Photoelectric conversion device, imaging device, control method, and computer program

Abstract

To provide a technique materializing suppression of an increase in circuit scale and furthermore materializing suitable pixel readout processing.SOLUTION: A photovoltaic device is provided which has a pixel including a photovoltaic unit which outputs a signal in accordance with an incident photon. The photovoltaic device has: first measuring means, second measuring means, and a changing means. The first measuring means measures the number of photons incident on the pixel. The second measuring means measures a time from the start of measurement performed by the first measuring means until time when the measured value of the first measuring means reaches a first threshold value. The changing means changes an upper limit of measured values for which photons can be counted for at least one or more of the plurality of pixels.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a photoelectric conversion device including a photoelectric conversion unit that outputs a signal according to incident photons, an imaging device, a control method, a computer program, and the like. [Background technology]

[0002] In recent years, a photoelectric conversion device has been proposed that digitally counts the number of photons incident on an avalanche photodiode and outputs the counted value from a pixel as a photoelectrically converted digital signal. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent Publication No. 2015 / 0163429 Summary of the Invention [Problem to be solved by the invention]

[0004] Patent Document 1 proposes a structure that includes a photon counter that counts photons and a time counter that measures time. The time counter measures the time from when the photon counter starts measuring until the number of photons reaches a predetermined value, and calculates the pixel value from the measured time. However, Patent Document 1 requires a photon counter and a time counter for each pixel, which increases the circuit size.

[0005] The present invention has been made in view of the above problems, and has as its object to provide a technique for performing pixel readout processing in an appropriate manner while suppressing an increase in circuit scale. [Means for solving the problem]

[0006] The photoelectric conversion device according to the present invention, which solves the above-mentioned problems, is a photoelectric conversion device having pixels each equipped with a photoelectric conversion unit that outputs a signal in response to incident photons, and includes: a first measurement means for measuring the number of photons incident on the pixel; a second measurement means for measuring the time from when the first measurement means starts the measurement until the measurement value of the first measurement means reaches a first threshold; and a change means for changing the upper measurement limit at which photons can be counted for at least one pixel among the plurality of pixels. The change means changes the measurement upper limit value of the pixel corresponding to the first measurement means having the largest measurement value among the plurality of first measurement means so as to increase the measurement upper limit value. do. [Effects of the Invention]

[0007] The present invention provides a technique for performing pixel readout processing in an appropriate manner while suppressing an increase in circuit scale. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating an example of a hardware configuration of a photoelectric conversion device. [Figure 2] FIG. 1 is a diagram showing an example of a sensor chip of a photoelectric conversion device. [Figure 3] 1 is a diagram showing an example of a circuit chip of a photoelectric conversion device; [Figure 4] FIG. 1 is a diagram showing an example of an equivalent circuit of a pixel and a signal processing unit in a photoelectric conversion device; [Figure 5] 1 is a timing chart showing the operation of a photoelectric conversion device; [Figure 6] FIG. 1 is a diagram showing an example of a sensor chip of a photoelectric conversion device. [Figure 7] 1 is a flowchart illustrating an example of the operation of a photoelectric conversion device. [Figure 8] FIG. 1 is a diagram illustrating an example of the operation of a photoelectric conversion device. [Figure 9] Schematic diagram showing an example of a photon counter counting method [Figure 10] FIG. 1 is a block diagram illustrating an example of the functional configuration of an imaging device including a photoelectric conversion device. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes in detail embodiments of the present invention. Note that the embodiments described below are examples for realizing the present invention, and should be modified or changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions, and the present invention is not limited to the following embodiments. Furthermore, parts having the same functions in all figures are designated by the same numerals, and repeated explanations thereof are omitted.

[0010] First Embodiment Before describing the means for solving the problems, the configuration of the photoelectric conversion device according to the present invention will be described first.

