DE112017002649T5 - ARRANGEMENT AND METHOD FOR DETERMINING A TARGET DISTANCE AND ADAPTING READING PARAMETERS OF AN IMAGING READER BASED ON A TARGET DISTANCE - Google Patents

Abstract

A distance to a target to be read by image acquisition over a range of working distances is determined by pointing a target spot along a target axis at the target and detecting a first image of the target containing the target 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 that has an image axis offset from the target axis. An image pre-processor compares first image data from the first image with second image data from the second image over a common portion of both frames to obtain a position of the target light spot in the first image, and determines the distance to the target based on the position of the target light spot in the first image first picture.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Application filed May 26, 2016. Patent Application Serial No. 15 / 165,117 and U.S. Patent Application filed Jun. 1, 2016. Patent Application Serial No. 15 / 170,464.

BACKGROUND OF THE INVENTION

The present invention generally relates to an arrangement and method for determining a distance to a target to be read by image acquisition over a range of working distances, and / or for rapidly adjusting one or more reading parameters of an imaging reader used for reading Targeting is performed by image acquisition over a range of working distances based on a target distance, in particular in an imaging reader with a targeting light assembly which is offset from an imaging assembly.

Solid state imaging systems or imaging readers have been used for both handheld and handsfree modes for electro-optically reading targets, such as one and two dimensional bar code symbol targets and / or non-symbol targets, such as documents. A portable imaging reader includes a housing with a handle that is held by an operator and an imaging module, also known as a scanning machine, that is carried by the housing and is aligned by the operator to a target when reading. The imaging module includes an imaging assembly including a solid state imager or image sensor having an imaging array of photocells or light sensors corresponding to pixels in an imaging field of view of the imager, and an imaging lens assembly for detecting return light scattered from the target to be imaged and / or is reflected and for projecting the returning light onto the array to cause the taking of an image of the target. Such an imager may comprise a one or two dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device and associated circuitry for generating and processing electronic signals coupled to a one or two dimensional array of pixel data over the Imaging field of view correspond. To increase the amount of return light detected by the device, e.g. In low-light environments, the imaging module generally also includes an illumination light assembly for illuminating the target, preferably with a variable level of illumination light for reflection and scattering from the target. A aiming light assembly may also be carried by the imaging module to project a visible aiming spot onto the target.

In some applications, e.g. In warehouses, it is sometimes necessary for the same reader to not only read distant destinations, e.g. On products located on high shelves located at a far distance of working distances of the order of 30 to 50 feet from the reader, but also nearby targets, e.g. On products located at ground level or in the vicinity of the operator, which are located in a near range of working distances of the order of less than two feet from the reader. A close-up imager may be provided in the reader for imaging and focusing on near targets over a relatively wider field of view, and a remote imager may also be provided in the same reader for imaging and focusing on distant targets through a relatively narrower field of view. Typically, at least one of the imagers, typically the remote imager, has a variable focus, such as a moveable lens assembly or a variable focus element.

Although the known imaging reader is generally satisfactory for its intended purpose, it may be challenging for the reader to quickly select the correct imager to read a target, quickly select the proper gain and / or exposure for the selected imager, and quickly illuminate a proper illumination level of the target, which can be anywhere in the extended range of the working distance. It can also be challenging to focus the right imager over the extended range of the working distance. Contrast-based automatic focusing, as is common in consumer cameras on smartphones, is known to be slow because it relies on taking and processing many images over many relatively long frames over many relatively long frames to determine the best focus position. Such sluggish performance is unacceptable in many industrial applications where a fast-acting, aggressive, and dynamic reader is desired.

