U.S. patent application number 14/278413 was filed with the patent office on 2015-11-19 for imaging module and reader for, and method of, illuminating and imaging targets to be read over an extended range of working distances.
This patent application is currently assigned to SYMBOL TECHNOLOGIES, INC.. The applicant listed for this patent is SYMBOL TECHNOLOGIES, INC.. Invention is credited to Wynn L. AKER, Edward D. BARKAN, Caihau CHEN, Wanli CHI, Mark E. DRZYMALA, David T. SHI, Chinh TAN.
Application Number | 20150334282 14/278413 |
Document ID | / |
Family ID | 53274825 |
Filed Date | 2015-11-19 |
United States Patent
Application |
20150334282 |
Kind Code |
A1 |
TAN; Chinh ; et al. |
November 19, 2015 |
IMAGING MODULE AND READER FOR, AND METHOD OF, ILLUMINATING AND
IMAGING TARGETS TO BE READ OVER AN EXTENDED RANGE OF WORKING
DISTANCES
Abstract
Targets to be read by image capture are illuminated and imaged
over an extended range of working distances. A near imager captures
return light over a relatively wide imaging field of view from a
target located in a close-in region of the range. A far imager
captures return light over a relatively narrow imaging field of
view from a target located in a far-out region of the range. A
single illuminating light assembly is shared by both the near and
far imagers. An illumination light source emits illumination light,
and an illuminating lens assembly optically modifies the emitted
illumination light, and simultaneously illuminates a wide
illumination field to illuminate the target located in the close-in
region of the range, and a narrow illumination field to illuminate
the target located in the far-out region of the range.
Inventors: |
TAN; Chinh; (Setauket,
NY) ; AKER; Wynn L.; (Manorville, NY) ;
BARKAN; Edward D.; (Miller Place, NY) ; CHEN;
Caihau; (Albany, NY) ; CHI; Wanli; (Stony
Brook, NY) ; DRZYMALA; Mark E.; (St James, NY)
; SHI; David T.; (Setauket, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SYMBOL TECHNOLOGIES, INC. |
Schaumburg |
NY |
US |
|
|
Assignee: |
SYMBOL TECHNOLOGIES, INC.
Schaumburg
NY
|
Family ID: |
53274825 |
Appl. No.: |
14/278413 |
Filed: |
May 15, 2014 |
Current U.S.
Class: |
348/360 ;
348/370 |
Current CPC
Class: |
G02B 7/021 20130101;
G06K 7/10811 20130101; H04N 5/2354 20130101; G06K 7/10801
20130101 |
International
Class: |
H04N 5/235 20060101
H04N005/235; H04N 5/225 20060101 H04N005/225; G02B 7/02 20060101
G02B007/02 |
Claims
1. An imaging module for illuminating and imaging illuminated
targets to be read by image capture over an extended range of
working distances away from the module, comprising: an imaging
assembly including a plurality of solid-state imagers, each having
an imaging array of image sensors, and an imaging lens assembly for
capturing return light over an imaging field of view from a target,
and for projecting the captured return light onto the respective
imaging array, one of the imagers being a near imager for capturing
the return light over a relatively wide imaging field of view from
a target located in a close-in region of the range, and another of
the imagers being a far imager for capturing the return light over
a relatively narrow imaging field of view from a target located in
a far-out region of the range; and a single illuminating light
assembly for shared use by both the near and far imagers, the
single illuminating light assembly including an illumination light
source for emitting illumination light, and an illuminating lens
assembly for optically modifying the emitted illumination light,
and for simultaneously illuminating a wide illumination field to
illuminate the target located in the close-in region of the range,
and a narrow illumination field to illuminate the target located in
the far-out region of the range.
2. The module of claim 1, wherein the illumination light source
constitutes a light emitting diode stationarily mounted on an
optical axis; and wherein the illuminating lens assembly includes a
collimating lens stationarily mounted on the optical axis, and a
lenslet component including an array of lenslets stationarily
arranged in a plane that is generally perpendicular to the optical
axis.
3. The module of claim 2, wherein the collimating lens constitutes
at least one of a convex lens and a gradient index lens having an
input surface on which the emitted illumination light is incident,
and an output surface from which the modified illumination light
exits as generally parallel light rays for incidence on the lenslet
component.
