Photoelectric conversion device

Abstract

To provide a photoelectric conversion device that can shorten measurement time.SOLUTION: A photoelectric conversion device has: a timing generation unit that periodically generates first timing indicating the timing for a light-emitting device to emit light in a first mode, and periodically generates second timing indicating the timing for the light-emitting device to emit light in a second mode; a light receiving unit that generates a light reception signal on the basis of incident light incident in an exposure period; and an exposure period control unit. The length of the cycle of the second timing is longer than the length of the cycle of the first timing. In the first mode, one cycle of the first timing is divided into a plurality of periods of time. The exposure period control unit generates a control signal indicating the timing of the exposure period that has the time width of one of the periods of time of one cycle of the first timing. The exposure period control unit determines the timing of the exposure period in the second mode on the basis of a frequency distribution in which a count value of the light reception signal is associated with each of the plurality of exposure periods in the first mode.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a photoelectric conversion device. [Background technology]

[0002] Patent Document 1 discloses a distance measurement technique that irradiates an object with light from a light source and measures the distance to the object based on the relationship between the timing of light emission from the light source and the timing of light reception reflected from the object. In the distance measurement technique of Patent Document 1, measurement is repeatedly performed while changing the exposure period during which photons are received by the light receiving element. In Patent Document 1, distance measurement is performed using a two-stage process in which the length of the exposure period and the light emission cycle are different from each other. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2017 / 141957 Summary of the Invention [Problem to be solved by the invention]

[0004] In a photoelectric conversion device used in a distance measuring technique such as that described in Patent Document 1, there is a demand for further shortening the measurement time.

[0005] An object of the present invention is to provide a photoelectric conversion device capable of shortening the measurement time. [Means for solving the problem]

[0006] According to one disclosure of the present specification, a photoelectric conversion device includes a timing generation unit that periodically generates a first timing indicating an emission timing of a light emitting device in a first mode and periodically generates a second timing indicating an emission timing of the light emitting device in a second mode, a light receiving unit that generates a light receiving signal based on incident light that is incident during an exposure period, and an exposure period control unit that generates a control signal to control the timing of the exposure period, wherein a length of a period of the second timing is longer than a length of a period of the first timing, the exposure period control unit generates the control signal indicating the timing of the exposure period having a time width of one of one period of the first timing divided into a plurality of periods in the first mode, and the exposure period control unit determines the timing of the exposure period in the second mode based on a frequency distribution in which a count value of the light receiving signal is associated with each of the plurality of exposure periods in the first mode. Effect of the Invention

[0007] According to the present invention, a photoelectric conversion device capable of shortening the measurement time is provided. [Brief description of the drawings]

[0008] [Figure 1] 1 is a hardware block diagram showing an example of a schematic configuration of a distance measuring device according to a first embodiment. [Diagram 2] 1 is a schematic diagram showing the overall configuration of a photoelectric conversion device according to a first embodiment. [Diagram 3] 1 is a schematic block diagram showing an example of the configuration of a sensor substrate according to a first embodiment. [Figure 4] 1 is a schematic block diagram showing an example of the configuration of a circuit board according to a first embodiment. [Diagram 5] 2 is a schematic block diagram showing an example of the configuration of one pixel of a photoelectric conversion unit and a pixel signal processing unit according to the first embodiment. FIG. [Figure 6] 3A to 3C are diagrams illustrating the operation of the avalanche photodiode according to the first embodiment. [Figure 7] 1 is a functional block diagram showing a schematic configuration example of a distance measuring device according to a first embodiment. [Figure 8] 3A to 3C are schematic diagrams for explaining a ranging frame, and subframes and microframes in a first mode period and a second mode period according to the first embodiment. [Figure 9] 4 is a timing chart showing a distance measuring method according to the first embodiment. [Figure 10] 3A to 3C are schematic diagrams showing frequency distributions acquired by the distance measuring method according to the first embodiment. [Figure 11] 4 is a timing chart showing a distance measuring method according to the first embodiment. [Figure 12] 3A to 3C are schematic diagrams showing frequency distributions acquired by the distance measuring method according to the first embodiment. [Figure 13] FIG. 11 is a functional block diagram showing an example of a schematic configuration of a photoelectric conversion device and a distance measurement processing device according to a second embodiment. [Figure 14] 13A and 13B are schematic diagrams for explaining a ranging frame and sub-frames in a first mode period and a second mode period according to a second embodiment. [Figure 15] 13 is a timing chart showing a distance measuring method according to the third embodiment. [Figure 16] 13 is a timing chart showing a distance measuring method according to the third embodiment. [Figure 17] 13A to 13C are schematic diagrams showing frequency distributions obtained by a distance measuring method according to a third embodiment. [Figure 18] 13 is a timing chart showing a distance measuring method according to the fourth embodiment. [Figure 19] 13A to 13C are schematic diagrams showing frequency distributions acquired by a distance measuring method according to a fourth embodiment. [Figure 20] 13 is a timing chart showing a distance measuring method according to the fourth embodiment. [Figure 21] 13A to 13C are schematic diagrams showing frequency distributions acquired by a distance measuring method according to a fourth embodiment. [Figure 22] FIG. 13 is a schematic diagram of a device according to a fifth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same elements or corresponding elements in multiple drawings are denoted by the same reference numerals, and the description thereof may be omitted or simplified.

[0010] [First embodiment] 1 is a hardware block diagram showing a schematic configuration example of a distance measuring device 1 according to this embodiment. The distance measuring device 1 has a light emitting device 2, a signal processing circuit 3, and a light receiving device 4. Note that the configuration of the distance measuring device 1 shown in this embodiment is just an example, and is not limited to the configuration shown in the figure.

[0011] The distance measuring device 1 is a device that measures the distance to the object X to be measured using technology such as LiDAR (Light Detection And Ranging). The distance measuring device 1 measures the distance from the distance measuring device 1 to the object X based on the time difference between when light emitted from the light emitting device 2 is reflected by the object X and when it is received by the light receiving device 4. The distance measuring device 1 can also measure the distance to multiple points two-dimensionally by emitting laser light to a predetermined distance measuring range including the object X and receiving the reflected light with a pixel array. This allows the distance measuring device 1 to generate and output a distance image.

[0012] The light received by the light receiving device 4 includes ambient light such as sunlight in addition to the reflected light from the object X. Therefore, the distance measuring device 1 performs distance measurement with reduced influence of ambient light by using a method in which the light incident during each of a plurality of periods (exposure periods) is measured to generate a frequency distribution, and it is determined that the reflected light is incident during the period in which the amount of light is maximum.

[0013] The light emitting device 2 is a device that emits light such as laser light to the outside of the distance measuring device 1. The signal processing circuit 3 may include a processor that performs arithmetic processing of digital signals, a memory that stores digital signals, etc. The signal processing circuit 3 may be an integrated circuit such as a field-programmable gate array (FPGA) or an image signal processor (ISP).

[0014] The light receiving device 4 generates a pulse signal including a pulse based on the incident light. The light receiving device 4 is, for example, a photoelectric conversion device including an avalanche photodiode as a photoelectric conversion element. In this case, when one photon is incident on the avalanche photodiode and an electric charge is generated, one pulse is generated by avalanche multiplication. However, the light receiving device 4 may be, for example, a photoelectric conversion element using another photodiode. In other words, the distance measuring device 1 is a type of photoelectric conversion device that performs distance measurement using photoelectric conversion.

[0015] In this embodiment, the light receiving device 4 includes a pixel array in which a plurality of photoelectric conversion elements (pixels) are arranged to form a plurality of rows and a plurality of columns. Here, a photoelectric conversion device, which is a specific configuration example of the light receiving device 4, will be described with reference to Figs. 2 to 6. The configuration example of the photoelectric conversion device described below is one example. The photoelectric conversion device applicable to the light receiving device 4 is not limited to this, and may be any device capable of realizing the function of Fig. 7 described later.

[0016] FIG. 2 is a schematic diagram showing the overall configuration of a photoelectric conversion device 100 according to this embodiment. The photoelectric conversion device 100 has a sensor substrate 11 (first substrate) and a circuit substrate 21 (second substrate) that are stacked on each other. The sensor substrate 11 and the circuit substrate 21 are electrically connected to each other. The sensor substrate 11 has a pixel region 12 in which a plurality of pixels 101 are arranged to form a plurality of rows and a plurality of columns. The circuit substrate 21 has a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged to form a plurality of rows and a plurality of columns, and a second circuit region 23 arranged on the periphery of the first circuit region 22. The second circuit region 23 may include a circuit for controlling the plurality of pixel signal processing units 103. The sensor substrate 11 has a light incident surface that receives incident light and a connection surface that faces the light incident surface. The sensor substrate 11 is connected to the circuit substrate 21 on the connection surface side. That is, the photoelectric conversion device 100 is a so-called back-illuminated type.

[0017] In this specification, "planar view" refers to a view from a direction perpendicular to the surface opposite to the light incident surface. Also, a cross section refers to a surface in a direction perpendicular to the surface opposite to the light incident surface of the sensor substrate 11. Note that the light incident surface may be rough when viewed microscopically, and in such a case, the planar view is defined based on the light incident surface when viewed macroscopically.

