JP2025118157A - Photoelectric conversion device, photoelectric conversion system, and mobile body - Google Patents

Abstract

To provide a technology advantageous for obtaining a high quality image in a photoelectric conversion device having a plurality of pixels for counting photons and outputting a count value.SOLUTION: According to the present invention, a photoelectric conversion device having a plurality of pixels for counting photons and outputting a count value includes: a memory; a first arithmetic unit for generating a first arithmetic value by multiplying the count value generated in each pixel by a first coefficient; a second arithmetic unit for generating a second arithmetic value by multiplying data provided from the memory by a second coefficient; an adder for adding the first arithmetic value and the second arithmetic value to generate an addition value; and a memory controller for updating the data stored in the memory according to the addition value. The number of bits of the first arithmetic value generated by the first arithmetic unit is larger than the number of bits of the count value.SELECTED DRAWING: Figure 6

Description

The present invention relates to a photoelectric conversion device, a photoelectric conversion system, and a mobile object.

Patent document 1 describes a configuration in which each pixel has an avalanche photodiode (APD), a waveform shaping unit that shapes the output signal of the APD to generate a detection signal, a counting unit that counts the detection signals, and an IIR filter that processes the counting results from the counting unit.

Japanese Patent Application Laid-Open No. 2021-044636

In an IIR filter, if the number of bits in the data indicating the counting result output from the counting unit is the same as the number of bits in the adder, some of the image information (e.g., information after the decimal point) will be lost, making it difficult to obtain a high-quality image.

The present invention aims to provide an advantageous technology for obtaining high-quality images in a photoelectric conversion device having multiple pixels that count photons and output count values.

One aspect of the present invention relates to a photoelectric conversion device having a plurality of pixels that count photons and output count values, the photoelectric conversion device comprising: a memory; a first calculator that multiplies the count value generated in each pixel by a first coefficient to generate a first calculation value; a second calculator that multiplies data provided from the memory by a second coefficient to generate a second calculation value; an adder that adds the first calculation value and the second calculation value to generate a sum; and a memory controller that updates data stored in the memory according to the sum, wherein the number of bits of the first calculation value generated by the first calculator is greater than the number of bits of the count value.

The present invention provides an advantageous technique for obtaining high-quality images in a photoelectric conversion device having multiple pixels that count photons and output count values.

FIG. 1 is a diagram showing a basic configuration of a photoelectric conversion device according to an embodiment. FIG. 2 is a diagram showing a configuration example of a sensor substrate. FIG. 2 is a diagram showing an example of the configuration of a circuit board. FIG. 2 is an equivalent circuit diagram of one pixel and its signal processing unit. 3A to 3C are diagrams illustrating the operation of a pixel. FIG. 2 is a diagram showing the configuration of an image processing unit in the photoelectric conversion device according to the first embodiment. 5A to 5C are diagrams illustrating the operation of the photoelectric conversion device according to the first embodiment. 5A and 5B are diagrams illustrating the operation of an image processing unit in the photoelectric conversion device according to the first embodiment. FIG. 10 is a diagram showing the configuration of an image processing unit in a photoelectric conversion device according to a second embodiment. FIG. 10 is a diagram showing the configuration of an image processing unit in a photoelectric conversion device according to a third embodiment. 10A to 10C are diagrams illustrating the operation of a photoelectric conversion device according to a third embodiment. FIG. 10 is a diagram illustrating the operation of an image processing unit in the photoelectric conversion device according to the fourth embodiment. FIG. 13 is a diagram illustrating the operation of an image processing unit in a photoelectric conversion device according to a fifth embodiment. 13A and 13B are diagrams illustrating the operation of an image processing unit in a photoelectric conversion device according to a sixth embodiment. FIG. 10 is a diagram showing a modified example of the first computing unit. FIG. 10 is a diagram showing a specific example of a data converter in the first computing unit. FIG. 4 is a diagram schematically illustrating the operation of a bit width expanding unit. FIG. 4 is a diagram illustrating the operation of a nonlinear correction unit. FIG. 4 is a diagram illustrating the operation of a smoothing processing unit. FIG. 13 is a diagram showing the configuration of a photoelectric conversion system according to a seventh embodiment. FIG. 10 is a diagram showing a first application example. FIG. 10 is a diagram showing a second application example. FIG. 10 is a diagram showing a third application example. FIG. 10 is a diagram showing a fourth application example. FIG. 10 is a diagram showing a fifth application example. FIG. 10 is a diagram showing a sixth application example. FIG. 13 is a diagram showing a seventh application example.

The following describes the embodiments in detail with reference to the attached drawings. Note that the following embodiments do not limit the scope of the claimed invention. While the embodiments describe multiple features, not all of these features are necessarily essential to the invention, and multiple features may be combined in any desired manner. Furthermore, in the attached drawings, the same reference numbers are used to designate identical or similar components, and redundant explanations will be omitted.

In this specification, a planar view refers to viewing the photoelectric conversion device from a direction perpendicular to the light incident surface of the semiconductor layer, and is synonymous with an orthogonal projection onto the light incident surface. Furthermore, a cross-sectional view refers to a surface in a direction perpendicular to the light incident surface of the semiconductor layer. Note that if the light incident surface of the semiconductor layer is rough when viewed microscopically, the planar view is defined based on the light incident surface of the semiconductor layer when viewed macroscopically.

The present invention can be applied to a photoelectric conversion device having multiple pixels that count photons and output count values. As an example of such a photoelectric conversion device, a photoelectric conversion device in which each pixel has an avalanche photodiode (hereinafter also referred to as an APD) will be described below. However, the present invention can also be applied to other photoelectric conversion devices, such as a photoelectric conversion device called an EMCCD or a photoelectric conversion device that includes a scintillator.

In the following description of exemplary embodiments, the anode of the avalanche photodiode (APD) is held at a fixed potential, and the signal is extracted from the cathode side. Therefore, the first conductivity type semiconductor region in which charges of a first polarity, the same as the signal charge, are the majority carriers is an N-type semiconductor region, and the second conductivity type semiconductor region in which charges of a second polarity, different from the signal charge, are the majority carriers is a P-type semiconductor region. Note that the present invention also applies when the cathode of the APD is held at a fixed potential and the signal is extracted from the anode side. In this case, the first conductivity type semiconductor region in which charges of a first polarity, the same as the signal charge, are the majority carriers is a P-type semiconductor region, and the second conductivity type semiconductor region in which charges of a second polarity, different from the signal charge, are the majority carriers is an N-type semiconductor region. The following description will be given of a case in which one node of the APD is held at a fixed potential, but the potentials of both nodes may fluctuate.

First, the basic configuration and driving method common to the photoelectric conversion devices and driving methods of the multiple embodiments described below will be described with reference to Figures 1, 2, 3, 4, and 5.

Figure 1 illustrates the basic configuration of a photoelectric conversion device 100 according to an embodiment. Here, an example is described in which the photoelectric conversion device 100 is configured as a stacked-type photoelectric conversion device. However, the present invention is also applicable to photoelectric conversion devices other than stacked-type photoelectric conversion devices. The photoelectric conversion device 100 can be configured, for example, by stacking multiple substrates, including a sensor substrate 11 and a circuit substrate 21, and electrically connecting the multiple substrates. The sensor substrate 11 can have a first semiconductor layer having a photoelectric conversion element 102 (described below) and a first wiring structure. The circuit substrate 21 can have a second semiconductor layer having circuits such as an intra-pixel processing unit 103 (described below) and a second wiring structure. The photoelectric conversion device 100 can be configured, for example, by stacking the second semiconductor layer, the second wiring structure, the first wiring structure, and the first semiconductor layer in this order. The photoelectric conversion device 100 described in the following embodiment can be, for example, a back-illuminated photoelectric conversion device. However, the photoelectric conversion device according to the present invention can also be configured as a front-illuminated photoelectric conversion device.

The sensor substrate 11 may include a semiconductor layer including a pixel array region 12 having a plurality of pixels and a peripheral region 13 arranged around the pixel array region 12. The region between the outer edge of the pixel array region 12 and the outer edge of the sensor substrate 11 (the scribe region including the outer edge) may be the peripheral region 13. Circuit elements such as active elements may or may not be arranged in the peripheral region 13. The circuit substrate 21 may include a semiconductor layer including a circuit region 22 that processes signals detected by the pixels in the pixel array region 12.

Figure 2 is a diagram showing an example configuration of the sensor substrate 11. In the pixel array region 12, multiple pixels 101 can be arranged in a two-dimensional array to form multiple rows and multiple columns. Each pixel 101 can include a photoelectric conversion element 102 that includes an avalanche photodiode (APD).

The pixels 101 arranged in the pixel array region 12 can be pixels for forming an image. However, when the sensor substrate 11 or the photoelectric conversion device 100 is applied to TOF (Time of Flight), each pixel 101 does not have to be a pixel for forming an image. In other words, the pixel 101 can be a pixel for measuring the time and amount of light that arrives.