[0011] 1 is a diagram showing an example of the configuration of a photoelectric conversion device according to this embodiment. The photoelectric conversion device 100 is configured by stacking and electrically connecting two chips: a sensor chip 11 and a circuit chip 21. The sensor chip 11 includes a pixel region 12 having a plurality of pixels. The circuit chip 21 includes a pixel circuit region 22 that processes signals detected by each pixel in the pixel region 12 in parallel, and a peripheral circuit region 23 that reads out signals from the pixel circuit region 22.

[0012] FIG. 2 is a diagram showing an example of the configuration of the sensor chip 11. The pixel region 12 of the sensor chip 11 includes a plurality of pixels 101 arranged two-dimensionally across multiple rows and columns. Each pixel 101 has a photoelectric conversion unit 102 including an avalanche photodiode (hereinafter referred to as APD) that outputs a signal in response to incident photons. FIG. 2 shows 36 pixels 101 arranged in six rows from row 0 to row 5 and six columns from column 0 to column 5, along with reference symbols indicating the row and column numbers. For example, the unit pixel 11 arranged in the first row and fourth column is labeled "P14." The number of rows and columns of the pixel array constituting the pixel region 12 is not particularly limited.

[0013] 3 is a diagram showing an example of the configuration of the circuit chip 21. The circuit chip 21 includes a pixel circuit region 22 and a peripheral circuit region .

[0014] The pixel circuit region 22 includes a plurality of signal processing units 103 arranged two-dimensionally across a plurality of rows and columns. FIG. 3 shows 36 signal processing units 103 arranged in six rows (rows 0 to 5) and six columns (columns 0 to 5), with reference numerals indicating the row and column numbers. For example, the signal processing unit 103 arranged in the first row and fourth column is assigned the reference numeral "S14." The number of rows and columns of the signal processing unit array constituting the pixel circuit region 22 is not particularly limited.

[0015] The peripheral circuit region 23 includes a vertical scanning circuit 110, a column circuit 112, a horizontal scanning circuit 111, a control pulse generating unit 115, and a signal output circuit 114. A vertical selection line 116VSEL is arranged in each row of the signal processing unit array in the pixel circuit region 22, extending in a first direction (the horizontal direction in FIG. 3). The vertical selection line 116VSEL is connected to each of the signal processing units 103 arranged in the first direction and forms a signal line. The first direction in which the vertical selection line 116VSEL extends may be referred to as the row direction or the horizontal direction. Note that in FIG. 3, the vertical selection line VSEL is shown together with a symbol indicating the row number. For example, the vertical selection line in the first row is labeled "VSEL[1]." The vertical selection line 116VSEL in each row is connected to the vertical scanning circuit 110. The vertical scanning circuit 110 supplies a vertical selection signal for selectively driving the signal processing unit 103 to the signal processing unit 103 via a vertical selection line 116VSEL. In this embodiment, the vertical selection line 311 is divided into a readout vertical selection line 214 for reading out signals from the plurality of signal processing units 301 in each row and a reset vertical selection line 213 for resetting signals from the plurality of signal processing units 301 in each row.

[0016] In each column of the signal processing unit array of the pixel circuit region 22, a vertical signal line 113 is arranged, extending in a second direction (the vertical direction in FIG. 3 ) intersecting the first direction. The vertical signal line 113 is connected to each of the signal processing units 103 arranged in the second direction and forms a common signal line. The second direction in which the vertical signal lines 113 extend may be referred to as the column direction or the vertical direction. Note that in FIG. 3 , the vertical signal lines 113 are shown together with a symbol indicating the column number. For example, the signal line 113 in the fourth column is labeled "POUT4." Each vertical signal line 113 in each column includes n signal lines for outputting an n-bit digital signal. The vertical signal lines 113 are connected to a horizontal scanning circuit 112. The horizontal scanning circuit 112 is provided corresponding to each column of the signal processing unit array of the pixel circuit region 22 and is connected to the vertical signal line 113 of the corresponding column. The column circuit 112 has a function of holding a signal read out from the signal processing unit 103 via a vertical signal line 113 of the corresponding column.