Accordingly, there is a need to rapidly adjust various reading parameters of an imaging reader, such as selecting the correct imager, adjusting the gain and / or exposure of at least one imager, adjusting the illumination level, and focusing the at least one imager to read a target which can be anywhere within an extended range of a working distance relative to an imaging reader without slowing or compromising the performance of the reader.

list of figures

• 1 ist eine erhöhte Seitenansichtsansicht eines tragbaren, handgehaltenen Bildgebungslesegerätes zum Bestimmen eines Zielabstandes zur Verwendung zum schnellen Auswählen des richtigen Bildgebers und/oder Bildgeberverstärkung und/oder Bildgeberbelichtung und/oder Beleuchtungsniveau und/oder zum schnellen Fokussieren des richtigen Bildgebers gemäß dieser Offenbarung.
• 2 ist ein schematisches Diagramm verschiedener Komponenten, einschließlich bildgebender, beleuchtender und Ziellichtbaugruppen, die auf einem Bildgebungsmodul getragen werden, das im Inneren des Lesegerätes von 1 montiert ist.
• 3 ist eine perspektivische Ansicht des Bildgebungsmoduls von 2 in isolierter Form.
• 4 ist eine Schnittansicht, die auf Linie 4--4 von 2 aufgenommen wurde.
• 5 ist eine Ansicht, die einen Zielfleck auf einem Nahziel für das Lesegerät von 1 darstellt.
• 6 ist eine Ansicht, die einen Zielfleck auf einem Fernziel für das Lesegerät von 1 darstellt.
• 7 ist eine Ansicht eines Bildes, das den Zielfleck enthält, während einer groben Bestimmung der Position des Zielflecks in dem Bild.
• 8 ist eine Ansicht eines Bildes, das den Zielfleck enthält, während einer Feinbestimmung der Position des Zielflecks in dem Bild.
• 9 ist ein Flussdiagramm, das Schritte darstellt, die in einem Verfahren zum Bestimmen des Zielabstandes gemäß dieser Offenbarung durchgeführt werden.

The accompanying drawings, wherein like reference numerals designate identical or functionally similar elements in the several views, are incorporated in the disclosure together with the following detailed description, and form a part of the disclosure, and serve to further illustrate embodiments of the concepts described herein and various To explain principles and advantages of these embodiments.

• 1 FIG. 11 is an elevated side view of a portable hand-held imaging reader for determining a target distance for use in rapidly selecting the correct imager and / or imager gain and / or imager exposure and / or illumination level and / or quickly focusing the correct imager according to this disclosure.
• 2 FIG. 12 is a schematic diagram of various components, including imaging, illuminating and aiming light assemblies, carried on an imaging module mounted inside the reader of FIG 1 is mounted.
• 3 is a perspective view of the imaging module of 2 in isolated form.
• 4 is a sectional view taken on line 4--4 of 2 has been recorded.
• 5 is a view that has a target spot on a near target for the reader of 1 represents.
• 6 is a view that has a target spot on a remote target for the reader of 1 represents.
• 7 Figure 13 is a view of an image containing the target spot during a rough determination of the position of the target spot in the image.
• 8th Figure 11 is a view of an image containing the target spot during fine determination of the position of the target spot in the image.
• 9 FIG. 10 is a flowchart illustrating steps performed in a method for determining the target distance according to this disclosure. FIG.

Skilled artisans will recognize that elements in the figures are illustrated for simplicity and clarity and are not necessarily drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to enhance the understanding of embodiments of the present invention.

The arrangement and method steps have been illustrated, where appropriate, by conventional symbols in the drawings, which show only those specific details that are relevant to understanding the embodiments of the present invention so as not to obscure the disclosure with details specific to the Those skilled in the art having recourse to the present description will readily appreciate.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present disclosure relates to an arrangement for determining a distance to a target to be read by image acquisition over a range of working distances, and / or for adjusting at least one reading parameter of an imaging reader for reading targets through image capture over an area of working distances. The arrangement includes an activatable target assembly for directing a target spot along a target axis at the target when activated and a controller for activating and deactivating the target assembly. The arrangement also includes an imaging assembly for capturing a first image of the target containing the target spot when the target assembly is activated and capturing a second image of the target without the target spot with the target assembly deactivated. Each image is captured in a frame over a field of view that has an image axis offset from the target axis. An image preprocessor compares first image data from the first image with second image data from the second image over a common portion of both frames by one position of the target spot in the first image, and also determines the distance to the target based on the position of the target spot in the first image. The controller is further capable of adjusting the at least one read parameter based on the determined target distance.

