WO2025211035A1 - Ranging device - Google Patents

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

The present invention relates to a distance measuring device.

A known distance measurement method is the TOF (Time-Of-Flight) method, which measures the distance to an object by measuring the time between when a light-emitting element emits light and when the reflected light is detected.

Patent Document 1 discloses a configuration in which multiple light-emitting elements and multiple light-receiving elements are arranged in a two-dimensional array, light is irradiated onto an object via an imaging lens, and the reflected light is received via the imaging lens, thereby obtaining three-dimensional distance information without a drive unit. In such a configuration, the angle of view of the light emitted and the angle of view of the light received must be roughly equal. Furthermore, in order to miniaturize 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 roughly equal and to use a common imaging lens for the light-emitting element array and the light-receiving element array.

Patent document 2 discloses a configuration that improves distance measurement accuracy by calculating the time difference between a reference light corresponding to the laser emission timing and the light reflected by an object.

JP 2019-60652 A JP 2014-174069 A

However, the configuration disclosed in Patent Document 2 requires the provision of an optical system for receiving the reference light in addition to the optical system for receiving the reflected light, which results in an increase in the size of the distance measuring device.

The object of the present invention is to provide a compact distance measuring device capable of highly accurate distance measurement.

The distance measuring device of the present invention comprises 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 timer for measuring time, a beam splitter having a half mirror and a reflecting surface, and a distance measuring unit for measuring the distance to an object based on the time measured by the timer, wherein light emitted from the light-emitting element 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 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 the time obtained by subtracting the time taken for the second light to be reflected by the reflecting 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.

The present invention makes it possible to provide a compact distance measuring device capable of highly accurate distance measurement.

FIG. 1 is a block diagram of a distance measuring device. FIG. 2 is a block diagram of the light emitting unit. FIG. 3 is a block diagram of the 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 the time variations of the output signal of the buffer and the internal signal of the oscillator. FIG. 8 is a timing chart showing the process up to the end of the counting operation of the TDC. FIG. 9 is an enlarged view of a part of FIG. FIG. 10 is a block diagram of the oscillation adjustment circuit. 11A to 11D are cross-sectional views of the beam splitter according to the first embodiment. FIG. 12 is a flowchart of a distance measurement 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 measurement operation according to a modification of the first embodiment. 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.

<Embodiment 1>
A first embodiment of the present invention will be described.

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

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

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 multiple 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 embodiment 1, multiple light-emitting elements are arranged in a two-dimensional array (matrix), and the light source control unit 114 (light-emitting control unit) causes each row of light-emitting elements to emit light individually.

The measurement unit 120 has 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 embodiment 1, 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 will 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 placed on the light receiving element array 121.

Beam splitter 150 has a half mirror 151 that transmits part of the light and reflects part of it, and a reflective surface 152 that reflects the light.

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 part of the distance measuring device by expanding a program stored in the ROM into the RAM and executing it. At least a portion of the overall control unit 140 may be realized by a dedicated hardware circuit.

When each light-emitting element emits a pulse of light, it is output into space via the imaging lens 130. The pulse of light emitted from different light-emitting elements is output to different angles of view (ranges) in space. A portion of the output light (illumination light) is reflected by the object and enters the light-receiving element array 121 via the imaging lens 130 as reflected light. The time from when the light-emitting element emits illumination 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.

However, with 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 when the light emission signal (the drive signal for emitting light from the light-emitting element) is emitted and when the light-emitting element actually emits light have a significant impact on the measurement results. In other words, with 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 based on the histogram (for example, averaging the results of the multiple measurements).

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, light emitting element, light receiving element, TDC array 122, buffer used for signal transmission, etc. Therefore, as will be described in detail below, 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. By doing this, it is possible to obtain a time of flight TOF that has a small component of the time from when the light emission signal is emitted until the light emitting element emits light.

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)

[Lighting unit]
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.

