acoustical acknowledgement
signal of yet greater intensity levels that those specified above.
In such instances, electro-acoustical transducer 309 may be used to
excite one or more tuned resonant chamber(s) mounted within or
formed as part of the base unit housing.
[0212] Having described the structure and general functional
components of base unit 3, it is appropriate at this juncture to
now describe the overall operation thereof with reference to the
control process shown in FIG. 17.
[0213] As illustrated at Block A in FIG. 17, radio receiving
circuit 275 is the only system component that is normally active at
this stage of the base unit system control process. All other
system components are inactive (i.e., disabled), including base
unit system controller 278; data packet storage buffer 277, data
packet frame check module 279, transmitter number identification
module 280, data packet number Identification module 281, symbol
character data extraction module 282, data format conversion module
283, serial data transmission circuit 284, and acoustical
acknowledgement signal generation circuit 285. With the radio
receiving circuit activated, the base unit is capable of receiving
any modulated carrier signal transmitted from any of the bar code
symbol reading devices within the data transmission range of the
base unit.
[0214] At Block B in FIG. 17, radio receiving circuit 275
deter-mines whether it has received a transmitted carrier signal on
its receiving antenna element 274. If it has, then the radio,
receiving circuit generates a system controller activation signal
A.sub.7, which activates base unit system controller 278 and signal
amplifier 276 shown in FIGS. 16 and 16A, respectively. Then at
Block C, the base unit system controller activates (i.e., enables)
data packet storage buffer 277 and data packet frame check module
279 by producing activation control signals ESB=1 and E.sub.PFC=1,
respectively. At Block D, the base unit system controller
determines whether it has received an acknowledgement (i.e.,
control activation signal A.sub.PFC=1) from the data packet frame
check module, indicating that the received data packet is properly
framed. If the received data packet is not properly framed, then
the base unit returns to Block A in order to redetect an incoming
carrier signal. However, if the received data packet is properly
framed, then at Block E the base unit system controller enables the
transmitter number identification module by generating enable
signal E.sub.TID=1.
[0215] At Block F, the base unit system controller determines
whether it has received an acknowledgment (i.e., control activation
signal A.sub.TID=1) from the transmitter number identification
module that the received data packet contains the correct
transmitter identification number (i.e., the same number assigned
to the base unit and stored in storage unit 276). If the
Transmitter Identification Number contained within the received
data packet does not match the base unit identification number
stored in storage unit 276, then the base unit system controller
returns to Block A whereupon it resumes carrier signal detection.
If, however, the transmitter packet number contained within the
received data packet matches the base unit identification number,
then at Block G the base unit system controller enables the data
packet number identification module 289 by generating enable signal
E.sub.DPID=1.
[0216] At Block H, the base unit system controller determines
whether it has received an acknowledgment (i.e., control activation
signal A.sub.PDID=1) from the data packet identification module
indicating that the received data packet is not a redundant data
packet (i.e., from the same transmitted data packet group). If the
received data packet is a redundant data packet, then the base unit
system controller returns to Block A, whereupon carrier signal
detection; is resumed. If, however, the received data packet is not
redundant, then at Block the base unit system controller enables
the symbol character data extraction module by generating enable
signal E.sub.DE=1. In response to the generation of this enable
signal, the symbol data extraction module reads at Block J the
symbol character data contained in the received data packet, checks
the data for statistical reliability, and the writes the extracted
symbol character data bytes into a storage buffer (not explicitly
shown).
[0217] As indicated at Block K in FIG. 17, the base unit system
controller then enables the data format conversion module by
generating enable signal E.sub.DFC=1. In response to this enable
signal, the data format conversion module converts the data format
of the recovered symbol character data and then buffers the
format-converted symbol character data bytes in a data buffer (not
explicitly shown). At Block L the base unit system controller
enables the serial data transmission circuit 284 by generating
enable signal E.sub.DT=1. In response to this enable signal, the
serial data transmission circuit transmits the format-converted
symbol character data bytes over communication cable 7 using serial
data transmission techniques well known in the art, as discussed
above. When the serial data transmission process is successfully
completed, the base unit system controller enables at Block M the
acoustical acknowledgement signal generation circuit 285 by
producing enable signal E.sub.AA=1. In response to the production
of this enable signal, acoustical acknowledgment signal generation
circuit 285 generates a high intensity acoustical signal having
characteristics of the type described above, thereby informing the
user that a transmitted data packet has been received and that the
symbol character data packaged therein has been successfully
recovered and transmitted to the host computer system. Thereafter,
the base unit system controller returns to the Block A, as
shown.
[0218] It is appropriate at this juncture to illustrate the
automatic hands-on and hands-free modes of operation of the system
while utilized in different mounting installations.