[0018] In the following description, the sensor substrate 11 and the circuit substrate 21 are described as being diced chips, but the sensor substrate 11 and the circuit substrate 21 are not limited to being chips. For example, the sensor substrate 11 and the circuit substrate 21 may be wafers. In addition, when the sensor substrate 11 and the circuit substrate 21 are diced chips, the photoelectric conversion device 100 may be manufactured by stacking them in a wafer state and then dicing them, or may be manufactured by stacking them after dicing.

[0019] 3 is a schematic block diagram showing an example of the arrangement of the sensor substrate 11. A plurality of pixels 101 arranged in a plurality of rows and a plurality of columns are arranged in the pixel region 12. Each of the plurality of pixels 101 has a photoelectric conversion unit 102 including an avalanche photodiode (hereinafter referred to as APD) as a photoelectric conversion element within the substrate.

[0020] The conductivity type of the charge pair generated in the APD and used as the signal charge is called the first conductivity type. The first conductivity type refers to a conductivity type in which the charge of the same polarity as the signal charge is the majority carrier. The conductivity type opposite to the first conductivity type, that is, the conductivity type in which the charge of the opposite polarity to the signal charge is the majority carrier, is called the second conductivity type. In the APD described below, the anode of the APD is at a fixed potential, and a signal is taken out from the cathode of the APD. Therefore, the semiconductor region of the first conductivity type is an N-type semiconductor region, and the semiconductor region of the second conductivity type is a P-type semiconductor region. The cathode of the APD may be at a fixed potential, and the signal may be taken out from the anode of the APD. In this case, the semiconductor region of the first conductivity type is a P-type semiconductor region, and the semiconductor region of the second conductivity type is an N-type semiconductor region. In the following, a case in which one node of the APD is at a fixed potential will be described, but the potentials of both nodes may be fluctuating.

[0021] 4 is a schematic block diagram showing a configuration example of the circuit board 21. The circuit board 21 has a first circuit area 22 in which a plurality of pixel signal processing units 103 are arranged to form a plurality of rows and a plurality of columns.

[0022] Further, a vertical scanning circuit 110, a horizontal scanning circuit 111, a readout circuit 112, pixel output signal lines 113, an output circuit 114, and a control signal generating unit 115 are arranged on the circuit board 21. The multiple photoelectric conversion units 102 shown in Fig. 3 and the multiple pixel signal processing units 103 shown in Fig. 4 are electrically connected to each other via connection wiring provided for each pixel 101.

[0023] The control signal generating unit 115 is a control circuit that generates control signals for driving the vertical scanning circuit 110, the horizontal scanning circuit 111, and the readout circuit 112, and supplies these circuits with these signals. In this way, the control signal generating unit 115 controls the drive timing of each circuit.

[0024] The vertical scanning circuit 110 supplies a control signal to each of the pixel signal processing units 103 based on the control signal supplied from the control signal generation unit 115. The vertical scanning circuit 110 supplies a control signal to each pixel signal processing unit 103 for each row via a drive line provided for each row of the first circuit area 22. As will be described later, there may be multiple drive lines for each row. The vertical scanning circuit 110 may include logic circuits such as a shift register and an address decoder. In this way, the vertical scanning circuit 110 selects a row for outputting a signal from the pixel signal processing unit 103.

[0025] The signal output from the photoelectric conversion unit 102 of the pixel 101 is processed by the pixel signal processing unit 103. The pixel signal processing unit 103 counts the number of pulses output from the APD included in the photoelectric conversion unit 102 to obtain and hold a digital signal.

[0026] It is not necessary that one pixel signal processing unit 103 is provided for each pixel 101. For example, one pixel signal processing unit 103 may be shared by a plurality of pixels 101. In this case, the pixel signal processing unit 103 provides a signal processing function to each pixel 101 by sequentially processing the signals output from each photoelectric conversion unit 102.

[0027] The horizontal scanning circuit 111 supplies a control signal to the readout circuit 112 based on the control signal supplied from the control signal generation unit 115. The pixel signal processing unit 103 is connected to the readout circuit 112 via a pixel output signal line 113 provided for each column of the first circuit region 22. The pixel output signal line 113 of one column is shared by a plurality of pixel signal processing units 103 of the corresponding column. The pixel output signal line 113 includes a plurality of wirings, and has at least a function of outputting a digital signal from each pixel signal processing unit 103 to the readout circuit 112 and a function of supplying a control signal for selecting a column for outputting a signal to the pixel signal processing unit 103. The readout circuit 112 outputs a signal to a storage unit or a signal processing unit outside the photoelectric conversion device 100 via the output circuit 114 based on the control signal supplied from the control signal generation unit 115.

[0028] The photoelectric conversion units 102 in the pixel region 12 may be arranged one-dimensionally. Moreover, the function of the pixel signal processing unit 103 does not necessarily have to be provided for each pixel 101. For example, one pixel signal processing unit 103 may be shared by a plurality of pixels 101. In this case, the pixel signal processing unit 103 provides a signal processing function to each pixel 101 by sequentially processing signals output from each photoelectric conversion unit 102.

[0029] 3 and 4, a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged is arranged in a region overlapping the pixel region 12 in a plan view. A vertical scanning circuit 110, a horizontal scanning circuit 111, a readout circuit 112, an output circuit 114, and a control signal generating unit 115 are arranged so as to overlap between an end of the sensor substrate 11 and an end of the pixel region 12 in a plan view. In other words, the sensor substrate 11 has the pixel region 12 and a non-pixel region arranged around the pixel region 12. In the circuit substrate 21, a second circuit region 23 (described above in FIG. 2) in which the vertical scanning circuit 110, the horizontal scanning circuit 111, the readout circuit 112, the output circuit 114, and the control signal generating unit 115 are arranged is arranged in a region overlapping the non-pixel region in a plan view.

[0030] The arrangement of the pixel output signal lines 113, the readout circuits 112, and the output circuits 114 are not limited to those shown in Fig. 4. For example, the pixel output signal lines 113 may be arranged to extend in the row direction and shared by a plurality of pixel signal processing units 103 in the corresponding row. The readout circuits 112 may be arranged so that the pixel output signal lines 113 in each row are connected to each other.

[0031] Fig. 5 is a schematic block diagram showing a configuration example of one pixel of the photoelectric conversion unit 102 and pixel signal processing unit 103 according to this embodiment. Fig. 5 shows a more specific configuration example including a connection relationship between the photoelectric conversion unit 102 arranged on the sensor substrate 11 and the pixel signal processing unit 103 arranged on the circuit substrate 21. Note that in Fig. 5, the drive lines between the vertical scanning circuit 110 and the pixel signal processing unit 103 in Fig. 4 are shown as drive lines 213, 214, and 215.

[0032] The photoelectric conversion unit 102 has an APD 201. The pixel signal processing unit 103 has a quenching element 202, a waveform shaping unit 210, a counter circuit 211, a selection circuit 212, and a gating circuit 216. It is sufficient that the pixel signal processing unit 103 has at least one of the waveform shaping unit 210, the counter circuit 211, the selection circuit 212, and the gating circuit 216.

[0033] The APD 201 generates charges according to incident light by photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD 201. A cathode of the APD 201 is connected to a first terminal of the quench element 202 and an input terminal of the waveform shaping unit 210. A voltage VH (second voltage) higher than the voltage VL supplied to the anode is supplied to the cathode of the APD 201. As a result, a reverse bias voltage is supplied to the anode and cathode of the APD 201 such that the APD 201 performs avalanche multiplication. When charges are generated by incident light in the APD 201 to which the reverse bias voltage is supplied, the charges undergo avalanche multiplication, generating an avalanche current.

[0034] In addition, there are two operation modes when a reverse bias voltage is supplied to the APD 201: Geiger mode and linear mode. The Geiger mode is a mode in which the APD 201 operates with a potential difference between the anode and cathode that is greater than the breakdown voltage, and the linear mode is a mode in which the APD 201 operates with a potential difference between the anode and cathode that is close to or less than the breakdown voltage.

[0035] An APD operated in Geiger mode is called a SPAD (Single Photon Avalanche Diode). In this case, 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. In the case of a SPAD, the potential difference is larger than that of an APD in linear mode, and the effect of avalanche multiplication is more pronounced, so a SPAD is preferable.

[0036] The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication. The quench element 202 suppresses the voltage supplied to the APD 201 to suppress avalanche multiplication (quench operation). The quench element 202 also returns the voltage supplied to the APD 201 to the voltage VH by passing a current corresponding to the voltage drop caused by the quench operation (recharge operation). The quench element 202 can be, for example, a resistive element.

[0037] The waveform shaping unit 210 shapes the potential change of the cathode of the APD 201 obtained when a photon is detected, and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping unit 210. Although an example in which one inverter is used as the waveform shaping unit 210 is shown in Fig. 5, the waveform shaping unit 210 may be a circuit in which a plurality of inverters are connected in series, or may be another circuit having a waveform shaping effect.

