Passive autofocus system and method

Abstract

Passive autofocus is used in image acquisition devices (e.g., machine-readable symbol readers, cameras), and may be used with shutters and / or event-based image sensors. The sight pointer is readily detected in the image, and one or more characteristics are characterized at respective focus positions of the optics. The size and / or shape of the characteristic dimension of the sight pointer and / or the measure of the sharpness of the sight pointer are used to determine which image (and thus the focus position) results in an optimized or even optimal (i.e., optimal) focus. An image acquisition system is then correspondingly configured. The calculation intensity of measuring the size of the pointer of the sighting device is generally lower than that of a conventional method. Generating a sight pointer using a laser beam generally requires shorter exposure times than other methods. The image data may advantageously be windowed using a relatively small region of interest (ROI) based on a known sight pointer position.

Description

Technical Field

[0001] The present disclosure generally relates to autofocusing, such as autofocusing used in image acquisition devices (e.g., machine-readable symbol readers, cameras), and particularly to passive autofocusing that employs a sighting pointer and can be used with a shutter image sensor or an event-based image sensor. Background Art

[0002] There are a wide variety of image acquisition devices. Examples of image acquisition devices include, but are not limited to: readers, cameras, scanners, and even the ubiquitous mobile or cellular smart phones. Such image acquisition devices generally include one or more image sensors and associated optics.

[0003] A particular type of reader is a machine-readable symbol reader for optically reading machine-readable symbols that encode information. Machine-readable symbols take many forms, the most common form being linear or one-dimensional machine-readable symbols, commonly referred to as barcode symbols. Other forms include two-dimensional machine-readable symbols, such as stacked code symbols, area or matrix code symbols, or QR code symbols. Machine-readable symbols can also include human-readable symbols (e.g., letters, numbers, punctuation marks).

[0004] Machine-readable symbols have a wide and diverse range of applications. For example, machine-readable symbols can be used to identify a class of objects (e.g., merchandise) or unique objects (e.g., patents). Thus, machine-readable symbols are found associated with a wide variety of objects, such as retail merchandise, company assets, packaging, parcels, and documents, and assist in tracking production at manufacturing facilities and inventory at stores (e.g., by scanning objects upon arrival and at the time of sale). In addition, machine-readable symbols can appear on the displays of portable electronic devices, such as cellular smart phones, tablet computers, laptop computers, or other devices having an electronic display. For example, a customer (such as a shopper, an airline passenger, or a person attending a sporting event or a theatrical event) can cause a machine-readable symbol to be displayed on their portable electronic device so that an employee (e.g., a merchant employee) can read the machine-readable symbol via a machine-readable symbol reader, thereby allowing the customer to redeem a coupon or verify that the customer has purchased a ticket for an event or boarded a vehicle.

[0005] A commonly used machine-readable symbol reader is an imager-based or imaging machine-readable symbol reader. Imager-based machine-readable symbol readers typically use flood illumination to illuminate the entire machine-readable symbol simultaneously, either from a dedicated light source or, in some cases, using ambient light. This is in contrast to scanning or laser (i.e., flying spot)-type machine-readable symbol readers, which sequentially scan a relatively narrow beam or spot (e.g., a laser beam) across the machine-readable symbol.

[0006] The image acquisition device can be fixed. For example, the machine-readable symbol reader can be fixed in a structure at a supermarket checkout or other point of sale. The machine-readable symbol reader can also be handheld (e.g., a handheld reader or even a smartphone), or even mobile (e.g., mounted on a vehicle such as a lift truck or forklift).

[0007] Whether fixed, handheld, or mobile, the field of view of the image acquisition device (e.g., a machine-readable symbol reader, a camera) is typically aimed at the target or the target is moved into the field of view of the image acquisition device.

[0008] To facilitate aiming, some image acquisition devices (e.g., machine-readable symbol readers) include a sighting subsystem that provides a sighting beam (e.g., a laser beam) and helps the operator position and / or orient the field of view of the image acquisition device relative to the target (e.g., a machine-readable symbol) by displaying a visual indication (called a sighting pointer) on the surface of the target object. The sighting pointer can take various forms, from a simple spot to a more complex geometric pattern that, for example, frames the area covered by the field of view of the image acquisition device. Some image acquisition devices (e.g., machine-readable symbol readers) can also include an active rangefinder to measure or estimate the reading distance, i.e., the distance between the image sensor of the image acquisition device and the target object.

[0009] Only when the target object is at a distance between a minimum and a maximum working distance can the machine-readable symbol reader use the measurement or estimation of the distance to activate a decoding algorithm and / or control a zoom device and / or the device to automatically change the focusing distance or focus or focal point of the machine-readable symbol reader. Moreover, the measurement or estimation of the distance can be used in cases where digital restoration of the image is required, because the degradation function or PSF (point spread function) of the optics of the image forming device may depend on the reading distance. Additionally, if this functionality is implemented in a particular machine-readable symbol reader, the measurement or estimation of the distance can be used to calculate the volume of the object.

[0010] When the distance between the object to be imaged and an image acquisition device (e.g., a machine-readable symbol reader, a camera) can vary, the focus or the focus point or the focus distance of the image acquisition device can be adjusted to ensure that the object is correctly focused on the image sensor of the image acquisition device.

[0011] In an autofocus system, it is important to have a method to focus the optics on the correct distance in an efficient and reliable manner. Autofocus techniques are mainly divided into two categories: active and passive. Conventional passive autofocus performs a complete focus sweep, evaluates the image contrast and decides which focus position is the best one to use. Passive autofocus is a reliable but slow closed-loop method. Active autofocus typically is based on additional signals generated from a source that is not part of the receiving system (e.g., additional sources such as time-of-flight sensors, laser triangulation from an external laser diode, phase shift, ultrasonic waves that measure the delay between transmission and reception). The additional signals provide measurements (e.g., steering delay, phase shift, point displacement within the received image) that can be directly related to the distance to the object (i.e., the object distance) and thus to the correct focus position. Active autofocus is a fast open-loop system, but its reliability depends on the sensor accuracy. If for some reason the feed-forward signal of the active autofocus system is not accurate enough to model the relationship between the distance and the lens focus, then a closed-loop method becomes preferred to determine the best focus position.

[0012] U.S. Patent 9,800,749 B1 describes a method using laser triangulation with two images, where a sight is activated in one image and deactivated in the other. The localization phase is based on combining the two images to identify the sight, which changes intensity from the first image to the second image, and the background is eliminated because it does not change.

[0013] Using a frame-based method commonly used for global / rolling shutter image sensors, pixels are exposed to light during a determined time window, and the entire image is output as intensity values of all image pixels at intervals determined by the frame rate during the readout phase.

[0014] In contrast, event-based image sensors utilize an event-based method that asynchronously detects pixel luminance changes and outputs data with pixel positions (e.g., XY coordinates) and time information. To this end, each pixel is equipped with signal processing circuitry for detecting luminance changes. This design enables the output data to potentially represent only those pixels that detect a luminance change of the target object. This advantageously allows event-based image sensors to immediately detect luminance changes at high speed, low latency, and high temporal resolution. Typically, the reconstructed image or more precisely the image information from such event-based image sensors will output the edges of moving objects and objects or parts thereof whose reflected light amount has changed. Event-based image sensors typically only output the sign of the change (e.g., positive change or negative change), rather than the intensity of the change. However, there are thresholds and parameters that can be set to regulate which pixels will trigger their events in response to specified conditions (e.g., intensity change trigger threshold). Summary of the Invention

[0015] In a system with a sight, classical contrast-based passive focusing can be replaced or assisted by checking the dimensions of the characteristic dimensions (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the sight pointer (e.g., laser spot sight pointer or two-dimensional pattern) while performing a focusing sweep of the optical device. Optimal focus is achieved when the sight pointer captured by the image sensor during the lens sweep has the smallest dimension in the corresponding image or image information.

[0016] In the case of event-based image sensors, the detection of optimized or even optimal focus is made very efficient, fast, and computationally simple because the reduction in the dimensions of the characteristic dimensions (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the sight pointer is very well highlighted by the typical output of such event-based image sensors.

[0017] The systems, articles, and methods described herein can advantageously improve reliability, for example when there is laser triangulation and it is not possible to accurately model the distance-lens focus relationship due to various effects such as lens aging, creep, temperature variations, etc.

[0018] The systems, articles, and methods described herein are generally also useful for passive autofocus systems, such as when there is a sighting subsystem and a fast-focusing optics system. For example, tunable MEMS lenses reach focus very quickly, but the voltage required for a particular diopter depends on various effects (such as creep and temperature) that are difficult to model precisely. Depending on the system conditions, the estimated lens focus position can be too far off from the actual situation to be used as the sole focusing method.

[0019] The systems, articles, and methods described herein can advantageously accelerate and simplify passive fine focusing for reaching an optimized or even optimal focus position, such as after performing active triangulation autofocus that does not reach the desired result precisely enough. In some embodiments, the methods described herein can also be used to perform a full passive focus sweep without computing contrast.

[0020] The systems, articles, and methods described herein can be used to find optimized or even optimal focus in a series of images during a focus sweep without using feature contrast as an indicator. Instead, the shape and / or the size of the characteristic dimensions of the sighting pointer are used to select which image has optimized or even optimal (i.e., best) focus, focus point, or focus distance. It is worth noting that there are some limitations to image contrast calculation, especially in low-light and featureless scenes. In particular, long exposure times are required to obtain sufficient signal for the contrast evaluation to work. Contrast evaluation is also generally quite computationally intensive, requiring analysis of a large portion of the image. In systems with fast-focusing lenses, the contrast evaluation sweep can be limited by the exposure time and / or the required ROI size related to the sensor readout time.

