U.S. patent application number 12/853833 was filed with the patent office on 2010-12-23 for hybrid laser scanning and imaging reader.
Invention is credited to Edward Barkan, Christopher Warren Brock, Bradley Carlson, Vladimir Gurevich.
Application Number | 20100320272 12/853833 |
Document ID | / |
Family ID | 39714119 |
Filed Date | 2010-12-23 |
United States Patent
Application |
20100320272 |
Kind Code |
A1 |
Carlson; Bradley ; et
al. |
December 23, 2010 |
HYBRID LASER SCANNING AND IMAGING READER
Abstract
An imaging module is supported by a housing of a reader for
electro-optically reading indicia. The imaging module includes a
solid-state imager having an array of image sensors for capturing
return light from the indicia during reading. A laser scanning
module is also supported by the housing and includes a scanner for
scanning at least one of a laser beam from a laser and a field of
view of a light detector in a scan pattern across the indicia
during reading. A controller is operatively connected to the
modules, and is operative for preventing reading interference
between the modules during reading.
Inventors: |
Carlson; Bradley;
(Huntington, NY) ; Barkan; Edward; (Miller Place,
NY) ; Gurevich; Vladimir; (Stony Brook, NY) ;
Brock; Christopher Warren; (Manorville, NY) |
Correspondence
Address: |
MOTOROLA, INC.;Penny Tomko
1303 EAST ALGONQUIN ROAD, IL01/3RD
SCHAUMBURG
IL
60196
US
|
Family ID: |
39714119 |
Appl. No.: |
12/853833 |
Filed: |
August 10, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11823817 |
Jun 28, 2007 |
7798410 |
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12853833 |
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Current U.S.
Class: |
235/462.07 ;
235/462.2; 235/462.22 |
Current CPC
Class: |
G06K 7/10712 20130101;
G06K 7/109 20130101; G06K 7/1096 20130101; G06K 7/10554 20130101;
G06K 2207/1011 20130101 |
Class at
Publication: |
235/462.07 ;
235/462.2; 235/462.22 |
International
Class: |
G06K 7/14 20060101
G06K007/14 |
Claims
1-22. (canceled)
23. A reader for electro-optically reading indicia, comprising: a
housing; an imaging module supported by the housing and including a
solid-state imager having an array of image sensors for capturing
return light from the indicia during reading; a laser scanning
module supported by the housing and including a scanner for
scanning at least one of a laser beam from a laser and a field of
view of a light detector in a scan pattern across the indicia
during reading; and a controller operatively connected to the
modules, for distinguishing between types of the indicia, and for
enabling one of the modules to read the indicia of one determined
type, and for enabling another of the modules to read the indicia
of another determined type.
24. A reader for electro-optically reading indicia located in a
range of working distances from the reader, comprising: a housing;
an imaging module supported by the housing and including a
solid-state imager having an array of image sensors for capturing
return light from the indicia during reading; a laser scanning
module supported by the housing and including a scanner for
scanning at least one of a laser beam from a laser and a field of
view of a light detector in a scan pattern across the indicia
during reading; and a controller operatively connected to the
modules, for distinguishing between the working distances of the
indicia, and for enabling one of the modules to read the indicia at
working distances close to the reader, and for enabling another of
the modules to read the indicia at working distances further from
the reader.
25. A reader for electro-optically reading indicia, comprising: a
housing; an imaging module supported by the housing and including a
solid-state imager having an array of image sensors for capturing
return light from the indicia; a laser scanning module supported by
the housing and including a scanner for scanning a laser beam in a
visible scan pattern across the indicia; and a controller
operatively connected to the modules, for enabling the laser
scanning module to scan the laser beam over the indicia prior to
reading to facilitate aiming of the reader at the indicia, and for
enabling one of the modules to read the indicia after aiming.
26-47. (canceled)
48. A method of electro-optically reading indicia, comprising the
steps of supporting an imaging module by a housing, and capturing
return light from the indicia during reading with a solid-state
imager having an array of image sensors; supporting a laser
scanning module by the housing, and scanning at least one of a
laser beam from a laser and a field of view of a light detector in
a scan pattern across the indicia during reading; and
distinguishing between types of the indicia, and enabling one of
the modules to read the indicia of one determined type, and
enabling another of the modules to read the indicia of another
determined type.
49. A method of electro-optically reading indicia located in a
range of working distances from the reader, comprising the steps of
supporting an imaging module by a housing, and capturing return
light from the indicia during reading with a solid-state imager
having an array of image sensors; supporting a laser scanning
module by the housing, and scanning at least one of a laser beam
from a laser and a field of view of a light detector in a scan
pattern across the indicia during reading; and distinguishing
between the working distances of the indicia, and enabling one of
the modules to read the indicia at working distances close to the
reader, and enabling another of the modules to read the indicia at
working distances further from the reader.
50. A method of electro-optically reading indicia, comprising the
steps of: supporting an imaging module by a housing, and capturing
return light from the indicia with a solid-state imager having an
array of image sensor; supporting a laser scanning module by the
housing, and scanning a laser beam in a visible scan pattern across
the indicia; and enabling the laser scanning module to scan the
laser beam over the indicia prior to reading to facilitate aiming
of the reader at the indicia, and enabling one of the modules to
read the indicia after aiming.
