Ranging device

Abstract

A ranging device according to the present invention has: a light-emitting element array including a plurality of light-emitting elements; a light-receiving element array including a plurality of light-receiving elements; a timekeeping unit that measures time; a beam splitter having a half-silvered mirror and a reflective surface; and a ranging unit that measures the distance to an object on the basis of the time measured by the timekeeping unit, wherein light emitted from the light-emitting elements is divided into first light and second light by the half-silvered mirror, the first light is reflected by the object and incident on any of the plurality of light-receiving elements, the second light is reflected by the reflective surface and incident on any of the plurality of light-receiving elements, and the ranging unit measures the distance to the object on the basis of the time obtained by subtracting the time until the second light was reflected by the reflective surface and incident on any of the plurality of light-receiving elements from the time until the first light was reflected by the object and incident on any of the plurality of light-receiving elements.

Description

distance measuring device

[0001] The present invention relates to a distance measuring device.

[0002] A time-of-flight (TOF) distance measurement method is known, which measures the distance to an object by measuring the time from when a light-emitting element emits light until reflected light is detected.

[0003] Patent Document 1 discloses a configuration in which a plurality of light-emitting elements and a plurality of light-receiving elements are arranged in a two-dimensional array, light is irradiated onto an object through an imaging lens, and the reflected light is received through the imaging lens, thereby acquiring three-dimensional distance information without a drive unit. In such a configuration, the angle of view of the light-emitting element array and the angle of view of the light-receiving element array must be approximately equal. In order to reduce the size of the distance measuring device, it is desirable to make the size of the light-emitting element array and the size of the light-receiving element array approximately equal and to use a common imaging lens for the light-emitting element array and the light-receiving element array.

[0004] Patent Document 2 discloses a configuration for improving distance measurement accuracy by calculating the time difference between a reference light corresponding to the timing of emitting a laser and a reflected light reflected by an object.

[0005] JP 2019-60652 A JP 2014-174069 A

[0006] However, in the configuration disclosed in Patent Document 2, it is necessary to provide an optical system for receiving the reference light in addition to the optical system for receiving the reflected light, which increases the size of the distance measuring device.

[0007] An object of the present invention is to provide a small distance measuring device capable of measuring distances with high accuracy.

[0008] The distance measuring device of the present invention comprises an array of light-emitting elements including a plurality of light-emitting elements, an array of light-receiving elements including a plurality of light-receiving elements, a timing unit that measures time, a beam splitter having a half mirror and a reflective surface, and a distance measuring unit that measures the distance to an object based on the time measured by the timing unit, wherein light emitted from the light-emitting element is separated into first light and second light by the half mirror, the first light is reflected by the object and enters one of the plurality of light-receiving elements, and the second light is reflected by the reflective surface and enters one of the plurality of light-receiving elements, and the distance measuring unit measures the distance to the object based on the time obtained by subtracting the time taken for the second light to be reflected by the reflective surface and enter one of the plurality of light-receiving elements from the time taken for the first light to be reflected by the object and enter one of the plurality of light-receiving elements.

[0009] According to the present invention, it is possible to provide a small-sized distance measuring device capable of measuring distances with high accuracy.

[0010] FIG. 1 is a block diagram of a distance measuring device. FIG. 2 is a block diagram of a light-emitting unit. FIG. 3 is a block diagram of a measurement unit. FIG. 4 is a schematic diagram of a pixel. FIG. 5 is a block diagram of a TDC array. FIG. 6 is a schematic diagram of an oscillator. FIG. 7 is a table showing temporal changes in the output signal of a buffer and the internal signal of the oscillator. FIG. 8 is a timing chart showing the end of the counting operation of the TDC. FIG. 9 is an enlarged view of a portion of FIG. 8. FIG. 10 is a block diagram of an oscillation adjustment circuit. FIGS. 11A to 11D are cross-sectional views of a beam splitter according to the first embodiment. FIG. 12 is a flowchart of a distance measuring operation according to the first embodiment. FIG. 13 is a schematic diagram of a histogram according to the first embodiment. FIG. 14 is a flowchart of a distance measuring operation according to a modification of the first embodiment. FIGS. 15A to 15D are cross-sectional views of a beam splitter according to the second embodiment. FIG. 16 is a schematic diagram of a histogram according to the second embodiment. FIG. 17 is a schematic diagram of a pixel according to the third embodiment. FIG. 18 is a schematic diagram of a distance measurement operation according to the third embodiment.

[0011] First Embodiment A first embodiment of the present invention will be described.

[0012] 1 is a block diagram showing an outline of an example configuration of a distance measuring device according to embodiment 1. Solid arrows connecting blocks (components) indicate signal exchange, dashed arrows indicate irradiating light onto an object, and dashed arrows indicate reflected light from the object.

[0013] The distance measuring device includes a light emitting unit 110 , a measurement unit 120 , an imaging lens 130 , an overall control unit 140 , and a beam splitter 150 .

[0014] The light-emitting unit 110 has a light source unit 113 and a light source control unit 114. The light source unit 113 has a light-emitting element array 111 including a plurality of light-emitting elements, and a light-emitting element drive unit 112 that drives each light-emitting element in accordance with instructions from the light source control unit 114. In the first embodiment, the plurality of light-emitting elements are arranged in a two-dimensional array (matrix), and the light source control unit 114 (light-emitting control unit) causes the light-emitting elements in each row to emit light individually.

[0015] The measurement unit 120 includes a light receiving element array 121, a TDC (Time-to-Digital Converter) array 122, a signal processing unit 123, a measurement control unit 124, and a row selection circuit 125. The light receiving element array 121 includes multiple light receiving elements. In the first embodiment, the multiple light receiving elements are arranged in a two-dimensional array (matrix). The TDC array 122 is a timing unit that measures time. The signal processing unit 123 is a distance measurement unit that performs predetermined signal processing to measure distance. The measurement control unit 124 controls the operation of the measurement unit 120. The row selection circuit 125 selects the row of light receiving elements that receive light (light receiving elements to be enabled). Note that a bandpass filter that transmits light of wavelengths including the wavelength of the light emitted from the light emitting element array 111 and reflects or absorbs light of other wavelengths may be arranged on the light receiving element array 121.

[0016] The beam splitter 150 has a half mirror 151 that transmits part of the light and reflects part of it, and a reflecting surface 152 that reflects the light.

[0017] The overall control unit 140 controls the operation of the entire distance measuring device. For example, the overall control unit 140 has a CPU, ROM, and RAM, and the CPU controls each unit of the distance measuring device by loading a program stored in the ROM into the RAM and executing it. At least a part of the overall control unit 140 may be realized by a dedicated hardware circuit.

[0018] When each light-emitting element emits pulsed light, pulsed light is output into space via the imaging lens 130. The pulsed light emitted from different light-emitting elements is output to different angles of view (ranges) in space. A portion of the output light (irradiated light) is reflected by the object and enters the light-receiving element array 121 as reflected light via the imaging lens 130. The time from when the light-emitting element emits irradiation light to when the light-receiving element array 121 receives the reflected light is the time of flight (TOF), and this time is measured by the TDC array 122.

