Optical distance measuring device and method thereof

Abstract

The optical distance measuring device (20) images reflected light corresponding to pulse light emitted from a light emitting unit (40) to a predetermined range on a pixel (66) arranged with a plurality of small pixels (69, s1 to s9) capable of performing detection respectively, and detects reflected light repeatedly performed at intervals of at least a part of the plurality of small pixels at different phases and detects reflected light repeatedly performed at intervals of other small pixels at different phases through a timing control unit (170). Using the results of the detection repeatedly performed at intervals of each small pixel, a determination unit (100) determines the spatial position of an object (OBJ1) including the distance to the object existing in the predetermined range.

Description

Technical Field

[0001] The present invention relates to a technology for detecting an object using light. Background Art

[0002] The following technology is known: irradiating pulsed light such as laser, detecting reflected light from the object in the light receiving part, measuring the return time (TOF) from irradiation to light reception, thereby detecting the presence of the object and measuring the distance to the object. In such a device, various studies have been conducted to improve the resolution of capturing the object. As resolution, there are two: the resolution when detecting the spatial position of the object (hereinafter also referred to as spatial resolution), and the resolution when measuring the return time corresponding to the distance to the object (hereinafter also referred to as time resolution). In order to improve the former, it is sufficient to reduce the size of the light-emitting element and the light-receiving element. For example, in Japanese Patent Gazette No. 2016-176721 (hereinafter referred to as Patent Document 1), the following structure is described: prepare a plurality of light-emitting elements with a light-emitting area smaller than the light-receiving area of ​​the light-receiving element, and make the plurality of light-emitting elements emit light in a time-sharing manner, so as to obtain a distance image with a resolution higher than the resolution of the light-receiving element.

[0003] However, in the technology described in the above-mentioned patent document 1, in one distance measurement, a laser diode having a small light-emitting area is caused to emit light in a time-sharing manner, so the time required for distance measurement becomes longer, resulting in a decrease in the frame rate. On the other hand, it is also possible to assume a technology that divides the interior of the light-receiving element into a plurality of small pixels and can detect each small pixel, but although the spatial resolution is improved, the temporal resolution cannot be improved in that way. Summary of the invention

[0004] The present invention can be implemented as the following modes or application examples. That is, the optical distance measuring device of the present invention uses light to measure the distance to the object, and the optical distance measuring device comprises: a light emitting unit that emits pulse light to a specified range; an optical system that images the reflected light from the specified range corresponding to the pulse light on the pixel for detection; a light receiving unit that arranges a plurality of small pixels in the pixel that can respectively detect the reflected light; a timing control unit that performs the detection of the reflected light repeatedly performed at a time interval by at least a part of the plurality of small pixels and the detection of the reflected light repeatedly performed at a time interval by other small pixels at different phases; and a determination unit that uses the results of the detection repeatedly performed at the time interval by each of the small pixels to determine the spatial position of the object including the distance to the object existing in the specified range.

[0005] According to the optical ranging device, it is possible to perform detection of reflected light repeatedly performed at time intervals by at least a part of the multiple small pixels and detection of reflected light repeatedly performed at time intervals by other small pixels with different phases. Therefore, by using the results of detection repeatedly performed at time intervals by each small pixel, in determining the spatial position of an object at a distance to an object existing in a specified range, the resolution on the time axis can be improved by the phase difference of detection between the small pixels. In addition, by using the detection results of multiple small pixels, the spatial resolution can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 is a schematic structural diagram of the optical distance measuring device of the first embodiment,

[0007] Figure 2 is an explanatory diagram showing the detailed structure of the optical system,

[0008] Figure 3 is a block diagram showing the internal structure of the SPAD operation unit.

[0009] Figure 4 is an explanatory diagram showing an example of a SPAD circuit constituting a light receiving circuit,

[0010] Figure 5 1 is an explanatory diagram showing a state in which the detection results of each SPAD circuit are superimposed to detect a peak value.

[0011] Figure 6 is a block diagram showing the detailed structure of the adding unit, the histogram generating unit, and the peak detecting unit.