The light-emitting element array 111 has a configuration in which multiple 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 multiple light-emitting element row drive circuits 202 are arranged one-dimensionally (in one column). The multiple light-emitting element row drive circuits 202 correspond to the multiple rows of the multiple light-emitting elements 201, respectively. Each light-emitting element row drive circuit 202 drives the light-emitting elements 201 in the corresponding row.

Note that 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 a one-dimensional array of elements, 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.

Furthermore, while there are no particular limitations on the wavelength of the light emitted by the light-emitting element 201, a wavelength in the near-infrared band can suppress the effects of ambient light. VCSELs can be manufactured using semiconductor processes from materials used in edge-emitting lasers and surface-emitting lasers. If GaAs-based semiconductor materials are used as the main material, a VCSEL that emits light with a wavelength in the near-infrared band can be manufactured. In this case, the dielectric multilayer film that forms the DBR (distributed Bragg reflector) reflector that makes up the VCSEL can be constructed from two thin films made of materials with different refractive indices that are alternately and periodically stacked (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.

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 the active layer. An electrode is provided for each row of multiple light-emitting elements 201, and is shared between the VCSELs in the same row. The multiple electrodes are respectively connected to multiple light-emitting element row drive circuits 202. 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.

[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 light-receiving element array 121, a TDC 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 a plurality of pixels 301 arranged in a two-dimensional array. Each pixel includes a light-receiving element. The row selection circuit 125 is connected to the plurality of pixels 301 of the light-receiving element 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).

Figure 4 is a schematic diagram showing an example 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 the row selection line 303 and pixel output line 304. The SPAD element 401 is a type of avalanche diode, and has a light-receiving region and an avalanche region.

When light is incident on the SPAD element 401, photoelectric conversion occurs in the light-receiving region, generating electrons and holes. Positively charged holes are discharged via the anode electrode Vbd. Negatively charged electrons are transported to the avalanche region as signal charge by an electric field set so that the potential decreases toward the avalanche region. The signal charge that reaches the avalanche region causes avalanche breakdown due to the strong electric field in the avalanche region, generating an avalanche current.

When no avalanche current is flowing, 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."

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. In other words, the inverter output changes from "0" to "1." Hereafter, this operation is referred to as the build-up operation.

When the cathode potential Vc decreases, the reverse bias applied to the SPAD element 401 decreases, and when the reverse bias falls below the breakdown voltage, the generation of avalanche current stops. Hereafter, this operation is referred to as the quench operation.

After that, 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 it was in before the photon arrived. Hereafter, this operation is referred to as the recharge operation.

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

In this way, it is possible to detect only the light incident on the pixels 301 (SPAD elements 401) in the row selected by the row selection circuit 125.

[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.

Figure 5 is a block diagram showing an example configuration of the TDC array 122. The TDC array 122 has twice the number of pixels 301 in one row (the number of columns of multiple pixels 301) in TDCs 501 and can receive output signals from two rows of pixels 301. The output signals from the pixels 301 in one row are used to detect reflected light from an object, and the output signals from the pixels 301 in the other row are used to detect reference light. In the explanation of Figure 3, we have described a case where the same number of pixel output lines 304 as the number of pixels 301 in one row are used, but in embodiment 1, twice the number of pixel output lines 304 as the number of pixels 301 in one row are used. The pixel output lines 304, which are twice 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 rows, it becomes possible for the TDC array 122 to receive output signals from pixels 301 in two rows.

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

Figure 6 is a schematic diagram of oscillator 511. Oscillator 511 has an oscillation start/stop signal generation circuit 640, buffers 611-618, an oscillation switch 630, and a delay adjustment current source 620. Buffers 611-618 are connected alternately with oscillation switch 630 in series and in a ring configuration.

Fig. 7 is a table showing the time variations of the output signals of buffers 611 to 618 and the internal signal of oscillator 511. Fig. 7 shows the output signals of buffers 611 to 618 at the time of reset and the internal signal of oscillator 511. Furthermore, Fig. 7 shows the output signals of buffers 611 to 618 and the internal signal of oscillator 511 each time the delay time t _buff for one buffer stage has elapsed since oscillation switch 630 was turned on.

