Systems and methods for light pulse detection

Abstract

Systems and methods for detecting a timing interval in which a light pulse is received by a photodetector array comprising: receiving, by a plurality of photosensitive elements of the photodetector array, electromagnetic radiation from a field of view, accumulating, by each of the plurality of photosensitive elements, an electrical charge proportional to an intensity of received electromagnetic radiation during an integration time period, and performing a search on signals converted from the accumulated electrical charge to detect a light pulse appearance with a predefined precision. Performing the search may include performing a fine search stage including: controlling the duration of the integration time period for each of the plurality of photosensitive elements and a temporal relationship between the integration time periods of the photosensitive elements. The temporal relationship between the integration time periods of the photosensitive elements may define a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period. Detecting a timing interval in which a light pulse is received from the field of view by identifying the distinct temporal pattern corresponding to that timing interval.

Description

[0001] SYSTEMS AND METHODS FOR LIGHT PULSE DETECTION

[0002] FIELD

[0003] Subject matter disclosed herein relates to systems and methods for light pulse detection by a photodetector array.

[0004] BACKGROUND

[0005] Light-based sources may be used to generate illumination pulses, spots or beacons that operate with defined repetition times or modulation frequencies for various purposes such as target designation, tracking, identification, or alignment. Such sources, for example laser designators may include pulsed or coded laser beacons, infrared (IR) strobes, optical transponders, and active retroreflective markers. These light sources may emit radiation at visible or non-visible wavelengths, for example within the near-infrared or infrared spectrums and may be modulated according to predefined temporal patterns. The modulation may be periodic or coded, for example at frequencies ranging from a few hertz to several kilohertz, such as 10 Hz, 20 Hz, 100 Hz, or 1 kHz, depending on operational requirements. In certain systems, including NATO-standard laser designation and identification protocols, coded pulse sequences (often referred to as PRF codes or pulse repetition frequencies) may be used to distinguish between multiple simultaneous designations or to identify a specific friendly source. Other systems such as security, medicine, communication, civil or industrial systems may use optical beacons with unique timing signatures to enable autonomous localization, calibration, target designation, tracking, alignment, navigation, and / or synchronization between imaging and control systems.

[0006] Conventional imaging systems are primarily designed to capture passive light from the environment and therefore may not reliably recognize or distinguish artificially generated light spots, particularly when such spots are small, transient, or spectrally similar to background illumination. Accordingly, there exists a need for imaging systems and associated processing methods that can accurately detect, locate, and identify active light-based sources with a predefined precision. SUMMARY OF THE INEVNTION

[0007] Some embodiments of the disclosure may include a method for detecting a timing interval in which a light pulse is received by a photodetector array. The method may include receiving, by a plurality of photosensitive elements of the photodetector array, electromagnetic radiation from field of view, accumulating, by each of the plurality of photosensitive elements, an electrical charge proportional to an intensity of received electromagnetic radiation during an integration time period and performing a search on signals converted from the accumulated electrical charge to detect a light pulse appearance with a predefined precision.

[0008] According to some embodiments, performing the search may include performing a fine search stage including controlling the duration of the integration time period for each of the plurality of photosensitive elements and a temporal relationship between the integration time periods of the photosensitive elements.

[0009] According to some embodiments, the temporal relationship between the integration time periods of the photosensitive elements defines a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period.

[0010] According to some embodiments, the method may further include detecting a timing interval in which a light pulse is received from the field of view by identifying the distinct temporal pattern corresponding to that timing interval.

[0011] According to some embodiments, performing the fine search stage may include performing a plurality of iterations of the fine search stage, wherein in each of the plurality of iterations, the integration time period is reduced, such that each of the timing intervals within the integration time period is shortened until the light pulse appearance is detected with the predefined precision.

[0012] According to some embodiments, a plurality of distinct temporal patterns represent respective unique binary codes corresponding to timing intervals,

[0013] In some embodiments, detecting the timing interval in which the light pulse is received includes identifying a unique binary code corresponding to that timing interval.

[0014] According to some embodiments, performing the search further includes performing a first search stage, wherein the first search stage including scanning a sensor area to determine a spatial location of the light pulse and a timing of detection thereof with a first timing accuracy. According to some embodiments, scanning the sensor area may include sequentially scanning a plurality of sub-areas within the sensor area until a light pulse is detected within one of the sub-areas with the first timing accuracy.

[0015] According to some embodiments, the sequentially scanning of the plurality of the sub-areas includes iteratively scanning each of the sub-areas and iteratively scanning of each of the sub-areas is repeated for a predetermined duration of time or until a light pulse is detected.

[0016] According to some embodiments, the iteratively scanning each of the sub-areas may include dividing each of the sub-areas into a plurality of blocks, and simultaneously scanning the plurality of blocks, wherein at least one row of each of the plurality of blocks is exposed to light at any given time.

[0017] According to some embodiments, the size of each of the plurality of blocks is determined according to a spot size corresponding to the light pulse

[0018] According to some embodiments, the first search stage may further include scanning a selected search area around the spatial location of the light pulse until another light pulse is detected within the selected search area with a second timing accuracy.

[0019] Some embodiments of the disclosure may include a system for detecting a timing interval in which a light pulse is received, the system may include a photodetector array comprising a plurality of photosensitive elements configured to receive electromagnetic radiation from a field of view and to accumulate an electrical charge proportional to an intensity of the received electromagnetic radiation during an integration time period.

[0020] According to some embodiments, the system may further include a readout circuit configured to convert the accumulated electrical charge of each of the plurality of photosensitive elements into electrical signals.

[0021] According to some embodiments, the system may further include a processor configured to perform a search on the electrical signals to detect an appearance of a light pulse with a predefined precision, the search comprising a fine search stage in which the processor if further configured to control a duration of an integration time period for each of the plurality of photosensitive elements and a temporal relationship among the integration time periods of the photosensitive elements, wherein the temporal relationship among the integration time periods defines a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period. The processor is further configured to detect a timing interval in which the light pulse is received by identifying the distinct temporal pattern corresponding to that timing interval.

[0022] According to some embodiments, the processor is further configured to perform a plurality of iterations of the fine search stage, wherein in each of the plurality of iterations, the processor is to reduce an integration time period such that each of a plurality of timing intervals within the integration time period is shortened until an appearance of the light pulse is detected with the predefined precision.

[0023] According to some embodiments, the plurality of distinct temporal patterns represent respective unique binary codes corresponding to timing intervals, and wherein detecting the timing interval in which the light pulse is received comprises identifying a unique binary code corresponding to that timing interval.

[0024] According to some embodiments, the processor is further configured to perform a first search stage, and during the first search stage the processor is configured to scan a sensor area to determine a spatial location of the light pulse and a timing of detection thereof with a first timing accuracy.

[0025] According to some embodiments, the processor is configured to perform sequentially scanning a plurality of sub-areas within the sensor area until a light pulse is detected within one of the sub-areas with the first timing accuracy. The sequentially scanning of the plurality of the subareas comprises iteratively scanning each of the sub-areas.

[0026] According to some embodiments, the processor is configured to repeat the iteratively scanning each of the plurality of sub-areas for a predetermined duration of time or until a light pulse is detected.

[0027] According to some embodiments, during the iteratively scanning, the processor is configured to divide each of the plurality of sub-areas into a plurality of blocks; and simultaneously scan the plurality of blocks such that at least one row of each block is exposed to light at any given time. The size of each of the plurality of blocks is determined according to a spot size corresponding to the light pulse.

[0028] According to some embodiments, during the first search stage the processor is further configured to scan a selected search area around the spatial location of the light pulse until another light pulse is detected within the selected search area with a second timing accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Non-limiting embodiments disclosed herein are described below with reference to figures attached hereto that are listed following this paragraph, identical structures, elements or parts that appear in more than one figure are generally labeled with the same numeral in all the figures in which they appear. When similar reference numerals are shown, corresponding description(s) are not repeated, and the interested reader is referred to the previously discussed figure(s) for a description of the like element(s). The drawings and descriptions are meant to illuminate and clarify embodiments disclosed herein but should not be considered limiting in any way. In particular, variations and modifications apparent to those skilled in the art may be considered without departing from the claimed scope.

[0030] FIG. 1A illustrates an example configuration of a system for light spot detection in accordance with embodiments disclosed herein;

[0031] FIG. 1B-1C illustrates an exemplary arrangement of a pixel array in accordance with embodiments disclosed herein;

[0032] FIG. 2 is a block diagram of an imaging system for light spot detection in accordance with embodiments disclosed herein;

[0033] FIG. 3 shows a flowchart of process for light spot detection in accordance with embodiments disclosed herein;

[0034] FIGS. 4A-4B show an exemplary diagram of a first search stage used in methods for light spot detection in accordance with embodiments disclosed herein;

[0035] FIGS. 5A-5B illustrate a schematic representation of an exemplary first search stage on a visual image and a corresponding timing scheme in accordance with embodiments disclosed herein;

[0036] FIG. 6 shows an exemplary diagram of a second search stage used in methods for light spot detection in accordance with embodiments disclosed herein;

[0037] FIG. 7 illustrates a schematic representation of timing precision scheme after a first search stage and a second search stage in accordance with embodiments disclosed herein;

[0038] FIG. 8 shows an exemplary diagram of a fine search stage used in methods for light spot detection in accordance with embodiments disclosed herein; FIG. 9 shows exemplary timing diagrams illustrating the temporal relationship between integration time periods of a plurality of photosensitive elements in accordance with embodiments disclosed herein;

[0039] FIG. 10 is a table which shows exemplary timing results of a plurality of rounds of fine search stage used in methods for light spot detection in accordance with embodiments disclosed herein;

[0040] FIGS. 11A-11B which are tables showing exemplary values of segments codes in a plurality of implementations of fine search stage in accordance with embodiments disclosed herein;

[0041] FIG. 12 is a table showing exemplary timing results of a plurality of rounds of fine search stage used in methods for light spot detection in accordance with embodiments disclosed herein;

[0042] FIG. 13 shows illustrative visual results of methods for light spot detection in accordance with embodiments disclosed herein; and

[0043] FIG. 14 shows a flowchart of process for light spot detection in accordance with embodiments disclosed herein.

[0044] DETAILED DESCRIPTION

[0045] One skilled in the art will realize that the disclosure may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the disclosure described herein. Scope of the disclosure is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are, therefore, intended to be embraced therein.

[0046] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the disclosure. However, it will be understood by those skilled in the art that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present disclosure. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated. Although embodiments disclosed herein are not limited in this regard, discussions utilizing terms such as, for example, “processing,” “computing,” “calculating,” “determining,” “establishing”, “analyzing”, “checking”, or the like, may refer to operation(s) and / or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and / or transforms data represented as physical (e.g., electronic) quantities within the computer’s registers and / or memories into other data similarly represented as physical quantities within the computer’s registers and / or memories or other information non-transitory storage medium that may store instructions which when executed by a processor cause the processor to perform operations and / or processes.

[0047] Although embodiments disclosed herein are not limited in this regard, the terms “plurality” and “a plurality” as used herein may include, for example, “multiple” or “two or more”. The terms “plurality” or “a plurality” may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. The term “set” when used herein may include one or more items.

[0048] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

[0049] This disclosure describes systems and methods for detecting repetitive light signals by an imaging system and specifically by a photodetector array. The system may detect the spatial location of the light spot and identification of its frequency with a predefined precision while periodically outputting visual image frames. The detection may include operating the imaging sensor in various search modes dynamically, e.g., in real time, for identifying the location, frequency and the time of appearance of the light spot.

[0050] As used herein, the terms “light pulse” and “light spot” are used interchangeably to describe an incident illumination event detected by the imaging system, whether defined temporally as a pulse or spatially as a projected spot on the sensor array.

