Distance measuring device and distance measuring method

Abstract

To provide a distance measuring device capable of improving a frame rate.SOLUTION: A distance measuring device includes a timing generation part for generating first timing that is periodically repeated, and second timing that is timing different from the first timing and is periodically repeated, and supplying the first timing and the second timing as information showing light emission timing to a light-emitting device, a light reception part for generating a signal on the basis of incident light made incident during an exposure period, an exposure period control part for performing control to shift the exposure period with the first timing as reference, and a frequency distribution generation part for generating a frequency distribution showing a relation between time information from light emission of the light-emitting device to light reception by the light reception part and a frequency of light reception by the light reception part on the basis of the signal generated by the light reception part and information showing a shift amount of the exposure period. The length of a shift range of the exposure period is shorter than the length of a period of the first timing.SELECTED DRAWING: Figure 11

Description

[Technical field]

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

[0002] Patent Document 1 discloses a distance measuring device that measures the distance to an object by emitting light from a light source and receiving light, including reflected light from the object, with a light receiving element. Patent Document 1 discloses a method of repeatedly performing measurements while changing a gating period during which photons are detected by the light receiving element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2017 / 0052065 Summary of the Invention [Problem to be solved by the invention]

[0004] In the distance measurement method disclosed in Patent Document 1, it is necessary to repeatedly emit and receive light while changing the gating period, so the time required for one distance measurement may be long. Therefore, in this distance measurement method, it may be difficult to improve the frame rate.

[0005] An object of the present invention is to provide a distance measuring device and a distance measuring method that can improve the frame rate. [Means for solving the problem]

[0006] According to one disclosure of the present specification, there is provided a distance measuring device comprising: a timing generation unit that generates a first timing that is repeated periodically and a second timing that is different from the first timing and that is repeated periodically, and supplies the first timing and the second timing to a light emitting device as information indicating light emission timing; a light receiving unit that generates a signal based on incident light that is incident during an exposure period; an exposure period control unit that controls the shifting of the exposure period based on the first timing; and a frequency distribution generation unit that generates a frequency distribution that indicates the relationship between time information from the emission of light by the light emitting device to the reception of light by the light receiving unit and the frequency of light reception by the light receiving unit based on the signal generated in the light receiving unit and information indicating the amount of shift of the exposure period, wherein the length of the shift range of the exposure period is shorter than the length of the period of the first timing.

[0007] According to one disclosure of the present specification, there is provided a distance measurement method comprising the steps of generating a first timing that is repeated periodically and a second timing that is different from the first timing and that is repeated periodically; supplying the first timing and the second timing to a light emitting device as information indicating light emission timing; generating a signal based on incident light that is incident during the exposure period while shifting an exposure period based on the first timing; and generating a frequency distribution that indicates the relationship between time information from the emission of light by the light emitting device to the reception of the incident light and the frequency of light reception based on the generated signal and information indicating the amount of shift of the exposure period, wherein the length of the shift range of the exposure period is shorter than the length of the period of the first timing. Effect of the Invention

[0008] According to the present invention, a distance measuring device and a distance measuring method capable of improving the frame rate are provided. [Brief description of the drawings]

[0009] [Figure 1] 1 is a hardware block diagram showing an example of a schematic configuration of a distance measuring device according to a first embodiment. [Diagram 2] 1 is a schematic diagram showing the overall configuration of a photoelectric conversion device according to a first embodiment. [Diagram 3] 1 is a schematic block diagram showing an example of the configuration of a sensor substrate according to a first embodiment. [Figure 4] 1 is a schematic block diagram showing an example of the configuration of a circuit board according to a first embodiment. [Diagram 5] 2 is a schematic block diagram showing an example of the configuration of one pixel of a photoelectric conversion unit and a pixel signal processing unit according to the first embodiment. FIG. [Figure 6] 3A to 3C are diagrams illustrating the operation of the avalanche photodiode according to the first embodiment. [Figure 7] 1 is a functional block diagram showing a schematic configuration example of a distance measuring device according to a first embodiment. [Figure 8] 2A to 2C are schematic diagrams for explaining ranging frames, subframes, and microframes according to the first embodiment. [Figure 9] 11 is a timing chart showing a distance measuring method according to a comparative example. [Figure 10] 11 is a histogram showing a frequency distribution obtained by a distance measuring method according to a comparative example. [Figure 11] 4 is a timing chart showing a distance measuring method according to the first embodiment. [Figure 12] 4 is a histogram showing a frequency distribution acquired by the distance measuring method according to the first embodiment. [Figure 13] 4 is a timing chart showing a distance measuring method according to the first embodiment. [Figure 14] 4 is a histogram showing a frequency distribution acquired by the distance measuring method according to the first embodiment. [Figure 15] 4 is a histogram showing a frequency distribution generated by a frequency distribution generating section according to the first embodiment. [Figure 16] 5 is a flowchart showing a frequency distribution generating process in a frequency distribution generating unit according to the first embodiment. [Figure 17] 10 is a timing chart showing a distance measuring method according to the second embodiment. [Figure 18]13 is a timing chart showing a distance measuring method according to the third embodiment. [Figure 19] FIG. 13 is a schematic diagram of a device according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same elements or corresponding elements in multiple drawings are denoted by the same reference numerals, and the description thereof may be omitted or simplified.

[0011] [First embodiment] 1 is a hardware block diagram showing a schematic configuration example of a distance measuring device 1 according to this embodiment. The distance measuring device 1 includes a light emitting device 2, a signal processing circuit 3, and a light receiving device 4. Note that the configuration of the distance measuring device 1 shown in this embodiment is just an example, and is not limited to the configuration shown in the figure.

[0012] The distance measuring device 1 is a device that measures the distance to the object X to be measured using technology such as LiDAR (Light Detection And Ranging). The distance measuring device 1 measures the distance from the distance measuring device 1 to the object X based on the time difference between when light emitted from the light emitting device 2 is reflected by the object X and when it is received by the light receiving device 4. The distance measuring device 1 can also measure the distance to multiple points two-dimensionally by emitting laser light to a predetermined distance measuring range including the object X and receiving the reflected light with a pixel array. This allows the distance measuring device 1 to generate and output a distance image.

[0013] The light received by the light receiving device 4 includes ambient light such as sunlight in addition to the reflected light from the object X. Therefore, the distance measuring device 1 performs distance measurement with reduced influence of ambient light by using a method in which the light incident during each of a plurality of periods (bin periods) is measured to generate a frequency distribution and it is determined that the reflected light is incident during the period when the amount of light is at its peak.

[0014] The light emitting device 2 is a device that emits light such as laser light to the outside of the distance measuring device 1. The signal processing circuit 3 may include a processor that performs arithmetic processing of digital signals, a memory that stores digital signals, etc. The signal processing circuit 3 may be an integrated circuit such as a field-programmable gate array (FPGA) or an image signal processor (ISP).

[0015] The light receiving device 4 generates a pulse signal including a pulse based on the incident light. The light receiving device 4 is, for example, a photoelectric conversion device including an avalanche photodiode as a photoelectric conversion element. In this case, when one photon is incident on the avalanche photodiode and an electric charge is generated, one pulse is generated by avalanche multiplication. However, the light receiving device 4 may be, for example, a device using a photoelectric conversion element using another photodiode.

[0016] In this embodiment, the light receiving device 4 includes a pixel array in which a plurality of photoelectric conversion elements (pixels) are arranged to form a plurality of rows and a plurality of columns. Here, a photoelectric conversion device, which is a specific configuration example of the light receiving device 4, will be described with reference to Figs. 2 to 6. The configuration example of the photoelectric conversion device described below is one example. The photoelectric conversion device applicable to the light receiving device 4 is not limited to this, and may be any device capable of realizing the function of Fig. 7 described later.

[0017] FIG. 2 is a schematic diagram showing the overall configuration of a photoelectric conversion device 100 according to this embodiment. The photoelectric conversion device 100 has a sensor substrate 11 (first substrate) and a circuit substrate 21 (second substrate) that are stacked on each other. The sensor substrate 11 and the circuit substrate 21 are electrically connected to each other. The sensor substrate 11 has a pixel region 12 in which a plurality of pixels 101 are arranged to form a plurality of rows and a plurality of columns. The circuit substrate 21 has a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged to form a plurality of rows and a plurality of columns, and a second circuit region 23 arranged on the periphery of the first circuit region 22. The second circuit region 23 may include a circuit for controlling the plurality of pixel signal processing units 103. The sensor substrate 11 has a light incident surface that receives incident light and a connection surface that faces the light incident surface. The sensor substrate 11 is connected to the circuit substrate 21 on the connection surface side. That is, the photoelectric conversion device 100 is a so-called back-illuminated type.

