CN109154974B - Apparatus and method for determining target distance and adjusting read parameters of an imaging reader based on target distance - Google Patents

Abstract

The range to a target to be read by image capture within the range of working distances is determined by directing the aiming spot along the aiming axis to the target, and by capturing a first image of the target containing the aiming spot, and by capturing a second image of the target without the aiming spot. Each image is captured in a frame over a field of view having an imaging axis offset from an aiming axis. An image preprocessor compares first image data from the first image to second image data from the second image over a common fractional region of the two frames to obtain a location of the aiming spot in the first image, and determines a distance to the target based on the location of the aiming spot in the first image.

Description

Apparatus and method for determining target distance and adjusting imaging reader read parameters based on target distance

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of US Patent Application Serial No. 15/165,117, filed May 26, 2016, and US Patent Application Serial No. 15/170,464, filed June 1, 2016.

technical field

The present invention relates to an apparatus and method for determining a target distance and adjusting read parameters of an imaging reader based on the target distance.

Background technique

The present invention generally relates to an arrangement and method for determining a distance to a target to be read by image capture within a range of working distances, and/or rapidly adjusting based on target distances operable to be within a range of working distances One or more read parameters of an imaging reader that reads a target through image capture, particularly in an imaging reader having an aiming light assembly offset from the imaging assembly.

Solid-state imaging systems or imaging readers have been used in handheld and/or hands-free modes of operation to electro-optically read objects, such as one-dimensional and two-dimensional bar code symbol objects and/or non-symbolic objects such as documents. A handheld imaging reader includes a housing having a handle that is held by the operator, and an imaging module, also known as a scan engine, supported by the housing and aimed by the operator during reading. The imaging module includes an imaging assembly and an imaging lens assembly, the imaging assembly has a solid-state imager or imaging sensor with an imaging array of photocells or photosensors, the imaging array of photocells or photosensors corresponds to the imaging field of view of the imager An image element or pixel in the imaging lens assembly for capturing return light scattered and/or reflected from the object being imaged and for projecting the return light onto the array to initiate capture of an image of the object. Such imagers may include a one-dimensional or two-dimensional charge-coupled device (CCD) or complementary metal-oxide-semiconductor (CMOS) device and electrons for generating and processing electrons corresponding to a one-dimensional or two-dimensional pixel data array within the imaging field of view The associated circuit of the signal. To increase the amount of returned light captured by the array in, for example, dimly lit environments, the imaging module typically also includes a lighting assembly for illuminating the target, preferably with variable levels of illumination light reflected and scattered from the target. The aiming light assembly may also be supported by the imaging module for projecting a visible aiming light spot on the target.

In some applications, such as in warehouses, it is sometimes necessary for the same reader to read more than just distant targets (eg, on a product located on an overhead shelf that is located thirty feet away from the reader) to long-range working distances on the order of fifty feet) and need to read close-range targets (such as on products at ground level or close to the operator that are on the order of less than two feet from the reader) at close working distance). A near imager can be provided in the reader for imaging and focusing near targets within a relatively wide imaging field of view, and a far imager can also be provided in the same reader for imaging and focusing on Distant targets within a relatively narrow imaging field of view. Typically, at least one of the imagers (usually the tele imager) has a variable focal length, such as a movable lens assembly or zoom element.

While known imaging readers generally serve their intended purpose, rapid selection of the correct imager for the reader to read the target, rapid selection of the correct gain and/or exposure for the selected imager, and rapid Selecting the correct illumination level to illuminate a target that can be located anywhere within an extended working distance can be challenging. It is also challenging to focus the correct imager over the extended working distance range. Contrast-based autofocus, which is common in consumer cameras on smartphones, is notoriously slow because it relies on capturing and processing many images over many consecutive frames over a relatively long period of time to determine the best focus position. In many industrial applications where fast acting, active and dynamic readers are desired, this slow performance is unacceptable.