[0021] Measuring the sighting pointer size is less computationally intensive, especially if there is already a triangulation system (e.g., U.S. Patent Application 17 / 118,374, published as US20220187459A1) that locates the sighting pointer position to calculate distance. When using a laser beam to generate the sighting pointer, generally shorter exposure times are required because, at least for indoor scenes, the sighting pointer is usually the brightest scene element. If the sighting pointer position is known, for example, based on opto-mechanical characteristics, then a relatively small region of interest (ROI) can be used to window the image data. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the drawings, like reference numerals identify similar elements or acts. The dimensions and relative positions of the elements in the drawings are not necessarily drawn to scale. For example, the shapes and angles of the various elements are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the readability of the drawing. Additionally, the particular shapes of the elements drawn are not necessarily intended to convey any information regarding the actual shapes of the particular elements and may merely be selected for ease of identification in the drawings.

[0023] Figure 1 is a perspective view of an image acquisition system in the form of a machine-readable symbol reader positioned relative to a target object bearing a machine-readable symbol, according to one illustrated embodiment.

[0024] Figure 2 is a functional block diagram of a machine-readable symbol reader, according to one illustrated embodiment.

[0025] Figure 3A is, according to one illustrated embodiment, a schematic diagram of a shutter image sensor that can be used as part of a machine-readable symbol reader for Figure 1 and Figure 2 .

[0026] Figure 3B is, according to one illustrated embodiment, a schematic diagram of an event-based image sensor that can be used as part of a machine-readable symbol reader for Figure 1 and Figure 2 .

[0027] Figure 4 is a flow chart of a method of operation of an image acquisition system for a machine-readable symbol reader described for achieving passive autofocus to capture an image of a machine-readable symbol on a target object and optionally decode the machine-readable symbol, according to one illustrated embodiment.

[0028] Figure 5A is a graphical representation of the field of view of an image acquisition system including a sighting pointer in the form of a laser spot produced by an illumination source (e.g., a laser) of a sighting subsystem (e.g., the sighting subsystem of a machine-readable symbol reader) on a target object at a first focus, focal point, or focal distance, according to one illustrated embodiment.

[0029] Figure 5B is a graphical representation of the field of view of an image acquisition system including a sighting pointer in the form of a laser spot produced by an illumination source (e.g., a laser) of a sighting subsystem (e.g., the sighting subsystem of a machine-readable symbol reader) on a target object at a second focus, focal point, or focal distance, according to one illustrated embodiment.

[0030] Figure 6AAnd Figure 6B is a flowchart of a method for operating an image acquisition system for a machine-readable symbol reader having an event-based image sensor and implementing passive autofocus, in order to capture an image of a machine-readable symbol on a target object and optionally decode the machine-readable symbol, according to one illustrated embodiment.

[0031] Figure 7A is a graphical representation of image information representing a field of view including a sighting pointer in the form of a laser spot generated by an event-based image sensor of an image acquisition system, the laser spot being generated on a target object by an illumination source (e.g., a laser) of a sighting subsystem (e.g., the sighting subsystem of a machine-readable symbol reader), according to one illustrated embodiment.

[0032] Figure 7B is a graphical representation of image information representing a field of view generated by an event-based image sensor of an image acquisition system, but with the laser spot turned off and the illumination source of the sighting subsystem in the OFF state, according to one illustrated embodiment.

[0033] Figure 7C is a graphical representation of image information representing a field of view including a sighting pointer in the form of a laser spot generated by an illumination source (e.g., a laser) of a sighting subsystem on a target object at a first focus, focal point, or focal distance, the sighting pointer having a characteristic dimension of a first size, according to one illustrated embodiment.

[0034] Figure 7D is a graphical representation of image information representing a field of view including a sighting pointer in the form of a laser spot generated by an illumination source (e.g., a laser) of a sighting subsystem on a target object at a second focus, focal point, or focal distance, the sighting pointer having a characteristic dimension of a second size, the second size being smaller than the first size, according to one illustrated embodiment.

[0035] Figure 7E is a graphical representation of image information representing a field of view including a sighting pointer in the form of a laser spot generated by an illumination source (e.g., a laser) of a sighting subsystem on a target object at a third focus, focal point, or focal distance, the sighting pointer having a characteristic dimension of a third size, the third size being smaller than the second size, according to one illustrated embodiment.

[0036] Figure 8A flowchart of a method of operating a machine-readable symbol reader having a shutter image sensor, according to one illustrated embodiment, to capture successive images of a machine-readable symbol on a target object, compare image pairs, and output difference data similar to the output of an event-based image sensor.

[0037] Figure 9A A graphical representation of a reconstructed image of the field of view of an image acquisition system including a sighting pointer in the form of a laser speckle captured at two different times, the laser speckle being generated on a target object by an illumination source (e.g., a laser) of a sighting subsystem, and only pixels with intensity changes being shown to represent the change in the characteristic dimension of the laser speckle from a first size at a first time to a second size at a second time.

[0038] Figure 9B A graphical representation of a reconstructed image of the field of view of an image acquisition system including a sighting pointer in the form of a laser speckle captured at two different times, the laser speckle being generated on a target object by an illumination source (e.g., a laser) of a sighting subsystem, and only pixels with intensity changes being shown to represent the change in the characteristic dimension of the laser speckle from a second size at a second time to a third size at a third time immediately following the second time.

[0039] Figure 9C A graphical representation of a reconstructed image of the field of view of an image acquisition system including a sighting pointer in the form of a laser speckle captured at two different times, the laser speckle being generated on a target object by an illumination source (e.g., a laser) of a sighting subsystem, and only pixels with intensity changes being shown to represent the change in the characteristic dimension of the laser speckle from a third size at a third time to a fourth size at a fourth time immediately following the third time. Detailed Description

[0040] In the following description, certain specific details are set forth in order to provide a thorough understanding of the various disclosed embodiments. However, one of ordinary skill in the relevant art will recognize that the embodiments may be practiced without one or more of these specific details or with other methods, components, materials, etc. In other instances, well-known structures associated with machine-readable symbol readers, optics, sights, processors, and / or communication networks are not shown or described in detail to avoid unnecessarily obscuring the description of the embodiments.

[0041] Unless the context requires otherwise, throughout the specification and the following claims, the word "comprising" is synonymous with "including" and is inclusive or open-ended (i.e., does not exclude additional, unstated elements or method acts).

[0042] References to "one embodiment" or "an embodiment" in the present specification mean that a particular feature, structure, or characteristic described with respect to the embodiment is included in at least one embodiment. Thus, the phrases "in one embodiment" or "in an embodiment" that appear throughout the present specification do not necessarily all refer to the same embodiment. In addition, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0043] As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally used in its inclusive sense, including "and / or", unless the context clearly dictates otherwise.

[0044] The headings and "Abstract of the Invention" provided herein are for convenience only and do not interpret the scope or meaning of the embodiments.

[0045] The embodiments described in this disclosure are directed to systems, articles, and methods for performing passive autofocus using a sight pointer generated by a sighting subsystem of an image acquisition device, which allows for increased computational efficiency and / or operating speed of the image acquisition device. Although generally described with respect to machine-readable symbol readers, the teachings herein are not so limited, but rather may be applied to any device capable of projecting a sight beam to generate a sight pointer, which has adjustable optics, at least one image sensor capable of capturing an image of the sight pointer and / or other objects in the field of view, and at least one processor that can evaluate characteristics such as dimensionality (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis), shape and / or edge sharpness of the sight pointer at various focus positions, focus or focal length of the optics, etc. to determine the focus, focus position, focus point, or focus distance that results in optimized or even optimal focus. The characteristics evaluated are preferably not the illumination intensity level. The characteristics evaluated are preferably not the position or location of the sight pointer in the image frame. The method may advantageously employ a region of interest (ROI) sized to cover the sight pointer while omitting most of the entire image frame. The method may advantageously employ a laser source to generate the sight pointer (e.g., a laser spot sight pointer) to facilitate detection of the sight pointer in the captured image or image information. At least one processor may use the determined focus, focus position, focus point, or focus distance to configure the image acquisition device to acquire an image of a target in the field of view, such as an image of a machine-readable symbol or other target. Optionally, at least one processor may decode the captured machine-readable symbol.

[0046] Figure 1An image acquisition device in the form of a handheld machine-readable symbol reader 100 is shown, which is positioned and oriented relative to a target object 102 to acquire a machine-readable symbol 104 (e.g., a bar code symbol, a QR code symbol) carried or otherwise borne by the target object 102.

[0047] The handheld machine-readable symbol reader 100 can be an imaging-based machine-readable symbol reader. The handheld machine-readable symbol reader 100 optionally includes a grip portion 106 shaped and sized to be grasped by an operator's hand, and a scan head portion 108 extending from an upper portion of the grip portion. The lower portion of the grip portion 106 can be shaped and sized to be received in a docking station (not shown), e.g., to receive power for recharging and / or to transfer data. The machine-readable symbol reader 100 includes a front wall 114 of the scan head portion 108. The scan head portion 108 also includes one or more transparent windows 116 on the front wall 114, behind which a camera subsystem 202 ( Figure 2 ) and a sighting subsystem 214 ( Figure 2 ) are located, which are discussed hereinafter.