[0018] In this specification, "planar view" refers to a view from a direction perpendicular to the surface opposite to the light incident surface. Also, a cross section refers to a surface in a direction perpendicular to the surface opposite to the light incident surface of the sensor substrate 11. Note that the light incident surface may be rough when viewed microscopically, and in such a case, the planar view is defined based on the light incident surface when viewed macroscopically.

[0019] In the following description, the sensor substrate 11 and the circuit substrate 21 are described as being diced chips, but the sensor substrate 11 and the circuit substrate 21 are not limited to being chips. For example, the sensor substrate 11 and the circuit substrate 21 may be wafers. In addition, when the sensor substrate 11 and the circuit substrate 21 are diced chips, the photoelectric conversion device 100 may be manufactured by stacking them in a wafer state and then dicing them, or may be manufactured by stacking them after dicing.

[0020] 3 is a schematic block diagram showing an example of the arrangement of the sensor substrate 11. A plurality of pixels 101 arranged in a plurality of rows and a plurality of columns are arranged in the pixel region 12. Each of the plurality of pixels 101 has a photoelectric conversion unit 102 including an avalanche photodiode (hereinafter referred to as APD) as a photoelectric conversion element within the substrate.

[0021] The conductivity type of the charge pair generated in the APD and used as the signal charge is called the first conductivity type. The first conductivity type refers to a conductivity type in which the charge of the same polarity as the signal charge is the majority carrier. The conductivity type opposite to the first conductivity type, that is, the conductivity type in which the charge of the opposite polarity to the signal charge is the majority carrier, is called the second conductivity type. In the APD described below, the anode of the APD is at a fixed potential, and a signal is taken out from the cathode of the APD. Therefore, the semiconductor region of the first conductivity type is an N-type semiconductor region, and the semiconductor region of the second conductivity type is a P-type semiconductor region. The cathode of the APD may be at a fixed potential, and the signal may be taken out from the anode of the APD. In this case, the semiconductor region of the first conductivity type is a P-type semiconductor region, and the semiconductor region of the second conductivity type is an N-type semiconductor region. In the following, a case in which one node of the APD is at a fixed potential will be described, but the potentials of both nodes may be fluctuating.

[0022] 4 is a schematic block diagram showing a configuration example of the circuit board 21. The circuit board 21 has a first circuit area 22 in which a plurality of pixel signal processing units 103 are arranged to form a plurality of rows and a plurality of columns.

[0023] Further, a vertical scanning circuit 110, a horizontal scanning circuit 111, a readout circuit 112, pixel output signal lines 113, an output circuit 114, and a control signal generating unit 115 are arranged on the circuit board 21. The multiple photoelectric conversion units 102 shown in Fig. 3 and the multiple pixel signal processing units 103 shown in Fig. 4 are electrically connected to each other via connection wiring provided for each pixel 101.

[0024] The control signal generating unit 115 is a control circuit that generates control signals for driving the vertical scanning circuit 110, the horizontal scanning circuit 111, and the readout circuit 112, and supplies these circuits with these signals. In this way, the control signal generating unit 115 controls the drive timing of each circuit.

[0025] The vertical scanning circuit 110 supplies a control signal to each of the pixel signal processing units 103 based on the control signal supplied from the control signal generation unit 115. The vertical scanning circuit 110 supplies a control signal to each pixel signal processing unit 103 for each row via a drive line provided for each row of the first circuit area 22. As will be described later, there may be multiple drive lines for each row. The vertical scanning circuit 110 may include logic circuits such as a shift register and an address decoder. In this way, the vertical scanning circuit 110 selects a row for outputting a signal from the pixel signal processing unit 103.

[0026] The signal output from the photoelectric conversion unit 102 of the pixel 101 is processed by the pixel signal processing unit 103. The pixel signal processing unit 103 counts the number of pulses output from the APD included in the photoelectric conversion unit 102 to obtain and hold a digital signal.

[0027] It is not necessary that one pixel signal processing unit 103 is provided for each pixel 101. For example, one pixel signal processing unit 103 may be shared by a plurality of pixels 101. In this case, the pixel signal processing unit 103 provides a signal processing function to each pixel 101 by sequentially processing the signals output from each photoelectric conversion unit 102.

[0028] The horizontal scanning circuit 111 supplies a control signal to the readout circuit 112 based on the control signal supplied from the control signal generation unit 115. The pixel signal processing unit 103 is connected to the readout circuit 112 via a pixel output signal line 113 provided for each column of the first circuit region 22. The pixel output signal line 113 of one column is shared by a plurality of pixel signal processing units 103 of the corresponding column. The pixel output signal line 113 includes a plurality of wirings, and has at least a function of outputting a digital signal from each pixel signal processing unit 103 to the readout circuit 112 and a function of supplying a control signal for selecting a column for outputting a signal to the pixel signal processing unit 103. The readout circuit 112 outputs a signal to a storage unit or a signal processing unit outside the photoelectric conversion device 100 via the output circuit 114 based on the control signal supplied from the control signal generation unit 115.

[0029] The photoelectric conversion units 102 in the pixel region 12 may be arranged one-dimensionally. Moreover, the function of the pixel signal processing unit 103 does not necessarily have to be provided for each pixel 101. For example, one pixel signal processing unit 103 may be shared by a plurality of pixels 101. In this case, the pixel signal processing unit 103 provides a signal processing function to each pixel 101 by sequentially processing signals output from each photoelectric conversion unit 102.

[0030] 3 and 4, a first circuit region 22 in which a plurality of pixel signal processing units 103 are arranged is arranged in a region overlapping the pixel region 12 in a plan view. A vertical scanning circuit 110, a horizontal scanning circuit 111, a readout circuit 112, an output circuit 114, and a control signal generating unit 115 are arranged so as to overlap between an end of the sensor substrate 11 and an end of the pixel region 12 in a plan view. In other words, the sensor substrate 11 has the pixel region 12 and a non-pixel region arranged around the pixel region 12. In the circuit substrate 21, a second circuit region 23 (described above in FIG. 2) in which the vertical scanning circuit 110, the horizontal scanning circuit 111, the readout circuit 112, the output circuit 114, and the control signal generating unit 115 are arranged is arranged in a region overlapping the non-pixel region in a plan view.

[0031] The arrangement of the pixel output signal lines 113, the readout circuits 112, and the output circuits 114 are not limited to those shown in Fig. 4. For example, the pixel output signal lines 113 may be arranged to extend in the row direction and shared by a plurality of pixel signal processing units 103 in the corresponding row. The readout circuits 112 may be arranged so that the pixel output signal lines 113 in each row are connected to each other.

[0032] Fig. 5 is a schematic block diagram showing a configuration example of one pixel of the photoelectric conversion unit 102 and pixel signal processing unit 103 according to this embodiment. Fig. 5 shows a more specific configuration example including a connection relationship between the photoelectric conversion unit 102 arranged on the sensor substrate 11 and the pixel signal processing unit 103 arranged on the circuit substrate 21. Note that in Fig. 5, the drive lines between the vertical scanning circuit 110 and the pixel signal processing unit 103 in Fig. 4 are shown as drive lines 213, 214, and 215.

[0033] The photoelectric conversion unit 102 has an APD 201. The pixel signal processing unit 103 has a quenching element 202, a waveform shaping unit 210, a counter circuit 211, a selection circuit 212, and a gating circuit 216. It is sufficient that the pixel signal processing unit 103 has at least one of the waveform shaping unit 210, the counter circuit 211, the selection circuit 212, and the gating circuit 216.

[0034] The APD 201 generates charges according to incident light by photoelectric conversion. A voltage VL (first voltage) is supplied to the anode of the APD 201. A cathode of the APD 201 is connected to a first terminal of the quench element 202 and an input terminal of the waveform shaping unit 210. A voltage VH (second voltage) higher than the voltage VL supplied to the anode is supplied to the cathode of the APD 201. As a result, a reverse bias voltage is supplied to the anode and cathode of the APD 201 such that the APD 201 performs avalanche multiplication. When charges are generated by incident light in the APD 201 to which the reverse bias voltage is supplied, the charges undergo avalanche multiplication, generating an avalanche current.

[0035] In addition, there are two operation modes when a reverse bias voltage is supplied to the APD 201: Geiger mode and linear mode. The Geiger mode is a mode in which the APD 201 operates with a potential difference between the anode and cathode that is greater than the breakdown voltage, and the linear mode is a mode in which the APD 201 operates with a potential difference between the anode and cathode that is close to or less than the breakdown voltage.