[0038] The gating circuit 216 is a circuit that performs gating such that the pulse signal output from the waveform shaping unit 210 passes only for a predetermined period. During the period during which the pulse signal can pass through the gating circuit 216, photons incident on the APD 201 are counted by the counter circuit 211 at the rear stage. Therefore, the gating circuit 216 controls the exposure period during which a signal is generated based on the incident light in the pixel 101. The period during which the pulse signal passes is controlled by a control signal supplied from the vertical scanning circuit 110 via the drive line 215. FIG. 5 shows an example in which one AND circuit is used as the gating circuit 216. A pulse signal and a control signal are input to two input terminals of the AND circuit. The AND circuit outputs the logical product of these to the counter circuit 211. Note that the gating circuit 216 may have a circuit configuration other than an AND circuit as long as it can realize gating. In addition, the waveform shaping unit 210 and the gating circuit 216 may be integrated by using a logic circuit such as a NAND circuit.

[0039] The counter circuit 211 counts the pulse signals output from the waveform shaping unit 210 via the gating circuit 216, and holds a digital signal indicating the count value. When a control signal is supplied from the vertical scanning circuit 110 via the drive line 213, the counter circuit 211 resets the held signal. The counter circuit 211 can be, for example, a 1-bit counter.

[0040] A control signal is supplied to the selection circuit 212 from the vertical scanning circuit 110 shown in Fig. 4 via a drive line 214 shown in Fig. 5. In response to this control signal, the selection circuit 212 switches between electrical connection and non-connection between the counter circuit 211 and the pixel output signal line 113. The selection circuit 212 includes, for example, a buffer circuit for outputting a signal corresponding to a value held in the counter circuit 211.

[0041] 5, the selection circuit 212 switches between electrical connection and disconnection between the counter circuit 211 and the pixel output signal line 113, but the method of controlling the signal output to the pixel output signal line 113 is not limited to this. For example, a switch such as a transistor may be disposed at a node between the quench element 202 and the APD 201, between the photoelectric conversion unit 102 and the pixel signal processing unit 103, or the like, and the signal output to the pixel output signal line 113 may be controlled by switching between electrical connection and disconnection. Alternatively, the signal output to the pixel output signal line 113 may be controlled by changing the value of the voltage VH or voltage VL supplied to the photoelectric conversion unit 102 using a switch such as a transistor.

[0042] Figures 6(a), 6(b) and 6(c) are diagrams for explaining the operation of the APD 201 according to this embodiment. Figure 6(a) is a diagram showing the APD 201, the quench element 202 and the waveform shaping unit 210 extracted from Figure 5. As shown in Figure 6(a), the connection node of the APD 201, the quench element 202 and the input terminals of the waveform shaping unit 210 is referred to as nodeA. Also, as shown in Figure 6(a), the output side of the waveform shaping unit 210 is referred to as nodeB.

[0043] FIG. 6(b) is a graph showing the time change of the potential of nodeA in FIG. 6(a). FIG. 6(c) is a graph showing the time change of the potential of nodeB in FIG. 6(a). In the period from time t0 to time t1, a voltage of VH-VL is applied to the APD 201 in FIG. 6(a). When a photon is incident on the APD 201 at time t1, avalanche multiplication occurs in the APD 201. As a result, an avalanche current flows through the quench element 202, and the potential of nodeA drops. After that, the amount of potential drop further increases, and the voltage applied to the APD 201 gradually decreases. Then, at time t2, the avalanche multiplication in the APD 201 stops. As a result, the voltage level of nodeA does not drop below a certain value. After that, in the period from time t2 to time t3, a current that compensates for the voltage drop flows from the node of voltage VH to nodeA, and at time t3, nodeA settles to its original potential.

[0044] In the above process, the potential of node B becomes high during the period when the potential of node A is lower than a certain threshold. In this way, the waveform of the drop in the potential of node A caused by the incidence of a photon is shaped by the waveform shaping unit 210 and output as a pulse to node B.

[0045] Next, the overall configuration and operation of the distance measuring device 1 will be described in more detail. Fig. 7 is a functional block diagram showing an example of a schematic configuration of the distance measuring device 1 according to this embodiment. The distance measuring device 1 has a light emitting unit 120, a light receiving unit 140, a timing generating unit 131, an exposure period control unit 132, a frequency distribution holding unit 133, a peak detecting unit 134, and an output unit 135.

[0046] The light emitting unit 120 corresponds to the light emitting device 2 in Fig. 1. The light receiving unit 140 corresponds to the light receiving device 4 in Fig. 1. The timing generating unit 131, the exposure period control unit 132, the frequency distribution holding unit 133, the peak detecting unit 134, and the output unit 135 correspond to the signal processing circuit 3 in Fig. 1.

[0047] The distance measuring device 1 of this embodiment performs a process in a first mode and a process in a second mode in one frame period. The second mode period in which the process in the second mode is performed is after the first mode period in which the process in the first mode is performed.

[0048] The timing generation unit 131 generates a first timing that is repeated at a predetermined cycle in the first mode. In addition, the timing generation unit 131 generates a second timing that is repeated at a cycle different from the first timing in the second mode. The first timing and the second timing are signals that indicate periodic light emission timing in the light emission unit 120. A period between a certain first timing and the next first timing, or a period between a certain second timing and the next second timing, may be called a microframe period. Also, a microframe period in the first mode may be called a first microframe period, and a microframe period in the second mode may be called a second microframe period.

[0049] The timing generation unit 131 supplies the generated first timing or second timing to the light-emitting unit 120 and the exposure period control unit 132. The light-emitting unit 120 emits pulsed light at a light-emitting timing based on the first timing or the second timing. That is, the light-emitting unit 120 emits pulsed light once within one microframe period with mutually different cycles in each of the first mode and the second mode. A part of the emitted pulsed light may be reflected by the object X and enter the light-receiving unit 140.

[0050] In the first mode, the exposure period control unit 132 determines the start timing of the exposure period in the light receiving unit 140 based on the first timing. The length of the exposure period can be set appropriately. The length of the exposure period affects the distance measurement resolution in the distance measuring device 1. That is, if the exposure period is set to be short, the distance resolution increases, and if the exposure period is set to be long, the distance resolution decreases. In addition, the exposure period control unit 132 acquires information (peak information) indicating the exposure period corresponding to the maximum value (peak) of the frequency distribution acquired in the first mode from the peak detection unit 134. In the second mode, the exposure period control unit 132 determines the start timing of the exposure period in the light receiving unit 140 based on the second timing based on the peak information. The exposure period control unit 132 generates a control signal for controlling the timing of the exposure period, and outputs it to the light receiving unit 140 and the frequency distribution holding unit 133.

[0051] One exposure period exists within one microframe period. After the end of a plurality of microframe periods in which exposure is performed at the same start timing, the start timing of the exposure period is shifted, and a plurality of microframe periods in which exposure is performed at the shifted start timing are started. In this specification, a plurality of microframe periods in which exposure is performed at the same start timing is called a subframe period. Therefore, the exposure period control unit 132 controls so as to shift the exposure period every time a subframe period elapses. In the first mode, the exposure period control unit 132 shifts the start timing of the exposure period by the length of the exposure period every time a subframe period elapses. In the second mode, the exposure period control unit 132 typically shifts the start timing of the exposure period by the length of the first microframe period every time a subframe period elapses. However, the operation of the second mode in this embodiment is not limited thereto.

[0052] When light is incident on the light receiving unit 140 during the exposure period, the light receiving unit 140 converts the received light into an electrical signal pulse. The light receiving unit 140 may be, for example, the photoelectric conversion device 100 shown in Fig. 2 to Fig. 6. The output signal of the light receiving unit 140 is output to the frequency distribution holding unit 133.

[0053] The frequency distribution holding unit 133 holds the multiple signals input from the light receiving unit 140 as a frequency distribution of the count values ​​of the light receiving signals generated by the light receiving unit 140 in each of the multiple exposure periods. That is, the frequency distribution holding unit 133 has a function of storing information in which the exposure periods and the count values ​​of the light receiving signals are associated with each other as a frequency distribution. A frequency distribution generated in a first mode of the exposure periods and the count values ​​of the light receiving signals may be referred to as a first frequency distribution, and a frequency distribution generated in a second mode of the exposure periods and the count values ​​of the light receiving signals may be referred to as a second frequency distribution.

[0054] The peak detection unit 134 performs a peak detection process to detect an exposure period corresponding to a maximum value (peak) of the frequency distribution based on the frequency distribution held in the frequency distribution holding unit 133. The peak detection unit 134 outputs information (peak information) indicating the exposure period corresponding to the maximum value of the frequency distribution to the exposure period control unit 132 in the first mode, and outputs the information to the output unit 135 in the second mode.

[0055] The output unit 135 acquires peak information from the peak detection unit 134 every time one frame period elapses, and outputs it as distance information to the outside of the distance measuring device 1. Alternatively, the output unit 135 may acquire a frequency distribution from the frequency distribution holding unit 133, and output it to the outside.

[0056] FIG. 8 is a schematic diagram for explaining the ranging frame, the first mode period, the second mode period, the subframe, and the microframe according to the present embodiment. The relationship between the ranging frame, the first mode period, the second mode period, the subframe, and the microframe described above will be described in more detail with reference to FIG. 8. In FIG. 8, the acquisition period of a ranging frame corresponding to one ranging result, the acquisition period of a subframe used to generate the ranging frame, and the acquisition period of a microframe used to generate the subframe are shown by arranging blocks in the horizontal direction. The horizontal direction in FIG. 8 indicates the passage of time, and one block indicates the acquisition period of one ranging frame, subframe, or microframe. In addition, FIG. 8 shows a control signal for controlling the light emission period of the light emitting unit 120 and an exposure control signal for controlling the exposure period in the light receiving unit 140.

