Title: METHOD OF SPECKLE-NOISE PATTERN REDUCTION AND APPARATUS THEREFOR BASED ON REDUCING THE TEMPORAL COHERENCE OF THE PLANAR LASER ILLUMINATION BEAM BEFORE IT ILLUMINATES THE TARGET OBJECT BY APPLYIN
Abstract: A planar laser illumination and imaging (PLIIM) based camera system capable of producing digital images with reduced levels of speckle-pattern noise. The PLIIM based camera system comprises a planar laser illumination array (PLIA) including a plurality of laser diodes for producing and projecting a planar laser illumination beam (PLIB), so as to illuminate an object as it is moving past said PLIIM based camera system. An image formation and detection (IFD) module is provided having a image detection array and imaging forming optics for providing said image detection array with a field of view (FOV). The PLIB and FOV are arranged in a coplanar relationship along the working range of the camera system so that the PLIB illuminates primarily within the FOV of the IFD module. A speckle-pattern noise reduction subsystem is integrated with the PLIA, for reducing the temporal-coherence of the PLIB before the PLIB illuminates a target object.
Patent Number: 6,991,165 Issued on 01/31/2006 to Tsikos, et al.
| Inventors:
|
Tsikos; Constantine J. (Voorhees, NJ);
Knowles; C. Harry (Moorestown, NJ);
Wirth; Allan (Bedford, MA);
Good; Timothy A. (Clementon, NJ);
Jankevics; Andrew (Westford, MA)
|
| Assignee:
|
Metrologic Instruments, Inc. (Blackwood, NJ)
|
| Appl. No.:
|
136182 |
| Filed:
|
April 30, 2002 |
| Current U.S. Class: |
235/462.01; 235/472.01 |
| Current Intern'l Class: |
G06K 7/10 (20060101) |
| Field of Search: |
235/46201-46247,472.01,472.02,472.03,454,455,470,494
|
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|
Primary Examiner: Le; Thien M.
Attorney, Agent or Firm: Perkowski, Esq., P.C.; Thomas J.
Parent Case Text
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS
This is a Continuation of copending application Ser. No. 09/990,585 filed Nov.
21, 2001 which is a Continuation-in-Part of: application Ser. No. 09/999,687 filed
Oct. 31, 2001, application Ser. No. 09/954,477 filed Sep. 17, 2001, now U.S. Pat.
No. 6,736,321; application Ser. No. 09/883,130 filed Jun. 15, 2001, now U.S. Pat.
No. 6,830,189, which is a Continuation-in-Part of application Ser. No. 09/781,665
filed Feb. 12, 2001, now U.S. Pat. No. 6,742,707; application Ser. No. 09/780,027
filed Feb. 9, 2001, now U.S. Pat. No. 6,629,641; application Ser. No. 09/721,885
filed Nov. 24, 2000, now U.S. Pat. No. 6,631,842; application Ser. No. 09/327,756
filed Jun. 7, 1999, now abandoned; and International application Ser. No. PCT/US00/15624
filed Jun. 7, 2000, published as WIPO WO 00/75856 A1; each said application being
commonly owned by Assignee, Metrologic Instruments, Inc., of Blackwood, N.J., and
incorporated herein by reference as if fully set forth herein in its entirety.
Claims
What is claimed is:
1. A method of reducing speckle-pattern noise at the image detection array of
a planar laser illumination and imaging (PLIIM) based camera system, said method
comprising the steps of:
(a) producing a planar laser illumination laser beam (PLIB) within a planar laser
illumination and imaging (PLIIM) based system including an image detection array
having image forming optics with a field of view (FOV) arranged in a coplanar relationship
with said PLIB;
(b) reducing the temporal-coherence of said PLIB before said PLIB illuminates
a target object, by applying a temporal intensity modulation technique during the
transmission of said PLIB towards the target, so that the object is illuminated
with a temporally coherent-reduced planar laser illumination beam (PLIB) and numerous
substantially different time-varying speckle-noise patterns are produced at said
image detection array over the photo-integration time period thereof;
(c) detecting said numerous substantially different time-varying speckle-noise
patterns over said photo-integration time period; and
(d) temporally averaging said detected speckle-noise patterns at said image detection
array during said photo-integration time period thereof, thereby reducing the RMS
power of observable speckle-noise patterns at said image detection array.
