Imaging device and imaging method

Abstract

An improved imaging device and an improved method are provided. [Solution] The present disclosure provides an imaging device including an array of photosensitive elements and a first counter for counting photon detection events received from a first group of the photosensitive elements, where in a first operating mode the first counter is connected to a first subgroup of the first group of photosensitive elements, and in a second operating mode the first counter is connected to a second subgroup of the first group of photosensitive elements.

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates generally to imaging devices and methods. [Background technology]

[0002] Known types of digital image sensors are the charge coupled device (CCD) and the complementary metal oxide semiconductor (CMOS) active pixel sensor.

[0003] In recent years, image sensors have emerged that include arrays of photosensitive elements based on single photon avalanche diodes (SPADs).

[0004] In a photosensitive element, a SPAD, a single free charge carrier injected by a single photon can cause an avalanche of free charge carriers, making the single photon detectable.

[0005] A counter in the photosensitive element can count the avalanches and thus provide the number of detected photons. Summary of the Invention [Problem to be solved by the invention]

[0006] While the art relates to imaging devices, it would generally be desirable to provide improved imaging devices and methods. [Means for solving the problem]

[0007] According to a first aspect, the present disclosure provides an imaging device comprising an array of photosensitive elements and a first counter for counting photon detection events received from a first group of photosensitive elements, wherein in a first operating mode, the first counter is connected to a first subgroup of the first group of photosensitive elements and wherein in a second operating mode, the first counter is connected to a second subgroup of the first group of photosensitive elements.

[0008] According to a second aspect, the present disclosure provides a method of operating an imaging device, comprising counting photon detection events received from a first group of photosensitive elements of an array of photosensitive elements with a first counter, connecting the first counter to a first subgroup of the first group of photosensitive elements in a first operating mode, and connecting the first counter to a second subgroup of the first group of photosensitive elements in a second operating mode.

[0009] Further aspects are set out in the dependent claims, the drawings and the following description. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram of an imaging device according to an embodiment. [Diagram 2] 1 shows a block diagram of an array of photosensitive elements and a counter in a top view, according to an embodiment; [Diagram 3] FIG. 11 is a block diagram of a counter read sequence in four operating modes according to an embodiment. [Figure 4] 1 illustrates a block diagram of a read sequence for four counters in four operating modes according to an embodiment. [Diagram 5] FIG. 2 is a block diagram of bit usage in the image sensor of the present embodiment based on a SPAD. [Figure 6] FIG. 2 is a block diagram of bit usage in a SPAD-based image sensor according to an embodiment. [Figure 7] FIG. 2 is a diagram illustrating a basic operation of the imaging device according to the embodiment. [Figure 8] FIG. 2 is a diagram showing a circuit configuration according to an embodiment. [Figure 9] 2 is a diagram of image data generated by an imaging device according to an embodiment. [Figure 10] FIG. 2 is a block diagram of the readout principle in an array of photosensitive elements for color coding according to an embodiment; [Figure 11] FIG. 13 is a block diagram of 3×3 binning in an array of photosensitive elements according to an embodiment. [Figure 12] 1 is a flow diagram of a method of operating an imaging device according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0012] Before proceeding to a detailed description of the embodiment with reference to FIG. 1, a general description will be given.

[0013] As indicated at the beginning, known types of digital image sensors are the Charge Coupled Device (CCD) and the Complementary Metal Oxide Semiconductor (CMOS) active pixel sensor. Recently, image sensors have emerged that include an array of photosensitive elements based on Single Photon Avalanche Diodes (SPADs).

[0014] In a photosensitive element, a SPAD, a single free charge carrier injected by a single photon can cause an avalanche of free charge carriers, making the single photon detectable.

[0015] Each SPAD-based photosensitive element has a counter that counts the avalanches and can therefore provide the number of detected photons.

[0016] In some embodiments, SPAD-based photosensitive elements require a dedicated readout counter with enough bits for high image depth, and the number of bits required dictates the minimum size of the counter, so that each counter must be placed below its corresponding SPAD-based photosensitive element, such that each photosensitive element occupies a space at least corresponding to the minimum size of the counter.

[0017] Thus, the density of the photosensitive elements, and therefore the image resolution, is potentially limited by the size of the counter.

[0018] In some embodiments, it is desirable to reduce the size of the photosensitive elements and the space occupied per photosensitive element in a SPAD-based imaging device in order to increase the density of the SPAD-based photosensitive elements and therefore the resolution of the images produced by the imaging device.

[0019] Consequently, some embodiments of the present invention relate to an imaging device comprising an array of photosensitive elements and a first counter for counting photon detection events received from a first group of photosensitive elements, wherein in a first operating mode, the first counter is connected to a first subgroup of the first group of photosensitive elements and wherein in a second operating mode, the first counter is connected to a second subgroup of the first group of photosensitive elements.

[0020] By counting the photon detection events received from the first group of photosensitive elements with the first counter, the photosensitive elements of the first group of photosensitive elements can share the first counter, which may eliminate the need for a dedicated counter for each photosensitive element, and therefore may occupy less space per photosensitive element than the first counter, resulting in a higher density of the photosensitive elements and higher image resolution.

[0021] Connecting the first counter to the first subgroup (or, equivalently, connecting the first subgroup to the first counter) may include establishing an electrical connection between the first counter and each photosensitive element of the first subgroup such that an electrical signal indicative of a photon detection event in any one of the photosensitive elements of the first subgroup is provided to the first counter.

[0022] Similarly, connecting the first counter to the second subgroup (or, equivalently, connecting the second subgroup to the first counter) may include establishing an electrical connection between the first counter and each photosensitive element of the second subgroup such that an electrical signal indicative of a photon detection event in any one of the photosensitive elements of the second subgroup is provided to the first counter.

[0023] By connecting the first counter to different subgroups of the first group of photosensitive elements in different operating modes, the first counter can count photon detection events from each photosensitive element of the corresponding subgroup in each respective operating mode, and the area where photons are detected can be increased, which can result in a higher number of detected photons for a single photosensitive element. The number of photons missed during SPAD recovery after a photon detection event can also be reduced compared to a single photosensitive element, since during SPAD recovery of one photosensitive element of a subgroup, the other photosensitive element(s) of the subgroup can still be sensitive to incident photons. Furthermore, by providing an overlap between the subgroups, an image resolution equal to or smaller than the subgroup size can be achieved.

[0024] The first subgroup may be a contiguous subset of the first group of photosensitive elements. Similarly, the second subgroup may be a contiguous subset of the first group of photosensitive elements.

[0025] The values ​​counted by the first counter in the first operating mode and the second operating mode, i.e., the number of photon detection events in the first subgroup and the second subgroup, respectively, can be associated with different pixels of an image generated by the imaging device.

[0026] In some embodiments, the first counter is disposed in a first semiconductor layer and the array of photosensitive elements is disposed in a second semiconductor layer, the first counter overlapping an area in which the first subgroup is disposed.

[0027] For example, the first semiconductor layer may be provided on the side opposite to the light incident side of the second semiconductor layer.

[0028] In this manner, by locating the first counter close to the first group of photosensitive elements, it may be possible to reduce the parasitic capacitance of the wiring connecting the first counter and the first group of photosensitive elements, thereby reducing the latency in counting photon detection events from the first group of photosensitive elements.

[0029] By providing the first counter in a semiconductor layer separate from the array of photosensitive elements, a larger area of ​​the second semiconductor layer can be utilized (for the SPAD of the photosensitive elements), and by covering a larger area with the SPAD, the light sensitivity of the array of photosensitive elements can be improved.

[0030] In some embodiments, the first semiconductor layer is provided on a first chip and the second semiconductor layer is provided on a second chip.

[0031] For example, the first chip and the second chip may be separate semiconductor chips. The first chip and the second chip may be fabricated separately and then stacked together. The first counter may be directly coupled to the first group of light sensitive elements, for example via solder bumps.

[0032] In some embodiments, each subgroup of the first group of photosensitive elements is configured to be individually connected to the first counter.

[0033] For example, the configuration of the first group of photosensitive elements may enable each subgroup of the first group of photosensitive elements to be connected to the first counter without connecting photosensitive elements that are not included in the corresponding subgroup to the first counter.

