Imaging module, reader and method for reading targets by image acquisition with a substantially constant resolution over an extended range of working distances

Abstract

An imaging module (40) for reading targets (42, 46) electro-optically by capturing an image with a substantially constant resolution over an extended range of working distances away from the module (40), the module (40) comprising: an imaging system with an image sensor (24) having an array of pixels for detecting returning light from a first target (42) located at a first working distance relative to the module (40) over a relatively narrow field of view (44), and from a second target (46) located at a second working distance relative to the module (40) over a relatively wide field of view (48), the second working distance being closer to the module (40) than the first working distance; and a controller (36) operatively connected to the imaging system and operable to process the detected returning light from the first target (42) only from a set of the pixels located in a central region (50) of the array, and further operable to process the detected returning light from the second target (46) by grouping all of the pixels into bins (52), each bin (52) having a plurality of the pixels, and by processing the detected returning light from the second target (46) from each of the bins (52).

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates generally to an imaging module and an imaging reader for reading targets, such as barcode symbols, to be electro-optically read by an image pickup, with a substantially constant resolution over an extended range of working distances away from the module / reader.

[0002] Solid-state imaging systems and image readers have long been used in both handheld and hands-free modes in numerous industries, such as retail, manufacturing, warehousing, distribution, postal, transportation, logistics, etc., to electro-optically read targets such as one- or two-dimensional barcode symbols to be decoded.A known image reader generally includes an imaging module, also known as a scanning engine, housed in a housing and typically including an illumination system for projecting illumination light toward targets for reflection and scattering thereof, and an imaging system including a solid-state imager, also known as an image sensor, having an array of light sensors or pixels, and an imaging lens assembly for receiving returning illumination light scattered and / or reflected from the illuminated targets across a field of view and for projecting the received illumination light onto the imager to initiate capture of an image of each target.The imager generates electrical signals that are decoded and / or processed by a programmed microprocessor or controller into information related to each target being read, e.g., decoded data identifying each target. The controller is operable to transmit the decoded data, either via a wireless or wired connection, to a remote host for further processing, e.g., retrieving the price from a price database to obtain a price for each identified target.

[0003] The known imaging lens arrangement may be of the fixed-focus type and may be formed from a plurality or group of stationary lenses, such as a classic Cooke triplet, which has a center lens between a pair of side lenses. To image targets that can be positioned over an extended range of working distances relative to the reader, it is known to configure the fixed-focus reader with different lens configurations having different focal lengths, each designed to focus at a different working distance. However, such multiple lens configurations are costly and not easily versatile across a wide range of applications.

[0004] The known imaging lens assembly may also be of the variable-focus type and may be formed of one or more movable lenses moved, for example, by a moving-coil motor, to automatically focus a target between a near or zoomed-in working distance close to the reader and a far or zoomed-out working distance farther from the reader. However, this mechanical lens movement is disadvantageous for several reasons. First, the mechanical lens movement generates vibrations, which, in the case of a handheld reader, can propagate through the reader to the user's hand, generate dirt to obscure the lenses, and produce an objectionable, annoying, audible buzzing.In addition, the moving coil motor is very sensitive to hand movement, consumes electrical power, is expensive and notoriously slow, can be unreliable, takes up space, and increases the overall weight, size, and complexity of the reader.

[0005] Another problem associated with known image readers concerns the resolution, or level of detail, with which the image of each target is captured. A distant target located at the far working distance is best read by the imager over a relatively narrow field of view with high resolution because the apparent size of the distant target is relatively small. A close target located at the near working distance is best read by the imager over a relatively wide field of view because its apparent size is relatively large, and as a result of the close proximity of the near target, high resolution is not required by the imager.A multi-megapixel imager could provide high resolution for a distant target, but such an imager is not only expensive, but working with such a large number of pixels slows the imager's frame rate and also slows the processing of the electrical signals that must be decoded and processed. Such time delays negatively impact the reader's aggressiveness and can render its performance too slow in many applications.

