Pixel sensor switching by neighbor gate

Abstract

To provide an imaging sensor system (26) having a high detection accuracy.SOLUTION: The imaging sensor system (26) comprises a plurality of pixel sensors (1) and at least one light source. The pixel sensors (1) are grouped into clusters and each pixel sensor (1) has a photodetector (2) and a local control circuit (18). The plurality of pixel sensors (1) in each cluster are configured to output a global detection signal (15) using a local control circuit (18) upon detecting a local detection signal (10) from at least two outputs of the photodetectors (2) in the local cluster. In the imaging sensor system (26), since each detection requires at least two positive outputs of the photodetectors (2) in the local cluster, false positive detections are excluded and a high detection accuracy is obtained.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image sensor system, and more particularly to an image sensor system having high detection accuracy. [Background technology]

[0002] In prior art active imaging scanning, a light beam, typically a laser, is moved over the area to be captured and the position of the beam's incidence is recorded over time via multiple image sensors. By processing the difference in position from different viewpoints (sensors), the effective distance to the object illuminated by the beam can be determined by triangulation. Such measurements capture voxels. The speed at which this processing can be performed, the voxel rate, is on the one hand limited by the speed at which the scan with the light beam is performed, but on the other hand (most strongly) limited by the processing time required by the sensor for the detection of the reflected light beam, especially for background radiation (extraneous light) and thermal noise in general. By specifically addressing this second problem, image formation can be significantly sped up.

[0003] To achieve voxel rates of tens to hundreds of millions of voxels per second, each voxel needs to be recorded in less than 10 ns. Therefore, the sensor also needs to be suitable to operate with a limited photon budget (i.e., the number of impinging photons detected by the sensor that is sufficient for detection), e.g., 10 photons. With a limited processing time, only a limited number of photons can be collected.

[0004] Existing image processing and imaging systems process the light input acquired by the sensor either in parallel for all pixels in the case of a so-called "global shutter" or over time in the case of a "rolling shutter". In either case, a typical imaging system has a gain factor of 10 μV to 1 mV per impinging electron to generate a recordable signal above the minimum detection voltage. It should be noted that the upper limit in the above range can only be guaranteed by very recent imaging devices that have been specially refined to count photons and focus on a very low detection rate. With such a special sensor, a signal of 10 mV for 10 electrons can be generated, which can be read as positive by a particular pixel. To detect a package of impinging photons, a minimum of 10 photons are required to hit the sensor during a time of 10 ns. In the prior art, it has been done so far to limit the exposure time of the sensor to, for example, 10 ns, read the sensor and trigger an event by a threshold voltage (i.e., an actual hit of the reflected beam, not a false positive due to ambient light or thermal noise). The drawback of this approach is that, especially for high-resolution imagers, a bottleneck occurs because the time required to read the sensor dominates the process, typically much longer than 10 ns.

[0005] Another disadvantage is that ambient light or thermal noise in one pixel sensor can result in a false positive, e.g., a false detection.

[0006] Prior art systems, such as those described in WO2019 / 060942A1, feed the individual detector signals into an event circuit for each "group" or cluster, which generates an event trigger when a particular pattern is recognised (perhaps from a list of possible patterns). Upon recognition, the address or identifier of the identified neural feature (pattern) is read out onto a data bus. Alternatively, the address of the SPAD can be read out. However, this has a number of drawbacks as neural feature circuitry is provided for each cluster, creating potential problems.

[0007] Other systems such as US2018 / 0225521A1 use local event intersection detection embedded in pixels, but do not provide an efficient way to determine the location of the event. Furthermore, by using only one "confirmed" pixel per cluster, the event detection is not reliable enough in this prior art.

[0008] The present invention aims to solve at least some of the problems mentioned above. Summary of the Invention

[0009] In a first aspect, the present invention provides a method for producing a composition comprising the steps of: A plurality of pixel sensors (1); At least one light source; 1. An imaging sensor system comprising: the plurality of pixel sensors (1) are grouped into at least one local cluster having at least two pixel sensors (1); Each of the pixel sensors (1) in the local cluster is adjacent to at least one other pixel sensor in the local cluster; The pixel sensors each include a photodetector capable of detecting a single photon impinging thereon and having an output for providing an electrical local detection signal upon detection of a photon; A local control circuit; having the plurality of pixel sensors in the local cluster are configured to output a global detection signal using the local control circuit when the plurality of pixel sensors in the local cluster detect a local detection signal from at least two outputs of the photodetectors in the local cluster; The local control circuit for each of the pixel sensors includes: a local enabling means; and a neighborhood enabling means connected to said local enabling means; having the local detection signal of the pixel sensor is provided to the local enabling means in the pixel sensor; the neighbourhood enabling means of said pixel sensor is supplied with at least one local detection signal of at least one other pixel sensor in said local cluster; the plurality of pixel sensors are configured to output the global detection signal when both the local enabling means and the neighborhood enabling means are triggered. The present invention relates to an imaging sensor system.