[0034] In this manner, photon detection events can be counted separately, for example sequentially, for each subgroup of the first group of photosensitive elements by the first counter, such that a pixel of an image generated by the imaging device can be based on the number of photon detection events for a single subgroup of the first group of photosensitive elements.

[0035] In some embodiments, the imaging device further includes an image data generation unit configured to generate image data, wherein a first pixel of the image data is based on a number of photon detection events of a first subgroup in a first operating mode, and a second pixel of the image data is based on a number of photon detection events of a second subgroup in a second operating mode.

[0036] The image data may represent an image generated by the imaging device based on photons detected by the array of photosensitive elements. A value of a pixel of the image may be based on the number of photon detection events in a single subgroup of the first group of photosensitive elements counted in a corresponding operation mode. In some embodiments, the imaging device further comprises a second counter for counting photon detection events received from a second group of photosensitive elements of the array of photosensitive elements, where in the first operation mode, the second counter is connected to a third subgroup of the second group of photosensitive elements, and in the second operation mode, the second counter is connected to a fourth subgroup of the second group of photosensitive elements, where the third subgroup of the second group of photosensitive elements overlaps with the second subgroup of the first group of photosensitive elements in at least one photosensitive element.

[0037] For example, at least one photosensitive element may be included in both the second subgroup of the first group of photosensitive elements and the third subgroup of the second group of photosensitive elements.

[0038] The overlapping subgroups may enable image resolution in an image produced by the imaging device that is finer than the size of the subgroups of the first or second groups of photosensitive elements.

[0039] The overlap may allow acquisition of image data by pixel shifting.

[0040] In some embodiments, the first subgroup and the second subgroup each include at least two photosensitive elements, and the first subgroup and the second subgroup overlap at least one photosensitive element.

[0041] As mentioned above, overlapping subgroups may allow pixel shifting to obtain higher image resolution than can be obtained with non-overlapping photosensitive elements.

[0042] In some embodiments, each of the first subgroup and the second subgroup includes at least two rows of photosensitive elements and at least two columns of photosensitive elements.

[0043] The first subgroups and the second subgroups may be rectangular, i.e., each one of the first subgroups and the second subgroups may include those photosensitive elements of the array of photosensitive elements that are included in both a consecutive set of rows and a consecutive set of columns of the array of photosensitive elements.

[0044] In some embodiments, each of the first subgroup and the second subgroup is a square.

[0045] For example, the number of rows of photosensitive elements included in the first or second subgroup may be equal to the number of columns of photosensitive elements included in the respective first or second subgroup. The square shape of the first and second subgroups may, for example, correspond to the shape of a pixel in an image generated by the imaging device.

[0046] In some embodiments, the first subgroup and the second subgroup each include two rows and two columns of photosensitive elements.

[0047] For example, a 2x2 binning of the photosensitive elements can be performed.

[0048] In some embodiments, each of the first subgroup and the second subgroup includes three rows and three columns of photosensitive elements.

[0049] For example, a 3x3 binning of the photosensitive elements can be performed.

[0050] In some embodiments, each photosensitive element of the first group of photosensitive elements includes a first sub-element for detecting light of a first color and a second sub-element for detecting light of a second color, and the first counter includes a first color counter for counting photon detection events received from the first sub-element and a second color counter for counting photon detection events received from the second sub-element.

[0051] For example, a color filter may be provided in front of the SPADs of the first and second sub-elements of the photosensitive elements of the first group of photosensitive elements such that only light having a predetermined color reaches the respective SPAD. The color filter may for example comprise a bandpass filter configured to transmit light of a predetermined wavelength interval, a longpass filter configured to transmit light of wavelengths not shorter than a predetermined cut-on wavelength, or a shortpass filter configured to transmit light of wavelengths not longer than a predetermined cut-off wavelength.

[0052] For example, instead of or in addition to providing a color filter in front of the SPADs of the first and second sub-elements of the photosensitive element, the material of the depletion region in the SPADs of the first and / or second sub-elements can be selected such that ionization (i.e., generation of free charge carriers) is particularly sensitive to a particular wavelength interval.

[0053] For example, a first sub-element may be configured to detect red light, e.g. photons having an average wavelength between 630 and 700 nanometers, a second sub-element may be configured to detect green light, e.g. photons having an average wavelength between 500 and 560 nanometers, and a third sub-element of the photosensitive element may be configured to detect blue light, e.g. photons having an average wavelength between 450 and 475 nanometers. The present disclosure is not limited to the mentioned wavelength values ​​and a person skilled in the art may find various combinations of wavelength intervals detected by different sub-elements of the photosensitive element.

[0054] Each color counter of the first counter may include a separate register for storing the number of detected photons. For example, the first color counter may count photon detection events from a first sub-element of a photosensitive element of a first group of photosensitive elements and store the number of counted photon detection events in its separate register. Similarly, the second color counter may count photon detection events from a second sub-element of a photosensitive element of the first group of photosensitive elements and store the number of counted photon detection events in its other register.

[0055] In this manner, the imaging device can generate a color image, for example a red-green-blue (RGB) image, based on photon detection events from different sub-elements of the photosensitive element counted by corresponding color counters of the first counter.

[0056] In some embodiments, all subgroups of the first group of photosensitive elements include the same number of photosensitive elements, and each subgroup of the first group of photosensitive elements includes fewer photosensitive elements than the first group of photosensitive elements.

[0057] For example, each subgroup of the first group of photosensitive elements may be rectangular or square.

[0058] Each subgroup of the first group of photosensitive elements may include fewer photosensitive elements than the first group of photosensitive elements, such that the first group of photosensitive elements may include some subgroups that are pairwise non-identical.

[0059] Some subgroups of the first group of photosensitive elements may overlap, which, as mentioned above, allows the image produced by the imaging device to have a finer resolution than non-overlapping subgroups.

[0060] In some embodiments, the number of subgroups of the first group of photosensitive elements is selected such that each photosensitive element of the first group of photosensitive elements is covered by at least one subgroup of the first group of photosensitive elements.

[0061] In this way, each photosensitive element of the first group of photosensitive elements can be connected to a first counter in at least one operating mode.

[0062] The photosensitive elements of a first group of photosensitive elements may be covered by a different number of subgroups, for example a photosensitive element may be covered by one subgroup, another photosensitive element may be covered by two subgroups, yet another photosensitive element may be covered by three subgroups, yet another photosensitive element may be covered by four subgroups, etc.

[0063] In some embodiments, subgroups of the first group of photosensitive elements are sequentially connected to the first counter in each operating mode.

[0064] For example, a first subgroup may be connected to a first counter in a first operating mode, then a second subgroup may be connected to the first counter in a second operating mode, then any further subgroups of the first group of photosensitive elements may be connected to the first counter in each subsequent operating mode, etc. Only one subgroup may be connected to the first counter at each time.

[0065] In this manner, photon detection events from all subgroups of the first group of photosensitive elements may be counted by the first counter.

[0066] The subgroups of the first group of photosensitive elements may each be connected in a short, rapid sequence such that changes in the scene imaged by the imaging device during the sequence are negligible, thus providing an approximately static image of the scene based on subsequent counting of photon detection events of the different subgroups of the first group of photosensitive elements.

[0067] In some embodiments, each photosensitive element of the first group of photosensitive elements includes a single photon avalanche diode (SPAD).

[0068] A SPAD may be capable of detecting single photons so that imaging of a scene is possible even under low light conditions.

[0069] In some embodiments, the exposure time for each operating mode (i.e., each subgroup) may be reduced compared to the imaging device of this embodiment, since the SPAD area may be increased by binning.

[0070] For example, for a 2x2 binning of photosensitive elements, the SPAD area may correspond to substantially four times the size of the photosensitive elements of the present embodiment, so that the exposure time of the array of photosensitive elements according to the embodiments may be reduced to one-fourth of the exposure time of the state of the art where neither pixel shifting nor binning is performed. The reduced exposure time may result in faster image acquisition in some embodiments, as the number of reads required to acquire image data may remain equal, compared to known image sensors that do not perform pixel shifting. Some embodiments relate to a method of operating an imaging device, the method including: counting photon detection events received from a first group of photosensitive elements of the array of photosensitive elements with a first counter; in a first mode of operation, connecting the first counter to a first subgroup of the first group of photosensitive elements; and in a second mode of operation, connecting the first counter to a second subgroup of the first group of photosensitive elements.