Specifically, during a rough determination of the target distance, the image preprocessor divides the common subarea into a plurality of subframes and compares the first and second image data in each subframe to obtain the position of the target light spot in at least one of the subframes. Thereafter, during a fine determination of the target distance, the image preprocessor divides an area around the position of the target spot into a plurality of partial areas, and compares the first and second image data in each partial area to obtain the position of the target spot in at least one of the partial areas. Advantageously, the imaging assembly captures each image as an array of pixels having brightness values, and the image preprocessor averages the brightness values in each subframe and subregion to obtain an average brightness value, and compares differences between the average brightness values in each subframe and each subregion of the first and second image to obtain the position of the target spot based on the largest difference between the average brightness values in at least one of the subframes and subregions.

The assembly is preferably incorporated into an imaging module, also referred to as a scanning machine, mounted in the imaging reader, particularly in a hand-held reader having a close-up imager for imaging near targets over a relatively wider field of view and a remote imager for imaging long-range targets over a relatively narrower field of view , The aforementioned imaging assembly preferably includes the remote imager having a variable focus, such as a movable lens assembly or a variable focus element. The reader also preferably includes an illumination light assembly for generating a variable illumination light level.

According to this disclosure, the determined target distance may be used to set one or more read parameters of the image reader. For example, the determined target distance may be used to automatically select which of the images to use to image the target, and / or to automatically adjust the gain of the selected image, and / or automatically adjust the exposure of the selected image, and / or to automatically adjust the level of illumination light and / or automatically adjust the focus of the selected image. In contrast to known contrast-based automatic focusing by capturing and processing many images over an extended period of time, the focus disclosed herein is faster because the determination of the target distance is done in subframes of a pair of subframes and in subregions of the subframes.

Yet another aspect of the present disclosure relates to a method of determining a distance to a target to be read by image acquisition over a range of working distances, and / or adjusting at least one reading parameter of an image reading device to read targets by image acquisition via a Range of working distances. The method is performed by pointing a target spot along a target axis at the target and then not pointing the target spot to the target. The method is further performed by capturing a first image of the target containing the target spot, capturing a second image of the target without the target spot, and capturing each image in a frame over a field of view having an image axis offset from the target axis. The method is further performed by comparing first image data from the first image with second image data from the second image over a common portion of both frames to obtain a position of the target light spot in the first image, and the distance to the target based on the Position of the target spot in the first image is determined. The method is further performed by adjusting the at least one read parameter based on the determined target distance.

The reference number 30 in 1 generally identifies an ergonomic image reader that acts as a gun-shaped housing with an upper barrel or body 32 and a lower handle 28 configured at an angle of inclination, for example fifteen degrees, to the vertical rearward of the body 32 is inclined away. A translucent window 26 is located adjacent to the front or front of the body 32 and is preferably also at a tilt angle, z. Fifteen degrees, inclined to the vertical. The imaging reader 30 is held in the hands of an operator and used in a hand-held mode in which a trigger 34 is manually pressed to the mapping of targets, in particular bar code symbols, to be read in an extended range of working distances, for example of the order of thirty to fifty feet away from the window 26 . initiate. Chassis of other configurations as well as readers operated in handsfree mode can also be used.

As schematically in the 2 presented, and how realistic in the 3 - 4 is an imaging module 10 in the reader 30 behind the window 26 mounted and is, as described below, for reading targets by image capture through the window 26 over an extended range of working distances away from the module 10 executed. A target can be anywhere in a workspace of distances between a close working distance ( WD1 ) and a remote working distance ( WD2 ) are located. In a preferred embodiment WD1 either at or about 18 inches away from the window 26 , and WD2 is much further away, for example, about 60 inches away from the window 26 , The module 10 includes an imaging assembly that includes a near-vision imaging sensor or close-up imager 12 and a close-up imaging lens assembly 16 for detecting return light over a generally rectangular, relatively wide field of view field 20 , z. About thirty degrees, from a near target that is in a near zone of the area, e.g. From about zero inches to about eighteen inches from the window 26 and project the detected returning light to the close-up imager 12 , as well as a remote imaging sensor or remote image generator 14 , and a remote imaging lens assembly 18 for detecting return light across a generally rectangular, relatively narrow field of view field 22 , z. About sixteen degrees, from a faraway target located in a far-away area of the area, e.g. Greater than about sixty inches from the window 26 and project the detected returning light onto the remote imager 14 , Although only two imagers 12 . 14 and two imaging lens assemblies 16 . 18 in 2 be understood that more than two in the module 10 can be provided.