[0051] The terms “photodetecting device”, “sensor array”, “photodetecting array”, “photodetector array”, “pixel array”, “image / imaging sensor” or simply “sensor” refers to a semiconductor device comprising multitude of “photosites” also referred to herein as “pixels”, “sensor elements”, “photosensitive cells”, “photosensitive elements”, “photodetector elements” or “photodetector cells”. Each of the photodetector elements includes a light-sensitive region e.g., one or more photodiode, photogate, germanium (Ge) photodiode or any other photodiode that detect impinging light and converts light photons into charge carriers. Each “photosite” or “pixel” further includes capacitance for storing charge provided by the photodiode. The capacitance may be implemented as a dedicated capacitor and / or using parasitic capacitance of the photodiode, transistors, and / or other components of the pixel. The photodetecting array further includes one or more readout circuitry configured to accumulate, transfer, and / or digitize charge from the pixels to produce electrical signals and image data corresponding to the spatial distribution of light and / or to output the image data.

[0052] The term "scene" refers to herein as any portion of an environment or field of view (FOV) that is imaged or captured by an imaging system. The scene may include one or more objects, surfaces, features, or regions of interest, and may include static or dynamic elements. The scene may be illuminated naturally or artificially, and may be captured in whole or in part, in two or more dimensions, across one or more spectral bands, depending on the capabilities and configuration of the imaging system.

[0053] The terms “line” and “row” of photodetectors as used herein, may be used interchangeably and refer to a group or sequence of photodetector cells arranged along a common direction within the pixel array or sensor. The use of either term does not imply any specific physical or functional distinction, and both are intended to encompass any linear arrangement of photosensitive elements that may be read out sequentially or simultaneously.

[0054] The term “scanning” as used herein, when referring to scanning rows of a photodetector array, relates to the sequential or coordinated activation, exposure, and / or readout of the photosensitive rows included in the array. Scanning may involve initiating and controlling the integration period of one or more rows to collect light over a defined time interval, followed by transferring or reading out the accumulated charge or signal from those rows. This process may be repeated across multiple rows or groups of rows, either sequentially or simultaneously, to acquire image or detection data across the entire array or selected sub-areas thereof.

[0055] As used herein, the terms “exposure time”, “exposure period” or “exposure duration” refer to the duration during which one or more photosensitive cells of a photodetector array are exposed to incident light. The exposure time defines the active light collection window of the sensor and may correspond to or differ from the integration time depending on the sensor architecture, such as in rolling-shutter or global-shutter operation modes.

[0056] As used herein, the term “integration time” refers to the duration during which one or more photosensitive element of a photodetector array accumulates electrical charge in response to incident light. The integration time defines the effective light collection period for each pixel and may be controlled or varied by the system controller to adjust for example, timing precision.

[0057] In some embodiments of the disclosure the integration time and exposure time are substantially identical, as all pixels begin and end light collection simultaneously e.g., in embodiments employing a global-shutter operation. In some embodiments, the exposure time encompasses the sequential integration periods of multiple rows, such that each row begins and ends integration at a slightly different time. Consequently, while integration time defines the lightcollection duration per pixel, exposure time defines the total time during which the sensor is actively acquiring image data across the array, e.g., when a rolling-shutter operation is employed.

[0058] FIG. 1A illustrates an example configuration of a system for light spot detection in accordance with embodiments disclosed herein. Embodiments of this disclosure may include any light-based source configured to generate illumination pulses, spots, or beacons that operate with defined repetition times or modulation patterns, such as a laser designator. FIG. 1B-1C illustrates an exemplary arrangement of a pixel array in accordance with embodiments disclosed herein.

[0059] FIGS. 1A-1C illustrate an exemplary embodiment using a laser designator, however, any suitable light-emitting device configured to project or direct optical radiation, including but not limited to light-emitting diodes (EEDs), laser diodes, lamps, or other artificial or natural illumination sources may alternatively be employed, and the term “laser” is used herein solely for illustrative purposes.

[0060] A light source 110, e.g., a laser designator may be configured to emit a light signal 112, e.g., a laser beam toward a certain point, surface, target or object, such as wall 114. The emitted light signal 112 may produce a localized illuminated region or light spot 111 on a surface of an object or a target, e.g., wall 114. An imaging system 100, which may include at least one or more optical elements, and a photodetecting device such as a photodetecting array, also referred to herein as an “imaging sensor”. Imaging system 100 may be oriented such that its field of view (FOV) 113 encompasses wall 114 and light spot 111. Imaging system 100 may include a plurality of photodetectors elements, each of the plurality of photosensitive elements of the photodetector array may receive electromagnetic radiation from field of view FOV 113. Each of the plurality of photosensitive elements may accumulate an electrical charge proportional to an intensity of received electromagnetic radiation during an integration time period and may perform a search on signals converted from the accumulated electrical charge to detect a light pulse appearance with a predefined precision, e.g., light spot 111. Imaging system 100 may further determine the spatial location of light spot 111 and detect its temporal repetition rate or frequency with a predetermined accuracy, precision or resolution as described in embodiments of the disclosure. In certain embodiments, the position of light spot 111 may be used for alignment, range finding, target designation, or calibration of the imaging system.

[0061] FIG. IB illustrates an exemplary arrangement of a pixel array or photodetector array in accordance with embodiments disclosed herein. Pixel array or sensor 120 may be included in imaging system 100 and may include a plurality of photosensitive cells or photodetector elements arranged along two dimensions, forming a grid of N pixels by M pixels. In this context, the term ‘pixel’ refers to an individual photodetector cell or photosensitive element of the imaging sensor which may correspond to a digital pixel in an output image frame. Each photosensitive element is configured to receive or detect incident electromagnetic radiation received from FOV 113, e.g., from a corresponding region of a scene within the FOV of the imaging system. Photodetector array 120 may be sensitive to one or more wavelength ranges and may receive electromagnetic radiation and accumulate charge proportional to the intensity of the received electromagnetic radiation during an integration time period. Photodetector array 120 may further convert the accumulated charge and generate an electrical signal proportional to the received electromagnetic radiation at each photodetector cell.

[0062] As illustrated in FIG. IB, and in accordance with the configuration shown in FIG. 1A, an illuminated region 121 of the pixel array receives light from a projected spot 111, resulting in a cluster or localized spot 122 on photodetector elements responding to increased illumination intensity. Pixel array 120 may have a resolution of NxM pixels, where N represents the number of pixels along a first dimension, for example the horizontal axis 125, and M represents the number of pixels along a second dimension, for example the vertical axis 126. In some embodiments, N and M may be for example, 640x480, 1920x1080, 1280x960 pixels, respectively. Any other image size may be applicable. The position of this illuminated region 121 may be defined in terms of its pixel coordinates along the first dimension 125 (N pixels, e.g., horizontal) and the second dimension 126 (M pixels, e.g., vertical). The localized spot 122 may extend across approximately X by Y photodetector cells (for example, 5x5 pixels), indicating the spatial distribution of the incident light across the sensor surface. Any other number of photodetector cells may be included in the area occupied by light spot 122. The depiction in FIG. IB is schematic and intended for illustrative purposes. The specific numerical values provided herein, including resolution, spot dimensions, array dimensions and the like, are exemplary only and may vary based on the configuration of imaging system 100, sensor type, optical design, scene geometry or any other parameter.

[0063] According to embodiments of the disclosure, light spot 111 may be emitted in a pulsed or modulated manner, having a predetermined frequency or duty cycle that distinguishes it from other light sources or background reflections. For example, the modulation frequency may be in the range of about 5 Hz to 100 Hz, such as approximately 10 Hz, 20 Hz, or 50 Hz. In certain embodiments, the light, e.g., laser may be configured to remain on for a defined duration, such as a few milliseconds to 1 second, and then off for a similar or different time interval, thereby generating a periodic appearance and disappearance of the spot in the image sequence. Embodiment of the invention may include detection of such periodic behavior in order to confirm identification of the light spot, for example, to ensure correspondence to the designated target.

[0064] Imaging system 100 of FIG.1A may detect, identify, or recognize light spots spatial coordinates and frequency as described in embodiments of the disclosure. In some embodiments, the light appearance frequency or the range of modulation frequencies applicable for a particular light transmission may be predetermined or known. For example, the optical signal may be modulated or pulsed at frequencies ranging from a few hertz (Hz) to several megahertz (MHz), depending on operational requirements and system configuration. Exemplary modulation frequencies may include, but are not limited to, 1 Hz, 10 Hz, 20 Hz, 100 Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz, or higher. In certain embodiments, light appearance frequency may be predetermined for certain applications and light pulses at a pulse repetition frequency (PRF) may conform to PRF code settings of certain standards or applications, for example, NATO-standard protocols. The modulation frequencies may be selected from standardized PRFs, such as 10 Hz, 20 Hz, 30 Hz, 40 Hz, 50 Hz, or ranges of PRFs, e.g., 8 to 20 Hz, 5 to 10 Hz 8 to 22 Hz. Any other defined PRF values or range may be used used for coded target marking, tracking, or any other purpose. FIG. 1C illustrates an exemplary partial view of sensor array in accordance with embodiments disclosed herein. The exemplary partial view of sensor array 120 represented as a pixel map 131, showing a two-dimensional distribution of light intensity values corresponding to spot of light 122, in accordance with the configuration shown in FIGS. 1A-1B. Pixel map 131 represents a sub-region of the photodetector array, wherein each cell corresponds to an individual photosensitive pixel of sensor 120. The numerical values within each cell denote measured or computed light intensity levels, expressed in arbitrary or normalized units.

[0065] As shown, the highest intensity values occur at the central region 132 of light spot 122 and gradually decrease toward outer pixels 134 (of light spot 122), thereby illustrating the spatial intensity profile of the light spot 122 as detected by sensor array 120. In this embodiment, light spot 122 impinges upon approximately five adjacent pixels in each direction, e.g., about five pixels by five pixels shown by element 133, defining the localized region of elevated intensity within the pixel array.

[0066] However, since spot of light 122 does not precisely align with the pixel boundaries of sensor 120, it may be detected across multiple adjacent pixels, including those whose active areas fall partially within the illuminated region. Accordingly, the detection of the light spot may occur during the integration time of the sensor rows encompassed by element 136, representing the pixels that collectively receive partial or full illumination from the incident light spot.

[0067] It should be appreciated that FIG. 1C presents only a partial view of sensor array 120 and is provided for explanatory purposes. The specific numerical values, contour spacing, and pixel dimensions shown are exemplary and non-limiting, variations may occur depending on illumination wavelength, optical focus, sensor design, or exposure parameters of imaging system 100.

[0068] FIG. 2 is a block diagram of an imaging system for light spot detection in accordance with embodiments disclosed herein. Imaging system 100 is configured to detect light, also referred herein as “optical signal” or “electromagnetic radiation”, reaching imaging system 100 from its FOV 113, e.g., reflected from a target, object or other article within FOV 113. Imaging system 100 may include an imaging receiver 110 and may further include one or more functional components such as a controller 150, an image processor 140, a readout circuitry 160, a display 170, a memory 180, and a communication module 190 all of which may be connected via one or more data bus 195. It should be understood that, although shown as discrete blocks or modules for clarity of illustration, any or all of these components may be implemented as part of, or integrated within, the imaging receiver 110. For example, the controller 150 and image processor 140 may share processing resources or be implemented on a common hardware platform, such as a digital signal processor (DSP), field-programmable gate array (FPGA), or system-on-chip (SoC). Similarly, the readout circuitry 160, memory 180, and communication module 190 may be physically or functionally incorporated into the imaging receiver to enable compact integration, enhanced performance, and reduced latency in data acquisition and processing. In some embodiments, such integration allows efficient coordination between light detection, image formation, data storage, and transmission operations within imaging receiver 110.

[0069] Imaging receiver 110, or simply receiver 110, may include any suitable type of image sensor or photodetector array 120 and optics 130. Image sensor or simply “sensor” 120 may include a plurality of photosensitive cells, photosites or pixels, collectively referred to herein as “photosensitive pixel array” or “pixel array” 120. The photosensitive cells may be arranged as an array, e.g., a two-dimensional array of photosensitive cells. The sensor may include, for example, a short-wave infrared (SWIR) photodetector array, a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS) sensor that converts visible or non-visible electromagnetic radiation into signals and / or image. Each photosite may include one or more photodiodes for electromagnetic radiation from a FOV and capacitance for accumulating and storing charge generated by the photodiode which may be proportional to the intensity of the received electromagnetic radiation. The time interval during which the pixels of the sensor array collect and accumulate charge provided by the photodiode in response to light or received electromagnetic radiation may referred to herein as “integration time” or an “integration time period”.