51. The method of claim 50, and projecting an aiming pattern on the
symbol which visibly indicates an entire extent of a field of view
of the imager.
Description
DESCRIPTION OF THE RELATED ART
[0001] Moving laser beam-based readers, in both handheld and
hands-free modes of operation, have been used to electro-optically
read coded symbols, particularly one-dimensional Universal Product
Code (UPC) type symbols, in supermarkets, warehouse clubs,
department stores, and other kinds of retailers for many years. A
laser generates a laser beam directed to a symbol associated with a
product for reflection and scattering from the symbol. A detector
having a field of view detects light of variable intensity
returning from the symbol. A scanner scans at least one of the
laser beam and the field of view in a scan pattern comprised of one
or more scan lines. When at least one of the scan lines sweeps over
the symbol, an electrical signal indicative of the intensity of the
detected return light is processed by signal processing circuitry
including a microprocessor; the symbol is read; and the product is
identified.
[0002] Imager-based readers, in both handheld and hands-free modes
of operation, have also been used to electro-optically read targets
such as coded symbols, particularly two-dimensional symbols, by
employing solid-state imagers to capture an image of each symbol.
The imager comprises an array of cells or photosensors, which
correspond to image elements or pixels in a field of view of the
imager. Such an array may be comprised of a one- or two-dimensional
charge coupled device (CCD) or a complementary metal oxide
semiconductor (CMOS) device, analogous to those devices used in a
digital camera to capture images.
[0003] The imager-based reader further typically includes an
illuminator to illuminate the symbol during its reading with
illumination light emitted from an illumination light source and
directed to the symbol for reflection therefrom. The illumination
light source may be located within and/or externally of the reader,
and comprises one or more light emitting diodes (LEDs). The
imager-based reader yet further includes electronic circuitry for
producing electrical signals indicative of the light captured by
the array, and a microprocessor for processing the electrical
signals to produce each captured image.
[0004] It is therefore known to use a solid-state imager for
capturing a monochrome image of a symbol as, for example, disclosed
in U.S. Pat. No. 5,703,349. It is also known to use a solid-state
imager with multiple buried channels for capturing a full color
image of a target as, for example, disclosed in U.S. Pat. No.
4,613,895. It is common to provide a two-dimensional CCD with a
640.times.480 resolution commonly found in VGA monitors, although
other resolution sizes are possible.
[0005] In the hands-free mode of either the moving laser beam-based
reader or the imager-based reader, an operator may slide or swipe
the product bearing the symbol past a window of either reader,
either from right to left, or from left to right, in a "swipe"
mode. Alternatively, the operator may present the symbol on the
product to an approximate central region of the respective window
in a "presentation" mode. The choice depends on operator preference
or on the layout of a workstation in which the reader is used.
[0006] In the handheld mode of either the moving laser beam-based
reader or the imager-based reader, the operator holds the
respective reader in his or her hand during reading and aims the
reader at the symbol to be read. The operator may first lift the
reader from a countertop or a support cradle. Once reading is
completed, the operator may return the reader to the countertop or
to the support cradle.
[0007] Although the moving laser beam-based reader and the
imager-based reader are generally satisfactory for their intended
purposes, their capabilities are limited in certain respects. The
moving laser beam-based reader works well in the handheld mode when
reading one-dimensional symbols, but does not read certain
two-dimensional symbols as well as the imager-based reader can, and
cannot read other two-dimensional symbols at all. Sometimes, the
moving laser beam-based reader is too big and bulky to pick up and
aim at a symbol easily. The imager-based reader, on the other hand,
works well in the hands-free mode for reading one- and
two-dimensional symbols, but it works poorly in the handheld mode
primarily due to its housing design, which fails ergonomically in
several ways.
[0008] Specifically, a housing of a known imager-based reader is
designed to be gripped between an operator's thumb, on one side of
the housing, and the operator's fingertips on the other side of the
housing, when picked up for handheld reading. This is an
uncomfortable grip. Also, reading of the known imager-based reader
is initiated by pressing one of two switches on a side of the
housing. The operator is required to press one of the switches
before aiming the reader at a symbol, and to release the button to
initiate image capture. When the button is pressed, an aiming spot
of light is projected on the symbol to facilitate aiming. When the
aiming spot is on the symbol, the switch is released, and the
reader decodes and reads the symbol. The aiming spot turns off when
the switch is released. If the switch is not pressed before aiming
the reader at a symbol, the reader will scan the symbol
automatically; however, this leaves open the possibility of
accidentally reading the wrong symbol as the reader is moved
towards the desired symbol to be read. Accidental reads waste time
and open the possibility of erroneously charging customers at
point-of-sale workstations, or of inaccurately recording scanned
inventory information, etc.