[0006] US 2006 / 0 219 792 A1 describes a handheld, digital imaging-based barcode symbol reader. It includes an IR-based object presence and distance detection subsystem; a multi-mode area imaging and detection subsystem with narrow-area and wide-area image acquisition modes; a multi-mode LED-based illumination subsystem with narrow-area and wide-area illumination modes; an automatic exposure metering and illumination control subsystem; an image acquisition and buffering subsystem; a multi-mode image processing barcode symbol reading subsystem; an input / output subsystem; a manually activated trigger switch; a system mode configuration parameter table; and a system control subsystem integrated with each of the above-described subsystems.The barcode reader can be configured and operated in numerous programmable system operating modes to read 1D and 2D barcode symbologies automatically and at high speed using advanced image processing modes on captured images.

[0007] US 2010 / 0 147 956 A1 describes a character reading terminal capable of processing a frame of image data to attempt to decode a decodable character. A frame may be one of a sequence of frames to be processed following and during the time a trigger signal is active. Such a sequence of frames may include zero or more grouped frames, zero or more ungrouped frames, zero or more windowed frames, and zero or more unwindowed full frames. A character reading terminal may also include a variable focal length imaging lens.The control of the variable focal length imaging lens may be such that during an exposure period for a collimated image the variable focal length imaging lens is set to a close focus setting, and further such that during an exposure period for a windowed image the variable focal length imaging lens is set to a far focus setting.

[0008] EP 0 989 741 A2 describes a CMOS image sensor that can be embedded in portable imaging systems. This CMOS area image sensor with high spatial resolution and low bit resolution not only enables portable imaging systems such as mobile phones, fax machines, portable copiers, and barcode readers, but can also be manufactured using standard digital CMOS processes, particularly at 0.35 micrometers and below. Several portable imaging systems using such a CMOS image sensor are also disclosed. Likewise, a CMOS image sensor having variable spatial resolution and bit resolution is disclosed. Starting with an image sensor with high spatial resolution and low bit resolution, the high bit resolution is achieved by combining information from a group of nearest neighbor pixels through spatial oversampling into a single superpixel.This variable CMOS image sensor can be used in a multi-function imaging device for document, video, or photography.

[0009] US 2015 / 0 219 437 A1 describes a coded localization system with multiple optical channels arranged to collectively image at least one object on multiple detectors. Each of the channels contains a localization code that differs from all other localization codes in other channels to modify the electromagnetic energy flowing through it. Digital images output by the detectors can be processed to determine the subpixel localization of the object on the detectors, allowing the object's location to be determined more accurately than by detector geometry alone.

[0010] Accordingly, it would be desirable to electro-optically and rapidly read targets by imaging over an extended range of working distances at a substantially constant resolution. BRIEF DESCRIPTION OF THE MULTIPLE VIEWS OF THE DRAWINGS

[0011] The accompanying figures, in which like reference numerals designate identical or functionally similar elements throughout the separate views, together with the detailed description given below, are incorporated in and constitute a part of the specification and serve to further illustrate embodiments of concepts comprising the claimed invention and to explain various principles and advantages of those embodiments.

[0012] The drawings show: Fig. 1 is a perspective view of an exemplary embodiment of an electro-optical handheld reader for reading targets by image capture having an imaging module mounted thereon in accordance with this disclosure; Fig. 2 a diagrammatic view of components of the imaging, illumination, and distance measurement system on board the imaging module within the reader of the Fig. 1 for reading targets over an extended range of working distances; Fig. 3 an enlarged front view of an array of the image of the Fig. 2 and a diagrammatic representation of a set of the pixels arranged in a central region of the array for reading a distant target at a given resolution, in accordance with this disclosure; Fig. 4 an enlarged front view of the array of the image of the Fig. 3 and a diagrammatic representation of all pixels grouped into bins for reading a near target at substantially the same predetermined resolution, in accordance with this disclosure; and Fig. 5 is a flow diagram of steps performed in a method for reading targets by imaging at a substantially constant resolution over an extended range of working distances, in accordance with this disclosure.

