Note: Descriptions are shown in the official language in which they were submitted.
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10 OPTICALLY-GUIDED INDICIA READER SYSTEM
Technical Field
The present invention relates to image processing and more particularly
relates to over-
the-belt optical character recognition (OCR) systems. Specifically, the
invention relates to an
indicia reader system that includes a projected optical guide to assist the
positioning of parcels on
a conveyor.
Background of the Invention
For years, machines have been used to scan parcels as they travel along a
conveyor.
Over-the-belt optical character recognition (OCR) systems have been recently
developed that can
read indicia, such as a typed or hand-written destination address on parcels
to be shipped.
Parcel delivery companies, such as United Parcel Service, ship millions of
parcels every day.
These parcel delivery companies make extensive use of OCR systems to read the
destination
address labels on parcels to facilitate sorting and routing the parcels to
their proper destinations.
The fundamental physical components of an OCR system are a scanner and a
character
recognition system including a central processing unit (CPU), a computer
memory, and a
sophisticated character recognition program module. The scanner is typically
an optical camera,
such as a charge-coupled device (CCD) array, that captures an image of the
destination address
on the parcels as they travel past the scanner on the conveyor. Generally, a
continuous video
image of the conveyor carrying the parcels is captured by the scanner, which
video image is
converted into digital format and transmitted to the character recognition
system. But only a
small part of the video image, such as the portions including the destination
addresses of the
parcels, needs to be processed by the character recognition system. The OCR
system, therefore,
must have some way to identify the portions of the video image that need to be
processed by the
' 35 character recognition system.
One approach is to store the entire video image created by the scanner, and
later parse out
' the portions of the video image that need to be processed by the character
recognition system.
But a continuously running scanner generates an enormous amount of video data.
This data i.c
formatted as a continuous bit map of the conveyor as the conveyor carries
parcels past the
scanner. This bit map inherently conveys information about the spatial
relationship of the pixels
of the image. Storing this continuous bit map requires an enormous amount of
computer
1 IM
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memory. It is therefore advantageous to reduce the memory storage requirement.
Data compression is one technique for reducing the memory storage requirement.
The
video data may be compressed for storage using any of a variety of well known
data
compression methods, such as run length encoding. These data compression
techniques,
however, alter the bit-map format of the data. This is undesirable because it
is advantageous for
the character recognition program module to operate on bit maps that allow
easy access to
information regarding neighborhoods around individual pixels. The compressed
data must
therefore be uncompressed, typically into a frame buffer, for processing by
the character
recognition program module. Compressing the video data for storage, and then
uncompressing
the video data for processing, burdens the CPU and slows the character
recognition process.
Real-time extraction of the desired portions of the video data is another
technique for
reducing the memory storage requirement. Indeed, real-time data extraction is
a very effective
technique because most of the video data created by the continuously running
scanner is a
useless image of the conveyor and the non-indicia bearing areas of the parcels
moving along the
conveyor; only a small percentage of the data includes the destination
addresses of the parcels to
be shipped. Therefore, extracting only small portions of the video data, such
as relatively small
areas covering the destination addresses, greatly reduces the memory storage
requirement and
speeds up the character recognition process.
Systems have been developed for triggering a video camera system so as to
store only
desired video images. For example, Tonkin, U.S. Patent No. 4,742,555,
describes a
mechanical Iimit switch, optical sensor, or magnetic sensor that triggers a
video system to
capture and store an image of a parcel as the parcel reaches a predetermined
location along a
conveyor. But the system described by Tonkin would have a significant drawback
if applied to
a parcel shipping system. This is because the system described by Tonkin
captures an image of
the entire parcel; is not operative for capturing only a specific portion of
the image, such as the
destination address. In a parcel shipping system, the destination address must
be captured for
sorting and routing purposes, but other indicia on the parcel, such as the
return address, is not
needed to route the parcel to its proper destination. It is therefore
advantageous to identify the
destination address prior to storing the image of the parcel, so that only the
portion of the image
containing the destination address may be stored in the computer memory.
Several difficulties are encountered, however, in attempting to identify the
destination
addresses on various parcels traveling on a conveyor. First, the destination
addresses may vary
in size, and may be in different locations on different parcels. Second, the
parcels themselves
may vary in size, shape, and position on the conveyor. Thus, the exact
position of a destination
address on a parcel cannot be determined by simply detecting the edge of the
parcel using a limit
switch or sensor, as described by Tonkin.
Systems have been developed for storing video images of selected portions of
parcels
traveling of a conveyor. For example, Kizu et al., U.S. Patent No. 4,516,265,
describes a two-
camera system that reads the postal (zip) codes on envelopes traveling on an
envelope transport
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3
system. The system includes a low resolution prescanner that coarsely scans
the surface of the
envelope. The position of the destination address block is determined from the
coarse scan, and
the coordinates of the destination address block with respect to the leading
edge of the envelope
are then passed to a second, high-resolution camera system. The second camera
system stores
an image of the destination address block by first detecting the leading edge
of the envelope.
