Photoelectric conversion device and distance measuring device

Abstract

To provide a photoelectric conversion device that can output an appropriate signal according to the frequency of incidence of photons on pixels.SOLUTION: A photoelectric conversion device has: a light receiving unit that generates a light receiving pulse signal according to incidence of light; a time information acquisition unit that, for every periodic light emission performed by a light emitting unit, acquires a first time count value indicating the time elapsed from the light emission performed by the light emitting unit until input of the light receiving pulse signal, and a second time count value indicating a pulse width of the light receiving pulse signal; and a weight determination unit that generates a weight value including a weight according to the second time count value as a signal used for generation of information representing the relationship between each of the first time count values and a light reception frequency.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] A distance measurement method called the time of flight (TOF) method is known as one of distance measurement methods that uses light to measure the distance to an object. The TOF method is a method for measuring the distance to an object based on the time from the emission of light toward the object to the detection of the light reflected by the object. Patent Document 1 describes a distance measurement device that applies the TOF method to a photon detection sensor using a SPAD (Single Photon Avalanche Diode) element to measure the distance to an object. In Patent Document 1, the accuracy of distance measurement is improved by performing a process corresponding to a weight according to the number of reactions of a light receiving element in response to the incidence of a photon on a pixel on a count value of the time from the emission of light from a light source to the timing when a photon is incident on the pixel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-001764 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the technology described in Patent Document 1, depending on the manner in which photons are incident on a pixel, it may not be possible to appropriately reflect the weighting according to the number of reactions of the light receiving element, and thus it may not be possible to improve distance measurement accuracy.

[0005] An object of the present invention is to provide a photoelectric conversion device capable of outputting an appropriate signal according to the frequency of incidence of photons on a pixel, and a distance measuring device using such a photoelectric conversion device and achieving high distance measurement accuracy. [Means for solving the problem]

[0006] According to one disclosure of the present specification, there is provided a photoelectric conversion device having a light receiving unit that generates a light receiving pulse signal in response to incidence of light, a time information acquiring unit that acquires, for each periodic emission by the light emitting unit, a first time count value indicating the elapsed time from emission of the light emitting unit to input of the light receiving pulse signal and a second time count value indicating the pulse width of the light receiving pulse signal, and a weight determining unit that generates a weight value including a weight corresponding to the second time count value as a signal used for generating information indicating the relationship between each of the first time count values ​​and a light receiving frequency.

[0007] According to another disclosure of this specification, there is provided a distance measuring device having a light receiving unit that generates a light receiving pulse signal in response to incidence of light, a time information acquisition unit that acquires, for each periodic emission by the light emitting unit, a first time count value indicating the elapsed time from the emission of light by the light emitting unit to the input of the light receiving pulse signal and a second time count value indicating the pulse width of the light receiving pulse signal, a weight determination unit that generates, for each periodic emission of light by the light emitting unit, a weight value including a weight corresponding to the second time count value, an information generation unit that accumulates, for each periodic emission of light by the light emitting unit, the weight value output from the weight determination unit as a value indicating the light receiving frequency at the first time count value, and generates information indicating the relationship between a plurality of the first time count values ​​and the light receiving frequency, and a distance information acquisition unit that acquires distance information corresponding to the first time count value having the largest accumulated value of the weight values ​​among the plurality of first time count values.

[0008] Furthermore, according to yet another disclosure of the present specification, there is provided an information processing device having: an input unit to which a first time count value indicating an elapsed time from emission of light by a light emitting unit to reception of a received light pulse signal and a second time count value indicating a pulse width of the received light pulse signal are periodically input; a weight determination unit that generates a weight value including a weight according to the second time count value for each input of the first time count value and the second time count value; an information generation unit that accumulates the weight value output from the weight determination unit for each input of the first time count value and the second time count value as a value indicating a light reception frequency corresponding to the first time count value, and generates information indicating a relationship between a plurality of the first time count values ​​and the light reception frequency; and a distance information acquisition unit that acquires distance information corresponding to the first time count value having the largest accumulated value of the weight values ​​among the plurality of the first time count values. Effect of the Invention

[0009] According to the present invention, it is possible to realize a photoelectric conversion device capable of outputting an appropriate signal according to the frequency of incidence of photons on a pixel, and a distance measuring device with high distance measurement accuracy that uses such a photoelectric conversion device. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a schematic configuration of a distance measuring device according to a first embodiment of the present invention. [Diagram 2] 1 is a block diagram showing an example of the configuration of a photoelectric conversion device according to a first embodiment of the present invention. [Diagram 3] 1 is a block diagram showing an example of the configuration of a pixel in a photoelectric conversion device according to a first embodiment of the present invention. [Figure 4] FIG. 2 is a diagram illustrating a basic operation of a pixel in the photoelectric conversion device according to the first embodiment of the present invention. [Diagram 5] 2 is a block diagram showing an example of the configuration of a signal processing unit in the distance measuring device according to the first embodiment of the present invention. FIG. [Figure 6] FIG. 11 is a diagram illustrating an example of histogram information. [Figure 7]FIG. 2 is a timing chart showing the operation of the distance measuring device according to the first embodiment of the present invention. [Figure 8] 5A to 5C are diagrams illustrating an example of processing by a weighting holding unit in the distance measuring device according to the first embodiment of the present invention. [Figure 9] FIG. 11 is a block diagram showing an example of the configuration of a signal processing unit in a distance measuring device according to a second embodiment of the present invention. [Figure 10] FIG. 11 is a timing diagram showing the operation of the distance measuring device according to the second embodiment of the present invention. [Figure 11] FIG. 13 is a diagram illustrating an example of processing by a weighting holding unit in the distance measuring device according to the third embodiment of the present invention. [Figure 12] FIG. 13 is a diagram (part 1) showing an example of processing by a weighting holding unit in the distance measuring device according to the fourth embodiment of the present invention. [Figure 13] FIG. 13 is a diagram (part 2) showing an example of the process of the weighting holding unit in the distance measuring device according to the fourth embodiment of the present invention. [Figure 14] FIG. 13 is a diagram showing a configuration example of a moving body according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] [First embodiment] A distance measuring device and a distance measuring method according to a first embodiment of the present invention will be described with reference to Figs. 1 to 8. Fig. 1 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment. Fig. 2 is a block diagram showing an example of the configuration of a photoelectric conversion device according to this embodiment. Fig. 3 is a block diagram showing an example of the configuration of a pixel in the photoelectric conversion device according to this embodiment. Fig. 4 is a diagram explaining the basic operation of a pixel in the photoelectric conversion device according to this embodiment. Fig. 5 is a block diagram showing an example of the configuration of a signal processing unit in the distance measuring device according to this embodiment. Fig. 6 is a diagram showing an example of histogram information. Fig. 7 is a timing chart showing the operation of the distance measuring device according to this embodiment. Fig. 8 is a diagram showing an example of the processing of a weighting holding unit in the distance measuring device according to this embodiment.

[0012] First, a schematic configuration of the distance measuring device according to this embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the distance measuring device 100 according to this embodiment can be configured with a light emitting unit 10, a light receiving unit 20, a signal processing unit 30, an output unit 40, and a control unit 50. The light emitting unit 10 is connected to the control unit 50. The light receiving unit 20 is connected to the signal processing unit 30 and the control unit 50. The signal processing unit 30 is connected to the light receiving unit 20, the output unit 30, and the control unit 50. The output unit 40 is connected to the signal processing unit 30 and the control unit 50. The control unit 50 is connected to the light emitting unit 10, the light receiving unit 20, the signal processing unit 30, and the output unit 40.

[0013] The light emitting unit 10 has a light emitting element (not shown) and has a role of emitting pulsed light (irradiation light 12) such as laser light emitted from the light emitting element to the measurement target area. As the light emitting element constituting the light emitting unit 10, an element capable of high speed modulation, such as an LED (Light Emitting Diode) or an LD (Laser Diode), can be preferably used. The light emitting element may be a VCSEL (Vertical Cavity Surface Emitting Laser) or a surface light emitting element in which the VCSEL is arranged in an array. The light emitting unit 10 is preferably configured to irradiate the measurement target area with a uniform amount of light, and may further include an optical element, such as a lens, for optically converting the light emitted from the light emitting element and irradiating the measurement target area.

[0014] The light receiving unit 20 has a role of detecting light incident from the measurement target area. The light incident on the light receiving unit 20 may include not only the ambient light in the measurement target area, but also light (reflected light 14) of the irradiated light 12 reflected by an object 210 in the measurement target area. The light receiving unit 20 includes a plurality of light receiving elements arranged two-dimensionally. Each of the light receiving elements converts an incident optical signal into an electrical signal and outputs the signal to the signal processing unit 30. A pulse signal corresponding to the reflected light 14 is superimposed on the electrical signal output from the light receiving element to the signal processing unit 30. For example, a SPAD (Single Photon Avalanche Diode) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used as the light receiving element. The light receiving unit 20 may further include an optical element, such as a lens, for efficiently guiding the reflected light 14 to the light receiving element.