[0019] However, in a single measurement, noise due to ambient light and dark counts, noise from each circuit used in the measurement, and noise due to the time between the emission of a light emission signal (a drive signal for causing a light-emitting element to emit light) and the actual emission of light by the light-emitting element have a large impact on the measurement result. In other words, in a single measurement, the measurement error due to these noises is large. For this reason, the TDC array 122 measures the time of flight TOF multiple times, and the signal processing unit 123 creates a histogram of the results of the multiple measurements and removes noise (for example, averaging the results of the multiple measurements) based on the histogram.

[0020] Furthermore, the time from when the light emission signal is emitted until the light emitting element emits light varies due to individual variations and temperature characteristics of the light emitting element drive unit 112, the light emitting element, the light receiving element, the TDC array 122, the buffer used for signal transmission, etc. Therefore, as will be described in detail later, in embodiment 1, the light emitted from the light emitting element is separated into illumination light and reference light, and the time until the reference light is detected is subtracted from the time until the reflected light from the object is detected to obtain the time of flight TOF. In this way, a time of flight TOF with a small component of the time from when the light emission signal is emitted until the light emitting element emits light can be obtained.

[0021] The signal processing unit 123 measures (calculates) the distance L from the distance measuring device to the object by substituting the obtained time of flight TOF into the following equation (1), where c is the speed of light: L=TOF×c / 2 (1)

[0022] 2, an example of the configuration of the light-emitting unit 110 will be described. As described above, the light-emitting unit 110 includes the light source unit 113 and the light source control unit 114.

[0023] The light-emitting element array 111 has a configuration in which a plurality of light-emitting elements 201, each of which is a vertical cavity surface-emitting laser element (VCSEL), are arranged in a two-dimensional array on a substrate. The light-emitting element drive unit 112 has a configuration in which a plurality of light-emitting element row drive circuits 202 are arranged one-dimensionally (in one column). The plurality of light-emitting element row drive circuits 202 respectively correspond to the plurality of rows of the plurality of light-emitting elements 201. Each light-emitting element row drive circuit 202 drives the light-emitting elements 201 in the corresponding row.

[0024] The light-emitting element 201 is not limited to a VCSEL, but is preferably a light-emitting element that can be integrated in a one-dimensional or two-dimensional array, and may be, for example, an edge-emitting laser or an LED (light-emitting diode). When an edge-emitting laser is used as the light-emitting element 201, a laser bar stack in which laser bars, each having elements arranged in a one-dimensional array, are stacked on a substrate can be used as the light-emitting element array 111. When an LED is used as the light-emitting element 201, an LED array in which LEDs are arranged in a two-dimensional array on a substrate can be used as the light-emitting element array 111.

[0025] Furthermore, the wavelength of the light emitted by the light-emitting element 201 is not particularly limited, but a wavelength in the near-infrared band can suppress the effects of ambient light. VCSELs can be fabricated using semiconductor processes from materials used in edge-emitting lasers and surface-emitting lasers. A VCSEL emitting light with a wavelength in the near-infrared band can be fabricated by using GaAs-based semiconductor materials as the main material. In this case, the dielectric multilayer film forming the DBR (distributed Bragg reflector) reflector constituting the VCSEL can be constructed by alternately and periodically stacking two thin films made of materials with different refractive indices (GaAs / AlGaAs). The wavelength of the light emitted by the VCSEL can be changed by adjusting the element combination and composition of the compound semiconductor.

[0026] The VCSELs (light-emitting elements 201) that make up the VCSEL array (light-emitting element array 111) are provided with electrodes for injecting current and holes into their active layers. An electrode is provided for each row of multiple light-emitting elements 201 and is shared by the VCSELs in the same row. The multiple electrodes are connected to multiple light-emitting element row drive circuits 202, respectively. By operating the light-emitting element row drive circuit 202, current is injected only into the VCSELs in one row connected to that light-emitting element row drive circuit 202, causing only the VCSELs in that row to emit light.

[0027] [Measurement Unit] An example configuration of the measurement unit 120 will be described using FIG. 3 . As described above, the measurement unit 120 includes a photodetector array 121, a TDC array 122, a signal processing unit 123, a measurement control unit 124, and a row selection circuit 125. The photodetector array 121 includes a plurality of pixels 301 arranged in a two-dimensional array. Each pixel includes a photodetector. The row selection circuit 125 is connected to the plurality of pixels 301 of the photodetector array 121 via a plurality of row selection lines 303, and the TDC array 122 is connected to the plurality of pixels 301 via a plurality of pixel output lines 304. The plurality of row selection lines 303 correspond to the plurality of rows of the plurality of pixels 301, respectively, and the pixels 301 in the same row are connected to the same row selection line 303. The plurality of pixel output lines 304 correspond to the plurality of columns of the plurality of pixels 301, respectively, and the pixels 301 in the same column are connected to the same pixel output line 304. The row selection circuit 125 can select one row of the multiple pixels 301 by outputting a signal (selection signal) to one row selection line 303. When one row of the multiple pixels 301 is selected, the TDC array 122 receives only signals output from the pixels 301 in the selected row via pixel output lines 304. As a result, it is possible to detect light reception by each of the multiple pixels 301 in the selected row (multiple light receiving elements in the selected row).

[0028] 4 is a schematic diagram showing an example of the configuration of a pixel 301. The pixel 301 has a SPAD (Single Photon Avalanche Diode) element 401, which is a light-receiving element, a load transistor 402, an inverter 403, and a pixel output circuit 404. The pixel output circuit 404 is connected to a row selection line 303 and a pixel output line 304. The SPAD element 401 is a type of avalanche diode, and has a light-receiving region and an avalanche region.

[0029] When light is incident on the SPAD element 401, photoelectric conversion occurs in the light-receiving region, generating electrons and holes. The positively charged holes are discharged via the anode electrode Vbd. The negatively charged electrons are transported to the avalanche region as signal charges by an electric field set so that the potential decreases toward the avalanche region. The signal charges that reach the avalanche region cause avalanche breakdown due to the strong electric field in the avalanche region, generating an avalanche current.

[0030] When no avalanche current flows, the voltage of the anode electrode Vbd is set so that a reverse bias equal to or greater than the breakdown voltage is applied to the avalanche region of the SPAD element 401. At this time, no current flows through the load transistor 402, so the cathode potential Vc is close to the power supply voltage Vdd, and the inverter output signal is "0."

[0031] When an avalanche current is generated in the SPAD element 401 due to the arrival of a photon, the cathode potential Vc drops and the output of the inverter 403 is inverted. That is, the inverter output changes from "0" to "1." Hereinafter, this operation is referred to as a build-up operation.

[0032] When the cathode potential Vc decreases, the reverse bias applied to the SPAD element 401 decreases, and when the reverse bias becomes equal to or lower than the breakdown voltage, the generation of the avalanche current stops. Hereinafter, this operation is referred to as the quench operation.

[0033] Thereafter, a hole current flows from the power supply voltage Vdd via the load transistor 402, causing the cathode potential Vc to rise, and the inverter output returns from "1" to "0", returning to the state before the arrival of the photon. Hereinafter, this operation is referred to as a recharge operation.