[0012] Figure 7 is an explanatory diagram showing the internal structure of the timing control circuit and the timing control signals output to each adder,

[0013] Figure 8 This is an illustration of the phase difference detected at each small pixel, taking 4 small pixels as an example.

[0014] Fig. 9 is a flowchart showing the process of ranging,

[0015] Fig.10 is an explanatory diagram showing an example of a histogram generated by each histogram generator.

[0016] Fig.11 is an explanatory diagram showing other examples of histograms generated by each histogram generator.

[0017] Fig.12 is an explanatory diagram showing the internal structure of the timing control circuit in the second embodiment and the timing control signals output to each adder,

[0018] Fig.13 1 is an explanatory diagram showing a state in which the detection results of the respective SPAD circuits are superimposed to detect a peak value in the second embodiment.

[0019] Fig.14 1 is an explanatory diagram showing a state in which the phase of the detection timing in each small pixel is changed in the second operation as another distance measurement process.

[0020] Fig.15 is an explanatory diagram showing an example of a combination of two small pixels.

[0021] Fig.16 is an explanatory diagram showing another example of a combination of two small pixels.

[0022] Fig.17 is an explanatory diagram showing an example of a combination of four small pixels.

[0023] Fig.18A is an explanatory diagram showing a situation where 3×3 small pixels are combined from 4×4 small pixels.

[0024] Fig.18B This is an explanatory diagram showing a case where the combination of 4×4 small pixels is changed to a combination of 2×2 small pixels. DETAILED DESCRIPTION

[0025] A. First Implementation Method:

[0026] (A1) Device structure:

[0027] The optical distance measuring device 20 as the optical device of the first embodiment is a device for optically measuring distance. Figure 1 As shown, it is provided with: an optical system 30 for projecting light for distance measurement onto an object OBJ1 as an object to be measured and receiving reflected light, and a SPAD operation unit 100 for driving the optical system 30 and processing a signal obtained from the optical system 30. The optical system 30 is provided with: a light emitting unit 40 for emitting laser light; a scanning unit 50 for emitting the laser light from the light emitting unit 40 to a predetermined range to be measured and scanning; and a light receiving unit 60 for receiving reflected light from the range scanned by the laser light.

[0028] Figure 2Detailed description of the optical system 30 is shown. As shown in the figure, the light emitting unit 40 includes a semiconductor laser element (hereinafter, also referred to as a laser element) 41 for emitting laser light for distance measurement, a circuit substrate 43 on which a driving circuit of the laser element 41 is assembled, and a collimating lens 45 for making the laser light emitted from the laser element 41 parallel light. The laser element 41 is a laser diode capable of oscillating a so-called short-pulse laser, and the pulse width of the laser light is about 5 nsec. By using a short pulse of 5 nsec, the resolution of distance measurement can be improved.

[0029] The scanning unit 50 includes: a surface reflector 51 that reflects the laser light formed into parallel light by the collimating lens 45, a holder 53 that rotatably holds the surface reflector 51 through a rotating shaft 54, and a rotating solenoid 55 that drives the rotating shaft 54 ​​to rotate. The rotating solenoid 55 receives a control signal Sm from the outside and repeatedly rotates forward and reverse within a specified angle range (hereinafter referred to as a field of view angle range). As a result, the rotating shaft 54 ​​and then the surface reflector 51 also rotate within the range. As a result, the laser light incident from the laser element 41 via the collimating lens 45 scans within the specified field of view angle range in the horizontal direction (H direction) shown in the figure. The rotating solenoid 55 has an encoder (not shown) built in, which can output its rotation angle. Therefore, by reading the rotation angle of the surface reflector 51 as the output of the encoder, the scanning position can be obtained.

[0030] By driving the surface reflector 51 within a predetermined range, the laser light emitted by the light emitting unit 40 is scanned in the horizontal direction (H direction). The laser element 41 has a shape that is long in a direction (hereinafter referred to as V direction) perpendicular to the H direction. The optical system 30 including the surface reflector 51 of the scanning unit 50 is accommodated in the housing 32, and the light emitted toward the object OBJ1 and the reflected light from the object OBJ1 pass through the cover 31 provided on the housing 32.