[0048] The machine-readable symbol reader 100 can be used in at least one of a handheld mode or a fixed-position mode. In the fixed-position mode, the reader 100 can be received in a docking station, and a target object 102 having a machine-readable symbol 104 can be brought within the angular field of view (FOV) 118 (a projection shown by a broken line) of the machine-readable symbol reader 100 so that the machine-readable symbol reader 100 reads and / or detects the machine-readable symbol 104. In the handheld mode, the reader 100 can be carried and positioned by an operator such that the surface of the target object 102 carrying the machine-readable symbol 104 is within the FOV 118 of the machine-readable symbol reader 100. In the handheld mode, the imaging and decoding of the target machine-readable symbol 104 can be automatically initiated or alternatively initiated by an operator actuating (e.g., pressing) a trigger 120.

[0049] For the purposes of this description, a handheld imaging-based machine-readable symbol system 100 is discussed. However, those of ordinary skill in the art will appreciate that the techniques and devices described herein can be advantageously practiced with stationary, mobile, dual-optical, or other types of readers or scan engines or other suitable image acquisition devices.

[0050] As described above, the machine-readable symbol reader 100 includes a sighting subsystem 214 ([[]] Figure 2), e.g., emitted from at least one window 116 of the front wall 114 of the scan head portion 108 of the machine-readable symbol reader. In the illustrated embodiment, the sighting subsystem 214 projects a sighting beam 122 outwardly from the front wall 114. The sighting beam 122 forms a sighting pointer 124 on the target object 102, thereby facilitating the aiming (e.g., positioning, orientation) of the FOV 118 of the machine-readable symbol reader 100 relative to the machine-readable symbol 104 to be read. The sighting pointer 124 can have any of a variety of shapes. In at least some embodiments, the sighting pointer 124 assumes the form of a spot (e.g., circular, oval, elliptical) when illuminating the target object 102 orthogonally. This can allow for the use of a relatively small region of interest (ROI) as described herein. Alternatively, the sighting pointer 124 can have a more complex shape, such as a cross, a bull's-eye pattern, a rectangle or square, or portions of a rectangle or square (e.g., two opposite corners, two pairs of opposite corners). The sighting beam 122 can, for example, take the form of a laser beam generated by a laser source (e.g., a laser diode). This can advantageously facilitate detection and processing as described herein. The sighting subsystem 214 can be positioned behind the window 116, adjacent to the camera subsystem 202 ( Figure 1 ). The length of the laser beam 122 depends on the distance of the target object 102 from the machine-readable symbol reader 100. In addition to allowing an operator to aim the machine-readable symbol reader 100 relative to the machine-readable symbol 104 carried on the surface of the target object 102, the sighting pointer 124 is advantageously used to perform passive autofocusing, thereby determining an optimized or even optimal focus of the optics for a given position of the machine-readable symbol reader 100 relative to the target object 102, as further discussed below.

[0051] Figure 2 is a block diagram of an image acquisition device in the form of an imaging-based machine-readable symbol reader 200 according to at least some embodiments of the present disclosure. The machine-readable symbol reader 200 can be similar or even identical to Figure 1 the handheld machine-readable symbol reader 100.

[0052] The machine-readable symbol reader 200 includes a camera subsystem 202 that captures image frames or portions thereof or image information. The camera subsystem 202 can, for example, capture an image of the sighting pointer 124 ( Figure 1 ), or image information representative of the sighting pointer 124, and / or capture graphic markings (such as the machine-readable symbol 104 ( Figure 1)) or image information representing a graphical marker. The machine-readable symbol reader 200 also includes one or more processors 204 operatively coupled to one or more non-transitory processor-readable storage media 206. The non-transitory processor-readable storage media 206 stores instructions or logic executable by a passive autofocus processor and optionally stores instructions or logic 210 executable by a decoder processor. Execution of the decoder instructions or logic by the (one or more) processors 204 causes the (one or more) processors 204 to decode the encoded markers within the captured image frames. Given the distance of a target object relative to the machine-readable symbol reader 200, execution of the passive autofocus instructions or logic by the (one or more) processors 204 causes the (one or more) processors 204 to determine an optimized or even optimal focus, focus position, focus point, or focus distance, as discussed below. The passive autofocus instructions or logic and the decoder instructions or logic may be executed by one or more processors 204, for example, by the same processor, by corresponding processors, or even by multiple processors separately. In some embodiments, one or both of the passive autofocus instructions or logic and the decoder instructions or logic are implemented by multiple processors, by other hardware, or by any combination thereof. In one or more embodiments, the one or more non-transitory storage media 206 may include, for example, volatile memory (e.g., random access memory (RAM)) that stores acquisitions to be processed (e.g., image information), and non-volatile memory (e.g., read-only memory (ROM), FLASH memory, spin-transfer torque memory) that stores processor-executable instructions or logic, for example. Generally, the passive autofocus instructions or logic and the decoder instructions or logic may be implemented in any suitable manner via one or more of the following, including hardware, software, circuitry, firmware: one or more application-specific integrated circuits (ASICs), one or more graphics processing units (GPUs), one or more digital signal processors (DSPs), one or more programmable gate arrays (PGAs) (e.g., field-programmable gate arrays (FPGAs) or complex programmable logic devices (CPLDs)), and / or one or more microcontrollers, or any combination thereof.

[0053] The camera subsystem 202 includes one or more image sensors 208, one or more adjustable-focus optical subsystem 210 (including optics 212 with adjustable focus), and optionally one or more shutters. In some embodiments, the shape of one or more lenses may be adjusted, such as a microfluidic lens. In some embodiments, the distance of one or more lenses may be adjusted, for example, relative to the aperture or relative to one or more other lenses.

[0054] (One or more) image sensors 208 can take various forms, such as global shutter image sensors, rolling shutter image sensors, and / or event-based image sensors, as discussed below with reference to Figure 3A and Figure 3B discussed.

[0055] The adjustable focusing optical device subsystem 210 includes one or more actuators (not shown) operable to adjust the focus of the optical device 212. The optical device 212 can take various forms, including a single lens, multiple lenses, compound lenses, microelectromechanical systems (MEMS) lenses, microfluidic lenses, lenses with non-zero optical power, lenses with zero optical power, mirrors or reflectors, dichroic mirrors, prisms, optical filters, etc. The (one or more) actuators can take any of various forms, and a particular actuator is a function of a particular optical device. For example, the actuator can include a solenoid, magnet, electromagnet, electrode, electric motor, etc., that are coupled to change the shape of one or more of the optical devices 212 and / or change the position of one or more of the optical devices 212 relative to the (one or more) image sensors 208 and / or relative to other optical devices 212 or relative to the window 116 ( Figure 1 ).

[0056] The optical device (e.g., focusing lens) 212 of the adjustable focusing optical device subsystem 210 focuses the light reflected and scattered from the target machine-readable symbol 104 ( Figure 1 ) onto at least one image sensor 202, typically through an aperture. As described herein, the adjustable focusing optical device subsystem 210 initially focuses the image of the aiming pointer 124 ( Figure 1 ) onto the array of pixels of the (one or more) image sensors 208 at various different focusing positions or settings as part of performing passive autofocus. Also as described herein, once passive autofocus is complete, the adjustable focusing optical device subsystem 210 focuses the target machine-readable symbol 104 (assuming the symbol is within the FOV) onto the array of pixels of the (one or more) image sensors 208, enabling the (one or more) image sensors 208 to capture an image of the target object (e.g., the target machine-readable symbol 104 ( Figure 1 )) that appears within the FOV 118 ( Figure 1 ) of the camera subsystem 202 during the exposure period or at least capture image information representative of the target object. The FOV 118 ( Figure 1 ) of the camera subsystem 202 can depend on the configuration of the (one or more) image sensors 208, the optical characteristics of the optical device 212 of the adjustable focusing optical device subsystem 210, and the distance and orientation between the (one or more) image sensors 208 and the optical device 212.

[0057] (One or more) image sensors 208 can take various forms, such as an array of charge-coupled devices (CCDs), an array of complementary metal-oxide semiconductor (CMOS) devices, or other imaging pixel arrays. (One or more) image sensors 208 can have various numbers of pixels arranged in various sizes along the X-axis and Y-axis. The pixels of (one or more) image sensors 208 should generally be large enough to provide sufficient SNR performance when combined with the image-forming optics 212 and associated aperture.

[0058] The optics 212 can include a wide-angle lens that provides an angular FOV. The optics 212 can have a relatively short focal length, which allows for the implementation of an entire camera subsystem 202 with a relatively small overall length. The aperture of the camera subsystem 202 provides a desired depth of field (DoF). In some embodiments, the camera subsystem 202 can be characterized by any suitable f-number for any suitable specific intended application.

[0059] The machine-readable symbol reader 200 includes a sighting subsystem 214 to generate a visible sighting pointer 124 ( Figure 1 ), to assist an operator in aiming the machine-readable symbol reader 200 relative to a target machine-readable symbol 104 and for performing passive autofocus. In some embodiments, the sighting subsystem 214 can include a light source 216 (e.g., one or more LEDs, lasers, superluminescent diodes). The light source is preferably a laser light source, such as a laser diode 216. The sighting subsystem 214 can optionally include one or more of the following: a focusing lens (e.g., a collimator), an aperture, and / or a pattern generator (e.g., a beam shaper) to generate a desired shape of the sighting pointer 124 ( Figure 1 ). In some embodiments, the focusing lens and the pattern generator can be formed in a single optical element.