[0034] When a selection signal is not supplied from the row selection line 303, the pixel output circuit 404 does not output the inverter output to the pixel output line 304, and when a selection signal is supplied from the row selection line 303, the pixel output circuit 404 outputs the output of the inverter 403 to the pixel output line 304. The inverter output is output to the TDC array 122 as a low-delay digital signal.

[0035] In this way, only the light incident on the pixels 301 (SPAD elements 401) in the row selected by the row selection circuit 125 can be detected.

[0036] [TDC Array] The TDC array 122 measures the time from when the light-emitting unit 110 emits light until the output signal of the pixel 301 changes from "0" to "1" as the time of flight TOF.

[0037] FIG. 5 is a block diagram showing an example configuration of the TDC array 122. The TDC array 122 has twice the number of TDCs 501 as the number of pixels 301 in one row (the number of columns of the plurality of pixels 301), and can receive output signals from two rows of pixels 301. The output signals from one row of pixels 301 are used to detect reflected light from an object, and the output signals from the other row of pixels 301 are used to detect reference light. In the description of FIG. 3 , a case was described in which the same number of pixel output lines 304 as the number of pixels 301 in one row is used. However, in the first embodiment, twice the number of pixel output lines 304 as the number of pixels 301 in one row are used. The twice the number of pixel output lines 304 as the number of pixels 301 in one row are each connected to the same number of TDCs 501. Two pixel output lines 304 are connected to the pixel output circuit 404 of each pixel 301, and the pixel output circuit 404 outputs a signal (inverter output) to one of the two connected pixel output lines 304. By using different pixel output lines 304 between the rows, the TDC array 122 can receive output signals from the pixels 301 in two rows.

[0038] The TDC 501 has an oscillator 511, an oscillation count circuit 521, and a synchronous clock count circuit 531. The count result of the synchronous clock count circuit 531 constitutes the upper bits, the internal signal of the oscillator 511 constitutes the lower bits, and the count result of the oscillation count circuit 521 constitutes the intermediate bits. In other words, the synchronous clock count circuit 531 performs rough measurements, the internal signal of the oscillator 511 performs fine measurements, and the oscillation count circuit 521 measures the interval between them. Note that each measurement bit may have a redundant bit.

[0039] 6 is a schematic diagram of the oscillator 511. The oscillator 511 has an oscillation start / stop signal generation circuit 640, buffers 611 to 618, an oscillation switch 630, and a delay adjustment current source 620. The buffers 611 to 618 are connected alternately with the oscillation switch 630 in series and in a ring shape.

[0040] 7 is a table showing the time variations of the output signals of the buffers 611 to 618 and the internal signal of the oscillator 511. FIG. 7 shows the output signals of the buffers 611 to 618 and the internal signal of the oscillator 511 at the time of reset. Furthermore, FIG. 7 shows the delay time t ｂｕｆｆ 6 shows the output signals of the buffers 611 to 618 and the internal signal of the oscillator 511 each time the time t passes.

[0041] At the time of reset, the outputs of the buffers 611 to 617 are "0" and the output of the buffer 618 is "1". After the oscillation switch 630 is turned on, the delay time t ｂｕｆｆ After this time has elapsed, only the output of buffer 611, whose input and output are not matched, changes from "0" to "1" (the signal advances by one stage). The outputs of buffers 612 to 618, whose input and output are matched, do not change.

[0042] Furthermore, the delay time t ｂｕｆｆ After the time has elapsed (2 x t ｂｕｆｆ After a certain time has elapsed, only the output of buffer 612, which has an input / output mismatch, changes from "0" to "1" (the signal advances by another stage). The outputs of buffer 611 and buffers 613 to 618, which have an input / output match, do not change.

[0043] In this way, the delay time t ｂｕｆｆ After the oscillation switch 630 is turned on, the output of one buffer with mismatched input and output changes from "0" to "1" in sequence every time 8×t ｂｕｆｆ After this time, the output of all buffers changes to "1" (the signal goes around once), and 16 x t ｂｕｆｆ Afterwards, all buffers change to "0" (the signal goes around twice) and return to the original state.

[0044] After that, 16 x tｂｕｕｆ The output changes in the same way with t ｂｕｆｆ Time measurement is performed with a time resolution of t ｂｕｆｆ is adjusted to 1 / 2 of the synchronous clock by the oscillation adjustment circuit 541 described later. ７ It is adjusted to be.

[0045] The oscillator output, which is the output of the buffer 618, is input to the oscillation count circuit 521. The oscillation count circuit 521 counts the rising edges of the oscillator output, thereby calculating 16×t ｂｕｆｆ Time measurement is performed with a time resolution of .

[0046] 8 is a timing chart from when a light-emitting element belonging to a specific row of the light-emitting element array 111 emits light to when the SPAD element 401 receives light and the counting operation of the TDC 501 ends. The chart shows changes in the cathode potential Vc of the SPAD element 1401, the pixel output signal, the synchronous clock, the count value of the synchronous clock count circuit 531, the output of the oscillation start / stop signal generation circuit, the oscillator output, and the count value of the oscillation count circuit 521.

[0047] The cathode potential Vc of the SPAD element 401 is an analog voltage, with the upper side of the drawing indicating a higher voltage. The synchronous clock, oscillation start / stop signal generation circuit output, and oscillator output are digital signals, with the upper side indicating an ON state and the lower side indicating an OFF state. The count values ​​of the synchronous clock count circuit 531 and the oscillation count circuit 521 are digital values ​​and are shown as decimal numbers.

[0048] 9 is an enlarged view of the oscillation start / stop signal generation circuit output, the oscillator output, the count value of the oscillation count circuit 521, and the oscillator internal signal from time 803 to time 805 in Fig. 8. The oscillator internal signal is a digital value, and is shown as a decimal number.

[0049] 8 and 9, the operation of measuring the time from time 801 when a light-emitting element belonging to a specific row of the light-emitting element array 111 emits light to time 803 when a photon is incident on the SPAD element 401 of the pixel 301 and the pixel output signal changes from 0 to 1 will be described.

[0050] At time 801 synchronized with the rising edge of the synchronous clock supplied via the overall control unit 140, a light emitting signal is sent from the overall control unit 140 to the light emitting unit 110. The synchronous clock count circuit 531 starts counting the rising edges of the synchronous clock from time 801 when the light emitting signal is sent.

[0051] At time 803, a photon reflected by an object is received by the SPAD element 401 of the pixel 301, causing the cathode potential Vc of the SPAD element 401 to drop and the pixel output signal to change from "0" to "1." When the pixel output signal becomes "1," the output of the oscillation start / stop signal generation circuit 640 changes from "0" to "1," and the oscillation switch 630 turns on.

[0052] When the oscillation switch 630 is turned on, oscillation begins, and a signal loop begins inside the oscillator 511 as shown in Fig. 9. Every time the signal makes two cycles inside the oscillator 511, a rising edge appears in the oscillator output, and the oscillation count circuit 521 counts the number of rising edges. Also, at time 803, the synchronous clock count circuit 531 stops counting and holds the count value.