[0070] Optics 130 included in imaging receiver 110 may include one or more optical elements or assembly of optical components, referred to herein as “optics”. Optics 130 may be configured to manipulate, direct, transmit, reflect, refract, focus, disperse, or otherwise affect electromagnetic radiation (e.g., light) within receiver 110. Optics 130 may be utilized by receiver 110 and may include, but is not limited to one or more, lenses, mirrors, prisms, beam splitters, filters, apertures, waveguides, diffractive elements, or optical fibers or any other element to improve, enhance and / or support receiver 110 and / or sensor 120. According to some embodiments of the present disclosure, the imaging system may include readout circuitry 160 operatively coupled to the photodetector array 120. Readout circuitry 160 may be configured to transfer, amplify, and process the electrical charge accumulated by each photosensitive element during the integration period. In operation, following completion of each integration cycle, the readout circuitry 160 converts the stored or accumulated electrical charge into a corresponding voltage or current signal suitable for further analog or digital processing.

[0071] The circuitry may include one or more analog front-end components, such as charge-to- voltage converters, source followers, correlated double sampling (CDS) circuits, or analog-to- digital converters (ADCs). In some embodiments, readout circuitry 160 may be arranged to sequentially or simultaneously read data from multiple pixels, depending on whether the imaging receiver operates in a rolling shutter or global shutter mode. Readout circuitry 160 may further include multiplexers, timing control logic, and noise reduction elements configured to preserve signal integrity and dynamic range. The output of readout circuitry 160 may be provided to image processor 140 or directly to controller 150 for subsequent image reconstruction, light spot detection, or temporal analysis.

[0072] Although readout circuitry 160 is illustrated as a discrete block external to the imaging receiver 110 for clarity of explanation, it should be understood that, in other embodiments, the readout circuitry may be physically or functionally integrated within the imaging receiver 110 or within sensor 120. Such integration may facilitate compact system design, reduce interconnect noise, and enhance synchronization between the sensor and downstream processing circuitry.

[0073] Controller 150 may refer to any component, module, circuitry, processor, or set of executable instructions configured to manage, regulate, or coordinate one or more operations of imaging system 100. Controller 150 may interface with one or more subsystems of imaging system 100 to enable coordinated operation and dynamic adjustment in response to system requirements or external conditions. For example, controller 150 may be configured to control the operation of one or more of the other components of imaging system 100 e.g., imaging receiver 110, sensor 120, processor 140, readout circuitry 160, display 170, memory 180, and communication module 190.

[0074] Controller 150 may be configured to control activation and / or deactivation of imaging sensor 120. For example, controller 150 may regulate the duration during which receiver 120 collects and accumulates incoming light or signal, such duration being referred to herein as “integration time”. In some embodiments, controller 150 may operate receiver 110 for predetermined integration times, for example, to limit or to reduce the effect of noise accumulation, e.g., dark signal noise, on signal quality. In some embodiments, controller 150 may control the duration of the integration time period of each of the photosensitive elements of sensor 120 and the temporal relationship between the integration time period of each of the photosensitive elements. Controller may further perform operation to allow a search on signals converted from the accumulated electrical charge and to detect a light pulse appearance with a predefined precision.

[0075] In some embodiments, controller 150 may be further configured to control operations of optics 130, including, but is not limited to, adjustment of focus, zoom level, aperture size, lens position, optical filtering, light modulation, or alignment of optical paths. Controller 150 may operate in response to predefined parameters, sensor feedback, user input, or automated algorithms for spot detection, scene optimization, image quality enhancement, target tracking, or environmental adaptation. Controller 150 may be implemented in hardware, software, firmware, or any combination thereof, and may be realized as a centralized processor or distributed across multiple processing units.

[0076] Processor 140 also referred to herein as “image processor” may control along with controller 150 the operation of one or more components of imaging system 100 for example, imaging receiver 110, sensor 120, processor 140, readout circuitry 160, display 170, memory 180, and communication module 190. Processor 140 may be connected to controller 150 to allow control operation of imaging receiver 110 and processing of signals, data or information received from sensor 120.

[0077] It should be understood that the operations, functions, and control actions described herein with reference to processor 140 and controller 150 may, in certain embodiments, be performed by a single processing unit, module, or processor. Accordingly, any reference to actions performed by the controller 150 and / or processor 140 may equivalently refer to actions performed by a processor configured to execute such operations, whether implemented as separate physical components, integrated circuitry, or as part of a common processing architecture

[0078] Processor 140 may receive the electrical signals produced in response to electromagnetic radiation detected by sensor 120, the signals being representative of imagery of the illuminated scene within FOV 103. Processor 140 may further process the electrical signals produced in response to electromagnetic radiation by imaging receiver 110 to detect timing interval in which a light pulse is received by sensor 120. Processor 140 and / or controller 150 may be configured to perform a search on the electrical signals to detect an appearance of a light pulse with a predefined precision. The search may include a plurality of search stages as described in embodiments of the disclosure.

[0079] According to some embodiments processor 140 and / or controller 150 may be configured to control a duration of an integration time period for each of the plurality of photosensitive elements and a temporal relationship among the integration time periods of the photosensitive elements, wherein the temporal relationship among the integration time periods defines a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period, processor 140 and / or controller 150 may be configured to detect a timing interval in which the light pulse is received by identifying the distinct temporal pattern corresponding to that timing interval.

[0080] In some embodiments, processor 140 may be implemented as one or more internal processors inside imaging system 100 while in some embodiments, processor 40 may be an external processor, e.g., external to imaging system 100. In some embodiments, processing of the output of receiver 110 may be performed by processor 114 and additionally or alternatively by an external processor (not shown). Processor 140 and / or controller 150 may be any suitable processing device e.g., a processor core, a microprocessor, an ASIC, an FPGA, a controller, a microcontroller, and the like. Processor 140 and / or controller 150 may be one processor or a plurality of processors that are operatively connected. Processor 140 and / or controller 150 may include or may be connected to at least one memory module 180 or any non-transitory computer-readable storage media, such as RAM, ROM, EEPROM, EPROM, flash memory devices, magnetic disks, etc., and combinations thereof.

[0081] Memory module 180 may store data such as detection information generated by processor 140 by processing the detection signals. Memory 180 may further store instructions which may be executed by processor 140 and / or controller 150 and may processor 140 and / or controller 150 to perform operations including but not limited to: perform a search on the electrical signals to detect an appearance of a light pulse with a predefined precision, control a duration of an integration time period for each of the plurality of photosensitive elements and a temporal relationship among the integration time periods of the photosensitive elements and to detect a timing interval in which the light pulse is received by identifying the distinct temporal pattern corresponding to that timing interval.

[0082] Other operations, calculations and computations may be performed by processor 140. Optionally, processing results may be provided by processor 140 to any one or more of: a tangible memory module 180 for storage or later retrieval, for external systems e.g., a remote server via communication module 190. According to some embodiments of the present disclosure, the imaging system may further include or be connected to an external display 170 operatively coupled to the imaging receiver 110, controller 150 and processor 140. Display 170 may be configured to visually present image data, detection results, or system status information generated by the imaging receiver or the image processor 140. The displayed information may include, for example, one or more captured image frames, identified light spots or targets, timing or detection parameters, or processed imagery derived from spectral or temporal analysis. In certain embodiments, display 170 may function as a userinterface element allowing an operator to monitor system performance, verify alignment, or adjust operational parameters such as exposure time, integration period, or sensitivity thresholds.

[0083] Display 170 may be implemented using any suitable display technology, including but not limited to a liquid-crystal display (LCD), organic light-emitting diode (OLED) panel, micro-LED screen, or projection-based device. The display may be physically integrated within the imaging receiver housing or provided as an external component communicatively linked through the communication module 190. In some embodiments, the display 170 may be configured to present both real-time and recorded imagery, optionally including visual overlays or indicators identifying detected targets or light spots.

[0084] According to some embodiments of the disclosure, a photodetecting array 120, may detect repetitive optical signals, e.g., laser signals, which may have certain predetermined characteristics of pulse length, pulse size, and repetition rate or frequency. For example, pulse length of 1-10 nano second, a pulse size of 3*3 - 10*10 pixels, and a frequency of 5-100 Hz.

[0085] The sensor may calculate the light appearance frequency and x / y spatial location. The system may further detect a timing interval or a time period in which the light pulse is received from the field of view, thereby determining the temporal occurrence of the pulse with a predefined level of accuracy or precision. The timing interval defines the temporal resolution of detection, that is, a distinguishable time window within which a light pulse should be identified. Higher timing accuracy corresponds to the degree to which the detected interval reflects the true arrival time of the light pulse. By refining the integration timing and reducing the timing intervals in which the pulse may be detected in, the system may reduce uncertainty in pulse timing.

[0086] Imaging system 100 may operate in real-time while continuously acquiring, processing, analyzing optical signals received from the field of view and dynamically control the sensor mode of operation according to the various search stages to allow determining the light appearance frequency and location in the image. In addition, the sensor may output visual frames periodically, e.g., according to a predefined timing scheme while the pulse detection continues to be performed. Controller 150 may adjust and control sensor parameters, such as integration time, exposure mode, frame rate, and region of interest to optimize detection of a light spot or pulse within the field of view. Through this adaptive operation, imaging system 100 may enable determination of both the light appearance frequency and the spatial location of the detected light spot within the image frame.

[0087] In some embodiments, sensor 120 may periodically output visual image frames, e.g., by display 170, according to a predefined or programmable timing scheme. Such periodic output may include either full-frame or sub-frame data, depending on the operational mode, search stage, or detected event. This configuration enables continuous monitoring of the scene while supporting accurate temporal analysis of repetitive or transient light signals. In some embodiments, the visual image frames output rate or timing intervals may be dynamically modified in response to the spot detection process progress or according to the plurality of the search stages during the duration of light spot detection.

[0088] Fig. 3 shows a flowchart of process for light spot detection in accordance with embodiments disclosed herein. Process 200 shown in FIG. 3, may be implemented, for example, by imaging system 100 of FIGS. 1A and 2 as described herein. A non-transitory computer readable medium may contain instructions which, when executed by at least one processor, e.g., processor 140 or controller 150 of imaging system 100, may perform the method and operations described at each of the steps in process 200. The non-transitory computer readable medium and at least one processor may correspond to one or more of processors 140, and memory 180 of imaging system 100 as described herein. In some embodiments, process 200 may be performed “on-the-fly” or in “real time” implying that process 200 may be performed while images are being captured and processed by a photodetector array e.g., sensor 120 of imaging device 100 of FIGS. 1 A and 2.

[0089] FIG. 3 illustrates a hierarchical, multi-stage detection methodology in which each successive search stage refines the detection parameters obtained from the preceding stage. This approach allows the system to efficiently narrow the search space, reduce processing time, and improve the precision of light pulse detection. Although the stages are illustrated sequentially, it should be understood that each search stage may be executed independently, concurrently, or in any desired order based on operational conditions, system configuration, or control logic. Furthermore, different combinations or subsets of the search stages may be implemented according to application requirements, for example, by omitting, merging, or repeating certain stages to optimize performance, response time, or detection reliability. The configuration shown is therefore exemplary and non-limiting, and other stage arrangements or detection hierarchies may be employed within the scope of the present disclosure.

[0090] Embodiment of the disclosure may include performing a search on signals converted from the accumulated charge to detect one or more light pulse appearances with a predefined precision by performing a plurality of search stages. One or more search stages may be performed in order to determine the location of the light spot within the image frame and the timing of its appearance with a predefined accuracy level. Each search stage may include multiple iterations and may enhance detection accuracy by progressively reducing the time window or timing interval within which a light spot is detected.