[0015] The control unit 50 generates a light emission control signal for controlling the timing of emitting pulsed light in the light emitting unit 10, and transmits the generated light emission control signal to the light emitting unit 10. The control unit 50 also generates a count control signal synchronized with the light emission control signal, and transmits the generated count control signal to the signal processing unit 30. The control unit 50 also has a role of controlling the overall operation of the distance measuring device 100.

[0016] The signal processing unit 30 has a role of acquiring distance information to the object 210 based on signals received from the light receiving unit 20 and the control unit 50. The specific configuration and operation of the signal processing unit 30 will be described later. The output unit 40 has a role of outputting the distance information received from the signal processing unit 30 to the outside.

[0017] The distance measuring device 100 according to this embodiment is not particularly limited, and may be configured to include, for example, a photoelectric conversion device 200 shown in Fig. 2. The photoelectric conversion device 200 constitutes at least the light receiving unit 20 among the multiple functional blocks of the distance measuring device 100 shown in Fig. 1. In this embodiment, the photoelectric conversion device 200 will be described taking as an example a case in which the photoelectric conversion device 200 includes at least some of the functions of the signal processing unit 30, the output unit 40, and the control unit 50 in addition to the light receiving unit 20. Note that the functions of the signal processing unit 30, the output unit 40, and the control unit 50 may be provided by a device other than the photoelectric conversion device 200 including the light receiving unit 20.

[0018] The photoelectric conversion device 200 may be configured with a pixel section 110, a pixel driving section 140, a time information acquisition section 150, a horizontal scanning circuit section 160, a signal processing circuit section 170, an output circuit section 180, and a control section 190, as shown in FIG. 2, for example. The pixel section 110 is connected to the pixel driving section 140 and the time information acquisition section 150. The pixel driving section 140 is connected to the pixel section 110 and the control section 190. The time information acquisition section 150 is connected to the pixel section 110, the horizontal scanning circuit section 160, the signal processing circuit section 170, and the control section 190. The horizontal scanning circuit section 160 is connected to the control section 190. The signal processing circuit section 170 is connected to the time information acquisition section 150 and the output circuit section 180. The output circuit section 180 is connected to the signal processing circuit section 170. The control unit 190 is connected to the pixel driving unit 140 , the time information acquiring unit 150 and the horizontal scanning circuit unit 160 .

[0019] Of the above-mentioned functional blocks of the distance measuring device 100, the light receiving unit 20 may be composed of a pixel unit 110 of the photoelectric conversion device 200. The signal processing unit 30 may be composed of a time information acquisition unit 150 and a signal processing circuit unit 170 of the photoelectric conversion device 200. The output unit 40 may be composed of an output circuit unit 180. The control unit 50 may be composed of a pixel driving unit 140, a horizontal scanning circuit unit 160, and a control unit 190.

[0020] The pixel unit 110 includes a plurality of pixels 112 arranged in an array having a plurality of rows and a plurality of columns. As described later, each pixel 112 may be composed of a photoelectric conversion unit including a photoelectric conversion element and a pixel signal processing unit that processes a signal output from the photoelectric conversion unit. The number of pixels 112 constituting the pixel unit 110 is not particularly limited. For example, the pixel unit 110 may be composed of a plurality of pixels 112 arranged in an array of several thousand rows and several thousand columns, as in a general digital camera. Alternatively, the pixel unit 110 may be composed of a plurality of pixels 112 arranged in one row or one column. Alternatively, the pixel unit 110 may be composed of one pixel 112.

[0021] In each row of the pixel array of the pixel unit 110, a control line 114 is arranged extending in a first direction (horizontal direction in FIG. 1). The control line 114 is connected to each of the pixels 112 arranged in the first direction, and serves as a signal line common to these pixels 112. The first direction in which the control lines 114 extend may be called the row direction or horizontal direction. Each of the control lines 114 may include a plurality of signal lines for supplying a plurality of types of control signals to the pixels 112. The control line 114 in each row is connected to a pixel driving unit 140.

[0022] Further, in each column of the pixel array of the pixel unit 110, an output line 116 is arranged to extend in a second direction (vertical direction in FIG. 1) intersecting the first direction. The output line 116 is connected to each of the pixels 112 aligned in the second direction, and serves as a common signal line for these pixels 112. The second direction in which the output line 116 extends may be referred to as a column direction or a vertical direction. Each of the output lines 116 may include a plurality of signal lines.

[0023] The control lines 114 of each row are connected to the pixel driving unit 140. The pixel driving unit 140 is a control circuit having a function of receiving a control signal output from the control unit 190, generating a control signal for driving the pixels 112, and supplying the control signal to the pixels 112 via the control line 114. The pixel driving unit 140 may include logic circuits such as a shift register and an address decoder. The pixel driving unit 140 sequentially scans the pixels 112 in the pixel unit 110 row by row, and outputs pixel signals held by each pixel 112 to the time information acquisition unit 150 via the output line 116.

[0024] The output line 116 of each column is connected to a time information acquisition unit 150. The time information acquisition unit 150 includes a plurality of column information acquisition units (not shown) provided corresponding to each column of the pixel array of the pixel unit 110, and has a function of performing a time count operation in response to pixel signals of the pixels 112 of each column output row by row from the pixel unit 110 via the output line 116. The specific configuration and operation of the time information acquisition unit 150 will be described later.

[0025] The horizontal scanning circuit unit 160 is a control unit that receives a control signal output from the control unit 190, generates a control signal for reading out a signal corresponding to the measurement result from the measurement unit of each column of the time information acquisition unit 150, and supplies the control signal to the time information acquisition unit 150. The horizontal scanning circuit unit 160 may use logic circuits such as a shift register and an address decoder. The horizontal scanning circuit unit 160 sequentially scans the column information acquisition units of each column of the time information acquisition unit 150, and sequentially outputs the signals held in each to the signal processing circuit unit 170.

[0026] The signal processing circuit section 170 has a role of performing predetermined signal processing on the signal transmitted from the time information acquisition section 150. The specific configuration and operation of the signal processing circuit section 170 will be described later.

[0027] The output circuit unit 180 has an external interface circuit, and is a circuit unit for outputting the signal output from the signal processing circuit unit 170 to the outside of the photoelectric conversion device 200. The external interface circuit included in the output circuit unit 180 is not particularly limited. For example, a SerDes (SERializer / DESerializer) transmission circuit can be applied to the external interface circuit. The SerDes transmission circuit is, for example, an LVDS (Low Voltage Differential Signaling) circuit or an SLVS (Scalable Low Voltage Signaling) circuit.

[0028] The control unit 190 is a control circuit for generating control signals for controlling the operations and timings of the pixel driving unit 140, the time information acquiring unit 150, and the horizontal scanning circuit unit 160, and for supplying the control signals to each functional block. Note that at least some of the control signals for controlling the operations and timings of the pixel driving unit 140, the time information acquiring unit 150, and the horizontal scanning circuit unit 160 may be supplied from outside the photoelectric conversion device 200. For example, the function of the control unit 190 may be provided in the control unit 50 of the distance measuring device 100.

[0029] Each pixel 112 may be composed of a photoelectric conversion element 122, a quench circuit 124, a waveform shaping circuit 132, and a selection circuit 134, for example, as shown in FIG.

[0030] The photoelectric conversion element 122 may be an avalanche photodiode (hereinafter, referred to as "APD"). The anode of the APD constituting the photoelectric conversion element 122 is connected to a node to which a voltage VL is supplied. The cathode of the APD constituting the photoelectric conversion element 122 is connected to one terminal of the quench circuit 124. The other terminal of the quench circuit 124 is connected to a node to which a voltage VH higher than the voltage VL is supplied. The voltages VL and VH are set so that a reverse bias voltage sufficient for the APD to perform an avalanche multiplication operation is applied. In one example, a negative high voltage is applied as the voltage VL, and a positive voltage approximately equal to the power supply voltage is applied as the voltage VH. For example, the voltage VL is -30V, and the voltage VH is 1V.

[0031] The photoelectric conversion element 122 may be configured by an APD as described above. By supplying the APD with a reverse bias voltage sufficient for avalanche multiplication, the charge generated by the incidence of light on the APD undergoes avalanche multiplication, generating an avalanche current. There are two operation modes when the APD is supplied with a reverse bias voltage: Geiger mode and linear mode. The Geiger mode is an operation mode in which the voltage applied between the anode and the cathode is a reverse bias voltage greater than the breakdown voltage of the APD. The linear mode is an operation mode in which the voltage applied between the anode and the cathode is a reverse bias voltage close to or less than the breakdown voltage of the APD. An APD operated in the Geiger mode is called a Single Photon Avalanche Diode (SPAD). The APD constituting the photoelectric conversion element 122 may be operated in either the linear mode or the Geiger mode.