[0036] An APD operated in Geiger mode is called a SPAD (Single Photon Avalanche Diode). In this case, for example, the voltage VL (first voltage) is −30 V, and the voltage VH (second voltage) is 1 V. The APD 201 may be operated in either linear mode or Geiger mode. In the case of a SPAD, the potential difference is larger than that of an APD in linear mode, and the effect of avalanche multiplication is more pronounced, so a SPAD is preferable.

[0037] The quench element 202 functions as a load circuit (quench circuit) during signal multiplication by avalanche multiplication. The quench element 202 suppresses the voltage supplied to the APD 201 to suppress avalanche multiplication (quench operation). The quench element 202 also returns the voltage supplied to the APD 201 to the voltage VH by passing a current corresponding to the voltage drop caused by the quench operation (recharge operation). The quench element 202 can be, for example, a resistive element.

[0038] The waveform shaping unit 210 shapes the potential change of the cathode of the APD 201 obtained when a photon is detected, and outputs a pulse signal. For example, an inverter circuit is used as the waveform shaping unit 210. Although an example in which one inverter is used as the waveform shaping unit 210 is shown in Fig. 5, the waveform shaping unit 210 may be a circuit in which a plurality of inverters are connected in series, or may be another circuit having a waveform shaping effect.

[0039] The gating circuit 216 is a circuit that performs gating such that the pulse signal output from the waveform shaping unit 210 passes only for a predetermined period. During the period during which the pulse signal can pass through the gating circuit 216, photons incident on the APD 201 are counted by the counter circuit 211 at the rear stage. Therefore, the gating circuit 216 controls the exposure period during which a signal is generated based on the incident light in the pixel 101. The period during which the pulse signal passes is controlled by a control signal supplied from the vertical scanning circuit 110 via the drive line 215. FIG. 5 shows an example in which one AND circuit is used as the gating circuit 216. A pulse signal and a control signal are input to two input terminals of the AND circuit. The AND circuit outputs the logical product of these to the counter circuit 211. Note that the gating circuit 216 may have a circuit configuration other than an AND circuit as long as it can realize gating. In addition, the waveform shaping unit 210 and the gating circuit 216 may be integrated by using a logic circuit such as a NAND circuit.

[0040] The counter circuit 211 counts the pulse signals output from the waveform shaping unit 210 via the gating circuit 216, and holds a digital signal indicating the count value. When a control signal is supplied from the vertical scanning circuit 110 via the drive line 213, the counter circuit 211 resets the held signal. The counter circuit 211 can be, for example, a 1-bit counter.

[0041] A control signal is supplied to the selection circuit 212 from the vertical scanning circuit 110 shown in Fig. 4 via a drive line 214 shown in Fig. 5. In response to this control signal, the selection circuit 212 switches between electrical connection and non-connection between the counter circuit 211 and the pixel output signal line 113. The selection circuit 212 includes, for example, a buffer circuit for outputting a signal corresponding to a value held in the counter circuit 211.

[0042] 5, the selection circuit 212 switches between electrical connection and disconnection between the counter circuit 211 and the pixel output signal line 113, but the method of controlling the signal output to the pixel output signal line 113 is not limited to this. For example, a switch such as a transistor may be disposed at a node between the quench element 202 and the APD 201, between the photoelectric conversion unit 102 and the pixel signal processing unit 103, or the like, and the signal output to the pixel output signal line 113 may be controlled by switching between electrical connection and disconnection. Alternatively, the signal output to the pixel output signal line 113 may be controlled by changing the value of the voltage VH or voltage VL supplied to the photoelectric conversion unit 102 using a switch such as a transistor.

[0043] Figures 6(a), 6(b) and 6(c) are diagrams for explaining the operation of the APD 201 according to this embodiment. Figure 6(a) is a diagram showing the APD 201, the quench element 202 and the waveform shaping unit 210 extracted from Figure 5. As shown in Figure 6(a), the connection node of the APD 201, the quench element 202 and the input terminals of the waveform shaping unit 210 is referred to as nodeA. Also, as shown in Figure 6(a), the output side of the waveform shaping unit 210 is referred to as nodeB.

[0044] FIG. 6(b) is a graph showing the time change of the potential of nodeA in FIG. 6(a). FIG. 6(c) is a graph showing the time change of the potential of nodeB in FIG. 6(a). In the period from time t0 to time t1, a voltage of VH-VL is applied to the APD 201 in FIG. 6(a). When a photon is incident on the APD 201 at time t1, avalanche multiplication occurs in the APD 201. As a result, an avalanche current flows through the quench element 202, and the potential of nodeA drops. After that, the amount of potential drop further increases, and the voltage applied to the APD 201 gradually decreases. Then, at time t2, the avalanche multiplication in the APD 201 stops. As a result, the voltage level of nodeA does not drop below a certain value. After that, in the period from time t2 to time t3, a current that compensates for the voltage drop flows from the node of voltage VH to nodeA, and at time t3, nodeA settles to its original potential.

[0045] In the above process, the potential of node B becomes high during the period when the potential of node A is lower than a certain threshold. In this way, the waveform of the drop in the potential of node A caused by the incidence of a photon is shaped by the waveform shaping unit 210 and output as a pulse to node B.

[0046] Next, the overall configuration and operation of the distance measuring device 1 will be described in more detail. Fig. 7 is a functional block diagram showing a schematic configuration example of the distance measuring device 1 according to this embodiment. The distance measuring device 1 has a light emitting unit 120, a light receiving unit 140, a timing generating unit 131, an exposure period control unit 132, a first holding unit 133, a frequency distribution generating unit 134, a second holding unit 135, and an output unit 136.

[0047] The light emitting unit 120 corresponds to the light emitting device 2 in Fig. 1. The light receiving unit 140 corresponds to the light receiving device 4 in Fig. 1 or one pixel 101 in Fig. 4. The timing generating unit 131, the exposure period control unit 132, the first holding unit 133, the frequency distribution generating unit 134, the second holding unit 135, and the output unit 136 correspond to the signal processing circuit 3 in Fig. 1.

[0048] The timing generation unit 131 generates a first timing that is repeated periodically. The period between one first timing and the next first timing is called a microframe period. The timing generation unit 131 also generates a second timing that is different from the first timing and that is repeated periodically. The second timing can be repeated in a period having the same length as the first timing. In other words, one second timing exists within one microframe period.

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

[0050] The exposure period control unit 132 determines the start timing of the exposure period in the light receiving unit 140 based on the first timing. The length of the exposure period can be set appropriately. The length of the exposure period affects the distance measurement resolution in the distance measuring device 1. In other words, if the exposure period is set short, the distance resolution increases, and if the exposure period is set long, the distance resolution decreases.

[0051] Within one microframe period, there is one exposure period. After multiple microframe periods in which exposure is performed at the same start timing are completed, the start timing of exposure is shifted by the length of the exposure period, and multiple microframe periods in which exposure is performed at the shifted start timing are started. In this specification, multiple microframe periods in which exposure is performed at the same start timing are called subframe periods. Therefore, the exposure period control unit 132 controls the exposure period to be shifted every time a subframe period elapses. The amount of shift in this exposure time is time information equivalent to the flight time of light from light emission to light reception, and is proportional to the distance from the distance measuring device 1 to the object X.

[0052] When light is incident during an exposure period, the light receiving unit 140 converts the received light into a pulse of an electrical signal. The light receiving unit 140 may be configured, for example, as the above-mentioned photoelectric conversion device 100. The output signal of the light receiving unit 140 is output to the first holding unit 133. The first holding unit 133 holds the multiple signals input from the light receiving unit 140 as a first frequency distribution indicating the relationship between the shift amount of the exposure period and the frequency of reception of the incident light.

[0053] After a predetermined number of subframe periods have elapsed, the timing generation unit 131 changes the second timing to a timing different from the previous subframe period and supplies it to the light emission unit 120 and the exposure period control unit 132. When the second timing is changed, the exposure period control unit 132 returns the start timing of the exposure period to an initial value and controls the exposure period. Thereafter, the light receiving unit 140 and the exposure period control unit 132 start acquiring signals for the next subframe period in the same manner. After the second timing is changed, the first holding unit 133 holds the multiple signals input from the light receiving unit 140 as a second frequency distribution indicating the relationship between the shift amount of the exposure period and the frequency of reception of the incident light.

