Electro-optical system, method for generating image information, and computer-readable medium

Abstract

Disclosed are an electro-optical system, a method for generating image information, and a computer-readable medium, relating to electro-optical devices and lasers used in infrared photonics. The system comprises: a photodetector array (PDA) including a plurality of photosensitive sites (PS), each PS being operable to output a plurality of detection signals in a plurality of different frames, the detection signal output by the corresponding PS for a frame indicating the amount of light impinging on the corresponding PS during a corresponding frame exposure time (FET); an availability filtering module being operable to first determine, for each of the plurality of photosensitive sites, that the photosensitive site is unavailable based on a first FET, and later determine that the PS is available based on a second FET shorter than the first FET; and a processor being operable to generate a plurality of images based on a plurality of frame detection levels of the plurality of PSs.

Description

[0001] This application is a divisional application of application number 202080005868.4 (PCT application number PCT / IB2020 / 060011), application date October 24, 2020, and invention name “Photonic Systems and Methods”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application is related to and claims priority from U.S. patent application No. 16 / 662,665 filed on October 24, 2019, and U.S. provisional patent application Nos. 63 / 075426 filed on September 8, 2020, 63 / 093,945 filed on October 20, 2020, and 63 / 094,913 filed on October 22, 2020, all of which are incorporated herein by reference in their entirety. Technical Field

[0004] The present disclosure relates to photonic systems, methods, and computer program products. More particularly, the present disclosure relates to electro-optical devices and lasers used in infrared (IR) photons. Background Art

[0005] A photodetection device such as a photodetector array (also referred to as a "photosensor array") includes a multitude of photosites, each of which includes one or more photodiodes and a capacitor, wherein the one or more photodiodes are used to detect impinging light and the capacitor is used to store the charge provided by the photodiode. The capacitor can be implemented as a dedicated capacitor and / or using the parasitic capacitance of the photodiode, transistor and / or other components of the PS. Hereinafter, in this specification and for simplicity, the term "photodetecting device" is often replaced by the abbreviation "PDD", the term "photodetector array" is often replaced by the abbreviation "PDA", and the term "photodiode" is often replaced by the abbreviation "PD".

[0006] The term "photosite" relates to a single sensor element (also called a "sensel", such as a combination of the words "sensor" and "cell" or "sensor" and "element") in an array of multiple sensors, and is also called a "sensor element", "photosensor element", "photodetector element", etc. In the following, "photosite" is generally replaced by the abbreviation "PS". Each PS may include: one or more PDs (for example, if a color filter array is implemented, multiple PDs that detect light in different parts of the spectrum may optionally be collectively referred to as a single PS). In addition to the PD, the PS may also include: some circuits or multiple additional components.

[0007] Dark current is a well-known phenomenon when referring to many PDs. It refers to the current that flows through the PD even when no photons enter the device. Dark current in many PDs can be caused by the random generation of electrons and holes in a depletion region of the PD.

[0008] In some cases, it is desirable to provide photosensitive sites with photodiodes characterized by a relatively high dark current while implementing capacitors of limited size. In some cases, it is desirable to provide PSs with PDs characterized by a relatively high dark current while reducing the effect of dark current on an output detection signal. In PSs characterized by high dark current accumulation, it is desirable and beneficial to overcome the detrimental effects of dark current on electro-optical systems. Hereinafter and for simplicity, the term "electrooptical" may be replaced with the abbreviation "EO."

[0009] Shortwave infrared (SWIR) imaging enables a range of applications that are difficult to perform using visible light imaging. These applications include electronic board inspection, solar cell inspection, product inspection, gated imaging, identification and sorting, surveillance, anti-counterfeiting, process quality control, and more. Many existing SWIR imaging systems based on indium gallium arsenide (InGaAs) are expensive to manufacture and currently suffer from limited manufacturing capacity.

[0010] Therefore, it would be beneficial to be able to provide a SWIR imaging system using more cost-effective photoreceivers based on PDs that can be more easily integrated into surrounding electronics. Summary of the Invention

[0011] According to one aspect of the present disclosure, an active SWIR imaging system is provided, comprising: a pulsed illumination source operable to emit a plurality of SWIR radiation pulses toward a target, the plurality of radiation pulses impinging on the target causing a plurality of reflected SWIR radiation pulses to be reflected from the target; an imaging receiver comprising a plurality of germanium (Ge) PDs operable to detect the reflected SWIR radiation, wherein the imaging receiver generates for each Ge PD a respective detection signal representative of the reflected SWIR radiation impinging on the respective Ge PD, the detection signal being greater than 50 μA / cm2. 2 ) a dark current, time dependent dark current noise, and time independent readout noise; and a controller operable to control activation of the imaging receptor during an integration time, wherein an accumulated dark current noise during the integration time does not exceed the time independent readout noise.

[0012] According to one aspect of the present disclosure, a method for generating multiple SWIR images of multiple objects in a field of view (FOV) of an EO system is disclosed, the method comprising: transmitting at least one illumination pulse toward the FOV to cause SWIR radiation to be reflected from at least one target; triggering continuous signal acquisition initiated by an imaging receiver, the imaging receiver comprising a plurality of germanium PDs operable to detect the reflected SWIR radiation; collecting, for each of the plurality of germanium PDs, a charge greater than 50 μA / cm3 that is caused by at least the SWIR reflected radiation impinging on the corresponding germanium PD due to the triggering; 2 dark current, dark current noise related to the integration time, and readout noise unrelated to the integration time; triggering to stop the collection of the charge when the amount of charge collected due to the dark current noise is still lower than the amount of charge collected due to the readout noise unrelated to the integration time; and generating an image of the FOV based on the multiple charge levels collected by each of the multiple germanium PDs.

[0013] According to one aspect of the present disclosure, a SWIR optical system is disclosed, the SWIR system including a passive Q-switched laser (also referred to herein as a "P-QS laser"), the passive Q-switched laser including: a gain medium including a gain medium crystalline (GMC) material, the gain medium crystalline material being ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG); a saturable absorber (SA) rigidly connected to the gain medium, the SA including a ceramic SA crystalline material selected from a group of multiple doped ceramic materials consisting of: V3+:YAG and multiple divalent cobalt-doped crystalline materials; and an optical cavity, the gain medium and the SA being located in the optical cavity, the optical cavity including a high reflectivity mirror and an output coupler.

[0014] Hereinafter in this description and for the sake of simplicity, the term "saturable absorber" is often replaced by the abbreviation "SA".

[0015] According to one aspect of the present disclosure, a SWIR optical system is disclosed, comprising a P-QS laser, the P-QS laser comprising: a gain medium comprising a GMC material, wherein the GMC material is ceramic Nd:YAG; an SA rigidly connected to the gain medium, wherein the SA comprises a ceramic SA crystalline material, wherein the ceramic SA crystalline material is selected from a group of multiple doped ceramic materials consisting of the following materials: V3+:YAG and multiple divalent cobalt-doped crystalline materials; and an optical cavity, wherein the gain medium and the SA are located in the optical cavity, wherein the optical cavity comprises a high-reflectivity mirror and an output coupler.

[0016] According to one aspect of the present disclosure, a SWIR optical system is disclosed, which includes a P-QS laser, the P-QS laser including: a gain medium, the gain medium including a ceramic GMC material, the ceramic GMC material being a ceramic neodymium-doped rare earth element crystal; an SA rigidly connected to the gain medium, the SA including a ceramic SA crystalline material, the ceramic SA crystalline material being selected from a group consisting of a plurality of doped crystalline materials consisting of the following materials: V3+:YAG and a plurality of cobalt-doped crystalline materials; and an optical cavity, the gain medium and the SA being located in the optical cavity, the optical cavity including a high-reflectivity mirror and an output coupler.

[0017] According to one aspect of the present disclosure, a method for fabricating components of a P-QS laser is disclosed, the method comprising: inserting at least one first powder into a first mold; compacting the at least one first powder in the first mold to produce a first green compact; inserting at least one second powder different from the at least one first powder into a second mold; compacting the at least one second powder in the second mold to produce a second green compact; heating the first green compact to produce a first crystalline material; heating the second green compact to produce a second crystalline material; and connecting the second crystalline material to the first crystalline material. In such a case, one of the first and second crystalline materials is a neodymium-doped crystalline material and is a gain medium for the P-QS laser, and the other of the first and second crystalline materials is a SA for the P-QS laser and is selected from a group of crystalline materials consisting of a neodymium-doped crystalline material and a doped crystalline material, the latter being selected from a group of doped crystalline materials consisting of V3+:YAG and multiple cobalt-doped crystalline materials. Likewise, in such a case, at least one of the gain medium and the SA is a ceramic crystalline material.

[0018] According to one aspect of the present disclosure, a PDD is disclosed, comprising: an active PS including an active PD; a reference PS including a reference PD; a first voltage-controlled current circuit composed of a voltage-controlled current source (VCS) or a voltage-controlled current sink (VCS), the first voltage-controlled current circuit being connected to the active PD; and a control voltage generating circuit connected to the active voltage-controlled current circuit and the reference PS and being used to provide a control voltage to the voltage-controlled current circuit, the control voltage having a voltage level that is responsive to a dark current of the reference PD to reduce an effect of the dark current of the active PD on an output of the active PS.

[0019] According to one aspect of the present disclosure, a method for reducing multiple effects of dark current in a PDD is disclosed, the method comprising: determining a first control voltage based on the dark current of at least one reference PD of the PDD when the PDD is operating at a first temperature; providing the first control voltage to a first voltage-controlled current circuit of at least one active PD of an active PS connected to the PDD, thereby causing the first voltage-controlled current circuit to apply a first dark current-resisting current in the active PS; generating a first detection current by the active PD in response to light impinging on the active PD from an object in a field of view of the PDD and the dark current generated by the active PD; and outputting a first detection signal by the active PS, the amplitude of the first detection signal being less than the first detection current, in response to the first detection current and the first The invention further comprises: providing a dark current suppressing current to compensate for the effect of dark current on the first detection signal; determining a second control voltage based on the dark current of at least one reference PD of the PDD when the PDD operates at a second temperature that is at least 10 degrees Celsius (°C) higher than the first temperature; providing the second control voltage to the first voltage-controlled current circuit, thereby causing the first voltage-controlled current circuit to apply a second dark current suppressing current in the active PS; generating a second detection current by the active PD in response to light impinging on the active PD from the object and the dark current generated by the active PD; and outputting a second detection signal by the active PS, the second detection signal having a magnitude less than the second detection current, in response to the second detection current and the second dark current suppressing current, thereby suppressing the effect of dark current on the second detection signal. In such a case, the magnitude of the second dark current suppressing current is greater than the magnitude of the first dark current suppressing current by a factor of at least two.

[0020] According to one aspect of the present disclosure, a method for testing a power supply device (PD) is disclosed, the method comprising: providing a first voltage to a first input of an amplifier of a control voltage generating circuit, wherein a second input of the amplifier is coupled to a reference power supply (PD) and a second current circuit, the second current circuit supplying a current at a level, the current being commanded in response to an output voltage of the amplifier, thereby causing the amplifier to generate a first control voltage for a first current circuit of a power supply (PS) of the PDD; reading a first output signal of the PS, the first output signal being generated by the PS in response to the current generated by the first current circuit and a power supply (PD) of the PS; providing a second voltage different from the first voltage to the first input of the amplifier, thereby causing the amplifier to generate a second control voltage for the first current circuit; reading a second output signal of the PS, the second output signal being generated by the PS in response to the current generated by the first current circuit and a power supply (PD) of the PS; and determining a defect state of a detection path of the PDD based on the first and second output signals, the detection path comprising the PS and a readout circuit associated with the PS.

[0021] According to one aspect of the present disclosure, a system for generating multiple images is disclosed, the system including: a processor, the processor being configured to: receive multiple detection results of an object from a PDA, the object including a high-reflectivity surface surrounded by multiple low-reflectivity surfaces on all sides, the multiple detection results including first frame information of the object detected by the PDA during a first frame exposure time, and second frame information of the object detected by the PDA during a second frame exposure time, the second frame exposure time being longer than the first frame exposure time; process the first frame information based on the first frame exposure time to provide a first image, the first image including a bright area representing the high-reflectivity surface, the bright area being surrounded by a dark background representing the multiple low-reflectivity surfaces; and process the second frame information based on the second frame exposure time to provide a second image, the second image including a dark background without a bright area.

[0022] According to one aspect of the present disclosure, a system for generating multiple images is disclosed, the system including: a processor, the processor being configured to: receive multiple detection results of an object from a PDA, the object including a high-reflectivity surface surrounded by multiple low-reflectivity surfaces on all sides, the multiple detection results including first frame information of the object detected by the PDA during a first frame exposure time, and second frame information of the object detected by the PDA during a second frame exposure time, the second frame exposure time being longer than the first frame exposure time; process the first frame information based on the first frame exposure time to provide a first image, the first image including a bright area representing the high-reflectivity surface, the bright area being surrounded by a dark background representing the multiple low-reflectivity surfaces; and process the second frame information based on the second frame exposure time to provide a second image, the second image including a dark background without a bright area.

[0023] According to one aspect of the present disclosure, a method for generating image information based on data from a PDA is disclosed, the method comprising: receiving first frame information of a low-reflectivity target including a high-reflectivity area from a PDA, the first frame information indicating multiple light intensities of multiple different parts of the target detected by the PDA during a first frame exposure time; processing the first frame information based on the first frame exposure time to provide a first image, the first image including a bright area surrounded by a dark background; receiving second frame information of the low-reflectivity target including the high-reflectivity area from the PDA, the second frame information indicating multiple light intensities of the multiple different parts of the target detected by the PDA during a second frame exposure time, the second frame exposure time being longer than the first frame exposure time; and processing the second frame information based on the second frame exposure time to provide a second image, the second image including a dark background without a bright area.

[0024] According to one aspect of the present disclosure, a non-transitory computer-readable medium is disclosed for generating image information based on data of a PDA, the non-transitory computer-readable medium including a plurality of instructions stored thereon, and when the plurality of instructions are executed on a processor, the following steps are performed: receiving a first frame information of a black target including a white area from a PDA, the first frame information indicating a plurality of light intensities of a plurality of different parts of the target detected by the PDA during a first frame exposure time; processing the first frame information based on the first frame exposure time to provide a first image, the first image including a bright area surrounded by a dark background; receiving a second frame information of the black target including the white area from the PDA, the second frame information indicating a plurality of indicated light intensities of the plurality of different parts of the target detected by the PDA during a second frame exposure time, the second frame exposure time being longer than the first frame exposure time; and processing the second frame information based on the second frame exposure time to provide a second image, the second image including a dark background without a bright area.

[0025] According to one aspect of the present disclosure, an EO system with dynamic PS availability assessment is disclosed, the system comprising: a photosensitive area device (PDA) including a plurality of photosensitive sites (PSs), each PS operable to output a plurality of detection signals in a plurality of different frames, the detection signals output by the corresponding PS for a frame indicating the amount of light impinging on the corresponding PS in the corresponding frame; an availability filter module operable to determine, for each PS, that the PS is unavailable based on a first frame exposure time, and later determine that the PS is available based on a second frame exposure time, the second frame exposure time being shorter than the first frame exposure time; and a processor operable to generate a plurality of images based on a plurality of frame detection levels of the plurality of PSs. The processor is configured to: (i) exclude a first detection signal of a filtered PS determined by the availability filter module to be unavailable for the first image when generating a first image based on the plurality of first frame detection levels, and (ii) include a second detection signal of the filtered PS determined by the availability filter module to be available for the second image when generating a second image based on the plurality of second frame detection levels captured by the PDA after capturing the plurality of first frame detection levels.

[0026] According to one aspect of the present disclosure, a method for generating image information based on data of a PDA is disclosed, the method comprising: receiving first frame information, the first frame information comprising a first frame detection level for each of a plurality of PSs of the PDA, the first frame detection level indicating a light intensity detected by the respective PSs during a first frame exposure time; identifying, based on the first frame exposure time, from the plurality of PSs of the PDD: a first available PS group comprising a first PS, a second PS and a third PS, and a first unavailable PS group comprising a fourth PS; disregarding the plurality of first frame detection levels of the first unavailable PS group, and generating a first image based on the plurality of first frame detection levels of the first available PS group; after receiving the first frame information, determining a second frame exposure time, the second frame exposure time being longer than the first frame exposure time; receiving second frame information, the second frame information comprising a second frame detection level for each of the plurality of PSs of the PDA, the second frame detection level indicating a light intensity detected by the respective PSs during a second frame exposure time; based on the second frame exposure time, identifying, from the plurality of PSs of the PDD (g) ignoring a plurality of second frame detection levels of the second unavailable PS group and generating a second image based on the plurality of second frame detection levels of the second available PS group; after receiving the second frame information, determining a third frame exposure time, the third frame exposure time being longer than the first frame exposure time and shorter than the second frame exposure time; receiving the third frame information, the third frame information including the exposure time for the P a third frame detection level for each of the multiple PSs of the DA, the third frame detection level indicating a light intensity detected by the respective PS during a third frame exposure time; identifying, based on the third frame exposure time, from the multiple PSs of the PDD: a third available PS group, including the first PS and the second PS, and a third unavailable PS group, including the third PS and the fourth PS; and (k) ignoring the multiple third frame detection levels of the third unavailable PS group, generating a third image based on the multiple third frame detection levels of the third available PS group.

[0027] According to one aspect of the present disclosure, a non-transitory computer-readable medium is disclosed for generating image information based on data from a photodetector array (PDA). The non-transitory computer-readable medium includes a plurality of instructions stored thereon. When the plurality of instructions are executed on a processor, the following steps are performed: receiving first frame information, the first frame information including a first frame detection level for each of a plurality of PSs of the PDA, the first frame detection level indicating a light intensity detected by the respective PS during a first frame exposure time; identifying, from the plurality of PSs of the PDD based on the first frame exposure time: a first available A PS group includes a first PS, a second PS and a third PS, and a first unavailable PS group includes a fourth PS; ignoring a plurality of first frame detection levels of the first unavailable PS group, generating a first image based on the first frame detection level of the first available PS group; determining a second frame exposure time after receiving the first frame information, the second frame exposure time being longer than the first frame exposure time; receiving second frame information, the second frame information including a second frame detection level for each of the plurality of PSs of the PDA, the second frame detection level indicating the second frame detection level of each PS during the second frame exposure time by the PDA; a light intensity detected by each PS; based on the second frame exposure time, identifying from the multiple PSs of the PDD: a second available PS group including the first PS, and a second unavailable PS group including the second PS, the third PS, and the fourth PS; ignoring the multiple second frame detection levels of the second unavailable PS group, and generating a second image based on the multiple second frame detection levels of the second available PS group; after receiving the second frame information, determining a third frame exposure time, the third frame exposure time being longer than the first frame exposure time and shorter than the second frame exposure time; receiving the third frame information , the third frame information includes a third frame detection level for each of the multiple PSs of the PDA, and the third frame detection level indicates a light intensity detected by the respective PS during a third frame exposure time; based on the third frame exposure time, identifying from the multiple PSs of the PDD: a third available PS group, including the first PS and the second PS, and a third unavailable PS group, including the third PS and the fourth PS; and ignoring multiple third frame detection levels of the third unavailable PS group, generating a third image based on the multiple third frame detection levels of the third available PS group.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The following description of non-limiting examples of the embodiments disclosed herein is based on the following figures listed after this paragraph. The same structure, element, or component that appears in more than one figure may be labeled with the same number in all figures in which it appears. The figures and description are intended to illustrate and clarify the embodiments disclosed herein and should not be considered limiting in any way. All figures show apparatus or flow diagrams according to various examples of the presently disclosed subject matter. In the drawings:

[0030] Figure 1A 、 Figure 1B and Figure 1C are schematic block diagrams illustrating active SWIR imaging systems.

[0031] Figure 2 is an exemplary graph illustrating the relative magnitude of noise power after different durations of multiple integration times in a SWIR imaging system;

[0032] Figure 3A 、 Figure 3B and Figure 3C A flowchart and schematic diagrams respectively illustrate a method of operating an active SWIR imaging system according to some embodiments;

[0033] Figure 4A 、 Figure 4B and Figure 4C A flow chart and schematic diagrams each illustrating an exemplary method of operating an active SWIR imaging system;

[0034] Figure 5 is a flow chart illustrating a method for generating multiple SWIR images of multiple objects in a FOV of an EO system;

[0035] Figure 6 is a schematic functional block diagram illustrating an example of a SWIR optical system.

[0036] Figure 7A 、 Figure 7B and Figure 7C are schematic functional block diagrams illustrating examples of P-QS lasers.

[0037] Figure 8 and Figure 9 1 and 2 illustrate schematic functional diagrams of a SWIR optical system.

[0038] Figure 10 is a schematic functional block diagram illustrating an example of a SWIR optical system.

[0039] Figure 11A 、 Figure 11B and Figure 11CA flow chart illustrating an example of a method for fabricating components of a P-QS laser and conceptual timelines for performing the method are shown, respectively.

[0040] Figure 12A Schematically showing a PS including a PD, wherein the PD is controlled by a voltage-controlled current source;

[0041] Figure 12B Schematically shows a PS including a PD controlled by a voltage-controlled current source in a "3T" structure;

[0042] Figure 13A and Figure 13B A PDD is shown that includes a PS and circuitry operable to reduce the effects of dark current.

[0043] Figure 13C A PDD is shown, comprising a plurality of PSs and circuitry operable to reduce the effects of dark current;

[0044] Figure 14 An exemplary PDIV curve and possible operating voltages of a PDD are shown;

[0045] Figure 15 A control voltage generating circuit is shown, wherein the control voltage generating circuit is connected to a plurality of reference photosensitive sites;

[0046] Figure 16A and Figure 16B A plurality of PDDs are shown, the plurality of PDDs comprising an array of a plurality of PSs and a reference circuit based on a plurality of PDs;

[0047] Figure 17 and Figure 18 A plurality of PDDs are shown, each PDD including a PS and circuitry operable to reduce the effects of dark current;

[0048] Figure 19 A PDD is illustrated, the PDD including an optical device, a processor, and a plurality of additional components;

[0049] Figure 20 is a flow chart illustrating a method for compensating for dark current in a photodetector;

[0050] Figure 21 is a flow chart illustrating a method for compensating for dark current in a photodetector;

[0051] Figure 22 is a flow chart illustrating a method for testing a photodetector;

[0052] Figure 23 To illustrate an EO system according to some embodiments;

[0053] Figure 24 An example of a method for generating image information based on data from a PDA is illustrated;

[0054] Figure 25 and Figure 26 A flow chart illustrating a method for generating a model for PDA operation at different frame exposure times and a graphical representation of the method being performed for different frames of the same scene captured at different frame exposure times are respectively shown;

[0055] Figure 27 is a flow chart illustrating an example of a method for generating multiple images based on different subsets of multiple PSs under different operating conditions;

[0056] Figure 28A and 28B An EO system and a plurality of exemplary target objects are illustrated;

[0057] Figure 29 The present invention is a flow chart illustrating a method for generating image information based on data of a PDA.

[0058] It will be understood that, for simplicity and clarity of illustration, the elements shown in the drawings are not necessarily drawn to scale. For example, the dimensions of some elements may be exaggerated relative to other elements for clarity. Furthermore, where deemed appropriate, reference numerals may be repeated across the drawings to indicate corresponding or similar elements. DETAILED DESCRIPTION

[0059] In the following detailed description, many specific details are set forth to provide a thorough understanding of the present disclosure. However, it will be understood by those skilled in the art that the present disclosure can be practiced without these specific details. In other cases, known methods, processes, and components are not described in detail to avoid confusing the present disclosure.

[0060] In the drawings and description set forth, like reference numerals indicate those elements that are common to the different embodiments or configurations.

[0061] Unless otherwise specifically stated, it will be apparent from the following discussion that it is understood that throughout the specification discussions, the use of terms such as "processing," "calculating," "computing," "determining," "generating," "setting," "configuring," "selecting," "defining," etc. include the actions and / or processes of a computer that manipulate and / or transform data into other data, where the data is represented as physical quantities, such as multiple electronic quantities, and / or data representing such multiple physical objects.

[0062] The terms "computer," "processor," and "controller" should be broadly interpreted to cover any type of electronic device with data processing capabilities, including, by way of non-limiting example, a personal computer, a server, a computing system, a communication device, a processor (such as a digital signal processor (DSP), a microcontroller, a field programmable gate array (FPGA), an application-specific integrated circuit, etc.), any other electronic computing device, or any combination thereof.

[0063] Operations according to the teachings herein may be performed by a computer specially constructed for the desired purposes or by a general-purpose computer specially configured for the desired purposes, via a computer program stored in a computer-readable storage medium.

[0064] As used herein, the phrases "for example," "such as," "for instance," and variations thereof describe numerous non-limiting embodiments of the presently disclosed subject matter. Reference in the specification to "one case," "some cases," "other cases," or variations thereof means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the presently disclosed subject matter. Thus, the appearance of the phrases "one case," "some cases," "other cases," or variations thereof are not necessarily referring to the same embodiment(s).

[0065] It should be understood that certain features of the presently disclosed subject matter that, for the sake of clarity, are described in the context of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the presently disclosed subject matter that, for the sake of brevity, are described in the context of a single embodiment may also be provided individually or in any suitable subcombination.

[0066] In various embodiments of the presently disclosed subject matter, one or more phases or steps illustrated in the accompanying drawings may be performed in a different order and / or one or more groups of phases may be performed simultaneously, or vice versa. The accompanying drawings illustrate a general schematic diagram of a system architecture according to an embodiment of the presently disclosed subject matter. Each module in the accompanying drawings may be composed of any combination of software, hardware, and / or firmware that performs the functions defined and explained herein. The modules in the accompanying drawings may be centralized in one location or distributed in more than one location.

[0067] Any reference in the specification to a method should be applied mutatis mutandis to a system capable of performing the method and should be applied mutatis mutandis to a non-transitory computer-readable medium storing instructions that, once executed by a computer, cause the method to be performed.

[0068] Any reference in the specification to a system should be applied mutatis mutandis to a method executable by the system and should be applied mutatis mutandis to a non-transitory computer-readable medium storing instructions executable by the system.

[0069] Any reference in the specification to a non-transitory computer-readable medium or similar terms should be applied mutatis mutandis to the ability to execute the instructions stored in the non-transitory computer-readable medium and to methods executable by a computer that reads the instructions stored in the non-transitory computer-readable medium.

[0070] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The materials, methods, and examples provided herein are illustrative only and not intended to be limiting.