[0010] Preferred embodiments of this approach are described in claims 2-10.

[0011] The system comprises a plurality of pixel sensors, the plurality of pixel sensors being grouped into at least one local cluster comprising at least two pixel sensors, each pixel sensor in the local cluster being adjacent to at least one other pixel sensor in the local cluster, the pixel sensors may be aligned in rows and columns, it is an advantage of an embodiment of the present invention that the pixel sensors in one local cluster cooperate or operate or assist each other to obtain a more accurate detection.

[0012] The system further comprises at least one light source.

[0013] Each pixel sensor includes a photodetector capable of detecting a single photon impinging thereon, the single photon being generated by the at least one light source, and the photodetector has an output for providing an electrical local detection signal upon detection of a photon.

[0014] Each pixel sensor further includes a local control circuit configured to output a global detection signal using the local control circuitry in response to detecting local detection signals from at least two outputs of the photodetectors in the local cluster.

[0015] The global detect signals of different local clusters may be aggregated together to form a cluster detect signal, which may be output onto a cluster bus.

[0016] Each of the pixel sensors may be associated with two or more local clusters, and thus it is an advantage of embodiments of the present invention that photons impinging in an area between two neighbouring local clusters can also be detected.

[0017] The local control circuit of each pixel sensor comprises a local enable means and a neighbourhood enable means, the neighbourhood enable means being connected to the local enable means, the local detection signal of the pixel sensor being fed to the local enable means of the pixel sensor, the neighbourhood enable means of the pixel sensor being fed with at least one local detection signal of at least one other pixel sensor in the local cluster, the pixel sensors being arranged to output the global detection signal when both the local enable means and the neighbourhood enable means are triggered.

[0018] It is an advantage of embodiments of the present invention that the local detection signals of the other pixel sensors in the local cluster reduce the possibility of false detection. It is an advantage of embodiments of the present invention that a false detection of one pixel sensor does not result in a global detection signal. It is an advantage of embodiments of the present invention that a more accurate detection is obtained. It is an advantage of embodiments of the present invention that a high accuracy pixel sensor is obtained. It is an advantage of embodiments of the present invention that the influence of ambient light or thermal noise on detection accuracy is reduced.

[0019] The photodetector may be a single photon detector. Alternatively, the photodetector may be a single photon avalanche diode.

[0020] The local enabling means and / or the neighbourhood enabling means may comprise transistors.The local detect signals, the global detect signals and the cluster detect signals are preferably binary signals.

[0021] The system may further comprise a buffer connected to the output of the photodetector of each pixel sensor. The buffer may be a comparator. The buffer may compare the output of the photodetector to a predetermined threshold voltage level. It is an advantage of embodiments of the present invention that the buffer allows the output of the photodetector to be isolated from the local control circuitry. It is an advantage of embodiments of the present invention that the output of the photodetector below the threshold voltage level is not passed to the local control circuitry, thereby preventing any noise or error signals.

[0022] The system may further include a plurality of row buses and a plurality of column buses. The pixel sensors may be arranged into a plurality of rows and a plurality of columns, each row of pixel sensors being connected to and associated with at least one row bus, and each column of pixel sensors being connected to and associated with at least one column bus.

[0023] The global sense signal for each pixel sensor may be connected to an associated row bus and column bus, and the global sense signals for each row may be aggregated together to form a row sense signal, and similarly, the global sense signals for each column may be aggregated together to form a column sense signal.

[0024] The system may further comprise synchronising means adapted to synchronise the row detect signals and the column detect signals.

[0025] The system may have 100 pixel sensors. A row may have up to 50 pixel sensors. And a column may have up to 50 pixel sensors.

[0026] Further advantages of the invention, particularly preferred embodiments, are disclosed in the detailed description that follows. [Brief description of the drawings]

[0027] [Figure 1] FIG. 1 is a circuit diagram of a pixel sensor (1) according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing four sensor clusters (19 to 22) according to an embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic diagram of an image sensor system (26) having pixel sensors (1) connected in rows and columns in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] The present invention relates to an image sensor system.

[0029] Unless otherwise defined, all terms used in disclosing the present invention, including technical and scientific terms, have the meanings commonly understood by one of ordinary skill in the art to which this invention belongs. As a further guide, definitions of terms are included to better understand the teachings of the present invention.

[0030] As used herein, the following terms have the following meanings.