[0054] After a further predetermined subframe period has elapsed, the timing generation unit 131 outputs a signal notifying the end of measurement for one frame period to the exposure period control unit 132. The exposure period control unit 132 outputs a signal instructing the frequency distribution generation unit 134 to generate a frequency distribution.

[0055] The frequency distribution generating unit 134 receives a signal instructing generation of a frequency distribution and acquires the first frequency distribution and the second frequency distribution from the first holding unit 133. The frequency distribution generating unit 134 generates a frequency distribution of the entire distance measurement range based on the first frequency distribution and the second frequency distribution, and outputs the frequency distribution to the second holding unit 135. The frequency distribution of the entire distance measurement range is a frequency distribution indicating the relationship between the shift amount of the exposure period corresponding to the entire distance measurement range and the frequency of received incident light. Hereinafter, the frequency distribution of the entire distance measurement range may also be referred to as a third frequency distribution.

[0056] The output unit 136 acquires the third frequency distribution from the second holding unit 135 every time one frame period elapses, and outputs it to the outside of the distance measuring device 1. Alternatively, the output unit 136 may calculate the distance from the distance measuring device 1 to the object X from peak information of the third frequency distribution, and output the distance information to the outside of the distance measuring device 1.

[0057] FIG. 8 is a schematic diagram for explaining a ranging frame, a subframe, and a microframe according to this embodiment. The relationship between the above-mentioned frame, subframe, and microframe will be described in more detail with reference to FIG. 8. In FIG. 8, the acquisition period of a ranging frame corresponding to one ranging result, a subframe used to generate the ranging frame, and a microframe used to generate the subframe are shown by arranging blocks in the horizontal direction. The horizontal direction in FIG. 3 indicates the passage of time, and one block indicates the acquisition period of one ranging frame, subframe, or microframe. In addition, FIG. 8 shows a control signal for controlling the light emission period of the light emitting unit 120 and an exposure control signal for controlling the exposure period in the light receiving unit 140.

[0058] In the "distance measurement period" in Fig. 8, multiple frame periods FL_1, FL_2, ... included in one distance measurement period are shown. Frame period FL_1 indicates the first frame period in one distance measurement period, and frame period FL_2 indicates the second frame period in one distance measurement period. A frame period is a period during which the distance measurement device 1 performs one distance measurement and outputs a signal indicating the distance (distance measurement result) from the distance measurement device 1 to the object X to the outside. Note that Fig. 8 shows an example in which a peak is determined and output from the frequency distribution within the distance measurement device 1, but this is not essential.

[0059] One ranging frame is generated from multiple subframes. In the "frame period" of FIG. 8, multiple subframe periods SF_1, SF_2, ..., SF_p included in one frame period and a peak output period POUT in which a peak is determined from the frequency distribution and output is shown. The subframe period SF_1 indicates the first subframe period in one frame period, and the subframe period SF_2 indicates the second subframe period in one frame period. In this embodiment, the number of subframes per frame is p (p is an integer equal to or greater than 2). The subframe period SF_p indicates the pth subframe period in one frame period.

[0060] One subframe is generated from multiple microframes. In the "subframe period" of FIG. 8, multiple microframe periods MF_1, MF_2, ..., MF_q included in one subframe period are shown. Microframe period MF_1 indicates the first microframe period in one subframe period, and microframe period MF_2 indicates the second microframe period in one subframe period. In this embodiment, the number of microframes per subframe is q (q is an integer equal to or greater than 2). Microframe period MF_q indicates the qth microframe period in one subframe period. The number of microframes q corresponds to the number of times the light reception results are integrated.

[0061] The "light emission" and "exposure control signal" in FIG. 8 indicate the light emission period of the light emission unit 120 and the exposure control signal input to the light receiving unit 140 in one microframe period. The light emission unit 120 emits light during the light emission period LA and the light emission period LB when "light emission" is at a high level. The start time of the light emission period LA corresponds to the first timing described above, and the start time of the light emission period LB corresponds to the second timing described above. In addition, when light is incident on the light receiving unit 140 during the exposure period E when the "exposure control signal" is at a high level, the incident light is detected in the light receiving unit 140. The period T_k from the start of the light emission period LA to the start of the exposure period E corresponds to the flight time of light from light emission to light reception in the light emission period LA. In other words, the length of the period T_k corresponds to the distance measurement distance in the corresponding microframe. Note that k is the number of the corresponding subframe period and is an integer from 1 to p. In addition, although not shown in FIG. 8, the light emitted during the light emission period LB can also be received during the exposure period E. This will be described later in the description of FIG. 11 and the like.

[0062] In each of the multiple microframe periods MF_1, MF_2, ..., MF_q, the length of the period T_k from the start of the light emission period LA to the start of the exposure period E is the same. That is, in one subframe period, light reception data is read out (microframe acquisition) q times. When a photon is detected one or more times in one microframe period, the light receiving unit 140 outputs "1" as the light reception data. Data indicating the number of microframes in which a photon was detected is generated by accumulating the q microframes acquired in one subframe period.

[0063] In each of the multiple subframe periods SF_1, SF_2, ..., SF_p, the lengths of the periods T_1, T_2, ..., T_p are different from each other. As a result, a frequency distribution of received light at different distances is acquired in each of the multiple subframe periods SF_1, SF_2, ..., SF_p. In the peak output period POUT, a peak (maximum value) of the frequency distribution is detected from the frequency of each of the subframe periods SF_1, SF_2, ..., SF_p. The length of the period T_k corresponding to this peak is proportional to the distance from the distance measuring device 1 to the object X.

[0064] Hereinafter, more specific operations of the distance measuring device 1 of this embodiment, such as the above-mentioned second timing, a method for determining the shift range of the exposure period, and a method for generating the third frequency distribution, will be described.

[0065] First, prior to the operation of this embodiment, an operation method of a comparative example will be described with reference to Fig. 9(a), Fig. 9(b) and Fig. 10. This comparative example is an example in which there is no second timing in this embodiment. In other words, this comparative example is an example in which one light emission is performed in one microframe period.

[0066] Figures 9(a) and 9(b) are timing charts showing a distance measuring method according to a comparative example. Each of Figures 9(a) and 9(b) shows the relationship between the light emission timing and the exposure period for a microframe period in one subframe period. One microframe period is divided into 15 periods (exposure periods) numbered "1" to "15", and the exposure period is shifted so that one of these periods becomes the exposure period. Note that this number of divisions is merely an example and is not limited to this.

[0067] In FIG. 9(a), "L11", "L12", and "L13" indicate light emission timings, and "E11", "E12", and "E13" indicate exposure periods. As shown in FIG. 9(a), light emission timings L11, L12, and L13 (first timings) are repeated at regular intervals and correspond to the start time or end time of a microframe period. In the example of FIG. 9(a), exposure periods E11, E12, and E13 are exposure period "1" in the microframe period.

[0068] FIG. 9(b) shows the next subframe of FIG. 9(a). In FIG. 9(b), "L21", "L22", and "L23" indicate light emission timings, and "E21", "E22", and "E23" indicate exposure periods. As shown in FIG. 9(b), light emission timings L21, L22, and L23 are the same as those in FIG. 9(a). In the example of FIG. 9(b), the exposure periods E21, E22, and E23 are exposure period "2" in the microframe period.

[0069] 9(a) and 9(b), the third and subsequent microframe periods are omitted, but the number of microframe periods in one subframe period is, for example, 10. In FIG. 9(a) and 9(b), two subframe periods with exposure periods "1" and "2" are shown, but the exposure period is then shifted from "3" to "15" and the same process is performed to obtain a total of 15 subframes. That is, the number of subframes per frame is 15, and the number of microframes per subframe is 10, so the number of microframes per frame is 150.

[0070] Fig. 10 is a histogram showing a frequency distribution obtained by a distance measuring method according to a comparative example. Fig. 10 shows an example of a frequency distribution showing the relationship between the exposure period and the light receiving frequency, which can be obtained in the above-mentioned example of the number of microframes, in the form of a histogram. Since 10 microframes are measured in one exposure period, the maximum value on the vertical axis of the histogram is 10.

[0071] In the example shown in FIG. 10, when the exposure period is "10", the light reception frequency is maximum. That is, a peak P1 exists at the position of "10". In this case, it is determined that the object X exists at the distance corresponding to "10". In order to obtain this distance measurement result, light emission and reception are required the number of times equal to the number of microframes per frame (150 in the above example). The "first range", "second range", and "third range" shown in FIG. 10 will be described later.

