Dynamic lateral and temporal resolution pixel array

Abstract

The present invention relates to an improved imaging system and method based on single photon detectors (SPDs) and in which false positives are suppressed.

Description

[Technical field]

[0001] The present invention relates to a sensor system for imaging with very high spatial and temporal resolution, for which an array of single photon detectors (SPDs) is provided whose output signals are subject to evaluation logic to remove false positives due to ambient light, thermal noise, and other effects. [Background technology]

[0002] Prior art high speed imaging systems have to address many requirements and challenges. The first challenge is the detection accuracy of the incoming photons. Higher and higher spatial resolution is required. As a result, the sensor array is subdivided into more and more individual detectors (pixels). This means that more and more computational power is needed to read all these detectors and process the output signals into an image. Since the individual pixels (must) be ever smaller, they must have high light sensitivity, since they have a limited spatial window for capturing photons. For this reason, very sensitive detectors like SPDs and SPADs (single photon avalanche detectors) are often considered.

[0003] However, such detectors have the inherent drawback that their high light sensitivity results in unwanted excitation due to both ambient light and thermal noise, which, as such, at the detector level is difficult to distinguish from "real" detections resulting from the incidence of reflected light intentionally emitted by the system to scan the scene.

[0004] Add to this the requirement that imaging systems be used in a wide range of conditions, from virtually complete darkness to very bright situations, varying in terms of reflectivity of the objects / environments being imaged, as well as distance to the imaging system, making it very challenging to find a single solution that can eliminate false positives and dynamically predict the various situations in which imaging will be performed.

[0005] The object of the present invention is to find a solution to at least some of the aforementioned problems. Summary of the Invention

[0006] The present invention relates to an improved high speed sensor imaging system as claimed in claim 1.

[0007] In further aspects, the invention relates to the further embodiments defined in claims 2 to 15. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a process flow for parallel processing of detector data under different sets of spatiotemporal conditions according to an embodiment of the present invention. [Diagram 2] 2A-2C illustrate a system according to an embodiment of the invention in several distinct situations in which a set of related spatiotemporal conditions is used. [Diagram 3] FIG. 3 is a circuit implementation diagram of a pixel sensor according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Unless otherwise defined, all terms used in the description of the present invention, including technical and scientific terms, have the meanings commonly understood by those skilled in the art of the present invention. In order to better appreciate the description of the present invention, the following terms are explicitly explained.

[0010] "A," "an," and "the" are used herein to refer to both the singular and the plural, unless the context clearly indicates otherwise. For example, "a segment" means one or more segments.

[0011] When "approximately" or "around" is used herein with respect to a measurable quantity, parameter, duration or moment, etc., it means a variation relative to the cited value and within ±20%, preferably within ±10%, more preferably within ±5%, even more preferably within ±1%, even more preferably within ±0.1% of the cited value, insofar as such variations are applicable in the described invention. However, it should be understood that the value of the quantity where the term "about" or "approximately" is used is itself specifically disclosed.

[0012] The terms "comprise," "comprising," "consist of," "consisting of," "provided with," "contain," "containing," "include," "including," "hold," and "holding" are synonymous and are inclusive or open-ended terms indicating the presence of what follows without excluding or excluding the presence of other components, features, elements, materials, or steps that are known or described in the state of the art.

[0013] Recitation of a numerical interval by endpoints includes those endpoints, and all integer, fractional, and / or real numbers between the endpoints.

[0014] In a first aspect, the present invention relates to a high-speed sensor imaging system, comprising one or more light sources and an array with a number of single photon detectors (or SPDs), said detectors being spatially distributed on said array in a substantially matrix shape, preferably at regular intervals from each other, whereby said SPDs are suitable for detecting single photons and record said detection of single photons by means of a detection signal. Preferably, said SPDs are SPADs (Single Photon Avalanche Detectors).

[0015] The system further comprises an evaluation circuit, the detector is connected to the evaluation circuit, the evaluation circuit being configured to ascertain a detection signal or an output signal of the detector based on a spatiotemporal condition, the detector is connected such that an output signal of the detector (related to detection or non-detection of an incident photon at the detector) is sent to the evaluation circuit.

[0016] The spatiotemporal conditions for verifying the detection signal of the detector to be verified (i.e. verifying that the detection signal is not related to a false positive signal, but is in fact related to the beam scanned by it) are: observing a programmable minimum number of detection signals at detectors located within a virtual macro-pixel associated with the detector to be identified within a time segment related to the observation time of the detection signal of the detector to be identified, the macro-pixel being located proximate to the detector to be identified and consisting of any programmable number of detectors, preferably consisting of at least directly adjacent detectors, or alternatively consisting of directly adjacent detectors in one direction along each axis, e.g. left and below, or right and above, or another combination (e.g. two or three of four directly adjacent detectors); This includes the following conditions.