Figure 3 is a diagram showing the configuration of the circuit board 21. The circuit board 21 may include, for example, an in-pixel processing unit 103 that processes a signal (electrical signal) generated in response to charge (signal charge) generated by photoelectric conversion in the photoelectric conversion element 102. The circuit board 21 may also include a readout circuit 112, a control pulse generation unit 115, a horizontal scanning circuit 111, signal lines 113, a vertical scanning circuit 110, and an image processing unit 120. One in-pixel processing unit 103 may be provided for one pixel 101. The photoelectric conversion element 102 in Figure 2 and the in-pixel processing unit 103 in Figure 3 may be electrically connected via connection wiring provided for each pixel 101.

The vertical scanning circuit 110 may be configured, for example, to receive a first control pulse supplied from the control pulse generation unit 115, generate a second control pulse, and supply the second control pulse to each pixel 101. The vertical scanning circuit 110 may include logic circuits such as a shift register and an address decoder. The signal output from the photoelectric conversion element 102 of each pixel 101 may be processed by an in-pixel processing unit 103 provided corresponding to that pixel 101. The in-pixel processing unit 103 may include a counter, memory, etc., and the memory may store digital values.

The horizontal scanning circuit 111 may be configured to supply the in-pixel processing unit 103 with a third control pulse that sequentially selects each column in order to read out a signal from the memory of each pixel 101 that holds a digital signal. The circuit board 21 may have multiple signal lines 113. Pixel signals are output to the multiple signal lines 113 from the in-pixel processing unit 103 assigned to the pixels 101 in the row selected by the vertical scanning circuit 110. The pixel signals output to the multiple signal lines 113 may be read out by the readout circuit 112 and sequentially supplied from the readout circuit 112 to the image processing unit 120 under the control of the horizontal scanning circuit 111. The image processing unit 120 performs TIIR filtering on the count values (pixel signals) sequentially supplied from the readout circuit 112, and provides the resulting data to the output unit 114. The output unit 114 may output the data provided by the image processing unit 120 to a recording unit or signal processing unit external to the photoelectric conversion device 100.

In FIG. 2, the photoelectric conversion elements 102 or pixels 101 in the pixel array region 12 may be arranged one-dimensionally. Each intra-pixel processing unit 103 may be assigned to at least two photoelectric conversion elements 102 or pixels 101.

As shown in Figures 2 and 3, multiple intra-pixel processing units 103 may be arranged in a region overlapping the pixel array region 12 in a planar view. Then, the vertical scanning circuit 110, horizontal scanning circuit 111, readout circuit 112, output unit 114, control pulse generation unit 115, and image processing unit 120 may be arranged so as to overlap the region between the outer edge of the sensor substrate 11 and the outer edge of the pixel array region 12 in a planar view. In other words, the vertical scanning circuit 110, horizontal scanning circuit 111, readout circuit 112, output unit 114, control pulse generation unit 115, and image processing unit 120 may be arranged in a region overlapping the peripheral region 13 of the sensor substrate 11 in a planar view.

Figure 4 illustrates an equivalent circuit of one pixel 101 in Figure 2 and one in-pixel processing unit 103 in Figure 3. The photoelectric conversion element 102 includes an APD 201. The APD 201 generates charge pairs in response to incident light through 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 can be supplied to the cathode of the APD 201. A reverse bias voltage (predetermined voltage) that can cause the APD 201 to perform avalanche multiplication can be supplied between the anode and cathode. With such a reverse bias voltage supplied between the anode and cathode, charges generated by incident light can cause avalanche multiplication, generating an avalanche current.

A mode in which an APD is operated with a voltage between the anode and cathode greater than the breakdown voltage is called Geiger mode. A mode in which an APD is operated with a voltage between the anode and cathode close to or less than the breakdown voltage is called linear mode. An APD operated in Geiger mode is called a SPAD. For example, the voltage VL (first voltage) is -30 V and the voltage VH (second voltage) is 1 V. The APD 201 may be operated in either linear mode or Geiger mode.

The quench element 202 can be arranged to connect the APD 201 to a power supply that supplies voltage VH. The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, suppressing the voltage supplied to the APD 201 and suppressing avalanche multiplication (quench operation). The quench element 202 also returns the voltage supplied to the APD 201 to voltage VH by passing a current equivalent to the voltage drop caused by the quench operation (recharge operation).

The intra-pixel processing unit 103 may include a waveform shaping unit 210, a counter circuit 211, and a selection circuit 212. The intra-pixel processing unit 103 may be a circuit including at least one of the waveform shaping unit 210, the counter circuit 211, and the selection circuit 212. The waveform shaping unit 210 may shape the potential change of the cathode of the APD 201 obtained during photon detection and output a pulse signal. The waveform shaping unit 210 may be, for example, an inverter circuit. In FIG. 4, the waveform shaping unit 210 is composed of a single inverter, but the waveform shaping unit 210 may include multiple inverters connected in series, or may include other circuits that have a waveform shaping effect.

The counter circuit 211 can count the pulse signals output from the waveform shaping unit 210 and hold the count value. The counter circuit 211 can also be configured to reset the count value held in the counter circuit 211 when a control pulse pRES is supplied via a drive line 213. The selection circuit 212 can receive a control pulse pSEL from the vertical scanning circuit 110 in FIG. 3 via a drive line 214 in FIG. 4 (not shown in FIG. 3), and can switch between electrical connection and disconnection between the counter circuit 211 and the signal line 113. The selection circuit 212 can include, for example, a buffer circuit for outputting a signal.

Switches such as transistors may be arranged between the quench element 202 and the APD 201 and/or between the photoelectric conversion element 102 and the intra-pixel processing unit 103, and the electrical connection may be controlled by the switches. Similarly, the supply of voltage VH and/or voltage VL to the photoelectric conversion element 102 may be controlled by switches such as transistors.

The photoelectric conversion device 100 may be configured to acquire pulse detection timing using a time-to-digital converter (TDC) and memory instead of the counter circuit 211. The generation timing of the pulse signal output from the waveform shaping unit 210 may be converted into a digital signal by the TDC. To measure the timing of the pulse signal, a control pulse pREF (reference signal) may be supplied to the TDC from the vertical scanning circuit 110 in FIG. 1 via a drive line. The TDC may acquire, as a digital signal, a signal obtained by converting the input timing of the signal output from each pixel via the waveform shaping unit 210 into a relative time based on the control pulse pREF.

Figure 5 is a diagram that schematically illustrates the relationship between the operation of APD 201 and the output signal. Figure 5(a) is a diagram that excerpts APD 201, quench element 202, and waveform shaping unit 210 from Figure 4. Here, the input side of waveform shaping unit 210 is referred to as node A, and the output side is referred to as node B. Figure 5(b) shows the waveform change at node A in Figure 5(a), and Figure 5(c) shows the waveform change at node B in Figure 5(a).

Between time t0 and time t1, a potential difference of VH-VL is applied to APD201 in Figure 5(a). When a photon is incident on APD201 at time t1, avalanche multiplication occurs in APD201, an avalanche multiplication current flows through quench element 202, and the voltage at node A drops. When the voltage drop increases further and the potential difference applied to APD201 decreases, the avalanche multiplication operation of APD201 stops, as at time t2, and the voltage level at node A no longer drops by more than a certain value. Thereafter, between time t2 and time t3, a current flows through node A from voltage VL to compensate for the voltage drop, and at time t3, node A settles to its original potential level. At this time, the portion of the output waveform at node A that exceeds a certain threshold is shaped by the waveform shaping unit 210 and output as a signal at node B.

Note that the arrangement of the signal lines 113, readout circuits 112, output units 114, image processing units 120, etc. is not limited to the arrangement shown in FIG. 3. For example, the signal lines 113 may be arranged to extend in the row direction, and the readout circuits 112 may be arranged at the ends of the signal lines 113.

Several embodiments of the photoelectric conversion device 100 are described below. First, a photoelectric conversion device 100 according to the first embodiment is described. Figure 6 is a diagram showing the configuration of the image processing unit 120 in the photoelectric conversion device 100 according to the first embodiment. A count value can be provided to the image processing unit 120 from each pixel 101 via the signal line 113 and the readout circuit 112. As described above, this count value is obtained by counting photons in the pixel 101. The image processing unit 120 can include, for example, a memory 403, a first computing unit 410, a second computing unit 420, an adder 401, and a memory controller 406. However, at least one of the memory 403, the first computing unit 410, the second computing unit 420, the adder 401, and the memory controller 406 may be located in the pixel 101.