[0053] Time 805 is the timing when the synchronous clock first rises after time 803 when the oscillator 511 is turned on. When the synchronous clock rises at time 805, the output of the oscillation start / stop signal generation circuit 640 becomes "0" and the oscillation switch 630 turns off. When the output of the oscillation start / stop signal generation circuit 640 becomes "0" (when the oscillation switch 630 turns off), oscillation ends and the oscillator internal signal is held as is. Furthermore, because oscillation ends, the oscillation count circuit 521 also stops counting.

[0054] By doing so, the count result D of the synchronous clock count circuit 531 Ｇｃｌｋ The time from time 801 to time 802 is divided into two ７ ×t ｂｕｆｆ The count result D of the oscillation count circuit 521 is ＲＯｃｌｋ The time from time 803 to time 804 is 2 ４ ×tｂｕｆｆ Furthermore, the value measured in units of the oscillator internal signal D ＲＯｉｎ The time from time 804 to time 805 is t ｂｕｆｆ The TDC 501 performs the following processing on these values ​​and outputs the processed values ​​to the signal processing unit 123, thereby completing one measurement operation.

[0055] Count result D of oscillation count circuit 521 ＲＯｃｌｋ and oscillator internal signal D ＲＯｉｎ and are added according to the following formula (2): D ＲＯ =2 ４ ×D ＲＯｃｌｋ +D ＲＯｉｎ ...(2)

[0056] D obtained from equation (2) ＲＯ The time from time 803 to time 805 is t ｂｕｆｆ The time from time 802 to time 805 is equal to one cycle of the synchronous clock, so 2 ７ ×t ｂｕｆｆ Therefore, as shown in the following formula (3), D ＲＯ Subtract D from the obtained value. Ｇｃｌｋ By adding these, the flight time of light (the time from time 801 to time 803) is t ｂｕｆｆ The value measured in units of D ＴｏＦ is obtained. ＴｏＦ =2 ７ ×D Ｇｃｌｋ + (2 ７ -D ＲＯ ) = 2 ７ ×D Ｇｃｌｋ + (2 ７ -24 x D ＲＯｃｌｋ -D ＲＯｉｎ ) ... (3)

[0057] Delay time for one buffer stage t ｂｕｆｆ Since the oscillation frequency fluctuates due to factors arising from the manufacturing process such as transistor manufacturing errors, fluctuations in the voltage applied to the TDC circuit, and temperature, an oscillation adjustment circuit 541 is provided.

[0058] 10 is a block diagram showing an example of the configuration of the oscillation adjustment circuit 541. The oscillation adjustment circuit 541 includes dummy oscillators 1001 and 1 / 2 ３ The dummy oscillator 1001 has the same configuration as the oscillator 511 mounted on the TDC 501.

[0059] The output of the dummy oscillator 1001 is 1 / 2 ３ Input to frequency divider 1002. ３ The frequency divider 1002 divides the frequency of the input clock signal by 2. ３ The phase comparator 1003 outputs a clock signal that is 1 / 2 the synchronous clock. ３ The output of the frequency divider 1002 is input to the phase comparator 1003. The phase comparator 1003 divides the frequency of the synchronous clock by 1 / 2. ３ The phase comparator 1003 compares the frequency of the clock signal output by the frequency divider 1002 with the frequency of the clock signal output by the frequency divider 1003. If the frequency of the synchronous clock is higher, the phase comparator 1003 increases the output voltage, and if the frequency of the synchronous clock is lower, the phase comparator 1003 decreases the output voltage. The output voltage of the phase comparator 1003 is input as an adjustment voltage to the delay adjustment current source 620 of the oscillator 511, so that the oscillation frequency of the oscillator 511 is adjusted to 2 times the frequency of the synchronous clock. ３ The delay is adjusted so that it doubles.

[0060] In this way, the frequency of the oscillator 511 is determined based on the synchronous clock frequency. Therefore, by generating the synchronous clock signal using an external IC that can output a constant frequency regardless of changes in the process, voltage, or temperature, it is possible to suppress variations in the oscillation frequency of the oscillator 511 due to changes in the process, voltage, or temperature. For example, by inputting a clock signal of 160 MHz as the synchronous clock signal, the oscillation frequency of the oscillator 511 becomes 1.28 GHz, which is eight times the synchronous clock frequency. The delay time t of one buffer stage, which is the time resolution of the TDC 501, ｂｕｆｆ becomes 48.8 ps.

[0061] [Reference Light and Object Reflected Light] FIG. 11A is a schematic diagram showing cross sections of the beam splitter 150, the light emitting element array 111, the light receiving element array 121, and the imaging lens 130.

[0062] The light-emitting element array 111 is in a conjugate relationship with the light-receiving element array 121 via the half mirror 151 of the beam splitter 150. The plurality of light-emitting elements of the light-emitting element array 111 are in a conjugate relationship with the plurality of light-receiving elements of the light-receiving element array 121 via the half mirror 151 of the beam splitter 150.

[0063] 11A, the number of rows of the plurality of light-emitting elements and the number of rows of the plurality of light-receiving elements are both eight, but these numbers of rows are not limited to eight. Furthermore, although the light-emitting elements and the light-receiving elements are in one-to-one correspondence, the correspondence (conjugate relationship) is not limited to this. For example, the number of light-receiving elements may be N times the number of light-emitting elements (e.g., n rows x n columns), and each light-emitting element may be associated with N (e.g., n rows x n columns) light-receiving elements (N and n are integers equal to or greater than 1).

[0064] The row numbers of the light-emitting element array 111 are assigned in ascending order from smaller to larger Yv in Fig. 11A, and the row numbers of the light-receiving element array 121 are assigned in ascending order from smaller to larger Y in Fig. 11A. The light-emitting elements and light-receiving elements with the same row number have a conjugate relationship with each other.

[0065] 11B is a schematic diagram showing the optical path of light emitted from the light-emitting element in row number 1 in the light-emitting element array 111. Light 1110 emitted from the light-emitting element array 111 is split into light 1111 that is reflected by the half mirror 151 and irradiated onto an object, and light 1112 that is transmitted through the half mirror 151 and heads toward the reflecting surface 152.

[0066] FIG. 11C is a schematic diagram showing reflected light (reference light) 1113 obtained when light 1112 is reflected by the reflecting surface 152, and FIG. 11D is a schematic diagram showing reflected light (object-reflected light) 1114 obtained when light 1111 is reflected by an object. The object-reflected light 1114 is incident on a light-receiving element that is conjugate with the light-emitting element in row number 1 that emitted the light 1110. On the other hand, the reference light 1113 is incident on a light-receiving element that is conjugate with a light-emitting element in a row different from the light-emitting element in row number 1. In the first embodiment, as an example, the reference light is incident on a light-receiving element that is conjugate with a light-emitting element that is adjacent in the column direction to the light-emitting element that emitted the light. Therefore, in FIG. 11C, the reference light 1113 is incident on a light-receiving element that is conjugate with the light-emitting element in row number 2.