[0013] Those of ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and are not necessarily 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 aid in an improved understanding of the embodiment of the present invention.

[0014] The module, reader, and method components have been illustrated in the drawings with conventional symbols where appropriate, showing only those specific details relevant to understanding embodiments of the present invention in order not to obscure the disclosure with details that will already be apparent to those of ordinary skill in the art having the benefit of the descriptions presented herein. DETAILED DESCRIPTIONS OF THE INVENTION

[0015] In accordance with one feature of this disclosure, an imaging module is operable to electro-optically read targets, e.g., barcode symbols, by capturing an image with a substantially constant resolution over an extended range of working distances away from the module. The module includes an imaging system having an image sensor, e.g., a two-dimensional solid-state device such as a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) device, comprising an array of pixels for detecting returning light from a first target located at a first working distance relative to the module over a relatively narrow field of view, and from a second target located at a second working distance relative to the module over a relatively wide field of view, the second working distance being closer to the module than the first working distance.Preferably, the pixels extend along mutually orthogonal horizontal and vertical axes for detecting the returning light from the targets along an imaging axis generally perpendicular to the horizontal and vertical axes. Advantageously, the pixels are arranged in a predetermined number of linear rows generally parallel to the horizontal axis and in a predetermined number of linear columns generally parallel to the vertical axis.

[0016] The module also includes a controller operatively connected to the imaging system. The controller processes the detected returning light from the first target only from a set of the pixels arranged in a central region of the array. Advantageously, the set of pixels arranged in the central region of the array forms a number of rows that is less than the predetermined number of rows and a number of columns that is less than the predetermined number of columns. The controller also processes the detected returning light from the second target by grouping all of the pixels into bins, each bin comprising a plurality of the pixels, and by processing the detected returning light from the second target from each of the bins. Each bin forms a single effective pixel that is larger than any individual pixel.The controller processes the detected returning light from the second target at a predetermined frame rate and processes the detected returning light from the first target at a frame rate greater than the predetermined frame rate. Preferably, a distance measurement signal system is used to determine the working distance to each target.

[0017] In accordance with another feature of this disclosure, the aforementioned imaging module is housed in an image reader housing having a light-transmitting window. The image sensor detects light returning from the target through the window. The housing is preferably implemented as a portable, point-of-sale, gun-shaped, and handheld housing, but could be implemented as a handheld, box-shaped housing or any other configuration including a hands-free configuration.

[0018] In accordance with yet another feature of this disclosure, a method for reading targets electro-optically by capturing an image with a substantially constant resolution over an extended range of working distances away from an array of pixels of an image sensor is performed by detecting returning light returning from a first target located at a first working distance relative to the array over a relatively narrow field of view and from a second target located at a second working distance relative to the array over a relatively wide field of view, and by processing the detected returning light from the first target only from a set of pixels located in a central region of the array.The method is further carried out by processing the detected returning light from the second target by grouping all of the pixels into bins, each bin comprising a plurality of the pixels, and processing the detected returning light from the second target from each of the bins.

[0019] Referring now to the drawings, reference numeral 30 in Fig. 1 generally describes a handheld image reader for reading targets electro-optically, such as barcode symbols or similar characters. The reader 30 includes a housing 32 in which an imaging or scanning engine or imaging module 40, as described below in connection with Fig. 2, is attached. The housing 32 includes a generally elongated, inclined handle or lower handgrip portion 28, and a cylindrical or upper body portion having a forward end at which a light-transmitting window 26 is located. The cross-sectional dimensions and overall size of the handle 28 are such that the reader 30 fits comfortably in the hand of an operator. The body and handle portions may be constructed of a lightweight, resilient, shock-absorbing, self-supporting material, such as a synthetic plastic. The plastic housing 32 may be injection molded, but may also be vacuum formed or blow molded to form a thin hollow shell defining an internal space of sufficient volume to accommodate the imaging module 40.A manually operable trigger 34 is mounted in a moving relationship on the handle 28 in a forward portion of the reader 30. An operator's index finger is used to trigger the reader 30 to initiate a reading operation by depressing the trigger 34. Although the housing 32 has been illustrated as a portable, point-of-sale, pistol-shaped, handheld housing, this is merely exemplary, as the housing could also be implemented as a handheld, box-shaped housing or any other configuration, including a hands-free configuration.