[0017] The term "macro-pixel" refers to a virtual pixel composed of several pixels or detectors, typically forming a contiguous cluster. The macro-pixel is associated with a specific set of spatio-temporal conditions and may vary in size, shape and other parameters depending on the situation. Macro-pixels may overlap each other and have common pixels or detectors. Preferably, macro-pixels have a square or rectangular shape, but may also have a roughly circular or elliptical, triangular, cross or star shape or other shapes. A macro-pixel is composed of at least two detectors (e.g., in a 2x1 or 1x2 matrix shape), more preferably at least four detectors (e.g., 2x2).

[0018] The spatial element of the condition relates to the requirement that a minimum number of detectors within a macropixel generate a detection signal (i.e. observe a photon) within a certain time segment of each other. The time segment may be bounded to the first detection within the macropixel (e.g. up to 10 ns after the first detection) or may be a fixed continuous period (e.g. every 10 ns). The length of the time segment and / or the minimum number of detectors generating a detection signal can be adapted by the user and / or automatically by the system. Preferably, however, the user can adapt both as desired.

[0019] The detector consists of semiconductor elements that together form an array and generate an output signal when a photon is incident on them. Typically, the detector has a pn junction that is under a reverse bias voltage above the breakdown voltage, so that an incident photon triggers breakdown and a multiplied output signal is generated. However, a major challenge with the array has been that the evaluation circuitry (instruments, etc.) occupies significant surface area, unavailable for the photon sensitive area of ​​the detector itself.

[0020] In a preferred embodiment, the system concerns a stacked sensor system, in which the detector is arranged in a first layer and the evaluation circuit is arranged in a second layer below the first layer. Additional components such as quenching circuits may be arranged in the first, second or third, fourth etc. layers, but are preferably arranged in the first or second layer. The detector, or at least the light-sensitive surface area, is arranged in the first layer above the second layer so as not to block part of the surface area. The division of the system into layers with different functions ensures that the maximum surface area can be used as the effective light-receiving surface area, while processing or evaluation circuits can be arranged in the lower layers. The different layers are typically made of different semiconductor wafers (or even different chips) connected to ICs (integrated circuits), allowing optimal use of the available surface area for photon collection and easy processing of the signal from the detector.

[0021] In one possible embodiment, the system comprises a separate evaluation circuit for each detector, which may be supplied with the output signal of each detector of the array or a part thereof. The part may for example be predefined as all detectors in a certain area around the detector associated with the evaluation circuit, for example all directly adjacent detectors or all directly adjacent and all secondarily adjacent detectors (secondarily adjacent being detectors directly adjacent to the detector adjacent to the detector associated with the evaluation circuit). Variations are also possible, such as including diagonally adjacent detectors (which form a square in the matrix array).

[0022] In yet another embodiment, an evaluation circuit is associated with a given cluster of detectors, said evaluation circuit being able to process the output signals of said detectors depending on imposed conditions. By overlapping clusters of evaluation circuits, the risk that there is no "right" evaluation circuit to process the incidence on a certain detector is eliminated.

[0023] In one possible embodiment, only one evaluation circuit is provided which processes the output signals of the detectors in parallel, in which case the evaluation circuit preferably has as many outputs (effective detector outputs) as inputs (detectors).

[0024] In a preferred embodiment, the evaluation circuit is able to modify the spatiotemporal conditions based on the context of the scene in which the image is formed. In particular, this is based on objectively observable parameters, including the intensity of the detected light, and on disturbing light (its intensity). In this way, it can be determined that stricter or less strict requirements may / should be imposed depending on whether the signal to be detected (detected light) is strong or weak, or that stricter or less strict requirements may / should be imposed depending on whether there is more or less disturbing light.

[0025] When the intensity of the disturbance light slightly exceeds a certain threshold, false positives increase, but this is localized. For this reason, in a further preferred embodiment, a minimum number N of detection signals in a macro pixel is selected, where N is at least 2 (e.g., 2, 3, 4 or more). Below said threshold, disturbance light is less of a problem, and one can choose to set the minimum number of detection signals to M, where M is at least 1. It is noted that further options can be set, for example, a second threshold ensures a minimum number of detection signals required from Q, where Q is at least 3.

[0026] If the detected light intensity exceeds the threshold, a strongly reflected (active) signal is assumed, and the ambient light and thermal noise can be excluded again by limiting the observation time window. In this case, the duration of the time segment is set to at most T1. Below said threshold, a duration of at least T2 is selected, T2 being greater than T1, T1 being at least 1 ns, preferably at least 5 ns. Preferably, T2 is at least 10 ns, more preferably at least 20 ns or 50 ns.