[0071] The imaging device may be configured according to any one of the above-described embodiments. The above-described variations, examples, technical effects and detailed descriptions of the imaging device embodiments also apply correspondingly to the embodiments of the operation method of the imaging device.

[0072] In some embodiments, connecting the first counter to the first subgroup includes individually connecting the first subgroup to the first counter, and connecting the first counter to the second subgroup includes individually connecting the second subgroup to the first counter.

[0073] In some embodiments, counting the photon detection events includes counting with a first counter a number of photon detection events received from the first subgroup in the first operating mode, and counting with the first counter a number of photon detection events received from the second subgroup in the second operating mode.

[0074] In some embodiments, the method further includes generating image data, wherein a first pixel of the image data is based on a number of photon detection events of a first subgroup in a first operating mode and a second pixel of the image data is based on a number of photon detection events of a second subgroup in a second operating mode.

[0075] In some embodiments, the method further comprises counting photon detection events received from a second group of photosensitive elements of the array of photosensitive elements with a second counter, and in the first operating mode, connecting the second counter to a third subgroup of the second group of photosensitive elements, and in the second operating mode, connecting the second counter to a fourth subgroup of the second group of photosensitive elements, wherein the third subgroup of the second group of photosensitive elements overlaps with the second subgroup of the first group of photosensitive elements in at least one photosensitive element.

[0076] In some embodiments, counting the photon detection events includes counting with a second counter a number of photon detection events received from the third subgroup in the first operating mode, and counting with a second counter a number of photon detection events received from the fourth subgroup in the second operating mode.

[0077] In some embodiments, counting the photon detection events includes counting, by a first color counter of the first counter, a number of photon detection events received from a first sub-element of the first sub-group of photosensitive elements in the first operating mode; counting, by a second color counter of the first counter, a number of photon detection events received from a second sub-element of the first sub-group of photosensitive elements in the first operating mode; counting with the first color counter a number of photon detection events received from the first sub-element of the second sub-group of photosensitive elements in the second operating mode; and counting with the second color counter a number of photon detection events received from the second sub-element of the second sub-group of photosensitive elements in the second operating mode.

[0078] In some embodiments, the method includes all subgroups of the first group of photosensitive elements including the same number of photosensitive elements and each subgroup of the first group of photosensitive elements including fewer photosensitive elements than the first group of photosensitive elements.

[0079] In some embodiments, the method selects the number of subgroups of the first group of photosensitive elements such that each photosensitive element of the first group of photosensitive elements is covered by at least one subgroup of the first group of photosensitive elements.

[0080] In some embodiments, the method sequentially connects subgroups of the first group of photosensitive elements to the first counter in each operating mode.

[0081] In some embodiments, the method detects photons with a single-photon avalanche diode at each photosensitive element of the first group of photosensitive elements.

[0082] The methods described herein are also, in some embodiments, implemented as a computer program that, when executed on a computer and / or processor, causes the computer and / or processor to perform the methods. In some embodiments, a non-transitory computer-readable recording medium is also provided having stored therein a computer program product that, when executed by a processor, such as the processors described above, causes the methods described herein to be performed.

[0083] Returning to Figure 1, a block diagram of an imager 1 according to an embodiment is shown. The imager 1 comprises an array of photosensitive elements 2 comprising photosensitive elements 3-6, each of which comprises a single photon avalanche diode (SPAD). The photosensitive elements 3-5 are coupled to a first counter 7. The photosensitive elements 5, 6 are coupled to a second counter 8.

[0084] In a first operating mode, the first counter 7 is connected to the photosensitive elements 3, 4 and the second counter 8 is connected to the photosensitive elements 5, 6. In a second operating mode, the first counter 7 is connected to the photosensitive elements 4, 5 and the second counter 8 is connected to the photosensitive element 6. In each operating mode, the first counter 7 and the second counter 8 together count photon detection events from the SPAD of each photosensitive element 3 to 6 to which they are connected in the respective operating mode.

[0085] The first counter 7 and the second counter 8 are provided in a first semiconductor layer provided on a first semiconductor chip 9, and the array of photosensitive elements 2 is provided on a second semiconductor layer provided on a second semiconductor chip 10. The first counter 7 overlaps the photosensitive elements 3, 4, and the second counter 8 overlaps the photosensitive elements 5, 6.

[0086] The first semiconductor chip 9 and the second semiconductor chip 10 are stacked together. The photosensitive elements 3 to 6 are coupled to the first counter 7 and the second counter 8 by the through electrodes 11 to 15 and the solder bumps 16 to 20, respectively.

[0087] The imaging device 1 further includes a control unit 21 for controlling the operation of the first counter 7 and the second counter 8 .

[0088] The imaging device 1 also includes an image data generator 22 for generating image data, the image data representing an image, and the values ​​of pixels of the image are based on the number of counted photon detection events counted by the first counter 7 or the second counter 8.

[0089] The imaging device 1 includes a lens 23 for focusing incident light onto an array 2 of photosensitive elements.

[0090] FIG. 2 shows in a top view a block diagram of an array 2 of photosensitive elements and a counter according to an embodiment.

[0091] The array 2 of photosensitive elements includes photosensitive elements 111 to 114, 121 to 124, 131 to 134 and 141 to 144, with each of the photosensitive elements 111, 112, 121 and 122 corresponding to the photosensitive elements 3 to 6 of FIG. 1, respectively.

[0092] The counters 110, 120, 130 and 140 are provided in a semiconductor layer below (i.e. on the side opposite to the light incidence side) the array 2 of photosensitive elements. The counter 110 corresponds to the first counter 7 in Fig. 1 and overlaps the photosensitive elements 111, 112, 113, 114. The counter 120 corresponds to the second counter 8 in Fig. 1 and overlaps the photosensitive elements 121, 122, 123, 124. The counter 130 overlaps the photosensitive elements 131, 132, 133, 134. The counter 140 overlaps the photosensitive elements 141, 142, 143, 144.

[0093] Photosensitive element group 100 of array 2 of photosensitive elements includes nine photosensitive elements, namely photosensitive elements 111, 112, 113, 114, 121, 123, 131, 132 and 141, as shown by dashed lines in FIG.

[0094] The counter 110 is coupled to the photosensitive elements 111-114, 121, 123, 131, 132, 141 of the photosensitive element group 100, as indicated by the arrows in Figure 2. The counter 110 can be connected to or disconnected from the photosensitive elements 111-114, 121, 123, 131, 132, 141 to which it is coupled, by switching the corresponding connections.

[0095] In a first mode of operation, the counter 110 is connected to the photosensitive elements 111 , 112 , 113 and 114 which constitute a first subgroup of the photosensitive element group 100 and have a centroid 101 .

[0096] In a second mode of operation, the counter 100 is connected to the photosensitive elements 112 , 114 , 121 , 123 which constitute a second subgroup of the photosensitive element group 100 and have a centroid 102 .

[0097] In a third mode of operation, the counter 100 is connected to the photosensitive elements 114 , 123 , 132 , 141 which form a third subgroup of the photosensitive element group 100 and have a centroid 103 .

[0098] In the fourth mode of operation, the counter 100 is connected to the photosensitive elements 113 , 114 , 131 and 132 which form a fourth subgroup of the photosensitive element group 100 and have a centroid 104 .

[0099] Similarly, counters 120, 130 and 140 are each coupled to nine light sensitive elements, including light sensitive elements not shown in FIG. 2, and are connected to different subgroups thereof in different operating modes.

[0100] For example, the counter 120 is coupled to a photosensitive element group including photosensitive elements 121, 122, 123, 124, 141, 142. In a first operating mode, the counter 120 is connected to the photosensitive elements 121, 122, 123, and 124. In a second operating mode, the counter 120 is connected to the photosensitive elements 122 and 124 as well as to a photosensitive element not shown in Fig. 2. In a third operating mode, the counter 120 is connected to the photosensitive elements 124 and 142 as well as to a photosensitive element not shown in Fig. 2. In a fourth operating mode, the counter 120 is connected to the photosensitive elements 123, 124, 141, 142.