[0071] The implementation of the method and system of the present disclosure involves manual, automatic or a combination thereof to perform or complete certain selected tasks or steps. Moreover, according to the actual instruments and equipment of the preferred embodiments of the method and system of the present disclosure, several selected steps can be implemented by hardware or by software on any operating system of any firmware or a combination thereof. For example: as hardware, multiple selected steps of the present disclosure can be implemented as a chip or a circuit. As software, multiple selected steps of the present disclosure can be implemented as multiple software instructions executed by a computer using any suitable operating system. In any case, multiple selected steps of the method and system of the present disclosure can be described as being performed by a data processor, such as a computing platform for executing multiple instructions.

[0072] Figure 1A 、 Figure 1B and Figure 1C are schematic block diagrams illustrating active SWIR imaging systems 100 , 100 ′, and 100 ″, respectively, according to examples of the presently disclosed subject matter.

[0073] As used herein, an "active" imaging system is operable to detect light reaching the system from its field of view (FOV), detect it by an imaging receiver comprising a plurality of PDs, and process the plurality of detection signals to provide one or more images of the FOV or a portion thereof. The term "image" means a digital representation of a scene detected by the imaging system, the imaging system storing a color value for each element (pixel) in the image, each pixel color representing light reaching the imaging system from a different part of the FOV (e.g., a 0.02° by 0.02° portion of the FOV, depending on the receiver optics). It is noted that, optionally, the imaging system can also be operated to generate other representations of objects or light in the FOV (e.g., a depth map, 3D model, polygonal mesh), but the term "image" means a two-dimensional (2D) image without depth data.

[0074] The system 100 includes an illumination source (IS) 102 operable to emit a plurality of radiation pulses in the SWIR band toward one or more targets 104, causing reflected radiation from the objects to be reflected back in the direction of the system 100. Figure 1A, outgoing illumination is designated 106, and illumination reflected toward system 100 is designated 108. Portions of the emitted radiation may also be reflected in other directions, deflected, or absorbed by the target. The term "target" refers to any object within the FOV of the imaging sensor, such as solid, liquid, flexible, and rigid objects. Some non-limiting examples of such objects include vehicles, roads, people, animals, plants, buildings, electronic devices, clouds, microscopic samples, items under manufacture, and the like. Any suitable type of illumination source 102 may be used, such as one or more lasers, one or more light emitting diodes (LEDs), one or more impact flashes, any combination thereof, and the like. As discussed in more detail below, illumination source 102 may optionally include one or more active lasers, or one or more P-QS lasers.

[0075] System 100 also includes at least one imaging receiver (or simply "receiver") 110, comprising a plurality of germanium (Ge) PDs operable to detect the reflected SWIR radiation. The receiver generates an electrical signal for each of the Ge PDs, representing the amount of impinging SWIR light within its detectable spectral range. The signal includes the amount of SWIR radiation pulses reflected from the target and may also include additional SWIR light (e.g., arriving from the sun or an external light source).

[0076] The term "germanium PD (Ge PD)" refers to any PD in which light-induced electron excitation (later detectable as a photocurrent) occurs within the germanium, within a germanium alloy (e.g., SiGe), or at the interface between germanium (or a germanium alloy) and another material (e.g., silicon, SiGe). Specifically, the term "germanium PD" refers to both pure germanium PDs and germanium-silicon PDs. When germanium PDs comprising both germanium and silicon are used, varying concentrations of germanium can be used. For example, the relative fraction of germanium in the germanium PD (whether alloyed with or adjacent to silicon) can range from 5% to 99%. For example, the relative fraction of germanium in multiple germanium PDs can range from 15% to 40%. It should be noted that materials other than silicon can also be part of the germanium PD, such as aluminum, nickel, silicide, or any other suitable material. In some implementations of the present disclosure, the multiple germanium PDs can be pure germanium PDs (comprising greater than 99.0% germanium).

[0077] It should be noted that the receiver can be implemented as a PDA fabricated on a single chip. Any of the PD arrays discussed throughout this disclosure can be used as receiver 110. The germanium PDs can be arranged in any suitable configuration, such as a rectangular matrix (straight rows and columns of germanium PDs), honeycomb tiling, or even an irregular configuration. Preferably, the number of germanium PDs in the receiver allows for the generation of high-resolution images. For example, the number of PDs can be on the order of 1 megapixel, 10 megapixels, or more.

[0078] In some embodiments, receiver 110 has the following specifications:

[0079] a.HFOV (horizontal field of view) [m]: 60

[0080] b.WD (working distance) [m]: 150

[0081] c.Pixel size [um]: 10

[0082] d. Resolution (on target) [mm]: 58

[0083] e. Pixel #[H]: 1,050

[0084] f. Pixel #[V]: 1112

[0085] g. Aspect ratio: 3:1

[0086] h. Viewing angle [rad]: 0.4

[0087] i. Target reflectivity [%]: 10%

[0088] j. Collection (ratio of collected photons to emitted photons assuming 100% target reflectivity and Lambertian reflectivity): 3e -9 .

[0089] In addition to the impinging SWIR light as described above, the electrical signal generated by each of the plurality of germanium PDs also represents:

[0090] a. Readout noise, which is random and has an amplitude that is independent (or substantially independent) of the integration time. Examples of this noise include Nyquist-Johnson noise (also known as thermal noise or kTC noise). In addition to statistical components, the readout process can also introduce a DC component into the signal, but the term "readout noise" refers to the random component of the signal introduced by the readout process.

[0091] b. Dark current noise, which is random and accumulates over the integration time (i.e., it depends on the integration time). In addition to the statistical component, the dark current will also have a DC component (which may or may not be eliminated, such as for example Figures 12A to 22 is discussed) is introduced into the signal, but the term "dark current noise" belongs to the random component of the signal that is accumulated during the integration time by dark current.

[0092] Some germanium PDs, particularly those that combine germanium with another material such as silicon, are characterized by a relatively high level of dark current. For example, the dark current for many germanium PDs may be greater than 50 μA / cm 2 (related to a surface area of the PD), or even larger (e.g., greater than 100 μA / cm 2 , greater than 200μA / cm 2 or greater than 500μA / cm 2 Depending on the surface area of the PD, such levels of dark current can translate to 50 picoamperes (pA) per Ge PD or higher (e.g., over 100 pA per Ge PD, over 200 pA per Ge PD, over 500 pA per Ge PD, or over 2 nA per Ge PD). It should be noted that PDs of different sizes can be used, such as approximately 10 mm 2 , about 50mm 2 , about 100mm 2 , about 500mm 2 It is noted that when the plurality of Ge PDs are subjected to different levels of nonzero bias, the plurality of Ge PDs may generate dark currents of different magnitudes (which may result in, for example, a dark current greater than 50 picoamperes in each of the plurality of Ge PDs).

[0093] System 100 also includes a controller 112 and an image processor 114. The controller 112 controls the operation of the receiver 110 (and optionally also the illumination source (IS) 102 and / or other components). Thus, the controller 112 is configured to control the activation of the receiver 110 during a relatively short integration time, thereby limiting the impact of accumulated dark current noise on signal quality. For example, the controller 112 can be operable to control the activation of the receiver 110 during an integration time during which the accumulated dark current noise does not exceed the readout noise irrelevant to the integration time.

[0094] Now refer to Figure 2 , Figure 2is an exemplary graph illustrating the relative magnitude of noise power after various durations of integration time according to various examples of the presently disclosed subject matter. For a given laser pulse energy, the signal-to-noise ratio (SNR) is primarily determined by the noise level, which includes the dark current noise (the noise of the dark photocurrent) and thermal noise (also known as kTC noise). Figure 2 As shown in the exemplary graph of FIG, depending on the integration time of the germanium-based receiver 110, the dark current noise or the thermal noise dominates the SNR of the electrical signal of the PD. Figure 2 The activation time of the germanium photodetector is limited to within the range designated as "A" in the receiver. Therefore, not too many electrons from the dark current noise are collected, so the SNR is improved and is therefore mainly affected by thermal noise. For a longer receiver integration time, the noise from the dark current of the germanium photodetector will exceed the thermal noise in affecting the receiver SNR, causing receiver performance to degrade. It should be noted that Figure 2 The graph is illustrative only, and the dark current noise accumulation over time generally increases with the square root of time. (Alternatively, consider the y-axis to be plotted on a matching nonlinear polynomial scale.) Likewise, at zero integration time (a condition in which the accumulated dark current noise is zero), the axes do not cross each other.

[0095] Returning to system 100, it should be noted that controller 112 can control activation of receiver 110 for a shorter integration time (e.g., an integration time during which the accumulated dark current noise does not exceed half the read noise or one-quarter the read noise). It should be noted that, unless specifically required, limiting the integration time to a very low level will limit the number of light-sensing signals that can be detected and degrade the SNR relative to thermal noise. It should be noted that the thermal noise level in multiple readout circuits adapted to read multiple noisy signals (requiring the collection of relatively high signal levels) can introduce non-negligible read noise, which can significantly degrade the SNR.

[0096] In some implementations, the controller 112 may apply a slightly longer integration time (eg, an integration time during which the accumulated dark current noise does not exceed twice the read noise or ×1.5 of the read noise).

[0097] Exemplary embodiments disclosed herein relate to systems and methods for high-SNR active SWIR imaging using multiple receivers including germanium-based PDs. A primary advantage of germanium receiver technology over indium gallium arsenide (InGaAs) technology is its compatibility with CMOS process flows, allowing the receivers to be manufactured as part of a CMOS production line. For example, by growing multiple Ge epitaxial layers on a silicon (Si) substrate, such as with Si photonics, multiple Germanium PDs can be integrated into a CMOS process flow. Consequently, Germanium PDs are more cost-effective than equivalent indium gallium arsenide (InGaAs) PDs.

[0098] To utilize germanium PDs, an exemplary system disclosed herein is adapted to overcome the relatively high dark current limitations of germanium diodes, typically in the range of about 50 uA / cm². The dark current problem can be overcome by using active imaging with a combination of short acquisition time and high-power laser pulses.

[0099] Compared to indium gallium arsenide (InGaAs) technology, the use of germanium PDs—particularly, but not limited to, those manufactured using a CMOS process flow—is a significantly less expensive solution for uncooled SWIR imaging. Unlike many prior art imaging systems, active imaging system 100 includes a pulsed illumination source with a short illumination duration (e.g., less than 1 μs, such as 1 to 1000 μs) and high peak power. Despite the drawbacks of such pulsed light sources (e.g., uneven illumination, more complex readout circuitry that may introduce higher levels of readout noise), and the drawbacks of shorter integration times (e.g., the inability to capture a wide range of distances in a single acquisition cycle), several approaches are discussed below to overcome these drawbacks and provide effective imaging systems.

[0100] Now refer to Figure 1B and Figure 1C , which schematically illustrate a number of other SWIR imaging systems numbered 100' and 100" according to some embodiments. Like system 100, system 100' includes an active illumination source 102A and receiver 110. In some embodiments, imaging systems 100, 100' and 100" also include a controller 112 and an image processor 114. In some embodiments, processing of the output of receiver 110 can be performed by image processor 114, and additionally or alternatively by an external image processor (not shown). Multiple imaging systems 100' and 100" can be many variations of imaging system 100. Any component or function discussed with respect to system 100 can be implemented in any of systems 100' and 100", and vice versa.

[0101] Controller 112 is a computing device. In some embodiments, many of the functions of controller 112 are provided within illumination source 102 and receiver 110, and controller 112 need not be a separate component. In some embodiments, control of imaging systems 100' and 100" is performed by a combination of controller 112, illumination source 102, and receiver 110. Additionally or alternatively, in some embodiments, control of imaging systems 100' and 100" may be performed by an external controller, such as a vehicle electronic control unit (ECU) 120 (which may be part of a vehicle in which the imaging system is installed).

[0102] The illumination source 102 is configured to emit a light pulse 106 in the infrared (IR) region of the electromagnetic spectrum. More specifically, the light pulse 106 is in the SWIR spectral band, including wavelengths in a range of approximately 1.3 μm to 3.0 μm.

[0103] In some embodiments, such as Figure 1B As shown in FIG, the illumination source (now labeled 102A) is an active Q-switched laser (or "active Q-type switch" laser) that includes a gain medium 122, a pump 124, a plurality of mirrors (not shown), and an active QS element 126A. In some embodiments, the QS element 126A is a modulator. After the gain medium 122 is electrically or optically pumped by the pump 124, a light pulse is released through the actively triggered QS element 126A.

[0104] In some embodiments, such as Figure 1C As shown in FIG, the illumination source 102P is a P-QS laser that includes a gain medium 122, a pump 124, a plurality of mirrors (not shown), and a SA 126P. After a "passive QS" light pulse is released, the SA 126P allows the laser cavity to store light energy (from the gain medium 122 pumped by the pump 124) until a saturation level is reached in the SA 126P. To detect the release of the passive QS pulse, a QS pulse photodetector 128 is coupled to the illumination source 102P. In some embodiments, the QS pulse photodetector 128 is a germanium PD. The signal from the QS pulse photodetector 128 is used to trigger the receiving process in the receiver 110 so that the receiver 110 will be activated after a time period suitable for the distance of the target 104 to be imaged. The time period is derived as follows with reference to Figure 3B 、 Figure 3C 、 Figure 4B and Figure 4C Further described.

[0105] In some embodiments, the laser pulse duration from illumination source 102 is in the range of 100 ps to 1 microsecond. In some embodiments, the laser pulse energy is in the range of 10 microjoules to 100 millijoules. In some embodiments, the laser pulse period is on the order of 100 microseconds. In some embodiments, the laser pulse period is in the range of 1 microsecond to 100 milliseconds.

[0106] The gain medium 122 is provided in a crystalline form or alternatively in a ceramic form. Non-limiting examples of materials that can be used for the gain medium 122 include: Nd:YAG, Nd:YVO4, Nd:YLF, Nd:Glass, Nd:GdVO4, Nd:GGG, Nd:KGW, Nd:KYW, Nd:YALO, Nd:YAP, Nd:LSB, Nd:S-FAP, Nd:Cr:GSGG, Nd:Cr:YSGG, Nd:YSAG, Nd:Y2O3, Nd:Sc2O3, Er:Glass, Er:YAG, and so on. In some embodiments, the doping levels of the gain medium can be varied based on the need for a specific gain. Non-limiting examples of SA 126P include: Co2+:MgAl2O4, Co2+:spinel, Co2+:zinc selenide (ZnSe) and other cobalt-doped crystals, V3+:YAG, doped glass, quantum dots, semiconductor SA mirrors (SESAM), Cr4+YAG SA, and the like. For additional ways in which the P-QS laser 102P can be implemented, see Figure 6 11, any of the variations discussed with respect to a laser 600 may also be applied mutatis mutandis to the illumination source 102P.

[0107] Regarding the illumination source 102, it is noted that pulsed lasers with sufficient power and short enough pulses are more difficult to obtain and more expensive than non-pulsed illumination, especially when eye-safe SWIR radiation based on solar absorption is desired.

[0108] Receiver 110 may include one or more germanium PDs 118 and receiver optics 116. In some embodiments, receiver 110 includes a 2D array of a plurality of germanium PDs 118. Receiver 110 is selected to be sensitive to infrared radiation including at least the wavelength emitted by illumination source 102, such that the receiver can form an imagery of the illuminated target 104 from reflected radiation 108.

[0109] The receiver optics 116 may include one or more optical elements, such as mirrors or lenses, arranged to collect, concentrate, and optionally filter the reflected electromagnetic radiation 108 and focus the electromagnetic radiation onto a focal plane of the receiver 110 .

[0110] The receiver 110 generates a plurality of electrical signals in response to electromagnetic radiation detected by one or more germanium PDs 118 representing an image of the illuminated scene. The plurality of signals detected by the receiver 110 may be transmitted to an internal image processor 114 or an external image processor (not shown) for processing into a SWIR image of the target 104. In some embodiments, the receiver 110 is activated multiple times to create "time slices," each covering a specific range of distances. In some embodiments, the image processor 114 combines the slices to create a single image with greater visual depth, such as proposed by Gruber, Tobias et al. "Gated2depth: Real-time dense LIDAR from gated images," arXiv preprint arXiv:1902.04997 (2019), incorporated herein by reference in its entirety.

[0111] In the automotive field, the images of objects 104 within the field of view (FOV) of the receiver 110 generated by the multiple imaging systems 100 ′ or 100 ″ can be processed to provide various driver assistance and safety features, such as forward collision warning (FCW), lane departure warning (LDW), traffic sign recognition (TSR), and detection of relevant entities such as pedestrians or oncoming vehicles. The generated images can also be displayed to the driver, for example, on a head-up display (HUD) projected on the vehicle windshield. Additionally or alternatively, the multiple imaging systems 100 ′ or 100 ″ can be interfaced to a vehicle ECU 120 to provide multiple images or videos to enable autonomous driving in low light levels or poor visibility conditions.

[0112] In many active imaging scenarios, a light source such as a laser is used in combination with an array of multiple light receivers. Since the germanium PD operates in the SWIR band, high power light pulses are feasible without exceeding eye safety regulations. For implementations in automotive scenarios, a typical pulse length is ~100 nanoseconds (ns), although, in some embodiments, longer pulse durations of up to about 1 microsecond can also be expected. Considering eye safety, a peak pulse power of ~300 kilowatts (kW) is allowed, but current laser diodes cannot actually reach this level. Therefore, in the present system, the high power pulses are generated by a QS laser. In some embodiments, the laser is a P-QS laser to further reduce costs. In some embodiments, the laser is an active QS.

[0113] As used herein, the term "target" means any imaged entity, object, area, or scene. Non-limiting examples of targets in automotive applications include vehicles, pedestrians, physical obstacles, or other objects.

[0114] According to some embodiments, an active imaging system includes: an illumination source for emitting a pulse of radiation toward a target, thereby causing radiation to be reflected from the target, wherein the illumination source comprises a QS laser; and a receiver comprising one or more germanium PDs for receiving the reflected radiation. In some embodiments, the illumination source operates in the SWIR spectral band.

[0115] In some embodiments, the QS laser is an active QS laser. In some embodiments, the QS laser is a P-QS laser. In some embodiments, the P-QS laser comprises a SA. In some embodiments, the SA is selected from the group consisting of Co2+:MgAl2O4, Co2+:spinel, Co2+:ZnSe and other cobalt-doped crystals, V3+:YAG, doped glass, quantum dots, semiconductor SA mirrors (SESAM), and Cr4+YAG SA.

[0116] In some embodiments, the system further comprises a QS pulse photodetector for detecting a radiation pulse emitted by the P-QS laser. In some embodiments, the receiver is configured to be activated for a time sufficient for the radiation pulse to travel to a target and return to the receiver. In some embodiments, the receiver is activated for an integration time during which the dark current power of the germanium PD does not exceed the kTC noise power of the germanium PD.

[0117] In some embodiments, the receiver generates a plurality of electrical signals in response to the reflected radiation received by the plurality of germanium PDs, wherein the plurality of electrical signals represent an image of the target illuminated by the radiation pulse. In some embodiments, the plurality of electrical signals are processed by one of an internal image processor or an external image processor into an image of the target. In some embodiments, the image of the target is processed to provide one or more of forward collision warning, lane departure warning, traffic sign recognition, and detection of pedestrians or oncoming vehicles.

[0118] According to various other embodiments, a method for performing active imaging includes the steps of: releasing a light pulse via an illumination source, the illumination source comprising an active QS laser; and activating a receiver, comprising one or more germanium PDs, for a limited time period sufficient for the light pulse to travel to a target and return to the QS laser to receive a reflected light pulse reflected from the target. In some embodiments, the illumination source operates in the short-wave infrared (SWIR) spectral band. In some embodiments, the limited time period is equal to an integration time, during which the dark current power of the germanium PDs does not exceed a kTC noise power of the germanium PDs.

[0119] In some embodiments, the receiver generates the plurality of electrical signals in response to the reflected light pulses received by the plurality of germanium PDs, wherein the plurality of electrical signals represent an image of the target illuminated by the light pulses. In some embodiments, the plurality of electrical signals are processed by one of an internal image processor or an external image processor into an image of the target. In some embodiments, the image of the target is processed to provide one or more of forward collision warning, lane departure warning, traffic sign recognition, and detection of pedestrians or oncoming vehicles.

[0120] According to various other embodiments, a method for performing active imaging includes the steps of: pumping a P-QS laser, the P-QS laser including an SA to cause release of a light pulse when the SA is saturated; detecting the release of the light pulse via a QS pulse photodetector; and activating a receiver for a limited period of time, based on the detected light pulse release, sufficient for the light pulse to travel to a target and return to the QS laser, the receiver including one or more germanium PDs to receive the reflected light pulse. In some embodiments, the QS laser operates in the short-wave infrared (SWIR) spectral band.

[0121] In some embodiments, the SA is selected from Co2+:MgAl2O4, Co2+:spinel, Co2+:ZnSe, other cobalt-doped crystals, V3+:YAG, doped glass, quantum dots, semiconductor SA mirrors (SESAM), and Cr4+YAG SA. In some embodiments, the limited time period is equal to an integration time, during which the dark current power of the Ge PD does not exceed the kTC noise power of the Ge PD.

[0122] In some embodiments, the receiver generates a plurality of electrical signals in response to the reflected light pulses received by the plurality of germanium PDs, wherein the plurality of electrical signals represent an image of the target illuminated by the light pulses. In some embodiments, the plurality of electrical signals are processed by one of an internal image processor or an external image processor into an image of the target. In some embodiments, the image of the target is processed to provide one or more of forward collision warning, lane departure warning, traffic sign recognition, and detection of pedestrians or oncoming vehicles.

[0123] Exemplary embodiments relate to a system and method for high SNR active SWIR imaging using multiple germanium-based PDs. In some embodiments, the imaging system is a gated imaging system. In some embodiments, the pulsed illumination source is an active or P-QS laser.

[0124] Now refer to Figure 3A 、 Figure 3B and Figure 3C , respectively showing a flow chart and a plurality of schematic diagrams of an operating method of an active SWIR imaging system according to some embodiments. Figure 3A The process 300 shown in FIG. Figure 1BSystem 100' is described. In step 302, pump 124 of illumination source 102A is activated to pump gain medium 122. In step 304, active QS element 126A releases a light pulse in the direction of a target 104 located at a distance D. In step 306, at time = T, the light pulse impacts target 104 and generates reflected radiation that returns toward system 100' and receiver 110. In step 308, after waiting for a time = T2, receiver 110 is activated to receive the reflected radiation. The return propagation delay T2 is composed of the flight time of the pulse from illumination source 102A to target 104 plus the flight time of the light signal reflected from target 104. Therefore, for a target 104 located at a distance "D" from illumination source 102A and receiver 110, T2 is known. The activation period Δt of the receiver 110 is determined based on the desired depth of field (DoV). The DoV is given by 2DoV=c*Δt, where c is the speed of light. A typical Δt of 100 ns provides a depth of field of 15 meters. In step 310, the reflected radiation is received by the receiver 110 for a period of time of Δt. The received data from the receiver 110 is processed by the image processor 114 (or an external image processor) to generate a received image. Process 300 can be repeated N times in each frame, where a frame is defined as the data set transmitted from the receiver 110 to the image processor 114 (or an external image processor). In some embodiments, N is between 1 and 10,000.

[0125] Now refer to Figure 4A 、 Figure 4B and Figure 4C A flowchart and schematic diagrams respectively illustrate an exemplary method of operating an active SWIR imaging system according to some embodiments. A process 400 shown in FIG4 is based on the reference Figure 1CThe system 100" is described. In step 402, the pump 124 of the illumination source 102P is activated to pump the gain medium 122 and saturate the SA 126P. In step 404, after reaching a saturation level, the SA 126P releases a light pulse in the direction of a target 430, which is located at a distance D. In step 406, the QS pulse photodetector 128 detects the released light pulse. In step 408, at time = T, the light pulse impacts the target 430 and generates reflected radiation that returns toward the system 100" and the receiver 110. In step 410, after waiting for a time = T2 after a released light pulse is detected by the QS pulse photodetector 128, the receiver 110 is activated to receive the reflected radiation. The return propagation delay T2 includes the flight time of the pulse from the illumination source 102P to the target 430 plus the flight time of the light signal reflected from the target 430. Thus, for a target 430 at a distance "D" from illumination source 102P and receiver 110, T2 is known. The activation period of Δt is determined based on the desired depth of field (DoV). In step 412, receiver 110 receives the reflected radiation for a period of Δt. The received data from receiver 110 is processed by image processor 114 (or by an external image processor) to generate a received image. Process 400 may be repeated N times per frame. In some embodiments, N is between 1 and 10,000.

[0126] With reference to all of the imaging systems 100, 100', and 100", it is noted that any of those imaging systems can include readout circuitry for reading out an accumulation of charge collected by each germanium PD after the integration time to provide the detection signal for the corresponding PD. Thus, unlike LIDARs or other depth sensors, the readout process can be performed after oscillation of the integration time and thus after the signals have been irreversibly summed from a wide range of distances.

[0127] With reference to all of the imaging systems 100, 100' and 100", optionally, the receiver 110 outputs a set of detection signals representing charge accumulated by each of the plurality of germanium PDs during the integration time, wherein the set of detection signals represents an image of the target illuminated by the at least one SWIR radiation pulse.

[0128] With reference to all of the imaging systems 100, 100' and 100", the imaging systems may optionally include at least one diffractive optical element (DOE) operable to improve the illumination uniformity of the light of the pulsed illumination source before emitting the light toward the target. As described above, a high peak power pulsed light source 102 may emit a less than uniform illumination distribution over different portions of the FOV. The DOE (not illustrated) may improve the uniformity of the illumination to generate multiple high quality images of the FOV. It is noted that equivalent illumination uniformity is not typically required in many LiDAR systems and other depth sensors, and therefore is not desirable for reasons of cost, system complexity, system size, or other reasons. For example, in LIDAR systems, it does not matter if certain areas in the FOV receive more illumination density than other parts of the FOV, as long as the entire FOV receives sufficient illumination (above a threshold that allows detection of targets at a minimum required distance). The DOE of the system 100, if implemented, can be used, for example, to reduce speckle effects. It is noted that the imaging systems 100, 100' and 100" can also include other types of optics for directing light from the light source 102 to the FOV, such as lenses, mirrors, prisms, waveguides, etc.

[0129] With reference to all of the imaging systems 100, 100', and 100", the controller 112 may optionally be operated to activate the receiver 110 to sequentially acquire a series of gated images, each gated image representing a detection signal of a different germanium PD within a different distance range, and an image processor may be operated to combine the series of images into a single two-dimensional image. For example, a first image may acquire light from the imaging sensor between 0 and 50 meters (m), a second image may acquire light from the imaging sensor between 50 and 100 meters, and a third image may acquire light from the imaging sensor between 0 and 50 meters (m). The image processor 114 can combine multiple 2D images into a single 2D image. Each distance range is captured with an accumulated dark current noise that is still less than the read noise introduced by the readout circuitry, at the expense of using more light pulses and more computation. The color value (e.g., grayscale value) of each pixel in the final image can be determined based on a function of the individual pixels in the multiple gated images (e.g., a maximum or weighted average of all values).