[0017] The horizontal scanning circuit 111 supplies horizontal selection signals to the column circuits 112 for reading out signals from the column circuits 112. The horizontal scanning circuit 111 supplies the horizontal selection signals to the column circuits 112 of each column via horizontal selection lines 117HSEL. The column circuits 112 that receive the horizontal selection signals from the horizontal scanning circuit 111 sequentially output the signals they hold to the output circuits 114 via horizontal output lines 117. Note that in FIG. 3, the horizontal selection lines HSEL are shown together with symbols indicating the column numbers. For example, the horizontal selection line for the fourth column is labeled "HSEL[4]." The horizontal output line HSIG has n signal lines for outputting n-bit digital signals.

[0018] The output circuit 114 outputs a signal corresponding to the pixel signal as an output signal SOUT of the photoelectric conversion device.

[0019] The control pulse generation unit 115 supplies control pulse signals that control the operations and timings of the vertical scanning circuit 110, the horizontal scanning circuit 111, and the column circuit 112. Note that at least some of the control pulse signals that control the operations and timings of the horizontal scanning circuit 110, the horizontal scanning circuit 111, and the column circuit 112 may be supplied from outside the photoelectric conversion device.

[0020] 4 shows an example of an equivalent circuit and a block diagram of the pixel 101 in FIG. 2 and the signal processing unit 103 in FIG. 3. The pixel 101 in the sensor chip 11 includes an APD 201, which is a photoelectric conversion unit. When light is incident on the APD 201, a charge pair corresponding to the incident light is generated by photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD 201. A voltage VH (second voltage) higher than the voltage VL supplied to the anode is supplied to the cathode of the APD 201. A reverse bias voltage is supplied to the anode and cathode so that the APD 201 performs avalanche multiplication. With such a voltage supplied, charges generated by the incident light undergo avalanche multiplication, generating an avalanche current.

[0021] When a reverse bias voltage is supplied, there are two modes: Geiger mode, in which the potential difference between the anode and cathode is greater than the breakdown voltage, and linear mode, in which the potential difference between the anode and cathode is close to or less than the breakdown voltage. APDs operating in Geiger mode are called SPADs (Single Photon Avalanche Diodes). For example, the voltage VL (first voltage) is -30V, and the voltage VH (second voltage) is 1V.

[0022] The signal processing unit 103 in the sensor chip 21 includes a quench element 202 , a waveform shaping unit 210 , a photon counter circuit 211 , and a selection circuit 212 .

[0023] The quench element 202 is connected to a power supply that supplies a voltage VH and the APD 201. The quench element 202 has a function of converting a change in avalanche current generated in the APD 201 into a voltage signal. The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, and suppresses the voltage supplied to the APD 201 to suppress avalanche multiplication (quench operation).

[0024] The waveform shaping unit 210 shapes the potential change of the cathode of the APD 201 obtained when a photon is detected, and outputs a pulse signal. The waveform shaping unit 210 may be, for example, an inverter circuit or a buffer circuit.

[0025] FIG. 5 is a timing chart for explaining the operations of the APD and the waveform shaping unit.

[0026] 5(a) shows the voltage change at node A in FIG. 4, and FIG. 5(b) shows the voltage change at node B in FIG.

[0027] Between times t0 and t1, a voltage of VH-VL is applied to the APD 201 in FIG. 4 . At this time, the voltage at node B is low. When a photon is incident on the photoelectric conversion unit at time t1, an avalanche multiplication current flows through the quench element 202, causing the voltage at node A to drop. When the voltage at node A falls below a predetermined threshold at time t2, the waveform shaping unit 210 causes the voltage at node B to change from low to high. At time t3, the voltage drop increases further, causing the voltage applied to the APD 201 to decrease. This stops avalanche multiplication in the APD 201, and the voltage at node A no longer drops below a certain value. After that, a current flows from voltage VL to node A to compensate for the voltage drop, causing the voltage to rise. At time t4, when the voltage at node A exceeds a predetermined determination threshold, the voltage at node B changes from High to Low due to the function of the waveform shaping section 210. At time t3, node A is stabilized at its original potential level.