[0027] By setting the conditions appropriately, it is possible to ensure that the evaluation circuitry applies strong filtering to the signals from the individual detectors. In the case of a lot of ambient light or thermal noise, the bar may be raised, e.g. requiring that the incident photon hits a number of detectors in a macropixel of 2x2 detectors (or 3x3, 2x3, 3x2, 1x2, 2x1, 1x3, 3x1 or other formats), e.g. at least X% and / or at least Y detectors that record a detection in a time segment in a macropixel. Thus, in the case of "very" strong signals here, one or more stricter conditions can be set (X% of the detectors in a macropixel). 2 % and / or Y 2 detectors, X 3 and / or Y 3, etc.), which automatically ignores more sporadic and spatially spread photons from ambient light and thermal noise, since it is highly unlikely that two (or more) detectors would detect such a photon from a macropixel within one and the same time segment.

[0028] Conversely, if little ambient light and thermal noise is detected, the threshold can be set very low, i.e., every detection can be confirmed to be a "real" photon impact.

[0029] In the case of a strong active signal (i.e. many incident photons as a result of exposing the object or scene to be imaged), the bar may be raised and the duration of the time segment may be required to be set to a low threshold, for example, up to 10.0ns, 5.0ns, 2.5ns, or even up to 1.0ns. In this way, it is ensured that thermal noise and ambient light are typically filtered out, since a strong active signal practically guarantees that some photons are incident on the (effectively exposed) macropixel during the short duration, although again, it is highly unlikely that the required M or N detectors in the macropixel will observe a detection within said short duration. Again, several steps from stricter to looser conditions can be imposed depending on the strength of the active signal. In the case of a weak signal, the time window is typically extended to at least 10ns, preferably at least 20ns or even 50ns.

[0030] By combining both of the aforementioned parameters, the effects of ambient light and thermal noise can be virtually 100% eliminated, significantly reducing the computational power required to filter out false positives.

[0031] It should be noted that in certain embodiments, the duration of the time segments can be determined by the ambient light (above a threshold, the duration is set shorter, below a threshold, the duration is set longer), so that the strength of the active signal (detected light) may or may not be taken into account as a parameter.

[0032] Conversely, in certain embodiments, the detected light (active signal) can also influence the required minimum number of detected signals in a macro-pixel (above a threshold, set to a higher number, below a threshold, set to a lower number), so that the intensity of ambient light may or may not be taken into account as a parameter.

[0033] In a preferred embodiment, the light source emits a light beam or flux with a known (flux) diameter and / or a known cross-section, preferably with a shape other than circular or elliptical. The evaluation circuit is configured to further adapt the spatiotemporal conditions based on the flux diameter and / or cross-section, whereby the shape and / or number of detectors in a macropixel preferably depends on the flux diameter and / or cross-section and / or the detectors generating detection signals in the time segment preferably have a shape approximating the known cross-section. However, alternatively or additionally, additional conditions can be imposed, such as that the detectors recording detection signals are spatially located relative to one another in a shape approximating the cross-section of the emitted flux. By using a flux of a particular shape, such as a cross-shape, the reflected flux will keep a similar shape (or at least a significant portion of the photons entering the array as a result of exposure by the light source will roughly approximate this shape), allowing a more targeted search. In this way, the shape of the macropixel can be adapted to the known cross-section or, as explained above, a verification pattern can be imposed.

[0034] Approximating the shape of a known cross-section can be interpreted broadly, including among other things its complete enclosure (such as a 3x3 array with detected signals includes a cross, includes a line, etc.) The system can also be configured to tolerate a certain level of deviation, such as the absence of one or more (or X%) of the "pixels" (detectors) required to represent the known cross-section.

[0035] In this way, the beam diameter can also be used to adjust the size of the macropixel. A wider beam (larger diameter) leads to a more spatially spread recurrent photon beam, so a larger macropixel (more detectors) may be advantageous. Therefore, a threshold value (or several values) for the beam diameter can be applied here too, which determines the number of detectors in a macropixel and / or the number of detectors that record a detection signal in said macropixel within a time segment and / or the duration of said time segment.

[0036] In a preferred embodiment, the evaluation circuit clusters the observed detection signals by time segments, whereby the time segments are consecutive and have equal duration. The time segments associated with the observation times of the detection signals of the detectors to be checked are the time segments in which the detection signals of the detectors to be checked are observed. In this embodiment, the evaluation circuit reads the detector outputs (directly or already clustered by macropixels) during certain time segments. This allows, for example, that the output signals are also "reset" (for example via an active quenching circuit (AQAR or AQPR, etc.)) after each measurement by the evaluation circuit. Alternatively, the reset can be performed immediately, for example while the evaluation circuit records the detection signals with or without time stamps.

[0037] In an alternative embodiment, the time segment begins only with the first detection signal of a detector from a macropixel, and detection is confirmed if a desired minimum number of detectors within a macropixel have produced a detection signal within a predefined duration of the time segment.

[0038] For this purpose, the evaluation circuit detects the slope (rising slope) of the detection signal, for example by means of a flip-flop circuit, and converts this into a digital signal (1 or 0) which can be easily processed by a logic circuit for further processing.