Every imager 12 . 14 is a solid-state device, for example a CCD or CMOS imager, having a one-dimensional array of addressable image sensors or pixels arranged in a single linear array, or preferably a two-dimensional array of such sensors are arranged in mutually orthogonal rows and columns, and for detecting return light coming from the respective imaging lens assemblies 16 . 18 along corresponding close and distant image axes 24 . 36 through the window 26 is detected is executed. Each imaging lens assembly is advantageously a Cooke triplet. As in 4 shown has the close-up imaging lens assembly 16 a fixed focus, and the far-imaging lens assembly 18 has a variable focus, since in addition a variable focusing element 38 or a movable lens assembly is provided.

As well as in the 2 - 4 As shown, an illumination light assembly also becomes the imaging module 10 worn and has an illumination light source, z. B. at least one light emitting diode (LED) 40 stationary on an optical axis 42 mounted, and a lighting lens assembly, which is also on the optical axis 42 centered illumination lens 44 includes. The illumination light assembly is used by both imagers 12 . 14 is shared and designed to emit illumination light with a variable illuminance.

As further in the 2 - 3 Also shown is a targeting light assembly from the imaging module 10 worn and has a target light source 46 on, z. As a laser stationary on a target axis 48 is mounted, and a target lens 50 that are on the target axis 48 is centered. The target lens 50 may comprise a diffractive or a refractive optical element and is for projecting a visible aiming light pattern along the aiming axis 48 executed on the target before reading. The aiming pattern includes, as in FIGS 5 - 6 represented, a target light spot 102 , preferably of generally circular shape.

As in further 2 shown are the imagers 12 . 14 , the LED 40 and the reader 46 functional with a controller or a programmed microprocessor 52 which is designed to control the operation of these components. A store 54 is to the controller 52 connected and accessible to them. Preferably, the controller 52 the same as that used to process the returning light from the targets and to decode the captured target images. An image preprocessor 56 in a custom application integrated circuit (ASIC) or field programmable gate array (FPGA) is functional between the imagers 12 . 14 and the controller 52 connected to those of the imagers 12 . 14 preprocessing captured images, as described in more detail below. The image preprocessor 56 can in some applications in the controller 52 be integrated.

As described above, it may be for the reader 30 be challenging, quickly find the right imager 12 or 14 to select a target, to quickly select the correct gain and / or exposure for the selected imager, and a proper illumination level from the LED 40 to illuminate the target, which can be anywhere in the extended working distance range. It may also be challenging to focus the selected imager over the extended working distance range. Contrast-based automatic focusing, which is based on capturing and processing many images over many consecutive frames over a relatively long period of time to determine the best focus position, is known to be slow. One aspect of this disclosure aims to improve the performance of the reader by operating the aiming light assembly as both a light meter and a rangefinder to determine a distance to the target and then the correct imagers 12 or 14 to select and / or select the correct gain and / or exposure for the selected imager, and / or the proper illumination from the LED 40 to focus and / or focus the selected imager based on the particular distance.

As in 2 represented, is the target axis 48 opposite the near and distant picture axes 24 . 36 offset so that the resulting parallax between the target spot 102 on the target axis 48 and one of the near and distant image axes 24 . 36 provides a target distance information. In particular, the parallax represents between the target axis 48 and each of the near and distant image axes 24 . 36 a distance information from the pixel position of the target spot 102 on one of the imaging sensor arrays. It is preferred, by default, the image axis 36 of the remote image generator 14 to use because the parallax error for the remote image generator 14 is larger than for the close-up imager 12 , In a preferred embodiment, the distance between the target axis 48 and the telephoto axis 36 on the module 10 about 23 millimeters.