[0130] All imaging systems 100, 100' and 100" may be an uncooled germanium-based SWIR imaging system operable to detect a 1 m x 1 m target at a distance exceeding 50 m with a 20% SWIR reflectivity (in the relevant spectral range).

[0131] With reference to all imaging systems 100, 100' and 100", the pulsed illumination source 102 can be a QS laser operable to emit eye-safe laser pulses having a pulse energy between 10 millijoules and 100 millijoules. Although not required, the illumination wavelength can be selected to match a solar absorption band (for example, the illumination wavelength can be between 1.3 micrometers (μm) and 1.4 μm).

[0132] With reference to all of the imaging systems 100, 100', and 100", the output signal of each germanium PD used for image generation can represent a single scalar for each PD. With reference to all of the imaging systems 100, 100', and 100", each PD can output a cumulative signal that represents a wide range of multiple distances. For example, some, most, or all of the germanium PDs of the receiver 110 can output multiple detection signals that represent each of the lights reflected from 20m, 40m, and 60m to the corresponding PD.

[0133] Another distinguishing feature of the imaging systems 100, 100' and 100" compared to many known art systems is that the pulsed illumination is not used to freeze rapid motion of objects in the field (unlike, for example, photographic flash illumination) and is also used for static scenes. Another distinguishing feature of the imaging systems 100, 100' and 100" compared to many known art systems is that the gating of the images is not primarily used to avoid internal noise in the system as opposed to external noise, which is a problem with some known technologies (such as sunlight).

[0134] It should be noted that any of the components, features, operating modes, system architectures, and interrelationships discussed above with respect to systems 100, 100', and 100" may, where necessary, be implemented in any of the EO systems discussed below, such as systems 700, 1300, 1300', 1600, 1600', 1700, 1800, 1900, 2300, and 3600.

[0135] Figure 5FIG. 5 is a flow chart illustrating a method 500 for generating SWIR images of objects in a FOV of an EO system according to examples of the presently disclosed subject matter. Referring to the examples described with respect to the previous figures, the method 500 may be performed by any of the imaging systems 100, 100′, and 100″. It is noted that the method 500 may also be implemented by any of the active imaging systems described below, such as the systems 700, 1300, 1300′, 1600, 1600′, 1700, 1800, 1900, 2300, and 3600.

[0136] Method 500 begins with a step (or "stage") 510 of emitting at least one illumination pulse toward the FOV, thereby causing SWIR radiation to reflect from at least one target. Hereinafter, "step" and "stage" may be used interchangeably. Optionally, the one or more pulses may be high-peak power pulses. For example, multiple illumination pulses may be used to achieve an overall higher level of illumination than a single pulse. Referring to the various examples in the various figures, step 510 may optionally be performed by controller 112.

[0137] A step 520 includes triggering the initiation of continuous signal acquisition by an imaging receiver comprising a plurality of germanium PDs (in the sense discussed above with respect to receiver 110), which is operable to detect the reflected SWIR radiation. The continuous signal acquisition of step 520 means that the charge is collected continuously and irreversibly (i.e., it is not possible to know what level of charge is collected at any intermediate time), and not in small increments. The triggering of step 520 can be performed before step 510 (e.g., if the detection array requires a ramp-up time), simultaneously with step 510, or after step 510 has concluded (e.g., upon commencing detection at a non-zero distance from the system). With reference to the example of the accompanying figures, step 520 can optionally be performed by controller 112.

[0138] Step 530 begins after the triggering step 520 and includes collecting, for each of the plurality of Ge PDs, at least a charge induced on the corresponding Ge PD by the SWIR reflected radiation impinging thereon as a result of the triggering, greater than 50 μA / cm 2 With reference to the example of the accompanying drawings, step 530 may optionally be performed by the receiver 110.

[0139] Step 540 includes triggering a cessation of charge collection when the amount of charge collected due to dark current noise is still lower than the amount of charge collected due to readout noise that is irrelevant to the accumulated time. The integration time is the duration from step 530 to the cessation of step 540. Referring to the example in the accompanying drawings, step 540 may optionally be performed by controller 112.

[0140] Step 560 is performed after step 540 and includes generating an image of the FOV based on the charge levels collected by each of the plurality of germanium PDs. As previously described with respect to imaging systems 100, 100', and 100", the image generated in step 560 is a 2D image without depth information. Referring to the example figures, step 560 may optionally be performed by imaging processor 114.

[0141] Optionally, stopping collection as a result of step 540 can be followed by an optional step 550 of reading, by a readout circuit, a signal related to the amount of charge collected by each of the plurality of Ge PDs, amplifying the readout signal, and providing the amplified signal (optionally after further processing) to an image processor, which performs the generation of the image as in step 560. Referring to the example of the accompanying drawings, step 550 can optionally be performed by the readout circuit (not illustrated above, but can be equivalent to any readout circuit discussed below, such as readout circuits 1610, 2318, and 3630). It should be noted that step 550 is optional, as other suitable methods of reading the plurality of detection results from the plurality of Ge PSs can be implemented.

[0142] Optionally, the signal output by each of the plurality of germanium PDs is a scalar representing the amount of light reflected from 20 meters, the amount of light reflected from 40 meters, and the amount of light reflected from 60 meters.

[0143] Optionally, the generating of step 560 may include generating the image based on a scalar value read for each of the plurality of germanium PDs. Optionally, the emitting of step 510 may include increasing illumination uniformity of the pulsed laser illumination (via one or more lasers) by passing the pulsed laser illumination through at least one diffractive optical element (DOE) and emitting the attenuated light into the FOV. Optionally, the dark current is greater than 50 picoamperes per germanium PD. Optionally, the plurality of germanium PDs are silicon-germanium PDs (Si-Ge PDs), each comprising silicon and germanium. Optionally, the emitting is performed using at least one active QS laser. Optionally, the emitting is performed using at least one P-QS laser. Optionally, the collecting is performed while the receiver is operating at a temperature greater than 30°C, and the image of the FOV is processed to detect a plurality of vehicles and a plurality of pedestrians within a plurality of ranges between 50 meters and 150 meters. Optionally, the emitting comprises emitting a plurality of illumination pulses having a pulse energy between 10 millijoules and 100 millijoules into an unprotected eye of a person at a distance of less than 1 meter without damaging the eye.

[0144] As previously described with respect to the various active imaging systems 100, 100' and 100", several gated images may be combined into a single image. Optionally, the method 500 may include repeating multiple times of emitting, triggering, collecting and stopping. The method 500 may include: generating a sequence of acquisitions (e.g., acquisitions) in which the acquisitions are triggered at different times from the light emission in each sequence. In each sequence, the method 500 may include: reading a detection value from the receiver for each of the plurality of germanium PDs corresponding to different distance ranges greater than 2 meters (e.g., 2.1 meters, 5 meters, 10 meters, 25 meters, 50 meters, 100 meters). In such a case, the generation of the image in step 560 includes generating a single two-dimensional image based on the plurality of detection values read from the different germanium PDs in different sequences. It should be noted that, since only a few images are captured, the plurality of gated images are not sparse (i.e., detection values for many pixels are present in all or most gated images). It should also be noted that the plurality of gated images may have overlapping distance ranges. For example, a first image may represent a distance range of 0 to 60 meters, a second image may represent a distance range of 50 to 100 meters, and a third image may represent a distance range of 90 to 120 meters.

[0145] Figures 6 to 11C Demonstrates SWIR electro-optical (EO) systems and P-QS lasers that can be used in such systems, as well as methods for the operation and fabrication of such lasers.

[0146] Figure 10 is a schematic functional block diagram illustrating one example of a SWIR optical system 700 according to many examples of the disclosed subject matter. The system 700 includes at least a P-QS laser 600, but may also be as Figure 10 Additional components are shown as included, such as a sensor 702 operable to sense reflected light from the FOV of the system 700 , particularly reflected illumination from the laser 600 that is reflected from external objects 910 .

[0147] Referring to other examples, the sensor 702 may be implemented as an imaging receiver, a PDA, or a number of photodetection devices discussed in this disclosure, such as the number of components 110 , 1300 , 1300 ′, 1600 , 1600 ′, 1700 , 1800 , 1900 , 2302 , and 3610 .

[0148] A processor 710 is operable to process the sensing results of the sensor 702. The output of the processing may be an image of the FOV, a depth model of the FOV, a spectral analysis of one or more portions of the FOV, information about identified objects in the FOV, light statistics on the FOV, or any other type of output. With reference to other examples, the processor 710 may be implemented as any of the processors discussed in this disclosure, such as the processors 114, 1908, 2304, and 3620.

[0149] A controller 712 is operable to control the activities of the laser 600 and / or the processor 710. For example, the controller 712 may include controlling the timing, synchronization, and other operating parameters of the processor 710 and / or the laser 600. With reference to various other examples, the controller 712 may be implemented as any of the other controllers discussed in this disclosure, such as the controllers 112, 1338, 2314, and 3640.

[0150] Optionally, system 700 may include a SWIR PDA 706 that is sensitive to the wavelength of the laser light. Thus, the SWIR optical system may function as an active SWIR camera, a SWIR time-of-flight (ToF) sensor, a SWIR light detection and ranging (LIDAR) sensor, or the like. The ToF sensor may be sensitive to the wavelength of the laser light. Alternatively, the PDA may be a CMOS-based PDA that is sensitive to a variety of SWIR frequencies emitted by laser 600, such as a CMOS-based PDA designed and manufactured by TriEye LTD of Tel Aviv, Israel.

[0151] Optionally, system 700 may include a processor 710 for processing detection data from the SWIR PDA (or any other photosensor of system 700). For example, the processor may process the detection information to provide a SWIR image of a field of view (FOV) of system 700, detect objects within the FOV, and so forth. Optionally, the SWIR optical system may include a time-of-flight (ToF) SWIR sensor sensitive to the wavelength of the laser light and a controller operable to synchronize operation of the ToF SWIR sensor and the P-QS SWIR laser to detect a distance to at least one object within the field of view of the SWIR optical system. Optionally, system 700 may include a controller 712 operable to control one or more aspects of the operation of laser 600 or other components of the system, such as a photodetector array (e.g., a focal plane array (FPA)). For example, several parameters of the laser can be controlled by the controller, including timing, duration, intensity, focusing, and the like. Although not required, the controller can control the operation of the laser based on various detection results of the PDA (directly or based on processing by the processor). Optionally, the controller can be operable to control the laser pump or other type of light source to affect various activation parameters of the laser. Optionally, the controller can be operable to dynamically change the pulse repetition rate. Optionally, the controller can be operable to control dynamic modification of the light shaping optics, for example, to improve a signal-to-noise ratio (SNR) in specific areas of the field of view. Optionally, the controller can be operable to control the illumination module to dynamically change the pulse energy and / or duration (e.g., in the same manner as many other P-QS lasers are possible, such as by changing the focus of the pump laser).

[0152] Furthermore and optionally, the system 700 may include temperature control (e.g., passive temperature control, active temperature control) for generally controlling the temperature of the laser or one or more components thereof (e.g., the pump diode). Such temperature control may include, for example, a thermoelectric cooler (TEC), a fan, a heat sink, a resistive heater under the pump diode, and so on.

[0153] Furthermore, and optionally, the system 700 may include another laser for bleaching at least one of the GM 602 and the SA 604. Alternatively, the system 700 may include an internal photodetector (e.g., one or more PDs, such as the PDA 706) operable to measure the timing of a pulse generated by the laser 600 (e.g., the PDs described above). In such a case, the controller 712 may be operable to send a trigger signal to the PDA 706 (or other type of camera or sensor 702) based on the timing information obtained from the internal photodetector 706, which detects reflections of the laser light from objects in the field of view of the system 700.

[0154] The main industry that requires large quantities of lasers in the above-mentioned spectral range (1.3 to 1.5 μm) is the electronics industry for optical data storage, which has driven down the cost of diode lasers to a few dollars per device and per watt or even less. However, these lasers are not suitable for other industries, such as the automotive industry, which require lasers with very high peak power and beam brightness and are used in harsh environmental conditions.

[0155] It should be noted that there is no scientific consensus on the wavelength range that is considered part of the SWIR spectrum. However, for the purposes of this disclosure, the SWIR spectrum includes electromagnetic radiation having wavelengths greater than those of the visible spectrum and including at least the spectral range between 1300 and 1500 nm.

[0156] Although not limited to such use, one or more P-QS lasers 600 may be used as the illumination source 102 of any of the imaging systems 100, 100', and 100". The laser 600 may be used in any other EO system in the SWIR range that requires pulsed illumination, such as lidars, spectrometers, communication systems, and the like. It is noted that the proposed lasers 600 and methods for manufacturing such lasers allow for high-volume manufacturing of lasers operating in the SWIR spectral range at relatively low production costs.

[0157] The P-QS laser 600 includes at least a crystalline gain medium 602 (hereinafter referred to as "GM"), a crystal SA 604, and an optical cavity 606. The crystalline material is confined in the optical cavity 606 to allow light to propagate in the gain medium 602 to enhance the tendency to generate a laser beam 612 (e.g., in the case of a laser beam). Figure 8). The optical cavity is also known by the terms "optical resonator" and "resonating cavity" and includes a high reflectivity mirror 608 (also known as a "high reflector") and an output coupler 610. Discussed below are unique and novel combinations of several different types of crystalline materials and the use of various fabrication techniques to fabricate the laser, thereby allowing for mass production of lasers in the SWIR spectral range at reasonable prices. For the sake of brevity of this disclosure, general details known in the art regarding P-QS lasers are not provided here, but such details are readily available from a variety of sources. As is known in the art, the saturable absorber of the laser serves as the Q-switch of the laser. The term "crystalline material" broadly includes any material in single crystal or polycrystalline form.

[0158] The dimensions of the coupled crystal gain medium and crystal SA can depend on the purpose of designing a particular P-QS laser 600. In a non-limiting example, a combined length of the SA and the GM is between 5 and 15 mm. In a non-limiting example, the combined length of the SA and the GM is between 2 and 40 mm. In a non-limiting example, a diameter of the combined SA and GM (e.g., if a cylinder, or confined within an imaginary such cylinder) is between 2 and 5 mm. In a non-limiting example, a diameter of the combined SA and GM is between 0.5 and 10 mm.

[0159] The P-QS laser 600 comprises a gain medium crystalline material (GMC) that is rigidly coupled to a SA crystalline material (SAC). The rigid coupling can be achieved in any manner known in the art, such as using an adhesive, diffusion bonding, composite crystal bonding, growing one on top of the other, and the like. However, as described below, rigidly coupled crystalline materials in the form of a ceramic can be achieved using simple and inexpensive methods. It is to be noted that the GMC and the SAC materials can be rigidly coupled directly to each other, but can alternatively be rigidly coupled to each other via an intermediate object (such as another crystal). In some embodiments, both the gain medium and the SA can be implemented on a single piece of crystalline material by doping different dopants (such as those discussed below with respect to the SAC material and the GMC) in different portions of the single piece of crystalline material, or by co-doping the single piece of crystalline material with two dopants (such as co-doped with N 3The gain medium can be grown on a single crystal saturable absorbing substrate (e.g., using liquid phase epitaxy (LPE)). It should be noted that the separate GMC and SA crystalline materials discussed extensively in the following disclosures, as well as monolithic ceramic crystalline materials doped with both dopants, can also be used in any of the following implementations.

[0160] Figure 7A 、 Figure 7B and Figure 7C 1 are schematic functional block diagrams illustrating examples of a P-QS laser 600 according to the presently disclosed subject matter. Figure 7A In FIG, the two dopants are implemented on two portions of the common crystalline material 614 (acting as both GM and SA), while in Figure 7B In FIG. 6 , the two dopants are interchangeably implemented on a common volume of common crystalline material 614 (in the illustrated case, the entirety of the common crystal). Alternatively, the GM and the SA may be implemented on a single piece of crystalline material doped with neodymium and at least one other material. Alternatively (e.g., Figure 7C As shown in FIG, any one or both of the output coupler 610 and the high reflectivity mirror 608 can be directly glued to one of the multiple crystalline materials (such as the GM or the SA, or a crystal combining the two).

[0161] At least one of the SAC and GMC is a ceramic crystalline material, which is a related crystalline material (e.g., doped yttrium aluminum garnet, YAG, doped with vanadium) in a ceramic form (e.g., a polycrystalline form). Crystalline materials in one (and particularly two) ceramic forms allow for higher-volume and lower-cost production. For example, instead of growing a single crystal of material in a slow and finite process, polycrystalline materials can be produced by powder sintering (i.e., compacting and possibly heating a powder to form a solid mass), low-temperature sintering, vacuum sintering, and the like. One of the crystalline materials (SAC or GMC) can be sintered on top of the other, eliminating complex and expensive processes such as polishing, diffusion bonding, or surface-activated bonding. Optionally, at least one of the GMC and SAC is polycrystalline. Optionally, both the GMC and SAC are polycrystalline.

[0162] The various combinations of crystalline materials mentioned for the GMC and the SAC can be made, such combinations may include:

[0163] a. The GMC is a ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and the SAC is (a) a ceramic trivalent vanadium-doped yttrium aluminum garnet (V3+:YAG) or (b) a ceramic cobalt-doped crystalline material. Alternatively, the ceramic cobalt-doped crystalline material may be a divalent ceramic cobalt-doped crystalline material. In those alternatives, both the Nd:YAG and the SAC selected from the above group are in the form of ceramics. A cobalt-doped crystalline material is a crystalline material doped with cobalt. Examples include cobalt-doped spinel (Co:Co or Co: 2+ :MgAl2O4), cobalt-doped zinc selenide (Co 2+ :ZnSe), cobalt-doped YAG(Co 2+ :YAG). Although not required, in this option, the high reflectivity mirror and the SA can optionally be rigidly connected to the gain medium and the SA so that the P-QS laser is a monolithic microchip P-QS laser (e.g., Figure 8 and Figure 10 shown).

[0164] b. The GMC is a ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and the SAC is a non-ceramic SAC selected from the group consisting of: (a) vanadium-doped yttrium aluminum garnet (V3+:YAG) and (b) a cobalt-doped crystalline material. Alternatively, the cobalt-doped crystalline material can be a cobalt-doped crystalline material. In such a case, the high-reflectivity mirror 608 and the output coupler 610 are rigidly connected to the gain medium and the SA, making the P-QS laser 600 a monolithic microchip P-QS laser.

[0165] c. The GMC is a ceramic neodymium-doped rare earth element crystalline material, and the SAC is a ceramic crystalline material selected from the group consisting of: (a) vanadium-doped yttrium aluminum garnet (V3+:YAG) and (b) cobalt-doped crystalline materials. Optionally, the cobalt-doped crystalline material can be a divalent cobalt-doped crystalline material. Although not required, in this option, the high-reflectivity mirror 608 and the output coupler 610 can optionally be rigidly connected to the gain medium and the SA, such that the P-QS laser 600 is a monolithic microchip P-QS laser.

[0166] It should be noted that in any of the implementations, a doped crystalline material can be doped with more than one dopant. For example, the SAC can be doped with the primary dopant disclosed above and at least one other dopant material (e.g., at a significantly lower concentration). A neodymium-doped rare earth element crystalline material is a crystalline material whose unit cell contains a rare earth element (one of a clearly defined group of 15 chemical elements, including the 15 lanthanides and scandium and yttrium) and which is doped with neodymium (e.g., triply ionized neodymium) replacing the rare earth element in a portion of the unit cell. Several non-limiting examples of neodymium-doped rare earth element crystalline materials that can be used in the present disclosure are:

[0167] a. Nd:YAG (as described above), neodymium-doped potassium yttrium tungstate (Nd:KYW), neodymium-doped lithium yttrium fluoride (Nd:YLF), neodymium-doped yttrium orthovanadate (YVO4), in all of which the rare earth element is neodymium, Nd;

[0168] b. Neodymium-doped orthovanadate (Nd:GdVO4), neodymium-doped gallium garnet (Nd:GGG), neodymium-doped potassium gadolinium tungstate (Nd:KGW), all of which contain gadolinium as the rare earth element;

[0169] c. Neodymium-doped lanthanum scandium borate (Nd:LSB), wherein the rare earth element is scandium;

[0170] d. Other neodymium-doped rare earth element crystalline materials may be used, wherein the rare earth element may be yttrium, gadolinium, scandium or any other rare earth element.

[0171] The following discussion applies to any optional combination of GMCs and SACs.

[0172] Optionally, the GMC is directly rigidly connected to the SAC. Alternatively, the GMC and SAC may be connected indirectly (e.g., each of the SAC and GMC is connected via a group of one or more intermediate crystalline materials and / or via one or more other solid materials transparent to the relevant wavelength). Optionally, one or both of the SAC and GMC are transparent to the relevant wavelength.

[0173] Alternatively, the SAC may be a cobalt-doped spinel (Co Co 2+ :MgAl2O4). Alternatively, the SAC may be cobalt-doped YAG (Co:YAG). Optionally, this may allow cobalt and neodymium Nd to be co-doped on the same YAG. Alternatively, the SAC may be cobalt-doped zinc selenide (Co: 2+ :ZnSe). Optionally, the GMC may be a ceramic cobalt-doped crystalline material.

[0174] Optionally, an initial transmittance (T0) of the SA is between 75% and 90%. Optionally, the initial transmittance of the SA is between 78% and 82%.

[0175] The wavelengths emitted by the laser depend on the materials used in its construction, and in particular on the materials and dopants of the GMC and the SAC. Some examples of output wavelengths include wavelengths in the range of 1,300 nm and 1,500 nm. Some more specific examples include 1.32 μm or about 1.32 μm (e.g., 1.32 μm ± 3 nm), 1.34 μm or about 1.34 μm (e.g., 1.34 μm ± 3 nm), 1.44 μm or about 1.44 μm (e.g., 1.44 μm ± 3 nm). A corresponding imager sensitive to one or more of these optical frequency ranges can be included in the SWIR optical system 700 (e.g., Figure 10 shown).

[0176] Figure 8 and Figure 9 Schematic functional diagrams illustrating a SWIR optical system 700 according to various examples of the presently disclosed subject matter are shown. As demonstrated in these figures, the laser 600, in addition to those components discussed above, may also include additional components such as, but not limited to: a. A light source such as a flash lamp 616 or a laser diode 618, which serves as a pump for the laser. Referring to the previous examples, the light source may serve as the pump 124. b. Focusing optics 620 (e.g., a lens) for focusing light from the light source (e.g., 618) onto the optical axis of the laser 600.

[0177] c. A diffuser or other optical device 622 for manipulating the laser beam 612 after it leaves the optical cavity 606.

[0178] Optionally, the SWIR optical system 700 may include an optical device 708 to spread the laser light over a wider FOV to improve eye safety issues within the FOV. Optionally, the SWIR optical system 700 may include an optical device 704 to collect reflected laser light from the FOV and direct it to the sensor 702, for example, to a photodetector array (PDA) 706, see Figure 10 Optionally, the P-QS laser 600 is a diode pumped solid-state laser (DPSSL).

[0179] Optionally, the P-QS laser 600 includes at least one diode pump light source and optics 620 for focusing the light from the diode pump light source into the optical resonator (optical cavity). Optionally, the light source is located on the optical axis (as a one-end pump). Optionally, the light source can be rigidly connected to a high-reflectivity mirror 608 or SA 604, such that the light source is part of a monolithic microchip P-QS laser. Optionally, the light source of the laser can include one or more vertical-cavity surface-emitting laser (VCSEL) arrays. Optionally, the P-QS laser 600 includes at least one VCSEL array and optics for focusing the light from the VCSEL array into the optical resonator. The wavelength emitted by the light source (e.g., the pump laser) may depend on the crystalline materials and / or dopants used in the laser. Some exemplary pump wavelengths that can be emitted by the pump include 808 nm or approximately 808 nm, 869 nm or approximately 869 nm, and approximately 900 nm.

[0180] The power of the laser may depend on its intended use. For example, the laser output power may be between 1 W and 5 W. For example, the laser output power may be between 5 W and 15 W. For example, the laser output power may be between 15 W and 50 W. For example, the laser output power may be between 50 W and 200 W. For example, the laser output power may be greater than 200 W.

[0181] The QS laser 600 is a pulsed laser and can have different frequencies (repetition rates), different pulse energies, and different pulse durations, depending on the application for which it is designed. For example, a repetition rate of the laser can be between 10 Hz and 50 Hz. For example, a repetition rate of the laser can be between 50 Hz and 150 Hz. For example, a pulse energy of the laser can be between 0.1 mJ and 1 mJ. For example, a pulse energy of the laser can be between 1 mJ and 2 mJ. For example, a pulse energy of the laser can be between 2 mJ and 5 mJ. For example, a pulse energy of the laser can be greater than 5 mJ. For example, a pulse duration of the laser can be between 10 ns and 100 ns. For example, a pulse duration of the laser can be between 0.1 μs and 100 μs. For example, a pulse duration of the laser can be between 100 μs and 1 ms. The size of the laser can also vary, for example, depending on the size of its components. For example: the size of the laser may be X1 by X2 by X3, where each dimension (X1, X2 and X3) is between 10 mm and 100 mm, between 20 and 200 mm, etc. The output coupling mirror may be flat, curved or slightly curved.

[0182] Optionally, in addition to the gain medium and the SA, the laser 600 may further include undoped YAG to prevent heat accumulation in an absorption region of the gain medium. The undoped YAG may be shaped into a cylinder (e.g., a concentric cylinder) surrounding the gain medium and the SA.

[0183] Figure 11A 1 is a flow chart illustrating an example of a method 1100 according to the presently disclosed subject matter. Method 1100 is a method for manufacturing components for a P-QS laser, such as, but not limited to, the P-QS laser 600 described above. With reference to the examples described with respect to the previous figures, the P-QS laser may be laser 600. It should be noted that any variations discussed with respect to laser 600 or with respect to a component thereof may also be implemented with respect to components of the P-QS laser manufactured in method 1100 or with respect to a corresponding component thereof, and vice versa.

[0184] Method 1100 begins with step 1102 of inserting at least one first powder into a first mold, which is then processed in method 1100 to produce a first crystalline material. The first crystalline material serves as the GM or the SA of the P-QS laser. In some implementations, the gain medium of the laser is first fabricated (e.g., by sintering), and then the SA is fabricated on top of the previously fabricated GM (e.g., by sintering). In other implementations, the SA of the laser is first fabricated, and then the GM is fabricated on top of the previously fabricated SA. In other implementations, the SA and the GM are fabricated independently of each other and coupled to form a single rigid body. The coupling can be done as part of heating, sintering, or later.