[0039] In a preferred embodiment, the virtual macro-pixels can be modified based on the ambient light and based on the intensity of the detected light, such that if ambient light below a second predefined threshold is detected, a first virtual macro-pixel around the detector to be checked is used, and if ambient light above the second predefined threshold is detected, a second virtual macro-pixel around the detector to be checked is used, such that the second virtual macro-pixel has fewer detectors than the first virtual macro-pixel.

[0040] Moreover, it is possible to further define third, fourth etc. macro-pixels with deviating shapes (configuration of detectors) and / or sizes (number of detectors). The macro-images thus defined are applied, for example in the area of ​​the desired resolution, under specific conditions regarding ambient light, intensity of detected light (active signal) and / or other (manual) settings.

[0041] In a preferred embodiment, the detector comprises a quenching circuit which normalizes the detection signal of the detector. The quenching circuit may be of the active or passive type. Preferably, the quenching circuit concerns an active quenching circuit which is controlled by the evaluation circuit and which "resets" the detector at the appropriate time. Preferably, the quenching circuit is AQAR (active quenching active reset), but AQPR (active quenching passive reset) is also an option. By providing a quenching circuit, the duration of the time segments can be checked very accurately and the detector can be reset quickly enough to detect new photons.

[0042] In one possible embodiment, the quenching circuit can also be controlled to reset the detector as soon as a detection signal is recorded, so that if the time segment is long enough (and the quenching circuit operates quickly enough, so that the dead time is short), detection of an incident photon by one and the same detector is possible within the same time segment.

[0043] In a preferred embodiment, the evaluation circuit is configured to validate the detection signal of the detector based on a plurality of sets of spatiotemporal conditions, whereby the evaluation circuit processes the detection signal according to each set of the plurality of spatiotemporal conditions in parallel.

[0044] Each of the plurality of sets of spatiotemporal conditions for verifying a detection signal of a detector to be verified is observing a programmable minimum number of detection signals in a time segment related to the observation time of the detection signal of the detector to be identified, at detectors located within a virtual macro-pixel related to said detector to be identified, said macro-pixel being located in close proximity to said detector to be identified and consisting of any programmable number of detectors, preferably consisting of at least directly adjacent detectors; This includes the following conditions. Thereby, each set of the multiple sets of spatiotemporal conditions may have a different minimum number of detected signals and / or a different duration of time segments for validation, relative to each other.

[0045] The system can use several predefined sets of conditions to impose them in parallel on the "raw" detector data (detector output signal), allowing a scene to be reconstructed in different ways in one scan instead of several sweeps if the results of the previous set of conditions were not satisfactory (too low resolution, too noisy, etc.). Furthermore, images produced by different sets can be combined, and areas of an image where one set is lacking in terms of settings can be completed / corrected using parts of images from one or more other images.

[0046] In a further preferred embodiment, the multiple sets of spatiotemporal conditions comprise a first set, a duration T1 of the first set of time segments is at least 10 ns, preferably at least 50 ns, and a minimum number M1 of the first set of detection signals is equal to 1. The multiple sets of spatiotemporal conditions comprise a second set, a duration T2 of the second set of time segments is less than 10 ns, and a minimum number M2 of the second set of detection signals is at least 2. The multiple sets of spatiotemporal conditions comprise a third set, a duration T3 of the third set of time segments is at least 10 ns, preferably at least 50 ns, and a minimum number M3 of the third set of detection signals is equal to 1.

[0047] Since the largest variations, which are hardly controlled, can occur in ambient light, the above three sets of conditions cover most situations: a first set for weak active signal and limited ambient light, a second set for moderate ambient light, and a third set for strong ambient light and / or weak active signal. Further sets can be provided to cover further variations in the intensity of the detected light (active signal) and / or ambient light.

[0048] In a preferred embodiment, the evaluation circuit is configured to define the macro-pixels, whereby the detection signals of the detectors are binned together in one macro-pixel and the spatio-temporal conditions are imposed on the binned detection signals. The macro-pixels can be pre-programmed (according to certain rules, depending or not on the shape and size of the detector array). This allows the macro-pixels to be adjacently arranged without overlap or to have limited overlap. In a particular embodiment, for any set of spatial conditions, a macro-pixel is associated with all detectors, and a detector can belong to 2, 3, 4 or more macro-pixels. Defining the macro-pixels through the evaluation circuit allows easy aggregation / combination of all detection signals per macro-pixel. If other conditions are imposed using a different definition of the macro-pixels (shape, size), the correct detection signals are automatically combined to the new macro-pixels as well.