[0091] The term “search stage” refers to a defined detection phase or iteration during which imaging system 100 applies specific operations to evaluate the presence of a light spot with a certain accuracy, e.g., within a specific time duration. Each search stage configured to refine one or more detection parameters based on results from a preceding stage. The plurality of search stages may be executed sequentially, while each stage may be executed iteratively and progressively narrow a search range or adjust timing, spatial, or spectral criteria to improve the accuracy of light spot detection.

[0092] The multi-stage search operation may include a first search stage, also refer to herein as “coarse search”, one or more intermediate refinement search stages, and a fine search stage search stage. The first search stage may operate over a broad temporal or spatial window to identify candidate events of light spot detection, while subsequent stages may successively reduce the search window or adjust detection thresholds to isolate and confirm a light spot with higher precision within timing intervals that may be reduced at each iteration and / or search stage as described with reference to process 200.

[0093] In step 210, a first search stage may be performed on a sensor area, e.g., of sensor 120 by imaging system 100. The first search stage may include scanning a portion or the entirety of the sensor area to determine the light spot spatial location within the sensor area and a timing of detection with a first timing accuracy. The terms “timing accuracy”, “precision” and “temporal resolution” may refer to a duration of time in which a single light pulse may be detected. This duration of time may also be referred to herein as a “time window” or a “time period”. The timing accuracy may be improved in every search stage by being reduced, namely to shorten the duration of time within which a pulse is detected until a predefined precision or predetermined accuracy is achieved.

[0094] The timing accuracy of the detection may be determined based on, or according to, the exposure time duration of a photodetector cell or of a row of photodetectors within sensor 120. In certain embodiments, shorter exposure times may provide higher temporal resolution, allowing more precise determination of the time at which an optical event, such as a light pulse, occurs. The exposure time duration may further be limited by physical or performance constraints of the sensor, such as signal-to-noise ratio (SNR), saturation level, dark current accumulation, or readout speed. Accordingly, the exposure or integration time of individual photodetector cells or rows may be selected or controlled to achieve a desired balance between timing accuracy and signal quality, within the operational limitations of sensor 120. According to some embodiments, the exposure times may be dynamically controlled or selected “on the fly”, in real time, during sensor operation to allow different timing accuracy in each search stage, or in each iteration. Exemplary exposure times or timing accuracy of the first search stage may be between 50-500 microseconds, e.g., 250 microseconds as described in some embodiments of the invention.

[0095] According to some embodiments, the first search stage may be performed on the entire area of the photodetector array 120. However, there may be a physical limitation in scanning the entire sensor area due to the electrical configuration or design of sensor 120, for example, limitations associated with the capacitance of the photodetector cells or other electrical components.

[0096] In some embodiments of the disclosure the first search stage may be performed sequentially on a plurality of sub-areas or partial regions within the sensor area until a light pulse is detected within one of the sub-areas with a first timing accuracy. Scanning a plurality of sub-areas of the sensor may enable operation within the limitations or physical constraints imposed by the electrical configuration or design of the sensor. Scanning may include sequentially scanning of the plurality of the sub-areas while scanning each of the sub-areas may be performed iteratively and may be repeated for a predetermined duration of time or until a light pulse is detected. Defining tor determining the size or area of each of the sub-areas may relate to electrical and / or physical characteristics of the sensor array or related electrical circuits, e.g., readout circuitry. For example, the number of lines or rows of photodetector cells included in each sub area may be defined based on one or more sensor parameters, system parameters or light spot parameters such as for example, readout time, integration time and / or maximum exposure time, spot size.

[0097] During the first search stage, each of the sub-areas of the sensor array may be scanned iteratively in order to identify a light spot appearance. The scan or detection may include performing a plurality of iterations on the plurality of rows of photodetector cells of the sensor which are included in each of the sub areas. According to embodiments of the disclosure, the iterative scanning of each of the sub-areas during the first search stage may include dividing each of the sub-areas into a plurality of blocks and simultaneously scanning the plurality of blocks while at least one row of each of the plurality of blocks is exposed to light at any given time. The size of each of the plurality of blocks may be determined according to a spot size corresponding to the light pulse.

[0098] The iterative scanning of each sub-area may be repeated in the first search stage for a predetermined duration of time or until the pulse is being detected. The predetermined duration of time may be determined based on system parameters or based on preliminary knowledge of the light frequency. For example, the predetermined duration of time for scanning each of the sub areas may be defined as: 1 divided by a minimum light frequency to be detected, e.g., 125 milliseconds if the light frequency is 8 Hz. If a pulse is not detected, the scanning moves to the next sub-area and repeats in circular mode on each sub area until a pulse is found. If a pulse is detected before scanning of the last sub area, the first search stage may be stopped, and subsequent sub area may not be scanned but the process may move to the next search stage.

[0099] When the first search stage is performed over discrete sub-areas of the sensor array, the effective search region for subsequent stages may be reduced. By detecting the presence of a light spot within a specific sub-area, the portion of the sensor to be scanned the next search stage may be reduced. This approach significantly reduces computational load and search time, allowing subsequent stages to focus only on the relevant localized region, thereby improving both processing efficiency, time of search and detection accuracy. Reference is now made to FIGS. 5A-5B which illustrate a schematic representation of an exemplary first search stage on a visual image and a corresponding timing scheme in accordance with embodiments disclosed herein. FIG.5A shows a visual image frame 500 in which a pulse of light is detected at location 505 within sub area 520. It should be understood that the method for detection of light spot described in embodiments of the disclosure does not require and does not based on a visual image. However, according to some embodiments of the disclosure, a visual image may be produced and presented or displayed to visualize the location of the light spot.

[0100] Visual image frame 500 represents or corresponds to a pixel array, e.g., of pixel array 120 of FIG. 2, which may be divided to sub areas 510, 520, 530 and 540. Each of the sub areas may include, for example, a quarter of the image and / or the pixel array. For example, each of the sub areas 510, 520, 530 and 540 may include 250 lines of photodetector cells. The duration of time for scanning each sub area may be defined as: 1 divided by the minimum light pulse frequency to be detected. In the example of FIG. 5 A a light pulse frequency of 8 Hz is presented and therefore each of sub areas 510, 520, 530 and 540 may be scanned during 125 milliseconds, as shown.

[0101] FIG.5B shows a corresponding timing diagram along a time axis 550. Sub areas 510, 520, 530 and 540 are presented along time axis 550, each of the sub blocks may be scanned for a duration of 125 milliseconds. The pulses 501, 502, 503 and 504 arrive every 125 milliseconds as their exemplary frequences is 8 Hz as shown in Fig. 5B. The second pulse 502 is the light pulse detected as its position or spatial location is in sub area 520 shown in FIG. 5A.

[0102] Reference is made back to FIG. 3. As indicated in decision block 220, if a light pulse is not detected, the process may repeat along path 225 and the first search stage may be continued in additional sub areas until a pulse detection event occurs. A detection of a light pulse during the first search stage may include determining a spatial location of the detected light spot by finding its coordinates within the pixel array (image frame) of the sensor. Upon detection of a light spot in the image frame, processor 140 may determine the location of the spot based on one or more image coordinates associated with the illuminated pixels. In some embodiments, the location may correspond to the pixel having the maximum detected intensity. In other embodiments, the location may be determined as a centroid of the intensity distribution of the illuminated pixels, thereby providing sub-pixel positional accuracy. The determined coordinates may be further converted to spatial or angular coordinates relative to the imaging system based on the optical parameters of the sensor and lens assembly. A detection of a light pulse during the first search stage may further include detection of the arrival time of the detected light pulse with a first timing accuracy, e.g., within a predetermined first exposure period. Once a pulse is detected in the first search stage, a second search stage is being performed as indicated in step 230.

[0103] In step 230, a second search stage may be performed on a reduced sensor area as location of the detected spot is known from the first search stage. After a location of the spot is detected during the first search stage, the search area may be reduced in subsequent search stages. A smaller region of the sensor array may be scanned e.g., a lower number of rows may be scanned during the second search stage. This reduction in the scanned area allows faster acquisition and improved temporal accuracy while maintaining detection precision

[0104] The search area or region to be scanned during the second search stage may be selected around the spatial location in which the spot was found in the first search stage. For example, a reduced number of rows or lines of photodetectors may be activated and / or read out, corresponding to an area surrounding the previously detected spot location. The scanning method of the second search stage may be similar to that of the first search stage, however scanning a smaller region, e.g., smaller number of rows, allows reducing the exposure time needed in the second search stage.

[0105] The second search stage may include scanning of a localized sensor area, e.g., a selected search area to determine the next light spot timing of detection with a second timing accuracy within the selected search area. The second timing accuracy or a second “time window” which refers to a second duration of exposure time, shorter than the first timing accuracy concluded from the first search stage.

[0106] According to some embodiments, the exposure times may be controlled or changed between search stages on the fly, during sensor operation to allow different timing accuracies in each search stage, or in each iteration, exemplary exposure times or timing accuracy of the second search stage may be between 20 - 200 microseconds, e.g., 32 microseconds as described in some embodiments of the invention.

[0107] The scanning of the reduced selected search area or limited region may be repeated during the second search stage for a predetermined duration of time or until a pulse is being detected. The predetermined duration of time may be determined based on system parameters or based on preliminary knowledge of the light frequency. For example, the predetermined duration of time for each sub area may be defined as 1 divided by minimum light frequency to be detected, e.g., 125 milliseconds if the light frequency is 8 Hz. If pulse is not detected, the scanning repeats in circular mode until a pulse is found.

[0108] After a pulse is detected the first time during the second search sage, the information known may include: a) the row in which the pulse was detected, which is known from the first search stage and b) a time duration between two pulses (a first pulse from the first search stage and a second pulse from the second search stage). The time period or duration between two consecutive pulses may be known with a combined timing accuracy which is a sum of the first timing accuracy or time window (from the first search stage) and the second timing accuracy or time window (from the second search stage). The combined timing accuracy is the period of time or the duration of time in which two consecutive light pulses are detected. A pulse frequency is known with a precision which equals to the combined timing accuracy of the last two pulses detected. An exemplary combined timing accuracy after one pulse is detected during second search stage is 282 microseconds which is the sum of 250 microseconds from the first search stage and 32 microseconds from the second search stage.

[0109] The second search stage may be repeated for additional search in exactly the same manner one more time which may allow to detect the timing of the next pulse with the second timing accuracy of the second search stage. A second detection during the second search stage allows calculating a total accuracy of twice the duration of the second time window or second timing accuracy. For example, if the second time window equals 32 microseconds the accuracy of the frequency of the light pulse is 64 microseconds after two pulses are detected during the second search stage.

[0110] As indicated in decision block 240, if a pulse is not detected, the process may repeat along path 245 and the second search stage may be continued until a first pulse detection event occurs, and next another round of second search stage may be performed until a second pulse is detected in order to achieve the accuracy of twice the duration of the second time window.

[0111] Following successful second detection in the second stage, a fine search may be executed as indicated in step 250 to achieve higher temporal precision. The fine search stage may improve the accuracy up to a required predefined precision, e.g., 0.1-3 microseconds. After the second search stage, the pulse timing is known with the timing accuracy of twice the duration of the second timing accuracy, e.g., 64 microseconds. In order to achieve a higher precision and to shorten the timing windows in which a pulse is being detected the fine search stage in being performed iteratively in a cyclic manner with reduced exposure time periods or integration time period in each iteration, until a defined precision is reached. The fine search is performed by scanning a portion or the entirety of the sensor area to improve the timing of detection until a predefined accuracy or precision is reached. In some embodiments, the fine search may be conducted on a set of sensor lines corresponding to, or closely surrounding, the reduced search area identified in the second search stage, thereby allowing localized refinement of the detected pulse position and timing. In some embodiments, the specific lines or regions of the sensor selected for the fine search may remain constant for repeatability, while in other embodiments, the selected area may shift slightly between iterations. Such adaptive adjustment enables dynamic tracking of the light spot as it moves within the field of view, enhancing spatial and temporal detection accuracy.