At reset, the outputs of buffers 611 to 617 are "0" and the output of buffer 618 is "1". After the delay time t _buff for one buffer stage has elapsed since oscillation switch 630 was turned on, 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.

After a delay time t _buff for one buffer stage has elapsed (2×t _buff has elapsed), only the output of buffer 612, whose input and output are not matched, changes from “0” to “1” (the signal advances by another stage). The outputs of buffer 611 and buffers 613 to 618, whose input and output are matched, do not change.

In this way, each time the delay time t _buff for one buffer stage elapses, the output of one buffer with mismatched input and output changes sequentially from "0" to "1." After 8×t _buff has elapsed since the oscillation switch 630 was turned on, the outputs of all buffers change to "1" (the signal goes around once), and after 16×t _buff , all buffers change to "0" (the signal goes around twice), returning to the original state.

Thereafter, the output changes in the same manner, with 16×t _buuf being one cycle. In this way, time is measured with a time resolution of t _buff . This time resolution t _buff is adjusted by the oscillation adjustment circuit 541, which will be described later, to be ^1/27 of the synchronous clock.

The oscillator output, which is the output of the buffer 618, is input to an oscillation count circuit 521. The oscillation count circuit 521 counts the rising edges of the oscillator output to measure time with a time resolution of 16×t _buff .

Figure 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, until the SPAD element 401 receives the light, and the counting operation of the TDC 501 ends. It 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.

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

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

Using Figures 8 and 9, we will explain how the TDC 501 measures 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.

At time 801, which is synchronized with the rising edge of the synchronization clock supplied via the overall control unit 140, a light emission signal is sent from the overall control unit 140 to the light emission unit 110. The synchronization clock count circuit 531 begins counting the rising edges of the synchronization clock from time 801, when the light emission signal is sent.

At time 803, photons reflected from an object are received by the SPAD element 401 of 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," turning on the oscillation switch 630.

When the oscillation switch 630 is turned on, oscillation begins, and a signal loop begins inside the oscillator 511 as shown in Figure 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 such edges. Also, at time 803, the synchronous clock count circuit 531 stops counting and retains the count value.

Time 805 is the timing when the synchronous clock first rises after time 803 when the oscillator 511 turns 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. Also, because oscillation ends, the oscillation count circuit 521 also stops counting.

In this way, the count result D _Gclk of the synchronous clock count circuit 531 is a value obtained by measuring the time from time 801 to time 802 in units of 2 ⁷ ×t _buff . Furthermore, the count result D _ROclk of the oscillation count circuit 521 is a value obtained by measuring the time from time 803 to time 804 in units of 2 ⁴ ×t _buff . Furthermore, the oscillator internal signal D _ROin is a value obtained by measuring the time from time 804 to time 805 in units of 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.

The count result _{D_ROclk} of the oscillation count circuit 521 and the oscillator internal signal _{D_ROin} are added together according to the following equation (2).

D _RO = 2 ⁴ × D _ROclk + D _ROin (2)

D _RO obtained by equation (2) is a value obtained by measuring the time from time 803 to time 805 in units of t _buff . Furthermore, the time from time 802 to time 805 is equal to one cycle of the synchronous clock, and is therefore 2 ⁷ ×t _buff . Therefore, as shown in equation (3) below, by subtracting D _RO from one cycle of the synchronous clock and adding D _Gclk to the obtained value, the value D _ToF obtained by measuring the time of flight of light (the time from time 801 to time 803) in units of t _buff can be obtained.

D _ToF = 2 ⁷ × D _Gclk + (2 ⁷ - D _RO )
=2 ⁷ × D _Gclk + (2 ⁷ -24 × D _ROclk - D _ROin ) ... (3)

The delay time t _buff for one buffer stage varies due to factors arising from the manufacturing process such as transistor manufacturing errors, fluctuations in the voltage applied to the TDC circuit, and temperature, so an oscillation adjustment circuit 541 is provided.

10 is a block diagram showing an example of the configuration of the oscillation adjustment circuit 541. The oscillation adjustment circuit 541 has a dummy oscillator 1001, a ½ ³ (⅛) frequency divider 1002, and a phase comparator 1003. The dummy oscillator 1001 has the same configuration as the oscillator 511 mounted in the TDC 501.