2. The method of claim 1, wherein the temporal intensity modulation technique
practiced during step (b) comprises:
modulating the temporal intensity of the transmitted PLIB along the planar extent
thereof according to a temporal intensity modulation function (TIMF) so as to modulate
the temporal intensity along the wavefront of the PLIB and produce said numerous
substantially different time-varying speckle-noise patterns at the image detection
array during the photo-integration time period thereof.
3. The method of claim 1, wherein the temporal intensity modulation technique
practiced during step (b) is selected from the group consisting of: using visible
mode-locked laser diodes (MLLDs) in a planar laser illumination array to produce
said transmitted PLIB; using electro-optical temporal intensity modulation panels
(i.e. shutters) along the optical path of the transmitted PLIB; using electrically-passive
optically-reflective cavities affixed external to laser diodes employed in said
PLIIM-based system; using electro-optical temporal intensity modulators disposed
along the optical path of a composite planar laser illumination beam; using laser
beam frequency-hopping devices; using internal and external type laser beam frequency
modulation (FM) devices; and using internal and external laser beam amplitude modulation
(AM) devices.
4. The method of claim 2, wherein step (b) comprises temporal intensity modulating
said PLIB employing high-speed beam gating/shutter principles, prior to target
object illumination.
5. The method of claim 2, wherein said PLIB is temporal intensity modulated prior
to target object illumination employing visible mode-locked laser diodes (MLLDs).
6. The method of claim 2, wherein said PLIB is temporal intensity modulated prior
to target object illumination employing current-modulated visible laser diodes
(VLDs) operated in accordance with temporal intensity modulation functions (TIMFS)
which exhibit a spectral harmonic constitution that results in a substantial reduction
in the RMS power of speckle-pattern noise observed at the image detection array
of PLIIM-based systems.
7. The method of claim 3, wherein said PLIB is temporal intensity modulated prior
to target object illumination, employing electro-optical temporal intensity modulation
panels (i.e. shutters) disposed along the optical path of the transmitted PLIB.
8. The method of claim 3, wherein said PLIB is temporal intensity modulated prior
to target object illumination employing electrically-passive optically-reflective
cavities affixed external to the VLD of a planar laser illumination module (PLIM)
employ in the PLIIM-based system.
9. The method of claim 3, wherein said PLIB is temporal intensity modulated prior
to target object illumination employing electro-optical temporal intensity modulators
disposed along the optical path of a composite planar laser illumination beam.
10. The method of claim 3, wherein said PLIB is temporal intensity modulated
prior to target object illumination employing laser beam frequency-hopping devices.
11. The method of claim 3, wherein said PLIB is temporal intensity modulated
prior to target object illumination, employing internal and/or external type laser
beam frequency modulation (FM) devices.
12. The method of claim 3, wherein said PLIB is temporal intensity modulated
prior to target object illumination, employing internal and external laser beam
amplitude modulation (AM) devices.
13. A planar laser illumination and imaging (PLIIM) based system capable of producing
digital images with reduced levels of speckle-pattern noise, said PLIIM-based camera
system having a working range and comprising:
a planar laser illumination array (PLIA) including a plurality of laser diodes
for producing and projecting a planar laser illumination beam (PLIB) so as to illuminate
an object as it is moving past said PLIIM-based PLIIM-based camera system;
an image formation and detection (IFD) module having an image detection array
and imaging forming optics for providing said image detection array with a field
of view (FOV),
wherein said PLIB and FOV are arranged in a coplanar relationship along the working
range of said PLIIM-based camera system so that the PLIB illuminates primarily
within said FOV of the IFD module; and
a speckle-pattern noise reduction subsystem, integrated with said PLIA, for reducing
the temporal-coherence of said PLIB before said PLIB illuminates a target object;
said speckle-pattern noise reduction subsystem applying a temporal intensity
modulation technique during the transmission of said PLIB towards the target, so
that the object is illuminated with a temporally coherent-reduced planar laser
illumination beam (PLIB) and numerous substantially different time-varying speckle-noise
patterns are produced at said image detection array over the photo-integration
time period thereof;
whereby said numerous substantially different time-varying speckle-noise patterns
are detected at said image detection array over said photo-integration time period,
and said detected speckle-noise patterns are temporally averaged at said image
detection array during said photo-integration time period thereof,
thereby reducing the RMS power of observable speckle-noise patterns at said image
detection array.