[0060] In some embodiments, the sighting pointer 124 ( Figure 1 ) is used by the operator to position and / or orient the FOV 118 ( Figure 1 ) to cover the target (e.g., the machine-readable symbol 104). In at least one embodiment, the machine-readable symbol readers 100, 200 perform passive autofocus, and upon completion of this operation, acquire an image or image information from the machine-readable symbol 104 using configuration parameters that depend on the result of the passive autofocus. In some embodiments, the machine-readable symbol readers 100, 200 can automatically start passive autofocus when a return or reflection of the sighting pointer 124 is detected. Alternatively, the operator can press a trigger 120 ( Figure 1) to begin passive autofocus. In some embodiments, the machine-readable symbol readers 100, 200 automatically read or capture an image or image information of the target machine-readable symbol 104( Figure 1 ) when passive autofocus is completed. In still other embodiments, the machine-readable symbol readers 100, 200 read or capture an image or image information of the target machine-readable symbol 104( Figure 1 ) in response to the operator actuating the trigger 120 when passive autofocus is completed (e.g., in response to a visual or audible indication that passive autofocus has been completed). In some embodiments, the machine-readable symbol readers 100, 200 have a two-position trigger 226, where the first position activates the sighting subsystem 214 and the second position activates the reading of the machine-readable symbol 104( Figure 1 ). In some embodiments, the machine-readable symbol readers 100, 200 include an optional motion detector (e.g., an accelerometer) that is used to activate the sighting subsystem 214 when movement of the reader is detected, and such movement may indicate that the operator has picked up the machine-readable symbol readers 100, 200 for a reading operation.

[0061] The sighting subsystem 214 may project a line having an angular projection field (FOP) with an angle smaller than the FOV of the camera subsystem 202, such that the line is projected only onto a portion (e.g., substantially the central portion) of the FOV of the camera subsystem. In at least some embodiments, when the line is projected orthogonally onto a flat or nearly flat surface, it is preferred that the line visually appears as a simple dot sighting pointer 124. In some embodiments, it is preferred to use a laser source 216 so that the (one or more) image sensors 208 can be easily discerned even outdoors or under other uncontrolled conditions.

[0062] The machine-readable symbol readers 100, 200 optionally include a flood illumination subsystem 218. The flood illumination subsystem 218 includes one or more light sources that are operable to provide flood illumination across the entire machine-readable symbol 104( Figure 1 ) simultaneously. The light source may include, for example, at least one of a light-emitting diode (LED), an incandescent lamp, or a superluminescent diode. The flood illumination subsystem 218 may be activated in response to the completion of passive autofocus to facilitate capturing an image of or capturing image information from the machine-readable symbol 104( Figure 1 ).

[0063] As further discussed below, decoder logic or instructions can decode any decodable images within one or more images captured by camera subsystem 202. Various decoding techniques can be employed. If decoding is successful, the decoded data representing the encoded data / information in machine-readable symbol 104 is output via a data input / output system, which can include one or more of a wired / wireless communication port, a display, an LED, an audio output, a touchscreen, a keypad, buttons, etc. After successfully imaging and decoding machine-readable symbol 104, the input / output system can provide feedback to the operator in the form of a visual indication and / or an audible indication.

[0064] Figure 3A is a schematic diagram of a shutter image sensor 300a that can be used as part of a machine-readable symbol reader 100, 200 according to one illustrated embodiment. Figure 1 and Figure 2 of the machine-readable symbol reader 100, 200 according to one illustrated embodiment.

[0065] The shutter image sensor 300a can take the form of a global shutter image sensor 300a or a rolling shutter image sensor. In either case, the pixels of the shutter image sensor 300a are exposed to light during a determined time window and output the entire image as a frame with intensity values of all image pixels during a readout phase. The frames are output at intervals determined by a frame rate.

[0066] The shutter image sensor 300a includes an image sensor 302a, and the image sensor 302b includes an array 304a of photosensitive pixels. The image sensor 302a can include a plurality of output contacts (e.g., pins) 306a (only one is labeled) to provide output data for the pixels to a processor, a register, or other memory. The shutter image sensor 300a also optionally includes one or more physical shutters 308, which are operable to selectively expose all pixels of the array 304a of photosensitive pixels to incoming light simultaneously. The (one or more) shutters 306 are located between the array 304a of photosensitive pixels and the exterior of the machine-readable symbol readers 100, 200. Alternatively, the shutter image sensor 300A optionally implements a logical rolling shutter, for example, by successively sampling multiple regions (e.g., row by row or group of rows) of the array 304a of photosensitive pixels.

[0067] Figure 3B is a schematic diagram of an event-based image sensor 300b that can be used as part of a machine-readable symbol reader according to one illustrated embodiment. Figure 1 and Figure 2 of the machine-readable symbol reader according to one illustrated embodiment.

[0068] Unlike the shutter image sensor 300a ( Figure 3A)In contrast, event-based image sensors utilize an event-based method that asynchronously detects changes in pixel luminance and outputs data with pixel positions (e.g., XY coordinates) and time information.

[0069] The event-based image sensor 300b includes an image sensor 302b, which includes an array 304b of photosensitive pixels. Each pixel is equipped with signal processing circuitry for detecting changes in luminance. The event-based image sensor 300b may include a plurality of output contacts (e.g., pins) 306b (only one is labeled) for providing output data for the pixels to a processor, register, or other memory. The array 304b of photosensitive pixels is operable to selectively output a signal only when the level of illumination intensity sensed by a corresponding pixel has changed relative to the most recently sensed level of illumination intensity. Thus, the output will be provided only to those pixels that have experienced a change. In some embodiments, the amount of change may need to exceed a specified threshold to trigger an output. The output may indicate that a change has occurred and may even indicate the direction of the change (e.g., whether the intensity is increasing or decreasing), but typically does not provide any indication of the magnitude of the change. The event-based image sensor 300b advantageously detects changes in luminance immediately at high speed, low latency, and high temporal resolution.

[0070] In some embodiments, an image acquisition system (e.g., a machine-readable symbol reader) may include two or more image sensors, such as a global shutter image sensor and an event-based image sensor. In such an embodiment, the event-based image sensor may be used for optimal focus search, while the global shutter image sensor may be used to adjust the focus based on the focus position found by the event-based image sensor in order to acquire an image for decoding.

[0071] Figure 4 A method 400 of operating an image acquisition system described for a machine-readable symbol reader that implements passive autofocus is shown, to capture an image of a machine-readable symbol on a target object and optionally decode the machine-readable symbol, according to one illustrated embodiment. The method 400 may be performed by an image acquisition system (e.g., a machine-readable symbol reader, such as Figure 1 and Figure 2 machine-readable symbol readers 100, 200).

[0072] As discussed previously, a machine-readable symbol reader can include a sighting subsystem that is operable to project a sighting beam outside of the machine-readable symbol reader to create a sighting pointer. The machine-readable symbol reader can also include optics with adjustable focus. The machine-readable symbol reader can also include at least one image sensor having an optical path that provides a field of view (FOV) extending outward from the machine-readable symbol reader through the optics. The at least one image sensor is operable to capture image information from objects (including the sighting pointer) and any machine-readable symbols that appear in the FOV. The machine-readable symbol reader can also include one or more processors that perform passive autofocusing, configure the machine-readable symbol reader to capture image information from machine-readable symbols that appear in the field of view, and optionally decode the captured machine-readable symbols.

[0073] The systems and methods described herein can advantageously replace classical contrast autofocus sweeps, such as when performing a full passive focus run or when performing a fine focus sweep around an estimated focus position (e.g., calculated according to a distance-to-focus triangulation formula).

[0074] Method 400 begins at 402, for example, when a user picks up the machine-readable symbol reader to scan a machine-readable symbol (e.g., 1D or 2D barcode, alphanumeric characters) carried by a target object or item (e.g., clothing, packaging, circuit board, label), such as when a trigger is actuated, or when the target object or item is otherwise presented to the machine-readable symbol reader.

[0075] At 404, at least one processor of the machine-readable symbol reader can generate, calculate, determine, or otherwise access a focus step specification, also referred to as a set of focus positions or focus position steps. The focus positions or focus position steps specify a plurality of specific focus positions or focus position steps of the optics to be attempted (e.g., swept through). For example, at least one processor of the machine-readable symbol reader can generate, calculate, determine, or select the set of focus position steps based on, for example, an initial estimate of the distance to the target object. The estimate (such as active distance information) can advantageously allow the use of a relatively small set of focus positions or focus position steps arranged around the calculated best focus estimate. If active distance information is not available, then at least one processor can generate, calculate, determine the set of focus positions or focus position steps to ensure coverage of all possible focus positions.

[0076] At 406, at least one processor of the machine-readable symbol reader can cause the aiming subsystem to project an aiming beam outside the machine-readable symbol reader to generate an aiming pointer. The aiming pointer can be used to position and / or orient the machine-readable symbol reader, and in particular to position and / or orient at least one image sensor of the machine-readable symbol reader relative to the field of view of the target object. As described herein, the aiming pointer is also used to perform passive autofocus. The aiming subsystem can, for example, turn on or activate an illumination source (e.g., a laser diode) to generate the aiming beam.

[0077] At 408, at least one processor of the machine-readable symbol reader can set an exposure time (e.g., a fixed exposure time) and / or an analog gain (e.g., a fixed analog gain) suitable for correctly exposing the aiming pointer (e.g., a laser spot) for at least one image sensor of the machine-readable symbol reader. Different types of aiming pointers and in particular different types of aiming illumination (e.g., illumination intensity, wavelength) and target object reflectivity can specify different exposure times and analog gains. Using a laser source to generate the aiming beam can result in a relatively short exposure time and a relatively small analog gain even in low light conditions because these values depend only on the laser light power, target reflectivity, and target color. A small exposure time is useful for increasing the frame rate during the focus position sweep phase (i.e., sweeping through the focus position or focus position steps).