The memory 403 may be composed of, for example, DRAM, SRAM, MRAM, FeRAM, ReRAM, or EEPROM, but may also be composed of, for example, a collection of flip-flops or latch circuits. The memory 403 may constitute a frame memory capable of holding one frame's worth of data. One frame may be composed of data from multiple pixels 101 arranged in the pixel array region 12. The first calculator 410 may be configured to multiply a count value generated in each pixel 101 by a first coefficient (here, (1-α)) to generate a first calculation value and provide the first calculation value to the adder 401. The second calculator 420 may be configured to multiply data provided from the memory 403 (the value held by the memory 403) by a second coefficient (here, α) to generate a second calculation value and provide the second calculation value to the adder 401. In this example, the first coefficient is (1-α), the second coefficient is α, and the sum of the first and second coefficients is 1. However, the first and second coefficients may be independent coefficients that are not correlated with each other. The first coefficient may be a value greater than 0 and less than 1. The second coefficient may be a value greater than 0 and less than 1.

The adder 401 may be configured to add a first calculation value provided by the first calculation unit 410 and a second calculation value provided by the second calculation unit 420 to generate an addition value. The memory controller 406 may be configured to update data stored in the memory 403 (a value held by the memory 403) according to the addition value generated by the adder 401. The memory controller 406 may be configured, for example, to overwrite data stored in the memory 403 with the addition value generated by the adder 401. The memory controller 406 and the memory 403 may be connected by a data bus DATA and an address bus ADD so that the memory controller 406 can write data to the memory 403 or read data from the memory 403.

The number of bits of the first calculation value generated by the first calculation unit 410 is greater than the number of bits of the count value provided from each pixel 101 via the signal line 113 and readout circuit 112. In one example, the number of bits of the count value provided from the pixel 101 via the signal line 113 and readout circuit 112 is 4, and the number of bits of the first calculation value generated by the first calculation unit 410 is 8. The number of bits of the second calculation value generated by the second calculation unit 420 and the number of bits of the sum value generated by the adder 401 are greater than the number of bits of the count value provided from each pixel 101 via the signal line 113 and readout circuit 112. In one example, the number of bits of the second calculation value generated by the second calculation unit 420 is 8, and the number of bits of the sum value generated by the adder 401 is 8.

The first calculator 410 may include, for example, a data converter 402 and a first multiplier 404. The data converter 402 may be configured to expand the number of bits (bit width) of the count value provided from each pixel 101 via the signal line 113 and the readout circuit 112. The first multiplier 404 may include a first multiplier that multiplies the count value, the number of bits (bit width) of which has been expanded by the data converter 402, by a first coefficient (1-α) to generate a first calculated value. The second calculator 405 may include a second multiplier that multiplies data provided from the memory 403 (a value held by the memory 403) by a second coefficient (α) to generate a second calculated value. The memory controller 406 may be configured to read one frame's worth of data (image data) from the memory 403 for each frame period and output the data to the outside of the photoelectric conversion device 100 via the output unit 407. Note that the output unit 407 may constitute all or part of the output unit 114, or the output unit 407 may be provided downstream of the output unit 407.

The memory controller 406 may determine (correct) the address of the memory 403 to be updated according to the added value based on a correction signal MBC for correcting image blur (camera shake) caused by vibration of the imaging device in which the photoelectric conversion device 100 is installed.

The multiple pixels 101, memory 403, first computing unit 410, second computing unit 420, adder 401, and memory controller 406 are arranged on a single semiconductor chip (packaged semiconductor device). Alternatively, on a single semiconductor chip, the multiple pixels 101 may be arranged on one semiconductor layer, and at least one of the memory 403, first computing unit 410, second computing unit 420, adder 401, and memory controller 406 may be arranged on another semiconductor layer. However, the memory 403, first computing unit 410, second computing unit 420, adder 401, and memory controller 406 may be distributed and arranged across two or more semiconductor layers.

Figure 7 illustrates an example of the operation of the photoelectric conversion device 100 of the first embodiment. In one example, the cycle in which one frame's worth of image data is output from the photoelectric conversion device 100 to the outside is called one frame period. One frame period can be made up of M subframe periods. During one subframe period, the count values of all pixels 101 that make up the pixel array region 12 can be read out by the readout circuit 112 and provided to the image processing unit 120. The image processing unit 120 can generate one frame of image data by performing TIIR (Temporal Infinite Impulse Response) filtering on the image data of M subframes during one frame period, and output the image data to the outside.

In Figure 7, "frame" refers to a "frame period," and "subframe" refers to a "subframe period." Furthermore, "row selection" refers to a "row selection period" during which one row is selected, and "memory update" refers to a period during which the data in memory 403 is updated with the sum generated by adder 401. Furthermore, "output" refers to a period during which one frame of image data is output from photoelectric conversion device 100. In the example of Figure 7, multiple pixels 101 in pixel array region 12 are reset using a rolling shutter method, and count values are read out from multiple pixels 101 in row sequence. However, multiple pixels 101 in pixel array region 12 may also be driven using a global shutter method.

Figure 8 shows an example in which α is 0.5 (i.e., the first and second coefficients are 0.5), the count value provided by pixel 101 is 4 bits, and the data converter 402 converts the count value from 4 bits to 8 bits. In Figure 8, "Count Value (Decimal)" is the count value provided by pixel 101 at an arbitrary position in the pixel array area 12 expressed in decimal, and "Count Value (Binary)" is the count value provided by pixel 101 expressed in binary. In the example of Figure 8, the count value data provided by pixel 101 consists of 4 bits (i.e., the bit width is 4). In Figure 8, "Data After Conversion C" is the count value C after the 4-bit count value provided by pixel 101 at the arbitrary position is converted to 8 bits by the data converter 402. In the example of Figure 8, the data converter 402 expands the number of bits (bit width) of the count value provided by pixel 101 at the arbitrary position by shifting it 4 bits to the left. In FIG. 8, "retained value M" is the data (retained value) M read from the corresponding address in memory 403 (an arbitrary corresponding address in pixel array region 12).

In FIG. 8, "(1-α)×C" indicates the first calculated value generated by the first multiplier 404, and "α×M" indicates the second calculated value generated by the second multiplier 405. Also in FIG. 8, "(1-α)×C+α×M" is the sum generated by the adder 401 expressed in binary, and "(decimal)" is the sum generated by the adder 401 expressed in decimal.

During the first subframe (subframe = 1), the bit width of the count value "1101" provided from a pixel 101 at an arbitrary position is expanded to "11010000" by the data converter 402. Also during the first subframe, the first multiplier 404 multiplies "11010000" by the first coefficient (1-α) = 0.5 to generate "01101000" as the first calculated value. Also during the first subframe, the second multiplier 405 multiplies the held value "00000000" stored at the corresponding address in the memory 403 by the second coefficient α = 0.5 to generate "00000000" as the second calculated value. Furthermore, during the first subframe, the adder 401 adds the first calculated value and the second calculated value to generate the sum "01101000", which is then overwritten at the corresponding address in the memory 403 as the stored value M. In other words, the data "00000000" at the corresponding address in the memory 403 is updated with "01101000".

During the second subframe (subframe = 2), the bit width of the count value "1010" provided from the pixel 101 at the arbitrary position is expanded to "10100000" by the data converter 402. Also, during the first subframe, the first multiplier 404 multiplies "10100000" by the first coefficient (1-α) = 0.5 to generate "01010000" as the first calculated value. Also, during the second subframe, the second multiplier 405 multiplies the held value "01101000" stored at the corresponding address in the memory 403 by the second coefficient α = 0.5 to generate "00110100" as the second calculated value. Furthermore, during the second subframe, the adder 401 adds the first calculation value and the second calculation value to generate the sum "10000100", which is then overwritten at the corresponding address in the memory 403 as the stored value M. In other words, the data at the corresponding address in the memory 403, "01101000", is updated with "10000100".

Then, during the periods from the second subframe to the Mth subframe, the same processing is repeated based on the count value provided from the pixel 101 at the arbitrary position and the data (retained value) stored at the corresponding address in memory 403. This type of filtering is called TIIR filtering. By expanding the bit width in the first computing unit 410 as in this embodiment, the data overwritten at the corresponding address in memory 403 is smoothed with high resolution on the time axis, resulting in data with an improved SNR (signal-to-noise ratio), and a high-quality image can be obtained.

On the other hand, if the bit width is not expanded in the first computing unit 410, the lower-order bits of data will be lost in the calculations by the first computing unit 410, the second computing unit 420, and the adder 401, and therefore improvement in image quality due to TIIR filter processing cannot be expected.

The memory controller 406 may compress the sum generated by the adder 401 to generate compressed data, and update the value stored in the memory 403 based on the compressed data. In this case, the second calculator 429 multiplies the data obtained by decompressing the compressed data provided by the memory 403 by a second coefficient to generate a second calculation value.