The second camera system begins storing an image of the destination address
black when the
block reaches the second camera, and stops storing the image when the black
moves past the
second camera. A postal code reader subsequently processes the high-resolution
scan to read the
postal code.
Another example is disclosed in Morton et al., U.S. Patent No. 5,642,442. This
patent
describes a two-camera system that reads the destination addresses on parcels
traveling on a
conveyor. A fluorescent ink fiduciary mark is superimposed relative to the
destination address
on a parcel. A first camera captures an image of the fiduciary mark, the
position and orientation
of which is ascertained. The position and orientation of the fiduciary mark is
then used to extract
an image of the destination address from a video data signal created by a
second camera, which
is positioned downstream from the first camera. The image of the destination
address is stored
in a computer memory for subsequent processing by a character recognition
system.
The two-camera systems described above are very effective at minilriizing the
amount of
video data that must be stored in an OCR system. They are, however, rather
expensive systems
that are best suited for very high-speed parcel handling systems. The cost
associated with these
systems may not be justified for many lower-speed parcel handling systems. The
LBM
Technical Disclosure Bulletin, Vol. 15 Nr. 4, Pg. 1170-1171 describes a moving-
light parcel
positioning scanning and sorting system that captures images of addresses on
parcels. But this
system does not describe further techniques for obtaining sharp image of the
addresses, nor does
it describe a non-moving-light parcel positioning system. In addition, the IBM
disclosure
document does not describe a mufti-conveyor parcel positioning system.
There is, therefore, a need for a less expensive and more effective system for
minimizing
the amount of video data that must be stored in an OCR system. In particular,
there is a need for
an inexpensive yet effective indicia reader system that is suited to low- to
medium-speed parcel
handling systems.
(the remainder of the page intentionally left blank)
p,MENDSD St~+E~S
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3A
Summary of the Invention
The invention seeks to provide a low-cost system for minimizing the amount of
video
data that must be stored in an OCR system. In particular, the invention seeks
to provide an
inexpensive indicia reader system suited to low- to medium-speed parcel
handling systems.
In accordance with the invention, these objects are accomplished in an indicia
reader
system that includes an optical guide to assist the positioning of parcels on
a conveyor. For
example, the optical guide may include a static elongated strip of light
projected toward the
conveyor from an illumination source positioned above the conveyor. An
operator positions a
parcel on the conveyor so that indicia to be imaged, such as the destination
address on the parcel,
is within static elongated strip of light. The parcel may also be positioned
on the conveyor so
that other indicia that is not to be imaged, such as the return address on the
parcel, is not within
the static elongated strip of light. Projecting the optical guide onto the
parcel avoids parallax-
related alignment errors that could otherwise occur with tall parcels in
systems using other types
of optical guides, such as reference marks placed on the conveyor itself.
(the remainder of the page intentionally left blank)
AMENDED S'r~EET
i
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The optically-guided indicia reader system may also include a proximity
sensor, such as
a photo detector, for detecting the arnval of the parcel at the scanner. In
response to a signal
from the proximity sensor, the computer memory and the scanner may be operated
so as to store
an image of a region having a width approximately equal to the width of the
area defined by the
illumination source, and a length approximately equal to the length of the
parcel in the direction
of conveyor travel.
The optically-guided indicia reader system may also include a reflectivity
sensor located
upstream of the scanner and positioned to determine reflectivity data
associated with the parcel.
A communication link transmits the reflectivity data from the reflectivity
sensor to the scanner,
and the gain of the scanner is adjusted in response to the reflectivity data.
In addition, an
optically-guided indicia reader system may include a height sensor located
above the conveyor
and upstream of the scanner and positioned to determine height data associated
with the parcel at
the location of the destination address. A communication link transmits the
height data from the
height sensor to the scanner, and the scanner is focused in response to the
height data.
According to another aspect of the invention, an operator positions a parcel
on the
conveyor so that indicia to be imaged, such as the destination address on the
parcel, coincides
with a moving spot light defined by an illumination source. A scanner located
downstream of
the illumination source captures an image of a region that is defined with
respect to the spot
defined by the illumination source. For example, the optical guide may include
a moving light,
such as a narrow-beam spot light, that is projected onto the conveyor, and
that travels at the
same speed as the conveyor. Positioning a parcel on the conveyor so that the
spot light is
located in the center of the city and state address lines of the destination
address allows a scanner
to efficiently capture an image of the destination address for processing by a
character
recognition reader.
The moving-light indicia reader system includes a conveyor for transporting a
parcel
from an upstream location of the conveyor to a downstream location of the
conveyor. A
moving-light system, which is preferably positioned above the conveyor,
includes an
illumination source for defining a spot that moves at the same speed as the
conveyor to assist in
positioning the parcel on the conveyor. A scanner, which is located downstream
from the
moving-light illumination source, and a processing module are operated so as
to store an image
of a region of the parcel defined with respect to the spot defined by the
moving-light illumination
source. For example, the illumination source may define a spot that is
substantially smaller than
the region to be imaged by the scanner of the indicia reader system. An
operator may then
position a parcel so that the spot defined by the moving-light illumination
source is located
approximately in the center of the city and state lines of the destination
address on the parcel.