The output of dummy oscillator 1001 is input to ^1/2/3 frequency divider 1002. ^1/2/3 frequency divider 1002 outputs a clock signal obtained by dividing the frequency of the input clock signal by ^2/3 . The synchronous clock and the output of ^1/2/3 frequency divider 1002 are input to phase comparator 1003. Phase comparator 1003 compares the frequency of the synchronous clock with the frequency of the clock signal output by ^1/2/3 frequency divider 1002. Phase comparator 1003 increases the output voltage when the frequency of the synchronous clock is higher, and decreases the output voltage when the frequency of the synchronous clock is lower. The output voltage of phase comparator 1003 is input as an adjustment voltage to delay adjustment current source 620 of oscillator 511, thereby adjusting the delay so that the oscillation frequency of oscillator 511 is ^2/3 times that of the synchronous clock.

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 process, voltage, or temperature, it is possible to suppress variations in the oscillation frequency of the oscillator 511 due to changes in process, voltage, or temperature. For example, by inputting a 160 MHz clock signal 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 _buff for one buffer stage, which is the time resolution of the TDC 501, is 48.8 ps.

[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.

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 multiple light-emitting elements of the light-emitting element array 111 are each in a conjugate relationship with the multiple light-receiving elements of the light-receiving element array 121 via the half mirror 151 of the beam splitter 150.

Note that in Figure 11A, the number of rows of the multiple light-emitting elements and the number of rows of the multiple light-receiving elements are both eight, but these numbers of rows are not limited to eight. Also, while the light-emitting elements and the light-receiving elements are in a 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 light-receiving elements (e.g., n rows x n columns) (N and n are integers greater than or equal to 1).

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

Figure 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 the object, and light 1112 that passes through the half mirror 151 and heads toward the reflecting surface 152.

11C is a schematic diagram showing reflected light (reference light) 1113 obtained when light 1112 is reflected by 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. 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 light 1110. On the other hand, reference light 1113 is incident on a light-receiving element that is conjugate with a light-emitting element in a different row from the light-emitting element in row number 1. In embodiment 1, 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.

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

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 in the paper), 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 Figures 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 a reflecting surface 152 with such a shape and arrangement, the reference light 1113 enters the half mirror 151 shifted by one row relative to the light 1110 emitted from the light-emitting element, and enters a light-receiving element that is conjugate with the light-emitting element adjacent to the light-emitting element that emitted the light.

As will be described in more detail below, in embodiment 1, 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, it is possible to obtain a time of flight (TOF) that contains a small component of the time from when the light emission signal is emitted until the light-emitting element emits light.

The above explanation is for the case where the light-emitting element in row number 1 emits light, but the same applies when a light-emitting element in a different row number emits light.

[Distance measurement operation]
Fig. 12 is a flowchart showing an example of a 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.

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

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 sets the signal of the pixel in row number j and the signal of the pixel in row number j+1 to be output to the TDC array 122 via the pixel output line 304. The pixel in row number j receives object-reflected light that is emitted from row number j and reflected by the object. The pixel in row number j+1 receives reference light that is emitted from row number j and reflected by the reflecting surface 152 of the beam splitter 150.

In step S1203, the overall control unit 140 resets the histogram circuits, of which the same number as the TDCs 501 are arranged within 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 (has not been created), and resetting the light emission count counter i sets it to 1.

In step S1204, the overall control unit 140 operates the light-emitting element row drive circuit 202 for the row (row number j) corresponding to row counter j, causing 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.

In step S1205, the overall control unit 140 determines whether a predetermined time Tmax (a pre-set time) has elapsed since the light emission signal was emitted. If the predetermined time Tmax has elapsed, the process proceeds to step S1209; if not, the process proceeds to step S1206. The predetermined time Tmax is the time corresponding to the longest distance measurement distance.

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," proceed to step S1207; if not, proceed to step S1205.

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 until the pixel output signal "1" is detected in step S1206.