Accordingly, there is a need to rapidly adjust various read parameters of an imaging reader, such as selecting the correct imager, adjusting gain and/or exposure of at least one imager, adjusting illumination levels, and focusing at least one imager for use in Targets can be located anywhere within an extended working distance relative to the imaging reader without slowing or degrading reader performance.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is provided an apparatus for determining a distance to a target within a working distance to be read by image capture, the apparatus comprising: an activatable aiming assembly configured to be directing an aiming spot along an aiming axis to a target upon excitation; a controller configured to activate and de-energize the energizable aiming assembly; and an imaging assembly configured to activate and deactivate the activatable aiming assembly when the energizable aiming assembly is activated capturing a first image of the target including the aiming spot, and capturing a second image of the target without the aiming spot with the energizable aiming assembly de-energized, the first image and each of the second images is captured in a corresponding frame on a field of view having an imaging axis offset from the boresight axis; and an image preprocessor configured to each of the corresponding frames comparing the first image data from the first image with the second image data from the second image over the common fractional area of to obtain the position of the aiming spot in the first image, and based on The position of the aiming spot in the first image determines the distance to the target, wherein the image preprocessor subdivides the common fractional area into a plurality of subframes and compares each of the plurality of subframes. the first image data and the second image data in subframes to obtain the position of the aiming spot in at least one of the plurality of subframes, wherein the imaging component captures the first image and each of the second images as an array of pixels having luminance values, and wherein the image pre-processor is configured to evaluate the luminance values in each of the plurality of subframes averaging to obtain an average luminance value, and comparing the average luminance value of each of the plurality of subframes of the first image with the average luminance value of each of the plurality of subframes of the second image to obtain the position of the aiming spot based on the largest difference between the average luminance values in at least one of the plurality of subframes.

According to a second aspect of the present invention there is provided a method of determining a distance to a target within a working distance to be read by image capture, the method comprising the step of directing an aiming spot along an aiming axis to the a target; capturing a first image of the target including the aiming spot; then not directing the aiming spot at the target; capturing a second image of the target without the aiming spot, the first image and Each of the second images is captured in a corresponding frame on a field of view having an imaging axis offset from the boresight axis; on a common fractional area of each of the corresponding frames will be derived from the first image data of the first image is compared with second image data from the second image to obtain the position of the aiming spot in the first image; based on the aiming spot in the first image determining the distance to the target; and subdividing the common score area into a plurality of subframes, and comparing the first image data and the second image in each of the plurality of subframes data to obtain the position of the aiming spot in at least one subframe of the plurality of subframes, and capturing the first image and capturing the second image are performed by the following steps: capturing the first image and capturing the second image, respectively. each of the second images as an array of pixels having a luminance value, averaging the luminance values in each of the plurality of subframes to obtain an average luminance value, and comparing the first image The difference between the average luminance value of each subframe of the plurality of subframes and the average luminance value of each subframe of the plurality of subframes of the second image is based on the The position of the aiming spot is obtained by the maximum difference between the average luminance values in at least one subframe.

Description of drawings

The accompanying drawings, in which like reference numerals refer to identical or functionally similar elements throughout the individual views, are incorporated herein together with the following detailed description and form a part of this specification, and serve to further illustrate the invention, including the claimed invention embodiments of the concepts, and explain the various principles and advantages of those embodiments.

1 is a side view of a portable handheld imaging reader operable to determine a target distance for rapidly selecting the correct imager and/or imager gain and/or imaging in accordance with the present disclosure imager exposure and/or illumination levels, and/or quickly focus the correct imager.

2 is a schematic diagram of various components including an imaging, illumination and aiming light assembly supported on an imaging module mounted within the reader of FIG. 1 .

FIG. 3 is a perspective view of the imaging module of FIG. 2 in an isolated state.

FIG. 4 is a cross-sectional view taken on line 4-4 of FIG. 2 .

FIG. 5 is a view depicting aiming spots on a close range target for the reader of FIG. 1 .

FIG. 6 is a view depicting aiming spots on a long-range target for the reader of FIG. 1 .

FIG. 7 is a view of an image containing an aiming spot during roughly determining the position of the aiming spot in the image.

Figure 8 is a view of an image containing an aiming spot during fine determination of its location in the image.

9 is a flowchart depicting steps performed in a method of determining a target distance in accordance with the present disclosure.

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 size and position of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of embodiments of the present invention.

The arrangements and methodologies have been represented in the drawings by conventional symbols, where appropriate, the representations showing only those specific details relevant to an understanding of the embodiments of the invention so as not to educate those skilled in the art having the benefit of the description herein Obscure the disclosure with obvious details.