[0020] As shown schematically in Fig. 2, the imaging module 40 includes an imaging system having an image sensor or imager 24 mounted on a printed circuit board (PCB) 22 in the reader 30, and an imaging lens assembly 20 positioned in front of the imager 24. The imager 24 and the imaging lens assembly 20 are preferably aligned along a centerline or optical imaging axis 18 located generally centrally within the upper body portion of the housing 32. The PCB 22 is preferably housed within the inclined handle 28. The imager 24 is a solid-state device, for example, a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (COMS) device. The imager 24 includes a two-dimensional array of mutually orthogonal rows and columns of image sensors or pixels, as described below in connection with Fig. 3 and Fig. 4, which extend parallel to the illustrated, mutually orthogonal horizontal XX and vertical YY axes. The imaging lens assembly 20 preferably includes one or more variable focusing lenses.

[0021] As in Fig. 2, the array of pixels, in operation, detects light returned from a far target 42, which is located at a far working distance WD2 relative to the module 40, over a relatively narrow field of view (FOV) 44, and from a near target 46, which is located at a near working distance WD1 relative to the module 40, over a relatively wide FOV 48. In a preferred embodiment, WD1 is approximately one-half inch from the window 26 and WD2 is approximately 30 inches or more from the window 26. The imaging lens assembly 20 is located away from the window 26, for example, approximately 40 mm away. The returning light is scattered and / or reflected from each target across its respective FOV.The imaging lens assembly 20 receives the returning light passing through the window 26 along the imaging axis 18 and projects the received returning light onto the array of pixels. Each FOV (field of view) is generally rectangular and extends along the aforementioned mutually orthogonal horizontal and vertical axes, which are generally perpendicular to the imaging axis 18.

[0022] An illuminating light system may also be housed in module 40 and includes an illuminating light source, for example, a light-emitting diode (LED) 10, preferably mounted on PCB 22, and an illuminating lens assembly 12 configured to efficiently generate a pattern of illuminating light on and along each target to be read by an image capture device. At least a portion of the scattered and / or reflected returning light is derived from the pattern of illuminating light on and along each target. A distance measurement system may also be housed in module 40 and includes a rangefinder 16 for determining the working distance to each target to be read.The rangefinder 16 may, for example, transmit a laser or light beam or an ultrasonic signal to the target and measure the working distance by determining when a returning or echo signal is received.

[0023] How to continue in Fig. As shown in Figure 2, the imager 24, the rangefinder 16, and the illumination LED 10 are operatively connected to a controller or programmed microprocessor 36 operable to control the operation of these components. A memory 14 is connected to and accessible by the controller 36. In operation, the controller 36 sends command signals to turn on the rangefinder 16 to determine the working distance to the target, and also turn on the illumination LED 10 for a short exposure time period, e.g., 500 µs or less, and also turn on and expose or expose the imager 24 to collect the returning light, e.g., illumination light and / or ambient light, from the target only during the exposure time period. A typical array requires approximately 18-33 ms to capture the entire target image and operates at a frame rate of approximately 30-60 frames per second.The pixels generate electrical signals corresponding to a two-dimensional image of the target. The electrical signals are processed by the controller 36 into data indicating the target being read, and the data can be stored in the memory 14 or uploaded to a remote host for further processing. The controller 36 and the memory 14 can be mounted on the PCB 22, which is held by the module 40.