[0032] The quench circuit 124 has a function of converting a change in avalanche current generated in the photoelectric conversion element 122 into a voltage signal. The quench circuit 124 also functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication, and has a function of reducing the voltage applied to the photoelectric conversion element 122 to suppress avalanche multiplication. The operation of the quench circuit 124 to suppress avalanche multiplication is called a quench operation. The quench circuit 124 also has a function of returning the voltage supplied to the photoelectric conversion element 122 to the voltage VH by flowing a current equivalent to the voltage drop caused by the quench operation. The operation of returning the voltage supplied to the photoelectric conversion element 122 by the quench circuit 124 to the voltage VH is called a recharge operation. The quench circuit 124 can be configured with a resistor element, a MOS transistor, or the like.

[0033] The waveform shaping circuit 132 has an input node connected to a connection node (node ​​A) between the photoelectric conversion element 122 and the quench circuit 124, and an output node. The waveform shaping circuit 132 has a function of converting an analog signal supplied from node A into a pulse signal. The waveform shaping circuit 132 can be configured of a logic circuit including a NOT circuit (inverter circuit), a NOR circuit, a NAND circuit, etc. The output node of the waveform shaping circuit 132 is connected to the selection circuit 134.

[0034] The selection circuit 134 has a function of switching the electrical connection state (connected or disconnected) between the waveform shaping circuit 132 and the output line 116. The selection circuit 134 switches the connection state between the waveform shaping circuit 132 and the output line 116 in response to a control signal supplied from the pixel driving unit 140 via the control line 114. The selection circuit 134 may include a buffer circuit for outputting a signal.

[0035] Next, the basic operation of the pixel 112 in the photoelectric conversion device 200 of this embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram for explaining the basic operation of the photoelectric conversion unit in the photoelectric conversion device according to this embodiment. Fig. 4(a) shows the waveform of a signal at the input node (node ​​A) of the waveform shaping circuit 132, and Fig. 4(b) shows the waveform of a signal at the output node (node ​​B) of the waveform shaping circuit 132. Note that, for simplicity of explanation, it is assumed here that the waveform shaping circuit 132 is configured with an inverter circuit.

[0036] At time t0, a reverse bias voltage with a potential difference equivalent to (VH-VL) is applied to the photoelectric conversion element 122. A reverse bias voltage sufficient to cause avalanche multiplication is applied between the anode and cathode of the APD constituting the photoelectric conversion element 122, but there are no carriers to serve as the seeds of avalanche multiplication when no photons are incident on the photoelectric conversion element 122. Therefore, avalanche multiplication does not occur in the photoelectric conversion element 122, and no current flows through the photoelectric conversion element 122.

[0037] At the next time t1, a photon is incident on the photoelectric conversion element 122. When a photon is incident on the photoelectric conversion element 122, an electron-hole pair is generated by photoelectric conversion, and avalanche multiplication occurs with these carriers as seeds, and an avalanche multiplication current flows through the photoelectric conversion element 122. As a result, the voltage at node A starts to drop. When the amount of voltage drop at node A increases and the avalanche multiplication stops at time t3, the voltage level at node A does not drop any more.

[0038] When the avalanche multiplication in the photoelectric conversion element 122 stops, a current compensating for the voltage drop flows from the node to which the voltage VH is supplied to the node A via the quench circuit 124, and the voltage of the node A gradually increases. After that, at time t5, the node A is stabilized to the original voltage level.

[0039] The waveform shaping circuit 132 binarizes the signal input from node A according to a predetermined judgment threshold Vth and outputs it from node B. Specifically, when the voltage level of node A exceeds the judgment threshold Vth, the waveform shaping circuit 132 outputs a low-level signal from node B, and when the voltage level of node A is equal to or lower than the judgment threshold, the waveform shaping circuit 132 outputs a high-level signal from node B. For example, as shown in FIG. 4(a), it is assumed that the voltage of node A is equal to or lower than the judgment threshold during the period from time t2 to time t4. In this case, as shown in FIG. 4(b), the signal level at node B is low during the period from time t0 to time t2 and the period from time t4 to time t5, and is high during the period from time t2 to time t4.

[0040] In this way, the analog signal input from node A is waveform-shaped into a digital signal by the waveform shaping circuit 132. The pulse signal output from the waveform shaping circuit 132 in response to the incidence of a photon on the photoelectric conversion element 122 is a received light pulse signal.

[0041] Next, a configuration example and basic operation of the signal processing unit 30 in the distance measuring device 100 of this embodiment will be described with reference to Fig. 5 and Fig. 6. As described above, the signal processing unit 30 can be composed of the time information acquisition unit 150 and the signal processing circuit unit 170 of the photoelectric conversion device 200. Fig. 5 focuses on the processing of a pixel signal output from one pixel 112, and shows only the functional blocks involved in the processing of the pixel signal from among the functional blocks constituting the signal processing unit 30.

[0042] The time information acquisition section 150 has a plurality of column information acquisition sections 152 provided corresponding to each column of the pixel array of the pixel section 110. Each of the plurality of column information acquisition sections 152 has time-to-digital conversion sections (TDC) 154, 156. The signal processing circuit section 170 has a weight determination section 172, a histogram information generation section 174, and a distance information acquisition section 176. The TDC 154 is connected to the output line 116 and the TDC 156. The TDC 156 is connected to the output line 116 and the TDC 154. The weight determination section 172 is connected to the TDCs 154, 156 and the histogram information generation section 174. The histogram information generation section 174 is connected to the weight determination section 172 and the distance information acquisition section 176. The distance information acquisition section 176 is connected to the histogram information generation section 174.

[0043] The signal OUT output from the pixel 112 is input to the TDC 154 and TDC 156 of the column information acquisition unit 152 via the output line 116 of the corresponding column. The TDC 154 and TDC 156 each perform time counting during a predetermined period. The time counting can be performed, for example, by a method of counting the number of pulses superimposed on a clock signal. For example, when a clock signal with a 1 nanosecond period is used, an increase in the time count value from 0 to 10 indicates that 10 nanoseconds have passed.

[0044] Specifically, the TDC 154 counts the time from the timing when it receives from the control unit 190 a count control signal synchronized with the light emission control signal transmitted to the light-emitting unit 10 to the timing when it first receives the light-receiving pulse signal to be superimposed on the signal OUT. Then, the TDC 154 outputs a signal Start to the TDC 156 at the timing when it first receives the light-receiving pulse signal, that is, at the timing when it stops the time count operation in response to the light-receiving pulse signal. The TDC 154 also outputs the count value of the clock pulses during the period from the timing when it receives the count control signal to the timing when it receives the light-receiving pulse signal to the weight determination unit 172 as a time count value TC1. The time count value TC1 corresponds to the elapsed time from the light emission of the light-emitting unit 10 to the input of the light-receiving pulse signal.

[0045] The TDC 156 counts the time from when the signal Start is received to when the next falling edge of the received light pulse signal. The TDC 156 outputs the count value of the clock pulses during the period when the received light pulse signal is received as a time count value TC2 to the weight determination unit 172. The time count value TC2 corresponds to the pulse width of the received light pulse signal.

[0046] The weight determination unit 172 outputs, as a signal for each pixel 112, the time count value TC1 received from the TDC 154 and the weight value WV including a weight according to the time count value TC2 received from the TDC 156 to the histogram information generation unit 174.

[0047] The histogram information generating unit 174 generates information by accumulating the weight value WV for each time count value TC1 for each pixel 112 based on the signal from the weight determining unit 172. Since this information represents the relationship between time classes (hereinafter referred to as "bins") and the light reception frequency in each bin, it is referred to as histogram information in this specification, as it is like a histogram representing the relationship between classes and frequencies. The histogram information only needs to be information that associates the time count value TC1 with an accumulated value, and the data structure does not need to be a histogram itself.

[0048] Fig. 6 is a diagram showing an example of histogram information generated by histogram information generating unit 174 as a histogram. In the histogram in Fig. 6, the horizontal axis represents the bin number indicating the class of time count value TC1, and the vertical axis represents the frequency (accumulated value of weight value WV) in each bin. In the histogram information in Fig. 6, the accumulated value peaks at time count value TC1 corresponding to bin 8.

[0049] Distance information acquisition unit 176 calculates distance information to object 210 for each pixel 112, based on time count value TC1 of the bin where the integrated value reaches a peak. Here, distance D [m] to object 210 can be calculated by the following formula (1). In formula (1), t is the time count value (unit: seconds) corresponding to the bin where the integrated value reaches a peak, and c is the speed of light (2.998×108 [m / sec]). D = c × t / 2 [m] … (1)

[0050] For example, when the resolution of the time count value TC1 is set to 0.1 nanoseconds, bin 8 indicates the peak of the integrated value, so that the distance D to the target object 210 can be calculated to be 120 mm from equation (1).

[0051] Next, the operation of the distance measuring device 100 according to this embodiment will be described in more detail with reference to FIGS. The distance measuring device 100 of this embodiment is a dToF (direct Time of Flight) LiDAR (Light Detection And Ranging) system. This calculates the distance to an object by measuring the time from the emission timing of laser light to the reception timing of reflected light. Pulsed light is periodically emitted from the light emitting unit 10, and time information is acquired for each emission of the pulsed light to obtain a frequency distribution for each predetermined time width, thereby making it possible to acquire more accurate distance information to the object.