Detailed ways

One aspect of the present disclosure relates to a method for determining a distance to a target to be read by image capture within a range of a working distance and/or for adjusting at least one reading parameter of an imaging reader for use at a working distance The arrangement of the target is read through image capture within the range. The arrangement includes an activatable aiming assembly for directing an aiming spot along an aiming axis to a target when activated, and a controller for activating and deactivating the aiming assembly. The apparatus also includes an imaging assembly for capturing a first image of the target containing the aiming spot with the aiming assembly activated, and capturing a second image of the target without the aiming spot with the aiming assembly deactivated . Each image is captured in a frame on a field of view with an imaging axis offset from the boresight axis. The image preprocessor compares the first image data from the first image with the second image data from the second image over the common fractional area of the two frames to obtain the position of the aiming spot in the first image, and also The distance to the target is determined based on the position of the aiming spot in the first image. The controller is further operable to adjust at least one read parameter based on the determined target distance.

More specifically, during the rough determination of the target distance, the image preprocessor subdivides the common score area into multiple subframes, and compares the first image data and the second image data in each subframe to obtain the aiming spot in the subframe. at least one of the positions. Thereafter, during the fine determination of the target distance, the image preprocessor subdivides the area around the position of the aiming spot into a plurality of sub-areas, and compares the first image data and the second image data in each sub-area to obtain the aiming spot in the sub-areas location in at least one of the regions. Advantageously, the imaging assembly captures each image as an array of pixels with luminance values, and the image preprocessor averages the luminance values in each subframe and each subregion to obtain an average luminance value, and compares the first image with the difference between the average luminance values in each subframe and each subregion of the two images to obtain the position of the aiming spot based on the largest difference between the average luminance values in at least one of the subframes and subregions .

This arrangement is preferably incorporated in an imaging module (also referred to as a scan engine) mounted in an imaging reader (especially a hand-held reader), with means for imaging over a relatively wide imaging field of view A near imager for close targets, and a far imager for imaging distant targets over a relatively narrow imaging field of view. The above-mentioned imaging assembly preferably includes a tele imager with a variable focus, such as a movable lens assembly or a variable focus element. The reader also preferably has a variable level illumination light assembly for generating illumination light.

According to the present disclosure, the determined target distance may be used to adjust one or more reading parameters of the imaging reader. For example, the determined target distance may be used to automatically select which of the imagers to use to image the target, and/or automatically adjust the gain of the selected imager, and/or automatically adjust the exposure of the selected imager, And/or automatically adjust the illumination light level, and/or automatically adjust the focus of the selected imager. Contrary to known contrast-based autofocusing performed by capturing and processing many images over a long period of time, the focusing disclosed herein is more rapid because the target is performed in subframes of a pair of partial images and in subregions of subframes Determination of distance.

Yet another aspect of the present disclosure relates to determining a distance to a target to be read by image capture within a range of working distances and/or adjusting at least one reading parameter of an imaging reader for a range of working distances method to read the target through image capture. The method is performed by directing the aiming spot to the target along the aiming axis, and then not directing the aiming spot to the target. The method is further performed by capturing a first image of the target containing the aiming spot, capturing a second image of the target without the aiming spot, and capturing each image in a frame on a field of view having an imaging axis offset from the aiming axis . The position of the aiming spot in the first image is obtained by comparing the first image data from the first image with the second image data from the second image over a common fractional area of the two frames, and by comparing the aiming spot in the first image based on the aiming spot The position of the first image determines the distance to the target to perform the method still further. The method is performed yet further by adjusting at least one read parameter based on the determined target distance.

Reference numeral 30 in FIG. 1 generally identifies an ergonomic imaging reader configured as a pistol-shaped housing having an upper barrel or body 32 and exiting the body 32 at, for example, 15° from vertical The inclination angle of the lower handle 28 is tilted backwards. The light transmission window 26 is located adjacent the front or nose end of the body 32 and is preferably also inclined at an inclination angle of eg 15° with respect to vertical. The imaging reader 30 is held in the operator's hand and used in a hand-held mode in which the trigger 34 is manually depressed to initiate scanning of a target to be read over an extended range of working distances (particularly is a barcode symbol), the extended working distance range is, for example, on the order of about thirty feet to fifty feet from the window 26. Other configurations of housings and readers operating in a hands-free mode may also be employed.