[0031] The scanning unit 50 scans the pulse light emitted by the laser element 41 within a specified range specified by the height of the laser in the V direction and the angle range of the scanning unit 50 in the H direction. If there is an object OBJ1 such as a person or a car, the laser output from the optical ranging device 20 toward the area is diffusely reflected on the surface of the object OBJ1, and a part of it returns to the direction of the surface reflector 51 of the scanning unit 50. The reflected light is reflected by the surface reflector 51 and enters the light receiving lens 61 of the light receiving unit 60. The reflected light focused by the light receiving lens 61 is imaged on the light receiving array 65 that forms the light receiving surface. In the light receiving array 65, as shown in FIG. Figure 4 As shown, a plurality of light receiving elements 66 for detecting reflected light are arranged.

[0032] like Figure 3 As shown, the output signal from the light receiving array 65 of the light receiving unit 60 is input to the SPAD operation unit 100 corresponding to the distance measuring unit. Figure 3 , Figure 4 , the structure and operation of the SPAD operation unit 100 are explained. The SPAD operation unit 100 causes the laser element 41 to emit light to scan the external space, and calculates the distance to the object OBJ1 based on the time TF from the moment when the laser element 41 outputs the irradiation pulse to the moment when the light receiving array 65 of the light receiving unit 60 receives the reflected light pulse. The SPAD operation unit 100 has a well-known CPU and memory, and performs the processing required for distance measurement by executing a pre-prepared program. Specifically, in addition to the control unit 110 that performs overall control, the SPAD operation unit 100 also has an adding unit 120, a histogram generating unit 130, a peak detecting unit 140, a distance operation unit 150, and a timing control circuit 170.

[0033] like Figure 4 As shown in FIG. 1 , a plurality of light receiving elements 66 are arranged in the light receiving array 65 of the light receiving unit 60. Each light receiving element 66 is a common unit for detecting reflected light, and therefore is also referred to as a pixel 66 in the following description. Each pixel 66 is composed of 3×3 small pixels 69. Each small pixel 69 is composed of a plurality of, here 3×3, SPAD circuits 68. Figure 4 As shown, the 3×3 small pixels 69 have the same structure in that they are all composed of 3×3 SPAD circuits 68, but the arrangement in the pixel 66 is different. Therefore, when it is necessary to distinguish each small pixel 69, the small pixel 69 from the upper left to the lower right is called small pixel s1, s2, ... s9. The number of small pixels 69 constituting the pixel 66 can be any number as long as it is plural, but considering the lower limit of resolution, the effect of improving the S / N ratio, etc., it is preferably about 4 (for example, 2×2) to 16 (for example, 4×4).

[0034] The adding section 120 is a circuit for performing addition operation on the output of the SPAD circuit 68 constituting the small pixel 69 included in the pixel 66 constituting the light receiving section 60. Figure 4 As shown, the light receiving array 65 of the light receiving unit 60 is composed of a plurality of pixels 66 arranged in the V direction of the reflected light. The pixel 66 is a unit for detecting the object OBJ1 during distance measurement and measuring the distance to the object OBJ1. On the other hand, one pixel 66 is composed of 3×3 small pixels 69, and each small pixel 69 can be independently controlled to be turned on and off. That is, as a whole pixel 66, in this embodiment, the 9 small pixels s1 to s9 can be made to work independently.

[0035] The SPAD circuit 68 uses an avalanche photodiode (APD) that achieves high responsiveness and excellent detection capabilities. If reflected light (photons) is incident on the APD, electron-hole pairs are generated, and the electrons and holes are accelerated in the high electric field, respectively, causing collision ionization to generate new electron-hole pairs (avalanche phenomenon). In this way, the APD can amplify the incidence of photons, so when the intensity of the reflected light decreases, such as in the case of a distant object, the APD is mostly used. The operation mode of the APD includes a linear mode that operates with a reverse bias voltage less than the breakdown voltage, and a Geiger mode that operates with a reverse bias voltage greater than the breakdown voltage. In the linear mode, the number of electron-hole pairs that disappear from the high electrolysis area is larger than the generated electron-hole pairs, and the fission of the electron-hole pairs stops naturally. Therefore, the output current from the APD is roughly proportional to the amount of incident light.