[0101] That is, each counter 110, 120, 130 and 140 is coupled to a respective group of nine photosensitive elements of the array 2 of photosensitive elements, and in each operating mode is coupled to another subgroup of four photosensitive elements of the respective group of nine photosensitive elements from which it counts photon detection events. The photosensitive elements of each group are arranged in a square with three rows and three columns, and the subgroups are arranged in a square with two rows and two columns. Vertically or horizontally adjacent groups overlap by one row or one column of photosensitive elements, and vertically or horizontally adjacent subgroups (same or different groups) overlap by one row or one column of photosensitive elements. Diagonally adjacent groups or subgroups overlap by one photosensitive element.

[0102] FIG. 3 is a block diagram of a read sequence of counter 110 in four operating modes according to an embodiment.

[0103] Part A of FIG. 3 shows a first mode of operation in which a first subgroup 105 (shown in dashed lines in Part A) including photosensitive elements 111 , 112 , 113 and 114 is connected to a counter 110 .

[0104] Part B of FIG. 3 illustrates a second mode of operation in which a second subgroup 106 (shown in dashed lines in Part B) including photosensitive elements 112 , 114 , 121 , 123 is connected to a counter 110 .

[0105] Part C of Fig. 3 shows a third mode of operation in which a third subgroup 107 (shown in dashed lines in part C) including photosensitive elements 114, 123, 132 and 141 is connected to the counter 110. Part D of Fig. 3 shows a fourth mode of operation in which a fourth subgroup 108 (shown in dashed lines in part D) including photosensitive elements 113, 114, 131 and 132 is connected to the counter 110.

[0106] In this way, four subgroups 105 to 108 of the same size and shape but different centers of gravity can be connected to one counter 110 in different operating modes.

[0107] FIG. 4 is a block diagram of the read sequence of the four counters 110, 120, 130, 140 in four modes of operation according to an embodiment.

[0108] FIG. 4 differs from FIG. 3 in that for each of the four counters 110, 120, 130, 140, the subgroup to which each one of the four counters 110, 120, 130, 140 is connected in each mode of operation.

[0109] The dashed grid in FIG. 4 shows four subgroups, with the top left cell of the dashed grid showing the subgroup connected to counter 110, the top right cell of the dashed grid showing the subgroup connected to counter 120, the bottom left cell of the dashed grid showing the subgroup connected to counter 130, and the bottom right cell of the dashed grid showing the subgroup connected to counter 140.

[0110] Similar to FIG. 3, Part A of FIG. 4 corresponds to a first mode of operation, Part B of FIG. 4 corresponds to a second mode of operation, Part C of FIG. 4 corresponds to a third mode of operation, and Part D of FIG. 4 corresponds to a fourth mode of operation.

[0111] Thus, in each mode of operation, each counter 110, 120, 130 and 140 can be connected to a different subgroup, all of which have the same size and shape but different centers of gravity.

[0112] The number of photon detection events counted by each counter 110, 120, 130, 140 in an operational mode corresponds to the sum of the photon detection events across the four photosensitive elements, which have different centroids for each operational mode, the pitch of the centroids corresponding to half the pitch of the counters.

[0113] By aligning pixels in an image generated by the imaging device 1 having values ​​based on the number of photon detection events counted for different subgroups such that the alignment of the pixels (i.e., their positions relative to each other) corresponds to the alignment of the corresponding centroids of the subgroups (i.e., their positions relative to each other), in some embodiments, the image resolution is improved relative to the image resolution that would be obtained if the pixels were based only on non-overlapping subgroups, by aligning pixels having values ​​based on the number of photon detection events counted for different subgroups such that the alignment of the pixels (i.e., their positions relative to each other) corresponds to the alignment of the corresponding centroids of the subgroups (i.e., their positions relative to each other), in some embodiments, the image resolution is improved relative to the image resolution that would be obtained if the pixels were based only on non-overlapping subgroups (e.g., only subgroups corresponding to the first operating mode).

[0114] FIG. 5 is a block diagram of bit usage in the image sensor of this embodiment based on a SPAD.

[0115] The image sensor of this embodiment includes SPAD-based photosensitive elements 201-204. Each photosensitive element 201-204 is connected to a separate counter 205-208. Photosensitive element 201 is connected to counter 205. Photosensitive element 202 is connected to counter 206. Photosensitive element 203 is connected to counter 207. Photosensitive element 204 is connected to counter 208.

[0116] To acquire an image, each photosensitive element 201-204 is read once by a corresponding counter 205-208. Thus, in the exemplary case where the number of photon detection events from each photosensitive element 201-204 counted by each counter 205-208 is stored in a 16-bit register, a separate 16-bit register is required for each photosensitive element 201-204 to acquire a high resolution image.

[0117] FIG. 6 is a block diagram of bit usage in a SPAD-based image sensor according to one embodiment.

[0118] The image sensor is an example of an image sensor included in the imaging device 1 and includes an array 2 of photosensitive elements and a counter 110 as described above with reference to FIGS.

[0119] In a first mode of operation, the counter 110 counts photon detection events from the first subgroup 105, which includes photosensitive elements 111-114. In a second mode of operation, the counter 110 counts photon detection events from the second subgroup 106, which includes photosensitive elements 112, 114, 121, and 123. In a third mode of operation, the counter 110 counts photon detection events from the third subgroup 107, which includes photosensitive elements 114, 123, 132, and 141. In a fourth mode of operation, the counter 108 counts photon detection events from the fourth subgroup 108, which includes photosensitive elements 113, 114, 131, and 132.

[0120] The number of photon detection events from each subgroup 105-108 counted by the counter 110 is stored in a 16-bit register. The 16-bit register size is merely an example. The present disclosure is not limited to the 16-bit register size. However, the subgroups 105-108 are read out sequentially in the following four operation modes. Therefore, the counter 110 only needs to have one 16-bit register. In the first operation mode, the number of photon detection events from the first subgroup 105 is stored in the 16-bit register. In the second operation mode, the number of photon detection events from the second subgroup 106 is stored in the 16-bit register. In the third operation mode, the number of photon detection events from the third subgroup 107 is stored in the 16-bit register. In the fourth operation mode, the number of photon detection events from the fourth subgroup 108 is stored in the 16-bit register.

[0121] Thus, instead of counting photon detection events in parallel and per photosensitive element, the photon detection events are counted sequentially and per subgroup, and thus the space occupied by the bits for storing the number of photon detection events can be reduced in some embodiments by requiring only one 16-bit register per counter.

[0122] FIG. 7 is a diagram showing the basic operation of the imaging device 1 according to the embodiment.

[0123] A SPAD-based photosensitive element 301, which is an example of any one of the photosensitive elements 111-114, 121-124, 131-134, 141-144 of FIG. 2, is connected to a counter 302, which is an example of the corresponding counters 110, 120, 130, 140 of FIG.

[0124] When the photosensitive element 301 is connected to the counter 302, a signal 303 is provided to the counter 302. When a photon 304 reaches the photosensitive element 301 and is detected by the SPAD of the photosensitive element 301, the SPAD of the photosensitive element 301 outputs a negative edge representing a photon detection event. The counter 302 counts the negative edges and thus the photon detection events.

[0125] Fig. 8 is a diagram showing a circuit arrangement according to an embodiment. It shows the circuit arrangement of a 4x4 block of the array 2 of photosensitive elements of Fig. 2. The free ends of the wiring indicate circuit parts that are not shown.

[0126] 2 included in the first subgroup 105 are coupled to the counter 110 via an AND gate 411 and an OR gate 410. When a control signal G1_SEL input to the AND gate 411 is set to a high (H) level, the first subgroup 105 is connected to the counter 110 and a signal indicative of a photon detection event from any one of the photosensitive elements 111-114 is transferred to the counter 110 via the AND gate 411 and the OR gate 410. When the control signal G1_SEL is set to a low (L) level, the AND gate 411 does not transfer a signal indicative of a photon detection event from any one of the photosensitive elements 111-114 and the first subgroup is disconnected from the counter 110.