[0112] Embodiment of the disclosure may control the duration of the integration time period also referred to herein as “duration of the exposure time period” for each of the plurality of the photosensitive elements and a temporal relationship between the integration time periods or the exposure time periods of the photosensitive elements, e.g., by creating a plurality of overlapping regions between integration time periods or exposure time periods. The temporal relationship between the integration time period of each of the photosensitive elements may define a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period. The distinct temporal patterns may be used for identifying the exact timing interval in which a pulse is received from the field of view by identifying the distinct temporal pattern corresponding to that timing interval as described in embodiments of the disclosure.

[0113] During the fine search a precise timing may be determined by a detection scheme which may include use of a global shutter operation mode of sensor array 120. A global shutter operation mode relates to a mode of operation in which all photodetector elements of the image sensor are exposed to incident light simultaneously. During the fine search, a global shutter operation mode may be operated on the entire sensor array, or on a reduced sensor area or limited region, for example, the same reduced sensor area on which the second search stage is performed.

[0114] According to some embodiments of the disclosure during the fine search stage, a global shutter operation mode may be operated with binning of photodetector cells. Image sensor 120 may be configured to perform pixel binning, wherein signals from a two or more adjacent photodetector cells are combined to form a single output pixel value. For example, binning of two or more photodiodes from adjacent rows which are exposed to incident light simultaneously may be grouped together into a single “super pixel”. Each super pixel may open integration windows at different times allowing the exposure timing of each row to be controlled independently. While the photodetector cells are shorted into a single effective super pixel, the readout circuitry 160 may retain control of separate integration “switches” enabling different integration widths and delays. The separate integration “switches” may allow independent control of integration timing to employ affectively shorter time windows at every round of the fine search until a required predefined accuracy or precision may be achieved.

[0115] During operation of the photodetector array, each pixel or photodetector element converts incident light into electrical charge proportional to the received light intensity. The accumulation of charge within the pixel, also referred to as “charge integration” is controlled by timing signals generated by controller 150. These control signals define the beginning and end of the integration period, thereby determining the duration over which each photodiode or photosensitive element collects charge. Once the integration period has elapsed, the accumulated charge is transferred to a readout circuitry and / or capacitor for further processing. According to some embodiments, the charge integration time may be controlled to allow selective timing delays.

[0116] Reference is made to FIG. 8 which shows an exemplary diagram of a fine search stage used in methods for light spot detection in accordance with embodiments disclosed herein. According to some embodiments of the disclosure, while in global shutter mode each of the photodetector elements or pixels is exposed to light simultaneously, however the control of the integration time, e.g., the charge integration of each of the photosensitive elements may be performed at different times, with variable delays, or over different integration durations. This configuration allows flexible timing control across the pixel array. In some embodiments of the disclosure during the fine search stage a plurality of pixels may be binned, for example, electrical signals or charge outputs of four adjacent photosensitive elements may be combined into a single output value and may be connected to a single capacitor or readout circuit.

[0117] In some embodiments during the fine search stage, the sensor array may be operated with line resolution. For example, each line or row of photodetector elements or pixels may be combined into a single output value and may be connected to a single capacitor or readout circuit. While the entire sensor may be exposed to light during a total exposure period, each of the lines or roes of the sensor may be controlled separately such as to allow different integration time periods for each line of photodetector elements. In FIG. 8, vertical axis 805 corresponds to individual rows or pixels within pixel array 120. Accordingly, timing diagram 800 may represent the timing sequence of four adjacent rows in the pixel array 120, or alternatively, four adjacent pixels, each located in a different but neighboring row. The notation along axis 805 represents sequential or grouped pixel rows within the array. Accordingly, timing diagram 800 illustrates the integration or exposure timing of four adjacent rows such as those indexed by 4N through 4N+3 or equivalently, four adjacent pixels each positioned in a different but consecutive row. This representation allows visualization of the relative timing relationships between neighboring pixels or pixel groups within the pixel array 120.

[0118] As shown by time axis 850, a timing accuracy or exposure time (or integration time which is identical) from the second stage, e.g., 64 microseconds may be divided by four to create four timing intervals 810, 820, 830 and 840 such that each of the pixels or rows correspond to a different timing interval within the integration time period of the 64 microseconds (850). Each of timing intervals 810, 820, 830, and 840 represents an individual integration or exposure period having a duration of approximately 16 microseconds, sequentially positioned at different locations within a total timing period of 64 microseconds. Accordingly, each timing interval corresponds to a distinct temporal segment within the overall duration of the integration time period, such that the integration windows are temporally shifted or staggered relative to one another within the 64- microsecond frame.

[0119] Within the total exposure period of 64 microseconds, each of the four lines or pixels, identified as 4N, 4N+1, 4N+2, and 4N+3, is exposed to light and accumulates charge during only one distinct timing interval. Accordingly, at any given moment within the exposure period of 64 microseconds, only one of the four rows or pixels is actively integrating light. This staggered exposure arrangement enables higher temporal accuracy in determining the timing of a detected light pulse. Specifically, when a pulse is detected within a particular timing interval, the pulse appearance timing may be associated with that corresponding integration window, thereby improving the timing resolution or precision of the detection event.

[0120] For example, when a pulse is detected within timing interval 810, the pulse may be associated with the corresponding integration window, e.g., the first 16 microseconds. When a pulse is detected within timing interval 820, the pulse may be associated with the corresponding integration window, e.g., the second 16 microseconds. When a pulse is detected within timing interval 830, the pulse may be associated with the corresponding integration window, e.g., the third 16 microseconds. When a pulse is detected within timing interval 840, the pulse may be associated with the corresponding integration window, e.g., the last 16 microseconds of the duration of the integration time period (64 microseconds).

[0121] Reference is made to FIG. 9 which shows exemplary timing diagrams illustrating the temporal relationship between integration time periods of a plurality of photosensitive elements in accordance with embodiments disclosed herein. According to embodiments of the disclosure the fine search stage includes controlling the duration of the integration time period of each of the photosensitive elements and the temporal relationship between the integration time period of each of the photosensitive elements, in order to achieve progressively higher detection accuracy with each iteration or round of the fine search.

[0122] As shown by timing diagram 910, this configuration represents a basic multi-tap approach with four discrete exposure intervals or “taps”. Each tap samples the reflected light at a fixed phase, providing fundamental temporal information. Each “tap” may relate to a photosensitive element or a plurality of grouped photosensitive elements, for example, to a row or a line of photosensitive elements. The four taps may be positioned adjacent to each other in the pixel array or may be positioned anywhere within the pixel array. The duration of the integration time period, also referred to herein as “timing interval” 911, 912, 913 and 914 of each of the taps 0-3 respectively are sequentially positioned as different timing interval within the total integration time period 900. Accordingly, each timing interval 911, 912, 913 and 914 corresponds to a distinct temporal segment within the overall operational period, as also described with reference to FIG. 8. duration of the integration time period

[0123] Timing diagram 920, shows a better or higher timing resolution or higher precision of the detection compared to timing diagram 910, as the temporal relationship between the integration time period of each of the photosensitive elements defines a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period. Integration times 961-964 of each of the four “taps” 0-3 may overlap in a predetermined pattern as to create distinct temporal patterns for each timing interval within the total duration of the integration time period. The overlapping between the integration times of the four photosensitive elements may define or create a plurality of distinct temporal patterns identified as 921-927, each corresponds to a different timing interval within the total integration time period. Each of the temporal patterns 921-927 may represent a “virtual tap”, e.g., taps 0-6 respectively (although only 4 real “taps” are used), defined a unique temporal relationship between the integration time period of each of the photosensitive elements. The concept of “virtual taps” refers to computationally derived sampling points obtained through combinations of multiple exposures, effectively increasing temporal resolution without requiring additional hardware taps.

[0124] For example, distinct temporal pattern 921 relates to the combination of “1 0 0 0” where tap 0 =1, tap 1=0, tap 2=0 and tap 3=0. distinct temporal pattern 922 relates to the combination of “1 1 00” where tap 0 =1, tap 1=1, tap 2=0 and tap 3=0. distinct temporal pattern 923 relates to the combination of “0 1 0 0” where tap 0 =0, tap 1=1, tap 2=0 and tap 3=0. It should be understood that each of the distinct temporal patterns of each timing interval 921-927 has a distinct, different, unique or exclusive pattern which may be used to identify the appearance of a light pulse. The pattern is a combination of “0” and “1” where detection of “1” relate to light detection and “0” relate to “no light is detected”. Detecting a timing interval in which a light pulse is received from the field of view may be performed by identifying the distinct temporal pattern corresponding to that timing interval within the total duration of the integration time period or a total duration of exposure time.

[0125] Timing diagram 930 illustrates an improved timing configuration that provides higher temporal resolution and greater timing precision compared to timing diagrams 910 and 920. The refined timing intervals 931-945 shown in diagram 930 enable more accurate determination of the light pulse occurrence within total integration window 900, thereby enhancing the overall detection accuracy of the imaging system. The temporal relationship between the integration time period of each of the photosensitive elements defines a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period. The distinct temporal pattern of each timing interval identified as 931-945 where each represent a “virtual tap”, e.g., taps 0-15 respectively, by the unique temporal relationship between the integration time period of each of the photosensitive elements. This method extends the previous approach by using double exposures per tap within a Gray code framework. As a result, it achieves 15 virtual taps, further refining temporal precision, improving signal-to-noise ratio (SNR), and minimizing phase ambiguity.

[0126] For example, distinct temporal pattern 931 relates to the combination of “1 1 0 0” where tap 0 =1, tap 1=1, tap 2=0 and tap 3=0. distinct temporal pattern 932 relates to the combination of “0 1 00” where tap 0 =0, tap 1=1, tap 2=0 and tap 3=0. distinct temporal pattern 933 relates to the combination of “0 1 1 0” where tap 0 =0, tap 1=1, tap 2=1 and tap 3=0. It should be understood that each of the distinct temporal patterns of each timing interval 931-945 has a distinct, different, unique or exclusive pattern which may be used to identify the appearance of a light pulse within the total duration of the integration. Detecting a timing interval in which a light pulse is received from the field of view may be performed by identifying the distinct temporal pattern corresponding to that timing interval within the total duration of the integration time period.

[0127] According to some embodiments of the present disclosure, Gray code encoding may be utilized in the detection process of a light pulse to improve timing accuracy and minimize ambiguity between adjacent detection intervals. Gray code, also referred to as reflected binary code, is characterized by the property that only a single bit changes between successive code values. This property reduces the likelihood of detection or decoding errors that may occur during fast transitions between timing states. During light pulse detection, each timing interval or exposure phase may be assigned a unique Gray code value, allowing the imaging system to identify the precise timing interval in which a light pulse is received. The use of Gray code encoding enables more robust and reliable detection under high-speed or noisy conditions by reducing the impact of bit errors and improving synchronization between timing intervals and sensor readout.

[0128] Reference is made back to FIG. 3, the fine search stage, indicated in step 250, may include controlling of the integration times and the corresponding accumulated charge in the capacitors of the readout circuitries of each of the photodetector elements or for example, each of the lines of the photodetector array. During the fine search stage, controller 150 or processor 140 may control, for each of the plurality of photosensitive elements, the duration of the integration time period within a total exposure duration or total duration of the integration time period. In addition, controller 150 or processor 140 may control a temporal relationship between the integration time periods of the photosensitive elements. Controlling the temporal relationship may be performed by formation of overlapping between integration times such that each timing interval within the total exposure time or integration time may include a unique temporal combination corresponding to each timing interval within the overall integration duration. Controlling integration times and selective readout times may allow creation of a plurality of time windows that may be shorter every round of the fine search stage and therefore the time window or timing accuracy in which a light pulse is detected may be minimized up to a predetermined accuracy. Embodiments of the disclosure may further include controlling the duration of the integration period of each photosensitive element and overlapping between them such as to define a temporal coordination or relationship between the integration periods of the plurality of photosensitive elements. The temporal coordination or relationship between the integration periods may establish a distinct timing pattern corresponding to each timing interval within the overall integration duration or total exposure duration.