[0067] The reflecting surface 152 transmits, absorbs, or both transmits and absorbs light within a certain wavelength range so as to reduce the reflectance of the wavelength of the light emitted from the light-emitting element array 111. For example, the reflecting surface 152 may be formed of a multilayer film including dielectric layers with different refractive indices, or may include an absorbing material such as a metal.

[0068] The multiple light-emitting elements (and multiple light-receiving elements) are arranged at equal intervals. The reflecting surface 152 faces the light-emitting element array 111, is flat in the column direction (depth direction of the page), and has multiple continuous recesses in the row direction (Yv direction), each with a width twice the spacing between the multiple light-emitting elements. In FIGS. 11A to 11D, the recesses are formed by two flat surfaces, but this is not limited to this. For example, the recesses may be formed by curved surfaces. The recesses may have a shape similar to the curved surface of a cylindrical lens. By using the reflecting surface 152 having such a shape and arrangement, the reference light 1113 enters the half mirror 151 at a position shifted by one row relative to the light 1110 emitted from the light-emitting element, and enters the light-receiving element that is conjugate with the light-emitting element adjacent to the light-emitting element that emitted the light.

[0069] Although details will be described later, in the first embodiment, a reference light signal is subtracted from the object-reflected light signal obtained by the TDC array 122. The object-reflected light signal indicates the time from when the light emission signal is emitted until the object-reflected light is detected, and the reference light signal indicates the time from when the light emission signal is emitted until the reference light is detected. Both the object-reflected light signal and the reference light signal contain a component of the time from when the light emission signal is emitted until the light-emitting element emits light. Therefore, by subtracting the reference light signal from the object-reflected light signal, a time of flight (TOF) having a small component of the time from when the light emission signal is emitted until the light-emitting element emits light can be obtained.

[0070] Although the case where the light emitting element in row number 1 emits light has been described, the same applies when the light emitting element in another row number emits light.

[0071] [Distance Measurement Operation] Fig. 12 is a flowchart showing an example of distance measurement operation according to the first embodiment. The distance measurement operation for acquiring three-dimensional distance information will be described with reference to Fig. 12. The distance measurement operation in Fig. 12 is realized, for example, by the CPU of the overall control unit 140 loading a program stored in the ROM of the overall control unit 140 into the RAM of the overall control unit 140 and executing the program. For example, when an instruction to perform distance measurement is given to the distance measurement device, the distance measurement operation in Fig. 12 starts.

[0072] In step S1201, the overall control unit 140 sets the value of the row counter j to 1 (resets the row counter j).

[0073] In step S1202, the overall control unit 140 controls the row selection circuit 125 to select the row (row number j) corresponding to row counter j. This causes the signals of the pixels in row number j and the pixels in row number j+1 to be output to the TDC array 122 via pixel output lines 304. The pixels in row number j receive object-reflected light that is emitted from row number j and reflected by an object. The pixels in row number j+1 receive reference light that is emitted from row number j and reflected by the reflecting surface 152 of the beam splitter 150.

[0074] In step S1203, the overall control unit 140 resets the histogram circuits, the number of which is the same as the number of TDCs 501, arranged in the signal processing unit 123, and resets the light emission count counter i. Resetting the histogram circuits sets a state in which no light detection histogram showing the change over time in the number of detected photons is present (is not created), and resetting the light emission count counter i sets the light emission count counter i to 1.

[0075] In step S1204, the overall control unit 140 operates the light-emitting element row drive circuit 202 of the row (row number j) corresponding to the row counter j to cause the light-emitting elements belonging to that row to emit short pulses of light. The overall control unit 140 sends a light-emitting signal to the light-emitting unit 110 and simultaneously instructs the measurement unit 120 to start measurement.

[0076] In step S1205, the overall control unit 140 determines whether a predetermined time Tmax (a pre-set time) has elapsed since the emission of the light emission signal. If the predetermined time Tmax has elapsed, the process proceeds to step S1209; otherwise, the process proceeds to step S1206. The predetermined time Tmax is the time corresponding to the longest distance measurement distance.

[0077] In step S1206, the overall control unit 140 determines whether the output signal of the pixel in the row corresponding to row counter j (the pixel with row number j or j+1) is 1. If the pixel output signal is 1, the process proceeds to step S1207; otherwise, the process proceeds to step S1205.

[0078] In step S1207, the overall control unit 140 controls the TDC 501 connected to the pixel that detected the pixel output signal "1" in step S1206, and measures the time from when the light emission signal is emitted to when the pixel output signal "1" is detected in step S1206.

[0079] In step S1208, the overall control unit 140 controls the histogram circuit connected to the TDC used in step S1207 to update the light detection histogram of the histogram circuit. By updating the light detection histogram, for example, the frequency of the category corresponding to the time measured in step S1207 increases by 1. Then, the process proceeds to step S1205.

[0080] The processes of steps S1204 to S1208 (the process of step S1216) are performed individually for each combination of light receiving element, TDC, and histogram circuit.

[0081] In step S1209, the overall control unit 140 increments the value of the light emission number counter i by one.

[0082] In step S1210, the overall control unit 140 checks whether the value of the light emission counter i is equal to the predetermined number of light emissions N ｔｏｔａｌ It is determined whether the value of the light emission counter i is greater than or equal to the number of light emissions N (preset number of light emissions). ｔｏｔａｌ If it is greater than , the process proceeds to step S1211; if not, the process proceeds to step S1204.

[0083] In step S1211, the overall control unit 140 performs histogram processing using the obtained light detection histogram to calculate distance measurement results such as distance measurement distance, signal intensity, and ambient light intensity.

[0084] In step S1212, the overall control unit 140 subtracts the reference light signal obtained using the pixels in row number j+1 from the object-reflected light signal obtained using the pixels in row number j.

[0085] In step S1213, the overall control unit 140 acquires the distance measurement results obtained in steps S1211 and S1212 from the measurement unit 120.

[0086] Through the processing of steps S1202 to S1213, distance measurement for one line is completed.

[0087] In step S1214, the overall control unit 140 increments the value of the row counter j by one.

[0088] In step S1215, overall control unit 140 determines whether the value of row counter j is greater than the number of rows Nrow of light-emitting elements and light-receiving elements (Nrow=8 in the cases of FIGS. 11A to 11D). If the value of row counter j is greater than the number of rows Nrow, the distance measurement operation ends; if not, the process proceeds to step S1204.

[0089] By the above-described distance measurement operation, distance measurement results can be obtained in a two-dimensional array form like image information.

[0090] Here, the subtraction process in step S1212 will be described. FIG. 13 is a schematic diagram showing a reference light histogram 1301, which is a light detection histogram obtained from the reference light, and an object-reflected light histogram 1302, which is a light detection histogram obtained from the object-reflected light. Timing 1303 is the timing (time) at which an emission signal is emitted from the overall control unit 140. From the peak of the reference light histogram 1301, a reference light peak time 1304, which is the time from when the emission signal is emitted to when the reference light is detected, is obtained. Since the time from when the light-emitting element emits light to when the reference light is detected is considered to be very short, the reference light peak time 1304 may be interpreted as the time from when the emission signal is emitted to when the reference light is emitted. Furthermore, from the peak of the object-reflected light histogram 1302, an object-reflected light peak time 1305, which is the time from when the emission signal is emitted to when the object-reflected light is detected, is obtained. The reference light peak time 1304 is subtracted from the object-reflected light peak time 1305 obtained in this manner. By doing so, it is possible to obtain a time of flight TOF that is free from the influence of individual variations and temperature characteristics of the light-emitting element driving unit 112, the light-emitting element, the light-receiving element, the TDC array 122, the buffer used for signal transmission, etc.