[0028] Although one photon counter is shown for each pixel, in reality, some photon counters span multiple pixels. Details will be described later. The photon counter circuit 211 (first measurement means) is a photon counter that measures the number of photons incident on the pixel. It counts the pulse signal output from the waveform shaping unit 210, for example, up to a first threshold Cx (a predetermined upper limit value). The photon counter circuit 211 (photon counter) also resets its count value when a predetermined control signal PRES is supplied via a control line 213. The photon counter circuit 211 also stops its counting operation based on the output of a time-to-digital converter (TDC) circuit (described later). The photon counter circuit 211 includes a TDC circuit (second measurement means) for stopping its counting operation. The time photon counter circuit (TDC circuit) measures the time from when the photon counter circuit 211 starts measurement until the measurement value (measured value) reaches the first threshold Cx, and outputs the measured time as a pixel value.

[0029] To solve the above-mentioned problems that arise when a TDC circuit (time counter) is connected to only one of multiple pixels, it is necessary to prevent the photon counter circuit 211 from saturating before the TDC circuit outputs. Therefore, by observing the output value of the photon counter circuit 211 once or multiple times before the TDC circuit outputs, and connecting an additional photon counter (extended photon counter circuit) so that the photon counter circuit connected to the TDC circuit saturates the earliest, the frequency with which the photon counter circuit not connected to the TDC circuit saturates can be reduced. The circuit configuration required for implementation will be described first, followed by a detailed description of the operation.

[0030] FIG. 6 shows an example of the detailed arrangement of the signal processing unit 211 in a multi-pixel unit (partial pixel region). Here, a partial pixel region having multiple pixels (e.g., four pixels) is treated as a single unit. A shared counter 603, which counts the number of photons incident on any one of the multiple pixels, is arranged for each of multiple photosensitive unit groups (A00, A01, A10, and A11 in this example), similar to the photon counter circuit 211. Furthermore, the shared counter 603 is connected to each pixel in an exclusive and switchable manner so that it can receive pulse signals generated by all of the photosensitive units in the multiple photosensitive unit groups. A measurement value comparison circuit 604 is arranged between the photon counter circuit 211 and the selection circuit 212 and switches the electrical connection between the shared counter 603 and the pixels in the multiple photosensitive unit groups.

[0031] Each of the photosensitive units A00, A01, A10, and A11 is composed of a sensor chip 11, a quench element 202, and a waveform shaping unit 210, and the output of each is connected to a photon counter circuit group 211s. The photon counter circuit group 211s is composed of photon counter circuits 601A, 601B, 601C, and 601D (hereinafter, simply referred to as 601 when referring to all 601A to 601D) that are dedicated to each of the photosensitive units, which are photon counter circuits 211 within a multi-photosensitive unit, a shared counter 603, a measurement value comparison circuit 604, and a TDC circuit 602 that is connected only to a single photon counter circuit 601 within the photon counter circuit group 211s.

[0032] The TDC circuit 602 is connected to one of the photon counter circuits 601 (here, photon counter circuit 601A) in the photon counter circuit group 211s, which includes multiple photon counters. When the output of the photon counter circuit 601A reaches a certain threshold, the TDC circuit 602 transitions its output signal to high level to stop the counting operation of the photon counter circuit 601 and its own time measurement operation. When a control signal PRES is supplied via control line 213, the TDC circuit 602 resets its output signal to low level. The output signal of the TDC circuit 602 is connected to the photon counter circuit 601 and the shared photon counter circuit 603, and when the output signal is high level, it stops the counter operations of these circuits. The TDC circuit 602 also outputs a time measurement value measured by the TDC circuit 602 simultaneously with, or instead of, outputting the count value of the pixel to which the TDC circuit 602 is connected in response to control signals 113 and 214. This time measurement value is used for conversion by a photon count value-to-pixel value restoration circuit, which may be connected downstream.