[0127] Additionally, the photosensitive elements 112, 114, 121, and 123 of the second subgroup 106 are coupled to the counter 110 via an AND gate 412 and an OR gate 410. When the control signal G2_SEL is set to a high level, the photosensitive elements 112, 114, 121, and 123 are connected to the counter 110 and a signal indicative of a photon detection event from any one of them is transferred to the counter 110 via the AND gate 412 and the OR gate 410. When the control signal G2_SEL is set to a low level, the AND gate 412 does not transfer a signal and the photosensitive elements 112, 114, 121, and 123 are disconnected from the counter 110.

[0128] Similarly, the photosensitive elements 114, 123, 132, 141 of the third subgroup 107 and the photosensitive elements 113, 114, 131 and 132 of the fourth subgroup 108 are coupled to the counter 110 via an AND gate 413 and an OR gate 410. The third subgroup 107 and the fourth subgroup 108 are connected to the counter 110 by setting the control signal G3_SEL or G4_SEL, respectively, to a high level, and are disconnected from the counter 110 by setting the control signal G3_SEL or G4_SEL, respectively, to a low level.

[0129] In a first operating mode, the control signal G1_SEL is set to a high level such that the first subgroup 105 is connected to the counter 110, and the control signals G2_SEL, G3_SEL, G4_SEL are set to a low level such that the second, third and fourth subgroups 106, 107 and 108 are disconnected from the counter 110. In a second operating mode, the control signal G2_SEL is set to a high level such that the second subgroup 106 is connected to the counter 110, and the control signals G1_SEL, G3_SEL, G4_SEL are set to a low level such that the first, third and fourth subgroups 105, 107 and 108 are disconnected from the counter 110. In a third operating mode, the control signal G3_SEL is set to H level so that the third subgroup 107 is connected to the counter 110, and the control signals G1_SEL, G2_SEL, G4_SEL are set to L level so that the first, second and fourth subgroups 105, 106 and 108 are disconnected from the counter 110. In a fourth operating mode, the control signal G4_SEL is set to H level so that the fourth subgroup 108 is connected to the counter 110, and the control signals G1_SEL, G2_SEL, G3_SEL are set to L level so that the first, second and third subgroups 105, 106 and 107 are disconnected from the counter 110.

[0130] Similarly, the photosensitive elements 121 to 124 are coupled to the counter 120 via an AND gate 421 and an OR gate 420, and can be connected to the counter 120 by setting the control signal G1_SEL to a high level. The photosensitive elements 123, 124, 141, and 142 are coupled to the counter 120 via an AND gate 423 and an OR gate 420, and can be connected to the counter 120 by setting the control signal G4_SEL to a high level. The photosensitive elements 131 to 134 are coupled to the counter 130 via an AND gate 431 and an OR gate 430, and can be connected to the counter 130 by setting the control signal G1_SEL to a high level. The photosensitive elements 132, 134, 141, and 143 are coupled to the counter 130 via an AND gate 432 and an OR gate 430, and can be connected to the counter 130 by setting the control signal G2_SEL to a high level. The photosensitive elements 141 to 144 are coupled to the counter 140 via an AND gate 431 and an OR gate 440, and can be connected to the counter 140 by setting the control signal G1_SEL to an H level.

[0131] Thus, a subgroup and its photosensitive elements can be connected to the counter by setting the corresponding control signal to a H level. A subgroup whose photon detection events should not be counted in the operational mode can be disconnected from the counter by setting the corresponding control signal to a L level such that the corresponding AND gate blocks the signal indicating a photon detection event.

[0132] It should be noted that the present disclosure is not limited to the embodiment of Figure 8. Those skilled in the art will recognize other suitable circuit configurations.

[0133] FIG. 9 is a diagram of image data generated by the imaging device 1 according to an embodiment.

[0134] Parts A to D of Fig. 9 correspond to respective portions of Fig. 3. Part E of Fig. 9 shows a pixel array 500 of an image represented by image data generated by the imaging device 1 based on the number of counted photon detection events.

[0135] Pixel array 500 includes pixels 501, 502, 503, and 504. The value of pixel 501 is based on the counted number of photon detection events from a first subgroup 105. The value of pixel 502 is based on the counted number of photon detection events from a second subgroup 106. The value of pixel 503 is based on the counted number of photon detection events from a third subgroup 107. The value of pixel 504 is based on the counted number of photon detection events from a fourth subgroup 108.

[0136] The pixels 501-504 are positioned according to the relative positions of the centroids 101-104 of their respective subgroups 105-108 with respect to each other.

[0137] Fig. 10 shows a block diagram of the readout principle of an array 600 of photosensitive elements for color coding according to an embodiment. The array 600 of photosensitive elements is included in a color image sensor and is arranged similarly to the array 2 of photosensitive elements of Fig. 2, except that each photosensitive element of the array 600 includes four sub-elements and each counter includes four sub-counters. The photosensitive elements of the array 600 of photosensitive elements are based on SPAD. Each sub-element of the photosensitive element is configured to detect photons of a given color, and each sub-counter is associated with a given color and configured to count photon detection events from the sub-elements of the corresponding color.

[0138] The photosensitive element 611 includes a sub-element 611a for detecting red light, sub-elements 611b and 611c for detecting green light, and a sub-element 61Id for detecting blue light. The other photosensitive elements are configured similarly. Sub-elements ending with the reference letter "a" are configured to detect red light and are hatched vertically. Sub-elements ending with the reference letter "b" or "c" are configured to detect green light and are hatched diagonally. Sub-elements ending with the reference letter "d" are configured to detect blue light and are hatched horizontally. The sub-elements are thus arranged according to the Bayer pattern for color coding in a red-green-blue (RGB) color sensor.

[0139] Similarly, counters 610, 620 and 630 each include four sub-counters, with sub-counters ending in "a" being associated with the color red, sub-counters ending in "b" or "c" being associated with the color green, and sub-counters ending in "d" being associated with the color blue.

[0140] Part A of FIG. 10 illustrates a first mode of operation of the array 600 of photosensitive elements.

[0141] The first subgroup 601 includes photosensitive elements 611, 612, 613, and 614 and is connected to a first counter 610. Sub-elements 611a, 612a, 613a, and 614a are configured to detect red light and are connected to sub-counter 610a. Sub-elements 611b, 612b, 613b, and 614b are configured to detect green light and are connected to sub-counter 610b. Sub-elements 611c, 612c, 613c, and 614c are configured to detect green light and are connected to sub-counter 610c. Sub-elements 61Id, 612d, 613d, and 614d are configured to detect blue light and are connected to sub-counter 610d.

[0142] The center of gravity of the first subgroup 601 is shown as a cross between the subelements 61Id, 612c, 613b, 614a.

[0143] Part B of FIG. 10 illustrates a second mode of operation of the array 600 of photosensitive elements.

[0144] The second subgroup 602 includes photosensitive elements 612, 614, 621, and 623 and is connected to the first counter 610. The subelements 612a, 614a, 621a, and 623a configured to detect red light are connected to the subcounter 610a associated with red. The subelements 612b, 614b, 621b, and 623b configured to detect green light are connected to the subcounter 610b associated with green. The subelements 612c, 614c, 621c, and 623c configured to detect green light are connected to the subcounter 610c associated with green. The subelements 612d, 614d, 62Id, and 623d configured to detect blue light are connected to the subcounter 610d associated with blue.

[0145] The center of gravity of the second subgroup 602 is illustrated as a cross between subelements 612d, 621c, 614b, and 623a. It is shifted to the right by one photosensitive element (i.e., two subelements) relative to the first subgroup 601. Thus, the number of counted photon detection events from the first subgroup 601 and the number of counted photon detection events from the second subgroup 602 correspond to different centers of gravity.

[0146] FIG. 10 further shows a second counter 620 and (a portion of) a third counter 630 .

[0147] In a first operating mode, the third subgroup 603, including the photosensitive elements 612, 622, 623 and 624, is connected to the second counter 620. The subelements 621a, 622a, 623a and 624a for detecting red light are connected to the subcounter 620a associated with the color red. The subelements 621b, 622b, 623b and 624b for detecting green light are connected to the subcounter 620b associated with the color green. The subelements 621c, 622c, 623c and 624c for detecting green light are connected to the subcounter 620c associated with the color green. The subelements 62Id, 622d, 623d and 624d for detecting blue light are connected to the subcounter 620d associated with the color blue.