[0031] As used herein, "a," "an," and "the" refer to both singular and plural referents unless the context clearly dictates otherwise. For example, "a contaminant" is , means one or more contaminants.

[0032] As used herein, "about" in reference to a parameter, amount, duration, or other measurable value is intended to include within reasonable variation for practice in the disclosed invention. In the present specification, the term "about" is intended to include a variation of the specified value within + / - 20%, preferably within + / - 10%, more preferably within + / - 5%, even more preferably within + / - 1%, and even more preferably within + / - 0.1% of the specified value. However, it should be understood that the value to which the modifier "about" refers is itself specifically disclosed.

[0033] As used herein, "comprise," "comprising," and "comprises," as well as "comprised of," are synonymous with "include," "including," "includes," or "contain," "containing," or "contains" and are inclusive or open-ended terms that specify the presence of what follows, e.g., components, but do not exclude or preclude the presence of additional, unrecited components, features, elements, materials, or steps that are well known in the art or disclosed therein.

[0034] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within that numerical range, as well as the recited endpoints.

[0035] In a first aspect, the present invention provides a method for producing a composition comprising the steps of: A plurality of pixel sensors (1); At least one light source; 1. An imaging sensor system comprising: the plurality of pixel sensors (1) are grouped into at least one local cluster having at least two pixel sensors (1); Each of the pixel sensors (1) in the local cluster is adjacent to at least one other pixel sensor (1) in the local cluster; The pixel sensors each include a photodetector capable of detecting a single photon impinging thereon and having an output for providing an electrical local detection signal upon detection of a photon; A local control circuit; having the plurality of pixel sensors in the local cluster are configured to output a global detection signal using the local control circuit when detecting a local detection signal from at least two outputs of the photodetectors in the local cluster; The local control circuit for each of the pixel sensors includes: A local enabling means; a neighborhood validation means connected to said local validation means; having the local detection signal of the pixel sensor is provided to the local enabling means in the pixel sensor; the neighbourhood enabling means of said pixel sensor is supplied with at least one local detection signal of at least one other pixel sensor in said local cluster; the plurality of pixel sensors are configured to output the global detection signal when both the local enabling means and the neighborhood enabling means are triggered. The present invention relates to an imaging sensor system.

[0036] In a preferred embodiment, the system includes a plurality of pixel sensors, the plurality of pixel sensors being grouped into at least one local cluster having at least two pixel sensors, each pixel sensor in the local cluster being adjacent to at least one other pixel sensor in the local cluster, e.g., each local cluster having at least two pixel sensors that are adjacent (e.g., in close proximity), and in a more preferred embodiment, each local cluster having at least four pixel sensors that are adjacent to each other, e.g., in close proximity.

[0037] In a preferred embodiment, pixel sensors in one local cluster cooperate with each other. In a more preferred embodiment, adjacent pixel sensors in one local cluster cooperate or work or assist each other. Such cooperation allows for more accurate detection.

[0038] In a preferred embodiment, the system further comprises at least one light source, for example arranged to emit light at a wavelength detectable by the pixel sensor.

[0039] In a preferred embodiment, each pixel sensor includes a photodetector. The photodetector may be arranged in a photodetector-based optical configuration. The photodetector is capable of detecting a single photon impinging thereon. The single photon is generated by the at least one light source with a wavelength suitable for the photodetector. The photodetector has an output for outputting an electrical local detection signal upon detection of a photon. For example, the local detection signal may be represented by a signal including a logic "1" (e.g., detected), while the absence of a local detection signal may be represented by a signal including a logic "0" (e.g., not detected).

[0040] In a preferred embodiment, the photodetector may be a single photon detector, or preferably, the photodetector may be a single photon avalanche diode.

[0041] In a preferred embodiment, the photodetector may be biased, for example, by a voltage divider arrangement, or any other suitable arrangement. For example, the photodetector may be connected at one end to a voltage source and at the other end to a resistor. For example, the voltage source may have a voltage of 3-20V and the resistor may have a resistance of several hundred kilo-ohms. The resistor is connected to a reference level, preferably to ground level, for example 0V. Those skilled in the art will understand that these values ​​depend on the design of the circuit and the breakdown voltage of the single photon avalanche diode. The output of the photodetector (for example, in this case having a voltage level equal to the voltage dropped across the resistor) is between the voltage of the voltage source and the ground level.

[0042] In a preferred embodiment, each pixel sensor further comprises a local control circuit, the pixel sensors in the local cluster being configured to output a global detection signal using the local control circuit when the pixel sensors detect local detection signals from at least two outputs of the photodetectors in the local cluster. For example, in a local cluster having two adjacent pixel sensors, the local control circuit outputs a global detection signal when it detects two local detection signals from the two pixel sensors. For example, one global detection signal is output for each pixel sensor.