A moving-light indicia reader system may also include a reflectivity sensor
located
upstream of the scanner and positioned to determine reflectivity data
associated with the parcel.
Reflectivity data from the reflectivity sensor is obtained for the spot
defined by the moving-light
illumination source so that reflectivity data is collected regarding the
parcel at the region to be
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captured and stored for subsequent processing by a character recognition
system. A
communication link transmits this reflectivity data from the reflectivity
sensor to the scanner, and
the gain of the scanner is adjusted in response to the reflectivity data. In
addition, a moving-light
indicia reader system may include a height sensor located above and upstream
of the scanner and
5 positioned to determine height data associated with the parcel at the
location of the destination
address. Height data from the height sensor is obtained for the spot defined
by the moving-light
illumination source so that height data is collected regarding the parcel at
the region to be
captured and stored for subsequent processing by the character recognition
system. A
communication link transmits this height data from the height sensor to the
scanner, and the
scanner is focused in response to the height data.
According to yet another aspect of the invention, a mufti-conveyor indicia
reader system
includes a plurality of moving-light indicia reader systems, wherein each
moving-light indicia
reader system includes an illumination source for defining a spot that moves
at the same speed as
its respective conveyor to assist in positioning parcels on the conveyor. The
processing module
and the scanner of each moving-light indicia reader system are operated so as
to store an image
of a region of the parcel defined with respect to the spot defined by the
illumination source. In
addition, the illumination sources are operated so as to time-division
multiplex the storage of the
images generated by the several moving-light indicia reader systems.
That the present invention improves over the drawbacks of the prior art and
accomplishes
the objects of the invention will become apparent from the following detailed
description of the
preferred embodiment and the appended drawings and claims.
Brief Description of the Drawings
FIG. 1 is a diagram of an optically-guided indicia reader system.
FIG. 2, including FIGS. 2A-2E, illustrates a moving-light indicia reader
system.
FIG. 3 illustrates a parcel with the spot defined by the moving-light system
located
approximately in the center of the city and state address lines of the
destination address.
FIG. 4 illustrates a mufti-conveyor indicia reader system.
Detailed Description
FIG. 1 is a diagram of an optically-guided indicia reader system 10 that
includes a
conveyer 12 carrying a parcel 14 from an upstream location I6 to a downstream
location 18 of
the conveyor 12. The parcel 14 includes indicia to be read by the optically-
guided indicia reader
system 10, such as a destination address 20. The parcel 14 may include other
indicia, such as
the return address, that the indicia reader system 10 preferably avoids
reading.
An illumination source 24 is positioned to define a static area 26 to assist
in positioning
the parcel 14 on the conveyor 12. The area 26 is static in that it does not
travel along with the
conveyor 12, but remains stationary with respect to an operator station that
is located along side
the conveyor 12. Thus, the conveyor 12 travels through the area 26, which is
defined by light
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projected by the illumination source 24.
The illumination source 24 may define the area 26 many different ways. For
example,
illumination source 24 may illuminate the interior of area 26, or the border
of the area 26, or
two spaced-apart parallel lines in the direction of conveyor travel, etc. The
illumination source
24 is positioned a sufficient distance above the conveyor 12 so that the
parcel 14 may be
positioned on the conveyor 12 to pass beneath the illumination source 24. An
operator may
therefore view the area 26, which is defined by light projected by the
illumination source 24,
directly on the parcel 14 as the operator positions the parcel 14 on the
conveyor 12. The area
26 thus provides an optical guide to assist the operator in positioning the
parcel 14 on the
conveyor 12.
A sensor assembly 28, including a height sensor and reflectivity sensor, my be
located
toward the downstream end of the illumination source 24. A communication link
30
functionally connects the sensor assembly 28 to a scanner 32 that is located
downstream from
the sensor assembly 2$. The scanner 32 is focused in response to height data
from the height
sensor, and the gain of the scanner 32 is adjusted in response to reflectivity
data from the
reflectivity sensor, so that the scanner 32 generates a clear image of the top
of the parcel 14 as
the parcel passes beneath the scanner 32. The scanner 32 is preferably
positioned so that the
scan line 34 is oriented across a portion of the conveyor 12 that is aligned
with the area 26 in
the cross-machine direction.
A belt encoder 36 measures the displacement of the conveyor 12. A
communication link
38 functionally connects the belt encoder 36 to the scanner 32 and to a
character recognition
system 40 that includes a processing unit 41 and a computer memory 42. Another
communication Iink 44 functionally connects the character recognition system
40 to the scanner
32. The height data from the sensor assembly 28 indicates the presence of a
parcel 14 on a
particular location of the conveyor 12. Thus, the height data and the signal
from the belt
encoder 36 may be used to determine when a parcel 14 is present at the scanner
32.