[0072] Next, the operation method of this embodiment will be described with reference to Fig. 11(a) to Fig. 16. In this embodiment, a second timing is added to the above-mentioned comparative example. In other words, in this embodiment, light is emitted twice in one microframe period. In this description, parts common to the above-mentioned comparative example may be omitted.

[0073] Figures 11(a) and 11(b) are timing charts showing the distance measuring method according to this embodiment. Each of Figures 11(a) and 11(b) shows the relationship between two light emission timings and one exposure period for a microframe period in one subframe period. One microframe period is divided into 15 periods, numbered "1" to "15."

[0074] One microframe period is divided into three equal intervals. That is, one microframe period is divided into a first range including "1" to "5", a second range including "6" to "10", and a third range including "11" to "15". That is, the first range, the second range, and the third range do not overlap with each other. Also, the first range, the second range, and the third range are of equal length. In this embodiment, the exposure period is shifted not over the entire microframe period, but only over the first range, i.e., the range from "1" to "5".

[0075] As described above, the second timing can be changed to one of two types of timing. In Figures 11(a) and 11(b), the second timing is the exposure period between "5" and "6", that is, the start position of the second range.

[0076] In FIG. 11(a), "LA11", "LB11", "LA12", "LB12", "LA13", and "LB13" indicate light emission timings, and "E11", "E12", and "E13" indicate exposure periods. As shown in FIG. 11(a), the light emission timings LA11, LA12, and LA13 (first timings) are repeated at regular intervals and correspond to the start time or end time of a microframe period. Furthermore, each of the light emission timings LB11, LB12, and LB13 (second timings) corresponds to the start position of the second range within the corresponding microframe period. Furthermore, in the example of FIG. 11(a), the exposure periods E11, E12, and E13 are exposure period "1" within the microframe period.

[0077] There are two light emission timings LA11 and LB11 in the first microframe period. Similarly, there are two light emission timings LA12 and LB12 in the second microframe period. Here, focusing on the period T1 in FIG. 11(a) which corresponds to the exposure period of the second microframe, this period is the exposure period "1" based on the light emission timing LA12 and also the exposure period "11" based on the light emission timing LB11. In this subframe, a signal is acquired which is the sum of the exposure period "1" based on the light emission timings LA11, LA12, and LA13 (first timing) and the exposure period "11" based on the light emission timings LB11, LB12, and LB13 (second timing).

[0078] FIG. 11(b) shows the next subframe of FIG. 11(a). In FIG. 11(b), "LA21", "LB21", "LA22", "LB22", "LA23", and "LB23" indicate light emission timings, and "E21", "E22", and "E23" indicate exposure periods. As shown in FIG. 11(b), the light emission timings LA21, LA22, and LA23 (first timings) are repeated at a constant cycle and correspond to the start time or end time of a microframe period. Also, each of the light emission timings LB21, LB22, and LB23 (second timings) corresponds to the start position of the second range in the corresponding microframe. Also, in the example of FIG. 11(b), the exposure periods E21, E22, and E23 are exposure period "2" in the microframe period.

[0079] There are two light emission timings LA21 and LB21 in the first microframe period. Similarly, there are two light emission timings LA22 and LB22 in the second microframe period. Here, focusing on the period T2 in FIG. 11(b) which corresponds to the exposure period of the second microframe, this period is the exposure period "2" based on the light emission timing LA22 and also the exposure period "12" based on the light emission timing LB21. In this subframe, a signal is acquired which is the sum of the exposure period "2" based on the light emission timings LA21, LA22, and LA23 (first timing) and the exposure period "12" based on the light emission timings LB21, LB22, and LB23 (second timing).

[0080] 11(a) and 11(b) show two subframe periods with exposure periods "1" and "2", and then the same process is performed while shifting the exposure period from "3" to "5". As a result, a total of five subframes are acquired for generating the first frequency distribution. That is, in acquiring the first frequency distribution, the number of subframes per frame is 5, and the number of microframes per subframe is 10, so the number of microframes per frame is 50.

[0081] Fig. 12 is a histogram showing a first frequency distribution obtained by the distance measuring method according to the present embodiment. Fig. 12 shows, in the form of a histogram, an example of a first frequency distribution showing the relationship between the exposure period and the light receiving frequency, which can be obtained in the above-mentioned example of the number of microframes. Since 10 microframes are measured in one exposure period, the maximum value of the vertical axis of the histogram is 10. Note that in the examples of Figs. 12, 14, and 15, it is assumed that the same incident light as in the example of Fig. 10 is incident.

[0082] As described above, in the exposure period "1" based on the light emission timing LA12, the incident light corresponding to the exposure period "11" based on the light emission timing LB11 can also be detected in a superimposed manner. The same is true for the other exposure periods. Therefore, the light reception frequency information for the exposure period "11" to "15" (third range) is superimposed on the light reception frequency information obtained for the exposure period "1" to "5" (first range). In this way, a first frequency distribution in which the information for the first range and the third range is superimposed is obtained.

[0083] FIG. 13(a) and FIG. 13(b) are timing charts showing the distance measurement method according to this embodiment. In the distance measurement method of FIG. 13(a) and FIG. 13(b), the position of the second timing relative to the first timing is different from that shown in FIG. 11(a) and FIG. 11(b). In FIG. 13(a) and FIG. 13(b), the second timing is the exposure period between "10" and "11", that is, the start position of the third range. In FIG. 13(a) and FIG. 3(b), the light emission timings LB11, LB12, and LB13 in FIG. 11(a) and FIG. 11(b) are replaced with light emission timings LC11, LC12, and LC13. Other than this, it is generally the same as FIG. 11(a) and FIG. 11(b).

[0084] In FIG. 13(a), there are two light emission timings LA11 and LC11 in the first microframe period. Similarly, there are two light emission timings LA12 and LC12 in the second microframe period. Here, focusing on the period T3 in FIG. 13(a) which corresponds to the exposure period of the second microframe, this period is the exposure period "1" based on the light emission timing LA12 and also the exposure period "6" based on the light emission timing LC11. In this subframe, a signal is acquired which is the sum of the exposure period "1" based on the light emission timings LA11, LA12, and LA13 (first timing) and the exposure period "6" based on the light emission timings LC11, LC12, and LC13 (second timing).

[0085] FIG. 13(b) shows the next subframe of FIG. 13(a). In FIG. 13(b), there are two light emission timings LA21 and LC21 in the first microframe period. Similarly, there are two light emission timings LA22 and LC22 in the second microframe period. Here, focusing on the period T4 in FIG. 13(b) which corresponds to the exposure period of the second microframe, this period is the exposure period "2" based on the light emission timing LA22 and also the exposure period "7" based on the light emission timing LC21. In this subframe, a signal is acquired which is the sum of the exposure period "2" based on the light emission timings LA21, LA22, and LA23 (first timing) and the exposure period "7" based on the light emission timings LC21, LC22, and LC23 (second timing).

[0086] 13(a) and 13(b) show two subframe periods with exposure periods "1" and "2", and then the same process is performed while shifting the exposure period from "3" to "5". As a result, a total of five subframes are acquired for generating the second frequency distribution. That is, in acquiring the second frequency distribution, the number of subframes per frame is 5, and the number of microframes per subframe is 10, so the number of microframes per frame is 50.

[0087] Fig. 14 is a histogram showing the second frequency distribution obtained by the distance measuring method according to the present embodiment. Fig. 14 shows an example of the second frequency distribution showing the relationship between the exposure period and the light receiving frequency, which can be obtained in the above-mentioned example of the number of microframes, in the form of a histogram. Since 10 microframes are measured in one exposure period, the maximum value of the vertical axis of the histogram is 10.

[0088] FIG. 15 is a histogram showing a third frequency distribution generated by the frequency distribution generating unit 134 according to this embodiment. The frequency distribution generating unit 134 generates a third frequency distribution showing the relationship between the exposure periods "1" to "15" and the light reception frequency based on the first frequency distribution and the second frequency distribution. FIG. 15 shows an example of the third frequency distribution generated from the first frequency distribution in FIG. 12 and the second frequency distribution in FIG. 14. In the example shown in FIG. 15, when the exposure period is "10", the light reception frequency is the maximum value. That is, a peak P2 exists at the position of "10". In this case, it is determined that the object X exists at the distance corresponding to "10".

[0089] FIG. 16 is a flowchart showing a frequency distribution generation process in the frequency distribution generation unit 134 according to this embodiment. A method for generating the third frequency distribution will be described in more detail with reference to FIG. 16. In the process of FIG. 16, it is assumed that the first frequency distribution and the second frequency distribution for one ranging frame have been acquired in advance, and that the first frequency distribution and the second frequency distribution are stored in the first storage unit 133. In the following description, the frequency corresponding to the exposure period "k" of the first frequency distribution will be expressed as "first frequency [k]". The same applies to the second frequency distribution and the third frequency distribution.