[0057] In the "distance measurement period" in Fig. 8, multiple frame periods FL_1, FL_2, ... included in one distance measurement period are shown. Frame period FL_1 indicates the first frame period in one distance measurement period, and frame period FL_2 indicates the second frame period in one distance measurement period. A frame period is a period during which the distance measurement device 1 performs one distance measurement and outputs a signal indicating the distance (distance measurement result) from the distance measurement device 1 to the object X to the outside. Note that Fig. 8 shows an example in which peaks are determined and output from the frequency distribution (peak detection period PDTC and peak output period POUT) within the distance measurement device 1, but this is not essential.

[0058] One ranging frame period includes a first mode period MD_1, a second mode period MD_2, a peak detection period PDTC for detecting a peak from the frequency distribution, and a peak output period POUT for outputting peak information based on the peak detected from the frequency distribution. As shown in "Frame Period" in Fig. 8, the peak detection period PDTC is set after the completion of the first mode period MD_1 and before the start of the second mode period MD_2. Also, the peak output period POUT is set after the completion of the second mode period MD_2.

[0059] Each of the first mode period and the second mode period includes a plurality of subframe periods. In the portion of the "first and second mode periods" in FIG. 8 corresponding to the first mode period MD_1, a plurality of subframe periods SF1_1, SF1_2, ..., SF1_p are shown. The subframe period SF1_1 indicates the first subframe period in the first mode period MD_1, and the subframe period SF1_2 indicates the second subframe period in the first mode period MD_1. In this embodiment, the number of subframe periods in the first mode period MD_1 is p (p is an integer equal to or greater than 2). The subframe period SF1_p indicates the pth subframe period in the first mode period MD_1.

[0060] Similarly, a portion of the "first and second mode periods" in FIG. 8 that corresponds to the second mode period MD_2 shows a plurality of subframe periods SF2_1, SF2_2, ..., SF2_q. Subframe period SF2_1 indicates the first subframe period in the second mode period MD_2, and subframe period SF2_2 indicates the second subframe period in the second mode period MD_2. In this embodiment, the number of subframe periods in the second mode period MD_2 is q (q is an integer equal to or greater than 2). Subframe period SF2_q indicates the qth subframe period in the second mode period MD_2.

[0061] One subframe is generated from multiple microframes. In the "subframe period" of FIG. 8, multiple microframe periods MF1_1, MF1_2, ..., MF1_r included in one subframe period in the first mode period MD_1 are shown. The microframe period MF1_1 indicates the first microframe period in one subframe period in the first mode period MD_1. The microframe period MF1_2 indicates the second microframe period in one subframe period in the first mode period MD_1. In this embodiment, the number of microframes per one subframe in the first mode period MD_1 is r (r is an integer equal to or greater than 2). The microframe period MF_r indicates the rth microframe period in one subframe period. The number r of microframes corresponds to the number of times the light reception results are integrated in the first mode period MD_1.

[0062] Similarly, in the "subframe period" of FIG. 8, a plurality of microframe periods MF2_1, MF2_2, ..., MF2_s included in one subframe period in the second mode period MD_2 are shown. The microframe period MF2_1 indicates the first microframe period in one subframe period in the second mode period MD_2. The microframe period MF2_2 indicates the second microframe period in one subframe period in the second mode period MD_2. In this embodiment, the number of microframes per one subframe in the second mode period MD_2 is s (s is an integer of 2 or more). The microframe period MF_s indicates the sth microframe period in one subframe period. This number of microframes s corresponds to the number of times that the light reception results are integrated in the second mode period MD_2.

[0063] "Light Emission" and "Exposure Control Signal" in FIG. 8 respectively indicate the light emission period of the light emission unit 120 and the exposure control signal input to the light receiving unit 140 in one microframe period. The light emission unit 120 emits light during a period when "light emission" is at a high level. The light emission unit 120 emits light during a light emission period L1_1 in a microframe period MF1_1 in the first mode period MD_1, and emits light during a light emission period L1_2 in a microframe period MF1_2 in the first mode period MD_1. The start time of the light emission period L1_1 and the start time of the light emission period L1_2 correspond to the first timing described above. Moreover, the light emission unit 120 emits light during a light emission period L2_1 in a microframe period MF2_1 in the second mode period MD_2, and emits light during a light emission period L2_2 in a microframe period MF2_2 in the second mode period MD_2. The start time of the light emission period L2_1 and the start time of the light emission period L2_2 correspond to the second timing described above. The light emission period in the first mode period MD_1 is shorter than the light emission period in the second mode period MD_2. As a typical example, the light emission period in the second mode period MD_2 can be an integer multiple of the light emission period in the first mode period MD_1, but the ratio of the light emission period in the second mode period MD_2 to the light emission period in the first mode period MD_1 is not limited to an integer.

[0064] The light receiving unit 140 detects incident light when light is incident during an exposure period in which the "exposure control signal" output from the exposure period control unit 132 is at a high level. In a microframe period MF1_1 in the first mode period MD_1, incident light is detected during exposure period E1_1. In a microframe period MF1_2 in the first mode period MD_1, incident light is detected during exposure period E1_2. In a microframe period MF2_1 in the second mode period MD_2, incident light is detected during exposure period E2_1. In a microframe period MF2_2 in the second mode period MD_2, incident light is detected during exposure period E2_2.

[0065] In the first mode period MD_1, a period T_k1 from the start of the light emission period L1_1 to the start of the exposure period E1_1 and a period T_k2 from the start of the light emission period L1_1 to the start of the exposure period E1_2 are the flight periods of light from light emission to light reception in the light emission period L1_1. That is, in the exposure period E1_n of the microframe period MF1_n (n is an integer of 2 or more), the light emitted in the light emission period L1_n and the light emitted in the light emission period L1_(n-1) are detected. As a result, it is detected whether or not the object X is present at a distance corresponding to the period T1_k1 and the period T1_k2. Note that in this example, the time interval between the exposure period E1_n and the light emission period L1_(n-2) is sufficiently large, and the exposure period E1_n is not affected by the reflected light generated by the light emitted in the light emission period L1_(n-2) being reflected by the object X. Also, k is the number of the corresponding subframe period and is an integer from 1 to p.

[0066] In the second mode period MD_2, a period T2_j from the start of the light emission period L2_1 to the start of the exposure period E2_1 is the flight period of light from emission to reception in the light emission period L2_1. That is, in the exposure period E2_m of the microframe period MF2_m (m is an integer of 2 or more), detection of light emitted in the light emission period L2_m is performed. This allows detection of whether or not an object X is present at a distance equivalent to the period T2_j. Note that j is the number of the corresponding subframe period and is an integer from 1 to q.

[0067] In the first mode period MD_1, light reception data is read (microframes are acquired) r times in one subframe period. When a photon is detected one or more times in one microframe period, the light receiving unit 140 outputs "1" as the light reception data. By accumulating the r microframes acquired in one subframe period, data indicating the number of microframes in which a photon was detected is generated.

[0068] In each of the subframe periods SF1_1, SF1_2, ..., SF1_p, the lengths of the periods T1_11, T1_21, ..., T1_p1 and the periods T1_12, T1_22, ..., T1_p2 are different from each other. As a result, in each of the subframe periods SF1_1, SF1_2, ..., SF1_p, a frequency distribution of the light reception count value at different distances is obtained. In the peak detection period PDTC, a peak of the frequency distribution is detected by obtaining the maximum value of the light reception count value in each of the subframe periods SF1_1, SF1_2, ..., SF1_p. One of the lengths of the periods T1_k1 and T1_k2 corresponding to this peak is proportional to the distance from the distance measuring device 1 to the object X.

[0069] Similarly, in the second mode period MD_2, light reception data is read out s times (microframe acquisition) in one subframe period. When a photon is detected one or more times in one microframe period, the light receiving unit 140 outputs "1" as the light reception data. By accumulating the s microframes acquired in one subframe period, data indicating the number of microframes in which photons were detected is generated.

[0070] In each of the multiple subframe periods SF2_1, SF2_2, ..., SF2_q, the lengths of the periods T2_1, T2_2, ..., T2_q are different from each other. In the example of this embodiment, in the first mode period MD_1, it is detected that the object X is present at a distance corresponding to either the period T1_k1 or the period T1_k2. Therefore, in the second mode period MD_2, the number of subframes q is set to 2, and a measurement is performed to determine whether the object X is present at a distance corresponding to either the period T1_k1 or the period T1_k2. That is, in the subframe period SF2_1, the exposure period E2_1 is set to the timing of the period T1_k1, and in the subframe period SF2_2, the exposure period E2_2 is set to the timing of the period T1_k2, and the measurement is performed.

[0071] Next, the operation method of this embodiment will be described with reference to Fig. 9(a) to Fig. 12. In the following description, a measurement method is exemplified in which a period corresponding to the distance measurement range is divided into 10 periods, and it is determined at which of the 10 periods the object X exists. However, this method is merely an example in this embodiment, and the present invention is not limited to this.