[0052] 2, the distance measuring device 100 performs a distance measuring operation for each row of the pixel unit 110. By controlling the selection circuits 134 of the pixels 112 in a predetermined row to be in an on state by a control signal from the pixel driving unit 140, it becomes possible for the pixels 112 in that row to output light receiving pulse signals to the time information acquiring unit 150. By sequentially selecting the pixels 112 in each row by the pixel driving unit 140, distance information corresponding to each of the multiple pixels 112 constituting the pixel unit 110 can be acquired.

[0053] The signals OUT output from the pixels 112 of each column are input to the column information acquisition unit 152 of the corresponding column via the output line 116 of the corresponding column. The column information acquisition unit 152 generates and holds time count values ​​TC1, TC2 based on the signals OUT received from the pixels 112 and the light emission control signal received from the control unit 190.

[0054] In response to a control signal from the horizontal scanning circuit section 160, the time information acquisition section 150 transfers the time count values ​​TC1 and TC2 held by the column information acquisition sections 152 for each column to the signal processing circuit section 170 in sequence.

[0055] The weight determination unit 172 of the signal processing circuit unit 170 generates a weight value WV based on the time count values ​​TC1 and TC2 acquired from the time information acquisition unit 150, and outputs the time count value TC1 and the weight value WV to the histogram information generation unit 174. The histogram information generation unit 174 accumulates the weight value WV output from the weight determination unit 172 for each time count value TC1 for each emission of pulsed light, and generates histogram information for each pixel 112.

[0056] Fig. 7 is a timing diagram showing an example of driving the distance measuring device 100 according to this embodiment. Fig. 7 shows the waveform of the pulsed light that is reflected by the object 210 and then enters the light receiving unit 20, the timing of the photon incidence, and the waveforms of the cathode voltage Vc, the signal OUT, the time count value TC1, the signal Start, and the time count value TC2.

[0057] Time t10 is any time between when the pulsed light is emitted from the light-emitting unit 10 and when it is detected as reflected light 14 by the light-receiving unit 20. At time t10, the photoelectric conversion element 122 is in a standby state in which avalanche multiplication is possible, and the cathode voltage Vc is a voltage corresponding to the voltage VH. The signal OUT receives a cathode voltage Vc higher than the judgment threshold Vth and is at a low level. The time count value TC1 indicates a predetermined count value corresponding to the elapsed time from the timing when the pulsed light is emitted from the light-emitting unit 10, that is, the timing when the count control signal is received from the control unit 190. The signal Start is at a low level in response to the low-level signal OUT. The TDC 156 is in a reset state, and the time count value TC2 is 0.

[0058] After time t10, the reflected light 14 is incident on the light receiving section 20, and photons are incident on a certain pixel 112 at the timings of times t11, t13, t14, and t17, for example, as shown in FIG.

[0059] When a photon is incident on the photoelectric conversion element 122 at time t11, electron-hole pairs are generated by photoelectric conversion, and avalanche multiplication occurs with these carriers as seeds, causing an avalanche multiplication current to flow through the photoelectric conversion element 122. This causes a voltage drop, and the cathode voltage Vc begins to drop.

[0060] At the next time t12, when the cathode voltage Vc falls below the determination threshold Vth, the signal level of the signal OUT output from the waveform shaping circuit 132 transitions from low to high. The TDC 154 stops the time counting operation in response to the rising edge of the signal OUT and transitions the signal Start from low to high. The TDC 156 starts the time counting operation in response to the rising edge of the signal Start.

[0061] After time t12, when the voltage drop at the cathode of the APD becomes large and avalanche multiplication in the photoelectric conversion element 122 stops, the voltage level of the cathode voltage Vc does not drop any further. When avalanche multiplication in the photoelectric conversion element 122 stops, a current flows from the node to which the voltage VL is supplied to the cathode of the APD via the photoelectric conversion element 122, and the cathode voltage Vc gradually increases.

[0062] If a photon is again incident on the photoelectric conversion element 122 at time t13 before the cathode voltage Vc reaches the decision threshold Vth, avalanche multiplication occurs in the photoelectric conversion element 122, and the cathode voltage Vc starts to drop again. In such a case, the cathode voltage Vc does not exceed the decision threshold Vth, so the signal level of the signal OUT is maintained at a high level.

[0063] After time t13, when the voltage drop at the cathode of the APD becomes large and avalanche multiplication in the photoelectric conversion element 122 stops, the voltage level of the cathode voltage Vc does not drop any further. When avalanche multiplication in the photoelectric conversion element 122 stops, a current flows from the node to which the voltage VL is supplied to the cathode of the APD via the photoelectric conversion element 122, and the cathode voltage Vc gradually increases.

[0064] If a photon is again incident on the photoelectric conversion element 122 at time t14 before the cathode voltage Vc reaches the decision threshold Vth, avalanche multiplication occurs in the photoelectric conversion element 122, and the cathode voltage Vc starts to drop again. In this case as well, the cathode voltage Vc does not exceed the decision threshold Vth, so the signal level of the signal OUT is maintained at the High level.

[0065] At the next time t15, when the cathode voltage Vc reaches the determination threshold Vth, the signal level of the signal OUT transitions from a high level to a low level. The TDC 156 stops the time counting operation in response to the falling edge of the signal OUT. That is, the TDC 156 performs the time counting operation in the period from time t12 to time t15. The period during which the TDC 156 performs the time counting operation corresponds to the pulse width of the light receiving pulse signal that is first detected after the light emission of the light emitting unit 10, that is, the period during which the signal OUT is continuously at a high level.

[0066] At the next time t16, the cathode voltage Vc is statically settled to the original voltage corresponding to the voltage VH. The photoelectric conversion element 122 enters a standby state in which avalanche multiplication is possible.

[0067] At the next time t17, when a photon is incident on the photoelectric conversion element 122, electron-hole pairs are generated by photoelectric conversion, and avalanche multiplication occurs with these carriers as seeds, causing an avalanche multiplication current to flow through the photoelectric conversion element 122. This avalanche multiplication current flows through the quench circuit 124, causing a voltage drop due to the quench circuit 124, and the cathode voltage Vc begins to drop.

[0068] At the next time t18, when the cathode voltage Vc falls below the determination threshold Vth, the signal level of the signal OUT output from the waveform shaping circuit 132 transitions from the low level to the high level. The TDC 154 stops counting time at time t12, and does not react to the second and subsequent rising edges of the signal OUT, and does not output the signal Start to the TDC 156.

[0069] After time t18, when the voltage drop at the cathode of the APD becomes large and avalanche multiplication stops in the photoelectric conversion element 122, the voltage level of the cathode voltage Vc stops dropping any more. When avalanche multiplication stops in the photoelectric conversion element 122, the cathode voltage Vc gradually increases.

[0070] At subsequent time t19, when the cathode voltage Vc reaches the determination threshold Vth, the signal level of the signal OUT transitions from a high level to a low level.

[0071] At the next time t20, the cathode voltage Vc is statically settled to the original voltage corresponding to the voltage VH. The photoelectric conversion element 122 enters a standby state in which avalanche multiplication is possible. After that, the same operation as from time t16 to time 20 is repeated until, for example, a count control signal corresponding to the next light emission timing of the light-emitting unit 10 is received.

[0072] When an information acquisition period corresponding to one emission of pulsed light has elapsed, the time information acquisition unit 150 sequentially transfers the time count values ​​TC1 and TC2 held by the column information acquisition units 152 for each column to the signal processing circuit unit 170 in response to a control signal from the horizontal scanning circuit unit 160. The time count values ​​TC1 and TC2 transferred to the signal processing circuit unit 170 are input to a weight determination unit 172. Here, it is assumed that the time count value TC1 held by the TDC 154 is 2011, and the time count value TC2 held by the TDC 156 is 27.

[0073] The weight determination unit 172 determines the weight value WV based on the time count value TC2 acquired from the time information acquisition unit 150. The method of determining the weight value WV is not particularly limited, but for example, a lookup table showing the correspondence between the time count value TC2 and the weight value WV can be used. By preparing a lookup table in advance and referring to this lookup table, the weight value WV corresponding to the time count value TC2 can be acquired.

[0074] Fig. 8 is a diagram showing an example of a lookup table that associates the time count value TC2 with the weight value WV. In the lookup table of Fig. 8, when the time count value TC2 is 10 or less, 11 to 15, 16 to 20, or 21 or more, the weight value WV is set to 1, 2, 4, or 8, respectively. In the case of the operation example of Fig. 7, the time count value TC2 is 27, and the weight value WV is 8.

[0075] A large time count value TC2 indicates that photons are continuously incident within a short period of time after the time corresponding to the time count value TC1, and it is considered that there is a high probability that a clear object exists near the distance corresponding to the time count value TC1. Therefore, in the lookup table of Fig. 8, the weight value WV is set to a larger value as the time count value TC2 is larger, so that the integrated value in the time width where there is a high probability that an object exists is preferentially increased.