[0090] In step S11, the frequency distribution generation unit 134 acquires the first frequency distribution and the second frequency distribution from the first holding unit 133. As described above, the first frequency distribution and the second frequency distribution are acquired in the range of exposure periods "1" to "5." Therefore, in this process, the frequency distribution generation unit 134 acquires the first frequency [1] to the first frequency [5] and the second frequency [1] to the second frequency [5].

[0091] In step S12, the frequency distribution generating unit 134 initializes a loop counter variable n to 1. Note that n is an integer from 1 to 5. Also, "←" in Fig. 16 is an assignment operator meaning a process of assigning a value on the right side to a variable on the left side.

[0092] In the subsequent steps S13, S14, and S17, a determination is made based on the first frequency [n] and the second frequency [n] in the same section of the first frequency distribution and the second frequency distribution. Then, in steps S15, S16, S18, and S19, a process is performed to determine the frequency of the third frequency distribution based on the result of this determination and the values ​​of the first frequency [n] and the second frequency [n].

[0093] In step S13, the frequency distribution generating unit 134 determines whether the difference between the first frequency [n] and the second frequency [n] (the absolute value of (second frequency [n] - first frequency [n])) is smaller than a predetermined first threshold. If the difference is smaller than the first threshold (YES in step S13), the process proceeds to step S14. In this case, the frequency of received light in the exposure period "n" is due to reflected light of the light emitted at the first timing or disturbance light. If the difference is equal to or greater than the first threshold (NO in step S13), the process proceeds to step S17. In this case, the frequency of received light in the exposure period "n" is due to reflected light of the light emitted at the second timing.

[0094] In step S14, the frequency distribution generating unit 134 determines whether the first frequency [n] is greater than a predetermined second threshold. If the first frequency [n] is greater than the second threshold (YES in step S14), the process proceeds to step S15. In this case, the frequency of light reception in the exposure period "n" is due to reflected light of the light emitted at the first timing. If the first frequency [n] is equal to or less than the second threshold (NO in step S14), the process proceeds to step S16. In this case, the frequency of light reception in the exposure period "n" is due to ambient light.

[0095] In step S15, the frequency distribution generating unit 134 assigns the value of the first frequency [n] to the third frequency [n], and assigns zero to the third frequency [n+5] and the third frequency [n+10]. Then, the process proceeds to step S20. Since it was determined in the processes of steps S13 and S14 that the light reception frequency in the exposure period "n" is due to the reflected light of the light emission at the first timing, in step S15, the value of the first frequency distribution is applied as the value of the third frequency distribution.

[0096] In step S16, the frequency distribution generating unit 134 assigns zero to the third frequency [n], the third frequency [n+5], and the third frequency [n+10]. Then, the process proceeds to step S20. Since it was determined in the processes of steps S13 and S14 that the light reception frequency in the exposure period "n" is due to disturbance light, in step S16, the values ​​of the first frequency distribution and the second frequency distribution are not used, and zero is applied as the value of the third frequency distribution.

[0097] In step S17, the frequency distribution generating unit 134 determines whether the first frequency [n] is greater than the second frequency [n]. If the first frequency [n] is greater than the second frequency [n] (YES in step S17), the process proceeds to step S18. In this case, the light reception frequency in the exposure period "n" is due to the reflected light of the light emission at the second timing in obtaining the first frequency distribution as shown in FIG. 11. If the first frequency [n] is equal to or less than the second threshold (NO in step S17), the process proceeds to step S19. In this case, the light reception frequency in the exposure period "n" is due to the reflected light of the light emission at the second timing in obtaining the second frequency distribution as shown in FIG. 13.

[0098] In step S18, the frequency distribution generating unit 134 assigns the value of the first frequency [n] to the third frequency [n+10], and assigns zero to the third frequency [n] and the third frequency [n+5]. After that, the process proceeds to step S20. Since it was determined in the processes of steps S13 and S17 that the light reception frequency in the exposure period "n" is due to the reflected light of the light emitted at the second timing in obtaining the first frequency distribution, in step S18, the first frequency distribution is applied as the value of the third frequency distribution. At this time, the exposure period to which the value is applied is shifted by the time difference between the first timing and the second timing.

[0099] In step S19, the frequency distribution generating unit 134 assigns the value of the second frequency [n] to the third frequency [n+5], and assigns zero to the third frequency [n] and the third frequency [n+10]. After that, the process proceeds to step S20. In the processes of steps S13 and S17, it is determined that the light reception frequency in the exposure period "n" is due to the reflected light of the light emission at the second timing in obtaining the second frequency distribution, so in step S19, the second frequency distribution is applied as the value of the third frequency distribution. At this time, the exposure period to which the value is applied is shifted by the time difference between the first timing and the second timing. In this way, in steps S17 to S19, the process is performed such that the larger of the first frequency [n] and the second frequency [n] is applied to the frequency of the third frequency distribution.

[0100] In step S20, the frequency distribution generating unit 134 determines whether the value of the loop counter variable n is 5, that is, whether the processing has been completed for the number of shifts in the exposure period. If the value of the loop counter variable n is 5 (YES in step S20), the processing proceeds to step S22. If the value of the loop counter variable n is not 5 (NO in step S20), the processing proceeds to step S21.

[0101] In step S21, the frequency distribution generating unit 134 increments the value of the loop counter variable n (adds 1 to the variable n). After that, the process proceeds to step S13, where the same process is repeated.

[0102] In step S22, the frequency distribution generation unit 134 outputs the generated third frequency distribution to the second holding unit 135. The second holding unit 135 holds the generated third frequency distribution. This ends the frequency distribution generation process.

[0103] The above-mentioned first and second thresholds are values ​​that are set in advance in consideration of distance measurement conditions, environment, etc. Examples of factors to be considered when setting the first and second thresholds include the number of microframes per subframe, the amount of ambient light in the distance measurement environment, etc.

[0104] By applying the process of FIG. 16 to the first frequency distribution of FIG. 12 and the second frequency distribution of FIG. 14, the third frequency distribution of FIG. 15 is obtained. For example, in the case of the exposure period "5", the first frequency [5] is zero from FIG. 12, and the second frequency [5] is 9 from FIG. 14. Since the difference between the first frequency [5] and the second frequency [5] is sufficiently large and the first frequency [5] is greater than the second frequency [5], the process of step S19 is performed. That is, the value 9 of the second frequency [5] is substituted for the third frequency

[10] , and 0 is substituted for the third frequency [5] and the third frequency

[15] . Therefore, the peak P2 of the light receiving frequency 9 is detected at the position "10" as shown in FIG. 15.

[0105] In this way, the method of this embodiment can generate a frequency distribution that can detect a peak, similar to the comparative example. Comparing FIG. 10 and FIG. 15, although the light reception frequency of the portion other than the peak is different, the same light reception frequency peak is obtained for the peak at the position of "10", and the same distance can be calculated. On the other hand, the number of microframes required to generate the frequency distribution of FIG. 10 is 150, whereas the number of microframes required to generate the frequency distribution of FIG. 10 is 100, so the number of microframes is reduced. This allows the length of the distance measurement frame period to be shortened.

[0106] In this embodiment, the length of the shift range of the exposure period in acquiring the first frequency distribution or the second frequency distribution is shorter than the length of one microframe period corresponding to the distance measurement range of the third frequency distribution. In addition, the sum of the length of the shift range of the exposure period in acquiring the first frequency distribution and the length of the shift range of the exposure period in acquiring the second frequency distribution is also shorter than the length of one microframe period. In other words, by performing light emission multiple times in one microframe period, it is possible to acquire the frequency distribution of the entire distance measurement range simply by shifting the exposure period by an amount corresponding to a part of the distance measurement range. This shortens the length of the distance measurement frame period and improves the frame rate. Therefore, according to this embodiment, a distance measurement device and a distance measurement method that can improve the frame rate are provided.