[0129] The process of the fine search stage may further include detection of the timing interval during which a light pulse is received from the field of view by identifying the corresponding distinct timing pattern associated with that interval. As indicated by decision block 260, the system determines whether a pulse has been detected with the required level of accuracy. If the required accuracy has not yet been achieved, the fine search operation may be repeated, as shown by feedback path 265.

[0130] A plurality of iterations of the fine search stage may be performed when in each of the plurality of the iterations, the integration time period may be reduced, thereby each of the timing intervals within the integration time period is shortened until the light pulse appearance is detected with the predefined precision. Once a pulse is detected and verified with the desired accuracy or predefined precision, the process proceeds to block 270, where the system provides detection results. The results may include, for example, the detected pulse timing, location within the sensor array, intensity, or other relevant parameters associated with the light spot. The detection results may be presented and / or stored. For example, by indicating on a visual image of the FOV the location of a light spot and other timing parameters.

[0131] It should be understood that the illustrations presented in FIGS. 4A-10 depict exemplary timing relationships and numerical parameters that are provided solely for purposes of explanation and ease of understanding. The specific values, durations, intervals, and other numerical examples shown are not intended to limit the scope of the present disclosure. Alternative timing schemes, parameter values, or operational configurations may be employed without departing from the spirit and scope of the invention. The illustrated figures are therefore to be regarded as schematic and exemplary representations rather than restrictive technical specifications.

[0132] FIG. 4A shows an exemplary diagram of a first search stage used in methods for light spot detection in accordance with embodiments disclosed herein. The first search stage, also referred to herein as a “first coarse search” may be repeated until a light spot is detected, such that both the spatial location and timing of the detected light spot are determined, albeit with a first timing accuracy, e.g., 250 microseconds which corresponds to a first exposure time.

[0133] During the first search stage the search area which corresponds to the area of the sensor array may be divided into a plurality of sub areas. Each of the sub areas may include a plurality of rows of photodetecting elements within the photodetector array 120. For example, an exemplary photodetector array which includes 1280 columns and 960 rows or lines may be divided to or split into four sub-areas. Each exemplary sub area may include 250 lines or rows (240 lines +10 lines overlaps with previous / next sub area). A first exemplary sub area may include rows 0-250 of sensor array 120, a second exemplary sub area may include rows 240-490 of sensor array 120, a third exemplary sub area may include rows 480-730 of sensor array 120, and a fourth exemplary sub area may include rows 720-960 of sensor array 120. Any other division of the search area may be applicable.

[0134] FIG. 4A shows a timing diagram 300 of a first search stage which corresponds to performing the first search stage in a single sub area from the plurality of sub areas of the sensor area. The vertical axis 310 shows the row number within a selected sub area, e.g., 0-250 in the exemplary division, while the horizontal axis 311 represents time. Element 315 shows an exposure time 316 followed up by a readout time 317. It should be noted that element 315 is provided solely for illustration purposes to conceptually represent the timing structure of the exposure and readout sequence of each row. Element 315 is not intended to denote a physical component or functional module of the imaging system, but rather a schematic representation used to simplify the depiction of timing relationships in the rolling shutter operation. As illustrated, element 315 encompasses the exposure period 316 and the readout duration or period 317. While these timing intervals occur for each row of the sensor array, they are explicitly illustrated only for the first row for the sake of clarity.

[0135] In some embodiments, determining the area of each of the plurality of the sub areas may be based on the maximal exposure time 316 and the readout duration period 317. For example, an exposure time is selected to be 280 microseconds due to SNR considerations or based on other physical parameters of sensor array 120. An exemplary readout time may be 5.6 microseconds therefore 50 lines may be read during an exposure period of 280 microseconds as 280 divided by 5.6 results in 50 lines. If 50 lines may be exposed simultaneously and the size of the pulse or spot to be detected is 5*5 pixels a sub area may be determined as 250 lines (50 lines* 5 hight of the light spot).

[0136] According to some embodiments of the present disclosure, scanning each of the sub-areas of the sensor array may include dividing each of the sub-areas to a plurality of blocks and simultaneously scanning the plurality of blocks, while at least one row of each of the plurality of blocks is exposed to light at any given time to ensure that a light spot is detected during operation.

[0137] In some embodiments, the division or distribution of each sub-area into blocks may be determined in accordance with the size of the light spot to be detected. For a light spot occupying an area of XxY pixels, each block may include at least Y rows of the sensor array such that, at any given time, at least one of the Y rows is actively exposed to incident light. The size of each of the plurality of blocks may be determined according to the size of the light spot, e.g., if the height of the spot is 5 pixels, a block of 5 lines may ensure detection of the spot if at any given time at least one line of the block is exposed to sensing light.

[0138] In the exemplary configuration illustrated in FIG. 4A, the exemplary sub-area includes rows 1 to 250 is divided into a plurality of blocks, each including five rows as the exemplary light spot occupies an area of at least 5x5 pixels. Therefore, in exemplary illustration of FIG. 4A block 320 includes rows 1 to 5, block 321 includes rows 6 to 10, and the last block of the sub-area, block 322, includes rows 246 to 250. This division into blocks corresponds to the exemplary sub-area of 250 rows. The general expression defining the row indices for the nthblock, in case a spot size in minimum 5*5 pixels, may be represented as follows: 5n + 1, 5n + 2, 5n + 3, 5n + 4, 5n + 5. where n > 0 represents the block index within the sub-area. Thus, the first block (n = 0) includes rows 1 to 5, the second block (n = 1) includes rows 6 to 10, and so forth. This formulation provides a generalized mathematical representation of the above example and is presented for exemplary purposes only. Any other formulation or division scheme may be employed in accordance with the specific spot size, number of sub-areas, or desired detection configuration.

[0139] According to embodiments of the disclosure, during the first search stage, the sensor is configured to work in rolling shutter mode, in which the integration time guarantees that at least 1 out of every Y rows is open for exposure at any given moment. With assumption of minimum spot size of 5x5 pixels, at least 1 out of every Y rows is open for exposure at any given moment and therefore the spot will not be missed. The scanning of each sub-area may be performed by a rolling shutter technique with a predetermined exposure time, duration or period 316, e.g., 250 microseconds exposure time. All exposure durations 316 may be identical and may follow by a readout duration 317. Rolling shutter technique or mode of operation refers to a sensor readout method used for capturing images sequentially rather than all at once. The sensor array may be exposed and read out the image line by line (row by row) sequentially.

[0140] In a rolling shutter mode of operation, while scanning each sub area, the imaging sensor may perform exposure (316) and readout (317) of the pixel array in a sequential manner rather than simultaneously across all pixels. The process begins with a first row of photodetector cells being activated to collect incident light over a defined exposure time, also referred to herein as “integration time period” 316. Upon completion of the integration period for the first row, e.g., 316 (1) the corresponding electrical charge or signal is read out, e.g., 317 (1) while a subsequent row, e.g., row 2, is sequentially exposed, e.g., 316 (2). As shown in timing diagram 300, while a first line (row 1) is being read indicated by 317(1), the next line (row 2) is exposed and there is an overlapping between the readout period of the first line 317(1) and the beginning of the exposure period of the second line 316(2), indicated by element 318.

[0141] Reference is made to FIG. 4B, which is similar to FIG. 4 A, but further includes an illustration representing the relationship between the rows (lines) of the sub-areas and their corresponding locations within the captured image. It should be noted that although not all reference numerals and elements shown in FIG. 4 A are repeated in FIG. 4B, the corresponding elements are identical in structure and function. Therefore, for the sake of conciseness, features differing from FIG. 4 A are explicitly described with respect to FIG. 4B, and identical elements retain the same reference numerals and corresponding description as previously provided.

[0142] In some embodiments described in the disclosure, in order to detect a spot with an exemplary size of 5*5 pixels, at least one row of each block from the sub area should be open for exposure at any given time. If at any given time at least one row of a block, e.g., one row out of 5 rows is open for exposure, it may ensure detection if a spot arrives within that sub area. Therefore, each first line of each block, e.g., row 1, row 6, row 11 up to row 246 should be exposed to light at the same time and after their exposure time ends the next row at each block should be open for exposure, e.g., row 2, row 7, row 12 and up to row 247. In some embodiments the group of corresponding rows in each of the plurality of blocks of a sub area, e.g., the group of first rows out of 5 rows may be open for exposure at the exact time. In some embodiments, as shown in the exemplary illustration of FIG 4A-4B, there may be a delay in the opening of each group to exposure due to the readout periods 317, as according to certain implementation read outs may not be performed simultaneously. Therefore, each of the corresponding rows from each block may be open in a certain delay from the previous row. For example, row 6 is opened after a duration of a read out from the beginning of the exposure time of row 1, as shown by 422.

[0143] FIG. 4B illustrates an exemplary timing relationship between the exposure and readout periods of the sensor rows and their corresponding representation within the captured image. An exemplary light pulse 410 which its reflection may be collected by sensor 120 at a time indicated by 420 which is included in the exposure times of rows 1 and 6. An exemplary portion of sensor array 120 may be represented by an exemplary pixel map 450 of a portion of sensor array 120 which includes matrix of 6 rows and 6 columns. An exemplary spot 460 having size of 5*5 pixels is presented on array 450.

[0144] Row 1 of the sensor begins its exposure period 316 (1) during which it may accumulate light. Following completion of the exposure period 316(1), row 1 enters its readout period 317(1), during which the accumulated charge is transferred for processing or storage. The exposure and readout timing of row 1 corresponds directly to the pixels represented by row 471 in the pixel map 450 as shown by element 430. The exposure and readout timing of row 6 corresponds directly to the pixels represented by row 441 in the pixel map 450 as shown by element 440. During the exposure time of rowl and 6, rows 2-5 of array 450 indicted by element 470 are not exposed to light and shown as black rows. As desired in order to detect the 5*5 pixels spot 460, at least one row of each block is open for exposure at any given moment in time. While one line is being read, the next row is exposed.

[0145] It should be understood that the same timing relationship applies to subsequent rows of the sensor array. For example, row 2 corresponds to the next readout time 317(2), which maps to the adjacent image row below row 471, and so forth for each subsequent sensor row. This sequential exposure and readout structure allow capture of the light spot.

[0146] The specific timing intervals and numerical parameters illustrated in FIGS. 4A-4B are exemplary only and are not intended to limit the scope of the present disclosure. Variations in exposure duration, readout sequencing, number of rows, array dimensions or mapping order may be implemented according to system design or operational requirements. Reference is made to FIG. 6 which shows an exemplary diagram of a second search stage used in methods for light spot detection in accordance with embodiments disclosed herein. The second search stage, also referred to herein as a “second coarse search” may include scanning a selected search area around the spatial location of the light spot detected in the first search stage until another light spot is detected within the selected search area with a second timing accuracy.

[0147] The second search stage may be performed on a reduced sensor area as location of the detected spot is known from the first search stage. After a spatial location of the spot is detected during the first search stage, the selected search area in the second search stage may be reduced and a smaller area of the sensor array may be scanned. The area to be scanned during the second search stage may be selected around the location in which the spot was found in the first search stage. After the first search stage the row in which the pulse was detected is known and the timing of the pulse with the accuracy of 250 microseconds is known. As at least one row in which the spot is detected is known the selected search area for the seconds search stage may be determined based on the spot size and the maximum estimated movement of the spot. For example if a spot size is 5*5 pixels and maximum movement of the spot is +-10 pixels, a selected search area to be scan may be a product of sum of a first pulse dimension (5) and maximum movement lines (10) and For example, area of 30 rows may be selected from the calculation of 10*2 + 5*2 = 30 rows which may allow 15 rows above and 15 rows below the row in which the spot was detected at the previous stage.

[0148] The scanning method of the second search stage may be similar to that of the first search stage, however scanning a smaller region, e.g., smaller number of rows, allows reducing the exposure time needed in the second search stage. For example, scanning only 30 rows allows to reduce the exposure time to 32 microseconds as 6 blocks (of 5 rows) multiply by 5 microseconds (of readout time) equals 30 microseconds, and therefore 32 microseconds may be determined as n exposure time or timing accuracy of the second search stage.