[0036] On the other hand, in the Geiger mode, even the incidence of a single photon can cause an avalanche phenomenon, so the detection sensitivity can be further improved. Such an APD operating in the Geiger mode is sometimes called a single photon avalanche diode (SPAD: Single Photon Avalanche Diode).

[0037] Each SPAD circuit 68 is as follows Figure 4 As shown in the equivalent circuit of , an avalanche diode Da and a quenching resistor Rq are connected in series between the power supply Vcc and the ground line, and the voltage at the connection point is input to the inversion element INV, which is one of the logic operation elements, and converted into a digital signal after the voltage level is inverted. The output signal Sout of the inversion element INV is directly output to the outside. The quenching resistor Rq is configured as a FET, and if the selection signal SC is valid, its on-resistance works as the quenching resistor Rq. If the selection signal SC is invalid, the quenching resistor Rq becomes a high impedance state, so even if light is incident on the avalanche diode Da, no quenching current flows, and as a result, the SPAD circuit 68 does not operate. The selection signal SC is output to the 3×3 SPAD circuits 68 in the small pixel 69, which is used to specify which small pixel 69 from each pixel 66 is to be read or not read. In addition, the avalanche diode Da can also be used in a linear mode, and its output can be directly processed as an analog signal. In addition, a PIN photodiode can also be used instead of the avalanche diode Da.

[0038] If light is not incident on the SPAD circuit 68, the avalanche diode Da remains in a non-conducting state. Therefore, the input side of the inversion element INV is maintained in a pull-up state, that is, a high level H, through the quenching resistor Rq. Therefore, the output of the inversion element INV is maintained at a low level L. If light is incident on each SPAD circuit 68 from the outside, the avalanche diode Da becomes energized by the incident light (photon). As a result, a large current flows through the quenching resistor Rq, the input side of the inversion element INV temporarily becomes a low level L, and the output of the inversion element INV is reversed to a high level H. As a result of a large current flowing through the quenching resistor Rq, the voltage applied to the avalanche diode Da is reduced, so the power supply to the avalanche diode Da stops, and the avalanche diode Da returns to a non-conducting state. As a result, the output signal of the inversion element INV is also reversed and returned to a low level L. As a result, if light (photon) is incident on each SPAD circuit 68, the inversion element INV output becomes a pulse signal of a high level in a very short time. Therefore, when the selection signal SC is set to high level H according to the timing at which each SPAD circuit 68 receives light, the output signal of the AND circuit SW, that is, the output signal Sout from each SPAD circuit 68 becomes a digital signal reflecting the state of the avalanche diode Da.

[0039] The total 9 output signals Sout of the 3×3 SPAD circuits 68 included in the small pixel 69 are as follows: Figure 4 The outputs of the nine SPAD circuits 68 in each small pixel 69 are collected by the adders 121 to 129 and output to the histogram generation unit 130 for histogram generation.

[0040] Figure 5 This state is illustrated in FIG. 4 . The laser element 41 of the light emitting unit 40 emits light, and if the reflected light from the object OBJ1 enters the pixel 66 corresponding to one pixel arranged on the light receiving surface of the light receiving unit 60, each small pixel 69 outputs a pulse signal at the timing (the timing of time TOF) of receiving the reflected light. Figure 5 As shown in the left column, each of the SPAD circuits 68 constituting the small pixels s1 to s9 is also affected by disturbance light (noise) and the like, and outputs the output signal Sout at various timings. Figure 5 SPAD_1 to SPAD_N in the left column (N=9 here). In addition, Figure 5 The reference symbol t in denoted by FIG. 8 represents time (the same also applies to other drawings).

[0041] For each of the small pixels s1 to s9, the output signal Sout outputted by each of the SPAD circuits 68 is summed up by adders 121 to 129, as shown in FIG. Figure 5 As shown in the center, the SPAD response numbers As1 to As9 are calculated. As shown in the figure, each SPAD circuit 68 also outputs an output signal Sout caused by noise, but each SPAD circuit 68 outputs an output signal Sout near the return time TOF corresponding to the reflected light of the pulse light emitted by the laser element 41. Therefore, in the SPAD response numbers As1 to As9 calculated by summing them up, the peak of the SPAD response number appears at the return time TOF. The SPAD response numbers As1 to As9 calculated for each small pixel s1 to s9 are further summed up to calculate the histogram for the pixel 66. Figure 5 It is shown in the right column of .