As in 5 is shown as an icon 100 executed target, which is located in a close range of the area, in the narrow field of view 22 of the remote image generator 14 and preferably the image axis 36 in the narrow field of view 22 centered. As in 6 represented, is the same symbol 100 located in a far-away area of the area, even in the narrow field of view 22 of the remote image generator 14 and preferably the image axis 36 again almost in the narrow field of view 22 centered. The apparent size of the symbol 100 is in 5 bigger than in 6 , The symbol 100 is in 5 eccentric and in 6 more centered in the narrow field of view 22 , If, for the standard remote image generator 14 , the symbol 100 at an infinite working distance from the reader 30 would be located on the icon 100 directed target spot 102 directly on the image axis 36 rest. With increasing approach of the symbol 100 to the reader 30 becomes the target spot 102 , as in 5 shown, getting bigger and bigger and moving from the image axis 36 along an inclined trajectory 104 away. By determining the position of the target spot 102 in relation to the image axis 36 on the trajectory 104 can the working distance of the symbol 100 be determined. The distance between the target spot 102 and the image axis 36 is proportional to the reciprocal of the working distance. Preferably, the position of the target spot 102 along the trajectory 104 calibrated in advance during the manufacture of the reader. As well as in the 5 - 6 shown captures the remote image generator 14 Pictures of the symbol 100 with a certain resolution, in this case a two-dimensional resolution of 800 lines of pixels in height by 1280 columns of pixels in width.

The aforementioned image preprocessor 56 is used to that of the remote image generator 14 captured images, thus the position of the target spot 102 to determine. To minimize costs, the image preprocessor 56 preferably integrated into a low-power, low-processing device, preferably without a frame buffer for storing images. As explained below, the image preprocessor has 56 Therefore, not the task of analyzing each individual recorded image, but only analyzes a subarea of each captured image, especially the sub-area in which it is expected that the target spot 102 along the trajectory 104 appears.

In particular, the controller activates 52 the target laser 46 to the target spot 102 on the icon 100 to judge. The remote imager 14 detects a first, complete or preferably partial image of the symbol 100 with the target spot 102 on it in a first frame. In response, the image preprocessor analyzes 56 only a portion of the first image in the first frame. As in 7 represented, the image preprocessor analyzes 56 not the pixels in row 0 to about row 400, or the pixels in row 560 to row 800, or the pixels in column 0 to about column 640 because the target spot 102 is not expected there and there is no reason to waste computing power or time analyzing pixels where the target spot 102 will not be available. The subarea or remaining area contains only about 160 lines of the original 800 lines of the full first image, and thus can be captured and analyzed much faster than the full first image.

The image preprocessor 56 Divide the remaining area of the first image into a matrix of subframes or coarse zones. As in 7 shown, the remaining area in sixteen, in general divided rectangular frames, z. B. four rows by four columns. The subframes do not need to have the same height, width or area. It is understood that the remaining area can be divided into any number of subframes. The number of subframes depends on the desired accuracy in the initially rough localization of the target spot 102 in the subframes.

The image preprocessor 56 Next, captures image data from each of the subframes. In particular, the tone or brightness values of all the pixels in each subframe are averaged to obtain an average brightness value. The image preprocessor 56 obtains a matrix of sixteen average brightness values, one for each subframe.

The controller then deactivates 52 the target laser 46 from, and the remote image generator 14 detects a second, complete or preferably partial image of the symbol 100 without the target spot 102 on it in a second frame. As before, the image preprocessor analyzes 56 only a portion of the second image in the second frame, and it is the same portion as it was used in the first frame. As before, the image pre-processor captures 56 Brightness values of all pixels in each subframe of the same subarea, average the brightness values in each subframe of the same subarea to obtain average brightness values, and obtain a matrix of sixteen mean brightness values, one for each subframe.

As a non-limiting numerical example, the matrix of the sixteen average brightness values with the target assembly deactivated is shown at the bottom of the left-hand side and the matrix of the sixteen mean brightness values with the target assembly activated at the bottom right-hand side: $$\begin{array}{cc}\text{Aim\_Off =}\left(\begin{array}{rrrr}\hfill 7729& \hfill 10501& \hfill 5965& \hfill 21158\\ \hfill 7214& \hfill 7715& \hfill 5841& \hfill 20854\\ \hfill 5740& \hfill 8623& \hfill 6118& \hfill 16340\\ \hfill 11012& \hfill 7696& \hfill 4729& \hfill 6908\end{array}\right)& \text{Aim\_On =}\left(\begin{array}{rrrr}\hfill 8482& \hfill 10672& \hfill 5939& \hfill 21283\\ \hfill 7400& \hfill 7693& \hfill 5847& \hfill 20791\\ \hfill 5758& \hfill 8602& \hfill 6092& \hfill 16263\\ \hfill 11010& \hfill 7587& \hfill \mathrm{4,638}& \hfill 6814\end{array}\right)\end{array}$$