[0076] The weighting according to the time count value TC2 is not limited to the example in Fig. 8, and can be changed as appropriate according to the measurement conditions, measurement environment, etc. For example, in the example in Fig. 8, the weight value WV is set to a value of a power of 2, but the weight value WV does not necessarily have to be a value of a power of 2, and may be set to increase at equal intervals, for example. Also, the range of the time count value TC2 corresponding to each value of the weight value WV can be set arbitrarily.

[0077] The weight determination unit 172 transfers the time count value TC1 acquired from the time information acquisition unit 150 and the weight value WV acquired based on the time count value TC2 to the histogram information generation unit 174. The histogram information generation unit 174 accumulates the weight value WV acquired from the weight determination unit 172 for each time count value TC1 for each emission of pulsed light, and generates histogram information for each pixel 112. In the case of the operation example of FIG. 7, the weight value WV of 8 acquired from the weight determination unit 172 is added to the accumulated value up to that point in the time count value TC1.

[0078] By generating histogram information in this manner, it is possible to increase the difference between the integrated value at the time count value TC1 where there is a high probability that an object exists and the integrated value at other time count values ​​TC1 where there is a risk of an object being present, resulting in more accurate distance information.

[0079] It is also possible to count the number of photon detection pulses superimposed on the signal OUT and assign a weighting value WV according to the count value of the received light pulse signal. However, when assigning a weighting value WV according to the count value of the photon detection pulse, if multiple photons are continuously incident within a short period of time, the APD may not be able to recharge in time, and the photon detection pulses may not be counted accurately. For example, in the operation example of Figure 7, the count value corresponding to the incident photons at times t11, t13, and t14 is 1, and appropriate weighting corresponding to the three incident photons cannot be performed.

[0080] In contrast, in this embodiment, the weight value WV is weighted according to the time width of the photon detection pulse superimposed on the signal OUT, so that it is possible to appropriately take into account the increase in the time width of the photon detection pulse in response to the incidence of photons at times t11, t13, and t14. As a result, even when the pulse width of the pulsed light emitted from the light emitter 10 is short and multiple photons are consecutively incident on the light receiver 20 within a short period of time, it is possible to appropriately weight the weight value WV and obtain more accurate distance information.

[0081] In addition, the generation rate (dark count rate) of noise signals (dark pulses) detected when there is no incident light is sufficiently low compared with the incidence rate of photons incident on the light receiving unit 20 due to the pulsed light emitted from the light emitting unit 10. Therefore, the probability that unnecessary weighting is applied to the dark pulses is low, and deterioration of distance measurement accuracy due to the dark pulses is suppressed.

[0082] Thus, according to this embodiment, it is possible to realize a photoelectric conversion device that can output an appropriate signal according to the frequency of incident photons on a pixel, as well as a distance measuring device with high distance measurement accuracy that uses such a photoelectric conversion device.

[0083] [Second embodiment] A distance measuring device and a distance measuring method according to a second embodiment of the present invention will be described with reference to Figs. 9 and 10. Components similar to those in the distance measuring device according to the first embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 9 is a block diagram showing an example of the configuration of a signal processing unit in the distance measuring device according to this embodiment. Fig. 10 is a timing chart showing the operation of the distance measuring device according to this embodiment.

[0084] The distance measuring device according to this embodiment is similar to the distance measuring device 100 according to the first embodiment, except for the configuration of the signal processing unit 30. In this embodiment, the differences from the distance measuring device according to the first embodiment will be mainly described, and the description of the similarities between the distance measuring device according to the first embodiment will be omitted as appropriate.

[0085] As described above, the signal processing unit 30 may be configured by the time information acquisition unit 150 and the signal processing circuit unit 170 of the photoelectric conversion device 200. The signal processing unit 30 of this embodiment differs from the first embodiment in the configuration of the column information acquisition unit 152. That is, as shown in FIG. 9, the column information acquisition unit 152 of this embodiment further includes a counter 158 in addition to the TDC 154 and the TDC 156. The TDC 154 is connected to the output line 116 and the weight determination unit 172. The TDC 156 is connected to the output line 116, the counter 158, and the weight determination unit 172. The counter 158 is connected to the output line 116 and the TDC 156. The configurations and operations of the weight determination unit 172, the histogram information generation unit 174, and the distance information acquisition unit 176 are the same as those of the first embodiment.

[0086] The signal OUT output from the pixel 112 is input to the TDC 154, TDC 156, and counter 158 of the column information acquisition unit 152 via the output line 116 of the corresponding column. The TDC 154, TDC 156, and counter 158 each perform time counting during a predetermined period. The time counting can be performed, for example, by a method of counting the number of pulses superimposed on a clock signal.

[0087] Specifically, the TDC 154 counts the time from the timing when it receives from the control unit 190 a count control signal synchronized with the light emission control signal transmitted to the light emission unit 10 to the timing when it receives the light reception pulse signal superimposed on the signal OUT. The TDC 154 also outputs the count value of the clock pulses during the period from the timing when it receives the count control signal to the timing when it receives the light reception pulse signal to the weight determination unit 172 as a time count value TC1.

[0088] The counter 158 starts a time counting operation from the timing when the light receiving pulse signal superimposed on the signal OUT is first received after the light emission of the light-emitting unit 10, and ends the time counting operation when the time count value reaches a preset value (the value of the signal Stop). The counter 158 then outputs an enable signal Enable, which becomes a predetermined signal level (high level here) during the period when the time counting operation is being performed, to the TDC 156. The value of the signal Stop can be set according to, for example, the pulse width of the pulsed light emitted from the light-emitting unit 10.

[0089] The TDC 156 performs a time count operation during a period in which the enable signal Enable received from the counter 158 is at a predetermined signal level (high level) and in which a light-receiving pulse signal is being received from the pixel 112. The TDC 156 outputs the count value of the clock pulses during a period in which the enable signal Enable is at a predetermined signal level (high level) and in which a light-receiving pulse signal is being received to the weight determination unit 172 as a time count value TC2.

[0090] Fig. 10 is a timing diagram showing an example of driving the distance measuring device according to this embodiment. Fig. 10 shows the waveform of the pulsed light reflected by the object 210 and then incident on the light receiving unit 20, the timing of the incident photons, and the waveforms of the cathode voltage Vc, the signal OUT, the time count values ​​TC1 and TC3, the enable signal Enable, and the time count value TC2. The time count value TC3 is the count value of the counter 158.

[0091] Time t30 is any time between when the pulsed light is emitted from the light-emitting unit 10 and when the reflected light 14 is detected by the light-receiving unit 20. At time t30, the photoelectric conversion element 122 is in a standby state in which avalanche multiplication is possible, and the cathode voltage Vc is a voltage corresponding to the voltage VH. The signal OUT receives a cathode voltage Vc higher than the judgment threshold Vth and is at a low level. The time count value TC1 indicates a predetermined count value corresponding to the elapsed time from the timing when the pulsed light is emitted from the light-emitting unit 10, that is, the timing when the count control signal is received from the control unit 190. The TDC 156 and the counter 158 are in a reset state, and the time count values ​​TC2 and TC3 are 0. It is assumed that the value of the signal Stop preset in the counter 158 is 31. The enable signal Enable receives the low-level signal OUT and is at a low level.

[0092] After time t30, the reflected light 14 is incident on the light receiving section 20, and photons are incident on a certain pixel 112 at the timings of t31, t33, t35, and t40, for example, as shown in FIG.

[0093] At time t31, when a photon is incident on the photoelectric conversion element 122, electron-hole pairs are generated by photoelectric conversion, and avalanche multiplication occurs with these carriers as seeds, and an avalanche multiplication current flows through the photoelectric conversion element 122. This causes a voltage drop, and the cathode voltage Vc begins to drop.

[0094] At the next time t32, when the cathode voltage Vc falls below the determination threshold Vth, the signal level of the signal OUT output from the waveform shaping circuit 132 transitions from low to high. The TDC 154 stops the time counting operation in response to the rising edge of the signal OUT. The counter 158 starts the time counting operation in response to the first rising edge of the signal OUT, and controls the enable signal Enable to change from low to high. The TDC 156 starts the time counting operation in response to the rising edge of the signal OUT and the high level of the enable signal Enable.

[0095] After time t32, when the voltage drop at the cathode of the APD becomes large and avalanche multiplication stops in the photoelectric conversion element 122, the voltage level of the cathode voltage Vc stops dropping any more. When avalanche multiplication stops in the photoelectric conversion element 122, the cathode voltage Vc gradually increases.

[0096] If a photon is again incident on the photoelectric conversion element 122 at time t33 before the cathode voltage Vc reaches the decision threshold Vth, avalanche multiplication occurs in the photoelectric conversion element 122, and the cathode voltage Vc starts to drop again. In such a case, the cathode voltage Vc does not exceed the decision threshold Vth, so the signal level of the signal OUT is maintained at a high level.

[0097] After time t33, when the voltage drop at the cathode of the APD becomes large and avalanche multiplication stops in the photoelectric conversion element 122, the voltage level of the cathode voltage Vc stops dropping any more. When avalanche multiplication stops in the photoelectric conversion element 122, the cathode voltage Vc gradually increases.