[0148] Further, as partially shown, sub-elements 631a and 633a for detecting red light are connected to sub-counter 630a associated with red in counter 630, and sub-elements 631c and 633c for detecting green light are connected to sub-counter 630c associated with green in counter 630.

[0149] In a second operating mode, the fourth subgroup 604 (partially shown) includes photosensitive elements 622, 624, 631 and 633 and is connected to the second counter 620. The subelements 622a, 624a, 631a and 633a for detecting red light are connected to the subcounter 620a associated with red. The subelements 622b and 624b for detecting green light are connected to the subcounter 620b associated with green. The subelements 622c, 624c, 631c and 633c for detecting green light are connected to the subcounter 620c associated with green light. The subelements 622d and 624d for detecting blue light are connected to the subcounter 620d associated with blue. Although only two operating modes of the array 600 of photosensitive elements are shown in FIG. 10, the array 600 of photosensitive elements is configured to operate in four operating modes, and two more subgroups can be connected to each counter as shown in FIGS. 3 and 4.

[0150] FIG. 11 is a block diagram of 3×3 binning in an array 700 of photosensitive elements according to an embodiment.

[0151] The array of photosensitive elements 700 is an example of an array of photosensitive elements that can be included in the imaging device 1 instead of the array of photosensitive elements 2. The photosensitive elements of the array of photosensitive elements 700 are based on SPADs.

[0152] That is, each subgroup of the photosensitive element group associated with a counter is square and includes nine photosensitive elements.

[0153] In the array 700 of Figure 11, each counter is coupled to a group of 25 light sensitive elements arranged in 5 rows and 5 columns. Each such group contains 9 square subgroups, each of which contains 9 light sensitive elements arranged in 3 rows and 3 columns. The centroids of the subgroups vary between the subgroups. The centroids are indicated by crosses in Figure 11. Each counter can be individually connected (and disconnected) to each of the 9 square subgroups.

[0154] Photon detection events from each subgroup are counted in a corresponding operating mode in which the respective subgroup is connected to a counter, such that the array of photosensitive elements 700 can be operated in nine different operating modes, in which a different one of the nine subgroups of the photosensitive element group is connected to a corresponding counter for counting photon detection events therefrom.

[0155] Part A of Fig. 11 shows a first mode of operation in which a first subgroup 701 including photosensitive elements 711 to 713 is connected to a first counter 710 for counting photon detection events. Furthermore, photosensitive elements 721 to 729 are connected to a second counter 720 for counting photon detection events and photosensitive elements 731 to 739 are connected to a third counter 730 for counting photon detection events.

[0156] Part B of Fig. 11 shows a second mode of operation in which a second subgroup 702 including photosensitive elements 712, 713, 715, 716, 718, 719, 721, 724, 727 is connected to a first counter 710 for counting photon detection events. The second subgroup 702 (and its center of gravity) is shifted one photosensitive element to the right with respect to the first subgroup 701. A second counter 720 is connected to photosensitive elements 722, 723, 725, 726, 728, 729, 731, 734, 737 for counting photon detection events. A third counter 730 is connected to photosensitive elements 732, 733, 735, 736, 738 and 739 as well as three photosensitive elements not shown in Fig. 11 for counting photon detection events.

[0157] Part C of Fig. 11 shows a third operation mode in which the third subgroup 703 including the photosensitive elements 713, 716, 719, 721, 722, 724, 725, 727, 728 is connected to the first counter 710 to count the photon detection events. The second subgroup 703 (and its center of gravity) is shifted by one photosensitive element to the right with respect to the second subgroup 702. The second counter 720 is connected to the photosensitive elements 723, 726, 729, 731, 732, 734, 735, 737, 738 to count the photon detection events. The third counter 730 is connected to the photosensitive elements 733, 736 and 739 as well as six photosensitive elements not shown in Fig. 11 to count the photon detection events.

[0158] In addition to the three operating modes shown in parts A to C of Fig. 11, the array of photosensitive elements 700 can be operated in six more operating modes not shown in Fig. 11. In the fourth to sixth operating modes, the counters 710, 720 and 730 are connected to subgroups that are shifted down by one photosensitive element relative to the subgroups 701, 702 and 703 shown in parts A to C. In the seventh to ninth operating modes, the counters 710, 720 and 730 are connected to subgroups that are shifted down by two photosensitive elements relative to the subgroups 701, 702 and 703 shown in parts A to C.

[0159] Thus, in the array of photosensitive elements 700, a 3x3 binning is performed such that the number of photon detection events counted by counter 710, 720 or 730 is the sum of the number of photon detection events counted from the nine photosensitive elements.

[0160] By performing 3x3 binning, one counter can be provided for nine photosensitive elements instead of 2x2 binning with one counter for four photosensitive elements. Therefore, fewer counters are required and the size per photosensitive element (i.e., the area occupied by each photosensitive element) is reduced. By performing pixel shifting, a high resolution can be obtained for the image generated by the imaging device 1. Figure 12 is a flow diagram of a method 800 for operating the imaging device 1 according to an embodiment.

[0161] The imaging device 1 of a SPAD-based photosensitive element array, such as the array of photosensitive elements 2 of Figures 2-4, the array of photosensitive elements 600 of Figure 10, or the array of photosensitive elements 700 of Figure 11, is operated with a method 800. Thus, examples of a first counter operated with the method 800 include the first counter 110 of Figures 2-4, the first counter 610 of Figure 10, and the first counter 710 of Figure 11. Examples of a second counter operated with the method 800 include the second counter 120 of Figures 2-4, the second counter 620 of Figure 11, and the second counter 720 of Figure 11. The first group of photosensitive elements operated with the method 800 includes all the photosensitive elements coupled to the first counter, such as the first group 100 of Figure 2. The first subgroup operated by the method 800 includes the first subgroup 105 of Figures 2 to 4, the first subgroup 601 of Figure 10 and the first subgroup 701 of Figure 11. The second subgroup operated by the method 800 includes the second subgroup 106 of Figures 2 to 4, the second subgroup 602 of Figure 10 and the second subgroup 702 of Figure 11. Examples of the second group of photosensitive elements operated by the method 800 include groups of photosensitive elements that are coupled (i.e. may be connected) to the second counters 120, 620 or 720 of Figures 2 to 4, 10 or 11, respectively, and examples of the third and fourth subgroups operated by the method include such subgroups of Figures 2 to 4, 10 and 11 that are connected to the respective second counters 120, 620 or 720 in the first or second mode of operation, respectively.

[0162] In S800a, all subgroups of the first group of photosensitive elements and the second group of photosensitive elements include the same number of photosensitive elements.

[0163] In S800b, each subgroup of the first group of photosensitive elements and each subgroup of the second group of photosensitive elements includes fewer photosensitive elements than the first group of photosensitive elements or the second group of photosensitive elements, respectively.

[0164] In S800c, the number of subgroups of the first group of photosensitive elements and the number of subgroups of the second group of photosensitive elements are selected such that each photosensitive element of the first group of photosensitive elements and each photosensitive element of the second group of photosensitive elements is covered by at least one subgroup of the first group of photosensitive elements or at least one subgroup of the second group of photosensitive elements, respectively.

[0165] The steps of S800a, S800b and S800c are for preparing the array of photosensitive elements. In S810, photon detection events received from a first group of photosensitive elements of the array of photosensitive elements are counted in a first counter.

[0166] To count the photon detection events in S810, in S811, a first counter is connected to a first subgroup of the first group of photosensitive elements in the first operating mode 801. This includes individually connecting the first subgroup to the first counter. Then, in S812, the number of photon detection events received from the first subgroup in the first operating mode 801 is counted in the first counter. This includes steps of S812a, S812b, and S812c to obtain color image data.

[0167] In S812a, in a first operating mode, the number of photon detection events received from a first sub-element of a first sub-group of photosensitive elements configured to detect red light is counted in a first color counter associated with the color red of the first counter.

[0168] In S812b, in the first operating mode, the number of photon detection events received from a second sub-element of the first sub-group of photosensitive elements configured to detect green light is counted in a second color counter of the first counter associated with the color green.