[0072] 9(a) and 9(b) are timing charts showing the relationship between the light emission timing of the light-emitting unit 120 in the first mode period MD_1 and the exposure period of the light-receiving unit 140. FIG. 9(a) is a timing chart of the first sub-frame period SF1_1 in the first mode period MD_1. FIG. 9(a) shows the light emission periods L1_11, L1_12, L1_13, and L1_14 and the exposure periods E1_11, E1_12, E1_13, and E1_14 in the first sub-frame period SF1_1. FIG. 9(a) also shows a numerical value proportional to the flight time of light from the emission of light in the light emission periods L1_11 and L1_13 to the reception of light as the "first flight time". FIG. 9(a) also shows a numerical value proportional to the flight time of light from the emission of light in the light emission periods L1_12 and L1_14 to the reception of light as the "second flight time". These flight times are proportional to the distance from the distance measuring device 1 to the object X. The exposure period E1_11 is a period during which the reflected light emitted in the light emission period L1_11 and having a flight time of "1" can be received. The exposure period E1_12 is a period during which the reflected light emitted in the light emission period L1_12 and having a flight time of "1" and the reflected light emitted in the light emission period L1_11 and having a flight time of "6" can be received. Similarly, the exposure period E1_13 is a period during which the reflected light emitted in the light emission period L1_13 and having a flight time of "1" and the reflected light emitted in the light emission period L1_12 and having a flight time of "6" can be received.

[0073] FIG. 9(b) is a timing chart of the second subframe period SF1_2 in the first mode period MD_1. FIG. 9(b) shows the light emission periods L1_21, L1_22, L1_23, and L1_24 and the exposure periods E1_21, E1_22, E1_23, and E1_24 in the subframe period SF1_2. The notations of "first flight time" and "second flight time" are the same as those in FIG. 9(a). The exposure period E1_21 is a period during which the reflected light emitted in the light emission period L1_21 and having a flight time of "2" can be received. The exposure period E1_22 is a period during which the reflected light emitted in the light emission period L1_22 and having a flight time of "2" and the reflected light emitted in the light emission period L1_21 and having a flight time of "7" can be received. Similarly, the exposure period E1_23 is a period during which reflected light emitted in the light emission period L1_23 and having a flight time of "2" and reflected light emitted in the light emission period L1_22 and having a flight time of "7" can be received.

[0074] In this example, the first mode period MD_1 includes five sub-frame periods SF1_1 to SF1_5. The sub-frame periods SF1_3 to SF1_5 are obtained by shifting the exposure periods of the above-mentioned sub-frame periods SF1_1 and SF1_2, but are otherwise similar, and therefore will not be described.

[0075] FIG. 10 is a schematic diagram showing a frequency distribution acquired in the first mode period MD_1 by the distance measurement method according to the present embodiment. The horizontal axis of FIG. 10 is the value of the flight time corresponding to the position of the above-mentioned exposure period. As described above, flight times "1" and "6", flight times "2" and "7", flight times "3" and "8", flight times "4" and "9", and flight times "5" and "10" are measured in a mixed state. Therefore, the horizontal axis of FIG. 10 is written as "1" to "5" or "6" to "10". The vertical axis of FIG. 10 is the number of microframes in which light is detected in each exposure period, that is, the light reception count value. FIG. 10 shows an example in which the number of microframes per subframe is 10 in the operation of the above-mentioned first mode period MD_1, so the maximum value of the vertical axis is 10. In the example shown in Figure 10, the light receiving count value during the exposure period in which the flight time is "1" or "6" is the maximum, so the distance from the distance measuring device 1 to the target X is either the distance corresponding to the flight time "1" or the distance corresponding to the flight time "6."

[0076] Next, the process in the second mode period MD_2 will be described. In this example, in the measurement in the above-mentioned first mode period MD_1, peak information is obtained that the light reception count value is maximum in the exposure period in which the flight time is "1" or "6" as shown in Fig. 10. Therefore, in the second mode period MD_2, a measurement is performed in the subframe period SF2_1 in which the exposure period corresponding to the flight time "1" is set, and a measurement is performed in the subframe period SF2_2 in which the exposure period corresponding to the flight time "6" is set.

[0077] 11(a) and 11(b) are timing charts showing the relationship between the light emission timing of the light-emitting unit 120 in the second mode period MD_2 and the exposure period of the light-receiving unit 140. FIG. 11(a) is a timing chart of the first sub-frame period SF2_1 in the second mode period MD_2. FIG. 11(a) shows the light emission periods L2_11 and L2_12 and the exposure periods E2_11 and E2_12 in the first sub-frame period SF2_1. FIG. 11(a) also shows a numerical value proportional to the flight time of light from emission to reception in the light emission periods L2_11 and L2_12 as the "flight time". The exposure period E2_11 is a period during which reflected light that is emitted in the light emission period L2_11 and has a flight time of "1" can be received. The exposure period E2_12 is a period during which reflected light that is emitted during the light emission period L2_12 and has a flight time of "1" can be received. The duration of the exposure period of the second mode period MD_2 is set to be equal to the duration of the exposure period of the first mode period MD_1.

[0078] Fig. 11(b) is a timing chart of the second sub-frame period SF2_2 in the second mode period MD_2. Fig. 11(b) shows the light emission periods L2_21 and L2_22 and the exposure periods E2_21 and E2_22 in the sub-frame period SF2_2. The exposure period E2_21 is a period during which reflected light emitted in the light emission period L2_21 and having a flight time of "6" can be received. The exposure period E2_22 is a period during which reflected light emitted in the light emission period L2_22 and having a flight time of "6" can be received.

[0079] Fig. 12 is a schematic diagram showing a frequency distribution acquired in the second mode period MD_2 by the distance measuring method according to this embodiment. Fig. 12 shows an example in which the number of microframes per subframe is 10 in the operation of the above-mentioned second mode period MD_2, so the maximum value on the vertical axis is 10. In the example shown in Fig. 12, the light receiving count value in the exposure period in which the flight time is "6" is the maximum, so the distance from the distance measuring device 1 to the object X is the distance corresponding to the flight time of "6".

[0080] In the examples of FIG. 10 and FIG. 12, the number of microframes per subframe in both the first mode period MD_1 and the second mode period MD_2 is 10, but is not limited to this. For example, the number of microframes per subframe in the second mode period MD_2 may be less than the number of microframes per subframe in the first mode period MD_1. That is, the timing generation unit 131 may generate the second timing less times in one subframe period than the number of first timings in one subframe period. Since the second mode period MD_2 is a measurement for determining which of the distant exposure periods has the largest light reception count value, erroneous determination due to noise is less likely to occur compared to the case where the light reception count values ​​of adjacent exposure periods are compared as in the first mode period MD_1. Therefore, by setting the number of microframes per subframe in the second mode period MD_2 to be less than that in the first mode period MD_1, the distance measurement time can be shortened without significantly decreasing the distance measurement accuracy.

[0081] As described above, the distance measuring device 1 of this embodiment operates in a first mode and a second mode in which the light emission intervals are different from each other. The light emission interval (period of the second timing) in the second mode is longer than the light emission interval (period of the first timing) in the first mode. In the first mode, one period of the light emission timing is divided into a plurality of periods, and each period is set as an exposure period to measure the light reception count value. Then, the distance measuring device 1 determines the timing of the exposure period in the second mode period MD_2 based on the frequency distribution acquired in the first mode period MD_1. With this configuration, the total number of subframes in the first mode period MD_1 and the second mode period MD_2 can be reduced compared to the case where measurements are performed in each exposure period in one mode. Therefore, according to this embodiment, a distance measuring device 1 that can shorten the measurement time is provided.

[0082] The reduction in measurement time will be described more specifically. For example, in the examples of Figs. 9 to 12 described above, in the first mode period MD_1, measurements corresponding to two distances can be performed simultaneously in one exposure period, so the number of subframes is halved. Also, in the second mode period MD_2, the number of subframes is reduced to two. Thus, although two-stage measurements in the first mode period MD_1 and the second mode period MD_2 are required in this embodiment, the total number of subframes is reduced, so the measurement time per distance measurement frame is shortened.

[0083] The configuration and operation of the distance measuring device 1 of this embodiment are merely an example, and the present invention is not limited to this. Several modified examples of the configuration of each part of the distance measuring device 1 will be described.

[0084] The peak detection process in the peak detection unit 134 is not limited to detecting one exposure period corresponding to the maximum value of the light reception count value of the frequency distribution. For example, the peak detection unit 134 may detect multiple exposure periods in descending order of the light reception count value of the frequency distribution. The peak detection unit 134 may also detect an exposure period in which the light reception count value of the frequency distribution exceeds a threshold value. Here, the magnitude of the threshold value may be common to each exposure period, or may be different for each exposure period. In this configuration, the peak detection unit 134 may detect one or multiple exposure periods in descending order of the light reception count value from among multiple exposure periods in which the light reception count value of the frequency distribution exceeds a threshold value.

[0085] When the peak detection unit 134 detects a plurality of exposure periods in the first mode period MD_1 as in some of the above examples, the exposure period control unit 132 determines the exposure period of the second mode period based on the detected plurality of exposure periods. On the other hand, when the peak detection unit 134 does not detect an exposure period in the first mode period MD_1, the exposure period control unit 132 may perform control so as not to perform the operation of the second mode period MD_2. Alternatively, in this case, the peak detection unit 134 or the exposure period control unit 132 may output a signal indicating that no peak exists to the timing generation unit 131 to stop the output operation of the second timing. In this case, the operation of the light emission unit 120 and the exposure period control unit 132 in the second mode period MD_2 is stopped.