14. The PLIIM-based camera system of claim 13, wherein the temporal intensity
modulation technique comprises modulating the temporal intensity of the transmitted
PLIB along the planar extent thereof according to a temporal intensity modulation
function (TPMF) so as to modulate the temporal intensity along the wavefront of
the PLIB and produce said numerous substantially different time-varying speckle-noise
patterns at the image detection array during the photo-integration time period thereof.
15. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem is selected from the group consisting of: visible mode-locked
laser diodes (MLLDs) employed in said planar laser illumination array; electro-optical
temporal intensity modulation panels (i.e. shutters) disposed along the optical
path of the transmitted PLIB; electrically-passive optically-reflective cavities
affixed external to said laser diodes; electro-optical temporal intensity modulators
disposed along the optical path of a composite PLIB; laser beam frequency-hopping
devices; internal and external type laser beam frequency modulation (FM) devices;
and internal and external laser beam amplitude modulation (AM) devices.
16. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises high-speed beam gating/shutter principles for temporal
intensity modulating said planar laser illumination beam PLIB prior to target object illumination.
17. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises visible mode-locked laser diodes (MLLDs) for producing
a PLIB that is temporal intensity modulated prior to target object illumination.
18. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises current-modulated visible laser diodes (VLDs) operated
in accordance with temporal intensity modulation functions (TIMFS) which exhibit
a spectral harmonic constitution that results in a substantial reduction in the
RMS power of speckle-pattern noise observed at said image detection array of PLIIM-based system.
19. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises electro-optical temporal intensity modulation panels
(i.e. shutters) disposed along the optical path of the transmitted PLIB so that
said PLIB is temporal intensity modulated prior to target object illumination.
20. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises electrically-passive optically-reflective cavities
affixed external to said laser diodes in said PLIIM-based system, so that said
PLIB is temporal intensity modulated prior to target object illumination.
21. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises one or more electro-optical temporal intensity modulators
disposed along the optical path of said planar laser illumination beam so that
said PLIB is temporal intensity modulated prior to target object illumination.
22. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises a laser beam frequency-hopping device so that said
PLIB is temporal intensity modulated prior to target object illumination employing.
23. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises internal and/or external type laser beam frequency
modulation (FM) devices for temporal intensity modulating said PLIB is prior to
target object illumination.
24. The PLIIM-based camera system of claim 13, wherein said speckle-pattern noise
reduction subsystem comprises internal and/or external laser beam amplitude modulation
(AM) devices, for temporal intensity modulating said PLIB prior to target object illumination.
Description
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to improved methods of and apparatus
for illuminating moving as well as stationary objects, such as parcels, during
image formation and detection operations, and also to improved methods of and apparatus
and instruments for acquiring and analyzing information about the physical attributes
of such objects using such improved methods of object illumination, and digital
image analysis.
2. Brief Description of the State of Knowledge in the Art
The use of image-based bar code symbol readers and scanners is well known in
the field of auto-identification. Examples of image-based bar code symbol reading/scanning
systems include, for example, hand-hand scanners, point-of-sale (POS) scanners,
and industrial-type conveyor scanning systems.
Presently, most commercial image-based bar code symbol readers are constructed
using charge-coupled device (CCD) image sensing/detecting technology. Unlike laser-based
scanning technology, CCD imaging technology has particular illumination requirements
which differ from application to application.
Most prior art CCD-based image scanners, employed in conveyor-type package identification
systems, require high-pressure sodium, metal halide or halogen lamps and large,
heavy and expensive parabolic or elliptical reflectors to produce sufficient light
intensities to illuminate the large depth of field scanning fields supported by
such industrial scanning systems. Even when the light from such lamps is collimated
or focused using such reflectors, light strikes the target object other than where
the imaging optics of the CCD-based camera are viewing. Since only a small fraction
of the lamps output power is used to illuminate the CCD camera's field of view,
the total output power of the lamps must be very high to obtain the illumination
levels required along the field of view of the CCD camera The balance of the output
illumination power is simply wasted in the form of heat.