Alternatively, a proximity sensor, such as a photo sensor 45, may be
positioned
upstream from the scanner 32. A communication link 48 functionally connects
the scanner 32
to the photo sensor 45. The photo sensor includes a light source 46a that
projects a columnar
beam of light 50 toward a photo detector 46b. The photo sensor 45 detects the
presence of the
parcel 14 as it passes by the photo sensor 45 because the parcel breaks the
beam of light 50.
Many other types of proximity sensors, such as a mechanical or a magnetic
sensor, may
equivalently be used to detect the location of the parcel 14 on the conveyor
12.
The belt encoder 36 is a standard belt-driven, opto-mechanical encoder that
provides a
signal indicating the linear displacement of the conveyor 12. The CCD array of
the scanner 32
is cycled in response to the signal from the belt encoder 26 to generate a
series of analog images
of the scan line 34 that are transmitted to an analog-to-digital converter
within the scanner 32.
The analog-to-digital converter of the scanner 32 uses a standard thresholding
or similar process
to convert the analog signal produced by the CCD array of the scanner 32 into
an eight-bit digital
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video signal that is transmitted via the communication link 44 to the
character recognition system
40, which stores the video data in the computer memory 42 for subsequent
processing.
The region to be stored in the computer memory 42 may include all or part of
the scan
line 34. This may be accomplished by only storing the output of all or only a
portion of the cells
of the scanner 32. The region to be stored in the computer memory 42 is
preferably aligned
with and has a length that is approximately equal to the width of the area 26
so that the region
stored in the computer memory 42 corresponds to, but is downstream from, the
area 26 defined
by the illumination source 24. This assists an operator in orienting a parcel
14 so that the
destination address 20 can be effectively scanned by the indicia reader system
10 as configured.
Alternatively, the operator may determine that the parcel 14 cannot be
oriented so that the
destination address 20 can be effectively scanned by the indicia reader system
10 as configured.
This may happen if the destination address 20 is larger than the region to be
stored in the
computer memory 42. In this case, the operator can divert the parcel 14 for
hand sorting or
imaging using a differently configured indicia reader system.
The scanner 32 may run continuously, so that region generated by the scanner
32 and
stored in the computer memory 42 of the character recognition system 40 is a
continuous strip
having a width approximately equal to the width of the area 26 defined by the
illumination
source 24. The size of the region may be further reduced by using the height
data from the
sensor assembly 28 or the signal from the photo sensor 45 to trigger the
storage of video data
generated by the scanner 32. For example, the video data generated by the
scanner 32 may be
stored in the computer memory 42 only when the beam 50 of the photo sensor 45
is broken. A
time delay may be imposed to account for the distance between the beam 50 or
the sensor
assembly 28 and the scan line 34. In this manner, an image of a strip of the
top of the parcel 14
including the destination address 20 may be stored in the computer memory 42.
That is, an
image of a region of the parcel 14 having a width approximately equal to the
width of the area
26 defined by the illumination source 24, and a length approximately equal to
the length of the
parcel 14 in the direction of conveyor travel, may be stored in the computer
memory 42 of the
character recognition system 40.
Triggering the storage of the image of the region in the computer memory 42
may be
accomplished in several different ways. For example, the scanner 32 may be
toggled on and off
by the signal from the photo sensor 45 or the sensor assembly 28 (with an
appropriate time
delay). Or the scanner 32 may run continuously, and the signal from the photo
sensor 45 or the
sensor assembly 28 may be used to latch a control line to an input buffer of
the character
recognition system 40. Alternatively, the signal from the photo sensor 25 or
the sensor
assembly 28 may be used as an input to a software-based algorithm running on
the processing
unit 41, which triggers the storage of video data from the scanner 32 in the
computer memory
42. Many other means known to those skilled in the art may equivalently be
employed to
operate the computer memory 42 and the scanner 32 so as to store an image of a
region in the
computer memory 42.
~ I
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To use the static-light indicia reader system 10, an operator positions the
parcel 14 on
the conveyor 12 so that the destination address 20 is within the area 26
defined by the
illumination source 24. The operator may also position the parcel 14 on the
conveyor 12 so
that other indicia on the parcel 14, such as the return address 22, is not
within the area 26
defined by the illumination source 24. It will be appreciated that many other
types of indicia
may be placed within, or excluded from, the area 26, such a barcode, a two-
dimensional code, a
hologram, etc.
Acceptable performance is experienced when optically-light indicia reader
system 10 is
configured as follows. The area 26 is typically a rectangular strip that is
significantly narrower
than the conveyor 12, sufficiently long to allow an operator to easily
position a parcel on the
conveyor 12 using the optical guide, and approximately in the center of the
conveyor I2. For
example, the area 26 may be approximately 4 inches (10 cm) in the cross-
machine direction and
approximately 12 (30 cm) to 36 inches (91 cm) in the direction of conveyor
travel. The use of
projected illumination, rather than an area painted on the conveyor 12, allows
the operator to
view the area 26 defined by the illumination source 24 directly on the top of
the parcel 14.