[0009] Another problem with the known imager-based readers is that
the aiming spot only indicates where a center of the imager's field
of view is. It does not give any visual indication of where the
edges of the field of view are. This is a significant handicap when
reading wide symbols, and particularly when reading the
two-dimensional symbols on the back of driver's licenses in most
states of the United States. To read easily, these two-dimensional
symbols must be positioned close to the reader where the field of
view of the imager extends only slightly beyond the ends of the
symbol. If the symbol is held further away, the imager does not
have adequate resolution to read some symbols and, if the symbol is
held closer, then the field of view will not cover the entire
symbol, thereby rendering the symbol unreadable. The known
imager-based reader provides no visual guidance to the operator
that helps the operator determine at what distance to hold the
symbol. Hence, the operator typically ends up waving the symbol
around until the right distance is finally found, at which time the
reader beeps to indicate that the symbol has been decoded. This is
a slow process and not acceptable for busy scanning
environments.
[0010] Another problem that the known imager-based reader fails to
address is that, when used in the hands-free mode, the reader needs
to have a somewhat limited working range (around six to eight
inches), or the reader will accidentally scan products that
customers place on the counter-top nearby. However, when used in
the handheld mode, the reader is better off with a greater working
range, which makes it easier to scan symbols on products that are
too big, heavy, or bulky to move close up to the reader.
SUMMARY OF THE INVENTION
[0011] One feature of the present invention resides, briefly
stated, in a reader for, and a method of, electro-optically reading
indicia, especially one- and/or two-dimensional symbols. Each
symbol includes elements of different light reflectivity, e.g.,
bars and spaces. The reader could be configured, in one embodiment,
as a hands-free and/or a hand-held housing having a window. The
housing may have a handle for handheld operation and/or a base for
supporting the housing on a support surface for hands-free
operation. Preferably, the base is connected to the housing in both
the handheld and hands-free modes by being pivotably connected to
the handle. Also, the housing is preferably configured with a
gun-shaped configuration, and a manually actuatable trigger is
provided on the housing at a location underlying an operator's
forefinger when the operator holds the handle in the operator's
hand. In another embodiment, the reader could be configured as a
stationary bi-optic housing having dual windows.
[0012] In some applications, each window could be omitted, in which
event, the reader has a windowless opening at which the indicia are
located for reading. As used herein, the term "presentation area"
is intended to cover both a window and a windowless opening. In the
case of the hands-free reader, the symbol is swiped past, or
presented to, the presentation area and, in the case of the
handheld reader, the reader itself is moved and the presentation
area is aimed at the symbol. In the preferred embodiments, the
reader is installed in a retail establishment, such as a
supermarket, especially in a cramped environment.
[0013] An imaging module is supported by the housing, and includes
a one- or two-dimensional, solid-state imager mounted in the
reader. The imager has an array of image sensors operative,
together with a focusing lens assembly, for capturing light from a
one- or two-dimensional symbol or target through the presentation
area during the reading to produce a captured image. Preferably,
the array is a CCD or a CMOS array. When the reader is operated in
low light or dark ambient environments, the imaging module includes
an illuminator for illuminating the symbol during the reading with
illumination light directed from an illumination light source
through the presentation area. The illumination light source
comprises one or more light emitting diodes (LEDs).
[0014] A laser scanning module is also supported by the housing and
includes a scanner for scanning at least one of a laser beam from a
laser and a field of view of a light detector in a scan pattern,
typically comprised of one or more scan lines, across the indicia
during reading. The laser scanning module may also include signal
processing circuitry for processing an electrical analog signal
generated by the light detector, and a digitizer for converting the
analog signal to a digital signal for subsequent decoding.
[0015] In accordance with one aspect of this invention, a
controller, especially but not necessarily operative for decoding
the digital signal, is operatively connected to the modules, for
preventing reading interference between the modules during reading.
For example, a mode sensor is employed for detecting the mode of
operation; and the controller enables the laser scanning module to
read the indicia when the mode sensor detects the handheld mode,
and enables the imaging module to read the indicia when the mode
sensor detects the hands-free mode. The mode sensor is operative
for detecting the mode of operation by sensing one of motion,
position and orientation of the housing.
[0016] As another example, the controller enables the imaging
module to capture the return light during an exposure time of a
frame, and downloads data generated by the imager during a read-out
time of the frame; and the controller enables the laser scanning
module to scan the indicia during the read-out time to prevent
reading interference with the imaging module.
[0017] As still another example, the controller energizes the
illuminator for illuminating the indicia during reading with the
illumination light directed from the illuminating light source
during the exposure time, and the controller disables the
illuminating light source during the read-out time to prevent
reading interference between the modules.
[0018] As yet another example, the illumination light and the laser
beam have different frequencies to prevent reading interference
between the modules.
[0019] Additionally, the controller advantageously turns the laser
beam off during scanning, for example, at the end regions of the
scan lines; and the controller enables the imaging module to
capture the return light when the laser beam is turned off, again
to prevent reading interference with the laser scanning module.
[0020] The housing may be configured to block the laser beam during
scanning, for example, at the end regions of the scan lines. In
that case, the controller enables the imaging module to capture the
return light when the laser beam is blocked to prevent reading
interference with the laser scanning module.
