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EP-4367488-B1 - PIXEL ARRAY WITH DYNAMIC LATERAL AND TEMPORAL RESOLUTION

EP4367488B1EP 4367488 B1EP4367488 B1EP 4367488B1EP-4367488-B1

Inventors

  • VAN DER TEMPEL, WARD
  • PEETERS, Johannes Willem
  • MIODEZKY, André Bernard
  • MOURAD, Christian

Dates

Publication Date
20260506
Application Date
20220629

Claims (18)

  1. High-speed sensor system, whereby the system comprises one or more light sources, and comprises an array (24) with a plurality of single-photon detectors SPDs (2), said detectors (2) being spatially distributed across the array (24) in a substantial matrix form, preferably at regular intervals from each other, whereby the SPDs (2) are suitable for detecting single photons (3), and register the detection of the single photon (3) with 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 4 detectors (2) are connected to the evaluation circuit, the evaluation circuit being adapted for confirming the detection signals or output signals of the detectors (2) based on spatiotemporal conditions; whereby the spatiotemporal conditions for confirmation of a detection signal of a detector (2) to be confirmed comprise the following conditions: observing a programmable minimum number of detection signals in detectors (2) located in a virtual macropixel (25) associated to the detector (2) to be confirmed within a time segment associated to the time of the observation of the detection signal of the detector (2) to be confirmed, said macropixel (25) comprising an, optionally programmable, number of detectors in the proximity of the detector to be confirmed, preferably comprising at least the immediately adjoining detectors (2); whereby the detectors (2) are comprised in a first layer (19), and whereby the at least one evaluation circuit is provided in a second layer (21), said second layer (21) being positioned under the first layer (19), whereby the first layer (19) is a detection layer, and the second layer (21) is a processing layer, characterised in that the evaluation circuit is configured for redefining the macropixels, whereby the number of detectors per macropixels can be adapted, preferably whereby the evaluation circuit is configured for automatically redefining the macropixels based on the detection signals of the detectors, preferably based on a total number of detection signals over a unit of time.
  2. High-speed sensor system according to claim 1, whereby the evaluation circuit is configured to modify the spatiotemporal conditions based on ambient light and based on the intensity and/or other properties of the detected light.
  3. High-speed sensor system according to claim 2, whereby the system is configured to, upon detection of ambient light above a first prefixed threshold value, set the minimum number of detection signals at detectors (2) located in the virtual macropixel (25) at a value of at least N, and below the first prefixed threshold value at a value of at most M, whereby M<N, with M at least equalling 1, and N at least equalling 2; whereby the system is configured to, upon detection of a strength of the detected light above a first prefixed threshold value, set the duration of the time segment at a value of at most T1, and below the first prefixed threshold value at a value of at least T2, whereby T2>T1, with T1 at least equalling 1 ns.
  4. High-speed sensor system according to any one of the previous claims 1 to 3, whereby the system is configured to confirm a detection signal if at least two pre-programmed sets of mutually different spatiotemporal conditions are met in parallel.
  5. High-speed sensor system according to any one of the previous claims 1 to 4, whereby the light sources emit a light beam or bundle with a known bundle diameter and/or known cross-section, whereby preferably the cross-section is not circular or oval, and whereby the spatiotemporal conditions further depend on the bundle diameter and/or cross-section, preferably whereby the form and/or the number of detectors in a macropixel (25) is dependent on the bundle diameter and/or cross-section.
  6. High-speed sensor system according to the previous claim 1 to 5, whereby the evaluation circuit clusters observed detection signals per time segment, whereby the time segments are consecutive and have an equal duration and whereby the time segment associated to the time of the observation 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 is observed.
  7. High-speed sensor system according to any one of the previous claims 1 to 6, whereby based on ambient light and based on the strength of detected light the virtual macropixel (25) can be modified, whereby in case ambient light is detected below a second prefixed threshold value a first virtual macropixel is used around the detector (2) to be confirmed, and in case ambient light is detected above the second prefixed threshold value a second virtual macropixel is used around the detector (2) to be confirmed, whereby the second virtual macropixel comprises fewer detectors (2) than the first virtual macropixel.
  8. High-speed sensor imaging system according to any one of the previous claims 1 to 7, whereby the detectors (2) are provided with a quenching circuit that normalises the detection signal of the detectors (2), preferably whereby the quenching circuit is provided in the second layer or in a third layer under the second layer.