[0086] The frequency distribution storage unit 133 may store the first frequency distribution acquired in the first mode period MD_1 and the second frequency distribution acquired in the second mode period MD_2 separately. On the other hand, the frequency distribution storage unit 133 may overwrite the first frequency distribution acquired in the first mode period MD_1 when acquiring the second frequency distribution in the second mode period MD_2. In this case, the storage capacity of the frequency distribution storage unit 133 may be reduced.

[0087] The timing generation unit 131 may set the period of the second timing to three times the period of the first timing, or may set it to an integer multiple greater than three. Moreover, the period of the second timing is not limited to an integer multiple of the period of the first timing. When the period of the second timing is three times the period of the first timing, typically, the number of subframe periods in the second mode period MD_2 is set to three, and measurements are performed in three different exposure periods in these three subframe periods.

[0088] Furthermore, one cycle of the second timing in the second mode period MD_2 may include a ranging period in which an exposure period is set and a non-ranging period in which an exposure period is not set. The non-ranging period is arranged in the period between the ranging period of one cycle of the second timing and the light emission of the next cycle. By arranging the non-ranging period, the influence of noise caused by receiving reflected light from an object X located farther away than the set ranging range during the exposure period of the next cycle can be reduced. When the period of one cycle of the second timing includes the non-ranging range, for example, the cycle of the second timing can be set to three times the cycle of the first timing, and the number of subframe periods in the second mode period MD_2 can be set to two.

[0089] [Second embodiment] In this embodiment, a configuration example in which the frequency distribution storage unit 133 and the peak detection unit 134 are disposed in a device external to the photoelectric conversion device will be described. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0090] FIG. 13 is a functional block diagram showing a schematic configuration example of a photoelectric conversion device and a distance measurement processing device according to this embodiment. In this embodiment, a system corresponding to the distance measurement device 1 of the first embodiment is composed of two devices, a photoelectric conversion device 1a and a distance measurement processing device 1b. The photoelectric conversion device 1a has a light emitting unit 120, a light receiving unit 140, a timing generating unit 131, an exposure period control unit 132, a count value holding unit 136, and an output unit 137. The distance measurement processing device 1b has a frequency distribution holding unit 133, a peak detection unit 134, and an output unit 135. Thus, in this embodiment, the frequency distribution holding unit 133 and the peak detection unit 134 are arranged in the distance measurement processing device 1b outside the photoelectric conversion device 1a. The photoelectric conversion device 1a and the distance measurement processing device 1b cooperate to form a distance measurement system that performs distance measurement similar to that of the distance measurement device 1 of the first embodiment.

[0091] The exposure period control unit 132 acquires information (peak information) indicating an exposure period corresponding to a peak of the frequency distribution acquired in the first mode from a peak detection unit 134 arranged in the distance measurement processing device 1b outside the photoelectric conversion device 1a. In the second mode, the exposure period control unit 132 determines a start timing of an exposure period in the light receiving unit 140 based on the second timing, based on the peak information. The exposure period control unit 132 outputs a control signal indicating the exposure period to the light receiving unit 140 and the count value holding unit 136. Alternatively, the exposure period control unit 132 may acquire exposure period setting information based on the peak information from the peak detection unit 134, and generate a control signal based on the exposure period setting information.

[0092] The count value holding unit 136 counts the light reception signals output from the light receiving unit 140 and holds them as a light reception count value of the incident light. The output unit 137 outputs the light reception count value held in the count value holding unit 136 to a distance measurement processing device 1b outside the photoelectric conversion device 1a every time a subframe period elapses. The frequency distribution holding unit 133 of the distance measurement processing device 1b generates a frequency distribution based on the light reception count value of each subframe period. The processing after the generation of the frequency distribution is the same as in the first embodiment.

[0093] 14 is a schematic diagram for explaining a ranging frame according to this embodiment and subframes in the first mode period and the second mode period. Note that the relationship between the subframes and the microframes is the same as in the first embodiment, so the explanation is omitted. In the "ranging period" in FIG. 14, multiple frame periods are shown as in the first embodiment.

[0094] One ranging frame period includes a first mode period MD_1 and a second mode period MD_2. In each of the first mode period MD_1 and the second mode period MD_2, subframe periods and output periods of the light reception count value are alternately repeated. The output period POUT1_1 in the first mode period MD_1 is a period in which the light reception count value of the subframe period SF1_1 is output to the outside. The output period POUT1_2 is a period in which the light reception count value of the subframe period SF1_2 is output to the outside. The output period POUT1_p is a period in which the light reception count value of the subframe period SF1_p is output to the outside. In this way, the output unit 137 sequentially outputs the light reception count values ​​obtained in all the subframe periods to the outside. The same is true in the second mode period, and for example, the output period POUT2_1 in the second mode period MD_2 is a period in which the light reception count value of the subframe period SF2_1 is output to the outside.

[0095] As described above, in this embodiment, although the frequency distribution holding unit 133 and the peak detection unit 134 are arranged in the distance measurement processing device 1b outside the photoelectric conversion device 1a, distance measurement can be performed similarly to the distance measurement device 1 of the first embodiment. Therefore, according to this embodiment, a photoelectric conversion device 1a capable of shortening the measurement time is provided.

[0096] It is also possible to provide two count value holding units 136. In this case, the operation during the subframe period and the operation during the output period of the light reception count value can be performed in parallel, thereby further shortening the measurement time.

[0097] [Third embodiment] In the first embodiment, the duration of the exposure period of the second mode period MD_2 is set equal to the duration of the exposure period of the first mode period MD_1. In contrast, in the present embodiment, an operation in a case where the duration of the exposure period of the second mode period MD_2 is set shorter than the duration of the exposure period of the first mode period MD_1 will be described. In the present embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0098] 15(a) and 15(b) are timing charts showing the relationship between the subframe periods in the first mode period MD_1 and the subframe periods in the second mode period MD_2 according to this embodiment. FIG. 15(a) shows the subframe periods in the first mode period MD_1, and the period corresponding to the ranging range is divided into 10 periods as in the first embodiment. FIG. 15(b) shows the subframe periods in the second mode period MD_2, and the period corresponding to the ranging range is divided into 20 periods. Therefore, in this embodiment, the duration of the exposure period in the second mode period MD_2 is half the duration of the exposure period in the first mode period MD_1.

[0099] 16(a) to 16(d) are timing charts showing the relationship between the light emission timing of the light-emitting unit 120 in the second mode period MD_2 according to this embodiment and the exposure period of the light-receiving unit 140. Note that, since the operation in the first mode period MD_1 in this embodiment is similar to that in the first embodiment, a description of the first mode period MD_1 will be omitted.

[0100] 16(a) shows a schematic diagram of light emission periods L2_11 and L2_12 and exposure periods E2_11 and E2_12 in the first subframe period SF2_1. The exposure period E2_11 is a period during which reflected light emitted during the light emission period L2_11 and having a flight time of "1" can be received. The exposure period E2_12 is a period during which reflected light emitted during the light emission period L2_12 and having a flight time of "1" can be received.

[0101] FIG. 16(b) shows the light emission periods L2_21 and L2_22 and the exposure periods E2_21 and E2_22 in the second subframe period SF2_2. The exposure period E2_21 is a period during which the reflected light emitted in the light emission period L2_21 and having a flight time of "2" can be received. The exposure period E2_22 is a period during which the reflected light emitted in the light emission period L2_22 and having a flight time of "2" can be received. FIG. 16(a) and FIG. 16(b) show two subframe periods in the second mode period MD_2 corresponding to a distance of "1" in the exposure period of the first mode period MD_1. That is, one exposure period E1_11 in the first mode period MD_1 corresponds to two exposure periods E2_11 and E2_21 in the second mode period MD_2.

[0102] 16(c) shows a schematic diagram of the light emission periods L2_31 and L2_32 and the exposure periods E2_31 and E2_32 in the third subframe period SF2_3. The exposure period E2_31 is a period during which the reflected light emitted during the light emission period L2_31 and having a flight time of "11" can be received. The exposure period E2_32 is a period during which the reflected light emitted during the light emission period L2_32 and having a flight time of "11" can be received.

[0103] FIG. 16(d) shows the light emission periods L2_41 and L2_42 and the exposure periods E2_41 and E2_42 in the fourth subframe period SF2_4. The exposure period E2_41 is a period during which the reflected light emitted in the light emission period L2_41 and having a flight time of "12" can be received. The exposure period E2_42 is a period during which the reflected light emitted in the light emission period L2_42 and having a flight time of "12" can be received. FIG. 16(c) and FIG. 16(d) show two subframe periods in the second mode period MD_2 corresponding to a distance of "6" in the exposure period of the first mode period MD_1. That is, one exposure period E1_12 in the first mode period MD_1 corresponds to two exposure periods E2_31 and E2_41 in the second mode period MD_2.

[0104] 17 is a schematic diagram showing a frequency distribution acquired in the second mode period MD_2 by the distance measuring method according to the present embodiment. In the example shown in FIG. 17, the light receiving count value in the exposure period in which the flight time is "12" is the maximum, so the distance from the distance measuring device 1 to the object X is the distance corresponding to the flight time "12".