[0107] [Second embodiment] In this embodiment, a modified example in which a period outside the range measurement target is included in the microframe period will be described. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0108] FIG. 17 is a timing chart showing the distance measurement method according to this embodiment. FIG. 17 shows the relationship between a plurality of light emission timings in a microframe period and the distance measurement range. As in the first embodiment, one microframe period is divided into 15 periods from "1" to "15". In FIG. 17, the light emission timings LA11 and LA12, which are the first timings, are repeated at a constant cycle and correspond to the start time or end time of the microframe period. The light emission timing LB11, which is the second timing, is located between the exposure periods "9" and "10" in the microframe period, and the light emission timing LC11, which is the second timing, is located between the exposure periods "12" and "13" in the microframe period. As in the first embodiment, the second timing is variable to one of two types of timing. Although both the light emission timings LB11 and LC11 are shown in FIG. 17, either the light emission timing LB11 or the light emission timing LC11 is applied depending on the subframe period.

[0109] In the first embodiment, all of the microframe periods from "1" to "15" are within the distance measurement range. In contrast, in the present embodiment, the microframe periods from "1" to "9" are within the distance measurement range, and the period after these (i.e., long distance), from "10" to "15" (fourth range), is outside the distance measurement range. That is, the third frequency distribution includes frequency information corresponding to "1" to "9" but does not include frequency information corresponding to "10" to "15". This method is applicable to applications in which some distance ranges are excluded from the distance measurement range, such as when measuring only short distances and when distance measurement accuracy cannot be ensured due to the influence of light attenuation or the like at distances farther than a certain distance.

[0110] The distance measurement range in one microframe period is divided into three equally spaced ranges. That is, the distance measurement range in one microframe period is divided into a first range including "1" to "3", a second range including "4" to "6", and a third range including "7" to "9". In this embodiment, the exposure period is shifted only in the first range, i.e., the range from "1" to "3", rather than the entire microframe period.

[0111] Focus on the period T5 in FIG. 17, that is, the exposure period "1" to "3" (first range) based on the light emission timing LA12. The exposure period "7" to "9" (third range) based on the light emission timing LB11 is included in the period T5. The exposure period "4" to "6" (second range) based on the light emission timing LC11 is also included in the period T5. By shifting the exposure period within the range of the exposure period "1" to "3" based on the light emission timing LA12 and performing the measurement, it is possible to obtain information on the reflected light that is incident during the exposure period "7" to "9" or the exposure period "4" to "6". Therefore, the first frequency distribution and the second frequency distribution can be obtained by the same method as in the first embodiment, and the third frequency distribution can be obtained from the first frequency distribution and the second frequency distribution.

[0112] Therefore, according to this embodiment, a distance measuring device and a distance measuring method are provided that can improve the frame rate, similarly to the first embodiment, even when a period not subject to distance measurement is included within a microframe period.

[0113] [Third embodiment] In this embodiment, a modified example in which the microframe period is not equally divided will be described. In this embodiment, the description of elements common to the first embodiment may be omitted or simplified.

[0114] FIG. 18 is a timing chart showing the distance measurement method according to this embodiment. FIG. 18 shows the relationship between a plurality of light emission timings in a microframe period and the distance measurement range. One microframe period is divided into eleven periods from "1" to "11". In FIG. 17, the light emission timings LA11 and LA12, which are the first timings, are repeated at a constant cycle and correspond to the start time or end time of the microframe period. The light emission timing LB11, which is the second timing, is located between the exposure periods "4" and "5" in the microframe period, and the light emission timing LC11, which is the second timing, is located between the exposure periods "8" and "9" in the microframe period. As in the first embodiment, the second timing is variable to one of two types of timing. Although both the light emission timings LB11 and LC11 are shown in FIG. 18, one of the light emission timings LB11 and LC11 is applied depending on the subframe period.

[0115] One microframe period is divided into three equal lengths. That is, one microframe period is divided into a first range including "1" to "4", a second range including "4" to "7", and a third range including "8" to "11". In this embodiment, the exposure period is shifted only in the first range, i.e., the range from "1" to "4", not the entire microframe period. Thus, in this embodiment, the exposure period "4" overlaps between the first range and the second range.

[0116] Focus on the period T6 in FIG. 18, that is, the exposure period "1" to "4" (first range) based on the light emission timing LA12. The exposure period "8" to "11" (third range) based on the light emission timing LB11 is included in the period T5. The exposure period "4" to "7" (second range) based on the light emission timing LC11 is also included in the period T5. By shifting the exposure period within the range of the exposure period "1" to "4" based on the light emission timing LA12 and performing the measurement, it is possible to obtain information on the reflected light that is incident during the exposure period "8" to "11" or the exposure period "4" to "7". Therefore, the first frequency distribution and the second frequency distribution can be obtained by the same method as in the first embodiment, and the third frequency distribution can be obtained from the first frequency distribution and the second frequency distribution. In this method, although some exposure periods (exposure period "4" in this example) are acquired overlapping in the first frequency distribution or the second frequency distribution, it is possible to acquire a third frequency distribution as in the first embodiment.

[0117] Therefore, according to this embodiment, even if the microframe period is not divided equally, a distance measuring device and a distance measuring method capable of improving the frame rate are provided, similarly to the first embodiment.

[0118] [Fourth embodiment] 19(a) and 19(b) are block diagrams of devices related to the vehicle-mounted distance measuring device in this embodiment. The device 80 has a distance measuring unit 803, which is an example of the distance measuring device 1 in the above-mentioned embodiment, and a signal processing device (processing device) that processes a signal from the distance measuring unit 803. The device 80 has a distance measuring unit 803 that measures the distance to an object, and a collision determination unit 804 that determines whether or not there is a possibility of collision based on the measured distance. Here, the distance measuring unit 803 is an example of a distance information acquisition means that acquires distance information to the object. In other words, the distance information is information related to the distance to the object, etc. The collision determination unit 804 may use the distance information to determine the possibility of collision.

[0119] The device 80 is connected to a vehicle information acquisition device 810, and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. In addition, the device 80 is connected to a control ECU 820, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 804. In addition, the device 80 is also connected to an alarm device 830 that issues an alarm to the driver based on the judgment result of the collision judgment unit 804. For example, when the judgment result of the collision judgment unit 804 indicates that there is a high possibility of a collision, the control ECU 820 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 830 warns the user by sounding an alarm such as a sound, displaying alarm information on the screen of a car navigation system, etc., and applying vibrations to a seat belt or steering wheel. These devices of the device 80 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0120] In this embodiment, the device 80 measures distances around the vehicle, for example, in front or behind. Fig. 19(b) shows the device when measuring distances in front of the vehicle (distance measurement range 850). A vehicle information acquisition device 810 as a distance measurement control means sends an instruction to the device 80 or distance measurement unit 803 to perform a distance measurement operation. With this configuration, the accuracy of distance measurement can be further improved.

[0121] 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.

[0122] [Modified embodiment] The present invention is not limited to the above-described embodiments and can be modified in various ways. For example, an example in which a part of the configuration of any of the embodiments is added to another embodiment, or an example in which a part of the configuration of any of the embodiments is replaced with a part of the configuration of another embodiment, is also an embodiment of the present invention.

[0123] The disclosure of this specification includes the complement of the concepts described in this specification. In other words, if the specification states, for example, that "A is B" (A=B), the specification is deemed to disclose or suggest that "A is not B" even if the statement that "A is not B" (A≠B) is omitted. This is because when it states that "A is B," it is assumed that the case that "A is not B" is taken into consideration.