[0042] If multiple measurements are performed at the same scanning position, the histogram generating unit 130 further adds the SPAD response numbers As1 to As9 obtained by the adding unit 120 for the small pixels s1, s2, ..., s9, as shown in FIG. Figure 5 As shown in the example in the right column, a histogram with a peak at the return time TOF is generated. If the SPAD response numbers are summed up for small pixels s1, s2...s9, a peak of the response number is formed near the time TOF. Due to the nature of the SPAD circuit 68, noise is also contained in the output pulse signal. The noise is randomly generated due to interference light such as sunlight. The noise-based pulse signal is randomly generated, so if the output signal Sout from the SPAD circuit 68 is added, and the SPAD response numbers As1~As9 obtained for the small pixels s1, s2...s9 are further summed up, the reflected light from the object OBJ1 appears randomly relative to the noise, and is detected at the return time, so a peak is obtained at a specific return time. In other words, the signal corresponding to the reflected light pulse is accumulated, and the signal corresponding to the noise is not accumulated, so the signal corresponding to the reflected light pulse becomes clear. The so-called S / N ratio becomes higher.

[0043] In this way, if the histogram generating unit 130 generates a histogram for pixels, the peak value detecting unit 140 detects the peak value of the signal by receiving the histogram. The peak value of the signal is generated at the return time corresponding to the reflected light pulse from the object OBJ1 that is the object of the distance measurement. In this way, if the peak value is detected, the distance calculating unit 150 measures the time TOF from the irradiated light pulse to the peak value of the reflected light pulse, thereby detecting the distance D to the object. The detected distance D is output to the outside, for example, if the optical distance measuring device 20 is mounted on an automatic driving vehicle, it is output to the automatic driving device, etc. Of course, in addition to mobile bodies such as unmanned aircraft, cars, and ships, it can also be used as a fixed distance measuring device.

[0044] Figure 3 The control unit 110 shown in the figure outputs a command signal SL for determining the emission timing of the laser element 41 to the circuit board 43 of the light emitting unit 40, a selection signal SC for determining whether to activate the SPAD circuit 68, and also outputs the timing of generating the histogram to the histogram generating unit 130, a signal St for instructing the correction of the histogram, a signal Sp for switching the threshold value Tn of the peak detection to the peak detecting unit 140, a driving signal Sm for the rotary solenoid 55 of the scanning unit 50, etc. Furthermore, the timing control unit 170 provided in the control unit 110 outputs a timing control signal Sa for adjusting the phase of the addition operation of each small pixel 69 to the adding unit 120. By the control unit 110 outputting these signals at a predetermined timing, the SPAD operation unit 100 operates as a determination unit for detecting the object OBJ1 existing in a predetermined range together with the distance D to the object OBJ1.

[0045] Next, the structures of the adding unit 120, the histogram generating unit 130, the peak detecting unit 140, and the structure and operation of the timing control unit 170 for adjusting the operation timing of these units in this embodiment will be described in sequence. Figure 6 As shown, the nine small pixels 69 (s1 to s9) constituting the pixel 66 are connected to adders 121 to 129 constituting the adder 120, respectively. Figure 4 The adders 121 to 129 calculate and output the outputs of the 3×3 SPAD circuits 68 included in the small pixels s1 to s9 and the SPAD response numbers As1 to As9.

[0046] The SPAD response numbers As1 to As9 outputted from the adders 121 to 129 are inputted to the memories m1 to m9 and sequentially stored in the memories m1 to m9. The SPAD response numbers As1 to As9 stored in the memories m1 to m9 are read at a predetermined timing by the histogram generators 131 to 139 provided in the histogram generator 130 of the next stage.