Thus, there is no displacement between the area 26 and the top of the parcel
14 that could cause
parallax-related alignment errors with tall parcels. The use of a relatively
narrow area 26 allows
the angle of the field of view of the scanner 32 to be relatively narrow so
that the scanner 32
generates a sharp image of the top of the parcel 14.
The belt encoder 36 is a standard belt-driven, opto-mechanical encoder that
provides a
signal indicating the linear displacement of the conveyor 12. The CCD array of
the scanner 32
is cycled in response to the signal from the belt encoder 36 to generate a
series of analog images
' of the scan line 34 that are transmitted to an analog-to-digital converter
within the scanner 32.
The analog-to-digital converter of the scanner 32 uses a standard thresholding
or similar process
to convert the analog signal produced by the CCD array of the scanner 32 into
an eight-bit digital
video signal that is transmitted via the communication link 44 to the
character recognition system
40, which is operable for storing the video data in the computer memory 42 for
subsequent
processing.
The scanner 32 is preferably a monochrome, 4,096 pixel line-scan type CCD
array such
as one using a Thompson TH7833A CCD chip. As the field of view of the scanner
32 is
approximately 16 inches (41 cm) at the conveyor 12, the resolution of the
image created by the
scanner 32 is approximately 256 pixels or "dots" per inch (DPI) (101 dots per
cm) across the
field of view of the scanner 32. The belt encoder 36 preferably triggers the
CCD array of the
scanner 32 at a rate of approximately 256 cycles ger inch (101 cycles per cm)
so that the
resolution of the image created by the scanner 32 is approximately 256 pixels
or "dots" per inch
(DPI) (101 dots per cm) in the direction of conveyor travel. It will therefore
be appreciated that a
digital image with a correct aspect ratio (i.e., the ratio of the length of
the image to the width)
may be generated by the scanner 32 and stored in the computer memory 42 of the
character
recognition system 40 by synchronizing the cycling rate of the scanner 32 with
the linear speed
CA 02271063 2002-08-19
9
of the conveyor 12. See, for example, Shah et al, C7.S, Patent No. 5,291,564.
The conveyor 12 may be approximately 24 inches (61 cm) wide and travel at
linear speeds up to 20 inches per second or 100 feet per minute (51 cm per
second or 30
meters per minute) or more. 'fhe illumination source 'Z4, which may be any of
a variety of
commercially-available narrow-beam light sources, is preferably positioned
approximately 18
inches (46 em) above conveyor 12 and defines an area ~'6 that is approximately
4 inches (10
crn) in the cross-machine direction and approximately 12 (30 cm) to 36 inches
(91 cm) in the
direction of conveyor travel.
The scanner 32 is preferably mounted to have a~n optical path of approximately
120 inches (304 cm) to the conveyor 12 with a Ifi inch (41 ern) field of view
at the conveyor
12. To save space, the scanner 32 is positioned approximately 30 inches (76
cm) above the
center of conveyer 12 and is pointed towards a complex of mirrors (not shown)
that increases
the optical path from the scanner 32 to the conveyor l:? to approximately 120
inches (305
em). These parameters may be varied somewhat without unduly .affecting the
performance
of the disclosed embodiment of the present invention. See also, Srnith et al,
LJ.S. Patent No.
5,308,960 and Bjorner, et al, U.S. Patent No. 5,485,26 >.
It should also be understood that the scan line 34 may be longer than the
width
of the region stored in the computer memory 42. For example, the scanner 32
may be
positioned to have a field of view (i.e. the Scan line 34) equal to
approximately 16 inches (41
cm) at the conveyor 12. The region stored in the computer memory 42, however,
may only
be approximately 4 inches ( 10 cm), which preferably corresponds to the width
of the area 26
defined by the illumination source 24. 'This may be accomplished by only
storing the output
of a portion of the cells of the scanner i2 (e.g. the center 1,024 pixels of a
4,096 pixel
scanner) in the computer memory 42.
In view of the forgoing, it will be appreciated that th.e optically-guided
indicia
reader system 10 reduces the amount of video data that must be stored in the
computer
memory 42 of the character recognition system 40. 'fhe. use of projected
illumination allows
the operator to view the area 30 defined by the illumination source 24
directly on the top of
the parcel 14. Thus, there is no displacement between the area 26 and the top
of the parcel
14 that could cause parallax-related alignment ~;rror5 with tat'. parcels. In
addition, the
optically-guided indicia reader system 10 allows the angle of the field of
view of the scanner
32 to be relatively narrow so that the scanner 32 generates a sharp image of
the top of the
CA 02271063 2002-08-19
1 ()
parcel 14.
FIGS. 2A - 2I~ illustrate another embodiment of the invention, a single-
conveyor
moving-light indicia reader system in which a moving-light illumination source
defines a spot
that moves at the same speed as a conveyor to assist the positioning of a
parcel on the
conveyor. FIG. 3 illustrates a parcel in this moving-light indicia reader
system with the spot
defined by the moving-light illumination source located approximately in the
center of the
region to be captured. More specifically, the parcel is preferably positioned
on the conveyor
so that the center of the spot defined by the moving-light illumination source
is approximately
in the center of the city and state lines of the destination address. FIG. 4
illustrates a
mufti-conveyor indicia reader system, in which the illumination sources of a
plurality of
moving-light indicia reader systems are operated so as to time-division
multiplex the storage
of the images generated by the several moving-light indicia reader systems.