The image preprocessor 56 Next, compare the two matrices by subtracting the average brightness value for each subframe, thereby obtaining in this numerical example the following difference matrix of brightness difference values: $$\text{Aim\_On}-\text{Aim\_Off =}\left(\begin{array}{rrrr}\hfill 0754& \hfill 0171& \hfill -0026& \hfill 0125\\ \hfill 0186& \hfill -0022& \hfill 0006& \hfill -0063\\ \hfill 0017& \hfill -0021& \hfill -0026& \hfill -0077\\ \hfill -0002& \hfill -0109& \hfill -0091& \hfill -0094\end{array}\right)$$

From the difference matrix it can be stated that the brightness difference value is in line 1 , Column 1 , stands out from the others by having the largest size or brightness difference. This identifies the position of the target spot 102 ,

If a higher accuracy in determining the position of the target spot 102 is desired, then the image preprocessor 56 an area around the identified position of the target spot 102 subdivide into a number of subareas. As in 8th represented, the image preprocessor divided 56 this area into a matrix of subregions or fine zones, e.g. B. in sixteen, generally rectangular sections, z. B. four rows by four columns. The sections do not need to have the same height, width or area. It is understood that this area can be divided into any number of subregions. The number of subregions depends on the desired accuracy in the subsequent fine localization of the target spot 102 in the subareas.

As before, enable and disable the controller 52 the target laser 46 , and the processor 56 obtains a matrix of sixteen average brightness values, one for each subarea with the activated target laser 46 and another matrix of sixteen average brightness values, one for each subarea with the target laser disabled 46 , The image preprocessor 56 Next, compare the two matrices by subtracting the average brightness value for each subarea and fine-localize the target spot 102 by finding the largest brightness difference value in at least one of the subregions.

In order to 7 It is observed that not all sixteen subframes need to be analyzed since the target spot 102 only appears in the shaded subframes that are along the trajectory 104 lie. This reduces the possibility of errors caused by moving objects or flashing light sources, which only occurs when the target laser is activated 46 occur in the picture and with the target spot 102 can be confused. The same principle of ignoring subframes can also apply to the top and bottom rows of the 8th shown sub-areas are applied.

In operation, as soon as the working distance to the symbol 100 is determined from the target spot position, the controller selects 52 either the close-up imager 12 and activates the illumination light assembly to display the icon 100 illuminate with illuminating light of a relatively lower intensity when the rangefinder determines that of the close-up 12 to be pictured and to be read symbol 100 located in a vicinity of the area; or select the remote imager 14 and illuminates the illumination light assembly to illuminate the target with illuminating light of relatively greater intensity when the rangefinder determines that the distance from the remote imager 14 to be pictured and to be read symbol 100 located in a far away area of the area.

Once the working distance to the icon 100 is determined from the target spot position, the controller 52 also the focusing of the remote image generator 14 adjust, for example, by changing the focus of the focusing element 38 , The control 52 activates the LED 40 with a variable electric current to vary the intensity of the illumination light. Once the working distance to the icon 100 is determined from the target spot position and / or as soon as the brightness values of each subframe are determined, the controller may 52 also adjust the gain and / or exposure of one or more imagers.

As in the flowchart of 9 shown, the procedure in step 200 by activating the aiming light assembly to make the aiming spot 102 along a target axis on the symbol 100 by capturing a first field of the symbol 100 in step 202 that the target light spot 102 and obtaining first image data from the first field in step 204 , Next, the aiming light assembly in step 206 deactivated, a second partial image of the symbol 100 will be without the aiming spot 102 in step 208 captured and second image data from the second field are in step 210 receive. The first and second image data are compared to a position of the target light spot 102 in step 212 to get, and the distance to the symbol 100 is based on the position of the target spot 102 in step 214 certainly. In step 216 will be the right imager 12 or 14 is selected, and / or the proper gain and / or exposure for the selected imager is adjusted, and / or the proper illumination from the LED 40 is adjusted and / or the focus of the selected imager is adjusted based on the determined distance.