[0169] In S812c, in the first operating mode, the number of photon detection events received from a third sub-element of the first sub-group of photosensitive elements configured to detect blue light is counted in a third color counter of the first counters associated with the color blue.

[0170] Next, in the second operating mode 802, in S813, the first counter is connected to a second subgroup of the first group of photosensitive elements. That is, the second operating mode 802 is performed after the first operating mode 801, and the first subgroup and the second subgroup are sequentially connected to the first counter in the first operating mode and the second operating mode, respectively. The connection of the first counter and the second subgroup in S813 includes individually connecting the second subgroup to the first counter.

[0171] In S814, a number of photon detection events received from a second subgroup of the first group of photosensitive elements in a second operating mode is counted with a first counter, which includes steps S814a, S814b, and S814c for obtaining color image data.

[0172] In S814a, in a second operating mode, the number of photon detection events received from a first sub-element of the second sub-group of photosensitive elements configured to detect red light is counted in a first color counter associated with the color red of the first counter.

[0173] In S814b, in the second operating mode, the number of photon detection events received from a second sub-element of the second sub-group of photosensitive elements configured to detect green light is counted in a second color counter of the first counter associated with the color green.

[0174] In S814c, in the second operating mode, the number of photon detection events received from a third sub-element of the second sub-group of photosensitive elements configured to detect blue light is counted in a third color counter of the first counters associated with the color blue.

[0175] In S820, photon detection events received from a second group of photosensitive elements of the array of photosensitive elements are counted in a second counter, which includes in S821 connecting the second counter to a third subgroup of the second group of photosensitive elements in the first operating mode 801, where the third subgroup of the second group of photosensitive elements overlaps with the second subgroup of the first group of photosensitive elements in at least one photosensitive element, and in S822 counting the number of photon detection events received from the third subgroup in the first operating mode 801 by the second counter.

[0176] S822 includes counting photon detection events received from sub-elements of a third sub-group having sub-counters associated with red, green or blue, similar to steps S812a, S812b and S812c, except that the detection of different colors in S822 is not described for the sake of brevity.

[0177] In S823, a second counter is connected to a fourth subgroup of the second group of photosensitive elements in the second operating mode 802.

[0178] At S824, in the second operating mode 802, the number of photon detection events received from a fourth subgroup of the second group of photosensitive elements is counted with a second counter.

[0179] In S830, image data is generated, where a first pixel of the image data is based on the number of photon detection events of a first subgroup in a first operating mode 801, and a second pixel of the image data is based on the number of photon detection events of a second subgroup in a second operating mode 802.

[0180] Counting photon detection events in S812, S814, S822 and S824 includes detecting photons using a single photon avalanche diode (SPAD) at each photosensitive element of the first or second group of photosensitive elements, respectively.

[0181] In the imaging device 1 according to the present disclosure, it may be possible to reduce the size of the photosensitive elements without trading off the number of bits of the counter. By implementing one counter for a predetermined number of photosensitive elements (for example, four photosensitive elements), it is possible to reduce the counter area required for the predetermined number (for example, four) of photosensitive elements. In addition, since the connection between the photosensitive elements and the counter can be controlled, it is possible to shift the photosensitive elements to be read out.

[0182] It should be appreciated that the embodiments describe the method with an exemplary order of method steps. However, the particular order of the method steps is provided for illustrative purposes only and should not be construed as binding. For example, the order of S812a, S812b, and S812c, and / or the order of S814a, S814b, and S814c in the embodiment of FIG. 12 may be interchanged. Also, the order of S810 and S820 and / or the order of the first operating mode 801 and the second operating mode 802 in the embodiment of FIG. 12 may be swapped. Other variations in the order of method steps will be apparent to those skilled in the art.

[0183] It should be noted that the division of control units 21 and 22 is for illustrative purposes, and the present disclosure is not limited to any particular division of functionality in any particular unit. For example, control units 21 and / or 22 may be implemented by respective programmed processors, field programmable gate arrays (FPGAs), etc.

[0184] 12 may also be implemented as a computer program that, when executed on a computer and / or processor, causes a computer and / or processor, such as the control unit 21 described above, to perform the method. In some embodiments, there is also provided a non-transitory computer readable recording medium having stored therein a computer program product that, when executed by a processor, such as the processor described above, causes the computer and / or processor to perform the method described above.

[0185] All units and entities described in this specification and recited in the accompanying claims may be implemented as integrated circuit logic, for example on a chip, unless otherwise noted, and the functions provided by such units and entities may be implemented by software, unless otherwise noted.

[0186] To the extent that the embodiments of the present disclosure described above are implemented, at least in part, using software-controlled data processing apparatus, it will be understood that computer programs providing such software control, and transmission, storage or other media on which such computer programs are provided, are contemplated as aspects of the present disclosure.

[0187] The present technology can also be configured as described below.

[0188] (1) an array of photosensitive elements; a first counter for counting photon detection events received from the first group of photosensitive elements; Equipped with In a first mode of operation, the first counter is connected to a first subgroup of the first group of photosensitive elements; In a second mode of operation, the first counter is connected to a second subgroup of the first group of photosensitive elements. Imaging device. (2) the first counter is provided in a first semiconductor layer; the array of photosensitive elements is disposed in a second semiconductor layer; The first counter overlaps with an area in which the first subgroup is provided. The imaging device according to (1) above. (3) the first semiconductor layer is provided on a first chip; The second semiconductor layer is disposed on a second chip. The imaging device according to (2) above. (4) Each subgroup of the first group of photosensitive elements is configured to be individually connected to the first counter. The imaging device according to any one of (1) to (3) above. (5) further comprising an image data generation unit configured to generate image data; a first pixel of the image data based on a number of photon detection events of the first subgroup in the first mode of operation; A second pixel of the image data is based on a number of photon detection events of the second subgroup in the second mode of operation. The imaging device according to any one of (1) to (4) above. (6) a second counter for counting photon detection events received from a second group of photosensitive elements of the array of photosensitive elements; In the first mode of operation, the second counter is connected to a third subgroup of the second group of photosensitive elements; In the second mode of operation, the second counter is connected to a fourth subgroup of the second group of photosensitive elements; The third subgroup of the second group of photosensitive elements overlaps with the second subgroup of the first group of photosensitive elements at least in one photosensitive element. The imaging device according to any one of (1) to (5) above. (7) each of the first subgroup and the second subgroup includes at least two photosensitive elements; The first subgroup and the second subgroup overlap at least one photosensitive element. The imaging device according to any one of (1) to (6) above. (8) Each of the first subgroup and the second subgroup includes at least two rows of photosensitive elements and at least two columns of photosensitive elements. The imaging device according to (7) above. (9) Each of the first subgroup and the second subgroup is a square. The imaging device according to (7) or (8) above. (10) Each of the first subgroup and the second subgroup includes two rows of photosensitive elements and two columns of photosensitive elements. The imaging device according to (9) above. (11) Each of the first subgroup and the second subgroup includes three rows of light receiving elements and three columns of light receiving elements. The imaging device according to (9) above. (12) each photosensitive element of the first group of photosensitive elements includes a first sub-element for detecting light of a first color and a second sub-element for detecting light of a second color; The first counter includes a first color counter for counting photon detection events received from the first sub-element and a second color counter for counting photon detection events received from the second sub-element. The imaging device according to any one of (1) to (11) above. (13) All subgroups of the first group of photosensitive elements include the same number of photosensitive elements, and each subgroup of the first group of photosensitive elements includes fewer photosensitive elements than the first group of photosensitive elements. The imaging device according to any one of (1) to (12) above. (14) The number of subgroups of said first group of photosensitive elements is selected such that each photosensitive element of said first group of photosensitive elements is covered by at least one subgroup of said first group of photosensitive elements. The imaging device according to (13) above. (15) Subgroups of the first group of photosensitive elements are sequentially connected to the first counter in each operating mode. The imaging device according to (14) above. (16) Each of the first group of photoreceptor elements includes a single-photon avalanche diode. The imaging device according to any one of (1) to (15) above. (17) 1. A method of operating an imaging device, comprising: counting photon detection events received from a first group of photosensitive elements of the array of photosensitive elements with a first counter; in a first mode of operation, connecting a first counter to a first subgroup of said first group of photosensitive elements; In a second mode of operation, a first counter is connected to a second subgroup of the first group of photosensitive elements. method. (18) connecting the first counter to the first subgroup includes individually connecting the first subgroup to the first counter; Connecting the first counter to the second subgroup includes connecting the second subgroup to the first counter individually. The method according to (17) above. (19) Counting the photon detection events includes: counting, in the first mode of operation, a number of photon detection events received from the first subgroup with the first counter; counting, in the second mode of operation, a number of photon detection events received from the second subgroup with the first counter. Including The method according to (17) or (18) above. (20) Generate image data; a first pixel of the image data based on a number of photon detection events of the first subgroup in the first mode of operation; A second pixel of the image data is based on a number of photon detection events of the second subgroup in the second mode of operation. 2. The method according to any one of (17) to (19) above. (twenty one) counting photon detection events received from a second group of photosensitive elements of the array of photosensitive elements with a second counter; in said first mode of operation, connecting said second counter to a third subgroup of said second group of photosensitive elements; in the second mode of operation, connecting the second counter to a fourth subgroup of the second group of photosensitive elements; The third subgroup of the second group of photosensitive elements overlaps with the second subgroup of the first group of photosensitive elements at least one photosensitive element. 20. The method according to any one of (17) to (20) above. (twenty two) Counting the photon detection events includes: counting with the second counter a number of photon detection events received from the third subgroup in the first mode of operation; counting with the second counter a number of photon detection events received from the fourth subgroup in the second mode of operation. Including The method according to (21) above. (twenty three) Counting the photon detection events includes: counting, in the first mode of operation, a number of photon detection events received from a first sub-element of the first sub-group of the photosensitive elements by a first color counter of the first counter; counting, in the first mode of operation, a number of photon detection events received from the second sub-elements of the first sub-group of the photosensitive elements by a second color counter of the first counter; counting, in the second mode of operation, a number of photon detection events received from the first sub-elements of the second sub-group of the photosensitive elements by the first color counter; counting, by the second color counter, a number of photon detection events received from the second sub-elements of the second sub-group of the photosensitive elements in the second mode of operation. Including 2. A method according to any one of (17) to (22) above. (twenty four) all subgroups of said first group of photosensitive elements include the same number of photosensitive elements; Each subgroup of the first group of photosensitive elements includes fewer photosensitive elements than the first group of photosensitive elements. 2. The method according to any one of (17) to (23) above. (twenty five) Selecting the number of subgroups of the first group of photosensitive elements such that each photosensitive element of the first group of photosensitive elements is covered by at least one subgroup of the first group of photosensitive elements. The method according to (24) above. (26) sequentially connecting said subgroups of said first group of photosensitive elements to said first counter in respective modes of operation. The method according to (25) above. (27) Detecting a photon with a single-photon avalanche diode at each photosensitive element of the first group of photosensitive elements 27. The method according to any one of (17) to (26) above. (28) A program code that, when executed on a computer, causes the computer to execute the method according to any one of (17) to (27) above. Computer program. (29) A computer program product that, when executed by a processor, performs the method according to any one of (17) to (27) above. A non-transitory computer-readable recording medium.