Next, a photoelectric conversion device 100 according to a second embodiment will be described. Matters not mentioned in the second embodiment may follow the first embodiment. Figure 9 is a diagram showing the configuration of the image processing unit 120 in the photoelectric conversion device 100 according to the second embodiment. In the second embodiment, the image processing unit 120 includes a coefficient determination unit 408. The coefficient determination unit 408 may be configured to determine the first and second coefficients based on data stored in the memory 403. In the example shown in Figure 9, the first coefficient is 1-α, the second coefficient is α, and the sum of the first and second coefficients is 1. However, the first and second coefficients may be independent coefficients that are not correlated with each other. The first coefficient may be a value greater than 0 and less than 1. The second coefficient may be a value greater than 0 and less than 1.

In an example where the first coefficient is 1-α and the second coefficient is α, the larger the value of α, the stronger the smoothing effect in the time direction, improving the SNR but also increasing the likelihood of subject blur. For example, when processing a count value generated for a pixel at an arbitrary position in the pixel array region 12, α can be determined based on the value of the data at the corresponding address in memory 403, or the average value of the data at the address corresponding to a group of pixels within the region that includes the pixel at the arbitrary position. For example, by reducing α under high light levels (high count values) and increasing α under low light levels (low count values), it is possible to improve the SNR and suppress subject blur at the same time.

Next, a photoelectric conversion device 100 according to a third embodiment will be described. Matters not mentioned in the third embodiment may follow those of the first and second embodiments. FIG. 10 is a diagram showing the configuration of the image processing unit 120 in the photoelectric conversion device 100 according to the third embodiment. In the third embodiment, the photoelectric conversion device 100 includes a receiving unit 430 that receives a trigger signal TRIG from outside the photoelectric conversion device 100, and the output unit 407 of the image processing unit 120 outputs one frame of data stored in the memory 403 in response to activation of the trigger signal TRIG. In one example, the memory controller 406 may operate to read one frame of data from the memory 403 in response to activation of the trigger signal TRIG and output the data to the outside via the output unit 407. The memory 403 and the output unit 407 may be connected by a data bus. In this case, the data output from the memory 403 may be provided to the output unit 407 without passing through the memory controller 406, and may be output from the output unit 407 to the outside.

Figure 11 illustrates an example of the operation of the photoelectric conversion device 100 of the second embodiment. In response to activation of the trigger signal TRIG (transition to high level in the example of Figure 11), the memory controller 406 can operate to read one frame of data from the memory 403 and output it to the outside via the output unit 407. In one example, the memory controller 406 can start an operation to read one frame of data from the memory 403 and output it to the outside via the output unit 407 during the subframe period following the subframe in which the trigger signal TRIG is activated. The memory controller 406 can operate such that the data to be read is not updated during the period in which one frame of data is read from the memory 403 and output to the outside. Alternatively, depending on the application, the memory controller 406 may operate such that the data to be read is updated during the period in which one frame of data is read from the memory 403 and output to the outside.

Next, a photoelectric conversion device 100 according to the fourth embodiment will be described. Matters not mentioned in the fourth embodiment may follow those of the first to third embodiments. Figure 12 is a diagram showing the configuration of the image processing unit 120 in the photoelectric conversion device 100 according to the fourth embodiment. In the fourth embodiment, the image processing unit 120 includes a coefficient determination unit 408, but the coefficient determination unit 408 of the fourth embodiment differs from the coefficient determination unit 408 of the second embodiment.

The coefficient determination unit 408 may be configured to determine the first and second coefficients based on a comparison between the count value obtained by expanding the number of bits of the count value of a pixel at an arbitrary position in the pixel array region 12 by the data converter 402 and the data stored at the corresponding address in the memory 403. In the example shown in FIG. 12, the first coefficient is 1-α, the second coefficient is α, and the sum of the first and second coefficients is 1. However, the first and second coefficients may be independent coefficients that are not correlated with each other. The first coefficient may be a value greater than 0 and less than 1. The second coefficient may be a value greater than 0 and less than 1.

For example, if the difference between the count value provided by the data converter 402 and the data value provided by the memory 403 is within a predetermined value, the coefficient determination unit 408 increases the value of α above the reference value to strengthen the smoothing effect. On the other hand, if this difference is greater than the predetermined value (if the change in light intensity is considered to be large), the coefficient determination unit 408 can decrease the value of α below the reference value to prioritize tracking of changes in light intensity. Through this operation, α (i.e., the first and second coefficients) is set according to the magnitude of the change in light intensity within the scene, making it possible to achieve both improved SNR and suppression of subject blur.

The image processing unit 120 may include a control unit 412. The control unit 412 may, for example, detect an abnormality in the data (image) held by the memory 403, and accordingly reset all or part of the multiple pixels 101 in the pixel array region (e.g., the counter circuit 211), the readout circuit 112, and the memory 403. The control unit 412 may control the reset operation so that the multiple pixels 101 in the pixel array region 12 are reset more frequently than the memory 403. If the control unit 412 detects an abnormality in the data (image) held by the memory 403, it may perform other processing, such as noise removal processing.

Next, we will explain the photoelectric conversion device 100 of the fifth embodiment. Matters not mentioned in the fifth embodiment may follow those of the first to fourth embodiments. Figure 13 is a diagram showing the configuration of the image processing unit 120 in the photoelectric conversion device 100 of the fifth embodiment. The fifth embodiment provides a modified example of the coefficient determination unit 408 of the fourth embodiment.

As in the fourth embodiment, the coefficient determination unit 408 may be configured to determine the first and second coefficients based on a comparison between the count value provided by the data converter 402 and the data provided by the memory 403. The coefficient determination unit 408 may also generate information corresponding to the difference (i.e., the change in light intensity) between the count value obtained by expanding the number of bits of the count value of a pixel at an arbitrary position in the pixel array region 12 by the data converter 402 and the data stored at the corresponding address in the memory 403. This information may be output to the outside via the output unit 407. The coefficient determination unit 408 may generate binary information indicating whether the difference is greater than a reference value.

Next, a photoelectric conversion device 100 according to a sixth embodiment will be described. Matters not mentioned in the sixth embodiment may follow those of the first to fifth embodiments. FIG. 14 is a diagram illustrating the configuration of the image processing unit 120 in the photoelectric conversion device 100 according to the sixth embodiment. In the sixth embodiment, the image processing unit 120 includes a third computing unit (third multiplier) 410. The first computing unit 410 may be configured to multiply a count value generated in each pixel 101 by a first coefficient (γ here) to generate a first computation value. The third computing unit 410 may be configured to multiply data stored in the memory 403 during a first period by a third coefficient (β here) to generate a third computation value. The second computing unit 420 may be configured to multiply data stored in the memory 403 during a second period that precedes the first period by a second coefficient (α here) to generate a second computation value. The adder 401 may be configured to add the first computation value, the second computation value, and the third computation value to generate a sum.

Here, during the first period, data is written to the first area 403a of the memory 403, and during the second period, data is written to the second area 403b of the memory 403. Between the first and second periods, the data in the first area 403a may be transferred to the second area 403b. From another perspective, the latest version of the sum generated by the adder 401 may be written to the first area 403a, and before that, the data in the first area 403a may be transferred to the second area 403b. The memory constituting the first area 403a and the memory constituting the second area 403b may be separate. In another control method, the first area 403a and the second area 403b may be swapped for each subframe, in which case there is no need to transfer data from the first area 403a to the second area 403b.

According to the sixth embodiment, data processed by the TIIR filter can be obtained using data from the current subframe and data from two subframes prior to the current subframe. This makes it possible to obtain data with an improved SNR.

Modifications or specific examples of the first to sixth embodiments will be described below. FIG. 15 is a diagram showing a modification of the first calculator 410. a[3:0] is data (4 bits in this example) indicating the count value provided from a pixel 101 at an arbitrary position via the readout circuit 112, and b[3:0] is data (4 bits in this example) indicating the first coefficient (here, (1-α) in the above example). The first calculator 410 generates the result (shown as a×b) of multiplying a[3:0] and b[3:0] as the first calculation value. In this example, the number of bits of the first calculation value generated by the first calculator 410 is 8 bits, which is greater than the number of bits of the count value provided from each pixel 101 via the signal line 113 and the readout circuit 112, which is 4 bits.

Figure 16 shows a specific example of the data converter 402 in the first computing unit 410. The data converter 402 may include, for example, a bit width expansion unit 421, as well as at least one of a nonlinear correction unit 422 and a smoothing processing unit 423.

Figure 17 schematically illustrates the bit-width expansion process performed by the bit-width expansion unit 421. The bit-width expansion unit 421 adds one or more bits (four bits in this example) to the lower-order side of the count value (four bits in this example) provided by the pixel 101. Bit expansion as illustrated in Figure 17 may be achieved by providing an n-bit count value to the upper-order side of an m-bit input terminal of a downstream circuit and providing (m-n) bits of "0" to the lower-order side. Note that m and n have a relationship of m > n. Figure 18 schematically illustrates the nonlinear correction process performed by the nonlinear correction unit 422. As illustrated in Figure 18, the pixel 101 may have a nonlinear characteristic in which the number of input photons and the output level (count value) are related nonlinearly. The nonlinear correction unit 422 may correct the count value provided by the pixel 101 so as to obtain an output level (count value) proportional to the number of input photons. Figure 19 schematically illustrates the spatial smoothing process performed by the smoothing processing unit 423. Examples of smoothing processes include convolution operations including moving average filters or Gaussian filters, nonlinear operations including median filters, and noise removal processes using Fourier transforms or wavelet transforms, but other methods may also be used.