4. The module of claim 3, wherein a first group of the lenslets
generally located at a middle region of the lenslet component are
configured with a first focal length to optically modify the
incident light rays from the collimating lens to illuminate the
target located in the close-in region with the wide illumination
field, and wherein a second group of the lenslets generally located
at an outer region of the lenslet component are configured with a
different second focal length to optically modify the incident
light rays from the collimating lens to illuminate the target
located in the far-out region with the narrow illumination
field.
5. The module of claim 3, wherein all the lenslets generally
located at a middle region of the lenslet component are configured
with the same focal length to optically modify the incident light
rays from the collimating lens to illuminate the target located in
the close-in region with the wide illumination field, and wherein
the lenslet component has a bypass region generally located at an
outer region of the lenslet component in which the incident light
rays from the collimating lens bypass the lenslets to illuminate
the target located in the far-out region with the narrow
illumination field.
6. The module of claim 2, wherein the lenslets have individual
input aspherical surfaces on which the collimated illumination
light is incident, and individual output aspherical surfaces for
forming the respective illumination field.
7. The module of claim 6, wherein the output aspherical surfaces
are shifted relative to the input aspherical surfaces to steer the
wide illumination field toward the wide imaging field of view.
8. The module of claim 2, wherein some of the lenslets have
different optical properties than the remaining lenslets to form
the illumination fields with a generally uniform light intensity
distribution.
9. An imaging reader for reading targets by image capture over an
extended range of working distances, comprising: a housing having a
light-transmissive window; and an imaging module supported by the
housing and operative for illuminating and imaging the targets, the
module having an imaging assembly including a plurality of
solid-state imagers, each having an imaging array of image sensors,
and an imaging lens assembly for capturing return light through the
window over an imaging field of view from a target, and for
projecting the captured return light onto the respective imaging
array, one of the imagers being a near imager for capturing the
return light through the window over a relatively wide imaging
field of view from a target located in a close-in region of the
range, and another of the imagers being a far imager for capturing
the return light through the window over a relatively narrow
imaging field of view from a target located in a far-out region of
the range, and a single illuminating light assembly for shared use
by both the near and far imagers, the single illuminating light
assembly including an illumination light source for emitting
illumination light through the window, and an illuminating lens
assembly for optically modifying the emitted illumination light,
and for simultaneously illuminating a wide illumination field to
illuminate the target located in the close-in region of the range,
and a narrow illumination field to illuminate the target located in
the far-out region of the range.
10. The reader of claim 9, wherein the illumination light source
constitutes a light emitting diode stationarily mounted on an
optical axis; and wherein the illuminating lens assembly includes a
collimating lens stationarily mounted on the optical axis, and a
lenslet component including an array of lenslets stationarily
arranged in a plane that is generally perpendicular to the optical
axis.
11. The reader of claim 10, wherein the collimating lens
constitutes at least one of a convex lens and a gradient index lens
having an input surface on which the emitted illumination light is
incident, and an output surface from which the modified
illumination light exits as generally parallel light rays for
incidence on the lenslet component.
12. The reader of claim 11, wherein a first group of the lenslets
generally located at a middle region of the lenslet component are
configured with a first focal length to optically modify the
incident light rays from the collimating lens to illuminate the
target located in the close-in region with the wide illumination
field, and wherein a second group of the lenslets generally located
at an outer region of the lenslet component are configured with a
different second focal length to optically modify the incident
light rays from the collimating lens to illuminate the target
located in the far-out region with the narrow illumination
field.
13. The reader of claim 11, wherein all the lenslets generally
located at a middle region of the lenslet component are configured
with the same focal length to optically modify the incident light
rays from the collimating lens to illuminate the target located in
the close-in region with the wide illumination field, and wherein
the lenslet component has a bypass region generally located at an
outer region of the lenslet component in which the incident light
rays from the collimating lens bypass the lenslets to illuminate
the target located in the far-out region with the narrow
illumination field.
14. The reader of claim 10, wherein the lenslets have individual
input aspherical surfaces on which the collimated illumination
light is incident, and individual output aspherical surfaces for
forming the respective illumination field; and wherein the output
aspherical surfaces are shifted relative to the input aspherical
surfaces to steer the wide illumination field toward the wide
imaging field of view.
15. The reader of claim 10, wherein some of the lenslets have
different optical properties than the remaining lenslets to form
the illumination fields with a generally uniform light intensity
distribution.