[0098] At the next time t34, when the cathode voltage Vc reaches the determination threshold Vth, the signal level of the signal OUT transitions from High to Low. The TDC 156 stops counting time in response to the falling edge of the signal OUT. At this time, the time count value TC2 of the TDC 156 is 18.

[0099] At the next time t35, when a photon is incident on the photoelectric conversion element 122, electron-hole pairs are generated by photoelectric conversion, and avalanche multiplication occurs with these carriers as seeds, causing an avalanche multiplication current to flow through the photoelectric conversion element 122. As a result, the cathode voltage Vc begins to drop.

[0100] At the next time t36, when the cathode voltage Vc falls below the determination threshold Vth, the signal level of the signal OUT output from the waveform shaping circuit 132 transitions from low to high. The TDC 154 stops the time counting operation at time t32 and does not react to the second or subsequent rising edge of the signal OUT. The TDC 156 receives the rising edge of the signal OUT and the high-level enable signal Enable, and resumes the time counting operation from the count value 18.

[0101] After time t36, when the voltage drop at the cathode of the APD becomes large and avalanche multiplication stops in the photoelectric conversion element 122, the voltage level of the cathode voltage Vc stops dropping any more. When avalanche multiplication stops in the photoelectric conversion element 122, the cathode voltage Vc gradually increases.

[0102] At the next time t37, when the cathode voltage Vc reaches the determination threshold Vth, the signal level of the signal OUT transitions from a high level to a low level. The TDC 156 stops the time counting operation in response to the falling edge of the signal OUT. At this time, the time count value TC2 of the TDC 156 is assumed to be 26. Note that the time count value TC2 at this time is the cumulative total of the count value corresponding to the pulse width of the received light pulse signal that rises during the period from time t32 to time t34 and the count value corresponding to the pulse width of the received light pulse signal that rises during the period from time t36 to time t37.

[0103] At the next time t38, the cathode voltage Vc is statically settled to the original voltage corresponding to the voltage VH. The photoelectric conversion element 122 enters a standby state in which avalanche multiplication is possible.

[0104] At subsequent time t39, it is assumed that the time count value TC3 of the counter 158 reaches the preset value of the signal Stop, in which case the counter 158 stops the time counting operation and controls the enable signal Enable to change from High level to Low level.

[0105] At the next time t40, when a photon is incident on the photoelectric conversion element 122, electron-hole pairs are generated by photoelectric conversion, and avalanche multiplication occurs with these carriers as seeds, causing an avalanche multiplication current to flow through the photoelectric conversion element 122. As a result, the cathode voltage Vc begins to drop.

[0106] At the next time t41, when the cathode voltage Vc falls below the determination threshold Vth, the signal level of the signal OUT output from the waveform shaping circuit 132 transitions from low to high. The TDC 154 stops the time counting operation at time t32 and does not react to the second and subsequent rising edges of the signal OUT. The TDC 156 receives the low-level enable signal Enable and does not resume the time counting operation.

[0107] After time t41, when the voltage drop at the cathode of the APD becomes large and avalanche multiplication stops in the photoelectric conversion element 122, the voltage level of the cathode voltage Vc stops dropping any more. When avalanche multiplication stops in the photoelectric conversion element 122, the cathode voltage Vc gradually increases.

[0108] At the next time t42, when the cathode voltage Vc reaches the determination threshold Vth, the signal level of the signal OUT transitions from the high level to the low level.

[0109] At the next time t43, the cathode voltage Vc is statically settled to the original voltage corresponding to the voltage VH. The photoelectric conversion element 122 is in a standby state in which avalanche multiplication is possible. After that, the same operation as from time t40 to time t43 is repeated until, for example, a count control signal corresponding to the next light emission timing of the light-emitting unit 10 is received.

[0110] When an information acquisition period corresponding to one emission of pulsed light has elapsed, the time information acquisition unit 150 sequentially transfers the time count values ​​TC1 and TC2 held by the column information acquisition units 152 for each column to the signal processing circuit unit 170 in response to a control signal from the horizontal scanning circuit unit 160. The time count values ​​TC1 and TC2 transferred to the signal processing circuit unit 170 are input to a weight determination unit 172. Here, it is assumed that the time count value TC1 held by the TDC 154 is 2011, and the time count value TC2 held by the TDC 156 is 26.

[0111] The weight determination unit 172 determines the weight value WV based on the time count value TC2 acquired from the time information acquisition unit 150, for example, in the same manner as in the first embodiment. In the case of the operation example of Fig. 10, the time count value TC2 is 26, and according to the lookup table of Fig. 8, for example, the weight value WV is 8.

[0112] The weight determination unit 172 transfers the time count value TC1 acquired from the time information acquisition unit 150 and the weight value WV acquired based on the time count value TC2 to the histogram information generation unit 174. The histogram information generation unit 174 accumulates the weight value WV acquired from the weight determination unit 172 for each time count value TC1 for each emission of pulsed light, and generates histogram information for each pixel 112. In the case of the operation example of Fig. 10, the weight value WV of 8 acquired from the weight determination unit 172 is added to the accumulated value up to that point in the time count value TC1.

[0113] By generating histogram information in this manner, it is possible to increase the difference between the integrated value at the time count value TC1 where there is a high probability that an object exists and the integrated value at the other time count value TC1 caused by ambient light or noise. Therefore, it is possible to obtain more accurate distance information. In addition, in the first embodiment, the time count is performed only during the first High level period of the OUT signal, but in this embodiment, even if the OUT signal returns to a Low level, the time count can be resumed during the next High level period as long as it is in the enable period. This makes it possible to obtain a time count value TC2 that is more in line with the number of photons incident due to the pulsed light emitted from the light emitting unit 10.

[0114] Thus, according to this embodiment, it is possible to realize a photoelectric conversion device that can output an appropriate signal according to the frequency of incident photons on a pixel, as well as a distance measuring device with high distance measurement accuracy that uses such a photoelectric conversion device.

[0115] In this embodiment, the weight value WV is determined based on the total time count value TC2 during which the enable signal Enable is at a predetermined signal level and the light receiving pulse signal is received, but the weight value WV may be determined for each light receiving pulse signal. For example, the weight value WV may be determined based on the time count value TC2 for each period during which the light receiving pulse signal is received, and the obtained multiple weight values ​​WV may be added together to determine the final weight value WV.

[0116] In addition, a counter may be further provided to count the number of received light pulse signals that are incident during the period when the enable signal Enable is at a predetermined signal level, and the weight value WV may be determined taking into account not only the time count value TC2 but also the count value of the received light pulse signals.

[0117] [Third embodiment] A distance measuring device and a distance measuring method according to a third embodiment of the present invention will be described with reference to Fig. 11. Components similar to those in the distance measuring device according to the first or second embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 11 is a diagram showing an example of processing of a weighting holding unit in the distance measuring device according to this embodiment.

[0118] The distance measuring device according to this embodiment is similar to the distance measuring device according to the first or second embodiment, except for the processing performed by the weight determination unit 172. In this embodiment, the differences from the distance measuring devices according to the first and second embodiments will be mainly described, and the description of the similarities between the distance measuring devices according to the first and second embodiments will be omitted as appropriate.

[0119] In the first and second embodiments, the weighting assigned to the weight value WV increases as the time count value TC2 increases. In contrast, in this embodiment, when the time count value TC2 is equal to or less than a predetermined threshold, the weighting is increased as the time count value TC2 increases, and when the time count value TC2 is greater than the threshold, the weighting is decreased. For example, as shown in the lookup table in FIG. 11, when the time count value TC2 is equal to or less than 10, 11 to 20, 21 to 30, or 31 or more and equal to or less than the width of the pulsed light, or equal to or greater than the width of the pulsed light, the weight value WV is set to 1, 2, 4, 8, or 0, respectively.

[0120] When the pulsed light emitted from the light-emitting unit 10 is received by the light-receiving unit 20, it is considered that there is a high probability that the time count value TC2 measured by the TDC 156 will be equal to or less than the value corresponding to the width of the pulsed light. Therefore, when the time count value TC2 is equal to or less than the value corresponding to the pulse width of the pulsed light emitted from the light-emitting unit 10, the weighting assigned to the weight value WV increases as the time count value TC2 increases.

[0121] On the other hand, if the time count value TC2 measured by the TDC 156 is greater than the value corresponding to the pulse width of the pulsed light, there is a high probability that disturbance light with a strong intensity and long duration has been detected, rather than the pulsed light emitted from the light-emitting unit 10. Therefore, if the time count value TC2 is greater than the value corresponding to the pulse width of the pulsed light emitted from the light-emitting unit 10, the weighting applied to the weight value WV is reduced. Since disturbance light is not something that is originally desired to be counted when generating histogram information, the degree to which disturbance light contributes to the histogram information can be reduced by reducing the weighting.