In the foregoing description, specific embodiments have been described. One of ordinary skill in the art, however, recognizes that various modifications and changes can be made without departing from the scope of the invention as set forth in the appended claims. Accordingly, the description and figures are to be considered in an illustrative rather than a limiting sense, and all such modifications are intended to be included within the scope of the present teachings.

The benefits, benefits, solutions to problems, and any elements that may cause or enhance the benefit, benefit, or resolution, are not to be considered critical, required, or essential features or elements in the claims. The invention is defined solely by the appended claims, including any changes made during the pendency of this application, and all equivalents of the claims as granted.

Moreover, in this document, relational terms such as first and second, upper and lower, and the like may be used merely to distinguish one entity or action from another entity or action, without necessarily implying actual such relationship or order between such entities or actions require or imply. The terms "comprising," "comprising," "having," "having," "having," "having," "containing," "containing," or any other variation thereof are intended to cover a non-exclusive inclusion such that a A process, method, product, or device that includes, comprises, includes, includes, includes not only these elements but also other elements that are not explicitly listed or inherent in such a process, method, product, or device are. An element that includes "a ...", "has ... a", "has ... a" or "contains ... a" precedes, without further limitations, the existence of additional identical elements in the process, the process, product or device comprising, comprising or containing the element is not sufficient. The terms "a" and "an" are defined as one or more, unless expressly stated otherwise herein. The terms "substantially", "generally", "about", "about" or any other version thereof are defined as being readily understood by one of ordinary skill in the art, and in a non-limiting embodiment, 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 being connected, but not necessarily directly and not necessarily mechanically. A device or structure that is "engineered" in a certain way is at least as so, but may also be implemented in ways that are not listed.

It is understood that some embodiments may include one or more generic or specialized processors (or "processing devices") such as microprocessors, digital signal processors, custom processors and field programmable gate arrays (FPGAs), and one-time stored program instructions (including both software and software) Firmware) that control the one or more processors to implement, in conjunction with certain non-processor circuitry, some, most or all of the features of the method and / or apparatus described herein. Alternatively, some or all of the functions may be implemented by a state machine having no stored program instructions or in one or more application specific integrated circuits (ASICs) where each function or some combination of particular functions is implemented as user-defined logic. Of course, a combination of the two approaches can be used.

In addition, an embodiment may be implemented as a computer-readable storage medium having computer-readable code stored thereon to program a computer (including, for example, a processor) to perform a method as described and claimed herein. Examples of such computer-readable storage media include 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) Memory), an EEPROM (Electrically Erasable Programmable Read Only Memory) and a flash memory, but are not limited thereto. Further, it is believed that one of ordinary skill in the art, regardless of possible significant efforts and many design choices, motivated by, for example, available time, current technology, and economic considerations, is readily capable of such software instructions and programs and ICs with minimal experimentation as it is guided by the concepts and principles disclosed herein.

The summary of the disclosure is provided to enable the reader to quickly ascertain the nature of the technical disclosure. It is provided with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. Furthermore, it can be seen from the foregoing detailed description that various features are summarized in various embodiments for the purpose of streamlining the disclosure. This type of disclosure is not to be construed as reflecting the intent that the claimed embodiments require more features than are expressly stated in each claim. Rather, as the following claims demonstrate, the 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 (18)