[0021] Another example resides in operating the scanner to sweep
through a scan angle larger than a field of view of the imager. The
controller enables the imaging module to capture the return light
when the laser beam is outside the field of view of the imager to
prevent reading interference between the modules.
[0022] In accordance with another aspect of the invention, the
controller is operative for distinguishing between types of the
indicia, e.g., one- or two-dimensional symbols, and for enabling
one of the modules to read the indicia of one determined type, and
for enabling another of the modules to read the indicia of another
determined type. For example, the laser scanning module is
especially good at reading one-dimensional symbols, and the imaging
module is especially good at reading two-dimensional symbols.
[0023] In accordance with still another aspect of the invention,
the controller is operative for distinguishing between working
distances at which the indicia are located relative to the reader,
and for enabling one of the modules to read the indicia at working
distances close to the reader, and for enabling another of the
modules to read the indicia at working distances further from the
reader. For example, the laser scanning module is especially good
at reading symbols that are further away from the reader due to its
large depth of field, and the imaging module is especially good at
reading symbols that are closer to the reader due to its smaller
depth of field. This increases the range of the reader.
[0024] In accordance with yet another aspect of the invention, the
controller is operative for enabling the laser scanning module to
scan the laser beam over the indicia prior to reading to facilitate
aiming of the reader at the indicia, and for enabling one of the
modules to read the indicia after aiming. In other words, the laser
scanning module not only performs its reading function, but also
assists the imaging module by performing an aiming function. The
scan pattern is visible on the symbol.
[0025] A secondary aiming light projector may be employed in the
imaging module to project a pattern of light that visibly indicates
to the operator where the periphery of the field of view of the
imager is. For example, the aiming light projector might project an
aiming pattern of light shaped like a cross, which consists of a
vertical line that matches the vertical dimensions of the field of
view, and also a horizontal line whose ends match the horizontal
width of the field of view. This projected aiming pattern should
grow at the same angular rate as the scan pattern so that it
properly indicates the extent of the field of view at any distance
from the reader. This aiming light pattern can be created using
either LED light or laser light. The aiming light projector makes
it easy to scan difficult to read driver's licenses by clearly
indicating to the operator where the periphery of the field of view
of the imager is, so as to facilitate fitting the driver's license
symbol entirely within the field of view.
[0026] In the preferred embodiment, a horizontal line of the aiming
pattern can be created by a scanned laser line projected from the
laser scanning module. The scan angle of the scanned laser beam is
adjusted to match the divergence angle of the field of view of the
imager so that the ends of the visible scan line is a visible
indication of the ends of the imager's field of view. The operator
can now use the laser scan line as a guide to properly position a
symbol in front of the imager, for subsequent decoding. The symbol
can also be decoded by the laser scanning module if both modules
are enabled to read at the same time. In some cases, the operator
may need to be able to selectively read a symbol that is positioned
close to other symbols, for example, in a barcode menu list. The
scan angle of the laser scanning module is adjustable to be reduced
to a short line to facilitate aiming in these applications.
[0027] The invention still further resides in a method of
electro-optically reading indicia, by supporting an imaging module
by a housing, and capturing return light from the indicia by the
imaging module during reading with a solid-state imager having an
array of image sensors; by supporting a laser scanning module by
the housing, and scanning at least one of a laser beam from a laser
and a field of view of a light detector in a scan pattern across
the indicia by the laser scanning module during reading; and by
preventing reading interference between the modules during
reading.
[0028] The reading interference is prevented in various ways. For
example, the imaging module is enabled to capture the return light
during an exposure time of a frame, and data generated by the
imager is downloaded during a read-out time of the frame. The laser
scanning module is enabled to scan the indicia during the read-out
time to prevent reading interference with the imaging module. Also,
the imaging module illuminates the indicia during reading with the
illumination light during the exposure time, and the illuminating
light is disabled during the read-out time to prevent reading
interference between the modules. The illumination light and the
laser beam are advantageously selected to have different
frequencies to prevent reading interference between the modules.
The laser beam is turned off during scanning; and the return light
is captured when the laser beam is turned off, again to prevent
reading interference with the laser scanning module. The laser beam
is blocked during scanning; and the return light is captured when
the laser beam is blocked to prevent reading interference with the
laser scanning module. The laser beam is swept through a scan angle
larger than a field of view of the imager, and the return light is
captured when the laser beam is outside the field of view of the
imager to prevent reading interference between the modules.
[0029] The invention yet further resides in a method of
electro-optically reading indicia, comprising the steps of holding
a housing by a handle held by an operator in a handheld mode of
operation, and supporting the housing by a base on a support
surface during a hands-free mode of operation; supporting an
imaging module by the housing, and capturing return light from the
indicia during reading with a solid-state imager having an array of
image sensors; supporting a laser scanning module by the housing,
and scanning at least one of a laser beam from a laser and a field
of view of a light detector in a scan pattern across the indicia
during reading; detecting the mode of operation; and enabling the
laser scanning module to read the indicia when the handheld mode is
detected, and enabling the imaging module to read the indicia when
the hands-free mode is detected.