16. The reader of claim 9, wherein the single illuminating light
assembly is located between the plurality of imagers, and wherein
at least one component of the illuminating light assembly is
adjustably positioned relative to at least one of the imagers and
the window to prevent stray illumination light that is reflected
off the window from entering at least one of the imaging fields of
view.
17. A method of illuminating and imaging illuminated targets to be
read by image capture over an extended range of working distances,
comprising: capturing return light with a near imager over a
relatively wide imaging field of view from a target located in a
close-in region of the range; capturing return light with a far
imager over a relatively narrow imaging field of view from a target
located in a far-out region of the range; optically modifying
illumination light emitted by a single illumination light source
shared by both the near and far imagers; and simultaneously
illuminating a wide illumination field to illuminate the target
located in the close-in region of the range, and a narrow
illumination field to illuminate the target located in the far-out
region of the range.
18. The method of claim 17, wherein the illuminating is performed
by stationarily mounting a collimating lens on an optical axis, and
by stationarily arranging a lenslet component having an array of
lenslets in a plane that is generally perpendicular to the optical
axis; and configuring a first group of the lenslets generally
located at a middle region of the lenslet component with a first
focal length to optically modify light rays from the collimating
lens to illuminate the target located in the close-in region with
the wide illumination field; and configuring a second group of the
lenslets generally located at an outer region of the lenslet
component with a different second focal length to optically modify
the light rays from the collimating lens to illuminate the target
located in the far-out region with the narrow illumination
field.
19. The method of claim 17, wherein the illuminating is performed
by stationarily mounting a collimating lens on an optical axis, and
by stationarily arranging a lenslet component having an array of
lenslets in a plane that is generally perpendicular to the optical
axis; and configuring all the lenslets generally located at a
middle region of the lenslet component with the same focal length
to optically modify light rays from the collimating lens to
illuminate the target located in the close-in region with the wide
illumination field; and configuring the lenslet component with a
bypass region generally located at an outer region of the lenslet
component in which the light rays from the collimating lens bypass
the lenslets to illuminate the target located in the far-out region
with the narrow illumination field.
20. The method of claim 17, wherein the illuminating is performed
by stationarily mounting a collimating lens on an optical axis, and
by stationarily arranging a lenslet component having an array of
lenslets in a plane that is generally perpendicular to the optical
axis; configuring some of the lenslets with different optical
properties than the remaining lenslets to form the illumination
fields with a generally uniform light intensity distribution.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to an imaging module
and an imaging reader for, and a method of, illuminating and
imaging targets to be read over an extended range of working
distances.
[0002] Solid-state imaging systems or imaging readers have been
used, in both handheld and/or hands-free modes of operation, to
electro-optically read targets, such as one- and two-dimensional
bar code symbol targets, and/or non-symbol targets, such as
documents. A handheld imaging reader includes a housing having a
handle held by an operator, and an imaging module, also known as a
scan engine, supported by the housing and aimed by the operator at
a target during reading. The imaging module includes an imaging
assembly having a solid-state imager or imaging sensor with an
array of photocells or light sensors, which correspond to image
elements or pixels in an imaging field of view of the imager, and
an imaging lens assembly for capturing return light scattered
and/or reflected from the target being imaged, and for projecting
the return light onto the array to initiate capture of an image of
the target. Such an imager may include a one- or two-dimensional
charge coupled device (CCD) or a complementary metal oxide
semiconductor (CMOS) device and associated circuits for producing
and processing electronic signals corresponding to a one- or
two-dimensional array of pixel data over the imaging field of view.
In order to increase the amount of the return light captured by the
array, for example, in dimly lit environments, the imaging module
generally also includes an illuminating light assembly for
illuminating the target with illumination light in an illumination
pattern for reflection and scattering from the target.
[0003] In some applications, for example, in warehouses having
targets on products located on high shelves, it is necessary that
such targets be capable of being read by the reader at an extended
range of working distances, for example, on the order of thirty to
fifty feet, away from the reader. For this purpose, it is known to
employ two imagers: a so-called near imager or camera to image
close-in targets over a relatively wide imaging field of view, and
a so-called far imager or camera to image far-out targets over a
relatively narrow imaging field of view. It is also known to employ
two illuminating light assemblies, each customized for each imager.
For example, the illuminating light assembly for the far-out
targets generally illuminates such far-out targets with more
intense, brighter illumination light as compared to the
illuminating light assembly for the close-in targets. It is further
known to employ zoom-type or liquid crystal-based illumination
mechanisms to sequentially illuminate targets at different working
distances from the reader.