[0043] In a preferred embodiment, the global detection signals of different local clusters may be aggregated together to form a cluster detection signal, which may be output to a cluster bus, e.g., to obtain information about in which local cluster there was a detection.

[0044] In a preferred embodiment, the bus is a data highway, for example data from more than one pixel sensor may be loaded onto the bus such that the receiver can ascertain which data belongs to which pixel sensor.

[0045] In a preferred embodiment, each of the pixel sensors may be associated with two or more local clusters. For example, a system having three pixel sensors arranged in a linear row may have two local clusters, one with the two pixel sensors from the left and one with the two pixel sensors from the right. In this case, the center pixel sensor is part of both local clusters. Having pixel sensors associated with two or more local clusters is advantageous when the required detection is located in the middle of two local clusters. For example, a plurality of pixel sensors, at least two pixel sensors located around each other, may be considered as one local cluster. For example, one pixel sensor and one pixel sensor adjacent to it may be considered as one local cluster.

[0046] In a preferred embodiment, the local control circuitry of each pixel sensor may comprise local enable means and neighbourhood enable means. A local enable means is connected to the pixel sensor, for example in series, or both are connected to a logic gate, for example an AND gate. The local detection signal of the pixel sensor is supplied to the local enable means of the pixel sensor. A neighbourhood enable means of the pixel sensor is supplied with at least one local detection signal of at least one other pixel sensor in the local cluster. The pixel sensors are configured to output the global detection signal, for example when both the local enable means and the neighbourhood enable means are triggered in at least two pixel sensors in the local cluster. For example, a pixel sensor whose local enable means and neighbourhood enable means are triggered may generate a global detection signal.

[0047] In a preferred embodiment, the number of local detection signals required to trigger the neighborhood enabling means of a pixel sensor may be variable. This depends on the time difference in receiving a photon at different pixel sensors in one local cluster. For example, in one scenario, eight neighboring pixel sensors in one local cluster may be detected. may require local detection signals of more than half the pixel sensors in the local cluster. For example, eight local detection signals of the eight neighboring pixel sensors may be required if the photon is not received by the one pixel sensor and the eight neighboring pixel sensors at the same time or is received with a large time difference. For example, in another scenario, a one pixel sensor having eight neighboring pixel sensors in a local cluster may require less than half the local detection signals in the local cluster. For example, one local detection signal of the one neighboring pixel sensor may be required if the photon is received by both the one pixel sensor and one neighboring pixel sensor at the same time. In another example, if a photon is received by the one pixel sensor and the multiple neighboring pixel sensors with a time delay (e.g., a time delay between the one pixel sensor and one neighboring pixel sensor), the time delay may be used to set the number of local detection signals required to trigger the neighborhood enabling means.

[0048] In a preferred embodiment, the local detection signal of one pixel sensor and the local detection signal of the neighbouring pixel sensor used to trigger the neighbourhood enabling means are not generated at the same time. For example, the local detection signal of a first pixel sensor is generated at time T1 as a result of a photon detection in the first pixel sensor. The local detection signal of the neighbouring pixel sensor may be generated at time T1+D, where D is a delay. The delay may occur, for example, if the light source moves too slowly. It is possible that the local detection signal of the first pixel sensor ends before the local detection signal of the neighbouring pixel sensor is generated due to a photon not being detected. A predetermined value of the delay D may be required to determine whether the detection is a false positive or not.

[0049] In a preferred embodiment, a neighborhood cluster thus covers multiple pixels in the neighborhood and can be triggered by a sufficiently large optical signal by triggering at least one pixel in the neighborhood within a short time window.

[0050] In another preferred embodiment, the neighboring clusters can thus be triggered by an optical signal having a momentary special footprint, which may be one pixel or smaller, spatially moving within a set time window D to sequentially trigger neighboring pixels within the time window D, thereby triggering the neighboring clusters.

[0051] In a preferred embodiment, for example, the neighborhood validation means of each pixel sensor includes a neighborhood validation means for validating one other pixel sensor in the local cluster, more preferably for more than half of the neighboring pixel sensors in the local cluster, and most preferably for all of the neighboring pixel sensors in the local cluster. The local detection signals of the neighboring pixel sensors are provided.