[0024] The resolution of the imager 24 can have various sizes. In a preferred embodiment, a resolution of four megapixels (MP) is used, with 2272 pixels wide along the horizontal axis by 1704 pixels high along the vertical axis, with each pixel occupying a square area of ​​approximately two microns. The pixels are thus arranged in a predetermined number of linear rows along the horizontal axis and in a predetermined number of linear columns along the vertical axis. A simplified version of the mutually orthogonal rows and columns of the imager array is shown in Fig. 3 and Fig. 4 shown.

[0025] As described above, the resolution at which the target image is captured varies over the working distance range. A distant target is best read by the imager at a high resolution, while a close target is better read at a low resolution. One aspect of this disclosure is to read the targets at a substantially constant resolution over the working distance range.

[0026] In this regard, controller 36 is operated to process the detected returning light from the distant target 42 only from a set of the pixels located in a central region 50 of the array, as diagrammatically represented by the shaded area in Fig. 3. The controller 36 is operated to ignore or discard the returning light captured by pixels located outside the central region 50. This set of pixels located in the central region 50 forms a number of rows less than the aforementioned predetermined number of rows and a number of columns less than the aforementioned predetermined number of columns. As a numerical example, if the central region 50 occupies one-quarter of the total area of ​​the array of the 4MP imager, the resolution of the captured image is 1MP.

[0027] The controller 36 is further operated to classify the detected returning light from the near target 46 by grouping all pixels into bins, as diagrammatically represented by the shaded areas 52 in Fig. 4. Each bin (also referred to as a pot) 52 includes a plurality of pixels. As shown, each bin 52 includes 4 individual, or native, pixels. Each bin 52 forms a single effective pixel that is larger than any individual pixel. The controller 36 processes the detected returning light from the near target 46 at a predetermined frame rate and processes the detected returning light from the far target 42 at a frame rate greater than the predetermined frame rate due to the fewer number of pixels in the central region 50 compared to the larger number of pixels in the entire array. The controller 36 processes the detected returning light from the near target 46 from each of the bins 52.As a numerical example, if each bin contains 52 2 × 2 or 4 native pixels, each bin is effectively four times larger than each native pixel, and the resolution is one-quarter of the total array area of ​​the 4MP imager, where in this case the resolution of the captured image is again 1MP. Thus, the resolution is essentially the same for both distant and near targets.

[0028] As shown in the flowchart of the Fig.5, the method for reading targets electro-optically is carried out by capturing an image at a substantially constant resolution over an extended range of working distances away from the array of pixels of the image sensor 24, beginning at start step 60 to determine whether the target is at a far distance, at decision step 62. If so, then the detected returning light from the far target 42 is processed only from the set of pixels located in the central region 50 of the array, at step 64, before terminating at end step 66. If not, then all of the pixels are copied into bins 52, each bin 52 having a plurality of the pixels, at step 68, and then the detected returning light from the near target 46 from each of the bins 52 is processed at step 70 before terminating at end step 66.

[0029] In the foregoing description, specific embodiments have been described. However, those of ordinary skill in the art will recognize that various modifications and changes may be made without departing from the scope of the invention as set forth in the following claims. Accordingly, the description and figures are to be considered in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present teachings.

[0030] The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or be more effectively realized are not considered critical, required, or essential features or elements of any or all of the claims. The invention is defined solely by the appended claims, including any amendments made during the pendency of this application, and all equivalent embodiments of the claims as granted.

[0031] Furthermore, in this document, interrelated terms such as first and second, top and bottom, and the like are 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," "contains," "containing," "includes," "including," or any other variation thereof are intended to connote non-exclusive incorporation, such that a process, method, article, or device that comprises, has, includes, or contains a list of elements not only includes those elements, but may include other elements not explicitly listed or inherent in such process, method, article, or device. An element preceded by "comprises... a," "has... a," "includes... a," "containing... a" does not, without further qualification, preclude the existence of additional identical elements in the process, method, article, or device 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 "substantial," "essential," "approximately," "nearly," or any other version thereof are defined to be understood as close to 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 this does not mean that it is necessarily direct and necessarily mechanical.A facility or structure that is "configured" in a particular way is configured in at least that way, but may also be configured in ways that are not listed.