[0185] Step 1104 of method 1100 includes inserting at least one second powder into a second mold, the at least one second powder being different from the at least one first powder. The at least one second powder is later processed in method 1100 to produce a second crystalline material. The second crystalline material is used as the GM or the SA of the P-QS laser (such that one of the SA and the GM is made of the first crystalline material and the other is made of the second crystalline material).

[0186] The second mold may be different from the first mold. Alternatively, the second mold may be the same as the first mold. In such a case, the at least one second powder may be inserted, for example, on top of the at least one first powder (or on top of the first green compact if already made), next to it, around it, and so on. The insertion of the at least one second powder into the same mold as the at least one first powder (if implemented) may be performed before the at least one first powder is processed into a first green compact, before the at least one first powder is processed into the second first green compact, or at some time during the process of processing the at least one first powder into the first green compact.

[0187] The first powder and / or the second powder may include crushed YAG (or any other of the aforementioned materials, such as spinel, MgAl2O4, ZnSe) and a doping material (such as N 3+ 、V 3+ , Co). The first powder and / or the second powder may include: a material for making YAG (or any other material mentioned above, such as spinel, MgAl2O4, ZnSe) and a doping material (such as N 3+ 、V 3+ 、Co).

[0188] Step 1106 is performed after step 1102 and includes compacting the at least one first powder in the first mold to produce a first green compact. Step 1104 is performed after step 1108 and includes compacting the at least one second powder in the second mold to produce a second green compact. If the at least one first powder and the at least one second powder are placed into the same mold in steps 1102 and 1104, compacting the powders in steps 1106 and 1108 can be performed simultaneously (e.g., pressing the at least one second powder, which in turn compresses the at least one first powder against the mold), but this is not required. For example, step 1104 (and therefore step 1108) can optionally be performed after the compaction in step 1106.

[0189] Step 1110 includes heating the first green body to yield a first crystalline material. Step 1112 includes heating the second green body to yield a second crystalline material. In various embodiments, the heating of the first crystal can be performed before, simultaneously with, partially simultaneously with, or after each of steps 1106 and 1110.

[0190] Optionally, heating the first green body at step 1110 precedes compacting the at least one second powder in step 1108 (and possibly in step 1104) (and possibly also prior to inserting). The first green body and the second green body can be heated separately (e.g., at different times, at different temperatures, for different durations). The first green body and the second green body can be heated together (e.g., in the same oven), or heated in conjunction with each other or not. The first green body and the second green body can be subjected to different heating regimes, which can share portions of the heating regime while being heated separately in other portions of the heating regime. For example, one or both of the first green body and the second green body can be heated separately from the other green body, and then the two green bodies can be heated together (e.g., after coupling, but not necessarily). Optionally, heating the first green body and heating the second green body includes heating the first green body and the second green body simultaneously in a single oven. It is noted that, optionally, the coupling of step 1114 is a result of heating the two green compacts simultaneously in a single oven.It is noted that, optionally, the coupling of step 1114 is accomplished by co-sintering the two green compacts after physically connecting them to each other.

[0191] Step 1114 comprises coupling the second crystalline material to the first crystalline material. The coupling can be performed using any coupling method known in the art, several non-limiting examples of which are discussed above with respect to P-QS laser 600. It should be noted that the coupling can have several sub-steps, some of which can be intertwined in different ways with different steps in steps 1106, 1108, 1110, and 1112 in different embodiments. The coupling results in a single rigid crystalline body comprising the GM and the SA.

[0192] It should be noted that method 1100 may include a number of additional steps used in the fabrication of many crystals, particularly in the fabrication of ceramic or non-ceramic polycrystalline compounds of polycrystalline materials bonded to one another. A few non-limiting examples include powder preparation, binder burn-out, densification, annealing, polishing (if necessary, as described below), and the like.

[0193] The GM of the P-QS laser in method 1100 (which may be the first crystalline material or the second crystalline material, as described above) is a neodymium-doped crystalline material. The SA of the P-QS laser in method 1100 (which may be the first crystalline material or the second crystalline material, as described above) is selected from a group of crystalline materials consisting of: (a) a neodymium-doped crystalline material, and (b) a doped crystalline material selected from a group of doped crystalline materials consisting of trivalent vanadium-doped yttrium aluminum garnet (V3+:YAG) and a cobalt-doped crystalline material. At least one of the GM and the SA is a ceramic crystalline material. Optionally, both the GM and the SA are ceramic crystalline materials. Optionally, at least one of the GM and the SA is a polycrystalline material. Optionally, both the GM and the SA are polycrystalline materials.

[0194] Although additional steps in the manufacturing process may be performed between different stages of method 1100, in at least some implementations, polishing of the first material prior to bonding of the second material during sintering is not required.

[0195] With respect to the combinations of crystalline materials that may be used to fabricate the GMC and the SAC in method 1100, such combinations may include:

[0196] 1. The GMC is a ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and the SAC is (a) a ceramic vanadium-doped yttrium aluminum garnet (V 3+ In this alternative, Nd:YAG and SAC selected from the group above are both in the form of ceramics. A cobalt-doped crystalline material is a crystalline material doped with cobalt. Examples include cobalt-doped spinel (Co:Spinel or Co 2+ :MgAl2O4), cobalt-doped zinc selenide (Co 2+ :ZnSe). Although not required, the high reflectivity mirror and the output coupler in this option can optionally be rigidly connected to the GM and the SA so that the P-QS laser is a monolithic microchip P-QS laser.

[0197] 2. The GMC is a ceramic neodymium-doped yttrium aluminum garnet (Nd:YAG), and the SAC is a non-ceramic SAC selected from the group consisting of: (a) vanadium-doped yttrium aluminum garnet (V3+:YAG) and (b) various cobalt-doped crystalline materials. In such a case, the high-reflectivity mirror and the output coupler are rigidly connected to the GM and the SA, such that the P-QS laser is a monolithic microchip P-QS laser.

[0198] 3. The GMC is a ceramic neodymium-doped rare earth element crystalline material, and the SAC is a plurality of doped crystalline materials selected from the group consisting of: (a) yttrium aluminum garnet (V3+:YAG) doped with trivalent vanadium and (b) various cobalt-doped crystalline materials. Although not required, the high reflectivity mirror and the output coupler in this option can optionally be rigidly connected to the GM and the SA, such that the P-QS laser is a monolithic microchip P-QS laser.

[0199] Referring generally to method 1100, it is noted that one or both of the SAC and the GMC (and optionally one or more intervening crystalline materials, if any) are transparent to wavelengths of interest (eg, SWIR radiation).

[0200] Figure 11B and Figure 11C Several conceptual timelines for performing method 1100 according to various examples of the presently disclosed subject matter are included. To simplify the figures, it is assumed that the SA is a result of the processing of at least one first powder, and the gain medium is a result of the processing of at least one second powder. As described above, the roles can be interchanged.

[0201] Figure 12AAn example of a PS, numbered 1200, is schematically shown, including a photodetector (e.g., PD) 1202 controlled by a voltage-controlled current source (VCCS) 1204. It should be noted that the voltage-controlled current source 1204 can optionally be external to the PS 1200 (e.g., if a single VCCS 1204 provides current to multiple PSs). The VCCS 1204 is a slave current source that delivers a current proportional to a control voltage (labeled VCTRL in the figure). The PSs and PDDs disclosed in this disclosure can include any suitable type of VCCS. Other ("additional") components of the PS 1200 (not shown) are collectively represented by a general box 1206. When used for sensing, PSs such as PS 1200 and photodetectors such as photodetector 1202 may also be referred to below as "active" or "non-referenced" PSs / photodetectors (as opposed to the PSs and photodetectors used to determine the input of the control voltage of the current source).

[0202] Figure 12B Another example of a PS is schematically shown, numbered 1200', which is an example of PS 1200. In PS 1200', additional components 1206 are in the form of a "3T" (three transistor) structure. Any other suitable circuits can be used as the additional components 1206.

[0203] Current source 1204 can be used to provide a current of the same magnitude but opposite direction as the dark current generated by PD 1202, thereby canceling the dark current (or at least reducing it). This is particularly useful if PD 1202 is characterized by a high dark current characteristic. In this way, the charge flowing from the PD to a capacitance (which, as described above, can be provided by one or more capacitors, by the parasitic capacitance of the PS, or a combination thereof) and the charge caused by the dark current can be canceled. In particular, providing a current of a magnitude substantially equal to the dark current by current source 1204 means that the provided current does not cancel the actual electrical signal generated by PD 1202 due to the detected light impinging on PD 1202.

[0204] Figure 13A A PDD 1300 according to many examples of the presently disclosed subject matter is shown. PDD 1300 includes circuitry that can controllably match the current sourced by current source 1204 to the dark current generated by PD 1202, even when the generated dark current is not constant (varies over time). It should be noted that the level of dark current generated by PD 1202 can depend on various parameters, such as operating temperature and the bias voltage supplied to the PD (which can also vary from time to time).

[0205] Reducing the effects of dark current within PS 1200 via PDD 1300 (rather than at later stages of signal processing, whether analog or digital) enables the use of a relatively small capacitor without saturating it or reducing the linearity of its response to the collected charge.

[0206] PDD 1300 includes a PS 1200 for detecting impinging light and a reference PS 1310, the output of which is used by additional circuitry (discussed below) to reduce or eliminate the effects of dark current in PS 1200. Like PS 1200 (and 1200'), reference PS 1310 includes a PD 1302, a VCCS 1304, and optionally other circuitry ("other components," collectively referred to as 1306). In some examples, reference PS 1310 of PDD 1300 can be identical to PS 1200 of PDD 1300. Alternatively, any one or more components of PS 1310 can be identical to a corresponding component of PS 1200. For example, PD 1302 can be substantially identical to PD 1202. For example, VCCS 1304 can be identical to VCCS 1204. Optionally, any one or more components of PS1310 may differ from those of PS1200 (e.g., PDs, current sources, additional circuitry). It should be noted that substantially identical components of PS1200 and PS1310 (e.g., PDs, current sources, additional circuitry) may be operated under different operating conditions. For example, different bias voltages may be supplied to PDs 1202 and 1302. For example, different components of additional components 1206 and 1306 may be operated using different parameters or selectively connected / disconnected, even when their structures are substantially identical. For simplicity and clarity, components of PS1310 are numbered 1302 (for the PDs), 1304 (for the VCCS), and 1306 (for the additional circuitry), but this does not imply that these components are different from components 1202, 1204, and 1206.

[0207] In some examples, reference additional circuit 1306 can be omitted or disconnected so as not to affect the dark current determination. PD 1202 can operate under any of the following conditions: reverse bias, forward bias, zero bias, or selectively between any two or three of the above biases (e.g., controlled by a controller such as controller 1338 discussed below). PD 1302 can operate under any of the following conditions: reverse bias, forward bias, zero bias, or selectively between any two or three of the above biases (e.g., controlled by a controller such as controller 1338 discussed below). PDs 1202 and 1302 can operate at substantially the same bias voltage (e.g., approximately -5V, approximately 0V, approximately +0.7V), which is not required (e.g., when testing PDD 1300, as discussed in more detail below). Optionally, a single PS of the PDD 1300 can sometimes operate as a PS 1200 (detecting light from a field of view (FOV) of the PDD 1300) and sometimes operate as a PS 1310 (whose detection signal output is used to determine a control voltage for a VCCS of another PS 1200 of the PDD). Optionally, the roles of the "active" PS and the reference PS used to detect impinging light can be swapped. The PDD 1300 also includes a control-voltage generating circuitry 1340 that includes at least an amplifier 1318 and multiple electrical connections to multiple PSs of the PDD 1300. The amplifier 1318 has at least two inputs: a first input 1320 and a second input 1322. The first input 1320 of the amplifier 1318 is supplied with a first input voltage (V FI ), which may be directly controlled by a controller (implemented on PDD 1300, on an external system, or a combination thereof), or derived from other voltages in the system (which in turn may be controlled by the controller). A second input 1322 of amplifier 1318 is connected to the cathode of PD 1302 (referenced to PS 1310).

[0208] In a first example use case, the PD 1202 is maintained at a first voltage (also referred to as “anode voltage”, denoted as V A ) and a second voltage (also called “cathode voltage”, denoted as V C). The anode voltage V can be controlled directly by the controller (implemented on the PDD 1300, on an external system, or a combination thereof) or derived from other voltages in the system (which can in turn be controlled by the controller). The cathode voltage can be controlled directly by the controller (implemented on the PDD 1300, on an external system, or a combination thereof) or derived from other voltages in the system (which can in turn be controlled by the controller). The anode voltage V A and the cathode voltage V C Each of the above voltages may be constant or not constant over time. For example, the anode voltage V A Can be provided by a constant source (e.g., from an external controller via a pad). Depending on the implementation, the cathode voltage V C For example, when a 3T structure is used in PS 1200, V C Varies with time. C It may optionally be determined / controlled / influenced by a number of additional components 1206 (instead of the reference circuit).

[0209] VCCS 1204 is used to provide (feed) a current to the cathode terminal of PD 1202 to cancel the dark current generated by PD 1202. It should be noted that at other times, VCCS 1204 can feed other currents to achieve other purposes (such as for calibration or testing PDD 1300). The level of the current generated by VCCS 1204 is controlled in response to an output voltage of amplifier 1318. The control voltage used to control VCCS 1204 is labeled V CTRL , can be the same as an output voltage of amplifier 1318 (as shown). Alternatively, V CTRL The voltage may be derived from the output of amplifier 1318 (eg, due to a resistance or impedance between the output of amplifier 1318 and VCCS 1204 ).

[0210] To cancel (or at least reduce) the effect of the dark current of PD 1202 on the output signal of PS 1200, PDD 1300 can subject PD 1302 to substantially the same bias voltage as that to which PD 1202 is subjected. For example, when PD 1302 is substantially identical to PD 1202, subjecting PD 1302 and PD 1202 to the same bias voltage can be used. One method of supplying the same bias voltage to both PDs (1202 and 1302) is to supply a voltage V to the anode of PD 1302. A(where the supplied voltage is denoted as VRPA, and RPA stands for “reference PD anode”), and the cathode of PD 1302 is supplied with a voltage V C (where the applied voltage is denoted as V RPC , RPC stands for "reference PD cathode"). Another way to supply the same bias voltage is to RPA =V A +ΔV is supplied to the anode of PD 1302, and V RPC =V C +ΔV is supplied to the cathode of PD 1302. Alternatively, the anode voltage V A , reference anode voltage V RPA Or both may be provided by an external power source (eg, via a printed circuit board (PCB) to which PDD 1300 is connected).

[0211] As described above, the first input 1320 of the amplifier 1318 is supplied with a first input voltage V FI A second input 1322 of amplifier 1318 is connected to the cathode of PD 1302. The operation of amplifier 1318 reduces the voltage difference between its two inputs (1320 and 1322), thereby causing the voltage on the second input 1322 to tend towards the voltage supplied to the first input (V FI ) of the same controlled voltage. Now refer to Figure 13B , where the dark current on PD 1302 (denoted as DC in the following) 参考 ) is represented by an arrow 1352 (the circuit shown in the figure is Figure 13A 1302). During the time that PD 1202 remains in the dark condition, the current on PD 1302 is equal to the dark current of PD 1202. PDD 1300 (or any system component connected to it or adjacent to it) may block light to PD 1302, so that it remains in the dark. The blocking can be done by physical barriers (such as opaque barriers), by optical devices (such as many steering lenses), by electronic shutters, and the like. In the following description, it is assumed that all current on PD 1302 is dark current generated by PD 1302. Alternatively, if PD 1302 is subjected to light (such as many low levels of known stray light in the system), a current source can be implemented to offset the known light-origin signal, or the first input voltage V FIThe barriers, optics, or other specialized components designed to direct light away from PD 1302 may be implemented at the wafer level (on the same wafer from which PDD 1300 is fabricated), may be attached to that wafer (e.g., using an adhesive), may be rigidly attached to a housing in which the wafer is mounted, or the like.

[0212] Assume V FI is constant (or slowly varying), the output of VCCS 1304 (indicated by arrow 1354) must be equal in magnitude to the dark current of PD 1302 (DC 参考 ), which means that VCCS 1304 provides charge carriers for the dark current consumption of PD 1302, thereby allowing the voltage to remain at VFI. Since the output of VCCS 1304 is controlled by VCTRL, which is responsive to the output of amplifier 1318, amplifier 1318 is operated to output the desired output so that VCTRL will control the output of VCCS 1304, which will be the same in magnitude as the dark current on PD 1302.

[0213] If PD 1202 is substantially identical to PD 1302 and VCCS 1204 is substantially identical to VCCS 1304, the output of amplifier 1318 will also cause VCCS 1204 to provide the same level of current (DC) to the cathode of PD 1202. 参考 In such a case, in order for the output of VCCS 1204 to cancel the dark current (hereinafter referred to as DC) generated by PD 1202, 有源PD ), it is required that both PD 1202 and PD 1302 will generate a similar level of dark current. In order to subject both PDs (1202 and 1302) to the same bias voltage (which will cause both PDs to generate substantially the same level of dark current because both PDs are maintained at substantially the same conditions such as temperature), the voltage provided to the first input of amplifier 1318 is determined in response to the anode voltage and the cathode voltage of PD 1202 and the anode voltage of PD 1302. For example: if V A Equal to V RPA , then it is equal to V C V FI can be provided to the first input 1320. It should be noted that V C can change over time and is not necessarily determined by a controller (e.g. V C1304). If PD 1202 is different from PD 1302 and / or if VCCS 1204 is different from VCCS 1304, the output of amplifier 1318 can be modified by matching electrical components (not shown) between amplifier 1318 and VCCS 1204 to provide a related control voltage to VCCS 1204 (e.g., if it is known that the dark current on PD 1202 is linearly related to the dark current on PD 1302, the output of amplifier 1318 can be modified based on the linear relationship). Another way to supply the same bias voltage is to change V RPA =V A +ΔV is supplied to the anode of PD 1302, and V RPC =V C +ΔV is supplied to the cathode of PD 1302 .

[0214] Figure 13C A photodetection device 1300′ according to many examples of the presently disclosed subject matter is shown, comprising a plurality of PSs 1200. PDD 1300′ comprises all components of PDD 1300, as well as a plurality of additional PSs 1200. The different PSs of PDD 1300′ are substantially identical to one another (e.g., all are part of a two-dimensional PDA), and thus the PDs 1302 of different PSs 1200 generate similar dark currents. Therefore, the same control voltage V CTRL All VCCSs 1204 supplied to the different PSs 1200 of the PDD 1300' are caused to cancel (or at least reduce) the effect of the dark current generated by the respective PDs 1202. Any of the options discussed above with respect to the PDD 1300 may be mutatis mutandis applied to the PDD 1300'.

[0215] In some cases (for example, if V C is not constant and / or unknown), a first input voltage V FI (For example, through a controller), the first input voltage V FI is chosen to induce a similar dark current on PD 1302 as on PD 1202 .

[0216] Now refer to Figure 14 , which shows an exemplary PD IV curve 1400 according to many examples of the presently disclosed subject matter. For ease of illustration, curve 1400 represents the IV curves of both PD 1302 and PD 1202, which are assumed to be substantially identical for the purposes of this description and are subjected to the same anode voltage (i.e., V for purposes of this description). A =V RPA). The IV curve 1400 is relatively flat between voltages 1402 and 1404, which means that different bias voltages between 1402 and 1404 supplied to the associated PD will produce similar levels of dark current. C In a cathode voltage range, given a known V A , which means that the bias voltage on PD 1202 is limited to between voltages 1402 and 1404. Then, supplying a VRPC will cause the bias voltage on PD 1302 to also be between voltages 1402 and 1404, which will cause the VCCS 1204 output to be sufficiently similar to DC 有源PD Even if PD 1202 and PD 1302 are subjected to different bias voltages, V RPC The bias voltage may be within the cathode voltage range (as shown by equivalent voltage 1414) or outside of it (while still maintaining the bias voltage on PD 1302 between 1402 and 1404), as demonstrated by equivalent voltage 1412. Modifications to other configurations, such as those discussed above, may be implemented accordingly. It should be noted that different bias voltages may also be supplied to different PDs 1202 and 1302 for other reasons. For example, different bias voltages may be supplied as part of testing or calibration of the PDA.

[0217] In reality, the different PDs (or other components) of different PSs in a single PDD are not made exactly the same, and the operation of these PSs is not exactly the same as each other. In a PD array, many PDs may be slightly different from each other, and the dark current may vary (for example, due to manufacturing differences, slight temperature differences, etc.).

[0218] Figure 15 A control voltage generating circuit 1340 is shown connected to a plurality of reference photosensitive sites 1310 (collectively 1500 ) according to examples of the present invention. Figure 15 The circuit (also referred to as reference circuit 1500) can be used to determine a control voltage (denoted as V) for one or more VCCSs 1204 corresponding to one or more PSs 1310 of multiple PDDs 1300, 1300' and any PDD variations discussed in this disclosure. CTRLIn particular, reference circuit 1500 can be used to determine a control voltage based on data collected from multiple reference PSs 1310 that differ to some extent (e.g., as a result of manufacturing inaccuracies, varying operating conditions, etc.) to offset (or limit) the effects of dark current in one or more PSs 1200 of a PDD. As previously discussed, the dark currents of multiple PDs can differ from one another even if they are similar. It should be noted that in certain PD technologies, multiple PDs with the same intent may feature dark currents that differ by a factor of x1.5, x2, x4, or even more. The averaging mechanism discussed herein allows even such significant differences (e.g., in manufacturing) to be compensated for. With amplifier 1318 connected to multiple reference PSs 1310 to average the dark current levels of several PSs 1310, such multiple PSs 1310 are maintained in darkness, for example, using any of the mechanisms discussed above. The voltages supplied to the different VCCSs 1304 of the various PSs 1310 are short-circuited, causing all VCCSs 1304 to receive substantially the same control voltage. The cathode voltages of the different reference PDs 1302 are shorted to different networks. Thus, although the currents in the different reference PSs 1310 are slightly different from each other (because the reference PSs 1310 are slightly different from each other), the average control voltage supplied to the one or more PSs 1200 of each PDD (which may also be slightly different from each other and from the reference PS 1310) is accurate enough to offset the effects of dark current on the different PSs 1200 in a sufficiently uniform manner. Optionally, the output voltage of a single amplifier 1318 is supplied to all PSs 1200 and all reference PSs 1310. Optionally, the selected PDs for the PDD have a flat IV response (as described above, e.g., with respect to Figure 14 ), so that the average control voltage discussed with respect to the reference circuit 1500 cancels the dark current in the different PS 1200 to a very good degree. Figure 16A and Figure 16BA number of non-limiting examples of PDDs are provided, which include multiple reference PSs 1310 whose average output signals are used to modify the multiple output signals of multiple active PSs 1200 (for example, to reduce the impact of dark current on the output signals). Different configurations, geometries, and numerical ratios can be implemented between the multiple reference PSs 1310 and the multiple active PSs 1200 of a single PDD. For example: in a rectangular photodetector array including multiple PSs arranged in multiple rows and multiple columns, an entire row of PSs (for example, 1,000 PSs) or multiple rows or columns of PSs can be used as multiple reference PSs 1310 (and optionally kept in the dark), while the rest of the array receives the control signal based on the average of the outputs of those reference PS rows. This method of generating control current significantly reduces the impact of dark current by eliminating the average dark current, leaving only PS-to-PS variations.

[0219] Figure 16A and Figure 16B 16 shows a plurality of photodetection devices according to many examples of the subject matter of the present disclosure, the plurality of photodetection devices including an array of a plurality of PSs and a reference circuit based on a plurality of PDs. Figure 16A shown) and PDD1600'( Figure 16B 1300, and multiple additional PSs 1200 and 1310. Optionally, the different PSs of PDD 1600 (and, respectively, PDD 1600') are substantially identical to one another. Any of the options discussed above with respect to multiple PDDs 1300 and 1300' and with respect to circuit 1500 may be applied mutatis mutandis to PDDs 1600 and 1600'.

[0220] Figure 16AA photodetector device 1600 is shown, comprising a photosensitive region 1602 (which is exposed to external light during operation of the photodetector device 1600), a region 1604 having a plurality (array) of PSs 1200, a region 1604 having a plurality of reference PSs 1310 that are kept in the dark (at least during reference current measurement, optionally at all times), and a control voltage generation circuit 1340, and further comprising a controller 1338. The controller 1338 can control the operation of the amplifier 1318, the voltage supplied to the amplifier 1318, and / or the operation of the plurality of reference PSs 1310. Optionally, the controller 1338 can also control various operations of the plurality of PSs 1200 and / or other components of the PDD 1600. Controller 1338 can control both the multiple active PSs 1200 and the multiple reference PSs 1310 to operate under the same operating conditions (e.g., bias voltage, exposure time, and management readout regime). It should be noted that any function of controller 1338 can be implemented by an external controller (e.g., implemented on another processor of an EO system in which the PDD is installed, or by an auxiliary system such as a controller of an autonomous vehicle in which the PDD is installed). Alternatively, controller 1338 can be implemented as one or more processors that are manufactured on the same wafer as other components of PDD 1600 (e.g., multiple PSs 1200 and 1310, amplifier 1318). Alternatively, controller 1338 can be implemented as one or more processors that are located on a PCB connected to such a wafer. Other suitable controllers can also be implemented as controller 1338.

[0221] Figure 16BA photodetector device 1600' is shown according to various examples of the presently disclosed subject matter. Photodetector device 1600' is similar to device 1600, but has various components arranged in a different geometry and does not show the internal details of various PSs. Also illustrated is readout circuitry 1610, which is used to read the detection signals from multiple PSs 1200 and provide them for further processing (e.g., for noise reduction, image processing), storage, or any other purpose. For example, readout circuitry 1610 can sequentially and temporarily arrange the readout values of different PSs 1200 (possibly after some processing by one or more processors of the PDD, not shown) before providing them for further processing, storage, or any other action. Alternatively, readout circuitry 1610 can be implemented as one or more units fabricated on the same wafer as other components of PDD 1600 (e.g., multiple PSs 1200 and 1310, amplifier 1318). Alternatively, the readout circuit 1610 may be implemented as one or more units on a PCB connected to such a wafer. Other suitable readout circuits may also be implemented as the readout circuit 1610. It should be noted that a readout circuit such as the readout circuit 1610 may be implemented in any photodetection device discussed in this disclosure (e.g., multiple PDDs 1300, 1700, 1800, and 1900). Prior to an optional digitization of the signal, many examples of analog signal processing may be performed in the PDD (e.g., by the readout circuit 1610 or one or more processors of the corresponding PDD), including: modifying gain (amplification), offset, and merging (combining multiple output signals from two or more PSs). The digitization of the readout data may be implemented on or outside the PDD.