[0149] The second search stage may include scanning of a localized sensor area to determine the light spot timing of detection with a second timing accuracy. The second timing accuracy or a second “time window” which refers to a second duration of time, shorter than the first time window concluded from the first search stage. For example, in some embodiments the second timing accuracy may be 32 microseconds. As shown in FIG. 6, the method of detection the light spot during the second search stage may be similar to the process of the first search stage shown in FIG. 4A-4B but with a reduced search area, e.g., instead of 250 lines in the sub area of the first search stage, only 30 lines in the second search stage.

[0150] It should be noted that the process described with reference to FIG. 4A-4B may be generally applicable to the operation illustrated in FIG. 6. Accordingly, unless otherwise indicated, the functional elements, processing steps, and control operations described in connection with FIG. 4A may be similarly implemented in the configuration or method illustrated in FIG. 6. Therefore, only differences relevant to the reduced search area or modified operational parameters of the second search stage are described in detail below. Element 315 of FIG 4A is applicable in FIG. 6 such that an exposure time 316 followed up by a readout time 317 also in diagram 600.

[0151] Timing diagram 600 corresponds to performing the second search stage in a reduced search area. The vertical axis 310 shows the row number within a selected reduced search area, e.g., 0-30 in the exemplary division, while the horizontal axis 311 represents time.

[0152] According to some embodiments of the present disclosure, during the second search stage scanning of a selected reduced search area around the spatial location of the light spot is performed. The scanning of the selected search area may include dividing the selected search to a plurality of blocks and simultaneously scanning the plurality of blocks, while at least one row of each of the plurality of blocks is exposed to light at any given time to ensure that a light spot is detected during operation. In some embodiments, the division or distribution of the selected search into blocks may be determined in accordance with the size of the light spot to be detected. For a light spot occupying an area of XxY pixels, each block may include at least Y rows of the sensor array such that, at any given time, at least one of the Y rows is actively exposed to incident light. The size of each of the plurality of blocks may be determined according to the size of the light spot, e.g., if the height of the spot is 5 pixels, a block of 5 lines may ensure detection of the spot if at any given time at least one line of the block is exposed to sensing light.

[0153] According to embodiments of the disclosure, during the second search stage, the sensor is configured to work in rolling shutter mode, in which the integration time guarantees that at least 1 out of every Y rows is open for exposure at any given moment. With assumption of minimum spot size of 5x5 pixels, at least 1 out of every Y rows is open for exposure at any given moment and therefore the spot will not be missed. The scanning of the reduced area of 30 lines may be performed by a rolling shutter technique with a predetermined exposure time, duration or period 316, e.g., 32 microseconds exposure time. All exposure durations 316 may be identical and may follow by a readout duration 317.

[0154] For example, in order to detect a spot with an exemplary size of 5*5 pixels, at least one row of each block from the reduced area should be open for exposure at any given time. If at any given time at least one row of a block, e.g., one row out of 5 rows is open for exposure, it may ensure detection if a spot arrives within the selected area. Therefore, each first line of each block, e.g., row 1, row 6, row 11 up to row 26 should be exposed to light at the same time and after their exposure time ends the next row at each block should be open for exposure, e.g., row 2, row 7, row 12 and up to row 27. In some embodiments the group of corresponding rows in each of the plurality of blocks, e.g., the group of first rows out of 5 rows may be open for exposure at the exact time. In some embodiments, as shown in the exemplary illustration of FIG 6, there may be a delay in the opening of each group to exposure due to the readout periods 317, as according to certain implementation readouts may not be performed simultaneously. Therefore, each of the corresponding rows from each block may be open in a certain delay from the previous row. For example, row 6 is opened after a duration of a read out from the beginning of the exposure time of row 1, as shown by 422.

[0155] The process begins with a first row of photodetector cells being activated to collect incident light over a defined exposure time, also referred to herein as “integration time period” 316. Upon completion of the integration period for the first row, e.g., 316 (1) the corresponding electrical charge or signal is read out, e.g., 317 (1) while a subsequent row, e.g., row 2, is sequentially exposed, e.g., 316 (2). As shown in timing diagram 600, while a first line (row 1) is being read indicated by 317(1), the next line (row 2) is exposed and there is an overlapping between the readout period of the first line 317(1) and the beginning of the exposure period of the second line 316(2), indicated by element 318.

[0156] The scanning of the reduced selected sensor area or limited region, e.g., 30 rows may repeat during the second search stage until a pulse is being detected. For example, the time required for the second search may equal to a maximum time duration computed by 1 divided by a minimum light pulse frequency, e.g., 125 milliseconds if the light pulse frequency is 8 Hz.

[0157] After a first round of the second search sage, the row in which the pulse was detected is known from the first search stage and a duration between pulses with accuracy of a sum of the first time window (from the first search stage) and the second time window (from the second search stage), e.g., 282 microseconds (250 microseconds from the first search stage and 32 microseconds from the second search stage).

[0158] The second search stage may be repeated for additional search in exactly the same manner one more time which may allow to detect the timing of the next pulse with the accuracy of the second timing accuracy, e.g., 32 microseconds. This may reduce the total accuracy to twice the duration of the second time window or timing accuracy which equals 64 microseconds (32*2 - 64 microseconds).

[0159] FIG. 7 illustrates a schematic representation of timing precision scheme after a first search stage and a second search state in accordance with embodiments disclosed herein. The illustrative timelines in FIG. 7 visualize the timing accuracy after each of the searches stages. It should be noted that, as used herein, the terms ‘timing accuracy’ and ‘time window’ may be used interchangeably and are intended to refer to the same concept, namely the temporal resolution or duration associated with detecting or measuring a light pulse or optical event.

[0160] Timeline 710 shows the timing accuracy or timing window after the first search stage. The exemplary timing accuracy first search stage is 250 microseconds which means that a light pulse may be detected within a time duration of 250 microseconds.

[0161] Timeline 720 shows the timing accuracy or timing window after a single light spot is detected in the second search stage. After a first round of the second search stage is performed, a duration between pulses may have accuracy of a sum of the first time window (from the first search stage) and the second time window (from the second search stage), e.g., 250 + 32 = 282 microseconds (250 microseconds from the first search stage and 32 microseconds from the second search stage).

[0162] Timeline 730 shows the timing accuracy or timing window after two consecutive light spots are detected in the second search stage. The second search stage may be repeated for additional search in exactly the same manner one more time which may allow to detect the timing of the next pulse with the accuracy of the second time window. This may allow for a total accuracy of twice the duration of the second time window. For example, if the second time window equals 32 microseconds the timing accuracy after two consecutive light spots are detected in the second search stage may equal 64 microseconds (32+32 = 64 microseconds). According to some embodiments, the timing accuracy or timing window in which a light pulse may be detected is the sum of timing accuracy of the last two detections.

[0163] Reference is made to FIG. 10 which is a table showing exemplary timing results of a plurality of rounds of fine search stage used in methods for light spot detection in accordance with embodiments disclosed herein. The exemplary timing results shown in table 1000 relate to a basic multi-tap approach with four discrete exposure intervals or “taps”, e.g., as timing diagram 910 of Fig. 9. As shown by table 1000, the fine search stage operation may be repeated number of times to determine the pulse timing with required accuracy. Column 1001 shows the fine search iteration number, Column 1002 represents the time “window” or duration during which a light pulse may be detected. Each entry in this column corresponds to a defined temporal interval within which the imaging system or sensor is configured to detect the presence of an incident light pulse from the field of view. Column 1003 shows the accuracy of the previous iteration and Column 1004 shows the next iteration time window divided by 4. Column 1005 shows accuracy after the current iteration. It should be noted that table 1000 presents an exemplary set of fine search results, illustrating one possible configuration of timing intervals and detection outcomes. The specific timing values shown are provided merely for illustrative purposes, and all numerical values appearing in the table are expressed in milliseconds.

[0164] Reference is made to FIGS. 11A-11B which are tables showing exemplary values of segments codes in a plurality of implementations of fine search stage in accordance with embodiments disclosed herein. FIG.11A shows table 1100 which relates to exemplary multi-tap exposure schemes, including naive multi-tap (4 taps), balanced Gray-coded exposures (9 virtual taps), and balanced Gray-coded with double exposures (virtual 15 taps). According to embodiments of the disclosure, the fine search stage may include controlling the duration of the integration time period of each of the photosensitive elements and the temporal relationship between the integration time period of each of the photosensitive elements, in order to achieve progressively higher detection accuracy with each iteration or round of the fine search.

[0165] As shown in FIG. 9, a plurality of implementations or options to control the duration of the integration time period of each of the photosensitive elements and the temporal relationship between the integration time periods. Table 1100 shows some options of configurations of temporal sampling and exposure encoding which include the representation of each segment in each of the configuration options: basic multi-tap approach with four discrete exposure intervals or “taps” which may relate to timing diagram 910 of FIG. 9, a balanced Gray-coded exposure pattern with 9 discrete exposure intervals or “taps” and a balanced Gray-coded with double exposures per tap with 15 discrete exposure intervals or “taps” which may relate to timing diagram 930 of FIG. 9. It should be noted that these configurations are provided merely as examples, and any other exposure timing or tap arrangement may be used to achieve comparable functionality or performance.

[0166] FIG.1 IB shows the actual binary combinations of each possible segment in a balanced Gray-coded exposure pattern with 9 discrete exposure intervals or “taps” (column 1220) and in a balanced Gray-coded with double exposures per tap with 15 discrete exposure intervals or “taps” (column 1210). Column 1210 relate to timing diagram 930 of FIG. 9. Column 1230 shows the segment number which relates to the segments or “timing intervals” within the total exposure time, e.g., timing intervals 931-945 shown in diagram 930. An exemplary line 1250 shows a temporal pattern or combination of taps “0 1 1 0” where tap 0 =0, tap 1=1, tap 2=1 and tap 3=0. This relates to segment number 3 which corresponds to segment 933 in FIG. 9, therefore the timing of a pulse detected by this temporal pattern relate to timing interval 933 within total exposure time or total integration time 900 in FIG. 9.

[0167] FIG. 12 is a table showing exemplary timing results of a plurality of rounds of fine search stage used in methods for light spot detection in accordance with embodiments disclosed herein. Table 1500 of FIG. 12 shows numerical timing uncertainty reduction across multiple pulse iterations. The first column lists the pulse number, including the initial first search stage and second search stage iterations and subsequent iterations of the fine search stage. The second column presents the timing uncertainty measured in microseconds after each iteration. The table exemplifies how successive iterations enhance the temporal accuracy of pulse detection. Specifically, the high efficiency of the 15 discrete exposure intervals or “taps” which may relate to timing diagram 930 of FIG. 9. As shown, the uncertainty decreases progressively with each additional pulse detection and iteration. As further shown a timing accuracy or precision in this mode of operation during the fine search stage may reach the minimal timing accuracy of 0.096 microseconds after 10 pulses.

[0168] FIG. 13 shows illustrative visual results of methods for light spot detection in accordance with embodiments disclosed herein. Table 1300 shows a representation of segment 14 with relation to the 15 discrete exposure intervals or “taps” which may relate to timing diagram 930 of FIG. 9. The example shown corresponds to Code 14, which is represented in binary form by four bits BIT 1, BIT 2, BIT 3, and BIT 0 having respective binary values of 0, 1, 1, and 1.

[0169] As shown by pixel array 1350 a “light” is detected in lines which corresponds to BIT 2, BIT 3, and BIT 0 while BIT 1 show “no light”, therefore the code which may be detected is the binary code “0 1 1 1” which corresponds to segment 14 within the integration period, e.g., integration time period or total exposure time 900 of FIG. 9. Based on the detection of segment 14 within integration time period 900 of FIG. 9 may relate to the accurate timing of the appearance of the light pulse detected.