As schematically shown in FIG. 2 and more realistically shown in FIGS. 3-4 , the imaging module 10 is mounted in the reader 30 behind the window 26 and is operable to pass through as described below. Window 26 reads the target by image capture within an extended working distance from module 10 . The target can be located anywhere in the working distance range between the close working distance (WD1) and the long working distance (WD2). In a preferred embodiment, WD1 is at or about eighteen inches from window 26 , and WD2 is much further from window 26 , eg, more than about sixty inches from window 26 . Module 10 includes an imaging assembly having a near imaging sensor or imager 12 and a near imaging lens assembly 16 and a far imaging sensor or imager 14 and a far imaging lens assembly 18 for use in a generally rectangular shape. A relatively wide imaging field of view 20 (eg, about thirty degrees) returns from close target capture in the close range region of the range (eg, the region from about zero inches to about eighteen inches from the window 26 ) and for projecting the captured return light onto the near imager 12, the far imaging lens assembly 18 for the generally rectangular, relatively narrow imaging field of view 22 (eg, about sixteen degrees) from within the range A distant object in a distant region of (eg, an area greater than about sixty inches from window 26 ) captures the return light and is used to project the captured return light onto distant imager 14 . Although only two imagers 12 , 14 and two imaging lens assemblies 16 , 18 have been illustrated in FIG. 2 , it will be appreciated that more than two imagers may be provided in module 10 .

Each imager 12, 14 is a solid-state device, such as 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 An array of CCD or CMOS imagers and the imagers 12 , 14 are operable to detect images captured by the respective imaging lens assemblies 16 , 18 through the window 26 along the respective near imaging axis 24 and far imaging axis 36 Return light. Each imaging lens assembly is advantageously a Cook triplet. As illustrated in FIG. 4, the near imaging lens assembly 16 has a fixed focal length, and the far imaging lens assembly 18 has a variable focal length due to the addition of a zoom element 38 or movable lens assembly.

2-4, the illumination light assembly is also supported by the imaging module 10 and includes an illumination light source (eg, at least one light emitting diode (LED) 40) fixedly mounted on the optical axis 42, and also with light Illumination lens assembly with illumination lens 44 centered on axis 42 . The illumination light assembly is shared by the two imagers 12, 14 and is operable to emit illumination light at variable illumination levels.

As further shown in FIGS. 2-3 , an aiming light assembly is also supported by imaging module 10 and includes an aiming light source 46 (eg, a laser) fixedly mounted on aiming shaft 48 , and an aiming lens centered on aiming shaft 48 50. Aiming lens 50 may include diffractive or refractive optical elements and is operable to project a pattern of visible aiming light onto a target along aiming axis 48 prior to reading. As shown in Figures 5-6, the aiming light pattern includes an aiming spot 102, preferably having a generally circular shape.

As further shown in Figure 2, the imagers 12, 14, LEDs 40 and lasers 46 are operatively connected to a controller or programmed microprocessor 52 operable to control the operation of these components. Memory 54 is connected to and accessible by controller 52 . Preferably, the controller 52 is the same as the means for processing the return light from the target and for decoding the captured image of the target. An image preprocessor 56 in a custom application specific integrated circuit (ASIC) or field programmable gate array (FPGA) is operably connected between the imagers 12 , 14 and the controller 52 for preprocessing by the imager 12 , 14 Captured images, as described more fully below. In some applications, image preprocessor 56 may be integrated with controller 52 .

As described above, for the reader 30, quickly select the correct imager 12 or 14 to read the target, quickly select the correct gain and/or exposure for the selected imager, and select the correct imager 40 from the LEDs It is challenging to illuminate a target that can be located anywhere within an extended working distance. It is also challenging to focus the chosen imager over the extended working distance range. Contrast-based autofocus, which relies on capturing and processing many images over many consecutive frames over a relatively long period of time to determine the best focus position, is notoriously slow. One aspect of the present disclosure involves determining the distance to the target by operating the aiming light assembly as both a lux meter and a rangefinder, and then selecting the correct imager 12 or 14, and/or selecting the correct imager 12 or 14 for the selected imager Correct gain and/or exposure, and/or selecting correct illumination from LED 40, and/or focusing the selected imager based on the determined distance, enhances reader performance.