[0222] Optionally, the PDD 1600 (or any other PDD disclosed in this disclosure) may include: a sampling circuit for sampling the output voltage of the amplifier 1318 and / or the control voltage V CTRL1310 is a system circuit that provides a plurality of sampling circuits, each of which is configured to provide ...

[0223] Figure 17 and Figure 18 More photodetection devices according to many examples of the presently disclosed subject matter are shown. In the photodetection devices described above (e.g., 1300, 1300', 1600, 1600'), a voltage-controlled current source is used for the multiple active PSs 1200 and the multiple reference PSs 1310. A current source is an example of a voltage-controlled current circuit that can be used in the disclosed PDD. Another type of voltage-controlled current circuit that can be used is a voltage-controlled current sink, the current absorbed by which is controlled in magnitude by the control voltage supplied to it. For example, a current sink can be used, wherein the bias voltage on the multiple PDs (1202, 1302) is opposite in direction to the bias voltage exemplified above. More generally, whenever a voltage-controlled current source (1204, 1304) is discussed above, this component can be replaced by a voltage-controlled current sink (labeled as 1704 and 1714, respectively). It should be noted that using a current sink instead of a current source may require different types of components or circuits to be used in other parts of the corresponding PDD. For example, an amplifier 1318 used with multiple VCCSs 1204 and 1304 may differ in power, size, and other aspects from an amplifier 1718 used with multiple voltage-controlled current sinks 1704 and 1714. To distinguish multiple PSs that include multiple voltage-controlled current sinks instead of multiple VCCSs, reference numerals 1200' and 1310' correspond to the multiple PSs 1200 and 1300 discussed above.

[0224] exist Figure 17In FIG, a PDD 1700 includes voltage-controlled current circuits that are voltage-controlled current sinks (in both PS 1200′ and PS 1310′), and a suitable amplifier 1718 is used in place of amplifier 1318. All variations discussed above with respect to current sources also apply to current sinks.

[0225] exist Figure 18 In FIG, a PDD 1800 includes two types of voltage-controlled current circuits, voltage-controlled current sources 1204 and 1314 and voltage-controlled current sinks 1704 and 1714, and matched amplifiers 1318 and 1718. This can allow, for example, the multiple PDs of PDD 1800 to be operated in forward or reverse bias. At least one switch (or other selection mechanism) can be used to select which reference circuit is activated / deactivated, the one based on multiple VCCSs or the one based on multiple voltage-controlled current sinks. Such a selection mechanism can be implemented, for example, to prevent two feedback regulators from operating "against" each other (e.g., if operating with a near-zero bias on the PD). Any options, interpretations, or variations discussed above with respect to any previously discussed multiple PDDs (e.g., 1300, 1300', 1600, 1600') can be applied mutatis mutandis to multiple PDDs 1700 and 1800. In particular, the plurality of PDDs 1700 and 1800 may include: a plurality of PSs 1200' and / or a plurality of reference PSs 1310', similar to the discussion above (e.g., regarding Figure 15 、 16A and 16B).

[0226] It should be noted that in any of the multiple photodetection devices discussed above, one or more of the PSs (e.g., the PSs of a photodetection array) can be optionally controllable to selectively act as a reference PS 1310 (e.g., sometimes) or as a regular PS 1200 (e.g., other times). Such a PS may include the circuitry required to operate in both roles. For example, if the same PDD is used in different types of electro-optical systems, it can be used. For example, one system may require an average with an accuracy of between 1,000 and 4,000 reference PSs 1310, while another system may require a lower accuracy, which can be achieved by averaging between 1 and 1200 reference PSs 1310. In another example, as described above, when the entire PDA is dimmed and stored in a sample-and-hold circuit, an average of the control voltages based on some (or even all) of the PSs can be performed, and all of the PSs can be used to detect FOV data using the determined control voltages in one or more subsequent frames.

[0227] It should be noted that in the above discussion, for simplicity, it is assumed that the anode side of all PDs on each PDA is connected to a known (and possibly controlled) voltage, and the multiple detection signals and multiple VCCS connections, and multiple additional circuits are implemented on the cathode side. It should be noted that, alternatively, the multiple PDs 1202 and 1302 can be connected in a similar manner (where the readout is on the anode side, and so on).

[0228] With reference to all of the PDDs discussed above (e.g., 1300, 1600, 1700, 1800), it is noted that the multiple PSs, the readout circuits, the reference circuits, and the other components described above (as well as any additional components that may be required) can be implemented on a single wafer or on more than one wafer, on one or more PCBs, or on another suitable type of circuit connected to the multiple PSs, and so on.

[0229] Figure 19 The present invention illustrates a PDD 1900 according to various examples of the presently disclosed subject matter. The PDD 1900 may implement any combination of features from one or more of the PDDs described above, and further include a number of additional components. For example, the PDD 1900 may include any one or more of the following components:

[0230] a. At least one light source 1902 operable to emit light into the FOV of the PDD 1900. Some of the light from the light source 1902 is reflected from objects in the FOV and captured by the plurality of PSs 1200 in the photosensitive region 1602 (which are exposed to external light during operation of the photodetector assembly 1900) and used to generate an image or other model of the plurality of objects. Any suitable type of light source (e.g., pulsed, continuous, modulated LED, laser) may be used. Optionally, the operation of the light source 1902 may be controlled by a controller (e.g., controller 1338).

[0231] b. A physical barrier 1904 is used to maintain region 1604 of the detector array in darkness. Physical barrier 1904 can be part of the detector array or external to it. Physical barrier 1904 can be fixed or movable (e.g., a movable shutter). It should be noted that other types of dimming mechanisms can also be used. Optionally, physical barrier 1904 (or other dimming mechanism) can dim different portions of the detector array at different times. Optionally, the operation of barrier 1904, if variable, can be controlled by a controller (e.g., controller 1338).

[0232] c. Ignored Photosensitive Sites 1906. It should be noted that not all PSs of the PDD are necessarily used for detection (PSs 1200) or as references (PSs 1310). For example, some PSs may be located in an area that is neither fully dark nor fully illuminated, and therefore are ignored in the generation of the image (or other type of output generated in response to the detection signals of PSs 1200). Alternatively, PDD 1900 may ignore different PSs at different times.

[0233] d. At least one processor 1908 for processing the plurality of detection signals output by the plurality of PSs 1200. Such processing may include, for example, signal processing, image processing, spectral analysis, etc. Optionally, the processing results of processor 1908 may be used to modify the operation of controller 1338 (or another controller). Optionally, controller 1338 and processor 1908 may be implemented as a single processing unit. Optionally, the processing results of processor 1908 may be provided to any one or more of the following: a tangible memory module 1910 for use with a plurality of external systems (e.g., a remote server or a vehicle computer of a vehicle in which PDD 1900 is installed), for example, via a communication module 1912; a display 1914 for displaying images or other types of results (e.g., graphs, textual results from a spectrometer); another type of output interface (e.g., a speaker (not shown)); and so on. It should be noted that, optionally, multiple signals from multiple PSs 1310 may also be processed by processor 1908, for example, to evaluate a condition of PDD 1900 (eg, operability, temperature).

[0234] e. A memory module 1910 for storing at least one of the detection signals output by the active PSs or the readout circuit 1610 (if different), and detection information generated by the processor 1908 by processing the detection signals.

[0235] f. Power supply 1916 (eg, battery, alternating current (AC) power adapter, direct current (DC) power adapter). The power supply can provide power to the multiple PSs, the amplifier, or any other components of the PDD.

[0236] g. A hard casing 1918 (or any other type of structural support).

[0237] h. Optics 1920 for directing light from light source 1902 (if implemented) to the FOV and / or for directing light from the FOV to the plurality of active PSs 1200. Such optics may include, for example, lenses, mirrors (fixed or movable), prisms, filters, and the like.

[0238] As described above, the multiple PDDs described above can be used to match the control voltage, which determines the current level provided by the at least one first voltage-controlled current circuit (VCCC) 1204 to account for differences in the operating conditions of the PDDs, which changes the variation of the multiple levels of dark current generated by the at least one PD 1202. For example: for a PDD including multiple PS1200 and multiple PS1320: when the PDD operates at a first temperature, the control voltage generating circuit 1340 responds to the dark currents of the multiple reference PDs 1302 and provides a control voltage to the voltage-controlled current circuit for providing a current at a first level at a first temperature to reduce the impact of the multiple dark currents of the active PDs 1202 on the outputs of the multiple active PSs 1200; and when the PDD operates at a second temperature (higher than the first temperature), the control voltage generating circuit 1340 responds to the dark currents of the multiple reference PDs 1302 and provides a control voltage to the voltage-controlled current circuit for providing a current at a second level to reduce the impact of the dark currents of the multiple active PDs 1202 on the outputs of the multiple active PSs 1200, so that the second level is greater in magnitude than the first level.

[0239] Figure 20 1 is a flow chart of a method 2000 for compensating for dark current in a photodetector according to various examples of the subject matter of the present disclosure. Method 2000 is performed in a PDD comprising at least: (a) a plurality of active PSs, each active PS comprising at least one active PD; (b) at least one reference PS comprising a reference PD; (c) at least one first VCCC connected to one or more active PDs; (d) at least one reference VCCC connected to one or more reference PDs; and (e) a control voltage generating circuit connected to the active VCCC and the reference VCCC. For example, method 2000 may be performed in any of the plurality of PDDs 1300', 1600, 1600', 1700, and 1800 (the latter two comprising a plurality of active PSs in various implementations). It should be noted that method 2000 may include performing any of the actions or functions discussed above with respect to any of the components of the various aforementioned PDDs.

[0240] Method 2000 includes at least a plurality of stages (stages) 2010 and 2020. Stage 2010 includes generating a control voltage based on a level of dark current in the at least one reference PD, which, when supplied to the at least one reference VCCC, causes the at least one reference VCCC to generate a current that reduces an effect of the dark current of the reference PD on an output of the reference PS. Stage 2020 includes supplying the control voltage to the at least one first VCCC, thereby causing the at least one first VCCC to generate a current that reduces an effect of the dark current of the plurality of active PDs on the plurality of outputs of the plurality of active PSs. VCCC stands for "Voltage Controlled Current Circuit" and can be implemented as a voltage-controlled current source or a voltage-controlled current sink.

[0241] Optionally, stage 2010 is implemented using an amplifier that is part of the control voltage generating circuit. In such a case, stage 2010 includes supplying a first input voltage to a first input of the amplifier while a second input of the amplifier is electrically connected between the reference PD and the reference voltage control circuit. The amplifier can be used to continuously reduce a difference between an output of the reference voltage control circuit and the first input voltage, thereby generating the control voltage. Optionally, both the first VCCC(s) and the reference VCCC(s) are connected to an output of the amplifier.

[0242] In the case where the PDD includes a plurality of different reference PDs generating different levels of dark current, stage 2010 may include generating a single control voltage based on an average of the different dark currents of the plurality of reference PDs.

[0243] Method 2000 may include preventing light from a field of view of the PDD from reaching the plurality of reference PDs (eg, using a physical barrier or steering optics).

[0244] The method 2000 may include sampling the plurality of outputs of the plurality of active PSs after reducing the effects of the dark current, and generating an image based on the plurality of sampled outputs.

[0245] Figure 212 is a flow chart illustrating a method for compensating dark current in a photodetector device according to examples of the presently disclosed subject matter. Method 2100 has two phases, which are performed in different temperature regimes: a first group of phases (2110-2116) is performed when the PDD operates at a first temperature (T1), and a second group of phases (2120-2126) is performed when the PDD operates at a second temperature (T2) that is higher than the first temperature. The first and second temperatures may vary in different implementations or different instances of method 2100. For example, the temperature difference may be at least 5°C; at least 10°C; at least 20°C; at least 40°C; at least 100°C, and so on. In particular, method 2100 may be effective at even smaller temperature differences (e.g., less than 1°C). Note that each of the first and second temperatures may be implemented as a temperature range (e.g., spanning 0.1°C; 1°C; 5°C or higher). Any temperature within the second temperature range is higher than any temperature within the first temperature range (e.g., according to the plurality of ranges mentioned above). Method 2100 can optionally be performed in any of the PDDs discussed above (1300, 1600, etc.). It is noted that method 1020 can include performing any of the actions or functions discussed above with respect to any of the components of the various aforementioned PDDs, and that the PDD of method 1020 can include any combination of one or more of the components discussed above with respect to any one or more of the aforementioned PDDs.

[0246] Referring to a plurality of stages performed when the PDD is operating at a first temperature (which may be a first temperature range): Stage 2110 includes determining a first control voltage based on a dark current of at least one reference PD of the PDD. Stage 2112 includes providing the first control voltage to a first VCCC coupled to at least one active PD of an active power supply (PS) of the PDD, thereby causing the first VCCC to impose a first dark-current countering current in the active power supply (PS). Stage 2114 includes generating a first detection current by the active power supply (PD) in response to: (a) light impinging on the active power supply (PD) from an object in a field of view of the PDD, and (b) dark current generated by the active power supply (PD). Stage 2116 includes outputting a first detection signal by the active power supply (PS) in response to the first detection current and the first dark-current countering current, the first detection signal being less in magnitude than the first detection current, thereby compensating for the effect of dark current on the first detection signal. Method 2100 may also include an optional stage 2118 of generating at least one first image of a FOV of the PDD based on a plurality of first detection signals from a plurality of PSs (and optionally all) of the PDD. Stage 2118 may be performed when the PDD is at the first temperature or at a subsequent stage.

[0247] Referring to a plurality of stages performed when the PDD operates at a second temperature (which may be a second temperature range), stage 2120 includes determining a second control voltage based on the dark current of at least one reference PD of the PDD. Stage 2122 includes providing the second control voltage to the first VCCC, thereby causing the first VCCC to apply a second dark current suppression current in the active PS. Stage 2124 includes generating a second detection current by the active PS in response to: (a) light impingement on the active PS from the object, and (b) dark current generated by the active PS. Stage 2126 includes outputting a second detection signal by the active PS having a magnitude less than the second detection current in response to the second detection current and the second dark current suppression current, thereby compensating for the effect of dark current on the second detection signal. The magnitude of the second dark current suppression current is greater than the magnitude of the first dark current suppression current, and may be by any ratio greater than one. For example, the ratio may be a factor of at least two or significantly higher (e.g., on the order of one, two, three, or more magnitudes). Method 2100 may also include an optional stage 2128 of generating at least one second image of a FOV of the PDD based on a plurality of second detection signals from a plurality of PSs (and optionally all) of the PDD. Stage 2128 may be performed when the PDD is at the second temperature or at a subsequent stage.

[0248] Optionally, a first level of radiation (L1) impinging on the active PD from the object during a first time (t1) when the first dark current suppressing current is generated is substantially equal to a second level of radiation (L2) impinging on the active PD from the object during a second time (t2) when the second dark current suppressing current is generated, wherein an amplitude of the second detection signal is substantially equal to an amplitude of the first detection signal. It should be noted that, optionally, the PDD according to the present disclosure can be used to detect multiple signal levels that are significantly lower than the multiple levels of dark current generated by its PD at certain operating temperatures (e.g., by an amplitude of one, two, or more orders of magnitude). Therefore, method 2100 can be used to emit multiple output signals of similar levels at two different temperatures, wherein the multiple dark currents are two or more orders of magnitude greater than the multiple detection signals and are significantly different from each other (e.g., by a factor of ×2, ×10).

[0249] Optionally, the determination of the first control voltage and the determination of the second control voltage are performed by a control voltage generating circuit, which includes at least one amplifier, the amplifier having an input, the input being electrically connected between the reference PD and a reference voltage control current circuit, and the reference voltage control current circuit being coupled to the reference PD.

[0250] Optionally, method 2100 may further include: supplying a first input voltage to another input of the amplifier, the level of the first input voltage being determined to correspond to a bias voltage on the active PD. Optionally, method 2100 may include: supplying the first input voltage so that a bias voltage on the reference PD is substantially the same as a bias voltage on the active PD. Optionally, method 2100 may include: when the plurality of active PDs have a plurality of different dark currents, determining the first control voltage and the second control voltage based on different dark currents of a plurality of reference PDs of the PDD, wherein providing the first control voltage includes providing the same first control voltage to a plurality of first voltage-controlled current circuits, each first voltage-controlled current circuit being coupled to at least one active PD among a plurality of active PDs of the PDD having different dark currents, and wherein providing the second control voltage includes providing the same second control voltage to the plurality of first voltage-controlled current circuits.

[0251] Optionally, a plurality of different active PDs simultaneously generate a plurality of different levels of dark current, and a plurality of different reference PDs simultaneously generate a plurality of different levels of dark current, and the control voltage generating circuit provides a common control voltage to the different active PDs based on an average of the plurality of different dark currents of the second PDs. Optionally, method 2100 may include: using dedicated optical devices to guide light from the field of view to the plurality of active PSs of the PDD; and preventing light from the field of view from reaching the plurality of reference PDs of the PDD.

[0252] Figure 222200 is a flow chart illustrating a method 2200 for testing a photodetector device according to various examples of the presently disclosed subject matter. For example, the testing can be performed using any of the aforementioned PDDs. That is, the same circuitry and architecture described above for reducing the effects of dark current can be used for additional purposes, testing multiple detection paths of multiple different photodetectors (PSs) in real time. Optionally, the testing can be performed while the PDD is in operational mode (i.e., not in test mode). In some implementations, some PSs can be tested while exposed to ambient light from the FOV, even while other PSs of the same PDD are capturing an actual image of the FOV (with or without dark current compensation). However, it should be noted that method 2200 can also be optionally implemented in other types of PDDs. It should also be noted that method 2200 can also be optionally implemented using circuits or architectures similar to those discussed above with respect to the aforementioned PDDs, but when the PDs are not characterized by high dark current and dark current reduction is not desired or required. Method 2200 is described as being applied to a single PS, but it can be applied to some or all PSs of a PDD.

[0253] Stage 2210 of method 2200 includes providing a first voltage to a first input of an amplifier of a control voltage generating circuit, wherein a second input of the amplifier is connected to a reference PD and a second current circuit, the second current circuit supplying a current whose level is controlled in response to an output voltage of the amplifier; thereby causing the amplifier to generate a first control voltage for a first current circuit of a PS of the PDD. Referring to the examples described with respect to the previous figures, the amplifier may be amplifier 1318 or amplifier 1718, and the PS may be PS 1310 or PS 1310'. Various examples of providing multiple first voltages to the first input are discussed below.

[0254] Stage 2220 of method 2200 includes reading a first output signal of the PS generated by the PS in response to the current generated by the first current circuit and the current generated by a PD of the PS.

[0255] Stage 2230 of method 2200 includes providing a second voltage different from the first input to the first input of the amplifier, thereby causing the amplifier to generate a second control voltage for the first current circuit. Examples of such second voltages may be discussed below.

[0256] Stage 2240 of method 2200 includes reading a second output signal of the PS generated by the PS in response to the current generated by the first current circuit and the current generated by a PD of the PS.

[0257] Stage 2250 of method 2200 includes determining a defect status of a detection path of the PDD based on the first output signal and the second output signal, the detection path including the PS and readout circuitry associated with the PS. Examples of what types of defects can be detected when using various combinations of first and second voltages are discussed below.

[0258] A first example involves using at least one of the first and second voltages to attempt to saturate the PS (e.g., by supplying a very high current to the PS capacitor via the VCCS, regardless of the actual detection level). Failure to saturate the PS (e.g., receiving a detection signal that is not white, but rather solid black or half-tone) indicates a problem with the associated PS or other components in its readout path (e.g., PS amplifier, sampler, analog-to-digital converter). In such a case, the first voltage (for example) causes the amplifier to generate a control voltage that causes the first current circuit to saturate the PS. In such a case, at stage 2250, the determination of the defect condition may include determining that the PS detection path is malfunctioning in response to determining that the first output signal is not saturated. In such a case, the second voltage may be a voltage that does not cause the PS to saturate (e.g., it causes the VCCS to not source current, but only to compensate for the dark current to prevent current from being collected by the capacitor). Testing whether a PS detection path can be saturated can be performed in real time.

[0259] When attempting to saturate one or more PSs to test the PDD, method 2200 may include reading the first output signal during a first detection frame of the PDD while the PS is exposed to ambient light, wherein the determination of the fault condition is performed in response to reading a saturated output signal during a second detection frame that precedes the first frame after previously determining that the detection path is operational. For example, during an ongoing operation of the PDD (e.g., while capturing a video), if a saturation attempt fails, then a PS may be determined to be defective or unusable after it succeeded at a previous time in the same operation. The test may be performed in a testing frame that is not part of the video, or for individual PSs whose saturated outputs are ignored (e.g., the pixel colors corresponding to these PSs may be complete from multiple adjacent pixels in the frame being tested, such that these PSs are deemed unusable for the span of the frame).

[0260] A second example involves using at least one of the first and second voltages to attempt to drain the PS (e.g., by providing a very high opposite current to the capacitor of the PS through the VCCS, regardless of the actual detection level). Failure to drain the PS (e.g., receiving a detection signal that is not black but rather solid white or half-tone) indicates a problem with the associated PS or other components in its read path. In such a case, the second voltage, for example, causes the amplifier to generate a second control voltage that causes the first current circuit to drain a detection signal caused by field light impinging on the PS. In such a case, at stage 2250, the determination of the defect condition may include determining that the detection path is malfunctioning in response to determining that the second output signal is not being drained. In such a case, the first voltage may be a voltage that does not cause the PS to saturate (e.g., it would cause the VCCS to not source current, only to compensate for the dark current, thereby saturating the capacitor). Testing whether a PS detection path can be drained (e.g., without dimming individual PSs) can be performed in real time.

[0261] When attempting to consume one or more PSs to test the PDD, method 2200 may include reading the second output signal in a third detection frame of the PDD while the PS is exposed to ambient light, wherein the determination of the fault state is performed in response to reading a consumed output signal in a fourth detection frame earlier than the third frame after previously determining that the detection path is operational.

[0262] Another example of using method 2200 to test a PS by supplying multiple control voltages includes supplying more than two voltages. For example, three or more different voltages may be supplied to a first input of an amplifier at different times (e.g., in different frames). In such a case, stage 2250 may include determining the defect state of the detection path of the PDD based on the first output signal, the second output signal, and at least one other output signal corresponding to the third or more voltages supplied to the first input of the amplifier. For example, three, four, or more different voltages may be supplied to the first input of the amplifier at different times (e.g., monotonically, where each voltage is greater than a previous voltage), and the multiple output signals of the same PS corresponding to the different voltages may be tested to correspond to the multiple supplied voltages (e.g., the multiple output signals also increase monotonically in amplitude).

[0263] An example of using method 2200 to test a portion (or even all) of the PDD includes reading at least two output signals from each of a plurality of PSs of the PDD in response to at least two different voltages provided to the amplifier of the corresponding PS, determining an operating state for at least one first detection path based on the at least two output signals output by at least one PS associated with the corresponding first detection path, and determining a fault state for at least one second detection path based on the at least two output signals output by at least one other PS associated with the corresponding second detection path.

[0264] Optionally, method 2200 may be performed in conjunction with multiple specified test targets (e.g., black targets, white targets) when the PDD is shielded from ambient light and / or when specified illumination is used (e.g., of a known amplitude, dedicated illumination, etc.), but this is not required.

[0265] Optionally, stage 2250 can be replaced by determining an operating state of the detection path. For example: this can be used to calibrate multiple different PSs of the PDD to the same level. For example: when the PDD is dimmed and there is no dedicated target or dedicated lighting, the same voltage can be supplied to the VCCS of the different PSs. The different output signals of the different PSs can be compared with each other (at one or more different voltages supplied to the first input of the amplifier). Based on the comparison, multiple correction values can be assigned to different PS detection paths so that they will provide a similar output signal (simulated by the current contained in the multiple VCCS of the different PSs) for similar lighting levels. For example: it can be decided that the output of PS A should be multiplied by 1.1 to output a calibrated output signal to PS B. For example: it can be decided that an incremental signal ΔS should be added to the output of PS C to output a calibrated output signal to the PSD. Non-linear correction can also be implemented.

[0266] Figure 23 An EO system 2300 is illustrated according to various examples of the presently disclosed subject matter. EO system 2300 includes at least one PDA 2302 and at least one processor 2304 operable to process a plurality of detection signals from a plurality of PSs 2306 of the PDA. EO system 2300 can be any type of EO system that uses a PDA for detection, such as a camera, spectrometer, LIDAR, or the like.

[0267] The at least one processor 2304 is operable and configured to process the plurality of detection signals output by the plurality of PSs 2306 of the at least one PDA 2302. Such processing may include, for example, signal processing, image processing, spectral analysis, etc. Optionally, the processing results of the processor 2304 may be provided to any one or more of: a tangible memory module 2308 (for storage or later retrieval), an external system (e.g., a remote server or a vehicle computer of a vehicle in which the EO system 2300 is installed) such as via a communication module 2310, a display 2312 for displaying an image or other type of result (e.g., a graph, textual results from a spectrometer), another type of output interface (e.g., a speaker, not shown), and the like.

[0268] EO system 2300 can include a controller 2314 that controls various operating parameters of EO system 2300 (e.g., PDA 2302 and an optional light source 2316). In particular, controller 2314 can be configured to set (or otherwise change) the frame exposure times used by EO system 2300 to capture different frames. Optionally, results of processing the light detection signals by processor 2304 can be used to modify the operation of controller 2314. Optionally, controller 2314 and processor 2304 can be implemented as a single processing unit.

[0269] EO system 2300 may include at least one light source 2316 operable to emit light into the field of view (FOV) of EO system 2300. Some light from light source 2316 is reflected from objects in the FOV and captured by PSs 2306 (at least those PSs located in a photosensitive area exposed to external light during the multiple frame exposure times of EO system 2300). Detecting light from multiple objects in the FOV (whether reflected from the light source, reflected from other light sources, or radiated light) is used to generate an image or other model (e.g., a three-dimensional depth map) of the multiple objects. Any suitable type of light source may be used (e.g., pulsed, continuous, modulated, LED, laser). Optionally, operation of light source 2316 may be controlled by a controller (e.g., controller 2314).

[0270] The EO system 2300 can include a readout circuit 2318 for reading a plurality of electrical detection signals from a plurality of different PSs 2306. Optionally, the readout circuit 2318 can process the plurality of electrical detection signals before providing them to the processor 2304. Such pre-processing can include, for example, amplification, sampling, weighting, denoising, correcting, digitization, capping, level-adjustments, dark current compensation, and the like.