[0033] For example, the measurement value comparison circuit references the upper two bits of the photon counters 601A-601D in the output of the photon counter circuit 601. When one of the photon counters 601A-601D indicates [1,1] (saturation), the measurement value comparison circuit increases the number of bits (measurement upper limit) allocated to the photosensitive element AXX (where XX is 00, 01, 10, or 11) connected to the photon counter that indicated saturation, and decreases the number of bits allocated to other photosensitive elements that did not indicate saturation. Details of the bit number allocation operation will be described later using a specific example. When decreasing the number of bits allocated to other photosensitive elements, it is preferable to reduce the number of bits when there is no value, as this allows the allocation to be changed without losing the counting result. The allocation of the shared counter 603 is performed by expanding the most significant bit of the photon counter. Furthermore, the photon counting result of a certain photosensitive element is indicated by the output of the photon counter 601 and the shared counter 603 connected to the same photosensitive element. The shared counter 603 includes, for example, a memory circuit for switching the connection state based on an input signal and maintaining that state. With the above configuration, the photon counter circuit connected to the TDC circuit can be controlled so that it saturates earliest within the unit pixel, thereby improving the possibility of more accurate photon counting of the subject.

[0034] The selection circuit 212 switches between electrical connection and disconnection between the photon counter circuit 211 and the signal line 113 in response to a vertical selection signal VSEL supplied from the vertical scanning circuit 110 in FIG. 3 via a control line 214. The connected photon counter circuit 211 transfers the counted measurement value or the time measurement value measured by the TDC circuit 602. Here, the counted measurement value is the counting result including both the photon counter 601 and the shared counter 603 connected to the same pixel. The selection circuit 212 includes, for example, a buffer circuit for outputting a signal.

[0035] FIG. 7 is a flowchart of the operation of the photoelectric conversion device to prevent saturation of pixels other than those connected to the TDC circuit when an exposure is performed. In the following description, each process (step) is denoted by prefixing it with an S, and the process (step) is omitted. In S700, the photon counter circuit 211 starts counting photons based on some operation. In S701, the shared counter assigns the upper measurement limit value of each photon counter in the initial state. For example, if the shared counter has four bits, one bit may be assigned to each of the four pixels, or all of the bits may be left unconnected (unassigned). In S702, the time counter (TDC circuit) determines whether it is time for comparison. For example, as described above, the upper two bits of the output of each photon counter circuit may be monitored, and if any pixel becomes saturated, the comparison may be triggered and the process may proceed to S703. Alternatively, the comparison may be triggered simply after a certain period of time has elapsed. In S703, the measurement value comparison circuit compares the output values ​​of each photon counter circuit. Based on the calculation result of S703, in S704, the shared counter changes the connection state of each photon counter. Then, in S705, the photon counters continue counting photons for each unit pixel until the number of photons reaches a respective set upper measurement limit. When the measurement value of the photon counter connected to the TDC circuit reaches the upper measurement limit (first threshold Cx), the process proceeds to S706. In S706, each photon counter stops counting photons and outputs the photon count value and time measurement value at that time. While the example of the measurement value of the photon counter connected to the TDC circuit reaching the upper measurement limit (first threshold Cx) was used to advance from S705 to S706, the counting operation may also be forcibly stopped after a certain elapsed time (first predetermined time) from the start of exposure based on the time measurement value of the time counter, even if the counting operation is not saturated, and the photon count value and time measurement value at that time may be output.