[0052] In a preferred embodiment, a local cluster may have at least two pixel sensors, a first pixel sensor and a second pixel sensor. For example, the pixel sensors are adjacent or close to each other. When there is an impinging photon in the local cluster, the local enabling means of the first pixel sensor is triggered by a local detection signal of the photodetector of the first pixel sensor. Similarly, the local enabling means of the second pixel sensor is triggered by a local detection signal of the photodetector of the second pixel sensor. The local detection signal of the second pixel sensor triggers the neighborhood enabling means of the first pixel sensor. Similarly, the local detection signal of the first pixel sensor triggers the neighborhood enabling means of the second pixel sensor. For example, when the local enabling means of both pixel sensors are triggered, the neighborhood enabling means of both pixel sensors are also triggered, so that a global detection signal is output by the two pixel sensors. The global detection signal indicates that there has been a photon impinging on the photodetectors of at least two pixel sensors in a local cluster (e.g., close to each other).

[0053] In a preferred embodiment, for example, the global detection signal indicates that there was a photon that hit the photodetector of a pixel sensor that is adjacent or close to each other. This is useful for eliminating false detections. That is, a false detection is more likely to occur as a result of a false detection of one detector, and less likely to occur as a result of a false detection of two or more detectors, e.g., a group of detectors, that cooperate and are close to each other. Detection based on two or more pixel sensors is more reliable and accurate than detection based on only one pixel sensor. For example, detection based on two pixel sensors reduces the possibility of a false detection. A false detection may be the result of ambient light or thermal noise, but is less likely to occur with two or more adjacent pixel sensors. If a false detection occurs (for example, a false detection is detected only in one pixel sensor, but not in its adjacent or nearby pixel sensors), no global detection signal is output.

[0054] In a preferred embodiment, the term "triggering" may be interpreted as receiving a high voltage signal, e.g. a logic "1" signal, e.g. a signal representing an ON state. For example, triggering the neighborhood enabling means may mean receiving a e.g. logic "1" signal at the neighborhood enabling means.

[0055] In a preferred embodiment, pixel sensors associated with more than one local cluster, e.g. two local clusters, may have their local detection signals supplied to neighbourhood enabling means of pixel sensors (e.g. two pixel sensors) belonging to different local clusters.

[0056] In a preferred embodiment, the local detection signals and the global detection signals, the cluster detection signals, or any other signals in the system, are preferably binary signals.

[0057] In a preferred embodiment, the local enabling means and the neighbourhood enabling means may comprise transistors, preferably NMOS transistors, each of which may operate as a switch.

[0058] In a preferred embodiment, the output of the photodetector is a logic "1" when a photon is detected at the photodetector and a logic "0" when no photon is detected at the photodetector.

[0059] In a preferred embodiment, the local detection signal is either a logical "1" or a logical "0". For example, a transistor of the local enabling means is ON when the local sense signal is a logic "1" and is OFF when the local sense signal is a logic "0".

[0060] In a preferred embodiment, for example, a transistor of the neighborhood enablement means is ON when the local detection signal supplied from another adjacent pixel sensor is logic "1", and is OFF when the local detection signal is logic "0".

[0061] In a preferred embodiment, for example, when the neighborhood enabling means of one first pixel sensor is triggered by the local detection signal of at least one adjacent pixel sensor, a transistor of the neighborhood enabling means is turned ON. Similarly, the local detection signal of the first pixel sensor triggers a transistor of the neighborhood enabling means of the at least one adjacent pixel sensor.

[0062] In a preferred embodiment, the neighborhood enable means and the local enable means are connected, e.g., they are connected in series. For example, when both the local enable means and the neighborhood enable means are triggered, two, e.g., transistors or, e.g., switches, of the local enable means and the neighborhood enable means are turned on, and a global detection signal is output by the pixel sensor. For example, adjacent pixel sensors are supplied with each other's local detection signals to their respective neighborhood enable means, so that the same global detection signal is output by the adjacent pixel sensors.

[0063] In a preferred embodiment, the neighborhood enabling means and the local enabling means may comprise logic gates, for example AND gates. For example, if the local sense signal is logic "1" and the local sense signal of an adjacent pixel sensor is logic "1", the output of the AND gate will be logic "1" and a global sense signal will be generated at each of the two pixel sensors. The logic gates may also be replaced by two transistors acting as switches, or two switches. For example, one transistor of the local enabling means is connected in series with one transistor of the neighborhood enabling means, so that when both transistors are switched ON, a current can flow through the two transistors.

[0064] In a preferred embodiment, the neighborhood enabling means and the local enabling means may comprise logic gates, for example AND gates. For example, if the local sense signal is logic "1" and two or more local sense signals of two or more adjacent pixel sensors are logic "1", the output of the AND gate will be logic "1" and a global sense signal will be generated at each of the three or more pixel sensors. The logic gates may also be replaced by three transistors acting as switches, or three switches. For example, one transistor of the local enabling means is connected in series with two series-connected transistors of the neighborhood enabling means, so that when all transistors are switched ON, a current can flow through the three transistors. A person skilled in the art will understand that different circuit configurations are possible.