[0032] It should be noted that some embodiments may include one or more generic or specialized processors (or "processing devices"), such as microprocessors, digital signal processors, custom-designed processors, and field programmable gate arrays (FPGAs), and further include unique stored program instructions (including both software and firmware) that control the one or more processors to, in conjunction with certain non-processor circuitry, implement some, most, or all of the functions of the method and / or apparatus described herein.Alternatively, some or all of the functions can be implemented by a state machine that has no stored program instructions, or in one or more application-specific integrated circuits (ASICs), where each function or any combination of specific functions is implemented as specially tailored logic. Of course, a combination of the two approaches can be used.

[0033] Furthermore, an embodiment may 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 media 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 EROM (erasable programmable read-only memory), an EPROM (electrically erasable programmable read-only memory), and a flash memory.Furthermore, it is expected that, despite potentially significant effort and numerous design choices guided by, for example, available time, current technology, and economic considerations, those of ordinary skill in the art, when guided by the concepts and principles disclosed herein, will readily be able to create such software instructions and programs and ICs with minimal experimentation.

[0034] The Summary of Disclosure is provided to enable the reader to quickly ascertain the nature of the technical disclosure. It is presented with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Additionally, it can be seen in the foregoing Detailed Description that various features in various embodiments are grouped together for the purpose of clarity of disclosure. This method of disclosure should not be interpreted as reflecting an intent that the claimed embodiments require more features than are explicitly recited in each claim. On the contrary, as the following claims set forth, inventive subject matter lies in fewer than all of the features of any single disclosed embodiment.Thus, the following claims are hereby incorporated into the detailed description, with each claim standing on its own as separately claimed subject matter.