[0091] As described above, according to the first embodiment, a beam splitter having a half mirror and a reflective surface is used. Light emitted from a light-emitting element is split into two beams by the half mirror, one of which is detected as object-reflected light reflected by an object, and the other is detected as reference light reflected by the reflective surface of the beam splitter. The time until the reference light is detected (incident on the light-receiving element) is subtracted from the time until the object-reflected light is detected (incident on the light-receiving element). This enables highly accurate distance measurement. Furthermore, since the optical system for receiving the object-reflected light and the optical system for receiving the reference light are the same, a compact distance measuring device can be provided.

[0092] <Modification of First Embodiment> A modification of the first embodiment will be described. In the first embodiment, the reference light signal and the object reflected light signal are outputted for a set number of times N ｔｏｔａｌ The distance is calculated by subtracting the reference light signal from the object-reflected light signal for each light emission and then performing histogram processing using the subtraction result. In the following, the same parts as in the first embodiment will be omitted, and the differences from the first embodiment will be mainly described.

[0093] 14 is a flowchart showing an example of distance measurement operation according to this modification. As in the first embodiment, the processes of steps S1201 to S1207 are performed.

[0094] In step S1408, the overall control unit 140 stores the time obtained in step S1207 in the RAM (primary memory) of the overall control unit 140.

[0095] The processes of steps S1204 to S1207 and S1408 (the process of step S1416) are performed individually for each combination of light receiving element, TDC, and histogram circuit.

[0096] If the overall control unit 140 determines in step S1205 that the predetermined time Tmax has elapsed, the process proceeds to step S1412. In step S1412, the overall control unit 140 reads from RAM the object-reflected light signal obtained using the pixels of row number j and the reference light signal obtained using the pixels of row number j+1, and subtracts the read reference light signal from the read object-reflected light signal. The overall control unit 140 then reflects the subtraction results in the light detection histogram. Here, for example, multiple combinations of the object-reflected light signal and the reference light signal are read, and multiple subtraction results obtained from each of the multiple combinations are reflected in the light detection histogram. The process of reflecting the subtraction results in the light detection histogram is, for example, a process of increasing by 1 the frequency of the category corresponding to the time obtained by the subtraction.

[0097] Thereafter, the processes of steps S1209 to S1211 and S1213 to S1215 described in the first embodiment are carried out.

[0098] According to this modification, it is possible to obtain the same effects as in embodiment 1. Furthermore, since subtraction processing is performed for each light emission, it is possible to obtain highly accurate results as measurement results for each light emission.

[0099] <Embodiment 2> A description will be given of embodiment 2 of the present invention. In embodiment 1, the reference light is incident on a light-receiving element that is conjugate with the light-emitting element that is adjacent in the column direction to the light-emitting element that emitted the light. In embodiment 2, both the object-reflected light and the reference light are incident on a light-receiving element that is conjugate with the light-emitting element that emitted the light that is the source of the light. In other words, the object-reflected light and the reference light are incident on the same light-receiving element (pixel). In the following, a description of the same parts as embodiment 1 will be omitted, and the differences from embodiment 1 will be mainly described.

[0100] FIG. 15A is a schematic diagram showing cross sections of the beam splitter 150, the light-emitting element array 111, the light-receiving element array 121, and the imaging lens 130.

[0101] 15B is a schematic diagram showing the optical path of light emitted from a light-emitting element in row number 1 in the light-emitting element array 111. Light 1510 emitted from the light-emitting element is split into light 1511 that is reflected by the half mirror 151 and irradiated onto an object, and light 1512 that passes through the half mirror 151 and heads toward the reflecting surface 152.

[0102] 15C is a schematic diagram showing reflected light (reference light) 1513 obtained when light 1512 is reflected by reflecting surface 152, and FIG. 15D is a schematic diagram showing reflected light (object-reflected light) 1514 obtained when light 1511 is reflected by an object. Object-reflected light 1514 is incident on a light-receiving element that is conjugate with the light-emitting element in row number 1 that emitted light 1510. Since reflecting surface 152 is flat, reference light 1113 also enters a light-receiving element that is conjugate with the light-emitting element in row number 1.

[0103] Although the case where the light emitting element in row number 1 emits light has been described, the same applies when the light emitting element in another row number emits light.

[0104] The flowchart of the distance measurement operation according to the second embodiment is the same as that of the first embodiment (FIG. 12). However, in step S1202, only the signal of the pixel with row number j is set to be output to the TDC array 122 via the pixel output line 304.

[0105] FIG. 16 is a diagram schematically illustrating a light detection histogram obtained from a pixel conjugate with the light-emitting pixel that emitted light. Timing 1603 is the timing (time) at which an emission signal is emitted from the overall control unit 140. The light detection histogram in FIG. 16 shows two peaks 1601 and 1602. The earlier peak 1601 is a reference light peak indicating the timing at which the reference light is detected, and the later peak 1602 is an object-reflected light peak indicating the timing at which the object-reflected light is detected. From the reference light peak 1601, a reference light peak time 1604 is obtained, which is the time from when the emission signal is emitted to when the reference light is detected. Furthermore, from the object-reflected light peak 1602, an object-reflected light peak time 1605 is obtained, which is the time from when the emission signal is emitted to when the object-reflected light is detected. The reference light peak time 1604 is subtracted from the object-reflected light peak time 1605 obtained in this manner. By doing so, as in embodiment 1, it is possible to obtain a time of flight TOF in which the effects of individual variations and temperature characteristics of the light-emitting element driving unit 112, light-emitting element, light-receiving element, TDC array 122, buffers used for signal transmission, etc. are eliminated.

[0106] <Modification of Embodiment 2> A modification of Embodiment 2 will be described. In this modification, as in Embodiment 2, the object-reflected light and the reference light are incident on the same light-receiving element (pixel). Also, as in the modification of Embodiment 1, the distance is obtained by subtracting the object-reflected light signal from the object-reflected light signal for each light emission, and performing histogram processing using the subtraction result. Below, a description of the same parts as in Embodiment 2 will be omitted, and the description will focus on the differences from Embodiment 2.

[0107] The ranging operation according to this modification is similar to the ranging operation according to the modification of embodiment 1 ( FIG. 14 ). However, in step S1202, similar to embodiment 2, only the signal of the pixel with row number j is set to be output to the TDC array 122 via the pixel output line 304. Also, in step S1412, the shortest time of the multiple times stored in the RAM in step S1408 is used as the reference light signal, and the others are used as the object-reflected light signal.

[0108] According to this modification, it is possible to obtain the same effects as in embodiment 2. Furthermore, as in the modification of embodiment 1, since subtraction processing is performed for each light emission, it is possible to obtain highly accurate results as measurement results for each light emission.