[0078] At 410, at least one processor of the machine-readable symbol reader can set a suitable region of interest (e.g., a fixed region of interest or a fixed ROI) to obtain an image of the aiming pointer or to obtain image information therefrom without obtaining too much additional image or image information. In a triangulation system, the ROI is typically a small stripe oriented on the same axis as the mechanical offset between the aiming device and the receiver (e.g., a photodiode). The ROI can be a small portion of the complete image, e.g., a subset of the pixels of at least one image sensor, the subset corresponding to the area where the aiming pointer is expected or predicted to appear within the entire frame. Using the ROI can advantageously speed up the readout time and thus the frame rate during the sweep phase. The frame rate is typically limited by the longer of the exposure time and the readout time. Employing the ROI reduces the number of pixels sampled and the amount of image information to be processed, thus advantageously reducing the computational complexity and increasing the speed.

[0079] At 412, at least one processor of the machine-readable symbol reader may adjust an optical device (e.g., one or more lenses) to focus at each focus position or focus position step while acquiring an image or image information at each focus position or focus position step. Thus, the processor sweeps through the set of focus positions or focus position steps, thereby acquiring an image or image information at each focus position or focus position step. The speed of the sweep is limited by the longer of the sensor frame rate and the time to adjust the focus of the optical device (e.g., lens focusing time).

[0080] At 414, at least one processor of the machine-readable symbol reader may process the image or image information acquired by at least one image sensor during the focus sweep. The processing may include determining a characterization aspect of at least one of one or more characteristics of a sighting pointer in a frame, e.g., determining the size and / or shape of at least one characteristic dimension (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the sighting pointer and / or determining the edge sharpness (e.g., a measure of edge sharpness) of the sighting pointer (e.g., sighting illumination spot, sighting laser spot). Such image processing for finding and characterizing the sighting pointer within a frame of the image may be performed with various techniques (e.g., techniques for performing laser triangulation).

[0081] At 416, at least one processor of the machine-readable symbol reader may select the image having the smallest characteristic dimension (e.g., smallest laser spot size), shape, and / or having the best edge sharpness (e.g., sharpest edge) as the best focus position or focal length in the focus sweep and move the lens to the selected focus position, which is shown in Figure 5A and Figure 5B and discussed below.

[0082] At 418, at least one processor of the machine-readable symbol reader may reset the image sensor configuration (exposure, gain, windowing) to acquire an image for decoding. The image sensor configuration may depend on the characteristics of the (one or more) image sensors, the reflectivity of the target object or machine-readable symbol, and / or the optical device.

[0083] Optionally, at 420, if the focus of the optical device has not been set to the optimized focus position, then adjust the focus of the optical device based on the optimized focus position determined via passive autofocus.

[0084] Optionally, at 422, at least one image sensor acquires an image or image information using a reset image sensor configuration and an optimized focus position. The image or image information can represent, for example, one or more machine-readable symbols in the FOV of a machine-readable symbol reader or its (one or more) image sensors.

[0085] Optionally, at 424, at least one processor decodes the machine-readable symbols represented in the captured image. Conventional machine-readable symbol decoding techniques can be employed.

[0086] Method 400 can terminate at 426, for example, until called again. Alternatively, method 400 can be continuously repeated. In some embodiments, method 400 can be executed by multiple threads, for example, via a multi-threaded processor.

[0087] Although method 400 is illustrated and described as a series of ordered actions or operations, in some embodiments, the method can omit some actions or operations, include other actions or operations, and / or can execute some actions or operations in an order different from the order shown. In some embodiments, the passive autofocus sequence of method 400 can be restarted, for example, when a timeout and an end condition occur, or if the scene changes or the scene brightness changes beyond a set brightness change threshold.

[0088] Figure 5A The field of view 500a of an image acquisition system including a sighting pointer in the form of a laser spot 502a is shown, which is generated by an illumination source (e.g., a laser) of a sighting subsystem (e.g., the sighting subsystem of a machine-readable symbol reader) on a target object 504 at a first focal length.

[0089] Figure 5B The field of view 500b of an image acquisition system including a sighting pointer in the form of a laser spot 502b is shown, which is generated by an illumination source (e.g., a laser) of a sighting subsystem (e.g., the sighting subsystem of a machine-readable symbol reader) on a target object 504 at a second focal length.

[0090] As can be seen by comparing Figure 5A with Figure 5B There is a relationship between the focus and the dimensions of the characteristic dimensions (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the laser spots 502a, 502b. Optimized focus (e.g., best focus, focus position, focus point, or focus distance) is generally associated with the minimum dimension of the characteristic dimensions of the laser spots 502a, 502b.

[0091] Figure 5A and Figure 5B An example region of interest (ROI) 506 is also shown. The ROI can specify an area where a sight pointer (e.g., laser spots 502a, 502b) is likely or expected or predicted to appear. Thus, the ROI can be employed to reduce the amount of image information that needs to be captured by the image sensor, read from the image sensor, and / or processed by the processor as part of passive autofocus, thereby advantageously reducing the time for reading and processing image information from the image sensor and / or increasing the frame capture rate (frame rate) of the image sensor.

[0092] If the passive autofocus system uses an event-based image sensor, then with respect to Figure 6A and Figure 6B the described method may be particularly efficient, and thus its event-based nature and differential representation can be exploited to adjust the focus in a very precise, fast, and computationally easy manner, as will be described below.

[0093] The image information provided by an event-based image sensor (also known as an event-based camera) to the processor is only related to the change in the brightness of the pixels. This is in contrast to a shutter image sensor (also known as a shutter camera) that provides the values of all pixels of a frame. This means that if the only significant change that occurs is the size of the sight pointer, then it will be very clear whether the image sensor is in focus, and at the same time, a very high frame rate is allowed compared to the shutter image sensor because there is no need to wait for the shutter to open and close, nor to read out all the pixels in the ROI. Therefore, when adjusting the focus of the optics (e.g., the lens), it can be determined in real-time or near real-time whether the size of the sight pointer is shrinking or growing, and in which direction to focus (towards near focus, towards far focus) and when the optimized focus position is achieved.

[0094] When the correct focus is determined, the sight beam can be turned off, and then an optional general illuminator (e.g., flood illumination) can be turned on so that the image sensor will capture an image or image information and output image data (e.g., digital image data) for processing, analysis, and / or decoding according to the purposes of the specific application. The following references Figure 6A and Figure 6B describe exemplary methods for achieving this.

[0095] Figure 6A and Figure 6B show a method 600 for the operation of an image acquisition system described for a machine-readable symbol reader that implements passive autofocus to capture an image of a machine-readable symbol on a target object and decode it. Method 600 can be performed by an image acquisition system (e.g., a machine-readable symbol reader such as Figure 1 and Figure 2is performed by the machine-readable symbol readers 100, 200), and may in particular utilize an event-based image sensor, such as the event-based image sensor 300b( Figure 3B ).

[0096] As discussed previously, the machine-readable symbol reader may include a sighting subsystem operable to project a sighting beam outside the machine-readable symbol reader to produce a sighting pointer. The machine-readable symbol reader optics may also include optics with adjustable focus. The machine-readable symbol reader optics may also include at least one image sensor having a FOV that extends outside the machine-readable symbol reader through the optics and is operable to capture an image of or image information from objects (including the sighting pointer and machine-readable symbols) appearing in the field of view. The machine-readable symbol reader optics may also include at least one processor that performs passive autofocus, configures the machine-readable symbol reader to capture image information from machine-readable symbols appearing in the FOV, and optionally decodes the captured machine-readable symbols.

[0097] The systems and methods described herein may advantageously replace classical contrast autofocus sweeps, such as when performing a full passive focus run or when performing a fine focus sweep around an estimated position calculated, for example, according to a distance-to-focus triangulation formula. Generally, the focus may be adjusted in two opposite directions, towards near focus or towards far focus. In some embodiments, the focus may first be adjusted towards near focus and then towards far focus. In some embodiments, the focus may first be adjusted towards far focus and then towards near focus. Thus, method 600 is described with respect to a first focus direction and a second focus direction to clarify that method 600 is applicable to either embodiment, regardless of which focus direction is employed first.

[0098] Method 600 begins at 602, for example, when the user picks up the machine-readable symbol reader to scan a machine-readable symbol (e.g., 1D or 2D barcode, alphanumeric characters) placed on a target object or item (e.g., clothing, packaging, circuit board), or when a trigger is actuated, or when the target object or item is otherwise presented to the machine-readable symbol reader.

[0099] At 604, at least one processor of the machine-readable symbol reader can generate, calculate, determine, or otherwise access a focusing step specification (also referred to as a set of focusing position steps). The focusing positions or focusing position steps specify a plurality of specific focusing positions or focusing position steps to be attempted (e.g., swept through) by the optics. For example, at least one processor of the machine-readable symbol reader can generate, calculate, determine, or select the set of focusing position steps based on, for example, an initial estimate of the distance to the target object. An estimate such as active distance information can advantageously allow the use of a relatively small set of focusing position steps arranged around the calculated best focus estimate. If no active distance information is available, then at least one processor can generate, calculate, determine the set of focusing position steps to ensure coverage of all possible focusing positions, but may not traverse all of the focusing positions or focusing position steps in any given iteration of method 600.