Claims

1. an array of photosensitive elements; a first counter for counting photon detection events received from the first group of photosensitive elements; Equipped with In a first mode of operation, the first counter is connected to a first subgroup of the first group of photosensitive elements; In a second mode of operation, the first counter is connected to a second subgroup of the first group of photosensitive elements. Imaging device.

2. the first counter is provided in a first semiconductor layer; The array of photosensitive elements comprises: provided on the second semiconductor layer, The first counter overlaps with an area in which the first subgroup is provided. The imaging device according to claim 1 .

3. the first semiconductor layer is provided on a first chip; The second semiconductor layer is disposed on a second chip. The imaging device according to claim 2 .

4. Each subgroup of the first group of photosensitive elements is configured to be individually connected to the first counter. The imaging device according to claim 1 .

5. further comprising an image data generation unit configured to generate image data; a first pixel of the image data based on a number of photon detection events of the first subgroup in the first mode of operation; A second pixel of the image data is based on a number of photon detection events of the second subgroup in the second mode of operation. The imaging device according to claim 1 .

6. a second counter for counting photon detection events received from a second group of photosensitive elements of the array of photosensitive elements; In the first mode of operation, the second counter is connected to a third subgroup of the second group of photosensitive elements; In the second mode of operation, the second counter is connected to a fourth subgroup of the second group of photosensitive elements; The third subgroup of the second group of photosensitive elements overlaps with the second subgroup of the first group of photosensitive elements at least one photosensitive element. The imaging device according to claim 1 .

7. each of the first subgroup and the second subgroup includes at least two photosensitive elements; The first subgroup and the second subgroup overlap at least one photosensitive element. The imaging device according to claim 1 .

8. each photosensitive element of the first group of photosensitive elements includes a first sub-element for detecting light of a first color and a second sub-element for detecting light of a second color; The first counter includes a first color counter for counting photon detection events received from the first sub-element and a second color counter for counting photon detection events received from the second sub-element. The imaging device according to claim 1 .

9. All subgroups of the first group of photosensitive elements include the same number of photosensitive elements, and each subgroup of the first group of photosensitive elements includes fewer photosensitive elements than the first group of photosensitive elements. The imaging device according to claim 1 .

10. The number of subgroups of said first group of photosensitive elements is selected such that each photosensitive element of said first group of photosensitive elements is covered by at least one subgroup of said first group of photosensitive elements. The imaging device according to claim 9.

11. 1. A method of operating an imaging device, comprising: counting photon detection events received from a first group of photosensitive elements of the array of photosensitive elements with a first counter; in a first mode of operation, connecting a first counter to a first subgroup of said first group of photosensitive elements; In a second mode of operation, a first counter is connected to a second subgroup of the first group of photosensitive elements. method.

12. connecting the first counter to the first subgroup includes individually connecting the first subgroup to the first counter; Connecting the first counter to the second subgroup includes connecting the second subgroup to the first counter individually. The method of claim 11.

13. Counting the photon detection events includes: counting, in the first mode of operation, a number of photon detection events received from the first subgroup with the first counter; counting, in the second mode of operation, a number of photon detection events received from the second subgroup with the first counter. Including The method of claim 11.

14. Generate image data; a first pixel of the image data based on a number of photon detection events of the first subgroup in the first mode of operation; A second pixel of the image data is based on a number of photon detection events of the second subgroup in the second mode of operation. The method of claim 11.

15. counting photon detection events received from a second group of photosensitive elements of the array of photosensitive elements with a second counter; in said first mode of operation, connecting said second counter to a third subgroup of said second group of photosensitive elements; in said second mode of operation, connecting said second counter to a fourth subgroup of said second group of photosensitive elements; The third subgroup of the second group of photosensitive elements overlaps with the second subgroup of the first group of photosensitive elements at least one photosensitive element. The method of claim 11.

16. Counting the photon detection events includes: counting with the second counter a number of photon detection events received from the third subgroup in the first mode of operation; counting with the second counter a number of photon detection events received from the fourth subgroup in the second mode of operation. Including The method of claim 15.

17. Counting the photon detection events includes: counting, in the first mode of operation, a number of photon detection events received from a first sub-element of the first sub-group of the photosensitive elements by a first color counter of the first counter; counting, in the first mode of operation, a number of photon detection events received from a second sub-element of the first sub-group of the photosensitive elements by a second color counter of the first counter; counting, in the second mode of operation, a number of photon detection events received from the first sub-elements of the second sub-group of the photosensitive elements by the first color counter; counting, by the second color counter, a number of photon detection events received from the second sub-elements of the second sub-group of the photosensitive elements in the second mode of operation. Including The method of claim 11.

18. all subgroups of said first group of photosensitive elements include the same number of photosensitive elements; Each subgroup of the first group of photosensitive elements includes fewer photosensitive elements than the first group of photosensitive elements. The method of claim 11.

19. selecting a number of subgroups of the first group of photosensitive elements such that each photosensitive element of the first group of photosensitive elements is covered by at least one subgroup of the first group of photosensitive elements; 20. The method of claim 18.

20. sequentially connecting said subgroups of said first group of photosensitive elements to said first counter in respective modes of operation.

20. The method of claim 19.

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