[0122] From this viewpoint, the threshold value used in the above judgment can be determined, for example, according to the pulse width of the pulsed light emitted from the light-emitting unit 10. In the distance measuring device, the width of the pulsed light emitted from the light-emitting unit 10 is managed, and it is possible to obtain in advance what value the time count value TC2 will be when the pulse width of the pulsed light is measured by the TDC 156.

[0123] When the time count value TC2 is greater than the threshold value, the weight value WV does not necessarily have to be 0, but may be any value smaller than the maximum value of the weight value WV that is set when the time count value TC2 is equal to or smaller than the threshold value.

[0124] Thus, according to this embodiment, it is possible to realize a photoelectric conversion device that can output an appropriate signal according to the frequency of incident photons on a pixel, as well as a distance measuring device with high distance measurement accuracy that uses such a photoelectric conversion device.

[0125] [Fourth embodiment] A distance measuring device and a distance measuring method according to a fourth embodiment of the present invention will be described with reference to Fig. 12 and Fig. 13. The same components as those in the distance measuring devices according to the first to third embodiments are given the same reference numerals, and the description will be omitted or simplified. Fig. 12 and Fig. 13 are diagrams showing an example of the processing of the weighting holding unit in the distance measuring device according to this embodiment.

[0126] The distance measuring device according to this embodiment is similar to the distance measuring devices according to the first to third embodiments, except for the processing performed by the weight determination unit 172. In this embodiment, the differences from the distance measuring devices according to the first to third embodiments will be mainly described, and descriptions of the similarities between the distance measuring devices according to the first to third embodiments will be omitted as appropriate.

[0127] This embodiment is common to the first to third embodiments in that the weighting applied to the weight value WV is changed depending on the time count value TC2, but differs from the first to third embodiments in that the operating conditions of the photoelectric conversion element 122 are further taken into consideration.

[0128] For example, the lower the operating temperature and the higher the recharge voltage of the APD, the more the response speed improves. Therefore, even if photons are incident on the photoelectric conversion element 122 at the same timing, the time count value TC2 may change depending on the operating conditions of the photoelectric conversion element 122. For example, the value of the time count value TC2 when the photoelectric conversion element 122 is at a high temperature is larger than the value of the time count value TC2 when the photoelectric conversion element 122 is at a low temperature. Therefore, in this embodiment, the weight to be assigned to the weight value WV is determined by further considering the operating conditions of the photoelectric conversion element 122 in addition to the time count value TC2.

[0129] The weight determination unit 172 may hold, for example, two types of lookup tables as shown in Fig. 12 and Fig. 13. Fig. 12 is an example of a lookup table that can be applied when the photoelectric conversion element 122 is at a high temperature (for example, 60°C) or when the recharge voltage is low. Fig. 13 is an example of a lookup table that can be applied when the photoelectric conversion element 122 is at a low temperature (for example, 0°C) or when the recharge voltage is high. In the lookup table of Fig. 12, the weight value WV is set to 1, 2, 4, 8, 16, and 32 when the time count value TC2 is 10 or less, 11 to 20, 21 to 25, 26 to 30, 31 to 35, and 36 or more, respectively. In the lookup table of FIG. 13, when the time count value TC2 is 5 or less, 6 to 10, 11 to 13, 14 to 15, 16 to 17, or 18 or more, the weight value WV is set to 1, 2, 4, 8, 16, or 32, respectively.

[0130] By setting the weighting of the weight value WV in this way, it is possible to assign a stable weight to the weight value WV in accordance with the incident timing of a photon, regardless of the operating state of the photoelectric conversion element 122. This makes it possible to reduce the variation in each ranging operation and improve the ranging accuracy.

[0131] Thus, according to this embodiment, it is possible to realize a photoelectric conversion device that can output an appropriate signal according to the frequency of incident photons on a pixel, as well as a distance measuring device with high distance measurement accuracy that uses such a photoelectric conversion device.

[0132] In the present embodiment, two lookup tables are prepared according to the operating conditions of the photoelectric conversion element 122, but three or more lookup tables may be prepared.

[0133] [Fifth embodiment] A moving body according to the fifth embodiment of the present invention will be described with reference to Fig. 14. Fig. 14 is a diagram showing an example of the configuration of a moving body according to this embodiment.

[0134] Fig. 14(a) shows a configuration example of a device mounted on a vehicle as an on-board camera. The device 300 has a distance measurement unit 303 that measures the distance to an object, and a collision determination unit 304 that determines whether or not there is a possibility of collision based on the distance measured by the distance measurement unit 303. The distance measurement unit 303 is configured by the distance measuring device 100 described in any one of the first to fourth embodiments. Here, the distance measurement unit 303 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.

[0135] The device 300 is connected to a vehicle information acquisition device 310 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. In addition, the device 300 is connected to a control ECU 320, 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 304. In addition, the device 300 is also connected to an alarm device 330 that issues an alarm to the driver based on the judgment result of the collision judgment unit 304. For example, when the judgment result of the collision judgment unit 304 indicates that there is a high possibility of a collision, the control ECU 320 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 330 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 300 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0136] In this embodiment, the device 300 measures distances around the vehicle, for example, in front or behind. Fig. 14(b) shows the device when measuring distances in front of the vehicle (distance measurement range 350). A vehicle information acquisition device 310, which serves as a distance measurement control means, sends an instruction to the device 300 or the distance measurement unit 303 to perform a distance measurement operation. This configuration can further improve the accuracy of distance measurement.

[0137] 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.

[0138] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0139] For example, an example in which part of the configuration of any one of the embodiments is added to another embodiment, or an example in which part of the configuration of another embodiment is substituted therefor, is also an embodiment of the present invention.

[0140] In the above first to fourth embodiments, the time information acquisition unit 150 has the column information acquisition unit 152 provided for each column of the pixel unit 110. However, the time information acquisition unit 150 does not necessarily have to have the function corresponding to the column information acquisition unit 152. For example, the functions corresponding to the column information acquisition unit 152, i.e., the TDC 154, the TDC 156, and the counter 158, may be provided in each of the pixels 112 constituting the pixel unit 110. In this case, the time count values ​​TC1 and TC2 are held in each pixel 112 and can be output to the time information acquisition unit 150 on a row-by-row basis in response to a control signal from the pixel driving unit 140. By configuring the pixels 112 in this way, it becomes possible for the multiple pixels 112 constituting the pixel unit 110 to simultaneously acquire distance information for one irradiation of pulsed light, and a distance image with higher temporal accuracy can be acquired. The time information acquisition section 150 may be provided with a plurality of signal holding sections corresponding to the plurality of pixels 112 constituting the pixel section 110 , and configured to transfer the signals of the plurality of pixels 112 to the time information acquisition section 150 all at once.

[0141] In addition, in the above first to fourth embodiments, the light-emitting unit 10 and the light-receiving unit 20 are described as parts of the components of the distance measuring device 100, but at least one of the light-emitting unit 10 and the light-receiving unit 20 does not necessarily have to be part of the configuration of the distance measuring device 100.

[0142] Further, although the distance measuring device has been described in the above first to fourth embodiments, the algorithms described in the above embodiments can also be applied to an information processing device for processing a signal output from the light receiving unit 20. In this case, the information processing device can be configured by an input unit to which a signal is input and a signal processing unit 30. The information processing device can be a device such as a personal computer including a processor (for example, a CPU or MPU). Alternatively, the information processing device can be a circuit such as an ASIC that realizes the functions of the input unit to which a signal is input and the signal processing unit 30.

[0143] 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) that implements one or more of the functions.

[0144] 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.