Figure 20 shows the configuration of a photoelectric conversion system 1000 according to the seventh embodiment. In the seventh embodiment, a signal processing device 120', which corresponds to the image processing unit 120 described above, is arranged outside the photoelectric conversion device 100. Figure 7 is used as a diagram illustrating the operation of the photoelectric conversion system 1000 shown in Figure 20, and "output" indicates the output of the signal processing device 120'. Furthermore, signals from pixels in the row selected in "row selection" are read out by the readout circuit 112 and output from the photoelectric conversion device 100 to the signal processing device 120' via the output unit 114.

The photoelectric conversion device 100 may include a plurality of pixels 101 that count photons and output count values, a readout circuit 112 that reads out the count values generated in the plurality of pixels 101, and an output unit 114 that outputs the count values read out by the readout circuit 112. The photoelectric conversion device 100 may also include a control pulse generation unit 115, a horizontal scanning circuit 111, a signal line 113, and a vertical scanning circuit 110.

The signal processing device 120' may include a memory 403, a first computing unit 410, a second computing unit 420, an adder 401, and a memory controller 406. The configurations and functions of the memory 403, the first computing unit 410, the second computing unit 420, the adder 401, and the memory controller 406 may be similar to those described above.

In addition, in the above-described embodiments, the count value generated by the pixel 101 has been described as a signal having a resolution corresponding to the incidence of one photon, but this is not limited to this configuration. For example, the pixel 101 may output a count value whose signal value increases by one when multiple photons are incident. One such configuration is a configuration in which a detection circuit that detects the pulse signal output by the waveform shaping unit 210 is provided between the waveform shaping unit 210 and the counter circuit 211 in the pixel 101 shown in FIG. 4. In this configuration, when multiple pulse signals are input to the detection circuit, the detection circuit outputs a signal to the counter circuit 211. The counter circuit 211 counts this signal. As a result, 1 LSB (Lowest Significant Bit) of the count value generated by the counter circuit 211 corresponds to the incidence of multiple photons. In this case, the signal generated by the data converter 402 has a resolution smaller than the multiple photons corresponding to 1 LSB of the count value generated by the counter circuit 211.

The following describes application examples of the photoelectric conversion device 100 according to the first to seventh embodiments. When the seventh embodiment is applied, the signal processing device 120' may constitute part of a signal processing device that processes signals output from an imaging device (photoelectric conversion device), such as the signal processing unit 1007, image processing unit 1312, image processing circuit 1404, signal processing unit 352, etc.

Figure 21 is a block diagram showing the general configuration of a photoelectric conversion system in the first application example.

The above-described photoelectric conversion device 100 can be applied to a variety of photoelectric conversion systems. Examples of applicable photoelectric conversion systems include digital still cameras, digital camcorders, surveillance cameras, copiers, fax machines, mobile phones, vehicle-mounted cameras, and observation satellites. Camera modules equipped with an optical system such as a lens and an imaging device are also included in photoelectric conversion systems. Figure 21 shows a block diagram of a digital still camera as an example of such a system.

The photoelectric conversion system 1000 illustrated in FIG. 21 includes an imaging device 1004, which is an example of a photoelectric conversion device. The photoelectric conversion system 1000 also includes a lens 1002 that forms an optical image of a subject on the imaging device 1004, an aperture 1003 that adjusts the amount of light passing through the lens 1002, and a barrier 1001 that protects the lens 1002. The lens 1002 and aperture 1003 form an optical system (optical device) that focuses light on the imaging device 1004. The imaging device 1004 is the photoelectric conversion device 100 (imaging device) of any of the above embodiments, and converts the optical image formed by the lens 1002 into an electrical signal.

The photoelectric conversion system 1000 also has a signal processing unit 1007, which is an image generation unit that generates an image by processing the output signal output by the imaging device 1004. The signal processing unit 1007 functions as a processing device that performs various corrections and compressions as necessary and outputs image data. The signal processing unit 1007 may be formed on the same semiconductor substrate on which the imaging device 1004 is provided, or may be formed on a semiconductor substrate separate from the imaging device 1004. The imaging device 1004 and signal processing unit 1007 may also be formed on the same semiconductor substrate.

The photoelectric conversion system 1000 further includes a memory unit 1010 for temporarily storing image data, and an external interface unit (external I/F unit) 1013 for communicating with an external computer or the like. The photoelectric conversion system 1000 also includes a recording medium 1012, such as a semiconductor memory, for recording or reading image data, and a recording medium control interface unit (recording medium control I/F unit) 1011 for recording or reading data from the recording medium 1012. The recording medium control I/F unit 1011 and the recording medium 1012 may form part of a storage device. The recording medium 1012 may be built into the photoelectric conversion system 1000, or may be removable.

The photoelectric conversion system 1000 further includes an overall control and calculation unit 1009 that performs various calculations and controls the entire digital still camera, and a timing generation unit 1008 that outputs various timing signals to the image capture device 1004 and signal processing unit 1007. The overall control and calculation unit 1009 and timing generation unit 1008 may form part of a control device for controlling the operation of the photoelectric conversion system 1000. Here, timing signals and the like may be input from the outside, and the photoelectric conversion system 1000 only needs to include at least the image capture device 1004 and the signal processing unit 1007 that processes the output signal from the image capture device 1004.

The imaging device 1004 outputs an imaging signal to the signal processing unit 1007. The signal processing unit 1007 performs predetermined signal processing on the imaging signal output from the imaging device 1004 and outputs image data. The signal processing unit 1007 generates an image using the imaging signal. Although not shown in FIG. 21 , a display device such as a display for displaying the generated image may be provided in the photoelectric conversion system 1000. In this way, according to this embodiment, it is possible to realize a photoelectric conversion system 1000 that applies the photoelectric conversion device 100 (imaging device) of any of the above embodiments.

Figures 22(a) and 22(b) are diagrams showing the configuration of a photoelectric conversion system 1300 and a mobile object 1301 in a second application example.

Figure 21(a) shows an example of a photoelectric conversion system for an in-vehicle camera. The photoelectric conversion system 1300 includes an image capture device 1310. The image capture device 1310 is the photoelectric conversion device 100 (image capture device) described in any of the above embodiments. The photoelectric conversion system 1300 includes an image processing unit 1312 that performs image processing on multiple pieces of image data acquired by the image capture device 1310. The photoelectric conversion system 1300 also includes a distance acquisition unit 1316 that calculates the distance to an object, and a collision determination unit 1318 that determines whether or not there is a possibility of a collision based on the calculated distance. Here, the distance acquisition unit 1316 may acquire distance information to the object using a time-of-flight (ToF) method, or may acquire distance information using parallax information, etc. In other words, the distance information is information related to parallax, defocus amount, distance to the object, etc. The collision determination unit 1318 may determine the possibility of a collision using any of this distance information. The distance acquisition unit 1316 may be realized by dedicated hardware or by a software module. The distance acquisition unit 1316 may also be realized by an FPGA (Field Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or the like. The distance acquisition unit 1316 may also be realized by a combination of these.

The photoelectric conversion system 1300 is connected to a vehicle information acquisition device 1320 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. The photoelectric conversion system 1300 is also connected to an ECU 1330, which is a control device that outputs a control signal to generate braking force for the vehicle based on the determination result of the collision determination unit 1318. The photoelectric conversion system 1300 is also connected to an alarm device 1340 that issues an alert to the driver based on the determination result of the collision determination unit 1318. For example, if the determination result of the collision determination unit 1318 indicates a high possibility of collision, the ECU 1330 controls the drive device (mechanical device) 1360 by applying the brakes, releasing the accelerator, suppressing engine output, etc., to avoid the collision and mitigate damage. The alarm device 1340 warns the user by sounding an alarm, displaying alarm information on a screen such as a car navigation system, or vibrating the seat belt or steering wheel.

In this embodiment, the photoelectric conversion system 1300 captures images of the surroundings of the vehicle (mobile body 1301), for example, the front or rear. Figure 21(b) shows a photoelectric conversion system configured to capture images of the area in front of the vehicle (imaging range 1350). The vehicle information acquisition device 1320 sends instructions to the photoelectric conversion system 1300 or the imaging device 1310. This configuration can further improve the accuracy of distance measurement.