[0030] The invention additionally resides in a method of
electro-optically reading indicia, comprising the steps of:
supporting an imaging module by a housing, and capturing return
light from the indicia during reading with a solid-state imager
having an array of image sensors; supporting a laser scanning
module by the housing, and scanning at least one of a laser beam
from a laser and a field of view of a light detector in a scan
pattern across the indicia during reading; and distinguishing
between types of the indicia, and enabling one of the modules to
read the indicia of one determined type, and enabling another of
the modules to read the indicia of another determined type.
[0031] The invention also resides in a method of electro-optically
reading indicia located in a range of working distances from the
reader, comprising the steps of: supporting an imaging module by a
housing, and capturing return light from the indicia during reading
with a solid-state imager having an array of image sensors;
supporting a laser scanning module by the housing, and scanning at
least one of a laser beam from a laser and a field of view of a
light detector in a scan pattern across the indicia during reading;
and distinguishing between the working distances of the indicia,
and enabling one of the modules to read the indicia at working
distances close to the reader, and enabling another of the modules
to read the indicia at working distances further from the
reader.
[0032] The invention additionally resides in a method of
electro-optically reading indicia, comprising the steps of:
supporting an imaging module by a housing, and capturing return
light from the indicia with a solid-state imager having an array of
image sensor; supporting a laser scanning module by the housing,
and scanning a laser beam in a visible scan pattern across the
indicia; and enabling the laser scanning module to scan the laser
beam over the indicia prior to reading to facilitate aiming of the
reader at the indicia, and enabling one of the modules to read the
indicia after aiming.
[0033] Hence, this invention proposes a hybrid, dual module, reader
that can be used as a presentation or swipe reader for hands-free
reading of one- or two-dimensional symbols, and also offers
excellent and intuitive "aim-and-shoot" ergonomics for handheld
reading of one- or two-dimensional symbols by providing a
gun-shaped housing having a trigger to be depressed by the
operator's forefinger. The reader gives a clear visual indication
of the extent of its field of view, to facilitate reading of wide
targets like driver's licenses and two-dimensional symbols in
either the hands-free or handheld mode. In addition, the working
distance range increases in the handheld mode as compared to the
hands-free mode.
[0034] The novel features which are considered as characteristic of
the invention are set forth in particular in the appended claims.
The invention itself, however, both as to its construction and its
method of operation, together with additional objects and
advantages thereof, will be best understood from the following
description of specific embodiments when read in connection with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 is a perspective view of an electro-optical reader
operative in either a hand-held mode, or a hands-free mode, for
reading indicia in accordance with this invention;
[0036] FIG. 2 is a broken-away, sectional view of the reader of
FIG. 1 schematically depicting various components therein;
[0037] FIG. 3 is a perspective view of a bi-optical reader
operative for reading indicia in accordance with this
invention;
[0038] FIG. 4 is a broken-away, sectional view of the reader of
FIG. 3 schematically depicting various components therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0039] Reference numeral 40 in FIG. 1 generally identifies an
electro-optical, portable reader having a gun-shaped housing 42
connected to a base 44. The base 44 rests on a countertop or
analogous support surface and serves for supporting the reader 40.
The reader 40 can thus be used in a hands-free mode as a stationary
workstation in which products bearing indicia, such as one- or
two-dimensional symbols, are presented to, or slid or swiped past,
a presentation area or window 46. The gun-shaped housing 42 also
has a handle that can be picked up by an operator off the
countertop and held in the operator's hand in a handheld mode. A
trigger 48 is located on the gun-shaped housing 42 at a location
underlying an operator's forefinger when the operator holds the
handle in the operator's hand in the handheld mode. The trigger 48
is manually depressed to initiate reading of the symbol. The handle
is permanently and pivotably connected to the base 44 in both the
handheld and hands-free modes for pivoting movement about a
generally horizontal pivot axis that is generally parallel to, and
elevated above, the countertop. The housing is adjustably tiltable
forward and back about the pivot axis in the hands-free mode to aim
the window 46 at the symbol to be read.
[0040] An imaging module 50 is supported by the housing 42, and
includes a one- or two-dimensional, solid-state imager 30 mounted
in the reader. The imager 30 has an array of image sensors
operative, together with a focusing lens assembly 31, for capturing
light from a one- or two-dimensional symbol or target through the
presentation area 46 during the reading to produce an electrical
signal indicative of a captured image for subsequent decoding.
Preferably, the array is a CCD or a CMOS array. When the reader 40
is operated in low light or dark ambient environments, the imaging
module 50 includes an illuminator 32 for illuminating the symbol
during the reading with illumination light directed from an
illumination light source through the presentation area 46. The
illumination light source comprises one or more light emitting
diodes (LEDs). An aiming light generator 34 may also be provided
for projecting an aiming light pattern or mark on the symbol prior
to reading.
[0041] In operation of the imaging module 50, a controller 70, as
described below, sends a command signal to pulse the illuminator
LEDs 32 for a short time period, say 500 microseconds or less, and
energizes the imager 40 during an exposure time period of a frame
to collect light from a target symbol during said time period. A
typical array needs about 33 milliseconds to read the entire target
image and operates at a frame rate of about 30 frames per second.