[0109] <Embodiment 3> Embodiment 3 of the present invention will be described. In Embodiments 1 and 2, the number of SPAD elements (light-receiving elements) included in one pixel (light-receiving pixel) is one. In Embodiment 3, one pixel includes multiple SPAD elements. Below, a description of the same parts as in Embodiments 1 and 2 will be omitted, and the description will focus on the differences from Embodiment 1.

[0110] FIG. 17 is a schematic diagram showing an example of the configuration of a pixel 1701 according to the third embodiment. The pixel 1701 is composed of four sub-pixels 1721 to 1724. Each of the sub-pixels 1721 to 1724 has a configuration similar to that of the pixel 301 according to the first embodiment. In the third embodiment, as in the second embodiment, it is assumed that reference light and object-reflected light, which are generated by light emitted from the same light-emitting element, enter the same pixel. In other words, the reference light and object-reflected light, which are generated by light emitted from the same light-emitting element, enter the sub-pixels 1721 to 1724, respectively. The same row selection line 303 is connected to the sub-pixels 1721 to 1724, and pixel output lines 1731 to 1734 are connected to the sub-pixels 1721 to 1724, respectively. Although not shown, the TDC array 122 includes the same number of TDCs 501 as the pixel output lines so that the output signals of each sub-pixel can be processed simultaneously.

[0111] In the third embodiment, the mode of the SPADs 1711 to 1714 is switched between avalanche mode and non-avalanche mode by a switch (not shown). In the avalanche mode, the voltages of the anode electrodes Vbd1 to Vbd4 are set so that the reverse bias voltage applied to the SPADs 1711 to 1714 is equal to or greater than the breakdown voltage. In the non-avalanche mode, the voltages of the anode electrodes Vbd1 to Vbd4 are set so that the reverse bias voltage applied to the SPADs 1711 to 1714 is less than the breakdown voltage. In the avalanche mode, the arrival of photons can be detected, but after photon detection, the arrival of photons cannot be detected during the build-up operation and the quench operation.

[0112] Due to the occurrence of dead time during which the arrival of photons cannot be detected, the method of embodiment 2 cannot detect objects that exist very close to the distance measuring device. Therefore, in embodiment 3, the overall control unit 140 functions as a light receiving control unit that drives some of the multiple subpixels included in a pixel at a timing different from that of the rest of the multiple subpixels. This makes it possible to realize an operation in which some of the subpixels detect reference light and the remaining subpixels detect object-reflected light, thereby enabling high-precision distance measurement even for objects that exist very close to the distance measuring device.

[0113] In the third embodiment, the modes of the SPADs 1711 to 1714 are switched by controlling the voltages of the anode electrodes Vbd1 to Vbd4, but the mode switching method is not limited to this. Also, the number of sub-pixels included in one pixel may be more or less than four.

[0114] FIG. 18 is a schematic diagram illustrating an example of a distance measurement operation according to the third embodiment. FIG. 18 shows the mode switching timing and dead time of the SPADs 1711 to 1714, as well as a light detection histogram obtained from pixels (sub-pixels 1721 to 1724) that are conjugate with the light-emitting pixel that emitted light. The switches φVbd1 to φVbd4 switch the modes of the SPADs 1711 to 1714, with the upper side representing ON (avalanche mode voltage) and the lower side representing OFF (non-avalanche mode voltage). In the figure, "non-avalanche" indicates the period in non-avalanche mode, and "dead time" indicates the period during which the arrival of photons cannot be detected due to the build-up operation and quench operation. Timing 1803 is the timing (time) at which a light emission signal is issued from the overall control unit 140.

[0115] The overall control unit 140 controls the switches φVbd1 to φVbd4 so as to realize, for example, the following operations. At timing 1803, only SPAD1711 is in the avalanche mode, and SPADs 1712 to 1714 are in the non-avalanche mode. Thereafter, SPADs 1712 to 1714 sequentially enter the avalanche mode at predetermined time intervals. The number of light emission times N is set so that the reference light is detected by half of the sub-pixels and the object reflected light is detected by the remaining half of the sub-pixels. ｔｏｔａｌ During the measurement of minutes, the timing of switching the mode of each SPAD may be changed based on the detection results of the reference light and the light reflected from the object. The timing of switching from the non-avalanche mode to the avalanche mode may be interpreted as the timing of driving the SPAD (light receiving element).

[0116] The light detection histogram in FIG. 18 is a histogram obtained by adding up the signals obtained from the SPADs 1711 to 1714. As in the second embodiment, the light detection histogram in FIG. 18 shows a reference light peak 1801 and an object-reflected light peak 1802. In the third embodiment, the multiple SPADs in one pixel are controlled with a phase difference so that the multiple SPADs enter avalanche mode at different times, thereby preventing all of the multiple SPADs from entering a dead time state due to reception of the reference light. Therefore, the object-reflected light peak 1802 can be obtained even for objects closer than the distance corresponding to the dead time of the SPADs.

[0117] From the reference light peak 1801, a reference light peak time 1804, which is the time from when the light emission signal is emitted until the reference light is detected, is obtained. Furthermore, from the object reflected light peak 1802, an object reflected light peak time 1805, which is the time from when the light emission signal is emitted until the object reflected light is detected, is obtained. The reference light peak time 1804 is subtracted from the object reflected light peak time 1805 obtained in this manner. By doing so, as in the first and second embodiments, a time of flight TOF can be obtained in which the influences of individual variations and temperature characteristics of the light-emitting element driving unit 112, the light-emitting element, the light-receiving element, the TDC array 122, the buffer used for signal transmission, etc. are eliminated. Furthermore, this effect can be obtained even when the distance from the ranging device to the object is shorter than the distance corresponding to the dead time of the SPAD.

[0118] <Modification of Embodiment 3> A modification of Embodiment 3 will be described. In this modification, similar to the modifications of Embodiment 1 and Embodiment 2, the distance is obtained by subtracting the reference light signal from the object-reflected light signal for each light emission and performing histogram processing using the subtraction result. Below, a description of the same parts as in Embodiment 3 will be omitted, and the description will focus on the differences from Embodiment 3.

[0119] The ranging operation according to this modification is similar to the ranging operation according to the modification of embodiment 2 ( FIG. 14 ). In step S1202, similar to embodiment 2, a setting is made so that only the signal of the pixel with row number j is output to the TDC array 122 via the pixel output line 304. In step S1412, the shortest time among the multiple times stored in RAM in step S1408 is used as the reference light signal, and the others are used as the object-reflected light signal.

[0120] According to this modification, it is possible to obtain the same effects as in embodiment 3. Furthermore, as in the modification of embodiment 1 and the modification of embodiment 2, since subtraction processing is performed for each light emission, it is possible to obtain highly accurate results as measurement results for each light emission.

[0121] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various forms within the scope of the gist of the present invention are also included in the present invention. Furthermore, each of the above-described embodiments merely represents one embodiment of the present invention, and each embodiment can be combined as appropriate.