As shown in FIG. 2, the aiming axis 48 is offset from the near imaging axis 24 and the far imaging axis 36 such that the resulting parallax between the aiming spot 102 on the aiming axis 48 and one of the near imaging axis 24 and the far imaging axis 36 provides target distance information. More specifically, the parallax between the aiming axis 48 and either of the near imaging axis 24 and the far imaging axis 36 provides range information from the pixel position of the aiming spot 102 on one of the imaging sensor arrays. It is preferable to use the imaging axis 36 of the far imager 14 by default because the parallax will be greater for the far imager 14 than for the near imager 12 . In the preferred embodiment, the distance between the aiming axis 48 and the far imaging axis 36 on the module 10 is about 23 millimeters.

As shown in FIG. 5 , the target of the symbol 100 configured to lie in the near region of the range is contained in the narrow field of view 22 of the far imager 14 , and preferably the imaging axis 36 is approximately centered in the narrow field of view 22 . As shown in FIG. 6 , the same symbols 100 configured to be located in the far region of the range are also contained in the narrow field of view 22 of the far imager 14 , and preferably, the imaging axis 36 is again approximately centered in the narrow field of view 22 . The apparent size of the symbol 100 is larger in FIG. 5 than in FIG. 6 . In the narrow imaging field of view 22, the symbol 100 is off-center in FIG. 5 and more centered in FIG. 6 . For the default far imager 14, if the symbol 100 is located at an infinite working distance from the reader 30, the aiming spot 102 on the pointing symbol 100 will overlay directly on the imaging axis 36. As the symbol 100 gets closer to the reader 30 , the aiming spot 102 becomes larger in area, as shown in FIG. 5 , and moves along the inclined trajectory 104 away from the imaging axis 36 . By determining the position of the aiming spot 102 on the trajectory 104 relative to the imaging axis 36, the working distance of the symbol 100 can be determined. The separation between the aiming spot 102 and the imaging axis 36 is proportional to the inverse of the working distance. Preferably, the position of the aiming spot 102 along the trajectory 104 is pre-calibrated during reader manufacture. As also shown in Figures 5-6, the far imager 14 captures an image of the symbol 100 at a particular resolution, in the illustrated case at a two-dimensional resolution of 800 rows of pixels high and 1280 columns of pixels wide.

The image preprocessor 56 mentioned above is used to analyze the images captured by the far imager 14 in order to determine the location of the aiming spot 102 . To minimize cost, the image preprocessor 56 is preferably incorporated in a low power, low processing device, preferably without a frame buffer to store images. As a result, as explained below, the image preprocessor 56 is not responsible for analyzing each overall captured image, but only a fractional area of each captured image, particularly where the aiming spot 102 is expected to appear along the trajectory 104 Score area.

More specifically, controller 52 energizes aiming laser 46 to direct aiming spot 102 onto symbol 100 . The far imager 14 captures in a first frame an image of the first, whole or preferably part of the symbol 100 with the aiming spot 102 thereon. In response, image preprocessor 56 analyzes only fractional regions of the first image in the first frame. As shown in FIG. 7, image preprocessor 56 does not analyze pixels in rows 0 to about 400, or pixels in about rows 560 to 800, or columns 0 to about 640 pixels, since the aiming blob 102 is not expected to be there, and there is no reason to waste processing power or time analyzing pixels where the aiming blob 102 would not be present. The fractional or residual area contains only about 160 lines out of the original 800 lines of the complete first image, and thus can be captured and analyzed much faster than the complete first image.

Image preprocessor 56 subdivides the remaining regions of the first frame into a matrix of subframes or coarse regions. As shown in Figure 7, the remaining area is subdivided into sixteen generally rectangular subframes, eg, four rows by four columns. The subframes do not need to have the same height, width or area. It will be appreciated that the remaining region may be subdivided into any number of subframes. The number of subframes depends on the accuracy desired to initially roughly locate the aiming spot 102 in the subframes.

Image preprocessor 56 next obtains image data from each of the subframes. More specifically, the hue or luminance values of all pixels in each subframe are averaged to obtain an average luminance value. Image preprocessor 56 obtains a matrix of sixteen average luminance values, one for each subframe.