[0065] In a preferred embodiment, each bus may be connected to a voltage bias. For example, when the local enable means and the neighborhood enable means are triggered, e.g. when the transistor or switch is ON, a current flows through the local enable means and the neighborhood enable means. This current flow is then sensed, e.g. by a sense amplifier, e.g. at the other end of the bus. In another preferred embodiment, the bus may be pre-charged. For example, when the local enable means and the neighborhood enable means are triggered, e.g. when the transistor or switch is ON, a charge in the bus is discharged through the local enable means and the neighborhood enable means. This discharge is then sensed, e.g. by a sense amplifier, e.g. at the other end of the bus.

[0066] In a preferred embodiment, the number of neighbouring pixel sensors required to enable the generation of a global detection signal may for example be designed according to design requirements and may have different circuit implementations depending on said number.

[0067] In a preferred embodiment, the system may further comprise a buffer connected to the output of the photodetector of each pixel sensor. Preferably, the buffer may be a comparator. For example, the buffer may compare the output of the photodetector with a predetermined threshold voltage level. Preferably, the threshold voltage level is between 0.5 and 2V, more preferably between 0.6 and 1V. The buffer may be useful for isolating the photodetector from the local control circuitry. The buffer may further be useful for preventing signals with voltages below the threshold voltage level from passing to the local control circuitry.

[0068] In a preferred embodiment, the system may further comprise a plurality of row buses and a plurality of column buses, each row of pixel sensors being connected to and associated with at least one row bus, and similarly, each column of pixel sensors being connected to and associated with at least one column bus.

[0069] In a preferred embodiment, the local enable means may comprise two transistors, for example one of which is connected to the row bus and the other one to the column bus, and the output of the photodetector of each pixel sensor is connected to the row bus via one transistor in the local enable means and to the column bus via the other transistor in the local enable means.

[0070] In a preferred embodiment, multiple pixel sensors in adjacent rows and columns may be in one cluster. For example, a pixel sensor in row x and column y may be in one cluster with another pixel sensor in row x+1 and column y. For example, all pixel sensors included in row x-1, column y-1 to row x+1, column y+1 may be in one cluster. For example, the pixel sensors may be arranged in a matrix configuration.

[0071] In a preferred embodiment, the global detection signal for each pixel sensor may be provided to an associated row bus and column bus. The global detection signals for each row may be aggregated together to form a row detection signal, e.g. the row detection signal comprises the global detection signal for each pixel sensor in the row. Similarly, the global detection signals for each column may be aggregated together to form a column detection signal, e.g. the column detection signal comprises the global detection signal for each pixel sensor in the column.

[0072] In a preferred embodiment, the system may further comprise synchronization means for synchronising the row detect signals and the column detect signals, e.g. synchronising row detect signals of different rows and synchronising column detect signals of different columns.

[0073] In a preferred embodiment, the system may have 100 pixel sensors. For example, a row may have up to 50 pixel sensors. Further, for example, a column may have up to 50 pixel sensors.

[0074] Further features and advantages of embodiments of the invention will be described with reference to the figures. The invention is not limited to the specific embodiments shown in these figures or described by way of example. However, it should be noted that the present invention is limited only by the scope of the claims.

[0075] 1 is a circuit implementation diagram of a pixel sensor (1). The pixel sensor (1) comprises a photodetector (2), such as a single-photon detector or a single-photon avalanche diode. The photodetector (2) is capable of detecting a single photon (3) impinging thereon.

[0076] The photodetector (2) is biased by a voltage source (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.

[0077] 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).

[0078] The voltage drop (7) is compared with a predefined threshold voltage level (8) via a comparator (9). If the voltage drop (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 the case of "detection", a logic "1" is generated as the output of the comparator, and in the case of "non-detection", a logic "0" is generated as the output of the comparator.

[0079] Each pixel sensor (1) has a local control circuit (18). The comparator (9) acts as a buffer between the photodetector (2) and the local control circuit (18). The local control circuit (18) has a local enabling means (11) and a neighborhood enabling means (12).

[0080] The control circuitry, or parts thereof, may be physically located in different layers of the sensor system, for example the pixel sensors (1) of the sensing array may be located in a first semiconductor layer and the control circuitry (18) for each pixel sensor (1) in the array may be located in a second semiconductor layer, i.e. forming a so-called stacked pixel sensor solution structure.