[0271] Furthermore, the EO system 2300 may include a number of additional components, such as, but not limited to, one or more of the following optional components:

[0272] a. A memory module 2308 for storing at least one of the plurality of detection signals output by the plurality of PSs 2306 or by the readout circuit 2318 (eg, if different), and detection information generated by the processor 2304 by processing the plurality of detection signals.

[0273] b. A power source 2320 , such as a battery, an AC power adapter, a DC power adapter, or the like. The power source 2320 can provide power to the PDA, readout circuitry 2318 , or any other component of the EO system 2300 .

[0274] c. A hard shell 2322 (or any other type of structural support).

[0275] d. Optics 2324 for directing light from light source 2316 (if implemented) to the FOV and / or for directing light from the FOV to the PDA 2300. Such optics may include, for example, lenses, mirrors (fixed or movable), prisms, filters, and the like.

[0276] Alternatively, the PDA 2302 may be characterized by relatively high dark current (e.g., as a result of the type and characteristics of its PD). Due to the high level of dark current, the multiple capacitors of the various PSs 2306 that collect the detection charge may become saturated (partially or fully) by the dark current, leaving little or no dynamic range for detecting ambient light (from the FOV). Even if the readout circuitry 2318 or processor 2304 (or any other component of the system 2300) subtracts multiple dark current levels from the detection signal (e.g., to normalize the detection data), the lack of dynamic range for detection means that the resulting detection signal of the various PSs 2306 is too saturated to be used to meaningfully detect multiple ambient light levels. Because the dark current from the PD of each PS 2306 is accumulated in the capacitor (whether actual capacitors or parasitic capacitance or residual capacitance of other components of the multiple PSs) for the entire duration of the frame exposure time (FET), multiple different PSs 2306 with different capacitances may be rendered unusable at multiple different FETs.

[0277] Figure 24An example of a method 2400 for generating image information based on data from a PDA according to the presently disclosed subject matter is illustrated. Referring to the examples described with respect to the previous figures, method 2400 can be performed by EO system 2300 (e.g., by processor 2304, controller 2314, etc.). In such a case, the PDA of method 2400 can optionally be PDA 2302. Other related components discussed in method 2400 can be the corresponding components of EO system 2300. Method 2400 includes modifying a frame FET (FET) in which the PDA collects charge from its PDs. This collected charge can result from a photoelectric response to light impinging on the PDs as well as from inherent sources within the detection system, such as dark current in the PDs. The impinging light can arrive from, for example, a field of view (FOV) of a camera or other EO system mounted on the PDA. The FET can be controlled electronically, mechanically, or any combination thereof, such as by controlling the duration of a flash illumination.

[0278] It should be noted that the FET can be a whole FET that is the sum of a plurality of different durations in which the PDA collects charge due to photoelectric activity in a plurality of PSs of the PDA. A whole FET is used where the charge collected over different plurality of different durations is summed to provide a single output signal. Such a whole FET can be used, for example, with pulsed illumination, or with active illumination where the collection is suspended for a short period of time (e.g. to avoid saturation by a bright reflection in the FOV). It should be noted that, optionally, in some frames a single FET can be used, while in other frames the whole FET can be used.

[0279] Stage 2402 of method 2400 includes receiving a first frame of information. For each of a plurality of PSs of a PDA, the first frame of information includes a first frame of detection level indicating an intensity of light detected by the respective PS in a first FET. The receiving of the first frame of information may include receiving a plurality of readout signals from all of the PSs of the PDA, but this is not required. For example, some PSs may be defective and unable to provide a signal. For example, a region of interest (ROI) may be defined for the frame, indicating that data is only collected from a portion of the frame, and so on.

[0280] The frame information may be provided in any format, such as a detection level (or levels) for each PS (e.g., between 0 and 1024, three RGB values, each between 0 and 255, or the like), a scalar, a vector, or any other format. Optionally, the frame information (for the first frame or subsequent frames) may optionally indicate multiple detection signals in an indirect manner (e.g., information about the detection level of a given PS may be given relative to the level of a neighboring PS or relative to the level of the same PS in a previous frame). The frame information may also include additional information (e.g., sequence number, timestamp, operating conditions), some of which may be used in subsequent steps of method 2400. The first frame information (and frame information for subsequent frames received at later stages of method 2400) may be received directly from the PDA, or from one or more intermediate units (e.g., an intermediate processor, a memory unit, a data aggregator, or the like). The first frame information (and frame information for later frames received in later stages of method 2400) may include: the original data obtained by each PS, but may also include: pre-processed data (such as weighted, denoised, corrected, digitized, capped, level adjusted, and the like).

[0281] Stage 2404 includes identifying at least two types of PSs among the plurality of PSs of the PDD based on the first FET:

[0282] a. An available PS group for the first frame (referred to as a "first group of usable PSs") includes at least a first PS, a second PS, and a third PS among the plurality of PSs of the PDA.

[0283] b. An unusable PS group for the first frame (referred to as a "first group of unusable PSs"), comprising at least a fourth PS among the plurality of PSs of the PDA.

[0284] The identification of stage 2404 can be implemented in different ways and can optionally include (explicitly or implicitly) identifying that each of the plurality of PSs belongs to one of the at least two groups mentioned above. Optionally, each PS of the PDA (or each PS of a predetermined subset thereof, such as all PSs of an ROI) can be assigned to one of two pluralities relative to the first frame, the first group of available PSs or the first group of unavailable PSs. However, this is not necessarily required, and some PSs may not be assigned for certain frames, or may be assigned to other pluralities (for example, the availability of multiple PSs is based on a number of parameters other than the FET of the corresponding first frame, such as determined based on collected data). Optionally, the identification of stage 2404 can include determining which PSs match one of the first pluralities and automatically treating the remaining PSs of the PDA (or a predetermined subset thereof, such as an ROI) as belonging to the other of the two pluralities.

[0285] It should be noted that the identification of stage 2404 (and stages 2412 and 2402) does not necessarily reflect an actual availability status of the individual PSs (although in some implementations, it does reflect these actual availability statuses). For example, a PS included in the first unavailable PS group may actually be used under the multiple conditions of the first frame, while another PS included in the first available PS group may actually not be used under the multiple circumstances of the first frame. The identification of stage 2404 is an estimation or assessment of the availability of the multiple PSs of the PDA, rather than a test of the individual PSs. It should also be noted that the availability of multiple PSs may also be estimated in stage 2404 based on other factors. For example, a pre-existing list of defective PSs may be used to exclude such PSs from being considered available.

[0286] The identification of stage 2404 (and stages 2412 and 2420) may include: identifying at least one of the multiple unusable PS groups (and / or at least one of the multiple available PS groups) based on a sum of the durations during which the composite FET includes multiple sampled PSs of the PDD that are sensitive to light, and excluding multiple intermediate times between multiple durations during which the multiple sampled PSs of the PDD are insensitive to light.

[0287] The identification of multiple groups of available and unavailable PSs (in multiple stages 2404, 2412, and / or 2420) can be based in part on an assessment of temperature. Optionally, method 2400 can include processing one or more frames (particularly multiple previous frames or the current frame) to determine a temperature assessment (e.g., by assessing dark current levels in a dark frame or in multiple darkened PSs not imaged into the FOV). Method 2400 can then include using the temperature assessment to identify a group of available PSs and a group of unavailable PSs for a later frame, which affects the generation of the corresponding image. The temperature assessment can be used to assess how quickly the dark current will saturate the dynamic range of a given PS within the duration of the associated FET. Optionally, the temperature assessment can be used to utilize a parameter of an availability model for the PS (e.g., one generated in method 2500).

[0288] The timing of stage 2404 can vary relative to the timing of stage 2402. For example, stage 2404 can optionally be performed before, simultaneously with, partially simultaneously with, or after stage 2402. Referring to the example figures, stage 2404 can optionally be performed by processor 2304 and / or controller 2314. Examples of methods for performing the identification of stage 2404 are discussed with respect to method 1100.

[0289] Step 2406 includes generating a first image based on the first frame detection levels of the first available PS group, disregarding the first frame detection levels of the first unavailable PS group. The generation of the first image can be implemented using any suitable method and can optionally be based on additional information (e.g., data received from an active lighting unit, and, if used, data from additional sensors such as humidity sensors). Referring to the examples described with respect to the previous figures, it should be noted that stage 2406 can optionally be implemented by processor 2304. It should be noted that the generation can include various stages of processing the signals (e.g., weighting, noise reduction, correction, digitization, capping, level adjustment, and the like).

[0290] With respect to the first group of unavailable PSs, it should be noted that, since the detection data for those PSs is ignored in the generation of the first image, a plurality of replacement values can be calculated in any suitable manner (if desired). Such a plurality of replacement values can be calculated, for example, based on a plurality of first frame detection levels of a plurality of adjacent PSs, based on a plurality of earlier detection levels of a plurality of earlier frames, based on the same PS (e.g., if available in a previous frame), or based on one or more adjacent PSs (e.g., based on a kinematic analysis of the scene). For example, a Wiener filter, local mean algorithms, non-local mean algorithms, or the like can be used. With reference to the generation of a plurality of images based on the PDA data, optionally, the generation of any one or more such images (e.g., the first image, the second image, and the third image) can include calculating a replacement value for at least one pixel associated with a PS that is identified as unavailable for the corresponding image based on the detection level of at least one other adjacent PS identified as available for the corresponding image. In case a non-binary availability assessment is used (and said identification of stages 2404, 2412 and / or 2420 includes identifying at least one PS as belonging to a third group of partially available PSs), the detection signal of each such PS is partially identified as available, which can be combined or averaged with multiple detection signals of multiple adjacent PSs and / or multiple other readings of multiple identical PSs at other times when they were available (or partially available).

[0291] Optionally, the generation of the first image (and later the generation of the second and third images) may further include disregarding outputs of multiple PSs that are determined to be defective, inoperative, or unavailable for any other reason, or a test path that is determined to have a defective, inoperative, or unavailable. An example of an additional method for detecting defects in multiple PSs and / or multiple associated test paths is discussed with respect to method 2200, which may be combined with method 2400. The outputs of method 2200 may be used to generate stages 2406, 2414, and 2422. In such a case, method 2200 may be executed periodically and provide outputs for generating the multiple images, or may be specifically triggered according to method 2400 for the generation of the multiple images.

[0292] Optionally, the generation of the first image (and later the second and third images) may include, when a PS is determined to be available, calculating a replacement value for at least one pixel associated with the PS, which is identified as unavailable for the corresponding image, based on a detection level of the PS being measured. Such information may be used together with information of multiple adjacent PSs or independently thereof. Using multiple detection levels of a PS from other times may include, for example, considering multiple detection levels from multiple previous frames (e.g. for multiple still scenes), using detection information from another snapshot of a series of image acquisitions used to generate a composite image, such as a high dynamic range image (HDRI) or a multi-wavelength composite image (where several shots are taken using different spectral filters and then combined into a single image).

[0293] It is to be noted that in the first image (and in any other frames generated based on the detection data of the PDA), a single pixel may be based on the detection data from a single PS or from a combination of multiple PSs; likewise, the information from a single PS may be used to determine the pixel color of one or more pixels in the image. For example: a field of view of Θ by Φ degrees may be covered by multiple X by Y PSs and may be converted to N by N pixels in the image. A pixel value of one of these M×N pixels may be calculated as Pixel-Value(i,j)=Σ(ap , s·DLp , s), where DLp , s is the detection level of PS(p,s) for the frame, and ap,s is an average coefficient for the specific pixel (i,j).

[0294] After stage 2406, the first image can then be provided to an external system (e.g., a screen monitor, a storage unit, a communication system, an image processing computer). The first image can then be processed using the one or more image processing algorithms. After stage 2406, the first image can then be processed in other ways as desired.

[0295] Stages 2402 through 2406 may be repeated several times for many frames captured by the photodetector sensor, whether or not for multiple consecutive frames. It should be noted that in some implementations, such as if high dynamic range (HDR) imaging techniques are implemented, the first image may be generated based on multiple detection levels for several frames. In other implementations, the first image is generated using multiple first frame detection levels for a single frame. Multiple instances of stages 2402 and 2406 may follow a single instance of stage 2404 (e.g., if the same FET is used for several frames).

[0296] Stage 2408 is executed after receiving the first frame information and includes determining a second FET, the second FET being longer than the first FET. Determining the second FET includes determining a duration of the exposure of the plurality of associated PDs (e.g., in milliseconds, fractions thereof, or multiples thereof). Stage 2408 may also include determining additional timing parameters (e.g., a start time of the exposure), but this is not required. The second FET being longer than the first FET may be selected for any reason. Such a reason may include, for example, any one or more of the following: overall light intensity in the FOV, light intensity in multiple portions of the FOV, use of bracketing techniques, use of high dynamic range photography techniques, aperture variation, and the like. The second FET may be longer than the first FET by any ratio, whether a relatively low value (e.g., ×1.1, ×1.5), a value exceeding a multiple (e.g., ×2, ×5), or a higher value (e.g., ×20, ×100, ×5,000). Referring to the examples of the figures, stage 2408 may optionally be performed by controller 2314 and / or processor 2304. Alternatively, an external system may determine the first FET or influence the setting of the FET via EO system 2300 (e.g., a control system of a vehicle in which EO system 2300 is installed).

[0297] It is noted that, optionally, at least one of stage 2408 and stage 2416 can be replaced by determining a new FET (the second FET and / or the third FET, respectively) in conjunction with an external entity. Such an external entity can be, for example, an external controller, an external processor, or an external system. It is noted that, optionally, at least one of stage 2408 and stage 2416 can be replaced by receiving an indication of a new FET (the second FET and / or the third FET, respectively) from an external entity. The indication of the FET can be explicit (e.g., a duration in milliseconds) or implicit (e.g., an indication of a change in aperture opening and / or exposure value (EV) corresponding to the FET, an indication of flash duration). It is noted that, optionally, at least one of stage 2408 and stage 2416 can be replaced by receiving an indication of the expected dark current (or at least a portion of the dark current to be transferred to the capacitor of the PS, e.g., if dark current mitigation strategies are implemented) from an external entity.

[0298] Stage 2410 includes receiving a second frame of information. The second frame of information includes a second frame detection level for each of the plurality of PSs of the PDA, the second frame detection level indicating an intensity of light detected by the corresponding PS in the second FET. It should be noted that the second frame (in which the detection data for the second frame of information is collected) can directly follow the first frame, but this is not required. The plurality of FETs in any one of the one or more intermediate frames (if any) between the first frame and the second frame can be equal to the first FET, the second FET, or any other FET (longer or shorter). With reference to the example of the accompanying drawings, stage 2410 can optionally be performed by processor 2304 (e.g., via readout circuit 2318).

[0299] Stage 2412 includes identifying at least two types of PSs of the PDA from a plurality of PSs of the PDD based on the second FET:

[0300] a. An available PS group for the second frame (referred to as a "second group of usable PSs") includes the first PS.

[0301] b. An unusable PS group for the second frame (referred to as "a second group of unusable PSs") includes the second PS, the third PS, and the fourth PS.

[0302] That is, due to the longer FET of the second frame, the second and third PSs identified in stage 2404 as belonging to the first group of available PSs (i.e., the aforementioned group of available PSs for the first frame) are identified in stage 2412 as belonging to the second group of unavailable PSs (i.e., the aforementioned group of unavailable PSs for the second frame). The identification in stage 2412 can be implemented in various ways, such as any one or more of those discussed above with respect to stage 2404. For various reasons, PSs that were considered available for shorter FETs may be deemed unavailable for longer FETs in stage 2412. For example, if such PSs have a charge storage capacity (e.g., capacitance) that is lower than the average charge storage capacity of the PSs in the PDA, the charge storage capacity of these PSs may be deemed insufficient for both the detection signal and the accumulated dark current at longer integration times. If the dark current level is maintained (e.g., the temperature and bias voltage on the PD remain constant), any PS that cannot be present in the first FET due to its inability to maintain sufficient dynamic range will also be identified as unavailable for the longer second FET.

[0303] Stage 2412 is performed after stage 2408 (because it is based on the outputs of stage 2408). The timing of stage 2412 relative to the timing of stage 2410 can vary. For example, stage 2412 can optionally be performed before, simultaneously with, partially simultaneously with, or after stage 2410. Referring to the example of the figures, stage 2412 can optionally be performed by processor 2304. Examples of methods for performing the identification of stage 2412 are discussed with respect to method 2500.

[0304] Stage 2414 includes disregarding the second frame detection levels of the second unusable PS group and generating a second image based on the second frame detection levels of the second available PS group. Importantly, stage 2414 includes generating the second image while ignoring the outputs (detection levels) of at least two PSs, whose outputs were used to generate the first image. Based on the FETs of the first frame, these at least two PSs are identified as available and can be used to generate the first image (i.e., at least the second PS and the third PS). Generating the second image can be accomplished using any suitable method, including any of the methods, techniques, and variations discussed above with respect to generating the first image. Regarding the second unusable PS group, it should be noted that since the detection data of those PSs is ignored in generating the second image, replacement values can be calculated using any suitable method (if desired). Following stage 2414, the second image can then be provided to an external system (e.g., a screen monitor, a storage unit, a communication system, an image processing computer), where it can then be processed using one or more image processing algorithms, or can then undergo other processing as desired.

[0305] Stages 2410 through 2414 may be repeated multiple times for a number of frames captured by the photodetector sensor, whether or not multiple consecutive frames. It should be noted that in some implementations, such as if high dynamic range (HDR) imaging techniques are implemented, the second image may be generated based on multiple detection levels for several frames. In other implementations, the second image is generated using multiple second frame detection levels for a single frame. Multiple instances of stages 2410 and 2414 may follow a single instance of stage 2412 (e.g., if the same second FET is used for several frames).

[0306] Step 2416 is performed after receiving the second frame information and includes determining a third FET that is longer than the first FET and shorter than the second FET. The determination of the third FET includes determining a duration of the exposure for the plurality of associated PDs (e.g., in milliseconds, fractions thereof, or multiples thereof). Stage 2416 may also include determining additional timing parameters (e.g., a start time of the exposure), but this is not required. The third FET may be selected for any reason, such as the reasons discussed above with respect to the determination of the second FET in stage 2408. The third FET may be longer than the first FET by any ratio, whether a relatively low value (e.g., ×1.1, ×1.5), a value exceeding a multiple (e.g., ×2, ×5), or any higher value (e.g., ×20, ×100, ×5,000). The third FET can be shorter than the second FET by any ratio, whether a relatively low value (e.g., ×1.1, ×1.5), a multiple of more (e.g., ×2, ×5), or any higher value (e.g., ×20, ×100, ×5,000). Referring to the example of the figures, stage 2416 can optionally be performed by controller 2314 and / or processor 2304. Alternatively, an external system can determine the setting of the first FET or influence the setting of the FET via EO system 2300.

[0307] Stage 2420 of method 2400 includes receiving a third frame of information. The third frame of information includes a third frame detection level for each of the plurality of PSs of the PDA, the third frame detection level indicating an intensity of light detected by the corresponding PS in the third FET. It should be noted that the third frame (in which the detection data for the third frame of information is collected) can directly follow the second frame, but this is not required. The plurality of FETs of any one of the one or more intermediate frames (if any) between the second frame and the third frame can be equal to the second FET, the third FET, or any other FET (longer or shorter). Referring to the example of the accompanying drawings, stage 2420 can optionally be performed by processor 2304 (e.g., via readout circuit 2318).

[0308] Step 2420 includes identifying at least two types of PSs of the PDA from a plurality of PSs of the PDD based on the third FET:

[0309] a. An available PS group for the third frame (referred to as the "third group of usable PSs") includes the first PS and the second PS.

[0310] b. An unusable PS group for the third frame (referred to as "a third group of unusable PSs") includes the third PS and the fourth PS.

[0311] That is, since the FET of the third frame is longer than that of the first frame, the second PS is identified in stage 2404 as belonging to the first available PS group (i.e., the available PS group previously used for the first frame) and is identified in stage 2420 as belonging to the third unavailable PS group (i.e., the unavailable PS group previously used for the third frame). Since the FET of the third frame is longer than that of the second frame, the third PS is identified in stage 2412 as belonging to the second unavailable PS group (i.e., the unavailable PS group previously used for the second frame) and is identified in stage 2420 as belonging to the third available PS group (i.e., the available PS group previously used for the third frame).

[0312] The identification of stage 2420 can be implemented in various ways, such as any one or more of those discussed above with respect to stage 2404. For various reasons, such as, for example, as discussed above with respect to stage 2412, multiple PSs that were considered available for the shorter FET may be deemed unavailable for the longer FET in stage 2420. For various reasons, multiple PSs that were considered unavailable for the longer FET may be deemed available for the shorter FET in stage 2420. For example, if such multiple PSs have a charge storage capacity (e.g., capacitance) greater than the charge storage capacity of some PSs in the second group of unavailable PSs, the charge storage capacity of those different PSs may be deemed sufficient for the detection signal and the accumulated dark current within a shorter integration time than that of the second FET.

[0313] Stage 2420 is performed after stage 2416 (because it is based on the outputs of stage 2416). The timing of stage 2420 relative to the timing of stage 2416 can vary. For example, stage 2420 can optionally be performed before, simultaneously with, partially simultaneously with, or after stage 2416. Referring to the example figures, stage 2420 can optionally be performed by processor 2304 and / or controller 2314. Examples of methods for performing the identification of stage 2420 are discussed with respect to method 1100.

[0314] Stage 2422 includes disregarding the plurality of third frame detection levels of the third unusable PS group, and generating a third image based on the plurality of third frame detection levels of the third available PS group. Importantly, stage 2422 includes generating the third image while ignoring the plurality of outputs (detection levels) of at least one PS whose outputs were used in generating the first image (e.g., the second PS), while utilizing the plurality of outputs of at least one PS whose outputs were used in generating the second image (e.g., the third PS). Generating the third image can be accomplished using any suitable method, including any of the methods, techniques, and variations discussed above with respect to generating the first image. With respect to the third unusable PS group, it should be noted that since the detection data of these PSs is ignored in generating the third image, replacement values can be calculated using any suitable method (if desired). Following stage 2422, the third image can be provided to an external system (e.g., a screen monitor, a storage unit, a communication system, an image processing computer). After stage 2422, the third image may be processed using one or more image processing algorithms.After stage 2422, the third image may then be processed in other ways as desired.

[0315] Optionally, the generation of one or more images (e.g., the first image, the second image, the third image) in method 2400 can be based on a previous stage of evaluating dark current accumulation for at least one PS of the corresponding image, such as based at least on electrical measurements of the corresponding FET, the captured light signal, or a proximity light signal, or the like. For example, such measurements can include measuring dark current (or another indicative measurement) on a reference PS held in darkness. The generation of the corresponding image can include subtracting an amplitude related to the dark current evaluation of the PS from the detection signal of one or more PSs to provide a more accurate representation of the FOV of the PDA. Optionally, this stage of compensating dark current accumulation is performed only for the plurality of available PSs of the corresponding image.

[0316] In a PDA characterized by relatively high dark current (e.g., as a result of the types and characteristics of its multiple PDs), the capacitance of the various PSs where detection charge is collected may become saturated (partially or fully) due to the dark current, leaving little dynamic range for detecting ambient light (reaching from a field of view of the system). Even when means are implemented to subtract multiple dark current levels from the multiple detection signals (e.g., to normalize the detection data), the lack of dynamic range for detection means that the resulting signal is completely saturated or insufficient to meaningfully detect multiple ambient light levels. Since the dark current from the PDs is accumulated in the capacitance of the FET (whether the actual capacitors of the multiple PSs or parasitic capacitance or residual capacitance of other components), the method uses the FETs to determine which PSs are available to the corresponding FETs, leaving sufficient dynamic range in the capacitance after collecting the charge of the dark current (or at least a relevant portion thereof) for the entire FET. The identification of an unusable PS group for a frame may include, given the FET of the corresponding frame, identifying a plurality of PSs whose dynamic range is below an acceptable threshold (or otherwise expected to fail a dynamic range adequacy criterion). Similarly, the identification of an available PS group for a frame may include, given the FET of the corresponding frame, identifying a plurality of PSs whose dynamic range is above an acceptable threshold (or otherwise expected to meet a dynamic range adequacy criterion). The two acceptable thresholds may be the same threshold or different thresholds (e.g., if the dynamic ranges of the plurality of PSs are treated differently between those thresholds, such as being identified as being part of the available PS group for the associated frame).

[0317] Referring generally to method 2400, it should be noted that multiple additional instances of stages 2416, 2418, 2420, and 2422 can be repeated for multiple additional FETs (e.g., a fourth FET, and so on). Such times can be longer, shorter, or equal to any previously used FET. It should also be noted that, optionally, the first FET, the second FET, and the third FET are multiple consecutive FETs (i.e., the PDA does not use other FETs between the first FET and the third FET). Alternatively, other FETs can be used between the first FET and the third FET.

[0318] It should be noted that even if the exposure value (EV) remains the same, multiple different groups of usable PSs and unusable PSs can be determined for different FETs in method 2400. For example, consider a case where the first FET is expanded by a factor of q to provide the second FET, but the f-number is increased by a factor of q so that the total illumination received by the PDA is substantially the same. In such a case, even if the EV remains constant, the second unusable PS group will include PSs other than those included in the first unusable PS group because the dark current accumulation increases by a factor of p.

[0319] A non-transitory computer-readable medium is provided for generating image information based on data of a PDA, the non-transitory computer-readable medium including a plurality of instructions stored thereon, which, when executed on a processor, perform the following steps: receiving first frame information, the first frame information including a first frame detection level for each of a plurality of PSs of the PDA, the first frame detection level indicating a light intensity detected by the respective PS in a first FET; identifying, based on the first FET, from the plurality of PSs of the PDD: a first available PS group including a first PS, a second PS and a third PS, and a first unavailable PS group including a fourth PS; ignoring the plurality of first frame detection levels of the first unavailable PS group, generating a first image based on the first frame detection level of the first available PS group; after receiving the first frame information, determining a second FET, the FET being longer than the first FET; receiving second frame information, the second frame information including a second frame detection level for each of the plurality of PSs of the PDA, the second frame detection level indicating a light intensity detected by the respective PS in a second FET. light intensity; based on a second FET, identifying from the multiple PSs of the PDD: a second available PS group including the first PS, and a second unavailable PS group including the second PS, the third PS and the fourth PS; ignoring the multiple second frame detection levels of the second unavailable PS group, generating a second image based on the multiple second frame detection levels of the second available PS group; after receiving the second frame information, determining a third FET, the third FET being longer than the first FET and shorter than the second FET; receiving third frame information, the third frame information including a third frame detection level for each PS of the multiple PSs of the PDA, the third frame detection level indicating a light intensity detected by the respective PSs in a third FET; based on the third FET, identifying from the multiple PSs of the PDD: a third available PS group including the first PS and the second PS, and a third unavailable PS group including the third PS and the fourth PS; and ignoring the multiple third frame detection levels of the third unavailable PS group, generating a third image based on the multiple third frame detection levels of the third available PS group.