[0036] The allocation operation of the shared counter (third measurement means) will be described below using a specific example. The shared counter (third measurement means) counts the number of photons incident on at least one of the multiple pixels included in the partial pixel region. In other words, it is a photon counter shared among multiple pixels. The shared counter (third measurement means) can count the number of photons up to a predetermined value, such as 8 bits. For example, if the upper limit of the photon counter corresponding to a pixel is exceeded, a shared counter can be assigned in advance to measure the number of photons beyond the predetermined upper limit of the photon counter. FIG. 8 is an example showing the elapsed time and the number of photons counted when an exposure is performed. FIG. 9 is a schematic diagram showing an example of the measurement values ​​of the counters assigned to each pixel when the shared counters are reallocated. For example, each photosensitive element in FIG. 6 has a so-called color filter, and A00 is a Gb pixel, A01 is a B pixel, A10 is an R pixel, and A11 is a Gr pixel. In this diagram, Gr and Gb are collectively referred to as G, since they have approximately the same sensitivity, and bit allocation (deletion and addition) is performed equally. Each photon counter circuit 601 has, for example, 6 bits, and the shared counter 603 has a total of 8 bits. Initially, two bits of the shared counter 603 are connected to each photon counter circuit 601 (top diagram of Figure 9). In other words, the upper measurement limit value of the photon counter corresponding to each pixel is increased by a predetermined value by the shared counter. The TDC circuit 602 is also connected to the photon counter 601A connected to the photosensitive unit A00, i.e., the Gb pixel. After exposure, the upper two bits of the photon counter circuit output are monitored, and the output of each photon counter circuit is compared when saturation [1,1] is reached. Based on the results, the connection state to the shared counter 603 is switched (bottom diagram of Figure 9). When switching, the most significant bit of the photon counter circuit 601 connected to the photosensitive unit is expanded, as shown in the bottom diagram of Figure 9.

[0037] Table 1 shows conditions for switching the connection state to the shared counter 603 and examples thereof, and (a), (b), and (c) in the table correspond to those in FIG. [Table 1]

[0038] In the example of FIG. 8(a), it is estimated that the G pixel connected to the TDC circuit will saturate first (the photon count value will reach the upper limit). Therefore, it is estimated that the TDC circuit will stop the photon counter of the G pixel first, even without reallocating the bits of the shared counter 603. Therefore, the bits of the shared counter 603 are not reallocated. In the example of FIG. 8(c), the G count value is the lowest. In this case, the bits of the shared counter assigned to G are reassigned to R and B. In this way, reducing the G counter bit width can speed up the TDC circuit's stop of the photon counter of the G pixel, preventing pixels not connected to the TDC circuit from saturating before the TDC circuit stops the photon counter of the G pixel. As a result, the possibility of more accurate photon counting of the subject is improved. In the example of FIG. 8(b), it is estimated that the R pixel will saturate first, so the bits of the shared counter assigned to the G pixel connected to the TDC circuit are reassigned to the R pixel. In FIG. 8(b), unlike the case of FIG. 8(c), the bit allocation of the shared counter connected to the B pixel that shows a count value less than G does not need to be increased.

[0039] Table 2 shows a generalized relationship between these. For example, if the count value of the photon counter connected to the TDC circuit is denoted as α and the count values ​​of the other photon counters as β and γ, respectively, the bits of the shared counter can be assigned as shown in the formula below. Here, A and B are any integers, and N is the value obtained by dividing the bits of the shared counter by the number of pixels in the unit pixel (e.g., when the shared counter is 8 bits and the unit pixel is 4, N = 2). Note that the order of the values ​​of β and γ is arbitrary. First, the shared counter circuit connected to the TDC circuit should be assigned so that it saturates faster than any of the other photon counter circuits. It is more desirable to assign the shared counter circuits so that the difference between the photon counter circuits not connected to other TDC circuits is minimized, i.e., so that the difference between (2^A)β and (2^A)γ is smallest.

[0040] [Table 2]

[0041] In this way, the connection state of the shared counter is changed, and then in S705, the system waits for the TDC circuit to operate. Once the TDC circuit operates, the counter operation is stopped in S706, and the exposure operation is completed. Thereafter, the selection circuit 212, control line 214, etc. output pixel values ​​acquired based on the measurement values ​​of the photon counter or the time counter.