While U.S. Pat. No. 4,963,756 to Quan et al disclose a prior art CCD-based
hand-held image scanner using a laser source and Scheimpflug optics for focusing
a planar laser illumination beam reflected off a bar code symbol onto a 2-D CCD
image detector, U.S. Pat. No. 5,192,856 to Schaham discloses a CCD-based hand-held
image scanner which uses a LED and a cylindrical lens to produce a planar beam
of LED-based illumination for illuminating a bar code symbol on an object, and
cylindrical optics mounted in front a linear CCD image detector for projecting
a narrow a field of view about the planar beam of illumination, thereby enabling
collection and focusing of light reflected off the bar code symbol onto the linear
CCD image detector.
Also, in U.S. Provisional Application No. 60/190,273 entitled "Coplanar Camera"
filed Mar. 17, 2000, by Chaleff et al., and published by WIPO on Sep. 27, 2001
as part of WIPO Publication No. WO 01/72028 A1, both being incorporated herein
by reference, there is disclosed a CCD camera system which uses an array of LEDs
and a single apertured Fresnel-type cylindrical lens element to produce a planar
beam of illumination for illuminating a bar code symbol on an object, and a linear
CCD image detector mounted behind the apertured Fresnel-type cylindrical lens element
so as to provide the linear CCD image detector with a field of view that is arranged
with the planar extent of planar beam of LED-based illumination.
However, most prior art CCD-based hand-held image scanners use an array
of light emitting diodes (LEDs) to flood the field of view of the imaging optics
in such scanning systems. A large percentage of the output illumination from these
LED sources is dispersed to regions other than the field of view of the scanning
system. Consequently, only a small percentage of the illumination is actually collected
by the imaging optics of the system, Examples of prior art CCD hand-held image
scanners employing LED illumination arrangements are disclosed in U.S. Pat. No.
Re. 36,528, U.S. Pat. Nos. 5,777,314, 5,756,981, 5,627,358, 5,484,994, 5,786,582,
and 6,123,261 to Roustaei, each assigned to Symbol Technologies, Inc. and incorporated
herein by reference in its entirety. In such prior art CCD-based hand-held image
scanners, an array of LEDs are mounted in a scanning head in front of a CCD-based
image sensor that is provided with a cylindrical lens assembly. The LEDs are arranged
at an angular orientation relative to a central axis passing through the scanning
head so that a fan of light is emitted through the light transmission aperture
thereof that expands with increasing distance away from the LEDs. The intended
purpose of this LED illumination arrangement is to increase the "angular distance"
and "depth of field" of CCD-based bar code symbol readers. However, even with such
improvements in LED illumination techniques, the working distance of such hand-held
CCD scanners can only be extended by using more LEDs within the scanning head of
such scanners to produce greater illumination output therefrom, thereby increasing
the cost, size and weight of such scanning devices.
Similarly, prior art "hold-under" and "hands-free presentation" type CCD-based
image scanners suffer from shortcomings and drawbacks similar to those associated
with prior art CCD-based hand-held image scanners.
Recently, there have been some technological advances made involving the
use of laser illumination techniques in CCD-based image capture systems to avoid
the shortcomings and drawbacks associated with using sodium-vapor illumination
equipment, discussed above. In particular, U.S. Pat. No. 5,988,506 (assigned to
Galore Scantec Ltd.), incorporated herein by reference, discloses the use of a
cylindrical lens to generate from a single visible laser diode (VLD) a narrow focused
line of laser light which fans out an angle sufficient to fully illuminate a code
pattern at a working distance. As disclosed, mirrors can be used to fold the laser
illumination beam towards the code pattern to be illuminated in the working range
of the system. Also, a horizontal linear lens array consisting of lenses is mounted
before a linear CCD image array, to receive diffused reflected laser light from
the code symbol surface. Each single lens in the linear lens array forms its own
image of the code line illuminated by the laser illumination beam. Also, subaperture
diaphragms are required in the CCD array plane to (i) differentiate image fields,
(ii) prevent diffused reflected laser light from passing through a lens and striking
the image fields of neighboring lenses, and (iii) generate partially-overlapping
fields of view from each of the neighboring elements in the lens array. However,
while avoiding the use of external sodium vapor illumination equipment, this prior
art laser-illuminated CCD-based image capture system suffers from several significant
shortcomings and drawbacks. In particular, it requires very complex image forming
optics which makes this system design difficult and expensive to manufacture, and
imposes a number of undesirable constraints which are very difficult to satisfy
when constructing an auto-focus/auto-zoom image acquisition and analysis system
for use in demanding applications.