The array may have on the order of one million addressable image
sensors.
[0042] A laser scanning module 60 is also supported by the housing
42 and includes a scanner 62 for scanning at least one of a laser
beam from a laser 64 and a field of view of a light detector 66 in
a scan pattern, typically comprised of one or more scan lines,
across the indicia during reading. The laser scanning module 60 may
also include optics 61 for focusing the laser beam to have a large
depth of field, and a digitizer 68 for converting an electrical
analog signal generated by the detector 66 into a digital signal
for subsequent decoding,
[0043] In operation of the laser scanning module 60, the controller
70, as described below, energizes the laser to emit the laser beam,
and energizes the scanner to sweep the laser beam in the scan
pattern. The controller 70 also processes the digitized signal from
the digitizer 68.
[0044] In accordance with one aspect of this invention, a
programmed microprocessor or controller 70, especially but not
necessarily operative for decoding the digital signal from the
digitizer 68 or the electrical signal indicative of the captured
image from the imager 30, is operatively connected to the modules
50, 60 for preventing reading interference between the modules
during reading. For example, a mode sensor 72 is employed for
detecting the mode of operation; and the controller 70 enables the
laser scanning module 60 to read the indicia when the mode sensor
72 detects the handheld mode, and enables the imaging module 50 to
read the indicia when the mode sensor 72 detects the hands-free
mode. The mode sensor 72 is operative for detecting the mode of
operation by sensing one of motion, position and orientation of the
housing 42. For example, the mode sensor 72 can detect when the
reader 40 is lifted by means of a switch mounted on an underside of
the base 44, the switch being pushed in when the reader is on a
support surface, and the switch being released and moved outwards
when the reader 40 is lifted. The mode sensor 72 can also be an
orientation sensor or tilt switch for detecting whether or not the
reader is in a predetermined orientation. The mode sensor 72 can
also be an accelerometer for detecting motion when the reader is
lifted, or lack of motion when the reader is on the support
surface, thereby causing the reader to automatically switch between
modes.
[0045] As another example of preventing reader interference, the
controller 70 enables the imaging module 50 to capture the return
light during an exposure time of a frame, and downloads data
generated by the imager 30 during a read-out time of the frame; and
the controller 70 enables the laser scanning module 60 to scan the
indicia during the read-out time to prevent reading interference
with the imaging module 50.
[0046] As still another example, the controller 70 energizes the
illuminator 32 for illuminating the indicia during reading with the
illumination light directed from the illuminating light source
during the exposure time, and the controller 70 disables the
illuminating light source during the read-out time to prevent
reading interference between the modules 50, 60.
[0047] As yet another example, the illumination light and the laser
beam have different frequencies to prevent reading interference
between the modules 50, 60.
[0048] Additionally, the controller 70 advantageously turns the
laser beam off during scanning, for example, at the end regions of
the scan lines; and the controller 70 enables the imaging module 50
to capture the return light when the laser beam is turned off,
again to prevent reading interference with the laser scanning
module 60.
[0049] The housing 42 may be configured to block the laser beam
during scanning, for example, at the end regions of the scan lines.
In that case, the controller 70 enables the imaging module 50 to
capture the return light when the laser beam is blocked to prevent
reading interference with the laser scanning module 60.
[0050] Another example resides in operating the scanner 62 to sweep
through a scan angle larger than a field of view of the imager 30.
The controller 70 enables the imaging module 50 to capture the
return light when the laser beam is outside the field of view of
the imager 30 to prevent reading interference between the modules
50, 60.
[0051] In accordance with another aspect of the invention, the
controller 70 is operative for distinguishing between types of the
indicia, e.g., one- or two-dimensional symbols, and for enabling
one of the modules to read the indicia of one determined type, and
for enabling another of the modules to read the indicia of another
determined type. For example, the laser scanning module 60 is
especially good at reading one-dimensional symbols, and the imaging
module 50 is especially good at reading two-dimensional
symbols.
[0052] In accordance with still another aspect of the invention,
the controller 70 is operative for distinguishing between working
distances at which the indicia are located relative to the reader
40, and for enabling one of the modules to read the indicia at
working distances close to the reader, and for enabling another of
the modules to read the indicia at working distances further from
the reader. For example, the laser scanning module 60 is especially
good at reading symbols that are further away from the reader 40
due to its large depth of field, and the imaging module 50 is
especially good at reading symbols that are closer to the reader
due to its smaller depth of field. This increases the range of the
reader.
[0053] In accordance with yet another aspect of the invention, the
controller 70 is operative for enabling the laser scanning module
60 to scan the laser beam over the indicia prior to reading to
facilitate aiming of the reader 40 at the indicia, and for enabling
one of the modules to read the indicia after aiming. In other
words, the laser scanning module 60 not only performs its reading
function, but also assists the imaging module 50 by performing an
aiming function. The scan pattern is visible on the symbol.