[0105] As described above, in this embodiment, measurements are performed in four subframe periods SF2_1 to SF2_4. The duration of the exposure period corresponding to the subframe periods SF2_1 to SF2_4 is half the duration of the exposure period of the first mode period MD_1. Therefore, the duration of the exposure period in acquiring the frequency distribution for distance measurement can be shortened, and the distance resolution of distance measurement can be improved.

[0106] As described above, in the distance measuring device 1 of this embodiment, the operation in the first mode period MD_1 is similar to that of the first embodiment, but the duration of the exposure period in the second mode period MD_2 is set shorter than the duration of the exposure period in the first mode period MD_1. This not only provides the same effects as the first embodiment, but also improves the distance resolution of distance measurement without increasing the measurement time in the first mode period MD_1.

[0107] The configuration and operation of the distance measuring device 1 of the present embodiment are merely examples and are not limited thereto. For example, the duration of the exposure period of the first mode period MD_1 may be three times the duration of the exposure period of the second mode period MD_2, or may be an integer multiple greater than three, or may not be an integer multiple.

[0108] [Fourth embodiment] In this embodiment, the operation in the case where a plurality of exposure periods are arranged in one microframe period in the first mode period MD_1 will be described with reference to Fig. 18(a) to Fig. 21. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0109] In the following description, a measurement method is exemplified in which a period corresponding to the distance measurement range is divided into 12 periods, and it is determined at which of the 12 periods the object X is present at a distance corresponding to the period. However, this method is merely an example in this embodiment, and the present invention is not limited to this.

[0110] 18(a) to 18(c) are timing charts showing the relationship between the light emission timing of the light-emitting unit 120 and the exposure period of the light-receiving unit 140 in the first mode period MD_1 in this embodiment. FIG. 18(a) is a timing chart of the first sub-frame period SF1_1 in the first mode period MD_1. FIG. 18(a) shows the light emission periods L1_11, L1_12, and L1_13 and the exposure periods E1_11, E1_12, E1_13, E1_14, E1_15, and E1_16 in the first sub-frame period SF1_1. FIG. 18(a) also shows a numerical value proportional to the flight time of light from light emission to light reception in the light emission periods L1_11 and L1_13 as the "first flight time." Also, in FIG. 18(a), a value proportional to the flight time of light from light emission to light reception in the light emission period L1_12 is shown as a "second flight time". In this embodiment, two exposure periods are arranged in one microframe period. For example, the exposure period E1_13 is a period in which reflected light emitted in the light emission period L1_12 and having a flight time of "1" and reflected light emitted in the light emission period L1_11 and having a flight time of "7" can be received. Also, the exposure period E1_14 is a period in which reflected light emitted in the light emission period L1_12 and having a flight time of "4" and reflected light emitted in the light emission period L1_11 and having a flight time of "10" can be received.

[0111] FIG. 18(b) is a timing chart of the second sub-frame period SF1_2 in the first mode period MD_1. As in the first embodiment, all exposure periods are changed to positions shifted by one exposure period with respect to the sub-frame period SF1_1. FIG. 18(c) is a timing chart of the third sub-frame period SF1_3 in the first mode period MD_1. Similarly, all exposure periods are changed to positions shifted by one exposure period with respect to the second sub-frame period SF1_2. The second sub-frame period SF1_2 and the third sub-frame period SF1_3 are similar except that the exposure periods are shifted, so their explanations are omitted.

[0112] FIG. 19 is a schematic diagram showing a frequency distribution acquired in the first mode period MD_1 by the distance measurement method according to the present embodiment. The horizontal axis of FIG. 19 is the value of the flight time corresponding to the position of the above-mentioned exposure period. As described above, the flight times "1", "4", "7", "10", flight times "2", "5", "8", "11", and flight times "3", "6", "9", and "12" are measured in a mixed state, so multiple values ​​are written on the horizontal axis of FIG. 19. The vertical axis of FIG. 19 is the number of microframes in which light is detected in each exposure period, that is, the light reception count value. FIG. 19 shows an example in which the number of microframes per subframe is 10 in the operation of the above-mentioned first mode period MD_1, so the maximum value of the vertical axis is 10. In the example shown in FIG. 19, the light reception count value is the maximum in the exposure period in which the flight time is "3", "6", "9", or "12", so the distance from the distance measurement device 1 to the object X is the distance corresponding to any one of the flight times "3", "6", "9", and "12".

[0113] Next, the process in the second mode period MD_2 will be described. In this example, in the measurement in the above-mentioned first mode period MD_1, peak information is obtained that the light reception count value is maximum in the exposure period in which the flight time is "3", "6", "9" or "12" as shown in FIG. 10. Therefore, in the second mode period MD_2, measurements are performed in the subframe periods SF2_1, SF2_2, SF2_3, and SF2_4 in which the exposure periods corresponding to the flight times of "3", "6", "9" and "12" are set, respectively. FIG. 20(a) to FIG. 20(d) are timing charts showing the relationship between the light emission timing of the light emitter 120 and the exposure period of the light receiver 140 in the second mode period MD_2.

[0114] 20(a) shows a schematic diagram of the light emission periods L2_11 and L2_12 and the exposure periods E2_11 and E2_12 in the first subframe period SF2_1. The exposure period E2_11 is a period during which reflected light emitted during the light emission period L2_11 and having a flight time of "3" can be received. The exposure period E2_12 is a period during which reflected light emitted during the light emission period L2_12 and having a flight time of "3" can be received.

[0115] 20(b) shows schematic diagrams of light emission periods L2_21 and L2_22 and exposure periods E2_21 and E2_22 in the second subframe period SF2_2. The exposure period E2_21 is a period during which reflected light emitted during the light emission period L2_21 and having a flight time of "6" can be received. The exposure period E2_22 is a period during which reflected light emitted during the light emission period L2_22 and having a flight time of "6" can be received.

[0116] 20(c) shows a schematic diagram of the light emission periods L2_31 and L2_32 and the exposure periods E2_31 and E2_32 in the third subframe period SF2_3. The exposure period E2_31 is a period during which the reflected light emitted during the light emission period L2_31 and having a flight time of "9" can be received. The exposure period E2_32 is a period during which the reflected light emitted during the light emission period L2_32 and having a flight time of "9" can be received.

[0117] 20(d) shows a schematic diagram of the light emission periods L2_41 and L2_42 and the exposure periods E2_41 and E2_42 in the fourth subframe period SF2_4. The exposure period E2_41 is a period during which the reflected light emitted during the light emission period L2_41 and having a flight time of "12" can be received. The exposure period E2_42 is a period during which the reflected light emitted during the light emission period L2_42 and having a flight time of "12" can be received.

[0118] Fig. 21 is a schematic diagram showing a frequency distribution acquired in the second mode period MD_2 acquired by the distance measuring method according to this embodiment. Fig. 21 shows an example in which the number of microframes per subframe is 10 in the operation of the above-mentioned second mode period MD_2, so the maximum value on the vertical axis is 10. In the example shown in Fig. 21, the light receiving count value in the exposure period in which the flight time is "6" is the maximum, so the distance from the distance measuring device 1 to the object X is the distance corresponding to the flight time of "6".

[0119] As described above, in the distance measuring device 1 of this embodiment, a plurality of exposure periods are arranged in one microframe period in the first mode period MD_1. As a result, compared to the example of the first embodiment, the number of subframes in the first mode period MD_1 can be reduced without changing the cycle of the first timing. Although the number of subframes in the second mode period MD_2 increases compared to the example of the first embodiment, the total measurement time in the first mode period MD_1 and the second mode period MD_2 may be shortened depending on the setting. In addition, the method of this embodiment may be used in combination with a method of reducing the number of microframes per subframe in the second mode period MD_2 compared to that in the first mode period MD_1. As a result, the total measurement time can be further reduced.

[0120] [Fifth embodiment] 22(a) and 22(b) are block diagrams of devices related to the vehicle-mounted distance measuring device in this embodiment. The device 80 has a distance measuring unit 803, which is an example of the distance measuring device 1 in the above-mentioned embodiment, and a signal processing device (processing device) that processes a signal from the distance measuring unit 803. The device 80 has a distance measuring unit 803 that measures the distance to an object, and a collision determination unit 804 that determines whether or not there is a possibility of collision based on the measured distance. Here, the distance measuring unit 803 is an example of a distance information acquisition means that acquires distance information to the object. In other words, the distance information is information related to the distance to the object, etc. The collision determination unit 804 may use the distance information to determine the possibility of collision.

[0121] The device 80 is connected to a vehicle information acquisition device 810, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. In addition, the device 80 is connected to a control ECU 820, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 804. In addition, the device 80 is also connected to an alarm device 830 that issues an alarm to the driver based on the judgment result of the collision judgment unit 804. For example, when the judgment result of the collision judgment unit 804 indicates that there is a high possibility of a collision, the control ECU 820 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 830 warns the user by sounding an alarm such as a sound, displaying alarm information on the screen of a car navigation system, etc., and applying vibrations to a seat belt or steering wheel. These devices of the device 80 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0122] In this embodiment, the device 80 measures distances around the vehicle, for example, in front or behind. Fig. 22(b) shows the device when measuring distances in front of the vehicle (distance measurement range 850). A vehicle information acquisition device 810 as a distance measurement control means sends an instruction to the device 80 or distance measurement unit 803 to perform a distance measurement operation. With this configuration, the accuracy of distance measurement can be further improved.