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 that 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, proceed to step S1205.

The processing of steps S1204 to S1208 (the processing of step S1216) is performed separately for each combination of light receiving element, TDC, and histogram circuit.

In step S1209, the overall control unit 140 increments the value of the light emission count counter i by 1.

In step S1210, the overall control unit 140 determines whether the value of the light emission counter i is greater than or equal to a predetermined number of lights N _total (a number of lights set in advance). If the value of the light emission counter i is greater than the number of lights N _total , the process proceeds to step S1211; if not, the process proceeds to step S1204.

In step S1211, the overall control unit 140 uses the obtained light detection histogram to perform histogram processing to calculate ranging results such as ranging distance, signal strength, and ambient light intensity.

In step S1212, the overall control unit 140 subtracts the reference light signal obtained using the pixel with row number j+1 from the object-reflected light signal obtained using the pixel with row number j.

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

Steps S1202 to S1213 complete distance measurement for one line.

In step S1214, the overall control unit 140 increments the value of row counter j by 1.

In step S1215, the 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 case of Figures 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.

The above distance measurement operation allows for obtaining distance measurement results in a two-dimensional array similar to image information.

Here, the subtraction process in step S1212 will be explained. Figure 13 is a schematic diagram showing reference light histogram 1301, which is a light detection histogram obtained from the reference light, and 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 reference light histogram 1301, 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, reference light peak time 1304 may also be interpreted as the time from when the emission signal is emitted to when the reference light is emitted. Furthermore, 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 from the peak of object reflected light histogram 1302. Reference light peak time 1304 is subtracted from 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 driver 112, light-emitting element, light-receiving element, TDC array 122, buffers used for signal transmission, etc.

As described above, according to embodiment 1, a beam splitter having a half mirror and a reflective surface is used. Light emitted from the light-emitting element is split into two beams by the half mirror; one is detected as object-reflected light reflected by the object, and the other is detected as reference light reflected by the reflective surface of the beam splitter. The time taken for the reference light to be detected (to be incident on the light-receiving element) is then subtracted from the time taken for the object-reflected light to be detected (to be incident on the light-receiving element). This enables highly accurate distance measurement. Furthermore, because 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.

<Modification of the 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 accumulated as a histogram for a set number of times N _total of light emissions, and then subtraction processing is performed. In this modification, the reference light signal is subtracted from the object reflected light signal for each emission, and histogram processing is performed using the subtraction result to obtain the distance. Below, a description of the same parts as in the first embodiment will be omitted, and the differences from the first embodiment will be mainly described.

FIG. 14 is a flowchart showing an example of distance measurement operation according to this modified example. Similar to embodiment 1, steps S1201 to S1207 are performed.

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.

The processing of steps S1204 to S1207 and S1408 (processing of step S1416) is performed individually for each combination of light receiving element, TDC, and histogram circuit.

If the overall control unit 140 determines in step S1205 that the predetermined time Tmax has elapsed, it 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 object-reflected light signals and reference light signals 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.

Then, steps S1209 to S1211 and S1213 to S1215 described in embodiment 1 are performed.

This modified example achieves the same effects as embodiment 1. Furthermore, because subtraction processing is performed for each light emission, highly accurate results can be obtained as measurement results for each light emission.

<Embodiment 2>
A second embodiment of the present invention will now be described. In the first embodiment, 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 the second embodiment, 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 in the first embodiment will be omitted, and the differences from the first embodiment will be mainly described.

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

Figure 15B 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 1510 emitted from the light-emitting element is split into light 1511 that is reflected by the half mirror 151 and irradiated onto the object, and light 1512 that passes through the half mirror 151 and heads toward the reflecting surface 152.

Figure 15C is a schematic diagram showing reflected light (reference light) 1513 obtained when light 1512 is reflected by reflecting surface 152, and Figure 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. And, because 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.

The above explanation is for the case where the light-emitting element in row number 1 emits light, but the same applies when a light-emitting element in a different row number emits light.