  9. High-speed sensor imaging system according to any one of the previous claims 1 to 8, characterised in that the evaluation circuit is adapted for confirming the detection signals of the detectors (2) based on multiple sets of spatiotemporal conditions, whereby the evaluation circuit subjects the detection signals to each of the multiple sets of spatiotemperal conditions in parallel; whereby each of the multiple sets of spatiotemporal conditions for confirmation of a detection signal of a detector (2) to be confirmed comprises the following conditions: observing a programmable minimum number of detection signals in detectors (2) located in a virtual macropixel (25) associated to the detector (2) to be confirmed within a time segment associated to the time of the observation of the detection signal of the detector (2) to be confirmed, said macropixel (25) comprising an, optionally programmable, number of detectors in the proximity of the detector (2) to be confirmed, preferably comprising at least the immediately adjoining detectors (2), whereby each of the multiple sets of spatiotemporal conditions mutually comprises a different minimum number of detection signals and/or a different duration of the time segment for confirmation.
  10. High-speed sensor imaging system according to the previous claim 9, in which the multiple sets of spatiotemporal conditions comprise a first set whereby the duration of the time segment of the first set T1 amounts to at least 10 ns, preferably at least 50 ns, and the minimum number of detection signals of the first set M1 is equal to 1; whereby the multiple sets of spatiotemporal conditions comprise a second set whereby the duration of the time segment of the second set T2 amounts to less than 10 ns and the minimum number of detection signals of the second set M2 amounts to at least 2; whereby the multiple sets of spatiotemporal conditions comprise a third set whereby the duration of the time segment of the third set T3 amounts to at least 10 ns, preferably at least 50 ns, and the minimum number of detection signals of the third set M3 is equal to 1.
  11. High-speed sensor imaging system according to any one of the previous claims 1 to 10, whereby the evaluation circuit is configured for defining the macropixels (25) and whereby the detection signals of the detectors (2) are binned together in one macropixel (25), and whereby the spatiotemporal conditions are imposed on the binned detection signals.
  12. High-speed sensor imaging system according to the previous claims 1 to 11, whereby the macropixels (25) can adopt at least two of the following configurations in the matrix form of the array (24): 2x1, 1x2, 2x2, 3x1, 1x3, 3x2, 2x3, 3x3 and/or star-shaped with 1 central detector with every directly adjacent detector.
  13. High-speed sensor imaging system according to any one of the previous claims 1 to 12, whereby the evaluation circuit lets the time segments succeed each other periodically.
  14. High-speed sensor imaging system according to any one of the previous claims 1 to 13, whereby a further spatiotemporal condition is imposed on a confirmed detection signal of a detector in a first macropixel, whereby the further spatiotemporal condition comprises that a confirmed detection signal associated to a detector in a macropixel adjacent to the first macropixel is detected within a prefixed time window of the confirmed detection signal of the detector within the first macropixel; whereby adjacent macropixels are defined as non-overlapping macropixels, said macropixels having at least one detector in common and/or each at least comprising a detector which in the matrix form of the array (24) is adjacent to a detector of the other macropixel of the first and the adjacent macropixel.
  15. High-speed sensor imaging system according to any one of the previous claims 1 to 14, whereby a further spatiotemporal condition is imposed on a confirmed detection signal of a detector in a first macropixel, whereby the further spatiotemporal condition comprises that a confirmed detection signal associated to at least one other detector, preferably at least two other detectors, is detected in the first macropixel within a prefixed time window of the confirmed detection signal of the detector in the first macropixel.
  16. High-speed sensor imaging system according to the previous claims 1 to 15, whereby a first of the multiple sets of spatiotemporal conditions applies macropixels (25) with a first number of detectors, and a second of the multiple sets of spatiotemporal conditions applies macropixels (25) with a second number of detectors, the first and the second number of detectors being different from each other, and preferably whereby a third of the multiple sets of spatiotemporal conditions applies macropixels with a third number of detectors, the third number of detectors being different from the first and the second number of detectors.
  17. High-speed sensor imaging system according to the previous claims 1 to 16, whereby the detectors (2) in a macropixel (25) with K x L detectors (2) are positioned in a square or rectangular configuration, whereby the detectors (2) are clustered in the macropixel (25) by the evaluation circuit in R complementary sub-macropixels from P i x Q i detectors (2), with i = 1 ...R and with P i less than or equal to K/2 and Q i less than or equal to L/2; whereby the detection signals of the detectors (2) are aggregated into sub-macropixel detection signals by the evaluation circuit per sub-macropixel, and the evaluation circuit is configured for imposing the spatiotemporal conditions on the sub-macropixels and the sub-macropixel detection signals of the macropixel (25) instead of on the detectors (2) and the detection signals of the macropixel (25).
  18. High-speed sensor imaging system according to the previous claim 1 to 17, whereby the high-speed sensor system relates to a stacked sensor system.