When detecting images of target objects illuminated by a coherent illumination
source (e.g. a VLD), "speckle" (i.e. substrate or paper) noise is typically modulated
onto the laser illumination beam during reflection/scattering, and ultimately speckle-noise
patterns are produced at the CCD image detection array, severely reducing the signal-to-noise
(SNR) ratio of the CCD camera system. In general, speckle-noise patterns are generated
whenever the phase of the optical field is randomly modulated. The prior art system
disclosed in U.S. Pat. No. 5,988,506 fails to provide any way of, or means for
reducing speckle-noise patterns produced at its CCD image detector thereof, by
its coherent laser illumination source.
The problem of speckle-noise patterns in laser scanning systems is mathematically
analyzed in the twenty-five (25) slide show entitled "Speckle Noise and Laser Scanning
Systems" by Sasa Kresic-Juric, Emanuel Marom and Leonard Bergstein, of Symbol Technologies,
Holtsville, N.Y., published at http://www.ima.umn.edu/industrial/99-2000/kresic/sld001.htm,
and incorporated herein by reference. Notably, Slide 11/25 of this WWW publication
summaries two generally well known methods of reducing speckle-noise by superimposing
statistically independent (time-varying) speckle-noise patterns: (1) using multiple
laser beams to illuminate different regions of the speckle-noise scattering plane
(i.e. object); or (2) using multiple laser beams with different wavelengths to
illuminate the scattering plane. Also, the celebrated textbook by J. C. Dainty,
et al, entitled "Laser Speckle and Related Phenomena" (Second edition), published
by Springer-Verlag, 1994, incorporated herein by reference, describes a collection
of techniques which have been developed by others over the years in effort to reduce
speckle-noise patterns in diverse application environments.
However, the prior art generally fails to disclose, teach or suggest how
such prior art speckle-reduction techniques might be successfully practiced in
laser illuminated CCD-based camera systems.
Thus, there is a great need in the art for an improved method of and apparatus
for illuminating the surface of objects during image formation and detection operations,
and also an improved method of and apparatus for producing digital images using
such improved methods object illumination, while avoiding the shortcomings and
drawbacks of prior art illumination, imaging and scanning systems and related methodologies.
OBJECTS AND SUMMARY OF THE PRESENT INVENTION
Accordingly, a primary object of the present invention is to provide
an improved method of and system for illuminating the surface of objects during
image formation and detection operations and also improved methods of and systems
for producing digital images using such improved methods object illumination, while
avoiding the shortcomings and drawbacks of prior art systems and methodologies.
Another object of the present invention is to provide such an improved method
of and system for illuminating the surface of objects using a linear array of laser
light emitting devices configured together to produce a substantially planar beam
of laser illumination which extends in substantially the same plane as the field
of view of the linear array of electronic image detection cells of the system,
along at least a portion of its optical path within its working distance.
Another object of the present invention is to provide such an improved method
of and system for producing digital images of objects using a visible laser diode
array for producing a planar laser illumination beam for illuminating the surfaces
of such objects, and also an electronic image detection array for detecting laser
light reflected off the illuminated objects during illumination and imaging operations.
Another object of the present invention is to provide an improved method
of and system for illuminating the surfaces of object to be imaged, using an array
of planar laser illumination modules which employ VLDs that are smaller, and cheaper,
run cooler, draw less power, have longer lifetimes, and require simpler optics
(i.e. because the spectral bandwidths of VLDs are very small compared to the visible
portion of the electromagnetic spectrum).
Another object of the present invention is to provide such an improved method
of and system for illuminating the surfaces of objects to be imaged, wherein the
VLD concentrates all of its output power into a thin laser beam illumination plane
which spatially coincides exactly with the field of view of the imaging optics
of the system, so very little light energy is wasted.