[0042] In this embodiment, one measurement value comparison circuit 604 is provided for every four photosensitive sections (i.e., one partial pixel area), but it is also possible to provide one for every pixel and switch the connection using the selection circuit 212 and control lines 113 and 214. In other words, the measurement value comparison circuits may be connected in the same way as the vertical and horizontal scanning lines of pixel output operate, and the measurement value comparison operation may be performed. In this example, there is no need to provide a measurement value comparison circuit for each pixel, which is advantageous in terms of circuit size.

[0043] Furthermore, the bit allocation operation of the shared counter circuit can be initiated by the TDC circuit referring to the entire output of the photon counter circuit, rather than just the most significant two bits. This example increases the circuit size, but allows for more accurate bit allocation of the shared counter, which is advantageous in that it minimizes the reduction in image quality caused by reducing bit allocation. Alternatively, a separate time measurement can be used, and the operation can be performed after a certain period of time has elapsed. In this example, the method using the vertical and horizontal scan lines described above is particularly effective; for example, if a certain period of time is set as the saturation time of the previous frame, power consumption can be reduced while maintaining image quality.

[0044] <Imaging device> FIG. 5 is a block diagram of an imaging device 500 using the photoelectric conversion device 100.

[0045] The imaging device 500 is, for example, a digital camera, and is an imaging device that includes the photoelectric conversion device 100, and includes a lens 501, an image processing unit 502, an optical control unit 503, a memory unit 504, and a wireless I / F (Interface) unit 505 as a communication unit.

[0046] The lens 501 forms an optical image of a subject and transmits the formed optical image to the imaging surface of the photoelectric conversion device 100, which is equipped with a focus lens, a zoom lens, an aperture, and the like. The photoelectric conversion device 100 captures the optical image formed by the lens 501. Signals read from the photoelectric conversion device 100 are output to an image processing unit 502. The image processing unit 502 performs processing on the signals output from the photoelectric conversion device 100, such as signal rearrangement, defective pixel correction, noise reduction, color conversion, white balance correction, gamma correction, and data compression, to generate an image. The image processing unit 502 incorporates a CPU as a computer and functions as a control unit that controls the operation of each component of the entire imaging device 500 based on a computer program stored in a memory as a storage medium. The optical control unit 503 controls the focus lens, zoom lens, aperture, and the like provided in the lens 501. A recording medium (not shown) is attached to the recording unit 504, which stores the image output from the image processing unit in the storage medium. Such a recording medium may be, for example, a memory card. Alternatively, a hard disk may be used as the recording medium. A wireless I / F (Interface) unit 505 serving as a communication unit outputs the image signal generated by the image processing unit 502 to the outside of the imaging device 500. Reference numeral 506 denotes a network, which is composed of, for example, a plurality of routers, switches, cables, etc. that satisfy a communication standard such as Ethernet (registered trademark), and a client controls the imaging device 500 via the network 506.

[0047] <Other embodiments> In the embodiment, the imaging device is described as being a digital camera, but the imaging device also includes electronic devices with imaging capabilities, such as digital movie cameras, smartphones with cameras, tablet computers with cameras, in-vehicle cameras, drone cameras, cameras mounted on robots, and network cameras.

[0048] The present invention has been described in detail above based on its preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications are possible based on the gist of the present invention, and these modifications are not excluded from the scope of the present invention.

[0049] Note that a computer program that realizes part or all of the control in this embodiment and the functions of the above-described embodiment may be supplied to a photoelectric conversion device, an imaging device, or the like via a network or various storage media. Then, a computer (or a CPU, MPU, or the like) in the photoelectric conversion device, imaging device, or the like may read and execute the program. In this case, the program and the storage medium storing the program constitute the present invention. [Explanation of symbols]

[0050] 100 Photoelectric conversion device 500 Imaging device 501 Lens 502 Image processing unit 503 Optical control unit 504 Storage section 505 I / F section

Claims

1. A photoelectric conversion device having pixels each including a photoelectric conversion unit that outputs a signal in response to an incident photon, a first measuring means for measuring the number of photons incident on the pixel; a second measuring means for measuring the time from when the first measuring means starts the measurement until the measured value of the first measuring means reaches a first threshold value; a change unit that changes an upper measurement limit at which photons can be counted for at least one of the plurality of pixels, The photoelectric conversion device is characterized in that the change means changes the measurement upper limit value of the pixel corresponding to the first measurement means having the largest measurement value among the plurality of first measurement means so as to make it larger.