[0004] Although generally satisfactory for its intended purpose,
the known use of two imagers and two illuminating light assemblies,
as well as the known use of zoom-type or liquid crystal-based
illumination mechanisms, increases the size, cost, electrical power
consumption, and complexity of the imaging module, and, in turn, of
the overall reader. Sequential switching between illuminating light
assemblies, and zooming between working distances, can cause the
illumination patterns to appear to flicker and can, in some cases,
annoy the operators of the readers, as well as bother nearby
bystanders or consumers. Zoom response times can be slow. Any
mechanical zoom part is subject to wear and tear and can produce
undesirable noise. Stray illumination light from the illuminating
light assemblies may, sometimes, interfere with the operation of
the imaging assembly, which can cause reading performance to
deteriorate.
[0005] Accordingly, there is a need to reduce the size, cost,
electrical power consumption, and complexity of the imaging module
and of the overall reader, to avoid flickering illumination light
patterns, to improve response times, to avoid wear and tear from
moving parts, and to prevent stray illumination light from
degrading reading performance.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0006] The accompanying figures, where like reference numerals
refer to identical or functionally similar elements throughout the
separate views, together with the detailed description below, are
incorporated in and form part of the specification, and serve to
further illustrate embodiments of concepts that include the claimed
invention, and explain various principles and advantages of those
embodiments.
[0007] FIG. 1 is a side elevational view of a portable imaging
reader operative for illuminating targets over an extended range of
working distances in accordance with this invention.
[0008] FIG. 2 is a schematic diagram of various components,
including imaging and illuminating light assemblies, of the reader
of FIG. 1.
[0009] FIG. 3 is an enlarged side sectional view depicting
operation of components of the illuminating light assembly of FIG.
2 in accordance with one embodiment of this invention.
[0010] FIG. 4 is an enlarged side sectional view depicting
operation of components of the illuminating light assembly of FIG.
2 in accordance with another embodiment of this invention.
[0011] FIG. 5 is an elevational view of a lenslet array component
of the illuminating light assembly of FIG. 2 in accordance with one
embodiment of this invention.
[0012] FIG. 6 is a sectional view of the lenslet array component of
FIG. 5.
[0013] FIG. 7 is a view analogous to FIG. 2, but showing the
reduction or elimination of stray illumination light from the
illuminating light assembly from entering the field of view of the
imaging assembly.
[0014] FIG. 8 is a view analogous to FIG. 4 in accordance with
still another embodiment of the illuminating light assembly of this
invention.
[0015] FIG. 9 is a view analogous to FIG. 4 in accordance with
another embodiment of the lenslet array component of this
invention.
[0016] FIG. 10 is a view analogous to FIG. 2, but showing the
steering of the wide illumination field to substantially overlap
the wide imaging field of view of the imaging assembly.
[0017] Skilled artisans will appreciate that elements in the
figures are illustrated for simplicity and clarity and have not
necessarily been drawn to scale. For example, the dimensions and
locations of some of the elements in the figures may be exaggerated
relative to other elements to help to improve understanding of
embodiments of the present invention.
[0018] The system and method components have been represented where
appropriate by conventional symbols in the drawings, showing only
those specific details that are pertinent to understanding the
embodiments of the present invention so as not to obscure the
disclosure with details that will be readily apparent to those of
ordinary skill in the art having the benefit of the description
herein.
DETAILED DESCRIPTION OF THE INVENTION
[0019] One aspect of the present disclosure relates to an imaging
module, also known as a scan engine, for illuminating and imaging
illuminated targets to be read by image capture over an extended
range of working distances away from the module. Another aspect of
the present disclosure relates to an imaging reader having a
housing for supporting the imaging module, and a light-transmissive
window on the housing. In both aspects, the imaging module
comprises an imaging assembly including a plurality of solid-state
imagers, each having an imaging array of image sensors, and an
imaging lens assembly for capturing return light over an imaging
field of view from a target, and for projecting the captured return
light onto the respective imaging array. One of the imagers is a
near imager or camera for capturing the return light over a
relatively wide imaging field of view from a target located in a
close-in region of the range. Another of the imagers is a far
imager or camera for capturing the return light over a relatively
narrow imaging field of view from a target located in a far-out
region of the range.
[0020] The imaging module further comprises a single illuminating
light assembly for shared use by both the near and far imagers.