Immediately, the controller 52 de-energizes the aiming laser 46 and the far imager 14 captures in a second frame a second, whole or preferably part of the image of the symbol 100 on which the aiming spot 102 is not present. As before, the image preprocessor 56 analyzes only the fractional region of the second image in the second frame, and the fractional region is the same fractional region used in the first image. As before, the image preprocessor 56 obtains the luminance values of all pixels in each subframe of the same fractional area, averages the luminance values in each subframe of the same fractional area to obtain the average luminance value, and obtains sixteen averages A matrix of luminance values, with one average luminance value for each subframe.

As a non-limiting numerical example, the matrix of sixteen average luminance values with the aiming assembly de-energized is shown on the left below, and the matrix of the sixteen average luminance values with the aiming assembly activated is as follows The right side of the face shows:

Image preprocessor 56 then compares the two matrices by subtracting the average luminance values for each subframe, obtaining in this numerical example the following difference matrix of luminance difference values:

It will be observed from the difference matrix that the luminance difference value in row 1, column 1 stands out from all other luminance difference values because it has the largest magnitude or luminance difference. This identifies the location of the aiming spot 102 .

If more precise determination of the location of the aiming spot 102 is desired, the image preprocessor 56 may subdivide the area around the identified location of the aiming spot 102 into a plurality of sub-areas. As shown in FIG. 8, image preprocessor 56 subdivides the region into a matrix of subregions or fine regions, eg, into sixteen (eg, four rows by four columns) generally rectangular subregions. Subregions do not need to have the same height, width, or area. It will be appreciated that this area can be subdivided into any number of sub-areas. The number of sub-regions depends on the accuracy desired for subsequently finely positioning the aiming spot 102 in the sub-regions.

As before, the controller 52 energizes and de-energizes the aiming laser 46, and the processor 56 obtains a matrix of sixteen average luminance values (one average luminance value for each subregion with the aiming laser 46 energized), And another matrix of sixteen mean brightnesses (one mean brightness value for each subregion with the aiming laser 46 de-energized). The image preprocessor 56 then compares the two matrices by subtracting the average luminance values for each sub-region, and finely locates the aiming spot 102 by finding the largest luminance difference value in at least one of the sub-regions.

Returning to Figure 7, it will be observed that it is not necessary to analyze all sixteen subframes, since the aiming spot 102 will only appear in the shaded subframes exhibited along the trajectory 104. This reduces the possibility of errors caused by moving objects or flash light sources that may only appear in the image with the aiming laser 46 energized and be mistaken for the aiming spot 102 . The same principle of ignoring subframes can be applied to the top and bottom rows of the subregions shown in FIG. 8 .

In operation, once the working distance to the symbol 100 is determined from the aiming spot location, the controller 52 either selects the near imager 12, and when the rangefinder determines that the symbol 100 to be imaged and read by the near imager 12 is located at the end of the range At close range, the illumination light assembly is actuated to illuminate the symbol 100 with a relatively small intensity of illumination light; alternatively the far imager 14 is selected, and when the rangefinder determines that the symbol 100 to be imaged and read by the far imager 14 is in range , the illumination light assembly is actuated to illuminate the target with a relatively large intensity of illumination light.

Additionally, once the working distance to the symbol 100 is determined from the aiming spot position, the controller 52 may also adjust the focal length of the far imager 14, such as by changing the focal length of the focusing element 38. Controller 52 energizes LED 40 with a variable current to vary the intensity of the illumination light. Still further, controller 52 may also adjust the gain and/or exposure of one or more imagers once the working distance to the symbol 100 is determined from the aiming spot location and/or once the luminance value from each subframe is determined.

As shown in the flowchart of FIG. 9 , the method is performed by actuating the aiming light assembly in step 200 to direct the aiming spot 102 to the symbol 100 along the aiming axis; capturing the symbol containing the aiming spot 102 in step 202 100; and obtaining first image data from the first fractional image in step 204. Next, the aiming light assembly is deactivated in step 206 , a second fractional image of the symbol 100 without the aiming spot 102 is captured in step 208 , and second image data from the second fractional image is obtained in step 210 . The first image data and the second image data are compared in step 212 to obtain the position of the aiming spot 102 , and in step 214 the distance to the symbol 100 is determined based on the position of the aiming spot 102 . In step 216, based on the determined distance, the correct imager 12 or 14 is selected, and/or the correct gain and/or exposure for the selected imager is adjusted, and/or the correct illumination from the LED 40 is adjusted, and/or adjust the focus of the selected imager.