Another object of the present invention is to provide a planar laser illumination
and imaging (PLIIM) system, wherein the working distance of the system can be easily
extended by simply changing the beam focusing and imaging optics, and without increasing
the output power of the visible laser diode (VLD) sources employed therein.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein each planar laser illumination beam is focused so that
the minimum width thereof (e.g. 0.6 mm along its non-spreading direction) occurs
at a point or plane which is the farthest object distance at which the system is
designed to capture images.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein a fixed focal length imaging subsystem is employed,
and the laser beam focusing technique of the present invention helps compensate
for decreases in the power density of the incident planar illumination beam due
to the fact that the width of the planar laser illumination beam increases for
increasing distances away from the imaging subsystem.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein a variable focal length (i.e. zoom) imaging subsystem
is employed, and the laser beam focusing technique of the present invention helps
compensate for (i) decreases in the power density of the incident illumination
beam due to the fact that the width of the planar laser illumination beam (i.e.
beamwidth) along the direction of the beam's planar extent increases for increasing
distances away from the imaging subsystem, and (ii) any 1/r
2 type losses
that would typically occur when using the planar laser illumination beam of the
present invention.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein scanned objects need only be illuminated along a single
plane which is coplanar with a planar section of the field of view of the image
formation and detection module being used in the PLIIM system.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein low-power, light-weight, high-response, ultra-compact,
high-efficiency solid-state illumination producing devices, such as visible laser
diodes (VLDs), are used to selectively illuminate ultra-narrow sections of a target
object during image formation and detection operations, in contrast with high-power,
low-response, heavy-weight, bulky, low-efficiency lighting equipment (e.g. sodium
vapor lights) required by prior art illumination and image detection systems.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein the planar laser illumination technique enables modulation
of the spatial and/or temporal intensity of the transmitted planar laser illumination
beam, and use of simple (i.e. substantially monochromatic) lens designs for substantially
monochromatic optical illumination and image formation and detection operations.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein special measures are undertaken to ensure that (i)
a minimum safe distance is maintained between the VLDs in each PLIM and the user's
eyes using a light shield, and (ii) the planar laser illumination beam is prevented
from directly scattering into the FOV of the image formation and detection module
within the system housing.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein the planar laser illumination beam and the field of
view of the image formation and detection module do not overlap on any optical
surface within the PLIIM system.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein the planar laser illumination beams are permitted to
spatially overlap with the FOV of the imaging lens of the PLIIM only outside of
the system housing, measured at a particular point beyond the light transmission
window, through which the FOV is projected.
Another object of the present invention is to provide a planar laser illumination
(PLIM) system for use in illuminating objects being imaged.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein the monochromatic imaging module is realized as an
array of electronic image detection cells (e.g. CCD).
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein the planar laser illumination arrays (PLIAs) and the
image formation and detection (IFD) module (i.e. camera module) are mounted in
strict optical alignment on an optical bench such that there is substantially no
relative motion, caused by vibration or temperature changes, is permitted between
the imaging lens within the IFD module and the VLD/cylindrical lens assemblies
within the PLIAs.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein the imaging module is realized as a photographic image
recording module.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein the imaging module is realized as an array of electronic
image detection cells (e.g. CCD) having short integration time settings for performing
high-speed image capture operations.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein a pair of planar laser illumination arrays are mounted
about an image formation and detection module having a field of view, so as to
produce a substantially planar laser illumination beam which is coplanar with the
field of view during object illumination and imaging operations.
Another object of the present invention is to provide a planar laser illumination
and imaging system, wherein an image formation and detection module projects a
field of view through a first light transmission aperture formed in the system
housing, and a pair of planar laser illumination arrays project a pair of planar
laser illumination beams through second set of light transmission apertures which
are optically isolated from the first light transmission aperture to prevent laser
beam scattering within the housing of the system.
Another object of the present invention is to provide a planar laser illumination
and imaging system, the principle of Gaussian summation of light intensity distributions
is employed to produce a planar laser illumination beam having a power density
across the width the beam which is substantially the same for both far and near
fields of the system.
Another object of the present invention is to provide an improved method
of and system for producing digital images of objects using planar laser illumination
beams and electronic image detection arrays.