Preferably, the single illuminating light assembly is located
between the near and far imagers. The single illuminating light
assembly includes an illumination light source, preferably a light
emitting diode (LED), for emitting illumination light, and an
illuminating lens assembly for optically modifying the emitted
illumination light, and for simultaneously illuminating a wide
illumination field to illuminate the target located in the close-in
region of the range, and a narrow illumination field to illuminate
the target located in the far-out region of the range. In
accordance with this disclosure, the use of a single illuminating
light assembly for simultaneously generating wide and narrow
illumination fields decreases the size, cost, electrical power
consumption, and complexity of the imaging module, and, in turn, of
the overall reader.
[0021] In a preferred construction, the LED is stationarily mounted
on an optical axis, and the illuminating lens assembly includes a
collimating lens that is also stationarily mounted on the optical
axis, and a lenslet component including an array of lenslets that
is stationarily arranged in a plane that is generally perpendicular
to the optical axis. The collimating lens constitutes a convex lens
or a gradient lens, either having an input surface on which the
emitted illumination light is incident, and an output surface from
which the modified illumination light exits as generally parallel
light rays for incidence on the lenslet component. In one
embodiment, a first group of the lenslets have aspheric surfaces
that are configured with a first focal length to optically modify
the incident light rays from the collimating lens to illuminate the
target located in the close-in region with the wide illumination
field, and a second group of the lenslets have aspheric surfaces
that are configured with a different second focal length to
optically modify the incident light rays from the collimating lens
to illuminate the target located in the far-out region with the
narrow illumination field. In another embodiment, all the lenslets
have aspheric surfaces that are configured with the same focal
length to optically modify the incident light rays from the
collimating lens to illuminate the target located in the close-in
region with the wide illumination field, and the lenslet component
is further formed with a bypass region in which the incident light
rays from the collimating lens bypass the lenslets to illuminate
the target located in the far-out region with the narrow
illumination field. The wide illumination field is preferably
formed by the lenslets generally located at the middle region of
the lenslet component, while the narrow illumination field is
preferably formed by the lenslets generally located at the outer
edge regions of the lenslet component.
[0022] Still another aspect of the present disclosure relates to a
method of illuminating and imaging illuminated targets to be read
by image capture over an extended range of working distances. The
method is performed by capturing return light with a near imager
over a relatively wide imaging field of view from a target located
in a close-in region of the range, by capturing return light with a
far imager over a relatively narrow imaging field of view from a
target located in a far-out region of the range, by optically
modifying illumination light emitted by a single illumination light
source shared by both the near and far imagers, and by
simultaneously illuminating a wide illumination field to illuminate
the target located in the close-in region of the range, and a
narrow illumination field to illuminate the target located in the
far-out region of the range.
[0023] Reference numeral 30 in FIG. 1 generally identifies an
ergonomic imaging reader configured as a gun-shaped housing having
an upper barrel or body 32 and a lower handle 28 tilted rearwardly
away from the body 32 at an angle of inclination, for example,
fifteen degrees, relative to the vertical. A light-transmissive
window 26 is located adjacent the front or nose of the body 32 and
is preferably also tilted at an angle of inclination, for example,
fifteen degrees, relative to the vertical. The imaging reader 30 is
held in an operator's hand and used in a handheld mode in which a
trigger 34 is manually depressed to initiate imaging of targets,
especially bar code symbols, to be read in an extended range of
working distances, for example, on the order of thirty to fifty
feet, away from the window 26. Housings of other configurations, as
well as readers operated in the hands-free mode, could also be
employed.
[0024] As schematically shown in FIG. 2, an imaging module 10 is
mounted in the reader 30 behind the window 26 and is operative, as
described below, for illuminating and imaging illuminated targets
to be read through the window 26 by image capture over an extended
range of working distances away from the module 10. A target may be
located anywhere in a working range of distances between a close-in
working distance (WD1) and a far-out working distance (WD2). In a
preferred embodiment, WD1 is either at, or about one-half inch
away, from the window 26, and WD2 is much further away, for
example, about thirty to fifty feet away from the window 26. The
module 10 includes an imaging assembly that has a near imaging
sensor or imager 12, and a near imaging lens assembly 16 for
capturing return light over a relatively wide imaging field of view
20, e.g., about thirty degrees, from a target located in a close-in
region of the range, e.g., from about one-half inch to about two
feet away from the window 26, and for projecting the captured
return light onto the near imager 12, as well as a far imaging
sensor or imager 14, and a far imaging lens assembly 18 for
capturing return light over a relatively narrow imaging field of
view 22, e.g., about sixteen degrees, from a target located in a
far-out region of the range, e.g., greater than about two feet away
from the window 26, and for projecting the captured return light
onto the far imager 14. Although only two imagers 12, 14 and two
imaging lens assemblies 16, 18 have been illustrated, it will be
understood that more than two can be provided in the module 10. For
example, a first imager can read targets in an up-close region from
about six inches to about two feet away from the window 26; a
second imager can read targets in a mid-range region from about two
feet to about ten feet away from the window 26; and a third imager
can read targets in a far-range region from about ten feet to about
fifty feet away from the window 26.