These
embodiments of the invention are described below.
FIGS. 2A - IJ illustrate a moving-tight indicia reader system 200 including a
conveyer 212 carrying a parcel 214 from an upstream location 216 to a
downstream location
218 of the conveyor 212. T he parcel 214 includes indicia to be read by the
moving-light
indicia reader system 200, such as a destination address 221y. The parcel 214
may include
other indicia, such as the return address, that the moving-Light indicia
reader system 200
preferably avoids reading.
The moving-light indicia reader system 200 includes a moving-light
illumination
source 224 that includes a plurality of discrete illumination sources 226a
through 226n, such
as light-emitting diodes (L,EDs), that project columnar beams of light
represented by the beam
228. The illumination source 224 is positioned a sufficient distance above the
conveyor 212
so that the parcel 214 may be positioned on the conveyor 212 to 'pass beneath
the moving-
light illumination source 224. An operator may therefore view the spot 230,
which is defined
by light projected by the moving-light illumination source 2?4, directly on
the parcel 214 as
the operator positions the parcel 214 on the conveyor 212. The spot 230 thus
provides an
optical guide to assist the operator in positioning the parcel 214 on the
conveyor 212.
A sensor assembly 232, including a height sensor and reflectivity sensor, is
located toward the downstream end of ihc illumination source; 224. A
communication link-
234 functionally connects the sensor assembly 232 to a scanner 236 that is
located
downstream from the sensor assembly 232. The scanner 236 includes internal
components
CA 02271063 2002-08-19
l0A
2 33 well known to those skilled in the art to automatically focus th a
scanner 236 in response
to height data from the height sensor and to automatically adjust the gain of
the scanner 236
in response to reflectivity data from the reflectivity sensor, so that the
scanner 236 generates
a clear image of the top of the parcel =' I4 at the region to be captured and
stored for
S subsequent processing by a character recognition system :Z40 as the parcel
214 passes beneath
the scanner 236. The scamler 236 is aligned with the spot 230 so that the
scanner may be
operated to capture an image of the destination address 220 on they parcel
214.
A belt encoder 23$ measurca the displacement of tire conveyor 212. A
communication link 239 functionally connects the belt encoder 238 to the
scanner 236 and
to a character recognition system 240 that includes a processing module 241
and a computer
memory 242. A second communication link 244 t'unctionally connects the
character
recognition system 240 to the scanner '?36 and a third communication link 246
functionally
connects the character recognition system 240 to the mowing-light illumination
source 224.
The signal from the belt encoder 238 is used to determine the speed of the
conveyor 212,
1 S which is used to synchroni-re the operation of the moving-light
illumination source
224, the scanner 236 and the character ~ recognition system 240 so that an
image of a region 2S0 defined with respect to the spot 230 is
CA 02271063 2002-08-19
WD 98/32545 PCT/US98/01366
stored in the computer memory 242, The height data from the sensor assembly
232 indicates
the presence of a parcel 214 in association with a spot 230 so that an image
of a region 250 is
only stored in the computer memory 242 when a parcel 214 is present in
association with a
spot 230 defined by the moving-Light illununation source 224.
To use the moving-light indicia reader system 2011, an operator positions the
parcel 214
on the conveyor 212 so that the spot 230 defined by the moving-light
illumination source 224
is centered with respect to the destination address 220 on the parcel 214. For
example, FIG.
2A illustrates the parcel 214 positioned so that the spot 230 defined by the
first discrete
illumination source 226a is centered with respect to the destination address
220. From this
1G position, the parcel 214 travels on the conveyor 212, and the spot 230
travels at the same
speed as the parcel 214, so that the spot 230 remains stationary relative to
the parcel 214.
Thus, as illustrated in FIG. 2B, the parcel 214 is later positioned so that
the spot 230' defined
by the third discrete illumination source 226c is centered with respect to the
destination address
220. Later still, as illustrated in FIG. 2C, the parcel 214 is positioned so
that the spot 230"
defined by the last discrete illumination source 226n is centered with respect
to the destination
address 220.
FIGS. 2D and 2E illustrate the scanning of the parcel 2l4 by the scanner 236,
which
includes a CCD array that repeatedly generates an image of a scan line 252 to
generate a video
signal. The operation of the scanner 236 and the processing, module 241 of the
character
recognition system 240 are synchronized with the movement of the spot 230 so
as to store in
the computer memory 242 an image of the region 250, which is defined with
respect to the spot
230. When the region 250 reaches the scan line 252, which happens shortly
after the parcel
214 is in the position shown in FIG. 2D, the processing module 241 causes the
computer
memory 242 of the character recognition system 240 to begin storing the video
data generated
by the scanner 236. The video data generated by the scanner 236 continues to
be stored until
the region 250 passes the scan line 252, which happens shortly before the
parcel 214 is in the
position shown in FIG. 2E.