2. 2. The photoelectric conversion device according to claim 1, wherein the change means changes the measurement upper limit value to a larger value for the pixel corresponding to the first measurement means whose measurement value has reached a first threshold value.

3. a third measuring means for counting the number of photons for at least one pixel among the plurality of pixels included in the partial pixel region; 3. The photoelectric conversion device according to claim 1, wherein the change unit changes the upper measurement limit by associating the third measurement unit with any one of the plurality of pixels.

4. 4. The photoelectric conversion device according to claim 3, wherein the third measurement means counts photons up to a predetermined upper limit for each of the pixels included in the partial pixel region.

5. The photoelectric conversion device according to claim 4, characterized in that the change means determines the pixel for which the predetermined upper limit value is to be changed based on the measurement values ​​of the first measurement means corresponding to each of the pixels included in the partial pixel area.

6. The photoelectric conversion device according to claim 5, wherein the change means compares the measurement values ​​of the first measurement means corresponding to each of the pixels included in the partial pixel area, and changes the measurement upper limit value of the third measurement means for the pixel corresponding to the first measurement means having the larger measurement value.

7. 7. The photoelectric conversion device according to claim 3, further comprising an output unit that outputs the measurement value of the first measurement unit, the measurement value of the second measurement unit, or the measurement value of the third measurement unit.

8. The photoelectric conversion device according to claim 7, characterized in that the output means outputs the measurement values ​​of the first measurement means corresponding to each of the plurality of pixels, excluding the measurement values ​​of the first measurement means that have reached the first threshold, and the measurement values ​​of the second measurement means.

9. The photoelectric conversion device according to claim 7 or 8, characterized in that the output means outputs a single signal that combines the measurement value of the first measurement means and the measurement value of the second measurement means included in a partial pixel area consisting of a plurality of the pixels.

10. A photoelectric conversion device having pixels each having a photoelectric conversion unit that outputs a signal in response to incident photons, a first measuring means for measuring the number of photons incident on the pixel; a second measuring means for measuring the time from when the first measuring means starts the measurement until the measured value of the first measuring means reaches a first threshold value; a change unit that changes an upper measurement limit at which photons can be counted for at least one of the plurality of pixels, the second measuring means is arranged for each partial pixel region made up of a plurality of the pixels having different spectral sensitivities, The photoelectric conversion device is characterized in that the first measurement means is disposed in each of the plurality of pixels that constitute the partial pixel region.

11. 11. The photoelectric conversion device according to claim 1, further comprising a signal restoration means for restoring a pixel signal based on a measurement value by the first measurement means corresponding to each pixel or a time measurement value by the second measurement means.

12. 12. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion unit includes an avalanche photodiode for detecting incident photons.

13. An imaging device comprising the photoelectric conversion device according to claim 1 .

14. A control method for controlling a photoelectric conversion device having pixels each including a photoelectric conversion unit that outputs a signal in response to incident photons, a first measurement means that measures the number of photons incident on the pixel, and a second measurement means that measures a time period from when the first measurement means starts the measurement until a measurement value of the first measurement means reaches a first threshold, the method comprising: a changing step of changing an upper measurement limit value capable of counting photons for at least one pixel among the plurality of pixels, A control method characterized in that, in the change step, the measurement upper limit value of the pixel corresponding to the first measurement means having the largest measurement value among the plurality of first measurement means is changed to be larger.

15. A computer program for controlling each unit of the photoelectric conversion device according to any one of claims 1 to 12 or the imaging device according to claim 13 by a computer.

Images