[0219] A point-of-sale station is shown in FIGS. 18A and 18B, as
comprising an electronic cash register 6 operably connected to the
automatic bar code reading system of the first illustrative
embodiment by way of flexible communication cable 7. Low voltage DC
power is provided to base unit 3 by way of flexible power supply
cable 8. In this particular mounting installation, base unit 3 is
supported on a horizontal countertop surface. If necessary or
desired in such mounting installations, the base plate of base unit
3 may be weighted by affixing one or more dense mass elements to
the upper surface of the base plate.
[0220] With automatic bar code reading device 2 supported within
scanner support stand portion of the base unit, the system is
automatically induced into its automatic long-range hands-free mode
of operation. The positioning of both object detection and scan
fields in this mounting installation allows bar code symbols on
objects to be easily read. In order to induce the system into its
short-range hands-on mode of operation, the user simply encircles
the handle portion of the hand-supportable device with his or her
fingers, and then lifts the device out of the scanner support
stand. Upon lifting the device out of its stand, the range
selection circuit 115 (e.g., including a Halt-effectmagnetic flux
sensor (mounted in the handle of the housing) detects the absence
of magnetic flux produced from a permanent magnet mounted in the
support stand, and automatically generates the short-range control
activation signal (i.e., R.sub.1=0). The details of this range
mode-selection mechanism can be found in copending application Ser.
No. 07/761,123, now U.S. Pat. No. 5,340,971 supra.
[0221] With the automatic bar code reading device held in the
user's hand, and a bar coded object 435 in the other hand, the
object is moved into the short-range portion of the object
detection field as shown in FIG. 18B, where the object is
automatically detected, and bar code symbol 436 automatically
scanned while the visible laser beam is repeatedly scanned within
the scanning volume. After the bar code symbol has beer
successfully read (i.e., detected and decoded) and a transmitted
data packet containing symbol character data has been received and
processed at base unit 3 in a manner described hereinabove, a
highly audible acoustical acknowledgement signal Sack of a
predetermined pitch is produced from the base unit. Thereafter, the
bar code reading device is placed back within the scanner support
stand, where it is once again induced into its long-range
hands-free mode of operation.
[0222] Having described the preferred embodiments of the present
invention, several modifications come to mind.
[0223] In the system control process of the illustrative
embodiment, shown in FIG. 8, the polygon 36 is actively driven to
its desired angular velocity only when the system is in its bar
code symbol detection and read modes. In the illustrative
embodiment, the moment of inertia of the polygon 36 is ultra-low so
that it can instantly attain its desired angular velocity (from
rest) in a very short time from when an object is detected within
the 3-D scanning volume.
[0224] In an alternative embodiment of the present invention, the
control system of the laser scanner hereof can be modified so that
the scanning polygon 36 is actively driven to idle at angular
velocity W.sub.OD when the system is in its object detection mode,
and actively driven to its desired angular velocity W.sub.BCD
(i.e., where W.sub.BCD W.sub.OD) when the system is in the bar code
detection mode. Using this control process, the scanning polygon is
permitted to quickly attain its desired operating velocity
W.sub.BCD when an object is detected in the scanning volume, for
subsequent scan data collection operations. This control technique
offers the advantage of using a polygon of a high moment of
inertia, with the option of periodically imparting torque to the
polygon motor shaft during the object detection state to maintain
the idling velocity W.sub.ODS in an electrically conservative
manner. The motor control circuit hereof can be readily modified to
realize such a pulsed-torque functionality in the system of the
present invention.
[0225] In an alternative embodiment, where power consumption is not
of critical concern, the scanning polygon can be continuously
driven to the desired operating velocity at each state of system
operation.
[0226] The automatic bar code reading system of the present
invention is capable of performing a wide variety of complex
decision-making operations in real-time, endowing the system with a
level of intelligence hitherto unattained in the bar code symbol
reading art. Within the spirit of the present invention, additional
decision-making operations may be provided to further enhance the
capabilities of the system.
[0227] While the various embodiments of the projection laser
scanner hereof have been described in connection with linear (1-D)
code symbol scanning applications, it should be clear, however,
that the projection laser scanner of the present invention is
suitable for scanning 2-D code symbols as well as alphanumeric
characters (e.g. textual information) in optical character
recognition (OCR) applications.
[0228] While the particular illustrative embodiments shown and
described above will be useful in many applications in code symbol
reading, further modifications to the present invention herein
disclosed will occur to persons with ordinary skill in the art. All
such modifications are deemed to be within the scope and spirit of
the present invention defined by the appended claims to
Invention.
* * * * *