It will be understood that, when the parcel 214 is positioned as shown in
FIGS. 2D-E,
the spot 230 is not visible to an operator because the parcel 214 is not under
the moving-light
illumination source 224. Nevertheless, the character recognition system 240
uses the signal
from the belt encoder 238 to keep track of the spot 230 after the parcel 214
travels past the
moving-light illumination source 224. Thus, an image of the region 250, which
is defined with
respect to the spot 230, is stored in the computer memory 242 of the character
recognition
system 240.
FIG. 3 illustrates a parcel 214 with the spot 230 defined by the moving-light
illumination source 224. The spot 230 is typically a round or oval area that
is somewhat
smaller that than the region 250 to t>e imaged by the scanner 236. For
example, the area
associated with the spot 230 may be approximately one 1 inch (2.5 cm) across,
whereas the
region 250 may be approximately 4 inches (10 cm) by 4 inches (10 cm). The
parcel 214 is
CA 02271063 2002-08-19
12
preferably positioned so that the center of the spot 230 is approxirnately in
the center of the
city and state address lines of the destination address 220. This allows the
scanner 236 to
capture an image of the destination address 2'?0 by imaging the region 250.
It will be appreciated, however, that the spot 23() may have virtually any
size or
configuration and that multiple spots may be used to identii~y indicia on the
parcel, such as
four spots defining the comers of a rectangular region to be imaged. For
example, the spot
230 may be defined by an illuminated area or by an illuminated border, or by
two illuminated
spaced-apart parallel lines, etc. In addition, the spot 230 could be
configured to correspond
to the width of the region 250 to be stored in the computer memory 224. This
would assist
an operator in orienting a parcel 214 so that the destination address 220 can
be effectively
scanned by the indicia reader system 20(? as configured. Alternatively, the
operator may
determine that the parcel 214 cannot be oriented so tluat the destination
address 220 can be
effectively scanned by the indicia reader system 200 as configured. 'this may
happen if the
destination address 220 is larger than the region 250 to be stored in the.
computer memory
242. In this case, the operator can di~~ert the parcel 214 for hand sorting or
imaging using
a differently configured indicia reader system.
To capture the image of the region 250, the character recognition system 240
is
operative to selectively trigger the storage of an image in the computer
memory 242.
Triggering the storage of the image of the region 250 in the computer memory
242 may be
accomplished in several different ways. Fc.~r example, the scanner 2.36 may be
toggled on and
off by the processing module 241 in respo~lse to the signal from the belt
encoder 238. Or the
scanner 236 may run continuously and the processing module 241 may respond to
the signal
from the belt encoder 238 by latching a control line to an input buffer of the
character
recognition system 240. Alternatively, the signal from the belt en~~oder 238
may be used as
an input to a software-based algorithm running on the processing module 241,
which triggers
the storage of video data from the scanner 236 in the computer .memory 242.
Many other
means known to those skilled in the art may equivalently be employed to
operate the
character recognition system 240 and the scanner 236 so as to store an image
of the region
250 in the computer memory 242.
3;:. f~o~.;eptable performance is experienced when : roving.-Light indicia
reader s;~stem
200 is configured as follows. '1 he belt encoder 238 is a standard belt-
driven, opto-mechanical
encoder that provides a signal indicating the linear displacement of the
conveyor 212. The
CA 02271063 2002-08-19
13
CCD array of the scanner 236 is cycled in response to the signal from the belt
encoder 238
to generate a series of analog images c>1' the scan line 2S2 that are
transmitted to an analog-to-
digital converter within the scanner 236. 'l~he analog-tcf-digital converter
of the scanner 236
uses a standard thresholding or similar process to convert the analog signal
produced by the
CCD array of the scantier 236 into an c;ight-bit digital video signal that is
transmitted via the
communication link 244 to the character recognition system 240, which is
operable for storing
the video data in the computer memory 242 for subsequent processing.
The scanner 236 is preferably a nlonc>cl~rotn e, 4,06 pixel line-scan type CCD
array such as one using a Thompson T'H7833A CCD chip. As the field of view of
the
scanner 236 is approximately 16 inches (41 cm) at the conveyor 212, the
resolution of the
image created by the scanner 236 is approximately 25fi pixels or "dots" per
inch (DPI) (101
dots per cm) across the field of view of the scanner 236. rl he belt encoder
238 preferably
triggers the CC.D array of the scanner 236 at a rate of approximately 256
cycles per inch (2.54
cm) so that the resolution of the image created by the scanner 236 is
approximately 2~6 pixels
Y
or "dots" per inch (DPI) ( 1 O 1 dots per cm) in the direction of conveyor
travel. It will
therefore be appreciated that a digital image with a correct aspect ratio
(i.e. the ratio of the
length of the image to the width) may be generated by the scanner 236 and
stored in the
computer memory 242 of the character recognition system 240 by synclwoni-ring
the cycling
rate of the scanner 236 with the linear speed of the conveyor 212.