[0122] The disclosure of this embodiment includes the following configuration: (Configuration 1) A distance measuring device comprising: a light-emitting element array including a plurality of light-emitting elements; a light-receiving element array including a plurality of light-receiving elements; a timing unit that measures time; a beam splitter having a half mirror and a reflecting surface; and a distance measuring unit that measures a distance to an object based on the time measured by the timing unit, wherein light emitted from the light-emitting elements is split into first light and second light by the half mirror, the first light is reflected by the object and incident on one of the plurality of light-receiving elements, and the second light is reflected by the reflecting surface and incident on one of the plurality of light-receiving elements, and the distance measuring unit measures the distance to the object based on a time obtained by subtracting a time taken for the second light to be reflected on the reflecting surface and incident on one of the plurality of light-receiving elements from a time taken for the first light to be reflected by the object and incident on one of the plurality of light-receiving elements. (Configuration 2) The distance measuring device according to Configuration 1, wherein the plurality of light-emitting elements are arranged in a matrix, and the distance measuring device further includes a light-emitting control unit that individually controls the light-emitting elements in each row to emit light, the plurality of light-emitting elements are conjugate with the plurality of light-receiving elements via the half mirror, the first light and the second light are light obtained by splitting light emitted from the light-emitting elements in the first row by the half mirror, the first light is reflected by the object and incident on light-receiving elements that are conjugate with the light-emitting elements in the first row, and the second light is reflected by the reflecting surface and incident on light-receiving elements that are conjugate with the light-emitting elements in a second row different from the first row. (Configuration 3) The distance measuring device according to Configuration 2, wherein the second row is a row adjacent to the first row. (Configuration 4) The distance measuring device according to Configuration 2 or 3, wherein the plurality of light-emitting elements are arranged at equal intervals, and the reflecting surface faces the light-emitting element array, is flat in the column direction, and has a plurality of continuous recesses in the row direction, each having a width twice the interval between the plurality of light-emitting elements. (Configuration 5) The distance measuring device according to Configuration 4, wherein the recesses are formed by two flat surfaces.(Configuration 6) The distance measuring device according to Configuration 4, wherein the recess is formed by a curved surface. (Configuration 7) The distance measuring device according to any one of Configurations 1 to 6, wherein the plurality of light-emitting elements are arranged in a matrix, the plurality of light-emitting elements are in a conjugate relationship with the plurality of light-receiving elements via the half mirror, and the first light and the second light are incident on light-receiving elements that are in a conjugate relationship with the light-emitting elements that emitted the light that is the source of the first light and the second light. (Configuration 8) The distance measuring device according to any one of Configurations 1 to 7, wherein the reflecting surface is formed by a multilayer film. (Configuration 9) The distance measuring device according to any one of Configurations 1 to 8, wherein the reflecting surface includes an absorber that absorbs light in a partial wavelength range of the light emitted from the light-emitting element array. (Configuration 10) The distance measuring device according to any one of configurations 1 to 9, wherein the plurality of light receiving elements form a plurality of light receiving pixels each including two or more light receiving elements, the second light is reflected by the reflecting surface and enters one of the plurality of light receiving pixels, and the distance measuring device further comprises a light receiving control unit that drives some of the two or more light receiving elements included in the light receiving pixel at a timing different from that of the rest of the two or more light receiving elements. (Configuration 11) The distance measuring device according to configuration 10, wherein the light receiving elements are avalanche diodes. (Configuration 12) The distance measuring device according to configuration 10 or 11, wherein the light receiving control unit changes the timing at which each light receiving element is driven based on a detection result of the first light and the second light in the light receiving element array.

[0123] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0124] This application claims priority based on Japanese Patent Application No. 2024-059338, filed April 2, 2024, the entire contents of which are incorporated herein by reference.

[0125] 111: Light emitting element array 121: Light receiving element array 122: TDC array 123: Signal processing unit 140: Overall control unit 150: Beam splitter

Claims

1. A distance measuring device comprising: a light-emitting element array including a plurality of light-emitting elements; a light-receiving element array including a plurality of light-receiving elements; a timing unit that measures time; a beam splitter having a half mirror and a reflective surface; and a distance measuring unit that measures the distance to an object based on the time measured by the timing unit, wherein light emitted from the light-emitting elements is split into a first light and a second light by the half mirror, the first light is reflected by the object and incident on one of the plurality of light-receiving elements, and the second light is reflected by the reflective surface and incident on one of the plurality of light-receiving elements, and the distance measuring unit measures the distance to the object based on the time obtained by subtracting the time taken for the second light to be reflected on the reflective surface and incident on one of the plurality of light-receiving elements from the time taken for the first light to be reflected by the object and incident on one of the plurality of light-receiving elements.

2. The distance measuring device of claim 1, characterized in that the multiple light-emitting elements are arranged in a matrix, the distance measuring device further has a light-emitting control unit that causes the light-emitting elements in each row to emit light individually, the multiple light-emitting elements are each in a conjugate relationship with the multiple light-receiving elements via the half mirror, the first light and the second light are light obtained by splitting light emitted from the light-emitting elements in the first row using the half mirror, the first light is reflected by the object and enters a light-receiving element that is in a conjugate relationship with the light-emitting elements in the first row, and the second light is reflected by the reflective surface and enters a light-receiving element that is in a conjugate relationship with the light-emitting elements in a second row different from the first row.

3. The distance measuring device according to claim 2, wherein the second row is a row adjacent to the first row.

4. A distance measuring device as described in claim 2, characterized in that the plurality of light-emitting elements are arranged at equal intervals, the reflecting surface faces the light-emitting element array, is flat in the column direction, and has a plurality of continuous recesses in the row direction, each having a width twice the spacing between the plurality of light-emitting elements.

5. The distance measuring device according to claim 4, wherein the recess is formed by two flat surfaces.

6. The distance measuring device according to claim 4, wherein the recess is formed by a curved surface.

7. A distance measuring device according to any one of claims 1 to 6, characterized in that the plurality of light-emitting elements are arranged in a matrix, the plurality of light-emitting elements are in a conjugate relationship with the plurality of light-receiving elements via the half mirror, and the first light and the second light are incident on light-receiving elements that are in a conjugate relationship with the light-emitting elements that emitted the light that is the source of those lights.

8. A distance measuring device according to any one of claims 1 to 6, characterized in that the reflecting surface is formed of a multi-layer film.

9. A distance measuring device according to any one of claims 1 to 6, characterized in that the reflecting surface includes an absorbent material that absorbs light within a certain wavelength range of the light emitted from the light emitting element array.

10. The distance measuring device described in any one of claims 1 to 6, characterized in that the plurality of light receiving elements form a plurality of light receiving pixels each including two or more light receiving elements, the second light is reflected by the reflecting surface and enters one of the plurality of light receiving pixels, and the distance measuring device further has a light receiving control unit that drives some of the two or more light receiving elements included in the light receiving pixel at a timing different from that of the rest of the two or more light receiving elements.

11. The distance measuring device according to claim 10, wherein the light receiving element is an avalanche diode.

12. The distance measuring device according to claim 10, characterized in that the light receiving control unit changes the timing for driving each light receiving element based on the detection results of the first light and the second light in the light receiving element array.

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