The above describes an example of control to prevent collisions with other vehicles, but the photoelectric conversion system 1300 can also be applied to automatic driving control to follow other vehicles and automatic driving control to prevent vehicles from drifting out of their lanes. Furthermore, the photoelectric conversion system 1300 can be applied not only to vehicles such as automobiles, but also to moving bodies (mobile devices) such as ships, aircraft, or industrial robots. These moving bodies include one or both of a driving force generation unit that generates driving force primarily used to move the moving body, and a rotating body primarily used to move the moving body. The driving force generation unit can be an engine, a motor, or the like. The rotating body can be a tire, a wheel, a ship's screw, an aircraft's propeller, or the like. In addition to moving bodies, the system can be applied to a wide range of equipment that uses object recognition, such as intelligent transport systems (ITS).

Figure 23 is a block diagram showing an example configuration of a range image sensor 1401, which is a photoelectric conversion system in the third application example.

As shown in Figure 23, the distance image sensor 1401 is composed of an optical system 1407, a photoelectric conversion device 1408, an image processing circuit 1404, a monitor 1405, and a memory 1406. The distance image sensor 1401 is able to obtain a distance image corresponding to the distance to the subject by receiving light (modulated light or pulsed light) that is projected toward the subject from a light source device 1409 and reflected from the surface of the subject.

The optical system 1407 is composed of one or more lenses, and guides image light (incident light) from the subject to the photoelectric conversion device 1408, forming an image on the light-receiving surface (sensor section) of the photoelectric conversion device 1408.

The photoelectric conversion device 1408 is the photoelectric conversion device 100 of each of the above-described embodiments, and a distance signal indicating the distance determined from the light reception signal output from the photoelectric conversion device 1408 is supplied to the image processing circuit 1404.

The image processing circuit 1404 performs image processing to construct a distance image based on the distance signal supplied from the photoelectric conversion device 1408. The distance image (image data) obtained by this image processing is then supplied to the monitor 1405 for display, or supplied to the memory 1406 for storage (recording).

By applying the photoelectric conversion device 100 described above to the range image sensor 1401 configured in this manner, it is possible to obtain, for example, more accurate range images as pixel characteristics improve.

Figure 24 is a diagram showing an example of the general configuration of an endoscopic surgery system 1250, which is a photoelectric conversion system according to the fourth application example.

Figure 24 shows an operator (doctor) 1231 performing surgery on a patient 1232 on a patient bed 1233 using an endoscopic surgery system 1250. As shown, the endoscopic surgery system 1250 includes an endoscope 1200, surgical tools 1210, and a cart 1234 on which various devices for endoscopic surgery are mounted.

The endoscope 1200 includes a lens barrel 1201, the tip of which is inserted into the body cavity of the patient 1232 by a predetermined length, and a camera head 1202 connected to the base end of the lens barrel 1201. In the illustrated example, the endoscope 1200 is configured as a so-called rigid lens barrel having a rigid lens barrel 1201, but the endoscope 1200 may also be configured as a so-called flexible lens barrel having a flexible lens barrel.

An opening into which an objective lens is fitted is provided at the tip of the lens barrel 1201. A light source device 1203 is connected to the endoscope 1200, and light generated by the light source device 1203 is guided to the tip of the lens barrel 1201 by a light guide extending inside the lens barrel 1201, and is then irradiated via the objective lens towards an object to be observed inside the body cavity of the patient 1232. The endoscope 1200 may be a direct-viewing endoscope, an oblique-viewing endoscope, or a side-viewing endoscope.

An optical system and a photoelectric conversion device are provided inside the camera head 1202, and light reflected from the object of observation (observation light) is focused onto the photoelectric conversion device by the optical system. The photoelectric conversion device photoelectrically converts the observation light to generate an electrical signal corresponding to the observation light, i.e., an image signal corresponding to the observed image. The photoelectric conversion device can be the photoelectric conversion device 100 (imaging device) described in each of the above-mentioned embodiments. The image signal is sent to the camera control unit (CCU) 1235 as RAW data.

The CCU 1235 is composed of a CPU (Central Processing Unit), GPU (Graphics Processing Unit), etc., and provides overall control over the operation of the endoscope 1200 and the display device 1236. Furthermore, the CCU 1235 receives image signals from the camera head 1202 and performs various image processing on the image signals, such as development processing (demosaic processing), to display an image based on the image signals.

The display device 1236, under the control of the CCU 1235, displays an image based on the image signal that has been image processed by the CCU 1235.

The light source device 1203 is composed of a light source such as an LED (Light Emitting Diode), and supplies illumination light to the endoscope 1200 when photographing the surgical site, etc.

The input device 1237 is an input interface for the endoscopic surgery system 1250. The user can input various information and instructions to the endoscopic surgery system 1250 via the input device 1237.

The treatment tool control device 1238 controls the operation of the energy treatment tool 1212 for cauterizing tissue, incising, sealing blood vessels, etc.

The light source device 1203, which supplies illumination light to the endoscope 1200 when photographing the surgical site, can be configured from a white light source composed of, for example, an LED, a laser light source, or a combination of these. When the white light source is configured from a combination of RGB laser light sources, the output intensity and output timing of each color (each wavelength) can be controlled with high precision, making it possible to adjust the white balance of the captured image in the light source device 1203. In this case, it is also possible to capture images corresponding to each RGB color in a time-division manner by irradiating the object of observation with laser light from each RGB laser light source in a time-division manner and controlling the drive of the image sensor in the camera head 1202 in synchronization with the irradiation timing. This method makes it possible to obtain color images without providing a color filter to the image sensor.

The light source device 1203 may also be controlled to change the intensity of the light it outputs at predetermined time intervals. The image sensor of the camera head 1202 is controlled to acquire images in a time-division manner in synchronization with the timing of the change in light intensity, and these images are then combined to generate a high dynamic range image free of so-called blocked-up shadows and blown-out highlights.

The light source device 1203 may also be configured to provide light in a predetermined wavelength band compatible with special light observation. Special light observation, for example, utilizes the wavelength dependence of light absorption in body tissue. Specifically, by irradiating light with a narrower band than the light irradiated during normal observation (i.e., white light), specific tissue, such as blood vessels on the surface of the mucosa, can be imaged with high contrast. Alternatively, special light observation may involve fluorescence observation, in which images are obtained using fluorescence generated by irradiating excitation light. Fluorescence observation can involve irradiating excitation light onto body tissue and observing the fluorescence from the tissue, or locally injecting a reagent such as indocyanine green (ICG) into the body tissue and irradiating the tissue with excitation light corresponding to the fluorescent wavelength of the reagent to obtain a fluorescent image. The light source device 1203 may be configured to provide narrow band light and/or excitation light compatible with such special light observation.

Figures 25(a) and 25(b) illustrate glasses 1600 (smart glasses) that are a photoelectric conversion system according to a fifth application example. The glasses 1600 have a photoelectric conversion device 1602. The photoelectric conversion device 1602 is the photoelectric conversion device 100 (imaging device) described in each of the above embodiments. A display device including a light-emitting device such as an OLED or LED may also be provided on the back side of the lens 1601. There may be one or more photoelectric conversion devices 1602. Furthermore, multiple types of photoelectric conversion devices may be used in combination. The arrangement position of the photoelectric conversion device 1602 is not limited to that shown in Figure 25(a).

The glasses 1600 further include a control device 1603. The control device 1603 functions as a power source that supplies power to the photoelectric conversion device 1602 and the display device. The control device 1603 also controls the operation of the photoelectric conversion device 1602 and the display device. The lens 1601 is formed with an optical system for focusing light onto the photoelectric conversion device 1602.

Figure 25(b) illustrates glasses 1610 (smart glasses) as a fifth application example. The glasses 1610 have a control device 1612, which is equipped with a photoelectric conversion device corresponding to the photoelectric conversion device 1602 and a display device. The lens 1611 is formed with an optical system for projecting light emitted from the photoelectric conversion device in the control device 1612 and the display device, and an image is projected onto the lens 1611. The control device 1612 functions as a power source that supplies power to the photoelectric conversion device and the display device, and controls the operation of the photoelectric conversion device and the display device. The control device may have a gaze detection unit that detects the wearer's gaze. Infrared light may be used for gaze detection. The infrared light emitter emits infrared light toward the eyeball of a user gazing at a displayed image. An imaging unit with a light receiving element detects the reflected light of the emitted infrared light from the eyeball, thereby obtaining an image of the eyeball. By providing a reduction means for reducing light from the infrared light emitter to the display unit in a planar view, degradation of image quality is reduced.

The user's line of sight with respect to the displayed image is detected from an image of the eyeball obtained by capturing infrared light. Any known method can be used to detect the line of sight using an image of the eyeball. As an example, a line of sight detection method based on the Purkinje image formed by the reflection of irradiated light on the cornea can be used.