[0025] Each imager 12, 14 is a solid-state device, for example, a
CCD or a CMOS imager having a one-dimensional array of addressable
image sensors or pixels arranged in a single, linear row, or
preferably a two-dimensional array of such sensors arranged in
mutually orthogonal rows and columns, preferably with an anamorphic
field of view, and operative for detecting return light captured by
the respective imaging lens assemblies 16, 18 along respective
imaging axes 24, 36 through the window 26. Each imaging lens
assembly is advantageously a Cooke triplet, although other lens
combinations can also be employed.
[0026] As also shown in FIG. 2, an illuminating light assembly is
also supported by the imaging module 10 and includes an
illumination light source, e.g., a light emitting diode (LED) 40,
stationarily mounted on an optical axis 42, and an illuminating
lens assembly that includes a collimating convex lens 50 also
stationarily mounted on the optical axis 42, and a lenslet
component 60 including an array of cells or lenslets 64 (see FIGS.
5-6) stationarily arranged in a plane that is generally
perpendicular to the optical axis 42. The stationary or fixed
mounting of the components of the illuminating light assembly in
the module 10 contrasts with known zooming mechanisms whose movable
parts are subject to wear and tear, and slow response times, and
produce objectionable noise.
[0027] As further shown in FIG. 2, the imagers 12, 14 and the LED
40 are operatively connected to a controller or microprocessor 80
operative for controlling the operation of these components. A
memory 82 is connected and accessible to the microprocessor 80.
Preferably, the microprocessor 80 is the same as the one used for
processing the return light from the targets and for decoding the
captured target images. In operation, the microprocessor 80 sends a
command signal to energize the LED 40 for a short exposure time
period, say 500 microseconds or less, and energizes and exposes the
imagers 12, 14 to collect the return light, e.g., illumination
light and/or ambient light, from the target only during said
exposure time period. A typical array needs about 18-33
milliseconds to acquire the entire target image and operates at a
frame rate of about 30-60 frames per second. An aiming light
assembly 84, including a laser and a diffractive or a refractive
optical element, is also energized and controlled by the
microprocessor 80 in those cases where it is desired to project an
aiming pattern on the target prior to reading.
[0028] As still further shown in FIG. 2, the LED 40 and the near
imager 12 are surface mounted on a printed circuit board (PCB) 86,
and the far imager 14, and, optionally, the microprocessor 80 the
memory 82, and the aiming light assembly 84, are surface mounted on
another PCB 88. The single illuminating light assembly is located
between the imaging assemblies such that the illumination axis 42
is located between, and is generally parallel to, the imaging
optical axes 24, 36 and achieves a highly compact configuration on
the order of 38 mm.times.19 mm.times.25 mm for the module. Other
physical layouts for these components are also contemplated.
[0029] FIGS. 3-4 illustrate two different embodiments of the LED
40, the collimating convex lens 50, and the lenslet component 60 of
the illuminating light assembly of FIG. 2. The collimating convex
lens 50 in both FIGS. 3-4 is a positive lens having an input
surface 52 on which the emitted illumination light from the LED 40
is incident, and an output surface 54 from which the modified
illumination light exits as generally parallel light rays 56 for
incidence on the lenslet component 60. The collimating lens 50
helps to maximize on-axis gain, and is especially useful for
far-range reading. The lenslets 64 of the lenslet component 50 in
both FIGS. 3-4 are preferably arranged in mutually orthogonal rows
and columns (see FIG. 5) and are commonly molded of a one-piece
construction, preferably of a light-transmissive plastic
material.