[0081] The local detect signal (10) is fed to a local enable means (11). The local enable means (11) comprises two NMOS transistors. However, other transistor types or configurations may be used. The local detect signal (10) is fed to the gates 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 gate of a transistor of the local enable means (11), the local enable means (11) is triggered. In this case, the transistor acts as a switch, and receiving a logic "1" at the transistor turns the switch ON, e.g. short circuiting.

[0082] The local enabling means (11) is connected to the neighbourhood enabling means (12). In this case, each transistor of the local enabling means (11) is connected to said neighbourhood enabling means. The neighbourhood enabling means (12) comprises at least one transistor, in this embodiment three transistors with gates (13', 13", 13'"'). The gates (13', 13", 13'"') of the three transistors are connected to the local detection signals of 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. Upon receiving at least one local detection signal from one neighbouring pixel sensor at one gate, for example (13'), the neighbourhood enabling means is triggered. This means in this case that if the gate (13') has a logic "1", the transistor, now acting as a switch, is ON, e.g. short-circuited. When both the local enable means and the neighborhood enable means are triggered, i.e. when a transistor in the local enable means is operating as a short and one transistor in the neighborhood enable means is operating as a short, a global detect signal (15) is output to a row bus (16) and a column bus (17). The global detect signals of different pixel sensors in the row bus (16) are aggregated to form a row detect signal. The global detect signals of different pixel sensors in the column bus (17) are aggregated to form a column detect signal.

[0083] The local control circuit (18) in this example acts as an AND gate, i.e. when the local enabling means (11) and the neighborhood enabling means (12) are triggered, a global detection signal (15) is generated.

[0084] Two implementations are envisaged. In a first implementation, each bus (16, 17) may be connected to a voltage bias. For example, when the local enable means (11) and the neighborhood enable means (12) are triggered, a current flows through the local enable means (11) and the neighborhood enable means (12). This current flow is then sensed, for example by a sense amplifier, for example at the other end of the bus. This current is also referred to in this case as the global sense signal (15).

[0085] In a second implementation, each bus (16, 17) may be pre-charged. For example, when the local enable means (11) and the neighborhood enable means (12) are triggered, the charge in the bus is discharged via the local enable means (11) and the neighborhood enable means (12). This discharge is then sensed, for example, by a sense amplifier, for example, at the other end of the bus. This discharge is also referred to in this case as the global sense signal (15).

[0086] Figure 2 shows four clusters of pixel sensors, each with its own coordinates, for example the first pixel cluster (19) has a first pixel sensor (23) at position (i,j) and eight neighbouring pixel sensors.

[0087] The neighboring pixel sensors include an image sensor (24) having a local detection signal, e.g., positive detection, e.g., a local detection signal of logic "1", and an image sensor (25) having no local detection signal, e.g., negative detection (e.g., "not detected"), e.g., a local detection signal of logic "0". In this case, a first pixel cluster (19) has one positive detection among its neighboring pixel sensors. Similarly, a second pixel cluster (20) has three positive detections among its neighboring pixel sensors, a third pixel cluster (21) has two positive detections among its neighboring pixel sensors, and a fourth pixel cluster (22) has no positive detections.

[0088] For example, if the first pixel sensor (23) in the pixel cluster (19-22) is configured to output a global detection signal (15) when there is a positive detection in the first pixel sensor (23) and one neighboring pixel sensor, this will result in the first pixel sensor and the neighboring pixel sensors in the pixel clusters (19, 20, and 21) outputting a global detection signal (15), e.g., a global detection signal of logic "1". However, if the first pixel sensor (23) in the pixel cluster (19-22) is configured to output a global detection signal (15) when there is a positive detection in the first pixel sensor (23) and two neighboring pixel sensors, this will result in the first pixel sensor and the neighboring pixel sensors in the pixel clusters (20 and 21) outputting a global detection signal (15), e.g., a positive detection. The number of neighboring pixel sensors required for the detection of the cluster as a whole to be considered a positive detection depends on design requirements.

[0089] 3 is a schematic diagram of an image sensor system (26) having pixel sensors (1) connected in rows and columns. The pixel sensors (1) of each row are connected to two row buses (16, 16') and two column buses (17, 17'). The pixel sensors (1) output a global detection signal (15), which is a binary signal.

[0090] Three cases are shown in FIG. 3. In the first case, a photon hits more than one pixel sensor at the same time. In this case, it hits four pixel sensors at the same time. The first circle (27) shows the area where the photon hits. In this case, more than one pixel sensor (1) senses the photon, so the detection is correct. Each pixel sensor has a local detection signal, for example of logic "1". The local detection signal of each pixel sensor is also connected to and triggers the neighborhood enabling means of neighbouring or adjacent pixel sensors. For example, transistors belonging to the local enabling means and the neighborhood enabling means are triggered in the four pixel sensors. This causes a global detection signal of logic "1" to be generated by each pixel sensor, which is output to the associated row bus and column bus.