The flowchart for the distance measurement operation in embodiment 2 is the same as that in embodiment 1 (Figure 12). However, in step S1202, only the signal from the pixel with row number j is set to be output to the TDC array 122 via the pixel output line 304.

Figure 16 is a schematic diagram showing a light detection histogram obtained from a pixel that is conjugate with the light-emitting pixel that emitted light. Timing 1603 is the timing (time) at which an emission signal was emitted from the overall control unit 140. The light detection histogram in Figure 16 shows two peaks 1601 and 1602. The earlier peak 1601 is a reference light peak indicating the timing at which the reference light was detected, and the later peak 1602 is an object reflected light peak indicating the timing at which the object reflected light was 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 driver 112, light-emitting element, light-receiving element, TDC array 122, buffers used for signal transmission, etc. are eliminated.

<Modification of the Second Embodiment>
A modification of the second embodiment will now be described. In this modification, similar to the second embodiment, the object-reflected light and the reference light are incident on the same light-receiving element (pixel). Also, similar to the modification of the first embodiment, 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 the second embodiment will be omitted, and the description will focus on the differences from the second embodiment.

The ranging operation according to this modified example is the same as the ranging operation according to the modified example of embodiment 1 (Figure 14). However, in step S1202, as in embodiment 2, only the signal from 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, of the multiple times stored in RAM in step S1408, the shortest time is used as the reference light signal, and the others are used as the object-reflected light signal.

This modified example provides the same effects as embodiment 2. Furthermore, as with the modified example of embodiment 1, subtraction processing is performed for each light emission, making it possible to obtain highly accurate results as measurement results for each light emission.

<Embodiment 3>
A third embodiment of the present invention will be described. In the first and second embodiments, one pixel (light-receiving pixel) includes one SPAD element (light-receiving element). In the third embodiment, one pixel includes multiple SPAD elements. Hereinafter, a description of the same parts as in the first and second embodiments will be omitted, and the description will focus on the differences from the first embodiment.

Figure 17 is a schematic diagram showing an example configuration of a pixel 1701 according to embodiment 3. The pixel 1701 consists 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 embodiment 1. In embodiment 3, as in embodiment 2, reference light and object-reflected light generated by the same light-emitting element are assumed to enter the same pixel. In other words, reference light and object-reflected light generated by the same light-emitting element are incident on each of the sub-pixels 1721 to 1724. 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.

In embodiment 3, a switch (not shown) switches the mode of SPAD1711-1714 between avalanche mode and non-avalanche mode. In avalanche mode, the voltage of anode electrodes Vbd1-Vbd4 is set so that the reverse bias voltage applied to SPAD1711-1714 is equal to or greater than the breakdown voltage. In non-avalanche mode, the voltage of anode electrodes Vbd1-Vbd4 is set so that the reverse bias voltage applied to SPAD1711-1714 is less than the breakdown voltage. In avalanche mode, the arrival of photons can be detected, but after photon detection, the arrival of photons cannot be detected during the build-up and quench operations.

Due to the occurrence of dead time during which the arrival of photons cannot be detected, the method of embodiment 2 is unable to detect objects that are 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 sub-pixels included in a pixel at a different timing than the rest of the multiple sub-pixels. This makes it possible to perform operations such as detecting reference light with some sub-pixels and detecting object-reflected light with the remaining sub-pixels, enabling highly accurate distance measurement even for objects that are very close to the distance measuring device.

In the third embodiment, the modes of SPAD1711-1714 are switched by controlling the voltages of the anode electrodes Vbd1-Vbd4, but the mode switching method is not limited to this. Furthermore, the number of sub-pixels included in one pixel may be more or less than four.

FIG. 18 is a schematic diagram showing an example of distance measurement operation according to embodiment 3. FIG. 18 shows the mode switching timing and dead time of SPADs 1711-1714, as well as a light detection histogram obtained from pixels (sub-pixels 1721-1724) that are conjugate with the light-emitting pixel that emitted light. Switches φVbd1-φVbd4 are switches that switch the mode of SPADs 1711-1714, with the upper side of the figure indicating on (avalanche mode voltage) and the lower side indicating 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 incoming photons cannot be detected due to build-up and quench operations. Timing 1803 is the timing (time) at which a light emission signal is issued from the overall control unit 140.