[0030] As best seen in FIG. 6, the lenslets 64 have individual
input aspherical surfaces 68 on which the collimated illumination
light rays 56 are incident, and individual output aspherical
surfaces 70 for simultaneously, i.e., non-sequentially,
illuminating both the wide and the narrow illumination fields. Each
aspherical surface can have two radii of curvature in the
horizontal and vertical directions. The size for each lenslet 64 is
typically within 1.times.1 mm (square or rectangular) and the
center thickness for each lenslet 64 is around 1.5 mm. The surfaces
68, 70 are optical quality grade surfaces with a high aspheric
coefficient. The surfaces 68, 70 could be symmetric or
non-symmetric about the center optical axis of each lenslet 64. The
optical property of both surfaces 68, 70 and the respective center
thickness determine the angular spread of the illumination field
coming out from that lenslet 64.
[0031] In FIG. 3, a first group (type A) of the lenslets 64
generally located at the middle region of the lenslet component 60
are configured with a first focal length to optically modify the
incident light rays 56 from the collimating lens 50 to illuminate
the target located in the close-in region with the wide
illumination field, and a second group (type B) of the lenslets 64
generally located at an outer peripheral annular edge region of the
lenslet component 60 are configured with a different second focal
length to optically modify the incident light rays 56 from the
collimating lens 50 to illuminate the target located in the far-out
region with the narrow illumination field.
[0032] In FIG. 4, all the lenslets 64 are configured with the same
focal length to optically modify the incident light rays 56 from
the collimating lens 50 to illuminate the target located in the
close-in region with the wide illumination field. In addition, the
lenslet component 60 has a bypass region 62 in which the incident
light rays 56 from the collimating lens 50 bypass the lenslets 64
to illuminate the target located in the far-out region with the
narrow illumination field. The bypass region 62 can, in its
simplest form, be a light-transmissive region with no optical
power. As before, the wide illumination field is preferably formed
by the lenslets 64 generally located at the middle region of the
lenslet component 60, while the narrow illumination field is
preferably formed by the bypass region 62 generally located at the
outer edge regions of the lenslet component 60.
[0033] The simultaneous, non-sequential, illumination of the wide
and narrow illumination fields avoids the aforementioned flickering
problem when zooming or switching between different illumination
patterns in the known art. The superposition of the wide and narrow
illumination fields can cause the illumination light distribution
to be non-uniform across the target. If a more uniform illumination
light distribution is desired, then some of the lenslets 64 may be
configured with different optical properties than the remaining
lenslets 64 in order to shape the illumination light distribution
as desired.
[0034] The location of the lenslet component 60 relative to the
collimating lens 50, as well as to the window 26, can be axially
and/or radially adjusted, if necessary, to avoid reflections of the
illumination light back to either imager 12, 14. As shown in FIG.
7, if an illumination light ray 72 is reflected off the window 26
as a reflected ray 74, then the reflected ray 74 will not enter the
wide imaging field of view 20 of the near imager 12. Thus, any
stray illumination light is reliably prevented from degrading
reading performance.
[0035] The collimating lens 50 need not be a convex lens as best
illustrated in FIGS. 3-4, but could also be a gradient index lens
76 as shown in FIG. 8. In a gradient index lens, its index of
refraction increases in a radial direction away from the optical
axis 42. Otherwise, the embodiment of FIG. 8 is essentially the
same as described above for FIG. 4.
[0036] FIG. 9 discloses another version of a lenslet component 80
having an array of lenslets 86 bounded by individual input
aspherical surfaces 82 on which the collimated illumination light
rays 56 are incident, and individual output aspherical surfaces 84
for simultaneously, i.e., non-sequentially, illuminating both the
wide and the narrow illumination fields, as described above.
However, in contrast to the lenslet component 60 of FIG. 6 wherein
the surfaces 68, 70 of the lenlets 64 are mirror symmetrical, the
surfaces 82, 84 of the lenlets 86 shown in FIG. 9 are not. Instead,
the surfaces 84 are shifted relative to the surfaces 82.
[0037] Put another way, the vertices between adjacent surfaces 82
are not aligned with the vertices between adjacent surfaces 84 and,
indeed, are shifted by a distance D. This feature is used for
directing the illumination light in a desired direction that is
other than perpendicular relative to the window 26, and is
especially desirable to reduce the parallax between the wide
illumination field and the near imager when reading targets located
in the close-in region where the parallax effect is more prominent.