An arrangement for determining a distance to a target to be read by image acquisition over a range of working distances, the assembly comprising: an activatable target assembly configured to direct a target spot along a target axis toward a target when activated; a controller configured to enable and disable the activatable target assembly; an imaging assembly configured to use the activated activatable target assembly to capture a first image of the target containing the target spot and to use the deactivated target activatable assembly to capture a second image of the target without the target spot, each of the first image and of the second image is detected in a corresponding frame via a field of view with an image axis offset from the target axis; and an image preprocessor configured to compare first image data from the first image with second image data from the second image over a common portion of each of the respective frames to obtain a position of the target light spot in the first image, and a distance from the first image Determine target based on the position of the target spot in the first image. Arrangement according to Claim 1 wherein the image preprocessor divides the common subarea into a plurality of subframes and compares the first and second image data in each of the plurality of subframes to obtain the position of the target light spot in at least one of the plurality of subframes. Arrangement according to Claim 2 wherein the image preprocessor divides a range around the position of the target spot into a plurality of portions, and compares the first and second image data in each of the plurality of portions to obtain the position of the target spot in at least one of the plurality of portions. Arrangement according to Claim 2 wherein the imaging assembly captures each of the first image and the second image as an array of pixels having brightness values, and wherein the image preprocessor is configured to average the brightness values in each of the plurality of subframes to obtain an average brightness value, and differences between compare the average brightness value of each of the plurality of subframes of the first image and the average brightness value of each of the plurality of subframes of the second image to obtain the position of the target light spot based on a largest difference between the average brightness values in at least one of the plurality of subframes. Arrangement according to Claim 1 wherein the activatable target assembly, the imaging assembly, and the image preprocessor are integrated into 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 be a second imager Imagine a target over a second imaging field of view, wherein the first target is positioned closer than the second target, wherein the first field of view is wider than the second field of view, and wherein the imaging assembly is the second variable focus imager. Arrangement according to Claim 5 wherein the controller adjusts a focus of the second imager based on a particular target distance. Arrangement according to Claim 5 wherein the controller selects one of the first imager and the second imager and adjusts at least one of gain and exposure for the selected imager based on a particular target distance. Arrangement according to Claim 5 , further comprising an illumination light assembly mounted on the module configured to generate a variable illumination light level, wherein the controller adjusts the illumination light level based on a particular target distance. Arrangement according to Claim 1 10, further adapted to adjust at least one read parameter of an imaging reader for reading targets, the controller further configured to adjust the at least one read parameter of the imaging reader based on a particular target distance. A method of determining a distance to a target to be read by image acquisition over a range of working distances, the method comprising the steps of: Directing a target spot along a target axis at the target; Capturing a first image of the target containing the target spot; subsequent not aiming the aiming spot; Acquiring a second image of the target without the target spot, each of the first image and the second image being captured in a corresponding frame via a field of view having an image axis offset from the target axis; Comparing first image data from the first image with second image data from the second image over a common portion of each of the respective frames to obtain a position of the target light spot in the first image; and Determining the distance to the target based on the position of the target spot in the first image. Method according to Claim 10 further comprising dividing the common portion into a plurality of subframes and comparing the first and second image data in each of the plurality of subframes to obtain the position of the target light spot in at least one of the plurality of subframes. Method according to Claim 11 further comprising dividing a range around the position of the target spot into a plurality of portions, and comparing the first and second image data in each of the plurality of portions to obtain the position of the target spot in at least one of the plurality of portions. Method according to Claim 11 wherein acquiring the first image and acquiring the second image is performed by respectively acquiring each of the first image and the second image as an array of pixels having brightness values, averaging the brightness values in each of the plurality of subframes to obtain an average brightness value and comparing differences between the average brightness value of each of the plurality of subframes of the first image and the average brightness value of each of the plurality of subframes of the second image to determine the position of the target light spot based on a largest difference between the average brightness values in at least one of To get variety of subframes. Method according to Claim 10 wherein at least one of capturing the first image and capturing the second image is configured by a first imager configured to image a first target via a first imaging field of view and a second imager configured to image a second target via a second imaging field of view , wherein the first target is positioned closer than the second target and the first field of view is wider than the second field of view, wherein one of the first imager and the second imager has a variable focus. Method according to Claim 14 further comprising adjusting a focus of the second imager based on a particular target distance. Method according to Claim 14 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 a particular target distance. Method according to Claim 14 , further comprising illuminating the target with a variable illumination light level, and adjusting the illumination light level based on a particular target distance. Method according to Claim 10 , further configured to adjust at least one read parameter of an imaging reader for reading targets, the method further comprising adjusting the at least one read parameter of the imaging reader based on a particular target distance.

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