[0049] In a preferred embodiment, the evaluation circuit is configured to redefine the macropixels, thereby adapting the number of detectors per macropixel. Preferably, the evaluation circuit is configured to automatically redefine the macropixels based on the detection signals of the detectors, preferably based on the total number of detection signals per unit time. As mentioned above, making the macropixels adaptable is a powerful tool to accommodate situations such as active signals and ambient light, and / or the shape of the emitted light bundle / beam. Imposing restrictions on the size or shape of the macropixels may help to filter out false positives.

[0050] In a preferred embodiment, the system is preprogrammed with a macro-pixel capable of adopting at least two of the following configurations: 2x1, 1x2, 2x2, 3x1, 1x3, 3x2, 2x3, 3x3, and / or a cross or star (one central detector and one directly adjacent detector, respectively). Preferably, at least 3, 4, 5 or more configurations can be adopted. The most important configurations here are 2x1, 1x2 and 2x2.

[0051] Other possible configurations are, for example, a diagonal line (two or more detectors connected diagonally), a diagonal cross or a star.

[0052] In a preferred embodiment, the evaluation circuit is programmed to make the time segments follow one another cyclically, or alternatively, the time segments are triggered macro-pixel by macro-pixel by receiving a detection signal in the evaluation circuit of the detector from the macro-pixel.

[0053] In a preferred embodiment, a further spatio-temporal condition is imposed on the detection signal seen at a detector in a first macropixel, said further spatio-temporal condition comprising the condition that within a predefined time window of the detection signal seen at a detector in said first macropixel, a detection signal seen in relation to a detector in a macropixel adjacent to said first macropixel is detected, where adjacent macropixels are defined as macropixels each having at least one non-common detector, having at least one detector in common and / or each having at least a detector adjacent to a detector of another macropixel of said first macropixel and said adjacent macropixels in said matrix-shaped arrangement, whereby not only is a detector of one of said macropixels also a detector of another macropixel, but also macropixels having one or more adjacent detectors and / or at least one common detector.

[0054] The above-mentioned embodiments exploit the (relative) predictability of the (light beam) movement of the scanning light source. Typically, the light source has a continuous movement (e.g., one continuous curve), so it can be expected that the incident light on the detector array follows a substantially continuous pattern over time. However, more slack (is tolerated), more abrupt jumps, and even discontinuities may occur. However, typically, depending on the movement of the incident light beam from an object on the scene / array, if a detection is found in one macro-pixel, it will also be found in neighboring macro-pixels in a previous time window. By imposing this as an additional condition, any further false positives that slip through the net can also be filtered out.

[0055] This principle can also be used to reduce the region of interest in which the evaluation circuit processes signals. In this way, once a detection is confirmed in a macropixel, the next detection is expected to be within a certain range of the previous detection, and the evaluation circuit can simply consider and process signals from nearby macropixels in successive time windows. The range can be determined dynamically (based on the previously confirmed detection and the macropixel "jump" for each time window) or it can be determined absolutely by the system according to a predefined value (distance of X detectors / macropixels to the previously confirmed detection). By limiting the region of interest, the system can significantly reduce its computational load and not have to consider signals from further detectors. Furthermore, in situations where the incident light falls outside the region of interest (ROI), since no incident is detected, the system can easily identify this and expand the ROI (e.g. gradually or instantly to the entirety) to have the light source repeat a very limited part of the sequence.

[0056] In a preferred embodiment, a first set of the plurality of sets of spatio-temporal conditions uses a macro-pixel with a first number of detectors, a second set of the plurality of sets of spatio-temporal conditions uses a macro-pixel with a second number of detectors, the first and second numbers of detectors being different from each other, and preferably a third set of the plurality of sets of spatio-temporal conditions uses a macro-pixel with a third number of detectors, the third number of detectors being different from the first and second numbers of detectors. The advantages of this are as mentioned above, and it allows to increase / decrease the resolution in different situations and to adapt the checking conditions to the situation (ambient light, strength of active signal, etc.).

[0057] In a preferred embodiment, the detectors in a macro-pixel having K×L detectors are arranged in a square or rectangular configuration. The detectors in the macro-pixel are divided by the evaluation circuit into a set of detectors i=1···R, P i is less than or equal to K / 2, Q i P i ×Q ithe detection signals of the detectors are aggregated by the evaluation circuit into a sub-macropixel detection signal for each sub-macropixel, the evaluation circuit being configured to impose the spatio-temporal condition on the sub-macropixel and sub-macropixel detection signals of the macropixel instead of the detection signals of the detectors and the macropixel.

[0058] In this way, the resolution can be dynamically adapted depending on the situation, and if a detection is confirmed within a macro-pixel, one can simultaneously choose to form a higher resolution image via the sub-macro-pixels.

[0059] In a preferred embodiment, the system comprises one or more electronic circuits between the detector and the evaluation circuit, where applicable integrated in the detector, which convert the output signal of the detector into a discrete signal (presence or absence of a detection signal) and send it to the evaluation circuit. The electronic circuit may perform additional operations such as adding a time stamp to the discrete signal or adding information about the position of the detector relative to the signal. The system is preferably configured to synchronize the electronic circuits of the array with each other.