[0124] The disclosure of this specification includes the following configurations and methods. (Configuration 1) a timing generation unit that generates a first timing that is periodically repeated and a second timing that is different from the first timing and that is periodically repeated, and supplies the first timing and the second timing to a light emitting device as information indicating a light emission timing; a light receiving section that generates a signal based on incident light that is incident during an exposure period; an exposure period control unit that performs control to shift the exposure period based on the first timing; a frequency distribution generating unit that generates a frequency distribution indicating a relationship between time information from light emission by the light emitting device to light reception by the light receiving unit and a frequency of light reception by the light receiving unit, based on a signal generated by the light receiving unit and information indicating an amount of shift of the exposure period; having The length of the shift range of the exposure period is shorter than the length of the cycle of the first timing. A distance measuring device comprising: (Configuration 2) one period of the first timing includes a first range, a second range, and a third range, The shift range of the exposure period corresponds to the first range. 2. The distance measuring device according to configuration 1, (Configuration 3) The length of the first range, the length of the second range, and the length of the third range are equal to each other. 3. The distance measuring device according to configuration 2. (Configuration 4) The first range, the second range, and the third range do not overlap with each other. 4. The distance measuring device according to configuration 2 or 3. (Configuration 5) Two of the first range, the second range, and the third range partially overlap. 4. The distance measuring device according to configuration 2 or 3. (Configuration 6) one period of the first timing includes a fourth range that does not overlap with any of the first range, the second range, and the third range, The frequency distribution does not include information on the frequency corresponding to the fourth range. 6. The distance measuring device according to any one of configurations 2 to 5. (Configuration 7) In one cycle of the first timing, the fourth range is later than any of the first range, the second range, and the third range. 7. The distance measuring device according to configuration 6. (Configuration 8) The shift range of the exposure period is set so that frequency information corresponding to the first range is obtained based on the light emitted from the light emitting device at the first timing, and frequency information corresponding to the second range or the third range is obtained based on the light emitted from the light emitting device at the second timing. 8. The distance measuring device according to any one of configurations 2 to 7, (Configuration 9) The frequency distribution generating unit generates a first frequency distribution including frequency information corresponding to the first range and frequency information corresponding to the third range, and a second frequency distribution including frequency information corresponding to the first range and frequency information corresponding to the second range. 9. The distance measuring device according to any one of configurations 2 to 8. (Configuration 10) The timing generation unit switches a time difference of the second timing with respect to the first timing, thereby switching between a state in which the frequency distribution generation unit generates the first frequency distribution and a state in which the frequency distribution generation unit generates the second frequency distribution. 10. The distance measuring device according to configuration 9. (Configuration 11) The frequency distribution generating unit generates a third frequency distribution based on the first frequency distribution and the second frequency distribution. 11. The distance measuring device according to configuration 9 or 10. (Configuration 12) The frequency distribution generating unit determines the frequency of the third frequency distribution based on the values ​​of the first frequency and the second frequency in the same section of the first frequency distribution and the second frequency distribution. 12. A distance measuring device according to claim 11, (Configuration 13) When a difference between the first frequency and the second frequency is equal to or greater than a first threshold, the frequency distribution generating unit applies only the larger of the first frequency and the second frequency to the frequency of the third frequency distribution. 13. A distance measuring device according to claim 12. (Configuration 14) The frequency distribution generating unit applies the first frequency to the frequency of the third frequency distribution when a difference between the first frequency and the second frequency is smaller than a first threshold value and the first frequency is larger than a second threshold value. 14. The distance measuring device according to configuration 12 or 13. (Configuration 15) When a difference between the first frequency and the second frequency is smaller than a first threshold and the first frequency is equal to or smaller than a second threshold, the frequency distribution generating unit does not apply either the first frequency or the second frequency to the frequency of the third frequency distribution. 15. A distance measuring device according to any one of configurations 12 to 14. (Configuration 16) The third frequency distribution includes frequency information corresponding to the first range, frequency information corresponding to the second range, and frequency information corresponding to the third range. 16. A distance measuring device according to any one of configurations 11 to 15. (Configuration 17) A distance is calculated based on an amount of shift corresponding to a frequency peak in the third frequency distribution. 17. A distance measuring device according to any one of configurations 11 to 16. (Configuration 18) A distance measuring device according to any one of configurations 1 to 17, a processing device for processing distance information acquired by the distance measuring device; An apparatus comprising: (Configuration 19) A mobile object, A distance measuring device according to any one of configurations 1 to 17, a moving object control unit that controls the moving object based on distance information acquired by the distance measuring device; A moving object comprising: (Method 1) generating a first timing that is periodically repeated and a second timing that is different from the first timing and that is periodically repeated; supplying the first timing and the second timing to a light emitting device as information indicating a light emission timing; generating a signal based on incident light that is incident during an exposure period while shifting the exposure period based on the first timing; generating a frequency distribution indicating a relationship between time information from light emission by the light emitting device to reception of the incident light and a frequency of light reception based on the generated signal and information indicating the shift amount of the exposure period; having The length of the shift range of the exposure period is shorter than the length of the cycle of the first timing. A distance measuring method comprising:

[0125] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) for implementing one or more of the functions.

[0126] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features. [Explanation of symbols]

[0127] 1 Ranging device 120 Light emitting part 131 Timing Generation Unit 132 Exposure period control section 134 Frequency distribution generator 140 Light receiving part

Claims

1. A timing generation unit generates a first timing that repeats periodically and a second timing that is different from the first timing and also repeats periodically, and supplies the first timing and the second timing to a light-emitting device as information indicating the light-emitting timing. A light-receiving unit that generates a signal based on incident light that enters during the exposure period, An exposure period control unit that controls the shifting of the exposure period based on the first timing, A frequency distribution generation unit generates a frequency distribution showing the relationship between time information from the emission of light by the light-emitting device to the reception of light by the light-receiving unit and the frequency of light reception by the light-receiving unit, based on the signal generated in the light-receiving unit and information indicating the amount of shift in the exposure period. It has, The length of the shift range during the exposure period is shorter than the length of the period corresponding to the distance measurement range. A distance measuring device characterized by the following features.

2. The period corresponding to the distance measurement range includes the first range, the second range, and the third range. The shift range of the exposure period corresponds to the first range The distance measuring device according to feature 1.

3. The lengths of the first range, the second range, and the third range are equal to each other. The distance measuring device according to feature 2.

4. The first range, the second range, and the third range do not overlap with each other. The distance measuring device according to feature 2.

5. Two of the first, second, and third ranges overlap in part. The distance measuring device according to feature 2.

6. The period corresponding to the distance measurement range includes a fourth range that does not overlap with any of the first range, the second range, and the third range. The frequency distribution does not include frequency information corresponding to the fourth range. The distance measuring device according to feature 2.

7. During the period corresponding to the distance measurement range, the fourth range is later than any of the first range, the second range, and the third range. The distance measuring device according to feature 6.

8. The shift range of the exposure period is set such that frequency information corresponding to the first range is acquired based on the light emitted from the light-emitting device at the first timing, and frequency information corresponding to the second or third range is acquired based on the light emitted from the light-emitting device at the second timing. The distance measuring device according to feature 2.

9. The frequency distribution generation unit generates a first frequency distribution including frequency information corresponding to the first range and frequency information corresponding to the third range, and a second frequency distribution including frequency information corresponding to the first range and frequency information corresponding to the second range. The distance measuring device according to feature 2.

10. The timing generation unit switches between a state in which the frequency distribution generation unit generates the first frequency distribution and a state in which the frequency distribution generation unit generates the second frequency distribution by switching the time difference between the first timing and the second timing. The distance measuring device according to feature 9.

11. The frequency distribution generation unit generates a third frequency distribution based on the first and second frequency distributions. The distance measuring device according to feature 9.

12. The frequency distribution generation unit determines the frequency of the third frequency distribution based on the values ​​of the first and second frequencies in the same interval of the first and second frequency distributions. The distance measuring device according to feature 11.

13. The frequency distribution generation unit applies only the larger of the first and second frequencies to the frequency of the third frequency distribution if the difference between the first frequency and the second frequency is greater than or equal to a first threshold. The distance measuring device according to feature 12.

14. The frequency distribution generation unit applies the first frequency to the frequency of the third frequency distribution when the difference between the first frequency and the second frequency is less than the first threshold and the first frequency is greater than the second threshold. The distance measuring device according to feature 12.

15. The frequency distribution generation unit does not apply either the first or second frequency to the frequencies of the third frequency distribution if the difference between the first frequency and the second frequency is less than the first threshold, and the first frequency is less than or equal to the second threshold. The distance measuring device according to feature 12.

16. The third frequency distribution includes frequency information corresponding to the first range, frequency information corresponding to the second range, and frequency information corresponding to the third range. The distance measuring device according to feature 11.

17. The distance is calculated based on the shift amount corresponding to the peak of the frequency in the third frequency distribution. The distance measuring device according to feature 11.

18. A distance measuring device according to any one of claims 1 to 17, A processing device for processing distance information acquired by the distance measuring device, A device characterized by being equipped with the following features.

19. It is a mobile object, A distance measuring device according to any one of claims 1 to 17, A mobile body control unit that controls the mobile body based on distance information acquired by the distance measuring device, A mobile body characterized by having the following features.

20. A step of generating a first timing that is repeated periodically and a second timing that is different from the first timing and is repeated periodically, The steps include supplying the first timing and the second timing to the light-emitting device as information indicating the light-emitting timing, A step of generating a signal based on incident light incident during the exposure period while shifting the exposure period with reference to the first timing, A step of generating a frequency distribution that shows the relationship between the time information from the emission of light by the light-emitting device to the reception of the incident light and the frequency of reception, based on the generated signal and information indicating the amount of shift of the exposure period, It has, The length of the shift range during the exposure period is shorter than the length of the period corresponding to the distance measurement range. A distance measurement method characterized by the following features.

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