[0100] At 606, the event-based image sensor is turned on. For example, at least one processor of the machine-readable symbol reader can turn on the event-based image sensor or cause image information to be captured, read, or otherwise received from the event-based image sensor.

[0101] At 608, at least one processor of the machine-readable symbol reader can cause the aiming subsystem to project an aiming beam outside the machine-readable symbol reader to produce an aiming pointer. The aiming pointer can be used to position and / or orient the machine-readable symbol reader relative to the target object, in particular the FOV of the machine-readable symbol reader and / or its image sensor. The aiming subsystem can, for example, turn on or activate an illumination source (e.g., a laser diode) to generate the aiming beam.

[0102] At 610, at least one processor of the machine-readable symbol reader can process the image or image information acquired or generated by the event-based image sensor, the processing including, for example, determining the characteristics of the aiming pointer and optionally determining the position or location of the aiming pointer in the frame. Determining the characteristics of the aiming pointer can include, for example, determining the size of at least one characteristic dimension (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the aiming pointer (e.g., aiming illumination spot, aiming laser spot) and / or determining the edge sharpness of the aiming pointer (e.g., aiming illumination spot, aiming laser spot).

[0103] Method 600 enters a first iteration loop 612, including actions 614, 616, and 618.

[0104] At 614, at least one processor of the machine-readable symbol reader can adjust the optics (e.g., one or more lenses) to focus on the next focus position or focus position step in a first focusing direction (e.g., towards near focus, or towards far focus).

[0105] At 616, at least one processor of the machine-readable symbol reader determines or otherwise detects whether there is a change in the sighting pointer (e.g., sighting illumination spot, sighting laser spot). For example, at least one processor can determine whether the dimensions of a characteristic dimension (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the sighting pointer (e.g., sighting illumination spot, sighting laser spot) have changed or varied (e.g., increased or gotten larger, decreased or gotten smaller). Also, for example, at least one processor can determine whether the edge sharpness of the sighting pointer (e.g., sighting illumination spot, sighting laser spot) has changed or varied (e.g., edge sharpness increased or improved, edge sharpness decreased or degraded).

[0106] At 618, at least one processor of the machine-readable symbol reader determines whether a characteristic dimension (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the sighting pointer (e.g., sighting illumination spot, sighting laser spot) is shrinking or getting smaller and / or whether the edge sharpness is increasing or improving. In response to determining that the sighting pointer is shrinking or getting smaller and / or the edge sharpness is increasing or improving (yes), control returns to 614 to sweep through the focus position steps in the first focusing direction. In response to determining that the sighting pointer is not shrinking or getting smaller and / or the edge sharpness is not increasing or improving (no), control proceeds to enter the second iteration loop 620.

[0107] The second iteration loop 620 includes actions 622, 624, and 626.

[0108] At 622, at least one processor of the machine-readable symbol reader can adjust the optics (e.g., one or more lenses) to focus on the next focus position or focus position step in a second focusing direction (e.g., towards far focus, or towards near focus), the second focusing direction being opposite to the first focusing direction.

[0109] At 624, at least one processor of the machine-readable symbol reader determines or otherwise detects whether there is a change in the aiming pointer (e.g., aiming illumination spot, aiming laser spot). For example, at least one processor may determine whether the dimensions of a characteristic dimension (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the aiming pointer (e.g., aiming illumination spot, aiming laser spot) have changed or varied (e.g., increased or gotten larger, decreased or gotten smaller). Also, for example, at least one processor may determine whether the edge sharpness of the aiming pointer (e.g., aiming illumination spot, aiming laser spot) has changed or varied (e.g., the edge sharpness has increased or improved, the edge sharpness has decreased or deteriorated).

[0110] At 626, at least one processor of the machine-readable symbol reader determines whether a characteristic dimension (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis) of the aiming pointer (e.g., aiming illumination spot, aiming laser spot) is shrinking or getting smaller and / or whether the edge sharpness is increasing or improving. In response to determining that the aiming pointer is shrinking or getting smaller and / or the edge sharpness is increasing or improving (yes), control returns to 622 to sweep through the focus position step in a second focusing direction (e.g., toward far focus or toward near focus), the second focusing direction being opposite to the first focusing direction. In response to determining that the aiming pointer is not shrinking or getting smaller and / or the edge sharpness is not increasing or improving (no), control proceeds to 628.

[0111] Optionally, at 628, if the focus of the optical device has not been set to the optimized focus position, then adjust the focus of the optical device based on the optimized focus position determined via passive autofocus.

[0112] At 630, at least one processor of the machine-readable symbol reader may set the image sensor configuration (exposure, gain, window) to obtain an image for decoding.

[0113] Optionally, at 632, at least one processor of the machine-readable symbol reader may optionally turn on one or more general illumination sources (e.g., flood illumination) to illuminate the environment within the FOV of the machine-readable symbol reader.

[0114] Optionally, at 634, the image sensor obtains an image using the set image sensor configuration and the optimized focus position. For example, the image may represent one or more machine-readable symbols in the field of view of the machine-readable symbol.

[0115] Optionally, at 636, at least one processor decodes machine-readable symbols represented in the captured image. Conventional machine-readable symbol decoding techniques can be employed.

[0116] Method 600 can terminate at 638, for example until called again. Alternatively, method 600 can be continuously repeated. In some embodiments, method 600 can be executed by multiple threads, such as via a multi-threaded processor. In at least some embodiments, where the machine-readable symbol reader includes one or more shutter image sensors (also known as shutter cameras) and one or more event-based image sensors (also known as event-based cameras), the image information captured by the one or more shutter image sensors can be used to implement actions 628 to 636.

[0117] Although method 600 is illustrated and described as a series of ordered actions or operations, in some embodiments, the method can omit some actions or operations, include other actions or operations, and / or can execute some actions or operations in an order different from the order shown. For example, choosing to start with near focus is just an option, and the opposite option can be executed, starting with far focus instead of near focus. Thus, in some embodiments, the direction of focusing can be opposite to that described in method 600, moving in the direction of far focus and then in the direction of near focus. In some embodiments, for example when a timeout and end condition occur, or if the scene changes or the scene brightness changes by more than a set brightness change threshold, the passive autofocus sequence of method 600 can be restarted.

[0118] Figure 7A -7F shows some example image information representations of the field of view generated by the event-based image sensor during the operation of method 600 ( Figure 6A and Figure 6B ). As previously described, event-based image sensors typically output data including or specifying the coordinates of pixels where the incident light intensity has changed. Thus, the image information can indicate pixels with an increasing intensity value having a first value (e.g., a boolean value 0) and pixels with a decreasing intensity value having a second value (e.g., a boolean value 1), with pixels having a consistent intensity value omitted. In at least some embodiments, the event-based image sensor can have a specific threshold to determine whether the increase and / or decrease in intensity is sufficient to trigger an output. Such image information can be reconstructed into a two-dimensional (2D) representation or digital image. In these examples, a first grayscale value indicates that the corresponding pixel has no activity, a second grayscale value indicates an increase in the brightness of the corresponding pixel, and a third grayscale value indicates a decrease in the brightness of the corresponding pixel. From Figure 7A-7F It can be seen that the aiming pointer (e.g., the laser aiming spot) is very easy to handle in terms of positioning and tracking, and the change in the size of the characteristic dimension of the aiming pointer (e.g., the diameter of the aiming spot) is also easy to detect.

[0119] In particular, Figure 7A A graphical representation of image information of a field of view 700a generated by an event-based image sensor according to one illustrated embodiment is shown. The field of view 700a encompasses an aiming pointer in the form of a laser spot 702a, which is generated on a target object 704 by an illumination source (e.g., a laser) of an aiming subsystem (e.g., the aiming subsystem of a machine-readable symbol reader).

[0120] Figure 7B A graphical representation of image information of a field of view 700b generated by an event-based image sensor according to one illustrated embodiment is shown, but the aiming pointer in the form of a laser spot 702b is relative to Figure 7A changing from ON to OFF, and the illumination source of the aiming subsystem is switched to the OFF state. Changing to OFF indicates a decrease in the intensity value of the pixel representing the aiming pointer, and thus a decrease in the output of the corresponding pixel. Figure 7A which represents a decrease in the intensity value of the pixel representing the aiming pointer, and thus a decrease in the output of the corresponding pixel.

[0121] Figure 7C A graphical representation of image information of a field of view 700c generated by an event-based image sensor according to one illustrated embodiment is shown. The field of view 700c includes an aiming pointer in the form of a laser spot 702c, which is generated on a target object 704 by an illumination source (e.g., a laser) of the aiming subsystem at a first focal length. The laser spot 702c has a characteristic dimension of a first size (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis). The relative change in intensity is indicated by the color of the pixels in the graphical representation, which can also be represented numerically by a Boolean value or a possible non-Boolean value. Whether the focusing is improved is indicated by whether the size of the set of pixels representing the laser spot 702c is decreasing or increasing and / or whether the measure of edge sharpness is increasing or decreasing.

[0122] Figure 7DA graphical representation of image information representing a field of view 700d generated by an event-based image sensor according to one illustrated embodiment is shown. The field of view 700d includes a sighting pointer in the form of a laser spot 702d that is generated by an illumination source (e.g., a laser) of a sighting subsystem on a target object 704 at a second focal length. The laser spot 702d has a characteristic dimension of a second size (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis), and the second size is smaller than the first size. The relative change in intensity is indicated by the color of the pixels in the graphical representation, which can also be represented numerically by a Boolean value or a possible non-Boolean value. Whether the focus is improved is indicated by whether the size of the set of pixels representing the laser spot 702d is decreasing or increasing and / or whether the measure of edge sharpness is increasing or decreasing.