[0170] FIG. 14 shows a flowchart of process for light spot detection in accordance with embodiments disclosed herein. Process 1400 shown in FIG. 14, may be implemented, for example, by imaging system 100 of FIGS . 1 A and 2 as described herein. A non-transitory computer readable medium may contain instructions which, when executed by at least one processor, e.g., processor 140 or controller 150 of imaging system 100, may perform the method and operations described at each of the steps in process 1400. In some embodiments, process 1400 may be performed “on- the-fly”, “dynamically”, or in “real time” implying that process 1400 may be performed while images are being captured and processed by a photodetector array e.g., sensor 120 of imaging device 100 of FIGS. 1A and 2.

[0171] Process 1400 illustrates a hierarchical, multi-stage detection methodology in which each successive search stage refines the detection parameters obtained from the preceding stage. This approach allows the system to efficiently narrow the search space, reduce processing time, and improve the precision of light pulse detection.

[0172] Although the stages are illustrated sequentially, it should be understood that each search stage may be executed independently, concurrently, or in any desired order based on operational conditions, system configuration, or control logic. Furthermore, different combinations or subsets of the search stages may be implemented according to application requirements, for example, by omitting, merging, or repeating certain stages to optimize performance, response time, or detection reliability. The configuration shown is therefore exemplary and non-limiting, and other stage arrangements or detection hierarchies may be employed within the scope of the present disclosure.

[0173] In step 1410, a plurality of photosensitive elements of the photodetector array may receive electromagnetic radiation from field of view. In step 1420, each of the plurality of photosensitive elements of the photodetector array may accumulate an electrical charge proportional to an intensity of received electromagnetic radiation during an integration time period.

[0174] Embodiments of the invention may include performing a search on signals converted from the accumulated electrical charge to detect a light pulse appearance with a predefined precision. Performing the search may include performing a plurality of search stages as indicated in blocks 1430, 1450 and 1460.

[0175] In step 1432, a first search stage may be performed by scanning a sensor area to determine a spatial location of the light pulse and a timing of detection thereof with a first timing accuracy.

[0176] As indicated in step 1434, the scanning of the sensor area may include sequentially scanning a plurality of sub-areas within the sensor area until a light pulse is detected within one of the sub-areas with the first timing accuracy. The sequentially scanning of the plurality of the subareas may include iteratively scanning each of the sub-areas. Iteratively scanning of each of the sub-areas may be repeated for a predetermined duration of time or until a light pulse is detected.

[0177] As indicated in step 1436, the iteratively scanning of each of the sub-areas may include dividing each of the sub-areas into a plurality of blocks and simultaneously scanning the plurality of blocks, wherein at least one row of each of the plurality of blocks is exposed to light at any given time. In some embodiments of the disclosure, the size of each of the plurality of blocks may be determined according to a spot size corresponding to the light pulse.

[0178] Upon detection of a light spot in the sensor area, a determination regarding a location of the light pule, e.g., location of a spot created by the light pulse spot may be performed based on one or more image coordinates associated with the illuminated pixels. A detection of a light pulse during the first search stage may further include detection of the arrival time of the detected light pulse with a first timing accuracy, e.g., within a predetermined first exposure period. Once a pulse is detected in the first search stage, the process may continue as indicated by arrow 1444 with a second search stage which is indicated in step 1450. A second search stage may be performed on a reduced sensor area as location of the detected spot is known from the first search stage.

[0179] In step 1455, the second search stage may be performed by scanning a selected search area around the spatial location of the light pulse until another light pulse is detected within the selected search area with a second timing accuracy. The second search stage may be repeated for additional search in exactly the same manner one more time which may allow to detect the timing of the next pulse with the second timing accuracy of the second search stage. The second search stage may be continued until two consecutive light pulses are detected in order to achieve the accuracy of twice the duration of the second time window.

[0180] Following successful second detection in the second stage, a fine search may be executed as indicated in step 1460 to achieve higher temporal precision. The fine search stage may improve the accuracy up to a required predefined precision, e.g., 0.1-3 microseconds. After the second search stage, the pulse timing is known with the timing accuracy of twice the duration of the second timing accuracy, e.g., 64 microseconds. In order to achieve a higher precision and to shorten the timing windows in which a pulse is being detected the fine search stage in being performed iteratively in a cyclic manner while at each iteration the total integration time or total exposure time may be reduced until a defined precision is reached. During the fine search stage as indicated in step 1462, the duration of the integration time period may be controlled for each of the plurality of photosensitive elements and in addition, a temporal relationship between the integration time periods of the plurality of the photosensitive elements may be controlled as well as indicated in step 1466. The temporal relationship between the integration time periods of the photosensitive elements may define a distinct temporal pattern corresponding to each timing interval within the total duration of the integration time period.

[0181] In step 1468, a timing interval in which a light pulse is received from the field of view may be detected by identifying the distinct temporal pattern corresponding to that timing interval. The plurality of distinct temporal patterns may represent respective unique binary codes corresponding to timing intervals, e.g., a unique code for each timing interval within the total exposure time. According to embodiments of the disclosure, detecting the timing interval in which the light pulse is received may include identifying a unique binary code corresponding to that timing interval. For example, if a Gray code or reflected binary code implementation is selected a unique binary code may be correspond to each timing interval such that the binary codes represent two consecutive timing interval may differ by only one bit.

[0182] According to some embodiments, Gray code encoding may be applied during fine search detection process to improve timing precision and robustness in identifying the arrival of a light pulse. Each of the distinct temporal patterns which correspond to a timing interval may be represented by a respective unique binary Gray code. Each timing interval is represented by a unique Gray code that differs from the Gray code assigned to the preceding and succeeding timing intervals. In such configurations, each timing interval, integration window, exposure phase, or virtual tap may be assigned a unique Gray code value representing its temporal position within the detection period. Because Gray code changes only one bit between successive codes, transitions between adjacent timing intervals may be identified unambiguously, reducing timing uncertainty and minimizing decoding errors caused by high-speed signal transitions or noise.

[0183] During fine search operation, the processor may analyze the detected signal in relation to these gray-coded intervals to determine the specific timing window in which the light pulse was received. This enables accurate mapping between the detected pulse and its corresponding timing phase, thereby refining the temporal resolution and improving overall detection accuracy.

[0184] In step 1470, a plurality of iterations of the fine search stage may be performed. In each of the plurality of iterations, the integration time period may be reduced, such that each of the timing intervals within the integration time period is shortened until the light pulse appearance is detected with a predefined precision.

[0185] Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Furthermore, all operations described herein are intended as examples only and other or different operations may be used. Additionally, some of the described method embodiments or elements thereof may occur or be performed at the same point in time.

[0186] Unless otherwise indicated, the functions described hereinabove may be performed by executable code and instructions stored in computer readable medium and running on one or more processor-based systems. Moreover, those skilled in the art will appreciate that the disclosure may be practiced with other computer system configurations, including multiprocessor systems, microprocessor-based electronics, minicomputers, mainframe computers, and the like.

[0187] The terms, “for example”, “e.g.”, “optionally”, as used herein, are intended to be used to introduce non-limiting examples. While certain references are made to certain example system components or algorithms, other components and algorithms can be used as well and / or the example components can be combined into fewer components and / or divided into further components.

[0188] While certain features of the disclosure have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the disclosure.

[0189] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.

Claims

CLAIMS1. A method for detecting a timing interval in which a light pulse is received by a photodetector array, comprising: receiving, by a plurality of photosensitive elements of the photodetector array, electromagnetic radiation from a field of view; accumulating, by each of the plurality of photosensitive elements, an electrical charge proportional to an intensity of received electromagnetic radiation during an integration time period; performing a search on signals converted from the accumulated electrical charge to detect a light pulse appearance with a predefined precision, wherein performing the search comprises performing a fine search stage comprising: controlling the duration of the integration time period for each of the plurality of photosensitive elements and a temporal relationship between the integration time periods of the photosensitive elements, wherein the temporal relationship between the integration time periods of the photosensitive elements defines a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period, and detecting a timing interval in which a light pulse is received from the field of view by identifying the distinct temporal pattern corresponding to that timing interval.

2. The method of claim 1 wherein performing the fine search stage further comprising: performing a plurality of iterations of the fine search stage, wherein in each of the plurality of iterations, the integration time period is reduced, such that each of the timing intervals within the integration time period is shortened until the light pulse appearance is detected with the predefined precision.

3. The method of claim 1, wherein a plurality of distinct temporal patterns represent respective unique binary codes corresponding to timing intervals, and wherein detecting the timing interval in which the light pulse is received comprises identifying a unique binary code corresponding to that timing interval.

4. The method of claim 1 wherein performing the search further comprises performing a first search stage, wherein the first search stage comprising: scanning a sensor area to determine a spatial location of the light pulse and a timing of detection thereof with a first timing accuracy.

5. The method of claim 4, wherein scanning the sensor area comprises sequentially scanning a plurality of sub-areas within the sensor area until a light pulse is detected within one of the subareas with the first timing accuracy.

6. The method of claim 5, wherein sequentially scanning of the plurality of the sub-areas comprises iteratively scanning each of the sub-areas.

7. The method of claim 6, wherein iteratively scanning of each of the sub-areas is repeated for a predetermined duration of time or until a light pulse is detected.

8. The method of claim 6, wherein iteratively scanning each of the sub-areas comprises: dividing each of the sub-areas into a plurality of blocks; and simultaneously scanning the plurality of blocks, wherein at least one row of each of the plurality of blocks is exposed to light at any given time.

9. The method of claim 8, wherein the size of each of the plurality of blocks is determined according to a spot size corresponding to the light pulse.

10. The method of claim 4, wherein the first search stage further comprises scanning a selected search area around the spatial location of the light pulse until another light pulse is detected within the selected search area with a second timing accuracy.

11. A system for detecting a timing interval in which a light pulse is received, the system comprising:a photodetector array comprising a plurality of photosensitive elements configured to receive electromagnetic radiation from a field of view and to accumulate an electrical charge proportional to an intensity of the received electromagnetic radiation during an integration time period; a readout circuit configured to convert the accumulated electrical charge of each of the plurality of photosensitive elements into electrical signals; and a processor configured to: perform a search on the electrical signals to detect an appearance of a light pulse with a predefined precision, the search comprising a fine search stage in which the processor if further configured to: control a duration of an integration time period for each of the plurality of photosensitive elements and a temporal relationship among the integration time periods of the photosensitive elements, wherein the temporal relationship among the integration time periods defines a distinct temporal pattern corresponding to each timing interval within the duration of the integration time period; and detect a timing interval in which the light pulse is received from the field of view by identifying the distinct temporal pattern corresponding to that timing interval.

12. The system of claim 11 wherein the processor is further configured to perform a plurality of iterations of the fine search stage, wherein in each of the plurality of iterations, the processor is to reduce an integration time period such that each of a plurality of timing intervals within the integration time period is shortened until an appearance of the light pulse is detected with the predefined precision.

13. The system of claim 11, wherein a plurality of distinct temporal patterns represent respective unique binary codes corresponding to timing intervals, and wherein detecting the timing interval in which the light pulse is received comprises identifying a unique binary code corresponding to that timing interval.

14. The system of claim 11, wherein the processor is further configured to perform a first search stage, during the first search stage the processor is configured to:scan a sensor area to determine a spatial location of the light pulse and a timing of detection thereof with a first timing accuracy15. The system of claim 14, wherein the processor is configured to perform sequentially scanning a plurality of sub-areas within the sensor area until a light pulse is detected within one of the sub-areas with the first timing accuracy.

16. The system of claim 15, wherein the sequentially scanning of the plurality of the sub-areas comprises iteratively scanning each of the sub-areas.

17. The system of claim 16, wherein the processor is configured to repeat the iteratively scanning each of the plurality of sub-areas for a predetermined duration of time or until a light pulse is detected.

18. The system of claim 16, wherein during the iteratively scanning, the processor is configured to: divide each of the plurality of sub-areas into a plurality of blocks; and simultaneously scan the plurality of blocks such that at least one row of each block is exposed to light at any given time19. The system of claim 18, wherein the size of each of the plurality of blocks is determined according to a spot size corresponding to the light pulse.

20. The system of claim 14, wherein during the first search stage the processor is further configured to scan a selected search area around the spatial location of the light pulse until another light pulse is detected within the selected search area with a second timing accuracy.

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