The conveyor 212 may be approximately '24 inches (61 ctn) wide and travel at
linear speeds up to 20 inches per second or 100 feet per minute (51 cm per
second or 30
meters per minute) or more. 'hhe moving-light illumination source 224 is
preferably
positioned approximately 18 inches (46 cm) above conveyor 212 and defines a
spot 230 that
is approximately 1 inch (2.5 cm) wide anti 1 inch (2.S em) long at the
conveyor 212. The
moving-light illumination source 224 rnay be operated so that successive
moving spots 230
are spaced virtually any distance apart. l~'ar example, acceptable
pe~,rformance is experienced
when the moving-light indicia reader system 200 is operated with the conveyor
212 traveling
at 50 feet per minute (25 cm per second or 15 meters per minute) a.nd with the
moving spots
230 spaced 22 inches (56 cm) apart, which allows the moving-light indicia
reader system 200
to ?tandie approximately 1,636 parcels per hour if the operator places G
parcel under each
moving spot.
The scanner 236 is preferably mounted to have an optical path of approximately
CA 02271063 2002-08-19
13A
120 inches (305 cm) to the conveyor 212, with a 1 G inch (41 cm) field of view
at the
conveyor 212. To save space, the scanner 236 is positioned approximately 30
inches (76 em)
above the center of conveyer 212 and is pointed towards a c.omple:x of'
mirrors (not shown)
that increases the optical path from the scarmer 23fi to the conveyor 212 to
approximately 120
inches (305 cm). These parameters may be varied sonuewhat without unduly
affecting the
performance of the disclosed embodiment of the present invention.
It should also be understood that the scan line 252 may be longer than the
width
of the region stored in the computer mcn~ory 242. l~or example, the scanner
236 may be
positioned to have a field of view (i.e. the scan lice 252 equal to
approximately 16 inches (41
ctn) at the conveyor 212. lfhe region stcored in the cotnpttter n~emor,y 242,
however, may only
be approximately 4 inches (10 em) wide. This may be accomplished by canly
storing the
output ofa portion of the cells of tl~e scanner' 236 (e.g. the center 1,024
pixels of a 4,096
pixel scanner) in the computer memory 242.
It will be appreciated that the moving-light illumination source
224 should be long enough to allow an operator to position
the parcel 214 on the conveyor ~ 212 while the spot 230
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14
travels from the upstream end to the downstream end of the moving-light
illumination source
224. For example, a moving-ligtlt illumination source 224 having a length of
36 inches (91
cm) and 72 LEDs spaced 1/2 inch ( 1.3 crl~) apart is appropriate for the
conveyor 212 traveling at
inches per second or 50 feet per minute (25 crn per second or 15 meters per
minute), as
described above. T7ie LEDs 226a-n of the moving-light illumination source 224
may be any
of a variety of commercially available LEDs, such as a model AND190WOP
manufactured by
AND. The sensor assembly 232 may include any of a variety of commercially
available height
sensors, such as a model NR-40 manufactured by Lnnova Labs, Inc.
FIG. 4 is a diagram of a mufti-conveyor indicia reader system 400 that
includes a
10 plurality of moving-light indicia reader systems 210a through 210n, which
are virtually
identical to those described above with respect to F1(_IS. 2A-E. Each of the
moving-light indicia
reader systems 210a through 210n are synchronized by, and provide their video
data to, a
single character recognition system 240. 'the character recognition system 240
synchronizes
the moving spots 230a through 230n of the moving-light indicia reader systems
210a through
210n so as to time-division multiplex the storage of the regions 250a through
250n from the
several scanners 236a through 236n. In other wards, the spots 230a through
230n are
spaced relative to each other so that only one"of the regions 250a through
250n captured by the
scanners 236a through 236n needs to be stored in the computer memory 242 of
the character
recognition system 240 at any time. This allows the single character
recognition system 240 to
store the images generated by several moving-light indicia reader systems 210a
through 210n,
as shown in FIG. 4.
In view of the forgoing, it will be appreciated that the moving-light indicia
reader system
400 allows the video data stored in the computer memory 242 of the character
recognition
system 240 to be reduced to a standard-sized region that is only large enough
to capture the text
of the destination addresses 220a-220n on the various parcels carried on the
conveyors 2I2a-
212n. The use of projected illumination allows the operator to view the spot
230a-230n
defined by each moving-light illumination source 224a-224n directly on the top
of the parcels
214a-214n. Thus, there is no displacement between -each spot 230a-230n and the
top of
each parcel 214a-214n that could cause parallax-related alignment errors with
tall parcels. In
addition, the moving-light indicia reader system 400 allows the angle of the
field of view of the
scanners 23ba-236n to be relatively narrow so that the scanners generates
sharp images of the
top of the parcels 214a-214n.
It should be understood that the foregoing relates only to specific
embodiments of the
present invention, and that numerous changes may be made therein without
departing from the
spirit and scope of the invention as ;retired by the following claim:;.