[0320] The non-transitory computer-readable medium of the previous paragraph may include additional instructions stored thereon that, when executed on a processor, perform any other steps or variations discussed above with respect to method 2400 .

[0321] Figure 252400 is a flow chart illustrating a method 2500 for generating a model for PDA operation in different FETs according to examples of the presently disclosed subject matter. Identifying which of the plurality of PSs belongs to a group of available PSs provided with a given FET (and possibly additional parameters such as temperature, bias voltage across the plurality of PDs, capacitance of the plurality of PSs, etc.) can be performed at different FETs based on a model of the behavior of each of the plurality of PSs. Such modeling can be part of method 2400 or can be performed separately and before it. Stages 2502, 2504, and 2506 of method 2500 are performed for each of the plurality of PSs of a plurality of PDAs (e.g., PDA 1602), and possibly for all of the PSs of the photodetector array.

[0322] Step 2502 includes determining the availability of the corresponding PS for each of a plurality of different FETs. The availability determination can be performed in various ways. For example, a detection signal from the PS can be compared to an expected value (e.g., if the illumination level is known, perhaps complete darkness, or a known higher illumination level), compared to an average value across the other PSs, compared to multiple detection levels across the other PSs (e.g., if all PSs are imaging a uniform color target), compared to multiple detection results across the other FETs (e.g., determining whether the detection level at duration T, e.g., 200 nanoseconds, is approximately twice the detection level at T / 2, e.g., 330 nanoseconds), and so forth. The determined availability can be a binary value (e.g., available or unavailable), a non-binary value (e.g., a scalar evaluating the availability level or indicating availability), a set of values (e.g., a vector), or any other suitable format. Optionally, the same plurality of frame FETs are used for all PSs in the plurality of PSs, but this is not required. For example: in a non-binary availability assessment, an intermediate value between completely unavailable and completely available may indicate that, at other available times (or partially available times), the detection signal of the corresponding PS should be combined or averaged with multiple detection signals of multiple adjacent PSs and / or with other readings of the same multiple PSs.

[0323] Method 2500 may include an optional stage 2504 of measuring the charge accumulation capacity and / or saturation parameter of the respective PSs. The charge capacity may be measured in any suitable manner, such as using power from the PD, from another power source in the PS (e.g., a current source), from another power source in the PDA, or from an external power source (e.g., a calibration machine in a manufacturing facility where photodetectors are manufactured). Stage 2504 may be omitted, for example, if the differences in capacitance between different PSs are negligible or simply ignored.

[0324] Stage 2506 includes creating a usability prediction model for the corresponding PS. The usability prediction model provides an estimate of the PS's usability when operating different FETs that are not included in the plurality of FETs whose usability was actively determined in stage 2502. The different FETs may be included in the same duration span as the plurality of FETs in stage 2502, either longer or shorter. The created usability prediction model can provide different types of usability indications, such as a binary value (e.g., usable or unusable), a non-binary value (e.g., a scalar value indicating usability or its indicative nature), a set of values (e.g., a vector), or any other suitable format. The type of usability indicated by the model can be the same type of usability determined in stage 2502 or a variation thereof. For example, stage 2502 may include evaluating the dark current collected in different FETs, while stage 2504 may include determining a time threshold indicating the maximum allowable FET for the PS to be considered usable. Optionally, the usability model may take into account the charge accumulation capacity of each PS.

[0325] Any suitable method may be used to create the availability prediction model. For example, different dark currents may be measured or estimated for the PD for different FETs, and then a regression analysis may be performed to determine a function (polynomial, exponential, etc.) that can be used to estimate the dark currents in other FETs.

[0326] Optional stage 2508 includes compiling an availability model for at least a portion of the PDA, including at least the plurality of PSs of the previous stage. For example, stage 2508 may include generating one or more matrices or other types of maps that store a plurality of model parameters for each of the PSs in its cells. For example, if stage 2506 includes creating a dark current linear regression function for each PS (p, s), the dark current linear regression function is given by DarkCurrent(p, s) = Ap , s·τ+Bp , s (where τ is the FET, and Ap , s and Bp , s is the linear coefficient of the linear regression) is provided, and then a matrix A can be generated to store multiple different Ap , s value, and a matrix B can be generated to store multiple different Bp , If necessary, a third matrix C can be used to store different capacitance values Cp for multiple different PSs. ,s(or different saturation values Sp , s).

[0327] Stage 2506 (or stage 2508, if implemented) may be followed by an optional stage 2510, which includes determining the availability of the plurality of PSs for a FET in the plurality of FETs not used in stage 2502 based on the results of stage 2506 (or stage 2508, if implemented). For example, stage 2510 may include creating a mask (e.g., a matrix) of unavailable PSs for a plurality of different PSs of the photodetector array.

[0328] Referring to method 2500 in its entirety, stage 2502 may include determining the dark current of each PS of the PDA at four different FETs (e.g., 33 ns, 330 ns, 600 ns, and 2000 ns). Stage 2504 may include determining a saturation value for each PS, and stage 2506 may include creating a polynomial regression of the dark current accumulation over time for each PS. Stage 2508 in this example may include generating a matrix, storing in each cell the FET for which the dark current (according to the regression analysis) would saturate the PS. Stage 2510 may include receiving a new FET and determining whether each cell of the matrix is below or above the stored value by generating a binary matrix that stores a first value (e.g., "0") for each unusable PS (where the FET is above the stored value) and a second value (e.g., "1") for each usable PS (where the FET is below the stored value).

[0329] Any stage of method 2500 may be performed during the manufacture of the PDA (e.g., during factory calibration), during operation of the system (e.g., after an EO system including the PDA is installed in its designated location, such as a vehicle, surveillance system, etc.), or at any other suitable time between or after these times. Different stages may be performed at different times.

[0330] With reference to method 2400 in its entirety, it is noted that it can be extended to measure the effects of dark current on multiple different PSs in multiple different FETs at different stages and with different operating conditions (e.g., when different PDs are subjected to different temperatures, when multiple different bias voltages are supplied to multiple PDs).

[0331] Optionally, determining a FET (e.g., the second FET, the third FET) as part of method 2400 may include maximizing the corresponding FET while maintaining a number of unavailable PSs for the corresponding frame below a predetermined threshold. For example, to maximize the collection of multiple signals, method 2400 may include setting a FET close to a threshold associated with a predetermined number of unavailable PSs (e.g., requiring at least 99% of the PDA's PSs to be available, while allowing up to 1% of the PSs to be unavailable). It should be noted that in some cases, the maximization may not yield the exact maximum duration, but a duration close to it (e.g., greater than 320% or greater than 325% of the mathematical maximum duration). For example, the maximum frame duration may be selected from a plurality of discrete predefined time spans.

[0332] For example, determining a FET as part of method 2400 may include determining a FET that is longer than other possible FETs, thereby resulting in more PSs than a previous FET, thereby causing a higher number of PSs to be deemed unusable compared to such other possible FETs, but improving image quality in the remaining PSs. This may be useful, for example, in relatively dark conditions. It is noted that, optionally, the determination of the FET (e.g., by attempting to maximize it) may take into account the spatial distribution of PSs deemed unusable across multiple different FETs. For example, knowing that in certain areas of the PDA, a cumulative plurality of PSs has a high percentage of PSs that will be deemed unusable on a certain FET may result in determining a FET below the threshold, especially if this is a significant portion of the FOV (e.g., at a center of the FOV, or at a location where a pedestrian or vehicle was identified in a previous frame).

[0333] Method 2400 may include creating a single image based on multiple detection levels from two or more frames detected at multiple different FETs, where multiple different groups of unavailable PSs are used for different FETs. For example, three FETs may be used: ×1, ×10, and ×100. A color determined for each pixel of the image may be determined based on the multiple detection levels of one or more PSs (e.g., FETs where the PS is available, not saturated, and detects a non-negligible signal) or the multiple detection levels of multiple adjacent PSs (e.g., if no usable detection signal is provided even if the corresponding PS is determined to be available, such as because the signal is negligible in such a case). Method 2400 may include determining multiple FETs to be used to combine different exposures for a single image (e.g., using high dynamic range imaging (HDR)). The determination of such FETs may be based on modeling of different PS availability in multiple different FETs, such as the model generated in method 2500. Method 2400 may further include deciding to capture a single image in two or more different detection instances (wherein the plurality of detection signals are read separately in each instance and then summed), each detection instance providing sufficient available PS. For example, instead of capturing a scene once using a 2-ms FET, method 2400 may include deciding to capture the scene twice (e.g., two 1-ms FETs, a 1.5-ms FET, and a 0.5-ms FET) such that the number of available PS in each exposure exceeds a predetermined threshold.

[0334] Optionally, method 2400 may include determining at least one FET based on an availability model of different PSs in different FETs (e.g., generated in method 2500) and saturation data from at least one previous frame captured by the PDA. The saturation data includes information about PSs that were saturated in at least one FET in at least one previous frame (e.g., the number of PSs, which PSs, and which parts of the PDA) and / or information about PSs that were nearly saturated in at least one FET in at least one previous frame. The saturation data may relate to the immediately preceding frame (or frames) so that it indicates saturation behavior of a curtain imaged scene.

[0335] Method 2400 may further include modeling the availability of multiple PSs of the PDA at multiple different FETs (e.g., by implementing method 2500 or any other suitable modeling method). Providing an availability model of multiple PSs of the PDA at multiple different FETs (either as part of method 2400 or not as part of method 2400) may include: (a) determining at least one of the second FET and the third FET based on the results of the modeling; and / or (b) identifying at least one of the multiple unavailable PS groups based on the results of the modeling.

[0336] Optionally, when determining any one or more FETs, method 2400 may include determining a FET that balances extending the FET due to darkness in the FOV scene with reducing the FET to limit the number of unusable PSs that become available, which increases with longer FETs (e.g., based on the model of method 2500). For example, at the same temperature and bias across the PD (such that the dark current in each FET remains constant), stage 2408 may include determining a longer FET as the scene becomes darker (at the expense of a larger number of unusable PSs), and stage 2416 may include determining a shorter FET as the scene becomes brighter (thereby reducing the number of unusable PSs). This is particularly important in darker images, where the availability of multiple PSs due to dark current accumulation (which is caused by temperature and operating conditions rather than illumination levels) limits the lengthening of the FETs, which may be done if dark current accumulation does not significantly limit the dynamic range of the individual PSs. In another example, over a time span during which the scene illumination remains constant, stage 2408 may include determining a longer FET to be enabled as the temperature drops (thereby reducing dark current and reducing the percentage of unavailable PS on each FET), while stage 2416 may include determining a shorter FET as the temperature of the PDA rises again.

[0337] Figure 26 is a graphical representation of an execution of method 2400 for three frames of the same scene captured in different FETs according to examples of the presently disclosed subject matter. The example scene includes four concentric rectangles, each darker than the surrounding rectangles. Figure 26 The various figures correspond to a stage of method 2400 and are numbered with an equivalent reference numeral followed by a prime. For example, figure 2406′ matches an execution of stage 2406, and so on. Each rectangle in the lower nine figures represents a single PS, or a pixel that directly maps to such a PS (in the lower three figures). The positions of the multiple PSs relative to the PDD remain unchanged in all figures.

[0338] As is common in many types of PDAs, the PDA from which frame information is received may include a number of PSs that are bad, defective, or otherwise misbehaving (also referred to as bad, defective, or otherwise misbehaving pixels). The term "misbehaving PS" broadly relates to a PS that deviates from its expected response, including but not limited to: stuck, dead, hot, lit, warm, defective, and flashing PSs. The misbehaving PSs may be a single PS or a cluster of multiple PSs. Non-limiting examples of defects that may cause a PS to behave abnormally include: PS bump bond connectivity, addressing faults in the multiplexer, vignetting, severe sensitivity deficiency of some PSs, non-linearity, poor signal linearity, low full well, poor mean-variance linearity, excessive noise, and high dark current. One or more PSs identified as an unusable PS in method 2400 may be a permanently faulty PS or a PS that behaves abnormally based on conditions unrelated to the FET (e.g., due to high temperature). Such PSs may be identified as all FETs (e.g., PS 8012.5) that are unusable in method 2400. However, it should be noted that due to limited functionality and sufficiently long FETs (e.g., PS 8012.4), some functional PSs (not "misbehaving") may be deemed unavailable in all FETs of method 2400. Alternatively, method 2400 may include determining the availability of one or more PSs of the PDA based on other parameters besides the FETs (e.g., temperature, various electrical parameters, ambient light level). It should be noted that in such a case, a PS that is rendered unavailable due to FETs due to other considerations (e.g., temperature) cannot generally be deemed available due to its capacitance limitations.

[0339] In the example shown:

[0340] a. It is possible that under all conditions, the PS 8012.5 has no output signal, regardless of the amount of light striking it in all three FETs (T1, T2, T3).

[0341] b. It is possible that under all conditions, the PS 8012.4 outputs a saturated signal, regardless of the amount of light striking it in all three FETs (T1, T2, T3).

[0342] c. PS 8012.3 outputs a usable signal at the shortest FET (T1), but outputs an unusable (saturated) signal at the longer FETs (T2 and T3).

[0343] d. PS 8012.2 outputs a usable signal at the shorter FETs (T1 and T3), but an unusable (saturated) signal at the longest FET (T2).

[0344] It should be noted that other types of defects and erroneous outputs may also occur. For example, such errors may include: outputting a highly non-linear signal response, consistently outputting a signal that is too strong, consistently outputting a signal that is too weekly, outputting a random or semi-random output, and the like. Similarly, many PSs (such as the first PS 8012.1) can be used for all FETs used in the test.

[0345] Back to Figure 23 It should be noted that, alternatively, system 2300 may be an EO system with dynamic PS availability assessment capabilities. That is, EO system 2300 may be capable of alternately assigning multiple PSs as available or unavailable based on the FET and possibly other operating parameters, and utilizing multiple detection signals of multiple PSs only when it is determined at acquisition time that the respective PS is available (e.g., according to an availability model).

[0346] In such a case, the EO system 2300 includes:

[0347] a. PDA 2302, which includes multiple PSs 2306, each of which is operable to output multiple detection signals in different frames. The detection signal output by the corresponding PS 2306 for a frame indicates the amount of light impinging on the corresponding PS in the corresponding frame (and may also indicate the dark current of the PD of the corresponding PS).

[0348] b. An availability filtering module (eg, implemented as part of the processor 2304 or separately). The availability filtering module is operable to filter the availability of each PS based on a first FET.

[0349] In one embodiment, a PS 2306 may be determined to be unusable (which may vary between different PSs 2306), and the same PS 2306 may be determined to be unusable based on a second FET that is shorter than the first FET. That is, PSs 2306 that were unusable at one point (and whose outputs were ignored in generating one or more images) may later become available again (e.g., if the FETs become short), and the outputs of these PSs 2306 may be useful again in generating subsequent images.

[0350] c. The processor 2304 is operable to generate a plurality of images based on the plurality of frame detection levels of the plurality of PSs 2306. In other configurations of the processor 2304, it is configured to: (a) exclude a first detection signal of a filtered PS determined by the availability filtering module to be unusable for the first image when generating a first image based on the plurality of first frame detection levels, and (b) include a second detection signal of the filtered PS determined by the availability filtering module to be usable for the second image when generating a second image based on the plurality of second frame detection levels captured by the PDA after capturing the plurality of first frame detection levels.

[0351] Optionally, the controller 2314 may determine different FETs for different frames based on different illumination levels of multiple objects in the field of view of the EO system.

[0352] Alternatively, controller 2314 may be configured to determine the number of FETs for the EO system by maximizing the number of FETs while keeping the number of unavailable PSs for each frame below a predetermined threshold (eg, as discussed with respect to method 2400).

[0353] Optionally, the EO system 2300 may include: at least one shielded PD that is shielded from ambient lighting (e.g., by a physical barrier or using deflecting optics); and dedicated circuitry operable to output an electrical parameter indicating the level of dark current based on the signal level of the at least one shielded PD. The processor 2304 may be configured to generate multiple images based on the electrical parameter, the corresponding FET, and the multiple detection signals of the PDA, thereby compensating for different levels of dark current accumulation in different frames.

[0354] Optionally, the processor 2304 may be configured to calculate a replacement value for at least one pixel of the first image associated with the filtered PS based on a detection level of the filtered PS measured when the PS is identified as available. Optionally, the processor 2304 may be configured to calculate a plurality of replacement values for a plurality of PSs based on the detection levels of a plurality of adjacent PSs when the detection signals of the respective PSs are excluded from the generation of the plurality of images. Optionally, the processor 2304 may be configured to calculate a replacement value for at least one pixel of the first image associated with the filtered PS based on a first frame detection level of a plurality of adjacent PSs.

[0355] Optionally, the processor 2304 (or the availability filter module, if not part of the processor) can be operated to determine a degree of availability for multiple PSs based on a FET, the degree including a sum of the durations during which the sampled multiple PSs of the PDD are sensitive to light and excluding multiple intermediate times between multiple durations during which the sampled multiple PSs are not sensitive to light.

[0356] Optionally, processor 2304 can utilize an availability model generated according to method 2500 to determine when to include and when to exclude multiple detection signals of different PSs captured at different FETs. Optionally, EO system 2300 can be operated to perform method 2500. Optionally, EO system 2300 can be configured to participate in the performance of method 2500 in conjunction with an external system (e.g., a factory calibrator used in the manufacture of EO system 2300).

[0357] Figure 2735 is a flow chart illustrating an example of a method 3500 according to the presently disclosed subject matter. Method 3500 is used to generate multiple images based on different subsets of multiple PSs under different operating conditions. Referring to the examples described with respect to the previous figures, method 3500 can be performed by processor 1604, wherein the PDA of method 3500 can optionally be PDA 1602. Method 3500 includes at least a plurality of stages 3510, 3520, 3530, and 3540, which are repeated as a sequence for different frames captured by a photodetector array. The sequence can be performed in its entirety for each frame in a stream, but need not be, as discussed in more detail below.

[0358] The sequence begins at stage 3510, which receives frame information from the PDA, the frame information indicating multiple detection signals for the frame provided by multiple PSs of the PDA. The frame information may include: the detection level (or multiple levels) of each PS (e.g., between 0 and 1024, three RGB values, each between 0 and 255, or the like), or any other format. The frame information may indicate multiple detection signals in an indirect manner (e.g., relative to the level of an adjacent PS or relative to the level of the same PS in a previous frame to provide information about the detection level of a given PS). The frame information may also include: additional information (e.g., sequence number, time stamp, operating conditions), some of which may be used in subsequent steps of method 3500. The frame information received from the PDA may include: bad, defective or otherwise misbehaving PSs.

[0359] Stage 3520 includes receiving operating condition data during the frame duration, the operating condition data indicating a plurality of operating conditions of the PDA. The plurality of operating conditions may be received from different types of entities, such as any one or more of the following entities: the PDA, a controller of the PDA, the at least one processor executing method 3500, one or more sensors, one or more controllers of at least one processor executing method 3500, and the like. Non-limiting examples of the plurality of operating conditions that may be mentioned in stage 3520 include FETs of the PDA (e.g., electronic or mechanical shutter, flash illumination duration, and the like), amplification gain of the PDA or connected circuitry, bias voltages supplied to a plurality of PDs of the PDA, ambient light levels, dedicated illumination levels, image processing modes of downstream image processors, filtering applied to the light (e.g., spectral filtering, polarization), and the like.

[0360] Stage 3530 includes determining, based on the operating condition data, a group of defective pixels that includes at least one of the plurality of pixels and excludes a plurality of other pixels. When stage 3530 is performed for different frames in different corresponding instances of stage 3520 based on different operating condition data received for those frames, different groups of defective pixels are selected for different frames having different operating conditions. However, the same group of defective pixels may be selected for two frames having different operating conditions (e.g., when the difference in the operating conditions is relatively small).

[0361] It should be noted that the decision is based on the operating condition data, not on an assessment of the plurality of PSs themselves. Thus, the defectivity of the various PSs included in the different groups is an estimate of their condition, not a statement of their actual operability condition. Thus, a PS included in the defective PS group in stage 3530 is not necessarily defective or inoperable under the plurality of operating conditions indicated in the operating condition data. The decision in stage 3530 is intended to match the actual state of the PDA as accurately as possible.

[0362] Step 3540 includes processing the frame information to provide an image representing the frame. The processing is based on multiple detection signals from multiple PSs of the photodetector, but does not include multiple PSs in the defective PS group. That is, the multiple detection signals from the multiple PSs of the PDA are used to generate an image representing the field of view (or other scene, or one or more objects whose light reaches the PDA), but avoid all detection signals originating from multiple PSs, which are included in the defective PS group (as previously described, it is dynamically determined based on the operating condition data in the captured relevant frame information). Stage 3540 may optionally include calculating multiple replacement values to compensate for multiple ignored detection signals. Such calculations may include, for example, determining a replacement value for a defective PS based on multiple detection signals from multiple adjacent PSs. Such calculations may include, for example, determining a replacement value for a pixel of the image based on the multiple values of multiple adjacent pixels of the image. Any of the techniques discussed above with respect to image generation in method 2400 may also be used for image generation in stage 3540.

[0363] An example of performing the method for two frames (a first frame and a second frame) may include, for example:

[0364] a. Receive first frame information from the PDA indicating a plurality of first detection signals provided by a plurality of PSs and associated with a first frame duration, the plurality of PSs including at least a first PS, a second PS, and a third PS. A frame duration is the time it takes for the PDA to aggregate light into a single image or a frame of a video. Different frame durations may be mutually exclusive, but in some embodiments may optionally be partially overlapping.

[0365] b. Receiving first operating condition data, the first operating condition data indicating an operating condition of the PDA during the first frame duration.

[0366] c. Determining a first defective PS group based on at least the first operating condition data, including the third PS but excluding the first PS and the second PS. The determination may include directly determining the first defective PS group or determining other data that indicates which pixels are considered defective (e.g., determining a complement of non-defective pixels, assigning a defect level to each pixel, and then setting a threshold or other determination criteria).

[0367] d. Processing the first frame information based on the first defect PS group to provide a first image, so that the processing is based on at least the multiple first detection signals of the first PS and the second PS (optionally, after previous preprocessing, such as digitization, setting an upper limit, level adjustment, etc.), and ignoring information related to the multiple detection signals of the third PS.

[0368] e. Receive second frame information from the PDA, the second frame information indicating a plurality of second detection signals provided by a plurality of detection PSs, and the second frame information being related to a second frame duration other than the first frame duration.

[0369] F. receive the second operating condition data, wherein the second operating condition data indicate a plurality of operating conditions of the PDA during the second frame duration, and the second operating condition data are different from the first operating condition data. It should be noted that the second operating condition data can be received from the source identical with receiving the first operating condition data, but this is not necessary.

[0370] g. Based on the plurality of second operating conditions, determining data for a second defective PS group, including the second PS and the third PS, but excluding the first PS. The determining may include directly determining the second defective PS group, or determining other data that indicates which pixels are considered defective (e.g., determining a complement of non-defective pixels, assigning a defect level to each pixel, and then setting a threshold or other determination criteria).

[0371] h. Processing the second frame information based on the second defect PS group to provide a second image, so that the processing of the second image information is based at least on the multiple second detection signals of the first PS, and ignoring information related to the multiple detection signals of the second PS and the third PS.

[0372] Figure 28A Schematic diagram illustrating a system 3600 and a plurality of exemplary target objects 3902 and 3904 according to various examples of the presently disclosed subject matter. EO system 3600 includes at least a processor 3620 operable to process a plurality of detection signals from at least one PDA (which may be part of the same system, but not necessarily so) to generate a plurality of images representing a plurality of objects in a field of view of system 3600. System 3600 may be implemented by system 2300 and similar reference numerals may be used (e.g., in such a case, PDA 3610 may be PDA 2302, controller 3640 may be controller 2314, and so on), but this is not required. For the sake of brevity, not all of the description provided above with respect to system 2300 is repeated, and it should be noted that any combination of one or more components of system 2300 may be implemented similarly in system 3600, and vice versa. System 3600 can be a processing system (e.g., a computer, a graphics processing unit) or an EO system that further includes a PDA 3610 and optical components. In the latter case, system 3600 can be any type of EO system that uses a PDA for detection, such as a camera, a spectrometer, a LIDAR, and the like. Optionally, system 3600 can include one or more illumination sources 3650 (e.g., lasers, LEDs) for illuminating multiple objects within the FOV (e.g., illuminating the objects for at least the first and second FETs). Optionally, system 3600 can include a controller 3640 that can determine different FETs for different frames based on the different illumination levels of multiple objects within the EO system's field of view. Optionally, those different FETs can include the first FET and / or the second FET.

[0373] exist Figure 28A Two exemplary targets are shown in FIG36: a dark car 3902 (with low reflectivity body panels) with a highly reflective sign, and a black rectangular panel 3904 with a white patch on it. It should be noted that system 3600 is not necessarily limited to generating multiple images of multiple low reflectivity objects with multiple high reflectivity patches. However, the manner in which system 3600 generates multiple images of such targets is interesting.

[0374] The processor 3620 is configured to receive a plurality of detection results of an object from a PDA (e.g., PDA 3610, if implemented), the object including a high-reflectivity surface surrounded on all sides by a plurality of low-reflectivity surfaces (taking multiple targets 3902 and 3904 as an example). The plurality of detection results include: (a) a first frame of information of the object detected by the PDA in a first FET, and (b) a second frame of information of the object detected by the PDA in a second FET that is longer than the first FET. The first frame of information and the second frame of information indicate a plurality of detection signals output by different PSs of the PDA, which in turn indicate a plurality of light intensities of different portions of the target detected by the PDA. Some PSs detect light from the low-reflectivity portions of the multiple objects, while at least another PS detects light from the high-reflectivity surfaces.

[0375] Based on different FETs, the processor 3620 processes the first frame information and the second frame information in different ways. Figure 28B 3902 and 3904 according to various examples of the presently disclosed subject matter. When processing the first frame of information, the processor 3620 processes the first frame of information based on the first FET. It generates a first image comprising a bright area representing the high reflectivity surface surrounded by a dark background representing the low reflectivity surface. This is Figure 28B is illustrated as a plurality of first images 3912 and 3914 (corresponding to Figure 28A When the processor 3620 processes the second frame information longer than the first FET based on the second FET, a second image is generated, which includes a dark background without a bright area. Figure 28B Illustrated as a plurality of second images 3922 and 3924 (corresponding to Figure 28A Multiple objects 3902 and 3904).