[0123] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from lanes, etc. Furthermore, the device is not limited to vehicles such as automobiles, but can be applied to moving bodies (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied to devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, in addition to moving bodies.

[0124] [Modified embodiment] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, an example in which a part of the configuration of any of the embodiments is added to another embodiment, or an example in which a part of the configuration of any of the embodiments is replaced with a part of the configuration of another embodiment, is also an embodiment of the present invention.

[0125] The disclosure of this specification includes the complement of the concepts described in this specification. In other words, if the specification states, for example, that "A is B" (A=B), the specification is deemed to disclose or suggest that "A is not B" even if the statement that "A is not B" (A≠B) is omitted. This is because when it states that "A is B," it is assumed that the case that "A is not B" is taken into consideration.

[0126] The disclosure of this specification includes the following configurations and methods. (Configuration 1) a timing generation unit that periodically generates a first timing indicating a light emission timing of a light emitting device in a first mode and periodically generates a second timing indicating a light emission timing of the light emitting device in a second mode; a light receiving section that generates a light receiving signal based on incident light that is incident during an exposure period; an exposure period control unit that generates a control signal for controlling a timing of the exposure period; having The length of the cycle of the second timing is longer than the length of the cycle of the first timing, the exposure period control unit generates the control signal indicating a timing of the exposure period having one time width of one period of the first timing divided into a plurality of periods in the first mode; The exposure period control unit determines timing of the exposure period in the second mode based on a frequency distribution in which count values ​​of the light receiving signal are associated with each of the plurality of exposure periods in the first mode. A photoelectric conversion device comprising: (Configuration 2) The duration of the exposure period in the second mode is equal to the duration of the exposure period in the first mode. 2. The photoelectric conversion device according to configuration 1. (Configuration 3) The duration of the exposure period in the second mode is shorter than the duration of the exposure period in the first mode. 2. The photoelectric conversion device according to configuration 1. (Configuration 4) One of the exposure periods in the first mode corresponds to a plurality of the exposure periods in the second mode. 4. The photoelectric conversion device according to configuration 3. (Configuration 5) The number of times the second timing is generated in the exposure period corresponding to one flight time of the light emitted from the light emitting device is less than the number of times the first timing is generated in the exposure period corresponding to one flight time. 5. The photoelectric conversion device according to any one of configurations 1 to 4. (Configuration 6) The length of the cycle of the second timing is an integer multiple of the length of the cycle of the first timing. 6. The photoelectric conversion device according to any one of configurations 1 to 5. (Configuration 7) One cycle of the second timing includes a distance measurement period in which the exposure period is set and a non-distance measurement period in which the exposure period is not set. 7. The photoelectric conversion device according to any one of configurations 1 to 6. (Configuration 8) A plurality of the exposure periods are set corresponding to one cycle of the first timing. 8. The photoelectric conversion device according to any one of configurations 1 to 7. (Configuration 9) One exposure period is set corresponding to one cycle of the second timing. 9. The photoelectric conversion device according to configuration 8. (Configuration 10) The light receiving device further includes a frequency distribution storage unit that stores the frequency distribution by associating the exposure period with the count value of the light receiving signal. 10. The photoelectric conversion device according to any one of configurations 1 to 9. (Configuration 11) The light receiving device further includes a peak detection unit that performs a peak detection process to detect an exposure period corresponding to a peak of the count value of the light receiving signal based on the frequency distribution. 11. The photoelectric conversion device according to configuration 10. (Configuration 12) The peak detection unit performs the peak detection process by detecting an exposure period corresponding to a maximum value among count values ​​of the light reception signal included in the frequency distribution. 12. The photoelectric conversion device according to claim 11, (Configuration 13) The peak detection unit performs the peak detection process by detecting an exposure period corresponding to a count value of the light reception signal included in the frequency distribution that is greater than a predetermined threshold value. 12. The photoelectric conversion device according to claim 11, (Configuration 14) The peak detection unit performs the peak detection process after the generation of the frequency distribution in the first mode is completed and before the generation of the frequency distribution in the second mode is started. 14. The photoelectric conversion device according to any one of configurations 11 to 13. (Configuration 15) The peak detection unit performs the peak detection process after completing generation of the frequency distribution in the second mode. 15. The photoelectric conversion device according to any one of configurations 11 to 14. (Configuration 16) The exposure period control unit determines a timing of the exposure period in the second mode based on a timing of the exposure period corresponding to the peak in the first mode. 16. The photoelectric conversion device according to any one of configurations 11 to 15. (Configuration 17) a count value storage unit that stores a count value of the light receiving signal; and an output unit that outputs the count value to an outside. 10. The photoelectric conversion device according to any one of configurations 1 to 9. (Configuration 18) The exposure period control unit determines a timing of the exposure period in the second mode by externally acquiring information based on the frequency distribution. 18. The photoelectric conversion device according to claim 17, (Configuration 19) The photoelectric conversion device according to any one of configurations 1 to 18, a processing device that processes distance information acquired by the photoelectric conversion device; An apparatus comprising: (Configuration 20) A mobile object, The photoelectric conversion device according to any one of configurations 1 to 18, a moving object control unit that controls the moving object based on distance information acquired by the photoelectric conversion device; A moving object comprising:

[0127] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions.

[0128] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0129] 120 Light emitting part 131 Timing Generation Unit 132 Exposure period control section 140 Light receiving part

Claims

1. a timing generation unit that periodically generates a first timing indicating a light emission timing of a light emitting device in a first mode and periodically generates a second timing indicating a light emission timing of the light emitting device in a second mode; a light receiving section that generates a light receiving signal based on incident light that is incident during an exposure period; an exposure period control unit that generates a control signal for controlling a timing of the exposure period; having The length of the cycle of the second timing is longer than the length of the cycle of the first timing, the exposure period control unit generates the control signal indicating a timing of the exposure period having one time width of one period of the first timing divided into a plurality of periods in the first mode; The exposure period control unit determines timing of the exposure period in the second mode based on a frequency distribution in which count values ​​of the light receiving signal are associated with each of the plurality of exposure periods in the first mode. A photoelectric conversion device comprising:

2. The duration of the exposure period in the second mode is equal to the duration of the exposure period in the first mode.

2. The photoelectric conversion device according to claim 1.

3. The duration of the exposure period in the second mode is shorter than the duration of the exposure period in the first mode.

2. The photoelectric conversion device according to claim 1.

4. One of the exposure periods in the first mode corresponds to a plurality of the exposure periods in the second mode.

4. The photoelectric conversion device according to claim 3.

5. The number of times the second timing is generated in the exposure period corresponding to one flight time of the light emitted from the light emitting device is less than the number of times the first timing is generated in the exposure period corresponding to one flight time.

2. The photoelectric conversion device according to claim 1.

6. The length of the cycle of the second timing is an integer multiple of the length of the cycle of the first timing.

2. The photoelectric conversion device according to claim 1.

7. One cycle of the second timing includes a distance measurement period in which the exposure period is set and a non-distance measurement period in which the exposure period is not set.

2. The photoelectric conversion device according to claim 1.

8. A plurality of the exposure periods are set corresponding to one cycle of the first timing.

2. The photoelectric conversion device according to claim 1.

9. One exposure period is set corresponding to one cycle of the second timing.

9. The photoelectric conversion device according to claim 8.

10. The light receiving device further includes a frequency distribution storage unit that stores the frequency distribution by associating the exposure period with the count value of the light receiving signal.

2. The photoelectric conversion device according to claim 1.

11. The light receiving device further includes a peak detection unit that performs a peak detection process to detect an exposure period corresponding to a peak of the count value of the light receiving signal based on the frequency distribution. The photoelectric conversion device according to claim 10 .

12. The peak detection unit performs the peak detection process by detecting an exposure period corresponding to a maximum value among count values ​​of the light reception signal included in the frequency distribution. The photoelectric conversion device according to claim 11 .

13. The peak detection unit performs the peak detection process by detecting an exposure period corresponding to a count value of the light reception signal included in the frequency distribution that is greater than a predetermined threshold value. The photoelectric conversion device according to claim 11 .

14. The peak detection unit performs the peak detection process after the generation of the frequency distribution in the first mode is completed and before the generation of the frequency distribution in the second mode is started. The photoelectric conversion device according to claim 11 .

15. The peak detection unit performs the peak detection process after the generation of the frequency distribution in the second mode is completed. The photoelectric conversion device according to claim 11 .

16. The exposure period control unit determines a timing of the exposure period in the second mode based on a timing of the exposure period corresponding to the peak in the first mode. The photoelectric conversion device according to claim 11 .

17. a count value storage unit that stores a count value of the light receiving signal; and an output unit that outputs the count value to an outside.

2. The photoelectric conversion device according to claim 1.

18. The exposure period control unit determines a timing of the exposure period in the second mode by externally acquiring information based on the frequency distribution.

18. The photoelectric conversion device according to claim 17.

19. The photoelectric conversion device according to any one of claims 1 to 18, a processing device that processes distance information acquired by the photoelectric conversion device; An apparatus comprising:

20. A mobile object, The photoelectric conversion device according to any one of claims 1 to 18, a moving object control unit that controls the moving object based on distance information acquired by the photoelectric conversion device; A moving object comprising:

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