[0060] As mentioned above, a quenching circuit may be provided for the detector.

[0061] In a further embodiment, the evaluation circuit can also record for each macro pixel how many detection signals are generated within a time segment, which allows obtaining further physical information about the scene / object being photographed.

[0062] The present invention is illustrated below by non-limiting examples which illustrate the invention and are not intended, nor should they be construed, to limit the scope of the invention. EXAMPLES

[0063] First Example: 1 illustrates a process flow for parallel processing of signals (20) from a detector (19) in multiple parallel layers. First, the raw data (20) itself is input to an evaluation circuit where it can be processed under different sets of conditions (21) to generate different results (22), i.e. data layers 1-N. These data layers can then be further processed into an image for a final user (23). This further processing can be, for example, the selection of a particular data layer or a combination of multiple data layers.

[0064] Example 2: 2A-C are diagrams illustrating possible conditions belonging to different spatiotemporal condition sets. The array (24) with detectors (2) is presented as 5 rows and 5 columns, with each cell representing a detector. The subarray with the thick edges represents a virtual macropixel (25), while the central cell with the diagonal lines represents the detector generating the detection signal.

[0065] Figure 2A illustrates the full-pass situation, where there is little ambient light and the spatiotemporal conditions are invalid, so all detection signals are accepted as confirmed detections (M1=1).

[0066] 2B shows a situation where the spatiotemporal conditions mean that (M2=) 2 detection signals are recorded in a macropixel with 2×2 detectors in time segment T2. The figure shows 4 virtual macropixels (dark rectangles) associated with the exposed detectors, and the system now looks for a macropixel where another detector also records a detection signal in the time segment T2.

[0067] Figure 2C shows another case of virtual macro-pixel size, namely 3x3 detectors. In this case too, the system looks for cases where M3 (for example equal to 2) detection signals are recorded in one and the same macro-pixel within time segment T3. This is particularly applicable for situations with weaker active signals than in the situation of figure 2B.

[0068] Example 3: 3 shows a possible implementation at circuit level of a pixel sensor (1). The pixel sensor (1) comprises a photodetector (2), for example a photon detector or a photon avalanche diode. The photodetector (2) is capable of detecting single photons (3) incident thereon. Such an implementation can also be performed stack-wise, with subdivision between a detection layer (detector) and a processing layer (evaluation circuit).

[0069] The photodetector (2) is powered by a power supply (4) and is connected in a voltage divider configuration to a resistor (5). The photodetector (2) is arranged in a reverse bias configuration. The resistor (5) is connected to a first reference potential level (6), preferably ground level or 0V.

[0070] When a photon (3) strikes the photodetector (2), a reverse current is generated, which results in a voltage drop (7) across resistor (5). The voltage drop (7) has a logic "1" when a photon (3) is detected at the photodetector (2) and a logic "0" when no photon (3) is detected at the photodetector (2).

[0071] The voltage loss (7) is compared to a predefined voltage threshold level (8) via a comparator (9). If the voltage loss (7) is greater than the reference voltage (8), a local detection signal (10) is generated as the output of the comparator (9). For example, in case of detection, a logic "1" is generated as the output of the comparator, and in case of non-detection, a logic "0" is generated as the output of the comparator.

[0072] Each pixel sensor (1) has a local control circuit (18). The comparator (9) functions as a buffer between the photodetector (2) and the local control circuit (18). The local control circuit (18) has a local reset (11) and a local reset (12).

[0073] The control circuitry, or parts thereof, may be physically located on different layers within the sensor system, for example the pixel sensors (1) of the sensor group may be located on a first semiconductor layer while the control circuitry (18) for each pixel sensor (1) in the sensor group may be located on a second semiconductor layer, i.e. forming a stacked pixel sensor solution structure as known in the art.

[0074] The local detect signal (10) is sent to a local enable means (11). The local enable means (11) consists of two NMOS transistors. However, other transistor types or configurations may be used. The local detect signal (10) is fed to the ports of the transistors. One transistor is connected to a row bus (16) and the other transistor is connected to a column bus (17). When the local detect signal (10) is received at the port of the local enable means (11), the local enable means (11) is activated. In this case, the transistor acts as a switch and is switched on, for example by a short circuit, when a logic "1" is received at the transistor.

[0075] The local enabling means (11) is connected to the neighbour enabling means (12). In this case, each transistor of the local enabling means (11) is connected to said neighbour enabling means. The neighbour enabling means (12) consists of at least one transistor, in this embodiment three transistors with ports (13', 13'', 13'''). The ports (13', 13'', 13''') of the three transistors are connected to the local detection signals from the neighbouring pixel sensors. These transistors are also connected to a second reference potential level (14), preferably to a level equal to the first reference potential level (6), preferably to ground level or 0V. When at one port, for example (13'), at least one local detection signal of a neighbouring pixel sensor is received, said neighbour enabling means is activated. In this case, if said port (13') has a logic "1", this means that the transistor, here acting as a switch, is turned on, for example shorted.