[0054] FIG. 3 depicts a dual window, bi-optic, point-of-transaction
workstation or housing 10 used by retailers to process transactions
involving the purchase of products bearing an identifying symbol,
typically the UPC symbol described above. Housing 10 has a
generally horizontal window 12 set flush into a countertop 14, and
an upright window 16 set flush, or recessed, into a raised housing
portion 18 above the countertop 14. An operator 24 is shown holding
a product 26 bearing a symbol 28.
[0055] As shown in FIG. 4, the imaging module 50 including the
imager 30 and the illuminator 32 is mounted in the bi-optic housing
10. The laser scanning module 60 is also mounted in the bi-optic
housing 10. The modules 50, 60 could be dedicated to individual
windows as illustrated, or could share one or both of the windows
12, 16. The modules 50, 60 are operatively connected to the
controller 70 operative, as described above, for controlling the
operation of these modules. Preferably, the controller 70 is the
same as the one used for decoding light scattered from the indicia
and for processing and analyzing the captured target images.
[0056] Reading interference between the integrated laser scanning
and imaging modules is prevented in various ways. For example, the
imager 30 may have a short exposure time in a frame that is
typically about 25% or less of the frame read-out time. In the next
generation pico-imager in which a sixty frames per second frame
rate is employed, the frame read-out time is a minimum of about
16.67 ms and the exposure time is about 4 ms. Since this imager 30
has a global electronic shutter, return light is only captured
during the exposure time. Therefore, when the imager 30 is reading
out data but not exposing, the laser scanning module 60 can operate
without interfering with the imager module operation. Also, the
imager illuminator 32 is not switched on during this time, so it
does not interfere with the operation of the laser scanning module
60. The laser scanning module 60 can operate at a duty cycle of at
least about 75% and therefore there is very little impact on the
reader performance. If the exposure time of the imager 30 is short
enough, the two modules appear to operate concurrently. If the
exposure time is made very short (tenths of a millisecond), the
operation of the reader is practically not interrupted.
[0057] Another approach for multiplexing the laser scanning and
imaging modules is to use different wavelengths for the laser beam
and the illumination light, and to use optical filters in the
collection optics of each module to collect only the light
dedicated for each module. For example, the illumination light
could use a deeper red, blue, green or near infrared source, while
the laser beam could use a different red source.
[0058] Another approach would be to let the laser scanning module
continue operating, but ignore the pixels in the two-dimensional
image captured by the imaging module that are exposed to the laser
light.
[0059] Some laser scanning modules turn off the laser 64 near end
regions of each scan line, where the scanner 62 slows down and
reverses direction. If such a laser scanning module is used in
conjunction with an imaging module, then the modules can be
synchronized so that the illuminator 32 and the exposure time of
the imager 30 is activated during this laser-off time period when
the laser scanning module is not capturing symbol data. This
synchronization enables the two modules to operate without
interfering with each other at all. If the laser scanning module
provides an output start-of-scan (SOS) signal which indicates when
the scanner is at an end region of each scan line, then this SOS
signal can be used to synchronize the modules.
[0060] Many laser scanning modules employ an automatic gain control
(AGC) circuit whose behavior could be corrupted by the bright flash
of the illuminator LEDs 32 used by the imaging module. This could
degrade the performance of the laser scanning module. This problem
can be eliminated by disabling the AGC whenever the LEDs 42 are
flashed.
[0061] Some laser scanning modules do not turn off the laser 64 at
the end regions of each scan line. Even when this kind of laser
scanning module is used, it is still advantageous to synchronize
the imaging module with the SOS signal so as to flash the LEDs 32
and capture an image only when the laser beam is at or near one end
region of the scan line, since the laser does not scan well where
the laser beam slows down before reversing direction. The housing
of the reader can be designed to block the end region of each scan
line where the laser beam will be during the LEDs 32 flash, so that
operators do not attempt to place a symbol at the end of the scan
line where the reader may not read.
[0062] Another approach would be to design the laser scanning and
imaging modules such that the scan angle of the scanning laser beam
is larger than the field of view of the imager 30. The imager 30
can be synchronized to expose the image when the laser beam is
outside of the field of view of the imager 30, thereby eliminating
the interference between the modules. Similar to the description
above, the AGC of the laser scanning module can be disabled during
the illuminator 32 flash to eliminate the interference between the
modules.
[0063] As mentioned above, the LEDs 32 illuminate any symbol or
object placed in front of the reader. The secondary aiming light
projector 34 projects a pattern of light that visibly indicates to
the operator 24 where the periphery of the field of view of the
imager 30 is. For example, the aiming light projector 34 might
project an aiming pattern of light shaped like a cross, which
consists of a vertical line that matches the vertical dimensions of
the field of view, and also a horizontal line whose ends match the
horizontal width of the field of view. This projected aiming
pattern should grow at the same angular rate as the scan pattern so
that it properly indicates the extent of the field of view at any
distance from the reader. This aiming light pattern can be created
using either LED light or laser light. The aiming light projector
34 makes it easy to scan difficult to read driver's licenses by
clearly indicating to the operator where the periphery of the field
of view of the imager 30 is, so as to facilitate fitting the
driver's license symbol entirely within the field of view.