Specific embodiments have been described in the foregoing specification. 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 drawings 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 the present teachings.

These benefits, advantages, solutions to problems, and any element(s) that may make any benefit, advantage, or solution occur or become more pronounced are not to be construed as critical, required, or essential to any or all of the claims feature or element. 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 after publication.

Furthermore, in this document, relational terms such as first and second, top and bottom, etc. may be used solely to distinguish one entity or action from another without necessarily requiring or implying these entities or any actual such relationship or sequence between actions. The terms "consists of," "consists of," "has," "has," "includes," "includes," "comprises," "contains," or any other variations thereof are intended to cover non-exclusive inclusion such that constituting A process, method, article, or apparatus that has, includes, or includes a list of elements includes not only those elements, but may also include other elements not expressly listed or inherent to such a process, method, article, or apparatus. Elements beginning with "constitutes a", "has a", "includes a" or "includes a", without further constraints, are not excluded from the process, method of forming, having, including or including the element , the article or device has another identical element present. The terms "a" and "an" are defined as one or more, unless expressly stated otherwise herein. The terms "substantially," "essentially," "approximately," "approximately," or any other version of these terms are defined as close to what one of ordinary skill in the art would understand, and in one non-limiting example, the The term is defined as within 10%, in another embodiment as within 5%, in another embodiment as within 1%, and in another embodiment as within 0.5%. The term "coupled" as used herein is defined as connected, although not necessarily directly or 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.

It will be appreciated that some embodiments may include one or more general-purpose or special-purpose processors (or "processing devices") such as microprocessors, digital signal processors, custom processors, and field programmable gate arrays (FPGAs). and uniquely stored program instructions (including both software and firmware) that control one or more processors to implement, in conjunction with certain non-processor circuits, some of the methods and/or apparatus described herein, Most or all functions. Alternatively, some or all of the functions may be implemented by a state machine without stored program instructions, or in one or more application specific integrated circuits (ASICs), where various functions or some combination of certain functions are implemented as custom logic. Of course, a combination of these two methods can also be used.

Furthermore, one embodiment may be implemented as a computer-readable storage medium having computer-readable code stored thereon for programming a computer (eg, including a processor) to perform as described herein and the claimed method. Examples of such computer-readable storage media include, but are not limited to, hard disks, CD-ROMs, optical storage devices, magnetic storage devices, ROM (read only memory), PROM (programmable read only memory), EPROM (erasable programmable memory) read-only memory), EEPROM (electrically erasable programmable read-only memory), and flash memory. Furthermore, it is contemplated that those of ordinary skill in the art, despite the possible significant effort and many design choices motivated by, for example, time available, current technical and economic considerations, when guided by the concepts and principles disclosed herein, will Such software instructions and programs and integrated circuits (ICs) can readily be generated with minimal experimentation.

The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. This Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Furthermore, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of unifying the disclosure. This method of disclosure should not be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in the various claims. 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.

Claims (14)

1. An apparatus for determining a distance to a target to be read by image capture within a range of working distances, the apparatus comprising:

an energizable aiming assembly configured to direct an aiming spot along an aiming axis to a target when energized;

a controller configured to activate and deactivate the activatable targeting component;

an imaging assembly configured to

Capturing a first image of the target containing the aiming spot with the energizable aiming assembly energized, and

capturing a second image of the target without the aiming spot with the activatable aiming assembly deactivated, each of the first and second images being captured in a respective frame over a field of view having an imaging axis offset from the aiming axis; and

an image preprocessor configured to

Comparing first image data from the first image with second image data from the second image over a common fractional region of each of the respective frames to obtain a location of the aiming spot in the first image, an

Determining a distance to the target based on a location of the aiming spot in the first image, wherein the image preprocessor subdivides the common fractional region into a plurality of sub-frames and compares the first image data and the second image data in each of the plurality of sub-frames to obtain a location of the aiming spot in at least one of the plurality of sub-frames,

wherein the imaging component captures each of the first and second images as an array of pixels having intensity values, and wherein the image pre-processor is configured to

Averaging the luminance values in each of the plurality of sub-frames to obtain an average luminance value, an

Comparing the difference between the average brightness value of each of a plurality of sub-frames of the first image and the average brightness value of each of a plurality of sub-frames of the second image to obtain the location of the aiming spot based on the greatest difference between the average brightness values in at least one of the plurality of sub-frames.