[0145] The disclosure of the above embodiment includes the following configurations. (Configuration 1) a light receiving unit that generates a light receiving pulse signal in response to incidence of light; a time information acquiring unit that acquires, for each periodic emission by a light emitting unit, a first time count value indicating an elapsed time from emission of light by the light emitting unit to input of the received light pulse signal, and a second time count value indicating a pulse width of the received light pulse signal; a weight determination unit that generates a weight value including a weight corresponding to the second time count value as a signal used for generating information representing a relationship between each of the first time count values ​​and a light receiving frequency; A photoelectric conversion device comprising: (Configuration 2) The information is generated by accumulating the weight value as a value representing the frequency of light reception corresponding to the first time count value every time the light-emitting unit emits light periodically. 2. The photoelectric conversion device according to configuration 1. (Configuration 3) The time information acquisition unit includes a first time-to-digital conversion unit that acquires the first time count value, and a second time-to-digital conversion unit that acquires the second time count value. 3. The photoelectric conversion device according to configuration 1 or 2. (Configuration 4) The time information acquisition unit acquires the first time count value and the second time count value for the light receiving pulse signal that is first input after the light emission of the light emitting unit. 4. The photoelectric conversion device according to any one of configurations 1 to 3. (Configuration 5) The time information acquisition unit accumulates count values ​​corresponding to the pulse widths of the light receiving pulse signals inputted from the first input of the light receiving pulse signal after the light emission of the light emitting unit until a predetermined period has elapsed, and sets the accumulated count value as the second time count value. 5. The photoelectric conversion device according to any one of configurations 1 to 4. (Configuration 6) The time information acquisition unit further includes a counter that counts the time from when the light receiving pulse signal is first input until the predetermined period has elapsed. 6. The photoelectric conversion device according to configuration 5. (Configuration 7) The weight determining unit sets the weight value to a larger value as the second time count value increases. 7. The photoelectric conversion device according to any one of configurations 1 to 6. (Configuration 8) When the second time count value is equal to or smaller than a predetermined threshold value, the weight determination unit sets the weight value to a larger value as the second time count value increases, and when the second time count value is greater than the predetermined threshold value, sets the weight value to a value smaller than the maximum value of the weight value that is set when the second time count value is equal to or smaller than the predetermined threshold value. 7. The photoelectric conversion device according to any one of configurations 1 to 6. (Configuration 9) The light receiving unit has a SPAD, The weight determination unit sets the weight value such that a weight given to the weight value when the operating temperature of the SPAD is a first temperature is greater than a weight given to the weight value when the operating temperature of the SPAD is a second temperature higher than the first temperature. 9. The photoelectric conversion device according to any one of configurations 1 to 8. (Configuration 10) The light receiving unit has a SPAD, The weight determination unit sets the weight value such that a weight given to the weight value when the recharge voltage of the SPAD is a first voltage is greater than a weight given to the weight value when the recharge voltage of the SPAD is a second voltage lower than the first voltage. 9. The photoelectric conversion device according to any one of configurations 1 to 8. (Configuration 11) The weight determination unit has a lookup table indicating a correspondence relationship between the second time count value and the weight value. 11. The photoelectric conversion device according to any one of configurations 1 to 10. (Configuration 12) the light receiving section has a plurality of pixels each having a photoelectric conversion element, The time information acquisition unit and the weight determination unit perform processing on the signal for each pixel. 12. The photoelectric conversion device according to any one of configurations 1 to 11. (Configuration 13) an information generating unit that generates information representing a relationship between a plurality of the first time count values ​​and the frequency of light reception by accumulating the weight value as a value representing the frequency of light reception in the first time count value for each periodic light emission of the light-emitting unit; and a distance information acquisition unit that acquires distance information corresponding to a first time count value having a largest integrated value of the weighting values ​​among the plurality of first time count values. 13. The photoelectric conversion device according to any one of configurations 1 to 12. (Configuration 14) a light receiving unit that generates a light receiving pulse signal in response to incidence of light; a time information acquiring unit that acquires, for each periodic emission by a light emitting unit, a first time count value indicating an elapsed time from emission of the light emitting unit to input of the received light pulse signal, and a second time count value indicating a pulse width of the received light pulse signal; a weight determination unit that generates a weight value including a weight according to the second time count value for each periodic light emission of the light emission unit; an information generating unit that accumulates the weight values ​​output from the weight determining unit as a count value representing a light reception frequency in the first time count value for each periodic light emission of the light emitting unit, and generates information representing a relationship between the first time count values ​​and the light reception frequency; a distance information acquisition unit that acquires distance information corresponding to a first time count value having a largest integrated value of the weighting values ​​among the plurality of first time count values; A distance measuring device comprising: (Configuration 15) A mobile object, A distance measuring device according to configuration 14, a control means for controlling the moving object based on distance information acquired by the distance measuring device; A moving object comprising: (Configuration 16) an input unit to which a first time count value indicating an elapsed time from light emission by a light emitting unit to reception of a received light pulse signal and a second time count value indicating a pulse width of the received light pulse signal are periodically input; a weight determination unit that generates a weight value including a weight according to the second time count value for each input of the first time count value and the second time count value; an information generating unit that accumulates the weight value output from the weight determining unit as a value representing a light receiving frequency corresponding to the first time count value for each input of the first time count value and the second time count value, and generates information representing a relationship between a plurality of the first time count values ​​and the light receiving frequency; a distance information acquisition unit that acquires distance information corresponding to a first time count value having the largest integrated value of the weighting values ​​among the plurality of first time count values; 13. An information processing device comprising: [Explanation of symbols]

[0146] 10…Light emitting part 20...Light receiving section 30...Signal processing unit 100…Distance measuring device 110...Pixel section 150…Time information acquisition unit 152...Column information acquisition section 154,156…TDC 158…Counter 172...Weight determination unit 174...Histogram information generating unit 176…Distance information acquisition unit 200...Photoelectric conversion device

Claims

1. a light receiving unit that generates a light receiving pulse signal in response to incidence of light; a time information acquiring unit that acquires, for each periodic emission by a light emitting unit, a first time count value indicating an elapsed time from emission of light by the light emitting unit to input of the received light pulse signal, and a second time count value indicating a pulse width of the received light pulse signal; a weight determination unit that generates a weight value including a weight corresponding to the second time count value as a signal used for generating information representing a relationship between each of the first time count values ​​and a light receiving frequency; A photoelectric conversion device comprising:

2. The information is generated by accumulating the weight value as a value representing the light reception frequency corresponding to the first time count value for each periodic light emission of the light-emitting unit.

2. The photoelectric conversion device according to claim 1.

3. The time information acquisition unit includes a first time-to-digital conversion unit that acquires the first time count value, and a second time-to-digital conversion unit that acquires the second time count value.

2. The photoelectric conversion device according to claim 1.

4. The time information acquisition unit acquires the first time count value and the second time count value for the light receiving pulse signal that is first input after the light emission of the light emitting unit.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

5. The time information acquiring unit accumulates count values ​​corresponding to the pulse widths of the light receiving pulse signals inputted from the first input of the light receiving pulse signal after the light emission of the light emitting unit until a predetermined period has elapsed, and sets the accumulated count value as the second time count value.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

6. The time information acquisition unit further includes a counter that counts the time from when the light receiving pulse signal is first input until the predetermined period has elapsed.

6. The photoelectric conversion device according to claim 5.

7. The weight determining unit sets the weight value to a larger value as the second time count value increases.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

8. When the second time count value is equal to or smaller than a predetermined threshold value, the weight determination unit sets the weight value to a larger value as the second time count value increases, and when the second time count value is greater than the predetermined threshold value, sets the weight value to a value smaller than the maximum value of the weight value that is set when the second time count value is equal to or smaller than the predetermined threshold value.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

9. The light receiving unit has a SPAD, The weight determination unit sets the weight value such that a weight given to the weight value when the operating temperature of the SPAD is a first temperature is greater than a weight given to the weight value when the operating temperature of the SPAD is a second temperature higher than the first temperature.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

10. The light receiving unit has a SPAD, The weight determination unit sets the weight value such that a weight given to the weight value when a recharge voltage of the SPAD is a first voltage is greater than a weight given to the weight value when a recharge voltage of the SPAD is a second voltage lower than the first voltage.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

11. The weight determination unit has a lookup table indicating a correspondence relationship between the second time count value and the weight value.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

12. the light receiving section has a plurality of pixels each having a photoelectric conversion element, The time information acquisition unit and the weight determination unit perform processing on the signal for each pixel.

4. The photoelectric conversion device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

13. an information generating unit that generates information representing a relationship between a plurality of the first time count values ​​and the frequency of light reception by accumulating the weight value as a value representing the frequency of light reception in the first time count value for each periodic light emission of the light-emitting unit; and a distance information acquisition unit that acquires distance information corresponding to a first time count value having a largest integrated value of the weighting values ​​among the plurality of first time count values.

4. The photoelectric conversion device according to claim 1 or 3.

14. a light receiving unit that generates a light receiving pulse signal in response to incidence of light; a time information acquiring unit that acquires, for each periodic emission by a light emitting unit, a first time count value indicating an elapsed time from emission of light by the light emitting unit to input of the received light pulse signal, and a second time count value indicating a pulse width of the received light pulse signal; a weight determination unit that generates a weight value including a weight according to the second time count value for each periodic light emission of the light emission unit; an information generating unit that accumulates the weight value output from the weight determining unit as a value representing a light reception frequency in the first time count value for each periodic light emission of the light-emitting unit, and generates information representing a relationship between a plurality of the first time count values ​​and the light reception frequency; a distance information acquisition unit that acquires distance information corresponding to a first time count value having a largest integrated value of the weighting values ​​among the plurality of first time count values; A distance measuring device comprising:

15. A mobile object, A distance measuring device according to claim 14, a control means for controlling the moving object based on distance information acquired by the distance measuring device; A moving object comprising:

16. an input unit to which a first time count value indicating an elapsed time from light emission by a light emitting unit to reception of a received light pulse signal and a second time count value indicating a pulse width of the received light pulse signal are periodically input; a weight determination unit that generates a weight value including a weight according to the second time count value for each input of the first time count value and the second time count value; an information generating unit that accumulates the weight value output from the weight determining unit as a value representing a light receiving frequency corresponding to the first time count value for each input of the first time count value and the second time count value, and generates information representing a relationship between a plurality of the first time count values ​​and the light receiving frequency; a distance information acquisition unit that acquires distance information corresponding to a first time count value having a largest integrated value of the weighting values ​​among the plurality of first time count values; 13. An information processing device comprising:

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