[0064] In the preferred embodiment, a horizontal line of the aiming
pattern can be created by a scanned laser line projected from the
laser scanning module 60. The scan angle of the scanned laser beam
is adjusted to match the divergence angle of the field of view of
the imager 30 so that the ends of the visible scan line is a
visible indication of the ends of the imager's field of view. The
operator can now use the laser scan line as a guide to properly
position a symbol in front of the imager 30, for subsequent
decoding. The symbol can also be decoded by the laser scanning
module if both modules are enabled to read at the same time. In
some cases, the operator may need to be able to selectively read a
symbol that is positioned close to other symbols, for example, in a
barcode menu list. The scan angle of the laser scanning module is
adjustable to be reduced to a short line to facilitate aiming in
these applications.
[0065] In the hands-free mode, the imaging module becomes the
primary reading module. An aiming pattern is not needed when
scanning one-dimensional symbols, which is the most common
application for this kind of reader, so that the laser 64 can be
turned off most of the time. If a two-dimensional symbol is
detected in front of the reader, then the laser 64 can be turned on
to help the operator align the two-dimensional symbol to the field
of view. After the two-dimensional symbol has been decoded, the
laser 64 will turn off automatically until the next two-dimensional
symbol is detected by the imager. Hence, the imager 30 is the
primary means of decoding symbols when in the hands-free mode, and
the laser 64 is used as an aiming guide. The secondary aiming
projector 34 other than the scanning laser 64 can be used to
augment a single scan line generated by the laser scanning
module.
[0066] In the handheld mode, the laser scanning module becomes the
primary reading module, and one-dimensional symbols represent the
majority of symbols to be read. Occasionally, the operator may want
to read a two-dimensional symbol, such as printed on a driver's
license. The operator can aim the reader at the two-dimensional
symbol, and the laser scanning module can recognize that it is
looking at a two-dimensional symbol by the unique start/stop
characters of the two-dimensional symbol, or by the structure of
the internal characters. When this happens, the imaging module will
be enabled to read the two-dimensional symbol, while the laser scan
line may continue to be used to aim the reader to position the
two-dimensional symbol within the field of view of the imager, as
described above.
[0067] In some cases, it might be desirable to have both modules
active at the same time. For example, in the handheld mode, the
laser scanning module will provide an extra range of working
distances, which is useful when reading one-dimensional symbols at
a distance, but the imager could be used to read one-dimensional
symbols omnidirectionally closer to the reader. The reader can
therefore be user-programmable to have either the laser scanning
module, or the imaging module, or both operational at the same
time, or exclusively, in either the hands-free or handheld mode, or
to have one module enable the other module, when necessary, as
described above. User-programmability can be via scanning special
command symbols with either reader, or by communication with a
host.
[0068] An alternative embodiment would be to use a linear imager in
place of the laser scanning module. In this case, the linear
illumination line of the linear imager would take the place of the
laser scan line for aiming. Switching between the linear imager and
area imager would be accomplished in the same ways, as described
above.
[0069] Another way to achieve similar results would be to use the
area imager to simulate a single line scanner when in handheld
mode. This can be accomplished by projecting a horizontal line of
LED light near the center of the field of view of the area imager,
and only using a central line or several central lines of the area
imager to decode with. This eliminates the need for a secondary
optical system for a linear imager or laser scanner, but does not
provide the added range of a laser or linear imager when in
handheld mode.
[0070] This invention enables, for the first time, a reader that
provides excellent scanning ergonomics in both hands-free and
handheld modes, and also provides optimum reading performance in
both modes. The scan angle of the laser scanning module is
advantageously matched to the field of view angle of the imager.
Switching between the modules depends on the mode being used, what
kind of symbology is being read, the working distance to the
symbol, or by being user-programmed to enable whichever module is
needed in either the handheld or hands-free mode.
[0071] Another improvement in the alternate modes of hands-free
scanning vs. "point and shoot" handheld scanning is to have longer
exposure time goals for the handheld mode. In the hands-free mode,
a short exposure time allows good tolerance of motion in the
presented symbol, and also limits the working distance range by
limiting the amount of illumination. In the handheld mode, the
reader can have a longer exposure as the symbol is not being
swiped, thereby allowing for significantly more working range.
[0072] It will be understood that each of the elements described
above, or two or more together, also may find a useful application
in other types of constructions differing from the types described
above. Thus, readers having different configurations can be
used.
[0073] While the invention has been illustrated and described as
integrating a laser scanning module and an imaging module in a
hybrid reader and method, it is not intended to be limited to the
details shown, since various modifications and structural changes
may be made without departing in any way from the spirit of the
present invention.
[0074] Without further analysis, the foregoing will so fully reveal
the gist of the present invention that others can, by applying
current knowledge, readily adapt it for various applications
without omitting features that, from the standpoint of prior art,
fairly constitute essential characteristics of the generic or
specific aspects of this invention and, therefore, such adaptations
should and are intended to be comprehended within the meaning and
range of equivalence of the following claims.
[0075] What is claimed as new and desired to be protected by
Letters Patent is set forth in the appended claims.
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