The overall control unit 140 controls the switches φVbd1 to φVbd4 to achieve, for example, the following operation. At timing 1803, only the SPAD 1711 is in the avalanche mode, and the SPADs 1712 to 1714 are in the non-avalanche mode. Thereafter, the SPADs 1712 to 1714 sequentially switch to the avalanche mode at predetermined time intervals. Note that the mode switching timing of each SPAD may be changed based on the detection results of the reference light and the object-reflected light during the measurement of the set number of light emissions N _total , so that the reference light is detected in half of the subpixels and the object-reflected light is detected in the remaining half of the subpixels. The timing of switching from the non-avalanche mode to the avalanche mode may also be interpreted as the timing of driving the SPAD (light-receiving element).

The light detection histogram in Figure 18 is a histogram obtained by adding up the signals obtained from the SPADs 1711 to 1714. As with embodiment 2, the light detection histogram in Figure 18 shows a reference light peak 1801 and an object reflected light peak 1802. In embodiment 3, multiple SPADs in one pixel are controlled with a phase difference so that they enter avalanche mode at different times, preventing all of the multiple SPADs from entering a dead time state due to reception of the reference light. Therefore, an object reflected light peak 1802 can be obtained even for objects closer than the distance corresponding to the dead time of the SPADs.

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 from reference light peak 1801. Furthermore, object reflected light peak time 1805, which is the time from when the light emission signal is emitted until the light reflected from the object is detected, is obtained from object reflected light peak 1802. Reference light peak time 1804 is subtracted from object reflected light peak time 1805 obtained in this manner. In this way, as in embodiments 1 and 2, a time of flight TOF can be obtained that is free from the influence of individual variations and temperature characteristics of the light-emitting element drive unit 112, light-emitting element, light-receiving element, TDC array 122, buffers used for signal transmission, etc. Furthermore, this effect can be obtained even if the distance from the ranging device to the object is shorter than the distance corresponding to the dead time of the SPAD.

<Modification of the Third Embodiment>
A modification of the third embodiment will now be described. In this modification, similar to the modifications of the first and second embodiments, 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 the third embodiment will be omitted, and the differences from the third embodiment will be mainly described.

The ranging operation according to this modified example is the same as the ranging operation according to the modified example of embodiment 2 (Figure 14). In step S1202, as in embodiment 2, only the signal from 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, of the multiple times stored in RAM in step S1408, the shortest time is used as the reference light signal, and the others are used as the object-reflected light signal.

This modified example provides the same effects as embodiment 3. Furthermore, as with the modified examples of embodiment 1 and embodiment 2, subtraction processing is performed for each light emission, making it possible to obtain highly accurate results as measurement results for each light emission.

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 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.