Another object of the present invention is to provide an improved method
of and system for producing a planar laser illumination beam to illuminate the
surface of objects and electronically detecting light reflected off the illuminated
objects during planar laser beam illumination operations.
Another object of the present invention is to provide a hand-held laser illuminated
image detection and processing device for use in reading bar code symbols and other
character strings.
Another object of the present invention is to provide an improved method
of and system for producing images of objects by focusing a planar laser illumination
beam within the field of view of an imaging lens so that the minimum width thereof
along its non-spreading direction occurs at the farthest object distance of the
imaging lens.
Another object of the present invention is to provide planar laser illumination
modules (PLIMs) for use in electronic imaging systems, and methods of designing
and manufacturing the same.
Another object of the present invention is to provide a Planar Laser Illumination
Module (PLIM) for producing substantially planar laser beams (PLIBs) using a linear
diverging lens having the appearance of a prism with a relatively sharp radius
at the apex, capable of expanding a laser beam in only one direction.
Another object of the present invention is to provide a planar laser illumination
module (PLIM) comprising an optical arrangement employs a convex reflector or a
concave lens to spread a laser beam radially and also a cylindrical-concave reflector
to converge the beam linearly to project a laser line.
Another object of the present invention is to provide a planar laser illumination
module (PLIM) comprising a visible laser diode (VLD), a pair of small cylindrical
(i.e. PCX and PCV) lenses mounted within a lens barrel of compact construction,
permitting independent adjustment of the lenses along both translational and rotational
directions, thereby enabling the generation of a substantially planar laser beam therefrom.
Another object of the present invention is to provide a multi-axis VLD mounting
assembly embodied within planar laser illumination array (PLIA) to achieve a desired
degree of uniformity in the power density along the PLIB generated from said PLIA.
Another object of the present invention is to provide a multi-axial VLD mounting
assembly within a PLIM so that (1) the PLIM can be adjustably tilted about the
optical axis of its VLD, by at least a few degrees measured from the horizontal
reference plane as shown in FIG. 1B4, and so that (2) each VLD block
can be adjustably pitched forward for alignment with other VLD beams.
Another object of the present invention is to provide planar laser illumination
arrays (PLIAs) for use in electronic imaging systems, and methods of designing
and manufacturing the same.
Another object of the present invention is to provide a unitary object attribute
(i.e. feature) acquisition and analysis system completely contained within in a
single housing of compact lightweight construction (e.g. less than 40 pounds).
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, which is capable of (1) acquiring and
analyzing in real-time the physical attributes of objects such as, for example,
(i) the surface reflectivity characteristics of objects, (ii) geometrical characteristics
of objects, including shape measurement, (iii) the motion (i.e. trajectory) and
velocity of objects, as well as (iv) bar code symbol, textual, and other information-bearing
structures disposed thereon, and (2) generating information structures representative
thereof for use in diverse applications including, for example, object identification,
tracking, and/or transportation/routing operations.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, wherein a multi-wavelength (i.e. color-sensitive)
Laser Doppler Imaging and Profiling (LDIP) subsystem is provided for acquiring
and analyzing (in real-time) the physical attributes of objects such as, for example,
(i) the surface reflectivity characteristics of objects, (ii) geometrical characteristics
of objects, including shape measurement, and (iii) the motion (i.e. trajectory)
and velocity of objects.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, wherein an image formation and detection
(i.e. camera) subsystem is provided having (i) a planar laser illumination and
imaging (PLIIM) subsystem, (ii) intelligent auto-focus/auto-zoom imaging optics,
and (iii) a high-speed electronic image detection array with height/velocity-driven
photo-integration time control to ensure the capture of images having constant
image resolution (i.e. constant dpi) independent of package height.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, wherein an advanced image-based bar
code symbol decoder is provided for reading 1-D and 2-D bar code symbol labels
on objects, and an advanced optical character recognition (OCR) processor is provided
for reading textual information, such as alphanumeric character strings, representative
within digital images that have been captured and lifted from the system.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system for use in the high-speed parcel, postal
and material handling industries.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, which is capable of being used to identify,
track and route packages, as well as identify individuals for security and personnel
control applications.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system which enables bar code symbol reading
of linear and two-dimensional bar codes, OCR-compatible image lifting, dimensioning,
singulation, object (e.g. package) position and velocity measurement, and label-to-parcel
tracking from a single overhead-mounted housing measuring less than or equal to
20 inches in width, 20 inches in length, and 8 inches in height.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system which employs a built-in source for producing
a planar laser illumination beam that is coplanar with the field of view (FOV)
of the imaging optics used to form images on an electronic image detection array,
thereby eliminating the need for large, complex, high-power power consuming sodium
vapor lighting equipment used in conjunction with most industrial CCD cameras.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, wherein the all-in-one (i.e. unitary)
construction simplifies installation, connectivity, and reliability for customers
as it utilizes a single input cable for supplying input (AC) power and a single
output cable for outputting digital data to host systems.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, wherein such systems can be configured
to construct multi-sided tunnel-type imaging systems, used in airline baggage-handling
systems, as well as in postal and parcel identification, dimensioning and sortation systems.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system, for use in (i) automatic checkout solutions
installed within retail shopping environments (e.g. supermarkets), (ii) security
and people analysis applications, (iii) object and/or material identification and
inspection systems, as well as (iv) diverse portable, in-counter and fixed applications
in virtual any industry.