More specifically, gaze detection processing is performed based on the pupil-corneal reflex method. Using the pupil-corneal reflex method, a gaze vector representing the direction (rotation angle) of the eyeball is calculated based on the pupil image and Purkinje image contained in the captured image of the eyeball, thereby detecting the user's gaze.

The display device of this embodiment may have a photoelectric conversion device with a light-receiving element, and may control the image displayed on the display device based on user line-of-sight information from the photoelectric conversion device.

Specifically, the display device determines a first field of view area where the user gazes and a second field of view area other than the first field of view area based on the line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. In the display area of the display device, the display resolution of the first field of view area may be controlled to be higher than the display resolution of the second field of view area. In other words, the resolution of the second field of view area may be lower than that of the first field of view area.

The display area may also include a first display area and a second display area different from the first display area, and a high priority area may be determined from the first display area and the second display area based on line-of-sight information. The first field of view area and the second field of view area may be determined by a control device of the display device, or may be received from an external control device. The resolution of the high priority area may be controlled to be higher than the resolution of areas other than the high priority area. In other words, the resolution of areas with relatively low priority may be lowered.

In addition, AI may be used to determine the first field of view area and high-priority areas. The AI may be a model configured to estimate the angle of gaze and the distance to an object in the line of sight from the image of the eyeball, using as training data an image of the eyeball and the actual direction in which the eyeball was looking in the image. The AI program may be stored in the display device, the photoelectric conversion device, or an external device. If stored in an external device, it is transmitted to the display device via communication.

When display control is based on visual recognition detection, it is preferably applied to smart glasses that also have a photoelectric conversion device that captures images of the outside world. The smart glasses can display captured external information in real time.

Figures 26(a) and 26(b) are diagrams showing an electronic device according to a sixth application example. The electronic device may be configured as, for example, a smartphone or a tablet.

Figure 26(a) shows the front side of electronic device 1500, and Figure 26(b) shows the back side of electronic device 1500.

As shown in FIG. 26(a), a display 1510 for displaying images is disposed in the center of the surface of the electronic device 1500. Also, along the upper edge of the surface of the electronic device 1500, front cameras 1521 and 1522 using the above-described photoelectric conversion device 100, an IR light source 1530 that emits infrared light, and a visible light source 1540 that emits visible light are disposed.

Furthermore, as shown in FIG. 26(b), rear cameras 1551 and 1552 using the above-mentioned photoelectric conversion device 100, an IR light source 1560 that emits infrared light, and a visible light source 1570 that emits visible light are arranged along the upper edge of the back surface of the electronic device 1500.

By applying the photoelectric conversion device 100 described above, the electronic device 1500 configured in this manner can capture higher-quality images, for example. The photoelectric conversion device can also be applied to other electronic devices, such as infrared sensors, distance measurement sensors using active infrared light sources, security cameras, and personal or biometric authentication cameras. This can improve the accuracy and performance of these electronic devices.

Figure 27 is a block diagram of an X-ray CT device according to a seventh application example. The photoelectric conversion device 100 described above can be used as a detector for an X-ray CT device. The X-ray CT device 30 in this embodiment includes an X-ray generator 310, a wedge 316, a collimator 318, an X-ray detector 320, a tabletop 330, a rotating frame 340, and a high-voltage generator 350. The X-ray CT device 30 also includes a data acquisition system (DAS) 351, a signal processor 352, a display 353, and a controller 354.

The X-ray generating unit 310 is composed of, for example, a vacuum tube that generates X-rays. The vacuum tube of the X-ray generating unit 310 is supplied with high voltage and filament current from the high-voltage generator 350. X-rays are generated by irradiating thermions from the cathode (filament) toward the anode (target).

The wedge 316 is a filter that adjusts the amount of X-rays irradiated from the X-ray generator 310. The wedge 316 attenuates the amount of X-rays so that the X-rays irradiated from the X-ray generator 310 to the subject have a predetermined distribution. The collimator 318 is composed of a lead plate or the like that narrows the irradiation range of the X-rays that have passed through the wedge 316. The X-rays generated by the X-ray generator 310 are shaped into a cone beam via the collimator 318 and irradiated onto the subject on the tabletop 330.

The X-ray detection unit 320 is configured using the photoelectric conversion device 100 described above. The X-ray detection unit 320 detects X-rays that have passed through the subject from the X-ray generation unit 310 and outputs a signal corresponding to the X-ray dose to the DAS 351.

The rotating frame 340 is annular and rotatable. Inside the rotating frame 340, the X-ray generation unit 310 (wedge 316, collimator 318) and the X-ray detection unit 320 are arranged facing each other. The X-ray generation unit 310 and the X-ray detection unit 320 can rotate together with the rotating frame 340.

The high-voltage generator 350 includes a boost circuit and outputs a high voltage to the X-ray generator 310. The DAS 351 includes an amplifier circuit and an A/D converter circuit, and outputs the signal from the X-ray detector 320 to the signal processor 352 as digital data.

The signal processing unit 352 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory), and is capable of performing image processing on digital data. The display unit 353 includes a flat display device and is capable of displaying X-ray images. The control unit 354 includes a CPU, ROM, RAM, and other components, and controls the overall operation of the X-ray CT device 30.

The embodiments described above can be modified as appropriate without departing from the technical concept. The disclosure of this specification includes not only what is described herein, but also all matters that can be understood from this specification and the drawings attached hereto. The disclosure of this specification also includes the complement of the concepts described herein. In other words, if this specification states, for example, that "A is greater than B," then even if the statement "A is not greater than B" is omitted, it can be said that this specification discloses that "A is not greater than B." This is because when it states that "A is greater than B," it is assumed that the case where "A is not greater than B" is taken into consideration.

The disclosure of the present specification includes the following configurations.
(Item 1)
A photoelectric conversion device having a plurality of pixels that count photons and output count values,
Memory and
a first calculator that multiplies a count value generated for each pixel by a first coefficient to generate a first calculated value;
a second calculator that multiplies the data provided from the memory by a second coefficient to generate a second calculation value;
an adder that adds the first calculation value and the second calculation value to generate a sum;
a memory controller that updates data stored in the memory in accordance with the added value;
the number of bits of the first calculation value generated by the first calculation unit is greater than the number of bits of the count value;
A photoelectric conversion device characterized by:
(Item 2)
the number of bits of the second operation value generated by the second operation unit and the number of bits of the sum value generated by the adder are greater than the number of bits of the count value;
2. The photoelectric conversion device according to item 1,
(Item 3)
the first computing unit includes: a data converter that expands the number of bits of the count value provided from each pixel; and a multiplier that multiplies the count value, the number of bits of which has been expanded by the data converter, by the first coefficient to generate the first computed value.
3. The photoelectric conversion device according to item 1 or 2.
(Item 4)
the data converter performs nonlinear correction processing after expanding the number of bits of the count value provided from each pixel;
4. The photoelectric conversion device according to item 3.
(Item 5)
the data converter performs nonlinear correction processing and smoothing processing after expanding the number of bits of the count value provided from each pixel;
4. The photoelectric conversion device according to item 3.
(Item 6)
the memory controller compresses the sum generated by the adder to generate compressed data, and updates the value stored in the memory based on the compressed data;
6. The photoelectric conversion device according to any one of items 1 to 5.
(Item 7)
the second computing unit multiplies data obtained by decompressing the compressed data provided from the memory by the second coefficient to generate the second computation value;
7. The photoelectric conversion device according to item 6,
(Item 8)
the first coefficient is a value greater than 0 and less than 1,
the second coefficient is a value greater than 0 and less than 1;
8. The photoelectric conversion device according to any one of items 1 to 7.
(Item 9)
the sum of the first coefficient and the second coefficient is 1;
9. The photoelectric conversion device according to any one of items 1 to 8.
(Item 10)
further comprising a coefficient determination unit that determines the first coefficient and the second coefficient based on data stored in the memory;
10. The photoelectric conversion device according to any one of items 1 to 9.
(Item 11)
a coefficient determination unit that determines the first coefficient and the second coefficient based on the count value provided from each pixel and data stored in the memory,
10. The photoelectric conversion device according to any one of items 1 to 9.
(Item 12)
a coefficient determination unit that determines the first coefficient and the second coefficient based on a difference between the count value provided from each pixel and the data stored in the memory,
10. The photoelectric conversion device according to any one of items 1 to 9.
(Item 13)
a receiving unit for receiving a trigger signal;
an output unit that outputs one frame of data stored in the memory in response to activation of the trigger signal by the receiving unit;
13. The photoelectric conversion device according to any one of items 1 to 12, further comprising:
(Item 14)
13. The photoelectric conversion device according to any one of items 1 to 12, further comprising an output unit that outputs information corresponding to the difference between the count value provided from each pixel and the data stored in the memory.
(Item 15)
further comprising a third computing unit;
the third computing unit multiplies the data stored in the memory during the first period by a third coefficient to generate a third computation value;
the second computing unit multiplies data stored in the memory for a second period earlier than the first period by a second coefficient to generate the second computed value;
the adder adds the first calculation value, the second calculation value, and the third calculation value to generate the sum;
15. The photoelectric conversion device according to any one of items 1 to 14.
(Item 16)
The frequency of resetting the plurality of pixels is higher than the frequency of resetting the memory.
16. The photoelectric conversion device according to any one of items 1 to 15.
(Item 17)
the memory controller determines an address of the memory to be updated according to the added value based on a correction signal for correcting image blur caused by vibration of the imaging device;
17. The photoelectric conversion device according to any one of items 1 to 16.
(Item 18)
Each pixel includes an avalanche photodiode.
8. The photoelectric conversion device according to any one of items 1 to 7.
(Item 19)
Each pixel further includes a waveform shaping unit connected to the avalanche photodiode and a counter circuit that generates a first count value by counting the pulse signal output by the waveform shaping unit;
the first computing unit includes: a data converter that expands the number of bits of the first count value provided from each pixel; and a multiplier that multiplies the count value, the number of bits of which has been expanded by the data converter, by the first coefficient to generate the first computed value.
19. The photoelectric conversion device according to item 18.
(Item 20)
the plurality of pixels, the memory, the first computing unit, the second computing unit, the adder, and the memory controller are arranged on one semiconductor chip.
20. The photoelectric conversion device according to any one of items 1 to 19,
(Item 21)
In the one semiconductor chip, the plurality of pixels are arranged in one semiconductor layer, and at least one of the memory, the first computing unit, the second computing unit, the adder, and the memory controller is arranged in another semiconductor layer.
21. The photoelectric conversion device according to item 20,
(Item 22)
Item 22. The photoelectric conversion device according to any one of items 1 to 21,
a signal processing unit that processes a signal output from the photoelectric conversion device;
A photoelectric conversion system comprising:
(Item 23)
A moving object including the photoelectric conversion device according to any one of items 1 to 21,
A moving body comprising a control unit that controls the movement of the moving body using a signal output from the photoelectric conversion device.
(Item 24)
A photoelectric conversion system including a photoelectric conversion device and a signal processing device that processes a signal output from the photoelectric conversion device,
the photoelectric conversion device includes a plurality of pixels that count photons and output count values, a readout circuit that reads out the count values generated in the plurality of pixels, and an output unit that outputs the count values read out by the readout circuit;
The signal processing device includes:
Memory and
a first calculator that multiplies a count value generated for each pixel by a first coefficient to generate a first calculated value;
a second calculator that multiplies the data provided from the memory by a second coefficient to generate a second calculation value;
an adder that adds the first calculation value and the second calculation value to generate a sum;
a memory controller that updates data stored in the memory in accordance with the added value;
the number of bits of the first calculation value generated by the first calculation unit is greater than the number of bits of the count value;
A photoelectric conversion system comprising:
(Item 25)
A mobile object including the photoelectric conversion system according to item 24,
A moving body comprising a control unit that controls the movement of the moving body using a signal output by the photoelectric conversion system.