The disclosure of this embodiment includes the following configuration.
(Configuration 1)
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;
a distance measuring unit that measures the distance to an object based on the time measured by the timing unit,
The light emitted from the light-emitting element is separated into a first light and a second light by the half mirror,
the first light is reflected by the object and incident on any one of the plurality of light receiving elements,
the second light is reflected by the reflecting surface and incident on any one of the plurality of light receiving elements,
A ranging device characterized in that the ranging unit measures the distance to the object based on the time obtained by subtracting the time it takes for the second light to be reflected by the reflecting surface and enter one of the multiple light receiving elements from the time it takes for the first light to be reflected by the object and enter one of the multiple light receiving elements.
(Configuration 2)
The plurality of light-emitting elements are arranged in a matrix,
The distance measuring device is
a light-emission control unit that controls the light-emitting elements in each row to emit light individually;
the plurality of light-emitting elements are in a conjugate relationship 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 light-emitting elements in a first row by the half mirror,
the first light is reflected by the object and incident on a light receiving element in a conjugate relationship with the light emitting element in the first row;
2. The distance measuring device according to claim 1, wherein the second light is reflected by the reflecting surface and incident on a light receiving element that is in a conjugate relationship with a light emitting element in a second row different from the first row.
(Configuration 3)
3. The distance measuring device according to configuration 2, wherein the second row is a row adjacent to the first row.
(Configuration 4)
The plurality of light emitting elements are arranged at equal intervals,
The distance measuring device described in configuration 2 or 3, characterized in that the reflective 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.
(Configuration 5)
5. The distance measuring device according to configuration 4, wherein the recess is formed by two flat surfaces.
(Configuration 6)
5. The distance measuring device according to configuration 4, wherein the recess is formed by a curved surface.
(Configuration 7)
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,
The distance measuring device according to any one of configurations 1 to 6, wherein the first light and the second light are incident on a light receiving element that is conjugate with a light emitting element that emitted the light that is the source of the first light and the second light.
(Configuration 8)
8. The distance measuring device according to any one of configurations 1 to 7, wherein the reflecting surface is formed of a multilayer film.
(Configuration 9)
9. The distance measuring device according to any one of configurations 1 to 8, wherein the reflecting surface includes an absorbing material that absorbs light in a partial wavelength range of the light emitted from the light emitting element array.
(Configuration 10)
the plurality of light receiving elements form a plurality of light receiving pixels, each of which includes two or more light receiving elements;
the second light is reflected by the reflecting surface and incident on any one of the plurality of light-receiving pixels;
The distance measuring device is
10. The distance measuring device according to any one of configurations 1 to 9, further comprising a light receiving control unit that drives a part of 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)
11. The distance measuring device according to configuration 10, wherein the light receiving element is an avalanche diode.
(Configuration 12)
12. The distance measuring device according to configuration 10 or 11, wherein 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.

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

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.

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 (12)

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;
a distance measuring unit that measures the distance to an object based on the time measured by the timing unit,
The light emitted from the light-emitting element is separated into a first light and a second light by the half mirror,
the first light is reflected by the object and incident on any one of the plurality of light receiving elements,
the second light is reflected by the reflecting surface and incident on any one of the plurality of light receiving elements,
A ranging device characterized in that the ranging unit measures the distance to the object based on the time obtained by subtracting the time it takes for the second light to be reflected by the reflecting surface and enter one of the multiple light receiving elements from the time it takes for the first light to be reflected by the object and enter one of the multiple light receiving elements. The plurality of light-emitting elements are arranged in a matrix,
The distance measuring device is
a light-emission control unit that controls the light-emitting elements in each row to emit light individually;
the plurality of light-emitting elements are in a conjugate relationship 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 light-emitting elements in a first row by the half mirror,
the first light is reflected by the object and incident on a light receiving element in a conjugate relationship with the light emitting element in the first row;
2. The distance measuring device according to claim 1, wherein the second light is reflected by the reflecting surface and incident on a light receiving element that is in a conjugate relationship with the light emitting element 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. The plurality of light emitting elements are arranged at equal intervals,
3. The distance measuring device according to claim 2, wherein the reflecting surface faces the light-emitting element array, is flat in the column direction, and has a plurality of consecutive 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. 5. The distance measuring device according to claim 4, wherein the recess is formed by a curved surface. 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,
A distance measuring device according to any one of claims 1 to 6, characterized in that the first light and the second light are incident on a light receiving element that is conjugate with the light emitting element that emitted the original light. 7. The distance measuring device according to claim 1, wherein the reflecting surface is formed of a multi-layer film. 7. The distance measuring device according to claim 1, wherein the reflecting surface includes an absorbent material that absorbs light in a partial wavelength range of the light emitted from the light emitting element array. the plurality of light receiving elements form a plurality of light receiving pixels, each of which includes two or more light receiving elements;
the second light is reflected by the reflecting surface and incident on any one of the plurality of light-receiving pixels;
The distance measuring device is
A distance measuring device as described in any one of claims 1 to 6, characterized in that it 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 different timing than the remaining two or more light receiving elements. 11. The distance measuring device according to claim 10, wherein the light receiving element is an avalanche diode. 11. The distance measuring device according to claim 10, 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.