[0091] In the second and third cases, the second circle (28) indicates an area where a photon detection is suspect. In this case, the detection is a false positive because none of the neighboring pixel sensors sense such a detection. Therefore, the neighborhood enablement means is not triggered and thus no global detection signal is generated or a global detection signal of logic "0" is output to the associated row and column buses. This false positive may be the result of ambient light or thermal noise.

[0092] In the above description, a specific embodiment of the present invention is described in detail. However, no matter how detailed the above description is in the text, it will be apparent that the present invention can be applied in many ways. The use of a specific term to describe a specific feature or aspect of the present invention should not be interpreted as meaning that the term is redefined herein as being limited to the specific feature or aspect of the present invention to which it pertains.

Claims

1. A plurality of pixel sensors (1); At least one light source; An imaging sensor system (26) having The plurality of pixel sensors (1) are grouped into at least one local cluster having at least two pixel sensors (1); Each of the pixel sensors (1) in the local cluster is adjacent to at least one other pixel sensor in the local cluster; The pixel sensors each include a photodetector (2) capable of detecting a single photon (3) impinging thereon and having an output for providing an electrical local detection signal (1) upon detection of a photon (2); A local control circuit (18); having the plurality of pixel sensors (1) in the local cluster are configured to output a global detection signal (15) using the local control circuit when a local detection signal (10) is detected from at least two outputs of the photodetectors (2) in the local cluster; The local control circuit (18) for each of the pixel sensors comprises: A local validation means (11); a neighborhood validation means (12) connected to the local validation means (11); having The local detection signal (10) of the pixel sensor is fed to the local enabling means (11) in the pixel sensor (1); The neighbourhood validation means (12) of the pixel sensor is supplied with at least one local detection signal (10) of at least one other pixel sensor in the local cluster; The plurality of pixel sensors (1) generate the global detection signal (15) when both the local enabling means (11) and the neighborhood enabling means (12) are triggered. The system is configured to: The imaging sensor system (26) further comprises a plurality of row buses (16, 16') and a plurality of column buses (17, 17'); The pixel sensors (1) are aligned in a plurality of rows and a plurality of columns; Each pixel sensor row is connected to and associated with at least one column bus (17); the global detection signal (15) of each of the plurality of pixel sensors (1) is output to the associated row bus (16, 16') and column bus (17, 17'); An imaging sensor system (26).

2. 2. The imaging sensor system (26) of claim 1, the plurality of pixel sensors (1) in the local cluster are configured to output a global detection signal (15) upon detecting a local detection signal (1) from at least two outputs of the photodetectors (2) in the local cluster within a predetermined time delay; An imaging sensor system (26).

3. 3. The imaging sensor system (26) of claim 1 or 2, the photodetector (2) being a single-photon detector or a single-photon avalanche diode; An imaging sensor system (26).

4. An imaging sensor system (26) according to any one of claims 1 to 3, The local validation means (11) and / or the neighborhood validation means (12) having a transistor, preferably an NMOS transistor, An imaging sensor system (26).

5. An imaging sensor system (26) according to any one of claims 1 to 4, Each of the pixel sensors (1) further comprises a buffer (9) connected to an output of the photodetector of the pixel sensor, the buffer (9) comparing the output of the photodetector with a predetermined threshold voltage level. An imaging sensor system (26).

6. An imaging sensor system (26) according to any one of claims 1 to 5, The global detection signals (15) of different local clusters are aggregated together to form a cluster detection signal. An imaging sensor system (26).

7. An imaging sensor system (26) according to any one of claims 1 to 6, the local detection signal (10) and / or the global detection signal (15) are binary signals, An imaging sensor system (26).

8. 7. The imaging sensor system (26) of claim 6, the cluster detection signal is a binary signal; An imaging sensor system (26).

9. An imaging sensor system (26) according to any one of claims 1 to 8, each of the plurality of pixel sensors is associated with two or more local clusters; An imaging sensor system (26).

10. An imaging sensor system (26) according to any one of claims 1 to 9, the global detection signals (15) for each row are summed together to form a row detection signal, and the global detection signals (15) for each column are summed together to form a column detection signal; An imaging sensor system (26).

11. An imaging sensor system (26) according to any one of claims 1 to 10, the imaging sensor system (26) has up to 100 pixel sensors (1), or preferably up to 50 pixel sensors (1) connected in one row or in one column; An imaging sensor system (26).

12. 11. The imaging sensor system (26) of claim 10, the imaging sensor system (26) further comprising synchronization means for synchronizing the row detection signals and the column detection signals; An imaging sensor system (26).

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