[0076] When both the local enable means and the neighboring enable means are activated, i.e. when a transistor of the local enable means is operating as a short and one transistor of the neighboring enable means is operating as a short, a global sense signal (15) is output to the row bus (16) and column bus (17). The global sense signals of different pixel sensors on the row bus (16) are summed to form a row sense signal. The global sense signals from different pixel sensors on the column bus (17) are summed to form a column sense signal.

[0077] The local control circuit (18) in this example acts as an AND port, i.e. when the local enabling means (11) and the proximal enabling means (12) are activated, the global detection signal (15) is generated.

[0078] The present invention is not limited to the embodiments described above, and it is envisaged that numerous modifications or variations can be made to the described examples without reassessing the appended claims.

Claims

1. A high-speed sensor imaging system, said system comprising one or more light sources, and comprising an array (24) comprising a plurality of single photon detectors (SPDs) (2) spatially distributed on said array (24) in a substantially matrix shape, preferably at regular intervals from one another, whereby said SPDs (2) are suitable for detecting single photons (3), and recording the detection of said single photons (3) by a detection signal, the system further comprises at least one evaluation circuit, preferably one evaluation circuit per detector (2), whereby at least two detectors (2), preferably four detectors (2), are connected to the evaluation circuit, the evaluation circuit being configured to check detection signals or output signals of the detectors (2) based on spatiotemporal conditions, The spatiotemporal conditions for checking the detection signal of the detector (2) to be checked are: observing a programmable minimum number of detection signals in a time segment related to the observation time of a detection signal of a detector (2) to be confirmed, the detection signals being located in a virtual macro-pixel (25) related to the detector (2) to be confirmed, the macro-pixel (25) being composed of an arbitrarily programmable number of detectors located in close proximity to the detector (2) to be confirmed, preferably composed of at least directly adjacent detectors (2); Including the condition that Thereby, the detector (2) is arranged in a first layer (19) and the at least one evaluation circuit is arranged in a second layer (21), the second layer (21) being located below the first layer (19), whereby the first layer (19) is a detection layer and the second layer (21) is a processing layer. High-speed sensor imaging system.

2. 2. The high-speed sensor imaging system of claim 1, wherein the evaluation circuit is configured to modify the spatiotemporal conditions based on ambient light and based on intensity and / or other characteristics of the detected light.

3. 3. The high-speed sensor imaging system according to claim 2, the system is configured to set a minimum number of detection signals in the detectors (2) located within the virtual macro-pixel (25) upon detection of ambient light exceeding a first predefined threshold to a value of at least N, and below the first predefined threshold to a value of at most M, where M<N, M being at least equal to 1 and N being at least equal to 2; The system is configured to set the duration of the time segment to a value of at most T1 upon detecting an intensity of detected light above a first predetermined threshold, and to a value of at least T2 below the first predetermined threshold, where T2>T1 and T1 is at least equal to 1 ns.

4. A high-speed sensor imaging system as described in claim 1, wherein the system is configured to confirm a detection signal when at least two pre-programmed sets of distinct spatiotemporal conditions are satisfied in parallel.

5. A high-speed sensor imaging system as described in claim 1, wherein the light source emits a light beam or flux having a known flux diameter and / or a known cross-section, preferably the cross-section is a shape other than circular or elliptical, and the spatiotemporal conditions further depend on the flux diameter and / or cross-section, whereby preferably the shape and / or number of detectors in a macro pixel (25) depend on the flux diameter and / or cross-section.

6. A high-speed sensor imaging system as described in claim 1, wherein the evaluation circuit clusters the observed detection signals by time segments, such that the time segments are consecutive and have equal duration, whereby the time segment associated with the observation time of the detection signal of the detector (2) to be confirmed is the time segment in which the detection signal of the detector (2) to be confirmed was observed.

7. A high-speed sensor imaging system as described in claim 1, wherein the virtual macro pixel (25) can be modified based on both external light and the intensity of detected light, so that when external light below a second predetermined threshold is detected, a first virtual macro pixel around the detector (2) to be confirmed is used, and when external light exceeding the second predetermined threshold is detected, a second virtual macro pixel around the detector (2) to be confirmed is used, so that the second virtual macro pixel has fewer detectors (2) than the first virtual macro pixel.

8. A high-speed sensor imaging system as described in claim 1, wherein the detector (2) is provided with a quenching circuit for normalizing a detection signal of the detector (2), and preferably the quenching circuit is provided in the second layer or a third layer below the second layer.