Another object of the present invention is to provide such a unitary object
attribute acquisition and analysis system in the form of a high-speed object identification
and attribute acquisition system, wherein the PLIIM subsystem projects a field
of view through a first light transmission aperture formed in the system housing,
and a pair of planar laser illumination beams through second and third light transmission
apertures which are optically isolated from the first light transmission aperture
to prevent laser beam scattering within the housing of the system, and the LDIP
subsystem projects a pair of laser beams at different angles through a fourth light
transmission aperture.
Another object of the present invention is to provide a fully automated unitary-type
package identification and measuring system contained within a single housing or
enclosure, wherein a PLIIM-based scanning subsystem is used to read bar codes on
packages passing below or near the system, while a package dimensioning subsystem
is used to capture information about attributes (i.e. features) about the package
prior to being identified.
Another object of the present invention is to provide such an automated package
identification and measuring system, wherein Laser Detecting And Ranging (LADAR)
based scanning methods are used to capture two-dimensional range data maps of the
space above a conveyor belt structure, and two-dimensional image contour tracing
techniques and corner point reduction techniques are used to extract package dimension
data therefrom.
Another object of the present invention is to provide such a unitary system,
wherein the package velocity is automatically computed using package range data
collected by a pair of amplitude-modulated (AM) laser beams projected at different
angular projections over the conveyor belt.
Another object of the present invention is to provide such a system in which
the lasers beams having multiple wavelengths are used to sense packages having
a wide range of reflectivity characteristics.
Another object of the present invention is to provide an improved image-based
hand-held scanners, body-wearable scanners, presentation-type scanners, and hold-under
scanners which embody the PLIIM subsystem of the present invention.
Another object of the present invention is to provide a planar laser illumination
and imaging (PLIIM) system which employs high-resolution wavefront control methods
and devices to reduce the power of speckle-noise patterns within digital images
acquired by the system.
Another object of the present invention is to provide such a PLIIM-based
system, in which planar laser illumination beams (PLIBs) rich in spectral-harmonic
components on the time-frequency domain are optically generated using principles
based on wavefront spatio-temporal dynamics.
Another object of the present invention is to provide such a PLIIM-based
system, in which planar laser illumination beams (PLIBs) rich in spectral-harmonic
components on the time-frequency domain are optically generated using principles
based on wavefront non-linear dynamics.
Another object of the present invention is to provide such a PLIIM-based
system, in which planar laser illumination beams (PLIBs) rich in spectral-harmonic
components on the spatial-frequency domain are optically generated using principles
based on wavefront spatio-temporal dynamics.
Another object of the present invention is to provide such a PLIIM-based
system, in which planar laser illumination beams (PLIBs) rich in spectral-harmonic
components on the spatial-frequency domain are optically generated using principles
based on wavefront non-linear dynamics.
Another object of the present invention is to provide such a PLIIM-based
system, in which planar laser illumination beams (PLIBs) rich in spectral-harmonic
components are optically generated using diverse electro-optical devices including,
for example, micro-electro-mechanical devices (MEMs) (e.g. deformable micro-mirrors),
optically-addressed liquid crystal (LC) light valves, liquid crystal (L