Claims

[1] An imaging module (40) for reading targets (42, 46) electro-optically by capturing an image with a substantially constant resolution over an extended range of working distances away from the module (40), the module (40) comprising: an imaging system with an image sensor (24) having an array of pixels for detecting returning light from a first target (42) located at a first working distance relative to the module (40) over a relatively narrow field of view (44), and from a second target (46) located at a second working distance relative to the module (40) over a relatively wide field of view (48), the second working distance being closer to the module (40) than the first working distance; and a controller (36) operatively connected to the imaging system and operable to process the detected returning light from the first target (42) only from a set of the pixels located in a central region (50) of the array, and further operable to process the detected returning light from the second target (46) by grouping all of the pixels into bins (52), each bin (52) having a plurality of the pixels, and by processing the detected returning light from the second target (46) from each of the bins (52). [2] The imaging module (40) of claim 1, and including a distance measuring system for determining the working distance to each of the targets (42, 46) to be read. [3] The imaging module (40) of claim 1, wherein the pixels extend along mutually orthogonal horizontal and vertical axes for detecting the returning light from each of the targets (42, 46) along an imaging axis (18) generally perpendicular to the horizontal and vertical axes; and wherein the pixels are arranged in a predetermined number of linear rows generally parallel to the horizontal axis and in a predetermined number of linear columns generally parallel to the vertical axis. [4] The imaging module (40) of claim 1, wherein the imaging system comprises an imaging lens assembly (20) for receiving the returning light and for projecting the received returning light onto the image sensor (24) to initiate acquisition of an image of the target (42, 46), and wherein the imaging lens assembly (20) has a variable focus over the extended range of working distances. [5] The imaging module (40) of claim 3, wherein the set of pixels located in the central region (50) of the array forms a number of rows less than the predetermined number of rows and a number of columns less than the predetermined number of columns. [6] The imaging module (40) of claim 1, wherein each bin (52) forms a single effective pixel that is larger than any individual pixel. [7] The imaging module (40) of claim 1, wherein the controller (36) processes the detected returning light from the second target (46) at a predetermined frame rate, and processes the detected returning light from the first target (42) at a frame rate greater than the predetermined frame rate. [8] An image reader (30) for reading targets (42, 46) electro-optically by capturing an image with a substantially constant resolution over an extended range of working distances away from the reader (30), the reader (30) comprising: a housing (32) having a translucent window (26); and an imaging module (40) housed in the housing (32), the module (40) comprising: an imaging system with an image sensor (24) having an array of pixels for detecting returning light returning through the window (26) from a first target (42) located at a first working distance relative to the module (40) over a relatively narrow field of view (44), and from a second target (46) located at a second working distance relative to the module (40) over a relatively wide field of view (48), the second working distance being closer to the module (40) than the first working distance; and a controller (36) operatively connected to the imaging system and operable to process the detected returning light from the first target (42) only from a set of the pixels located in a central region (50) of the array, and further operable to process the detected returning light from the second target (46) by grouping all of the pixels into bins (52), each bin (52) having a plurality of the pixels, and by processing the detected returning light from the second target (46) from each of the bins (52). [9] An image reader (30) according to claim 8, and comprising a distance measuring system for determining the working distance to each of the targets (42, 46) to be read. [10] The image reader (30) of claim 8, wherein the pixels extend along mutually orthogonal horizontal and vertical axes for detecting the returning light from each of the targets (42, 46) along an imaging axis (18) generally perpendicular to the horizontal and vertical axes; and wherein the pixels are arranged in a predetermined number of linear rows generally parallel to the horizontal axis and in a predetermined number of linear columns generally parallel to the axis. [11] The image reader (30) of claim 8, wherein the imaging system comprises an imaging lens assembly (20) for receiving the returning light and for projecting the received returning light onto the image sensor (24) to initiate acquisition of an image of the target (42, 46), and wherein the imaging lens assembly (20) has a variable focus over the extended range of working distances. [12] The image reader (30) of claim 10, wherein the set of pixels located in the central region (50) of the array forms a number of rows less than the predetermined number of rows and a number of columns less than the predetermined number of columns. [13] The image reader (30) of claim 8, wherein each bin (52) forms a single effective pixel that is larger than any individual pixel. [14] The image reader (30) of claim 8, wherein the controller (36) processes the detected returning light from the second target (46) at a predetermined frame rate, and processes the detected returning light from the first target (42) at a frame rate greater than the predetermined frame rate. [15] A method for reading targets (42, 46) electro-optically by imaging with a substantially constant resolution over an extended range of working distances away from an array of pixels in an image sensor (24), the method comprising: detecting returning light returning from a first target (42) located at a first working distance relative to the array over a relatively narrow field of view (44), and from a second target (46) located at a second working distance relative to the array over a relatively wide field of view (48), the second working distance being closer to the module (40) than the first working distance; Processing the detected returning light from the first target (42) only from a set of pixels located in a central region (50) of the array; and Processing the detected returning light from the second target (46) by grouping all of the pixels into bins (52), each bin (52) comprising a plurality of the pixels, and by processing the detected returning light from the second target (46) from each of the bins (52). [16] The method of claim 15, and determining the working distance to each of the targets (42, 46) to be read. [17] The method of claim 15, and configuring the pixels to extend along mutually orthogonal horizontal and vertical axes for detecting the returning light from each of the targets (42, 46) along an imaging axis (18) generally perpendicular to the horizontal and vertical axes; and arranging the pixels in a predetermined number of linear rows generally parallel to the horizontal axis and in a predetermined number of linear columns generally parallel to the vertical axis. [18] The method of claim 15, and receiving the returning light and projecting the received returning light onto the array to initiate acquisition of an image of the target (42, 46), and changing a focus of the received returning light over the extended range of working distances. [19] The method of claim 17, configuring the set of pixels located in the central region (50) of the array with a number of rows less than the predetermined number of rows and with a number of columns less than the predetermined number of columns. [20] The method of claim 15, and configuring each bin (52) as a single effective pixel that is larger than each individual pixel.

Images