[0123] Figure 7E A graphical representation of image information representing a field of view 700e generated by an event-based image sensor according to one illustrated embodiment is shown. The field of view 700e includes a sighting pointer in the form of a laser spot 702e that is generated by an illumination source (e.g., a laser) of a sighting subsystem on a target object 704 at a third focal length. The laser spot 702e has a characteristic dimension of a third size (e.g., diameter, perimeter, area, diagonal, length of the major axis, length of the minor axis, ratio of the length of the major axis to the length of the minor axis, diagonal axis), and the third size is smaller than the second size. The relative change in intensity is indicated by the color of the pixels in the graphical representation, which can also be represented numerically by a Boolean value or a possible non-Boolean value. Whether the focus is improved is indicated by whether the size of the set of pixels representing the laser spot 702e is decreasing or increasing and / or whether the measure of edge sharpness is increasing or decreasing.

[0124] A method similar to method 600( Figure 6A and Figure 6B ) and / or even method 500 (Figure 5) can be used not only with event-based image sensors but also when using image sensors and image processing systems that can generate outputs similar to those of event-based image sensors.

[0125] For example, a system with a more conventional global shutter sensor can be combined with an image processing system that only outputs pixels with value changes to mimic an event-based image sensor. In this case, the responsiveness or "flexibility" of passive autofocus will be limited by the sensor frame rate, but the advantages of efficient processing and computational speed are still maintained. A method for achieving this is described below with reference to Figure 8 describe a method for achieving this.

[0126] Figure 8Method 800 for operating an image acquisition system described for a machine-readable symbol reader that can be used to implement passive autofocus is shown. Method 800 can be performed by an image acquisition system (e.g., a machine-readable symbol reader such as Figure 1 and Figure 2 machine-readable symbol readers 100, 200), and in particular can employ a shutter image sensor, such as a global or rolling shutter image sensor 300a ( Figure 3A ). For example, system 800 can be employed in conjunction with some or all of the actions or operations of method 500 (Figure 5).

[0127] As previously described, a machine-readable symbol reader can include a sighting subsystem operable to project a sighting beam outside the machine-readable symbol reader to produce a sighting pointer, optics with adjustable focus, whose field of view extends outside the machine-readable symbol reader via the optics and is operable to capture an image or image information of at least one image sensor that appears in a field of view (FOV) including the sighting pointer and the machine-readable symbol. The machine-readable symbol reader can also include at least one processor that performs passive autofocus, configures the machine-readable symbol reader to capture image information from a machine-readable symbol that appears in the field of view and optionally decodes the captured machine-readable symbol.

[0128] Method 800 begins at 802, for example, when a user picks up the machine-readable symbol reader to scan a machine-readable symbol (e.g., a 1D or 2D barcode, alphanumeric characters) placed on a target object or item (e.g., clothing, packaging, circuit board), or when a trigger is actuated, or when the target object or item is otherwise presented to the machine-readable symbol reader.

[0129] At 804, at least one processor of the machine-readable symbol reader exposes the image sensor, e.g., by opening and then closing the shutter or by sampling or reading out all pixels or a subset of pixels of the image sensor.

[0130] At 806, at least one processor of the machine-readable symbol reader causes a first set of image information (e.g., a first image) captured by the image sensor to be read out and / or stored in one or more non-transitory storage media (e.g., a memory, such as random access memory (RAM)).

[0131] Then, method 800 enters an iterative loop 808 to capture and process image pairs. The iterative loop includes four actions or operations: 810, 812, 814, and 816, as described below. Iterative loop 808 can be repeated until sufficient images have been captured, e.g., images at each focus position or focus position step.

[0132] At 810 , at least one processor of the machine-readable symbol reader then re-exposes the image sensor, such as by opening and then closing a shutter or by sampling or reading out all or a subset of the pixels of the image sensor.

[0133] At 812, at least one processor of the machine-readable symbol reader causes a second set of image information (e.g., a new or next image) captured by the image sensor to be read out and / or stored to one or more non-transitory storage media (e.g., memory, such as random access memory (RAM)).

[0134] At 814, at least one processor of the machine-readable symbol reader compares the set of image information for the new or next image to the set of image information for the previous image, thereby identifying differences (e.g., changes in pixel intensity levels in the set of image information for the new or next image compared to the set of image information for the previous image).

[0135] At 816, at least one processor of the machine-readable symbol reader generates an output that represents only pixels that have differences or changes (e.g., changes in pixel intensity levels in a set of image information for a new or next image compared to a set of image information for a previous image). The at least one processor may employ a specified threshold for determining whether the change in intensity or illumination level is sufficient to constitute a difference.

[0136] At 818, at least one processor determines whether all focus positions or focus position steps have been processed. If not all focus positions or focus position steps have been processed, control may return to 810 to capture the next image and compare it to the most recently captured image. If all focus positions or focus position steps have been processed, control may proceed to 820.

[0137] Method 800 may terminate at 820, for example, until called again. Alternatively, method 800 may be repeated continuously. In some implementations, method 800 may be executed by multiple threads, for example, via a multi-threaded processor.

[0138] Although method 800 is illustrated and described as a series of ordered acts or operations, in some implementations, the method may omit some acts or operations, include other acts or operations, and / or may perform some acts or operations in an order different from that shown.

[0139] Figure 9A , Figure 9B and Figure 9C The method 800 ( Figure 8)The reconstructed images 900a, 900b, 900c calculated from the described differences, where the output includes only pixels and / or the coordinates of those pixels having differences in intensity or luminance or having differences in intensity or luminance exceeding a specified change threshold. In a more classical method, the output can constitute an image or image information of the difference between two successive images. As can be seen from Figure 9A , Figure 9B and Figure 9C , the dimensions of the characteristic dimensions (e.g., perimeter) of the sighting device pointers (e.g., sighting device laser spots) 902, 902c, 902c become smaller respectively from Figures 9A to 9B , become smaller from Figures 9B to 9C , and when the image sensor approaches optimal or at least optimized focus, its edges become thinner. When out of focus, the effect is opposite and can be easily discerned using image processing techniques.

[0140] The various embodiments described above can be combined to provide other embodiments. All commonly assigned U.S. patent application publications, U.S. patent applications, foreign patents, and foreign patent applications mentioned in this specification and / or listed in the application data sheet are hereby incorporated by reference in their entirety, including but not limited to: U.S. patent application 17 / 118,374, published as US20220187459A1; U.S. patent 9,800,749B1; and U.S. patent application 17 / 534,797, published as US20220207353A1.

[0141] The foregoing detailed description has set forth various embodiments of the devices and / or processes by use of block diagrams, flowcharts, and examples. As long as such block diagrams, flowcharts, and examples contain one or more functions and / or operations, those skilled in the art will understand that each function and / or operation in such block diagrams, flowcharts, or examples can be implemented individually and / or collectively by a variety of hardware, software, firmware, or almost any combination thereof, any of which may be referred to herein as one or more processors. In one embodiment, the subject matter may be implemented via an application specific integrated circuit (ASIC). However, those skilled in the art will recognize that the embodiments disclosed herein, whether in whole or in part, can be equivalently implemented in standard integrated circuits, implemented as one or more computer programs running on one or more computer systems, microcontrollers, microprocessors, digital signal processors, graphics processing units, implemented as firmware, or implemented as almost any combination thereof, and designing the circuit system and / or writing the software and / or firmware code to implement one or more processors or controllers will be entirely within the skill of the ordinary artisan in the art.

[0142] Those skilled in the art will recognize that many of the methods or algorithms described herein may incorporate additional acts, some acts may be omitted, and / or acts may be performed in an order different from the specified order.

[0143] In addition, those skilled in the art will recognize that the mechanisms taught herein can be distributed in a variety of forms as a program product, and that illustrative embodiments are equally applicable regardless of the particular type of signal-bearing medium actually used to effect such distribution. Examples of signal-bearing media include, but are not limited to, the following: recordable-type media such as floppy disks, hard disk drives, CD ROMs, digital tapes, and computer memories.

[0144] The various embodiments described above can be combined to provide further embodiments. If necessary, aspects of the embodiments can be modified to incorporate the systems, circuits, and concepts of various patents, applications, and publications to provide further embodiments.

[0145] These and other changes can be made to the embodiments in light of the above detailed description. In general, in the following claims, the terms used should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be construed to include all possible embodiments and the full scope of equivalents to such claims. Accordingly, the claims are not limited by the present disclosure.

Claims

1. A method of operating an image acquisition system having a sighting subsystem, at least one image sensor, and at least one optical device, the method comprises: emitting a sighting beam from the sighting subsystem outside the image acquisition system to generate a sighting pointer in the field of view of the image acquisition system; for each of a plurality of focus settings, adjusting the focus of the at least one optical device according to the current focus setting among the plurality of focus settings; and capturing, via the at least one image sensor, image information representing one or more characteristics of the sighting pointer that returns to the image acquisition system; and determining, via at least one processor, at least one of the one or more characteristics of the sighting pointer at the current focus setting among the plurality of focus settings; identifying, at least in part based on the determined at least one of the one or more characteristics of the sighting pointer, one focus setting among the plurality of focus settings that results in optimized focusing of the sighting pointer; and configuring the image acquisition system, based on the one focus setting among the plurality of focus settings that is identified as resulting in optimized focusing of the sighting pointer, to at least one of the following: capture an image and process the captured image via the at least one processor.