[0376] That is, even if more light from highly reflective surfaces reaches each photodetector PS in the second frame, the image output will not be brighter or more saturated, but rather darker. Processor 3620 can use information from neighboring PSs to determine a darker color for the pixels representing the high-reflectivity surfaces in the second image (having lower-intensity signals due to capturing the object's lower-reflectivity surfaces) because it determines that the signals from the associated PSs are not available in the longer second FET. Optionally, processor 3620 can be configured to discard detected light signals corresponding to high-reflectivity surfaces when generating the second image based on the second FET (and optionally also based on modeling the availability of individual PSs, such as discussed with respect to method 2500), and to calculate a dark color for at least one corresponding pixel in the second image in response to the detected light intensities from the adjacent low-reflectivity surfaces of the object captured from the adjacent PSs. Optionally, processor 3620 determines to discard the corresponding PS based not on the detected signal level, but rather on the sensitivity of the corresponding PS to dark current (e.g., finite capacitance). Optionally, when processing the second frame information, processor 3620 may identify at least one PS that detects light from the high reflectivity surface as unavailable for the second frame based on the second FET, for example similar to the multiple identification stages of method 2400.

[0377] It should be noted that the high reflectivity surface can be smaller than the low reflectivity surface and can be surrounded by the low reflectivity surface on all sides, but this is not required. The size (such as angular size) of the high reflectivity surface can correspond to a single PS, less than one PS, but can also correspond to several PS. The difference between the high reflectivity level and the low reflectivity level can vary. For example: the reflectivity of the low reflectivity surface can be between 0% and 15%, while the reflectivity of the high reflectivity surface can be between 80% and 100%. In another example, the low reflectivity surface can have a reflectivity between 50% and 55%, while the high reflectivity surface can have a reflectivity between 65% and 70%. For example: the minimum reflectivity of the high reflectivity surface can be ×2, ×3, ×5, ×10 or ×100 of the maximum reflectivity of the low reflectivity surface. Optionally, the high-reflectivity surface has a reflectivity greater than 95% within the spectral range detectable by the plurality of PSs (e.g., a white surface), while the low-reflectivity surface has a reflectivity less than 5% within the spectral range detectable by the plurality of PSs (e.g., a black surface). It should be noted that, as described above, a FET can correspond to a fragmented time span (e.g., corresponding to several illumination pulses) or a single continuous time span.

[0378] It should be noted that, optionally, the amount of multiple light signal levels reaching the associated PS from the high reflectivity surface in the first FET and in the second FET can be similar. This can be achieved by filtering the incoming light and changing the f-number of the detection optics 3670 accordingly (e.g., increasing the FET by a factor of q and increasing the f-number by a factor of q). Optionally, a first exposure value (EV) of the PDA in capturing the first frame of information differs from the second EV of the PDA in capturing the second frame of information by less than 1%. Optionally, the difference in FET is the only major difference between the operating conditions between the first frame and the second frame.

[0379] The temperature of the PDA is evaluated as discussed above to calibrate the availability model to different levels of dark current. Optionally, the processor 3620 can be further configured to: (a) process the detection signal reflected from the object to determine a first temperature estimate of the photodetector array in capturing the first frame of information, and to determine a second temperature estimate of the photodetector array in capturing the first frame of information, and (b) determine to discard a plurality of detection results corresponding to the high reflectivity surface based on the second FET and the second temperature estimate.

[0380] Figure 29 3700 for generating image information based on data from a PDA, according to various examples of the presently disclosed subject matter. Referring to the examples described with respect to the previous figures, it should be noted that method 3700 can optionally be performed by system 3600. Any of the variations discussed above with respect to system 3600 can be applied mutatis mutandis to method 3700. In particular, method 3700 (and at least a plurality of its stages 3710, 3720, 3730, and 3740) can be performed by processor 3620.

[0381] Stage 3710 includes receiving a first frame of information from the PDA comprising a black target including a white area, the first frame indicating the light intensity of different portions of the target as detected by the PDA in a first FET. It should be noted that the white area can be replaced by a bright area (or other highly reflective area). For example, any area with a reflectivity greater than 50% can be used instead. It should be noted that the black target can be replaced by a dark area (or other slightly reflective area). For example, any target with a reflectivity less than 10% can be used instead.

[0382] Stage 3720 includes processing the first frame information based on the first FET to provide a first image, the first image including a bright area surrounded by a dark background. Optionally, stage 3720 may be implemented using any of the image generation processes discussed above with respect to any of stages 2406, 2414, and 2422 of method 2400.

[0383] Stage 3730 includes receiving a second frame of information from the PDA of a black target including white areas, the second frame of information indicating multiple light intensities of different portions of the target detected by the PDA in a second FET that is longer than the first FET.

[0384] Step 3740 includes processing the second frame information based on the second FET to provide a second image, the second image including a dark background without a bright area. Optionally, stage 3740 can be implemented using any of the image generation processes discussed above with respect to any of steps 2406, 2414, and 2422 of method 2400 and the previous stage of identifying a plurality of available and unavailable PS groups.

[0385] Regarding the execution order of method 3700, stage 3720 is executed after stage 3710, and stage 3740 is executed after stage 3730. Any suitable stage order may be used. Method 3700 may also optionally include capturing the first frame information and / or the second frame information via a PDA.

[0386] Optionally, after receiving the first frame of information, the second FET may be determined before receiving the second frame of information, the second FET being longer than the first FET. Optionally, the processing of the second frame of information may include: discarding the light intensity information of the detected white area based on the second FET; and determining a dark color of at least one corresponding pixel of the second image in response to the plurality of light intensities of the plurality of adjacent areas detected by the second frame of information. Optionally, the processing of the second frame of information may include: identifying at least one PS based on the second FET, the at least one PS detecting light from the white area as unavailable for the second frame. Optionally, a first exposure value (EV) of the PDA in capturing the first frame of information may differ by less than 1% from a second EV of the PDA in capturing the second frame of information.

[0387] Alternatively, during the first frame exposure time, dark current accumulation on the PS associated with the low reflectivity data leaves a usable dynamic range for the PS, while during the second frame exposure time, dark current accumulation on that PS leaves an insufficient dynamic range for the PS. In such a case, the PS corresponding to the high reflectivity region cannot be used for image generation in the second image, and a replacement color value can be calculated to replace the lost detection level.

[0388] A non-transitory computer-readable medium is provided for generating image information based on data of a PDA (including multiple instructions stored thereon), wherein when the image information is executed on a processor, the following steps are performed: (a) receiving a first frame information of a black target from a PDA, the black target including a white area, the first frame information indicating the light intensity of different parts of the target detected by the PDA in a first FET; (b) processing the first frame information based on the first FET to provide a first image, the first image including a bright area surrounded by a dark background; (c) receiving a second frame information of the black target from the PDA, the black target including the white area, the second frame information indicating the light intensity of different parts of the target detected by the PDA in a second FET longer than the first FET; (d) processing the second frame information based on the second FET to provide a second image, the second image including a dark background without a bright area.

[0389] The non-transitory computer-readable medium of the previous paragraph may include: other instructions stored thereon, and when the multiple instructions are executed on a processor, any other steps or variations discussed above with respect to method 3700 are performed.

[0390] In the above disclosure, a plurality of systems, methods, and computer code products are described, as well as ways of utilizing them to photoelectrically capture and generate high quality images. In particular, such systems, methods, and computer code products can be utilized to generate a plurality of high quality SWIR images (or other SWIR sensing data) in the presence of high PD dark current. Such a plurality of PDs can be a plurality of germanium PDs, but this is not the case in all cases. Some ways of using such systems, methods, and computer program products in a collaborative manner are discussed above, and many other ways are possible and are considered part of the innovative subject matter of the present disclosure. Any of the systems discussed above can incorporate any one or more components of any one or more of the other systems discussed above to achieve higher quality results, to achieve similar results in a more efficient or cost-effective manner, or for any other reason. Similarly, any of the methods discussed above can incorporate any one or more stages of any one or more of the other methods discussed above to achieve higher quality results, to achieve similar results in a more efficient or cost-effective manner, or for any other reason.

[0391] In the following paragraphs, some non-limiting examples of such combinations are provided to demonstrate some possible synergistic effects.

[0392] For example, imaging systems 100, 100', and 100" having integration times short enough to overcome the undue impact of dark current noise may implement multiple PDDs, such as multiple PDDs 1300, 1300', 1600, 1600', 1700, 1800 included in receiver 110 to reduce the time-invariant (direct current, DC) portion of the dark noise. In this way, the capacitance of the multiple PSs is not overwhelmed by the time-invariant portion of the dark current that is not accumulated in the detection signal, and the noise of the dark current does not cloud the detection signal. Implementing any one of the multiple PDDs 1300, 1300', 1600, 1600', 1700, 1800 in any one of the multiple imaging systems 100, 100', and 100" may be used to extend the frame exposure time to a significant extent (because the DC portion of the dark current is not accumulated in the capacitance) while still detecting a meaningful signal.

[0393] For example, imaging systems 100, 100', and 100" in which the integration time is set short enough to overcome the excessive effects of dark current noise can implement any one or more of methods 2400, 2500, and 3500 to determine the number of PSs available at that frame exposure time, and possibly reduce the frame exposure time (which corresponds to the integration time) to further determine that a sufficient number of PSs are available. Similarly, the expected ratio between the read noise and the expected cumulative dark current noise level of a given FET and the expected availability of different PSs in such a PS can be used by the controller to set a balance between the quality of the detected signal, the number of available pixels, and the illumination level required by the light source (e.g., laser 600). When applicable, the availability model at different FETs can also be used to determine the distance range of the multiple gated images generated by imaging systems 100, 100', and 100". Further incorporating any of the plurality of PDDs 1300, 1300', 1600, 1600', 1700, 1800 into the sensor as such an imaging system would increase the benefits discussed in the preceding paragraph.

[0394] For example, any one or more of methods 2400, 2500, and 3500 can be implemented by system 1900 (or by any EO system including any of the plurality of PDDs 1300, 1300', 1600, 1600', 1700, 1800). The reduction in the effects of dark current accumulation discussed with respect to system 1900 (or any of the aforementioned PDDs) allows for the use of longer FETs. Implementing any of these methods can be used to facilitate longer FETs because determining which PSs are temporarily unavailable in a relatively long FET enables system 1900 (or another EO system including one of the aforementioned PDDs) to ignore these PSs and optionally replace their detection output with data from multiple adjacent PSs.

[0395] Certain stages of the aforementioned method may also be implemented in a computer program running on a computer system, the computer program comprising at least code portions for executing the steps of the method when executed on a programmable device such as a computer system or when a programmable device is activated, thereby performing the functions of an apparatus or system according to the present disclosure. Such a method may also be implemented in a computer program running on a computer system, the computer program comprising at least code portions for causing a computer to execute the steps of a method according to the present disclosure.

[0396] A computer program is a list of instructions, such as a specific application and / or an operating system. The computer program may include, for example, one or more of the following: a subroutine, a function, a procedure, a method, an implementation, an executable application, an applet, a servlet, a source code, a code, a shared library / dynamically loaded library, and / or other instruction sequences designed to be executed on a computer system.

[0397] The computer program may be stored internally on a non-transitory computer-readable medium. All or some of the computer program may be provided on a computer-readable medium that is permanently, removably, or remotely coupled to an information processing system. The computer-readable medium may include, for example, but not limited to, any number of the following: magnetic storage media, including magnetic disk and tape storage media; optical storage media, such as optical disk media (e.g., CD-ROM, CD-R, etc.) and digital video disk storage media; non-volatile storage media, including semiconductor-based storage units such as flash memory, EEPROM, EPROM, ROM; ferromagnetic digital memory; MRAM; volatile storage media, including registers, buffers, or caches, main memory, RAM, etc.

[0398] A computer process typically consists of an executing (running) program or a portion of a program, current program values and state information, and information used by the operating system to manage the execution of the process. An operating system (OS) is software that manages the sharing of a computer's resources and provides an interface for programmers to access these resources. An operating system processes system data and user input and responds as a service to the system's users and programs by allocating and managing tasks and internal system resources.

[0399] The computer system may, for example, include at least one processing unit, associated memory, and a plurality of input / output (I / O) devices. When the computer program is executed, the computer system processes information according to the computer program and generates resultant output information via a plurality of I / O devices.

[0400] The many connections discussed in this article can be any type of connection suitable for transmitting signals from or to various nodes, units or devices via many intermediate devices. Therefore, unless otherwise implied or specified, the many connections can be, for example, direct connections or indirect connections. The many connections can be illustrated or described with reference to a single connection, multiple connections, unidirectional connections or bidirectional connections. However, different embodiments can change the implementation schemes of the many connections. For example: a separate unidirectional connection can be used instead of a bidirectional connection, or vice versa. Moreover, multiple connections can be replaced by a single connection, which transmits multiple signals serially or in a time-multiplexed manner. Similarly, many single connections carrying multiple signals can be separated into various different connections carrying subsets of these signals. Therefore, there are many options for transmitting signals.

[0401] Alternatively, the illustrated examples may be implemented as circuits on a single integrated circuit or within the same device. Alternatively, the examples may be implemented as any number of separate integrated circuits or separate devices interconnected in a suitable manner. Alternatively, appropriate portions of the methods may be implemented as soft or code representations of physical circuits or logical representations convertible to physical circuits, such as in any suitable type of hardware description language.

[0402] Other modifications, variations and substitutions are also possible. Therefore, the description and drawings should be regarded as illustrative rather than restrictive. Although certain features of the present disclosure have been illustrated and described herein, many modifications, substitutions, changes and equivalents will now occur to those of ordinary skill in the art. Therefore, it is to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the present disclosure. It will be understood that the above-described embodiments are cited as examples only, and that their various features and combinations of these features may be changed and modified. Although various embodiments have been shown and described, it should be understood that it is not intended to limit the present disclosure by such disclosure, but rather is intended to cover all modifications and alternative constructions that fall within the scope of the present disclosure, as defined in the appended claims.

[0403] In the claims or description of the present application, unless otherwise indicated, adjectives such as "substantially" and "about" modifying a condition or relational characteristic of one or more features of an embodiment are understood to mean that the condition or characteristic is defined to be within an acceptable tolerance range for the operation of the embodiment for an intended application. It should be understood that where a claim or description refers to "a" or "an" element, such reference should not be construed as meaning that only one of the elements is present.

[0404] All patent applications, white papers, and other publicly available materials published by the assignee of the present disclosure and / or TriEye LTD. of Tel Aviv, Israel, are incorporated herein by reference in their entirety. No admission is made that any reference cited herein is prior art.

Claims

1. An electro-optical system capable of dynamic photosensitive site availability assessment, characterized by: include: a photodetector array comprising a plurality of photosensitive sites, each photosensitive site being operable to output a plurality of detection signals in a plurality of different frames, the detection signal output by the corresponding photosensitive site for a frame indicating an amount of light impinging on the corresponding photosensitive site during a corresponding frame exposure time; an availability filtering module being operable to first determine, for each of the plurality of photosensitive sites, the photosensitive site as unavailable based on a first frame exposure time, and later determine the photosensitive site as available based on a second frame exposure time, the second frame exposure time being shorter than the first frame exposure time; and a processor operable to generate a plurality of images based on a plurality of frame detection levels of the plurality of photosensitive sites, wherein the processor is configured to: When generating a first image based on a plurality of first frame detection levels, excluding a first detection signal of a filtered photosensitive site determined by the availability filtering module to be unavailable for the first image, and When a second image is generated based on multiple second frame detection levels captured by the photodetector array after capturing the multiple first frame detection levels, a second detection signal of the filtered photosensitive sites determined by the availability filtering module to be available for the second image is included.

2. The electro-optical system according to claim 1, wherein: The electro-optical system includes a controller configured to determine a plurality of different frame exposure times for a plurality of different frames based on a plurality of different illumination levels of a plurality of objects in a field of view of the electro-optical system.

3. The electro-optical system according to claim 2, wherein: The controller is configured to determine the multiple frame exposure times of the electro-optical system by maximizing the multiple frame exposure times while maintaining a number of unusable photosensitivity sites for the multiple frames below a predetermined threshold.

4. The electro-optical system according to claim 1, wherein: The electro-optical system includes: at least one shielded photodiode, which is shielded from ambient lighting; and a circuit that outputs an electrical parameter indicating a dark current level based on a signal level of the at least one shielded photodiode, wherein the processor is configured to generate multiple images based on the electrical parameter, based on the corresponding frame exposure time and based on the multiple detection signals of the photodetector array, thereby compensating for multiple different degrees of dark current accumulation in multiple different frames.

5. The electro-optical system according to claim 4, wherein: The electro-optical system includes: a controller for determining multiple different frame exposure times for multiple different frames based on multiple different illumination levels of multiple objects in a field of view of the electro-optical system, wherein the controller is configured to determine the multiple frame exposure times of the electro-optical system by maximizing the multiple frame exposure times while keeping a number of multiple unavailable photosensitivity sites for the multiple corresponding frames below a predetermined threshold.

6. The electro-optical system according to claim 1, wherein: The processor is operable to calculate a replacement value for at least one pixel of the first image associated with the filtered photosensitive site based on a detection level of the filtered photosensitive site measured when the photosensitive site is identified as available.

7. The electro-optical system according to claim 6, wherein: The electro-optical system includes: a controller for determining multiple different frame exposure times for multiple different frames based on multiple different illumination levels of multiple objects in a field of view of the electro-optical system, wherein the controller is configured to determine the multiple frame exposure times of the electro-optical system by maximizing the multiple frame exposure times while keeping a number of multiple unavailable photosensitivity sites for the multiple corresponding frames below a predetermined threshold.

8. A method for generating image information based on data from a photodetector array, characterized in that: include: receiving first frame information, the first frame information including a first frame detection level for each photosensitive site of a plurality of photosensitive sites of the photodetector array, the first frame detection level indicating a light intensity detected by the corresponding photosensitive site during a first frame exposure time; Based on the first frame exposure time, identifying among the plurality of photosensitive sites of the photodetector array: (a) a first group of usable photosensitive sites, the first group of usable photosensitive sites including a first photosensitive site, a second photosensitive site, and a third photosensitive site, and (b) a first group of unusable photosensitive sites, the first group of unusable photosensitive sites including a fourth photosensitive site; generating a first image based on the first frame detection levels of the first group of available photosensitive sites, while ignoring the first frame detection levels of the first group of unavailable photosensitive sites; After receiving the first frame information, determining a second frame exposure time, wherein the second frame exposure time is longer than the first frame exposure time; receiving second frame information, the second frame information including a second frame detection level for each photosensitive site of the plurality of photosensitive sites of the photodetector array, the second frame detection level indicating a light intensity detected by the corresponding photosensitive site during the second frame exposure time; Based on the second frame exposure time, identifying among the plurality of photosensitive sites of the photodetector array: (a) a second group of available photosensitive sites, the second group of available photosensitive sites including the first photosensitive site, and (b) a second group of unavailable photosensitive sites, the second group of unavailable photosensitive sites including the second photosensitive site, the third photosensitive site, and the fourth photosensitive site; generating a second image based on the plurality of second frame detection levels of the second group of available photosensitive sites, while ignoring the plurality of second frame detection levels of the second group of unavailable photosensitive sites; After receiving the second frame information, determining a third frame exposure time, wherein the third frame exposure time is longer than the first frame exposure time and shorter than the second frame exposure time; receiving third frame information, the third frame information including a third frame detection level for each photosensitive site of the plurality of photosensitive sites of the photodetector array, the third frame detection level indicating a light intensity detected by the corresponding photosensitive site during the third frame exposure time; Based on the third frame exposure time, identifying, among the plurality of photosensitive sites of the photodetector array: (a) a third group of usable photosensitive sites, the third group of usable photosensitive sites including the first photosensitive site and the second photosensitive site, and (b) a third group of unusable photosensitive sites, the third group of unusable photosensitive sites including the third photosensitive site and the fourth photosensitive site; and A third image is generated based on the multiple third frame detection levels of the third group of available photosensitive sites, while ignoring the multiple third frame detection levels of the third group of unavailable photosensitive sites.

9. The method according to claim 8, characterized in that: The generation of each of the first image, the second image and the third image includes: calculating a replacement value for at least one pixel associated with a photosensitive site identified as unavailable for the corresponding image based on the detection level of at least one other adjacent photosensitive site identified as available for the corresponding image.

10. The method according to claim 8, characterized in that: The method includes: modeling the availability of multiple photosensitive sites of the photodetector array at different exposure times, wherein the determination of at least one frame exposure time of the second frame exposure time and the third frame exposure time is based on multiple results of the modeling, and wherein the identification of at least one unavailable photosensitive site group from the multiple unavailable photosensitive site groups is based on multiple results of the modeling.

11. The method according to claim 8, wherein: The determination of at least one of the second frame exposure time and the third frame exposure time includes maximizing the corresponding frame exposure time while keeping a number of unusable photosensitive sites for the corresponding frame below a predetermined threshold.

12. The method according to claim 8, wherein: The method includes evaluating dark current accumulation of at least one of the first image, the second image, and the third image, wherein the generating of the corresponding image includes subtracting the evaluation of the dark current accumulation from a plurality of photosensitive site detection levels of a plurality of available photosensitive sites of the corresponding image.

13. The method according to claim 8, wherein: The generation of at least one of the first image, the second image and the third image includes: calculating a replacement value for at least one pixel associated with a photosensitive site identified as unavailable for the corresponding image based on a detection level of the photosensitive site measured when the photosensitive site was identified as available.

14. The method according to claim 8, wherein: The method includes: modeling the availability of the plurality of photosensitive sites of the photodetector array at different exposure times, wherein the determination of at least one of the second frame exposure time and the third frame exposure time is based on a plurality of results of the modeling, wherein the identification of at least one group of unavailable photosensitive sites among the plurality of groups of unavailable photosensitive sites is based on the plurality of results of the modeling; The generation of each of the first image, the second image and the third image includes: (a) calculating a replacement value for at least one pixel associated with a photosensitive site identified as unavailable for the corresponding image based on the detection level of at least one other adjacent photosensitive site identified as available for the corresponding image; and (b) calculating a replacement value for at least one pixel associated with a photosensitive site identified as unavailable for the corresponding image based on a detection level of the photosensitive site measured when the photosensitive site was identified as available.

15. The method according to claim 14, characterized in that: The method includes evaluating dark current accumulation of at least one of the first image, the second image, and the third image, wherein the generating of the corresponding image includes subtracting the evaluation of the dark current accumulation from a plurality of photosensitive site detection levels of a plurality of available photosensitive sites of the corresponding image.

16. A non-transitory computer-readable medium, comprising: For generating image information based on data from a photodetector array, the non-transitory computer-readable medium includes a plurality of instructions stored thereon, and when the plurality of instructions are executed on a processor, the plurality of instructions perform the following steps: receiving first frame information, the first frame information including a first frame detection level for each photosensitive site of a plurality of photosensitive sites of the photodetector array, the first frame detection level indicating a light intensity detected by the corresponding photosensitive site during a first frame exposure time; Based on the first frame exposure time, identifying among the plurality of photosensitive sites of the photodetector array: (a) a first group of usable photosensitive sites, the first group of usable photosensitive sites including a first photosensitive site, a second photosensitive site, and a third photosensitive site, and (b) a first group of unusable photosensitive sites, the first group of unusable photosensitive sites including a fourth photosensitive site; generating a first image based on the first frame detection levels of the first group of available photosensitive sites, while ignoring the first frame detection levels of the first group of unavailable photosensitive sites; After receiving the first frame information, determining a second frame exposure time, wherein the second frame exposure time is longer than the first frame exposure time; receiving second frame information, the second frame information including a second frame detection level for each photosensitive site of the plurality of photosensitive sites of the photodetector array, the second frame detection level indicating a light intensity detected by the corresponding photosensitive site during the second frame exposure time; Based on the second frame exposure time, identifying among the plurality of photosensitive sites of the photodetector array: (a) a second group of available photosensitive sites, the second group of available photosensitive sites including the first photosensitive site, and (b) a second group of unavailable photosensitive sites, the second group of unavailable photosensitive sites including the second photosensitive site, the third photosensitive site, and the fourth photosensitive site; generating a second image based on the plurality of second frame detection levels of the second group of available photosensitive sites, while ignoring the plurality of second frame detection levels of the second group of unavailable photosensitive sites; and determining a third frame exposure time after receiving the second frame information, the third frame exposure time being longer than the first frame exposure time and shorter than the second frame exposure time; receiving third frame information, the third frame information including a third frame detection level for each photosensitive site of the plurality of photosensitive sites of the photodetector array, the third frame detection level indicating a light intensity detected by the corresponding photosensitive site during a third frame exposure time; Based on the third frame exposure time, identifying from a plurality of photosensitive sites of the photodetector array: (a) a third group of usable photosensitive sites, the third group of usable photosensitive sites including the first photosensitive site and the second photosensitive site, and (b) a third group of unusable photosensitive sites, the third group of unusable photosensitive sites including the third photosensitive site and the fourth photosensitive site; and A third image is generated based on the multiple third frame detection levels of the third group of available photosensitive sites, while ignoring the multiple third frame detection levels of the third group of unavailable photosensitive sites.

17. The non-transitory computer-readable medium of claim 16, wherein: The non-transitory computer-readable medium includes a plurality of instructions stored thereon, which, when executed on a processor, perform the steps of: modeling the availability of a plurality of photosensitive sites of the photodetector array at a plurality of different exposure times, wherein the determination of at least one of the second frame exposure time and the third frame exposure time is based on a plurality of results of the modeling, wherein the identification of at least one of the plurality of unavailable photosensitive site groups is based on a plurality of results of the modeling.

18. The non-transitory computer-readable medium of claim 16, wherein: The non-transitory computer-readable medium includes a plurality of instructions stored thereon, which, when executed on a processor, perform the steps of: determining at least one of the second frame exposure time and the third frame exposure time so as to maximize the corresponding frame exposure time while keeping a number of multiple unavailable photosensitive sites for the corresponding frame below a predetermined threshold.

19. The non-transitory computer-readable medium of claim 16, wherein: The non-transitory computer-readable medium includes a plurality of instructions stored thereon, which, when executed on a processor, perform the steps of: evaluating dark current accumulation of at least one of the first image, the second image, and the third image, wherein the generation of the corresponding image includes: subtracting the evaluation of the dark current accumulation from the plurality of detection levels of the plurality of available photosensitive sites of the corresponding image.

20. The non-transitory computer-readable medium of claim 16, wherein: The non-transitory computer-readable medium includes a plurality of instructions stored thereon, which, when executed on a processor, perform the steps of generating at least one of the first image, the second image, and the third image, thereby including calculating a replacement value for at least one pixel associated with a photosensitive site identified as unavailable for the corresponding image based on a detection level of the photosensitive site measured when the photosensitive site was identified as available.

Images