2. The apparatus of claim 1, wherein the image preprocessor subdivides a region around the location of the aiming spot into a plurality of sub-regions and compares the first image data and the second image data in each of the plurality of sub-frames to obtain the location of the aiming spot in at least one of the plurality of sub-regions.

3. The apparatus of claim 1, wherein the energizable targeting assembly, the imaging assembly, and the image pre-processor are incorporated in an imaging module having a first imager configured to image a first target over a first imaging field of view; and a second imager configured to image a second target over a second imaging field of view, the first target being located closer than the second target, the first imaging field of view being wider than the second imaging field of view, and wherein the imaging assembly is the second imager with variable focal length.

4. The apparatus of claim 3, wherein the controller adjusts a focal length of the second imager based on the determined target distance.

5. The apparatus of claim 3, wherein the controller selects one of the first imager and the second imager and adjusts at least one of a gain and an exposure for the selected imager based on the determined target distance.

6. The apparatus of claim 3, further comprising an illumination light assembly mounted on the module, the illumination light assembly configured to generate a variable level of illumination light, wherein the controller adjusts the level of the illumination light based on the determined target distance.

7. The apparatus of claim 1, further operable to adjust at least one reading parameter of an imaging reader for reading a target, wherein the controller is further configured to adjust the at least one reading parameter of the imaging reader based on the determined target distance.

8. A method of determining a distance to a target to be read by image capture within a range of working distances, the method comprising the steps of:

directing an aiming spot along an aiming axis to the target;

capturing a first image of the target including the aiming spot;

subsequently not directing the aiming spot at the target;

capturing a second image of the target without the aiming spot, each of the first and second images being captured in a respective frame over a field of view having an imaging axis offset from the aiming axis;

comparing first image data from the first image to second image data from the second image over a common fractional region of each of the respective frames to obtain a location of the aiming spot in the first image;

determining a range to the target based on a position of the aiming spot in the first image; and

subdividing the common fractional region into a plurality of sub-frames, and comparing the first image data and the second image data in each of the plurality of sub-frames to obtain a location of the aiming light spot in at least one of the plurality of sub-frames,

capturing the first image and capturing the second image are performed by: capturing each of the first and second images as an array of pixels having luminance values, averaging the luminance values in each of the plurality of sub-frames to obtain an average luminance value, and comparing a difference between the average luminance value of each of the plurality of sub-frames of the first image and the average luminance value of each of the plurality of sub-frames of the second image to obtain the location of the aiming spot based on a maximum difference between the average luminance values in at least one of the plurality of sub-frames.

9. The method of claim 8, further comprising subdividing an area around the location of the aiming spot into a plurality of sub-areas, and comparing the first image data and the second image data in each of the plurality of sub-frames to obtain the location of the aiming spot in at least one of the plurality of sub-areas.

10. The method of claim 8, wherein at least one of capturing the first image and capturing the second image is performed by one of a first imager configured to image a first target over a first imaging field of view and a second imager configured to image a second target over a second imaging field of view, the first target being located closer than the second target, the first imaging field of view being wider than the second imaging field of view, wherein the first imager and the second imager have variable focal lengths.

11. The method of claim 10, further comprising adjusting a focal length of the second imager based on the determined target distance.

12. The method of claim 10, further comprising selecting one of the first imager and the second imager and adjusting at least one of a gain and an exposure for the selected imager based on the determined target distance.

13. The method of claim 10, further comprising illuminating the target with a variable level of illumination light, and adjusting the level of illumination light based on the determined target distance.

14. The method of claim 8, further operable for adjusting at least one reading parameter of an imaging reader for reading a target, the method further comprising adjusting the at least one reading parameter of the imaging reader based on the determined target distance.

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