2. The method according to claim 1, wherein, before identifying the one focus setting among the plurality of focus settings that results in optimized focusing of the sighting pointer, image information representing one or more characteristics of the sighting pointer is captured at the plurality of focus settings.

3. The method according to claim 1, wherein adjusting the settings of the at least one optical device according to the current focus setting for each of the plurality of focus settings comprises: iteratively, adjusting the focus of the at least one optical device to focus at the next focus setting among the plurality of focus settings in a first focusing direction; determining whether at least one dimension of the sighting pointer is decreasing or increasing; and when it is determined that the at least one dimension of the sighting pointer is decreasing, adjusting the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in the first focusing direction of the at least one optical device; iteratively, determining whether at least one dimension of the sighting pointer is decreasing or increasing; when it is determined that the at least one dimension of the sighting pointer is increasing, adjusting the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in a second focusing direction of the at least one optical device, the second focusing direction being opposite to the first focusing direction; iteratively, determining whether at least one dimension of the sighting pointer is decreasing or increasing; when it is determined that the at least one dimension of the sighting pointer is decreasing, continuing to adjust the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in the second focusing direction of the at least one optical device; determining whether at least one dimension of the sighting pointer is decreasing or increasing; and In response to determining that at least one dimension of the aiming pointer is not decreasing, stop adjusting to the next focusing setting among the plurality of focusing settings.

4. The method according to claim 3, wherein the at least one image sensor is an event camera, and determining whether at least one dimension of the aiming pointer is decreasing or increasing includes determining whether a characteristic dimension of the aiming pointer is decreasing or increasing based on the output of the event camera.

5. The method according to claim 1, wherein for each of the plurality of focusing settings, adjust the settings of at least one optical device according to the current focusing setting including: Iteratively, Adjust the focus of the at least one optical device to focus at the next focusing setting among the plurality of focusing settings in a first focusing direction; Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; and When it is determined that the edge sharpness of the aiming pointer is increasing, adjust the focus of the at least one optical device according to the next focusing setting among the plurality of focusing settings in the first focusing direction of the at least one optical device; Iteratively, Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; When it is determined that the edge sharpness of the aiming pointer is decreasing, adjust the focus of the at least one optical device according to the next focusing setting among the plurality of focusing settings in a second focusing direction of the at least one optical device, the second focusing direction being opposite to the first focusing direction; Iteratively, Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; When it is determined that the edge sharpness of the aiming pointer is increasing, continue to adjust the focus of the at least one optical device according to the next focusing setting among the plurality of focusing settings in the second focusing direction of the at least one optical device; Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; and In response to determining that the edge sharpness of the aiming pointer is not increasing, stop adjusting to the next focusing setting among the plurality of focusing settings.

6. The method according to any one of claims 1 to 5, wherein the at least one image sensor is a global shutter sensor, and further includes: Store a plurality of successively captured images of the aiming pointer; Determine one or more differences between at least two successively captured images of the aiming pointer; and Generate pixel difference data representing the determined one or more differences between at least two successively captured images of the aiming pointer.

7. The method according to any one of claims 1 to 6, wherein capturing image information representing one or more characteristics of the aiming pointer includes capturing image information only for a defined region of interest corresponding to a subset of pixels of the at least one image sensor.

8. The method according to any one of claims 1 to 6, wherein emitting a sight beam outside the image acquisition system to generate a sight pointer in the field of view of the image acquisition system includes emitting a laser or LED sight beam outside the image acquisition system to generate at least one of a laser spot sight pointer, a laser two-dimensional pattern sight pointer, an LED spot sight pointer, or an LED two-dimensional pattern sight pointer in the field of view of the image acquisition system.

9. The method according to any one of claims 1 to 6, further comprising: Before capturing image information representing one or more characteristics of the sight pointer, setting at least one of an exposure time or an analog gain for the at least one image sensor based on one or more characteristics of the sight subsystem or one or more characteristics of the target to be illuminated.

10. The method according to any one of claims 1 to 6, further comprising: Before capturing image information representing one or more characteristics of the sight pointer, setting a region of interest for the at least one image sensor based on one or more characteristics of the sight subsystem.

11. The method according to any one of claims 1 to 6, further comprising: Determining the plurality of focusing settings before adjusting the focus of the at least one optical device.

12. The method according to any one of claims 1 to 6, further comprising: Processing each of the plurality of captured images of the sight pointer at a corresponding focusing setting of the plurality of focusing settings to determine the corresponding one or more characteristics of the sight pointer in each captured image; and wherein identifying the one focusing setting of the plurality of focusing settings that results in optimized focusing of the sight pointer is at least partially based on comparing the determined one or more characteristics of the sight pointer in the corresponding captured images.

13. The method according to any one of claims 1 to 6, wherein the image acquisition system includes a global shutter image sensor and an event-based image sensor, and further comprising: Using the image information captured by the event-based image sensor to identify the one focusing setting of the plurality of focusing settings that results in optimized focusing of the sight pointer, and using the image information captured by the global shutter image sensor to adjust the focus based on the one focusing setting identified from the plurality of focusing settings that results in optimized focusing of the sight pointer, thereby acquiring an image for decoding.

14. An image acquisition system, comprising: A sight subsystem operable to emit a sight beam outside the image acquisition system to generate a sight pointer in the field of view of the image acquisition system, At least one image sensor that captures image information representing one or more characteristics of the sight pointer returned to the image acquisition system and image information representing a target in the field of view of the image acquisition system, At least one optical device; and A control system including at least one processor, the control system being operable to: For each of the plurality of focusing settings, Adjust the focus of the at least one optical device according to the current focusing setting of the plurality of focusing settings; And Determine at least one of the one or more characteristics of the aiming pointer at the current focus setting among the plurality of focus settings; Identify, at least in part based on the determined at least one of the one or more characteristics of the aiming pointer, one focus setting among the plurality of focus settings that results in an optimized focus of the aiming pointer; And Configure the image acquisition system based on the one focus setting among the plurality of focus settings that is identified as resulting in an optimized focus of the aiming pointer to at least one of the following: capture an image and process the captured image by the at least one processor.

15. The image acquisition system according to claim 14, wherein prior to identifying the one focus setting among the plurality of focus settings that results in an optimized focus of the aiming pointer, capture image information representing one or more characteristics of the aiming pointer under the plurality of focus settings and only for a defined region of interest.

16. The image acquisition system according to claim 14, wherein in order to adjust the settings of at least one optical device according to the current focus setting for each of the plurality of focus settings, the at least one processor: Iteratively, Adjust the focus of the at least one optical device to focus at the next focus setting among the plurality of focus settings in a first focusing direction; Determine whether at least one dimension of the aiming pointer is decreasing or increasing; And When it is determined that the at least one dimension of the aiming pointer is decreasing, adjust the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in the first focusing direction of the at least one optical device; Iteratively, Determine whether at least one dimension of the aiming pointer is decreasing or increasing; When it is determined that the at least one dimension of the aiming pointer is increasing, adjust the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in a second focusing direction of the at least one optical device, the second focusing direction being opposite to the first focusing direction; Iteratively, Determine whether at least one dimension of the aiming pointer is decreasing or increasing; When it is determined that the at least one dimension of the aiming pointer is decreasing, continue to adjust the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in the second focusing direction of the at least one optical device; Determine whether at least one dimension of the aiming pointer is decreasing or increasing; In response to determining that the at least one dimension of the aiming pointer is not decreasing, stop any adjustment to the next focus setting among the plurality of focus settings.

17. The image acquisition system according to claim 16, wherein the at least one image sensor is an event camera, and in order to determine whether at least one dimension of the aiming pointer is decreasing or increasing, the at least one processor determines whether the characteristic dimension of the aiming pointer is decreasing or increasing based on the output of the event camera.

18. The image acquisition system according to claim 14, wherein, in order to adjust the settings of at least one optical device according to the current focus setting for each of a plurality of focus settings, the at least one processor: Iteratively, Adjust the focus of the at least one optical device to focus at the next focus setting among the plurality of focus settings in a first focusing direction; Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; And When it is determined that the edge sharpness of the aiming pointer is increasing, adjust the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in the first focusing direction of the at least one optical device; Iteratively, Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; When it is determined that the edge sharpness of the aiming pointer is decreasing, adjust the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in a second focusing direction of the at least one optical device, the second focusing direction being opposite to the first focusing direction; Iteratively, Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; When it is determined that the edge sharpness of the aiming pointer is increasing, continue to adjust the focus of the at least one optical device according to the next focus setting among the plurality of focus settings in the second focusing direction of the at least one optical device; Determine whether the edge sharpness of the aiming pointer is decreasing or increasing; In response to determining that the edge sharpness of the aiming pointer is not increasing, stop any adjustment of the next focus setting among the plurality of focus settings.

19. The image acquisition system according to any one of claims 14 to 18, wherein the at least one image sensor is a global shutter sensor, and the at least one processor further: Cause a plurality of successively captured images of the aiming pointer to be stored; Determine one or more differences between at least two successively captured images of the aiming pointer; and Generate pixel difference data representing the determined one or more differences between at least two successively captured images of the aiming pointer.

20. The image acquisition system according to any one of claims 14 to 18, wherein the image acquisition system includes a global shutter image sensor and an event-based image sensor, and the at least one processor further: uses image information captured by the event-based image sensor to identify the one focus setting among the plurality of focus settings that results in optimized focusing of the aiming pointer, and uses the image information acquired by the global shutter image sensor to adjust the focus based on the one focus setting among the plurality of focus settings that is identified as resulting in optimized focusing of the aiming pointer, so as to acquire an image for decoding.

Images