Description

TECHNICAL DOMAIN The invention relates to a sensor system for imaging under a very high spatial and temporal resolution, whereby an array of single photon detectors (SPDs) is provided, the output signal of which is subjected to evaluation logics for filtering out false positives due to ambient light, thermal noise and other influences. PRIOR ART In prior art, high-speed imaging systems have to contend with a number of requirements and problems. A first one is the accuracy with which incident photons are detected. Increasingly higher demands are made in terms of spatial resolution, resulting in the sensor arrays having increasingly more separate detectors (pixels). This means increased computing power is needed to read all said detectors and to process the output signals into an image. Because the separate pixels always (have to) become smaller, the photosensitivity must also increase, as they have a limited spatial window to capture photons. For this reason very sensitive detectors, such as SPDs or SPADs (single photon - avalanche - detectors), are often considered. A single photon avalanche detector, SPAD, is disclosed in document US 2019/326347 A1. However, said detectors have the inherent disadvantage that the increased photosensitivity also causes unwanted excitations, both due to ambient light and due to thermal noise. In itself such excitations on detector level are difficult to distinguish from 'genuine' detections resulting from the incidence of reflected light that was deliberately emitted by the system to scan a scene. Added to this is the requirement that imaging systems are used in a wide range of conditions, from practically complete darkness, to very bright situations, and also relating to the objects/environment to be captured, varying in terms of reflectiveness and in terms of distance to the imaging system. For this reason it is therefore very difficult to find a single solution that manages to filter out false positives, and can dynamically anticipate the variable circumstances in which the imaging is performed. The purpose of the present invention is to find a solution for at least a number of the aforementioned problems. SUMMARY OF THE INVENTION The invention relates to an improved high-speed sensor imaging system according to claim 1. In further aspects the invention relates to the embodiments according to the other claims 2 to 18. DESCRIPTION OF THE FIGURES Figure 1 shows a process flow of a parallel processing of the detector data under different sets of spatiotemporal conditions, according to an embodiment of the invention.Figures 2A-C show a system according to an embodiment of the invention in a number of separate situations with associated sets of spatiotemporal conditions.Figure 3 shows a circuit implementation of a pixel sensor according to an embodiment of the invention. DETAILED DESCRIPTION Unless otherwise defined, all terms used in the description of the invention, including technical and scientific terms, have the meaning as generally understood by the person skilled in the technical field of the invention. For a better evaluation of the description of the invention, the following terms are explicitly explained. "A", "an" and "the" refer to both the singular and the plural in this document unless the context clearly suggests otherwise. For example, "a segment" means one or more than a segment. When "approximately" or "around" are used in this document for a measurable quantity, a parameter, a duration or moment, and the like, variations of +/-20% or less, preferably +/-10% or less, more preferably +/-5% or less, still more preferably +/-1% or less, and even more preferably +/-0.1% or less than, and of, the quoted value are meant, to the extent that such variations are applicable in the described invention. However, it should be understood that the value of the quantity for which the term "approximately" or "around" is used is itself specifically disclosed. The terms "comprise", "comprising", "consist of", "consisting of", "provided with", "contain", "containing", "include", "including", "hold", "holding" are synonyms and are inclusive or open terms indicating the presence of what follows, without excluding or precluding the presence of other components, characteristics, elements, members, steps, known from or described in the state of the art. Quoting numerical intervals by the end points comprises all integers, fractions, and/or real numbers between the end points, including these end points. In a first aspect the invention relates to a high-speed sensor imaging system, whereby the system comprises one or more light sources, and an array with a plurality of single-photon detectors (or SPDs), said detectors being spatially distributed over the array in a substantial matrix form, preferably at regular intervals from each other, whereby the SPDs are suitable for detecting single photons, and register the detection of the single photon with a detection signal. Preferably, the