9. In the high-speed sensor imaging system of claim 1, the evaluation circuit is configured to verify the detection signal of the detector (2) based on a plurality of sets of spatiotemporal conditions, whereby the evaluation circuit processes the detection signal in parallel according to each set of the plurality of sets of spatiotemporal conditions; Each of the plurality of sets of spatiotemporal conditions for verifying a detection signal of a detector (2) to be verified comprises: observing a programmable minimum number of detection signals in a time segment related to the observation time of a detection signal of the detector (2) to be confirmed, at detectors (2) located within a virtual macro-pixel (25) related to said detector (2) to be confirmed, said macro-pixel (25) being located close to said detector (2) to be confirmed and consisting of an arbitrary programmable number of detectors, preferably consisting of at least directly adjacent detectors (2); Including the condition that Whereby, for each of the plurality of sets of spatiotemporal conditions, the minimum number of detection signals for validation differs from each other, and / or the duration of the time segments differs. High-speed sensor imaging system.

10. The high-speed sensor imaging system of claim 9, wherein the multiple sets of spatiotemporal conditions have a first set, a duration T1 of a time segment of the first set is at least 10 ns, preferably at least 50 ns, and a minimum number M1 of detection signals of the first set is equal to 1, the multiple sets of spatiotemporal conditions have a second set, a duration T2 of a time segment of the second set is less than 10 ns, and a minimum number M2 of detection signals of the second set is at least 2, and the multiple sets of spatiotemporal conditions have a third set, a duration T3 of a time segment of the third set is at least 10 ns, preferably at least 50 ns, and a minimum number M3 of detection signals of the third set is equal to 1.

11. A high-speed sensor imaging system as described in claim 1, wherein the evaluation circuit is configured to define the macro pixel (25), whereby the detection signals of the detector (2) are binned together within one macro pixel (25) and the spatiotemporal conditions are imposed on the binned detection signals.

12. A high-speed sensor imaging system as described in claim 11, wherein the evaluation circuit is configured to redefine the macropixels, thereby enabling the number of detectors per macropixel to be adapted, and preferably the evaluation circuit is configured to automatically redefine the macropixels based on the detection signals of the detectors, preferably based on the total number of detection signals per unit time.

13. In the high-speed sensor imaging system according to claim 1, the macro pixels (25) are arranged in a matrix shape of the array (24), 2x1, 1x2, 2x2, 3x1, 1x3, 3x2, 2x3, 3x3, and / or A star consisting of one central detector and each of its directly adjacent detectors. The high speed sensor imaging system may employ at least two of the following configurations:

14. The high-speed sensor imaging system of claim 1, wherein the evaluation circuit periodically successively causes the time segments to follow one another.

15. In the high-speed sensor imaging system of claim 1, a further spatiotemporal condition is imposed on a detection signal seen by a detector in a first macropixel, the further spatiotemporal condition including a condition that a detection signal seen in association with a detector in a macropixel adjacent to the first macropixel is detected within a predetermined time window of the detection signal seen by the detector in the first macropixel, wherein adjacent macropixels are defined as non-overlapping macropixels, the adjacent macropixels having at least one detector in common and / or each having at least a detector adjacent to a detector of the first macropixel and other of the adjacent macropixels in the matrix-shaped array (24).

16. The high-speed sensor imaging system of claim 1, wherein a further spatiotemporal condition is imposed on a detection signal seen by a detector of a first macropixel, said further spatiotemporal condition including a condition that within a predetermined time window of the detection signal seen by a detector in said first macropixel, a detection signal seen in association with at least one other detector, preferably at least two other detectors, is detected in said first macropixel.

17. A high-speed sensor imaging system as described in claim 1, wherein a first set of the multiple sets of spatiotemporal conditions uses a macropixel (25) having a first number of detectors and a second set of the multiple sets of spatiotemporal conditions uses a macropixel (25) having a second number of detectors, the first and second numbers of detectors being different from each other, and preferably a third set of the multiple sets of spatiotemporal conditions uses a macropixel having a third number of detectors, the third number of detectors being different from the first and second numbers of detectors.

18. The high speed sensor imaging system of claim 1, wherein the detectors (2) in a macro pixel (25) having K×L detectors (2) are arranged in a square or rectangular configuration, and the detectors (2) are evaluated by the evaluation circuit to determine, in the macro pixel (25), i=1...R,P ｉ is less than or equal to K / 2, Q ｉ P ｉ ×Q ｉ a macropixel (25) for each of the detectors (2), wherein detection signals of the detectors (2) are aggregated by the evaluation circuit into a sub-macropixel detection signal for each sub-macropixel, and the evaluation circuit is configured to impose the spatiotemporal condition on the sub-macropixel detection signals of the sub-macropixels and the macropixel (25) instead of the detection signals of the detectors (2) and the macropixel (25).

19. A high-speed sensor imaging system according to any one of claims 1 to 18, wherein the high-speed sensor imaging system relates to a stacked sensor system.

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