This is shown in FIG. 10, wherein the lenslet component 80 directs
the illumination light along a steering axis 88, which is inclined
relative to the optical axis 42. The wide illumination field
substantially overlaps the wide imaging field of view 20 of the
near imager 12.
[0038] In the foregoing specification, specific embodiments have
been described. However, one of ordinary skill in the art
appreciates that various modifications and changes can be made
without departing from the scope of the invention as set forth in
the claims below. Accordingly, the specification and figures are to
be regarded in an illustrative rather than a restrictive sense, and
all such modifications are intended to be included within the scope
of present teachings.
[0039] The benefits, advantages, solutions to problems, and any
element(s) that may cause any benefit, advantage, or solution to
occur or become more pronounced are not to be construed as a
critical, required, or essential features or elements of any or all
the claims. The invention is defined solely by the appended claims
including any amendments made during the pendency of this
application and all equivalents of those claims as issued.
[0040] Moreover in this document, relational terms such as first
and second, top and bottom, and the like may be used solely to
distinguish one entity or action from another entity or action
without necessarily requiring or implying any actual such
relationship or order between such entities or actions. The terms
"comprises," "comprising," "has," "having," "includes,"
"including," "contains," "containing," or any other variation
thereof, are intended to cover a non-exclusive inclusion, such that
a process, method, article, or apparatus that comprises, has,
includes, contains a list of elements does not include only those
elements, but may include other elements not expressly listed or
inherent to such process, method, article, or apparatus. An element
proceeded by "comprises . . . a," "has . . . a," "includes . . .
a," or "contains . . . a," does not, without more constraints,
preclude the existence of additional identical elements in the
process, method, article, or apparatus that comprises, has,
includes, or contains the element. The terms "a" and "an" are
defined as one or more unless explicitly stated otherwise herein.
The terms "substantially," "essentially," "approximately," "about,"
or any other version thereof, are defined as being close to as
understood by one of ordinary skill in the art, and in one
non-limiting embodiment the term is defined to be within 10%, in
another embodiment within 5%, in another embodiment within 1%, and
in another embodiment within 0.5%. The term "coupled" as used
herein is defined as connected, although not necessarily directly
and not necessarily mechanically. A device or structure that is
"configured" in a certain way is configured in at least that way,
but may also be configured in ways that are not listed.
[0041] It will be appreciated that some embodiments may be
comprised of one or more generic or specialized processors (or
"processing devices") such as microprocessors, digital signal
processors, customized processors, and field programmable gate
arrays (FPGAs), and unique stored program instructions (including
both software and firmware) that control the one or more processors
to implement, in conjunction with certain non-processor circuits,
some, most, or all of the functions of the method and/or apparatus
described herein. Alternatively, some or all functions could be
implemented by a state machine that has no stored program
instructions, or in one or more application specific integrated
circuits (ASICs), in which each function or some combinations of
certain of the functions are implemented as custom logic. Of
course, a combination of the two approaches could be used.
[0042] Moreover, an embodiment can be implemented as a
computer-readable storage medium having computer readable code
stored thereon for programming a computer (e.g., comprising a
processor) to perform a method as described and claimed herein.
Examples of such computer-readable storage mediums include, but are
not limited to, a hard disk, a CD-ROM, an optical storage device, a
magnetic storage device, a ROM (Read Only Memory), a PROM
(Programmable Read Only Memory), an EPROM (Erasable Programmable
Read Only Memory), an EEPROM (Electrically Erasable Programmable
Read Only Memory) and a Flash memory. Further, it is expected that
one of ordinary skill, notwithstanding possibly significant effort
and many design choices motivated by, for example, available time,
current technology, and economic considerations, when guided by the
concepts and principles disclosed herein, will be readily capable
of generating such software instructions and programs and ICs with
minimal experimentation.
[0043] The Abstract of the Disclosure is provided to allow the
reader to quickly ascertain the nature of the technical disclosure.
It is submitted with the understanding that it will not be used to
interpret or limit the scope or meaning of the claims. In addition,
in the foregoing Detailed Description, it can be seen that various
features are grouped together in various embodiments for the
purpose of streamlining the disclosure. This method of disclosure
is not to be interpreted as reflecting an intention that the
claimed embodiments require more features than are expressly
recited in each claim. Rather, as the following claims reflect,
inventive subject matter lies in less than all features of a single
disclosed embodiment. Thus, the following claims are hereby
incorporated into the Detailed Description, with each claim
standing on its own as a separately claimed subject matter.
* * * * *