The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Therefore, the following claims are appended to clarify the scope of the invention.

100: Photoelectric conversion device, 401: Adder, 402: Data converter, 403: Memory, 404: First multiplier, 405: Second multiplier, 406: Memory controller, 407: Output unit, 410: First computing unit, 420: Second computing unit,

Claims (25)

A photoelectric conversion device having a plurality of pixels that count photons and output count values,
Memory and
a first calculator that multiplies a count value generated for each pixel by a first coefficient to generate a first calculated value;
a second calculator that multiplies the data provided from the memory by a second coefficient to generate a second calculation value;
an adder that adds the first calculation value and the second calculation value to generate a sum;
a memory controller that updates data stored in the memory in accordance with the added value;
the number of bits of the first calculation value generated by the first calculation unit is greater than the number of bits of the count value;
A photoelectric conversion device characterized by: the number of bits of the second operation value generated by the second operation unit and the number of bits of the sum value generated by the adder are greater than the number of bits of the count value;
2. The photoelectric conversion device according to claim 1. the first computing unit includes: a data converter that expands the number of bits of the count value provided from each pixel; and a multiplier that multiplies the count value, the number of bits of which has been expanded by the data converter, by the first coefficient to generate the first computed value.
2. The photoelectric conversion device according to claim 1. the data converter performs nonlinear correction processing after expanding the number of bits of the count value provided from each pixel;
4. The photoelectric conversion device according to claim 3. the data converter performs nonlinear correction processing and smoothing processing after expanding the number of bits of the count value provided from each pixel;
4. The photoelectric conversion device according to claim 3. the memory controller compresses the sum generated by the adder to generate compressed data, and updates the value stored in the memory based on the compressed data;
2. The photoelectric conversion device according to claim 1. the second computing unit multiplies data obtained by decompressing the compressed data provided from the memory by the second coefficient to generate the second computation value;
7. The photoelectric conversion device according to claim 6. the first coefficient is a value greater than 0 and less than 1,
the second coefficient is a value greater than 0 and less than 1;
2. The photoelectric conversion device according to claim 1. the sum of the first coefficient and the second coefficient is 1;
2. The photoelectric conversion device according to claim 1. further comprising a coefficient determination unit that determines the first coefficient and the second coefficient based on data stored in the memory;
2. The photoelectric conversion device according to claim 1. a coefficient determination unit that determines the first coefficient and the second coefficient based on the count value provided from each pixel and data stored in the memory,
2. The photoelectric conversion device according to claim 1. a coefficient determination unit that determines the first coefficient and the second coefficient based on a difference between the count value provided from each pixel and the data stored in the memory,
2. The photoelectric conversion device according to claim 1. a receiving unit for receiving a trigger signal;
an output unit that outputs one frame of data stored in the memory in response to activation of the trigger signal by the receiving unit;
The photoelectric conversion device according to claim 1 , further comprising: The photoelectric conversion device of claim 1, further comprising an output unit that outputs information corresponding to the difference between the count value provided by each pixel and the data stored in the memory. further comprising a third computing unit;
the third computing unit multiplies the data stored in the memory during the first period by a third coefficient to generate a third computation value;
the second computing unit multiplies data stored in the memory for a second period earlier than the first period by a second coefficient to generate the second computed value;
the adder adds the first calculation value, the second calculation value, and the third calculation value to generate the sum;
2. The photoelectric conversion device according to claim 1. The frequency of resetting the plurality of pixels is higher than the frequency of resetting the memory.
2. The photoelectric conversion device according to claim 1. the memory controller determines an address of the memory to be updated according to the added value based on a correction signal for correcting image blur caused by vibration of the imaging device;
2. The photoelectric conversion device according to claim 1. Each pixel includes an avalanche photodiode.
2. The photoelectric conversion device according to claim 1. Each pixel further includes a waveform shaping unit connected to the avalanche photodiode and a counter circuit that generates a first count value by counting pulse signals output by the waveform shaping unit;
the first calculator includes: a data converter that expands the number of bits of the first count value provided from each pixel; and a multiplier that multiplies the count value, the number of bits of which has been expanded by the data converter, by the first coefficient to generate the first calculation value.
19. The photoelectric conversion device according to claim 18. the plurality of pixels, the memory, the first computing unit, the second computing unit, the adder, and the memory controller are arranged on one semiconductor chip.
2. The photoelectric conversion device according to claim 1. In the one semiconductor chip, the plurality of pixels are arranged on one semiconductor layer, and at least one of the memory, the first computing unit, the second computing unit, the adder, and the memory controller is arranged on another semiconductor layer.
21. The photoelectric conversion device according to claim 20. The photoelectric conversion device according to any one of claims 1 to 21,
a signal processing unit that processes a signal output from the photoelectric conversion device;
A photoelectric conversion system comprising: A moving object comprising the photoelectric conversion device according to any one of claims 1 to 21,
A moving body comprising a control unit that controls the movement of the moving body using a signal output from the photoelectric conversion device. A photoelectric conversion system including a photoelectric conversion device and a signal processing device that processes a signal output from the photoelectric conversion device,
the photoelectric conversion device includes a plurality of pixels that count photons and output count values, a readout circuit that reads out the count values generated in the plurality of pixels, and an output unit that outputs the count values read out by the readout circuit;
The signal processing device includes:
Memory and
a first calculator that multiplies a count value generated for each pixel by a first coefficient to generate a first calculated value;
a second calculator that multiplies the data provided from the memory by a second coefficient to generate a second calculation value;
an adder that adds the first calculation value and the second calculation value to generate a sum;
a memory controller that updates data stored in the memory in accordance with the added value;
the number of bits of the first calculation value generated by the first calculation unit is greater than the number of bits of the count value;
A photoelectric conversion system comprising: A moving object comprising the photoelectric conversion system according to claim 24,
A moving body comprising a control unit that controls the movement of the moving body using a signal output by the photoelectric conversion system.