[0047] The histogram generators 131 to 139 respectively accumulate the multiple detection results based on the small pixels 69, that is, the multiple SPAD response numbers As1 to As9, and generate histograms T1 to T9 for each small pixel s1 to s9. The generated histograms T1 to T9 are input to each of the peak detectors 141 to 149 of the peak detection unit 140 and the total peak detector 160. Each peak detector 141 to 149 detects the position of its peak value and the return time TOF on the time axis based on the histograms T1 to T9 generated for the small pixels s1 to s9 respectively. This is the return time of the reflected light from the object corresponding to each of the small pixels s1 to s9. In addition, the total peak detector 160 detects the position of its peak value and the return time TOF on the time axis based on the histogram TT after the histograms T1 to T9 generated for all the small pixels s1 to s9 are summed up. This is the return time of the reflected light from the object corresponding to the pixel 66 composed of the small pixels s1 to s9.

[0048] Each of the adders 121 to 129 and memories m1 to m9 described above operates at a timing determined by a timing control signal Sa from a timing control unit 170 in the control unit 110, and reads and stores a signal from the SPAD circuit 68. The configuration of the timing control unit 170 and the timing control signal Sa outputted by the timing control unit 170 are described below.

[0049] like Figure 7 As shown, the timing control unit 170 includes an oscillator (OSC) 180 that outputs a clock signal CLK of a predetermined frequency, and 8-stage delay circuits 172 to 179 that input the clock signal CLK and delay the phase of the clock signal CLK by a predetermined time. The timing control signal Sa, which is used as a reference by the clock signal CLK output by the oscillator 180, is input to the adder 121 and the trigger terminal of the memory m1. If the timing control signal Sa1 is input to the trigger terminal, the adder 121 outputs the SPAD response number As1 at the timing, and the memory m1 stores it. The timing control signal Sa2, which is delayed from the reference timing control signal Sa1 by the delay time DL based on the delay circuit 172, is input to the adder 122 and the trigger terminal of the memory m2. If the timing control signal Sa2 is input to the trigger terminal, the adder 122 outputs the SPAD response number As2 at the timing, and the memory m2 stores it. Similarly, according to the timing control signals Sa3 to Sa9 whose phases are delayed one by one, adders 123 to 129 respectively output SPAD response numbers As3 to As9, and each of memories m3 to m9 stores the corresponding SPAD response number As3 to As9. Figure 7Although not shown in the figure, the SPAD response numbers As1 to As9 stored in the memories m1 to m9 are read at desired timing by the peak detectors 141 to 149 and the total peak detector 160 included in the peak detection unit 140 at the subsequent stage.

[0050] Figure 8 FIG. 2 shows the state of reading the SPAD response number based on the timing control signal after the phase is gradually delayed. Figure 8 In FIG. 4 , for ease of understanding, the number of SPAD circuits 68 is set to 4. Figure 8 In the figure, the unfilled circles indicate that the SPAD response number is obtained under the timing control signal Sa1, and the filled circles indicate that it is obtained under the timing control signal Sa2 whose phase is delayed by the delay time DL from the timing control signal Sa1. In addition, the unfilled squares indicate that the SPAD response number is obtained under the timing control signal Sa3 whose phase is further delayed by the delay time DL from the timing control signal Sa2, and the filled squares indicate that it is obtained under the timing control signal Sa4 whose phase is delayed by the delay time DL from the timing control signal Sa3.

[0051] like Figure 8 As shown in the top level, the number of SPAD responses is repeatedly calculated based on each timing control signal Sa1 to Sa4. Among them, the second level shows the number of SPAD responses As1 calculated based on the timing control signal Sa1, the third level shows the number of SPAD responses As2 calculated based on the timing control signal Sa2, the fourth level shows the number of SPAD responses As3 calculated based on the timing control signal Sa3, and the fifth level shows the number of SPAD responses As4 calculated based on the timing control signal Sa4. Figure 8 The highest level of corresponds to the result obtained by summing up the four SPAD response numbers As1 to As4.

[0052] like Figure 8 As shown, the sampling timing of the SPAD response numbers As1 to As4 detected by each small pixel s1 to s4 is sequentially staggered by the delay time DL of the delay circuit 172. Figure 8 In the example shown, the delay time DL is set so as to divide the light emission period of the light emitting unit 40 into four equal parts, so that the detection of the SPAD response numbers As1 to As4 based on the small pixels s1 to s4 will not be repeated. Figure 1 to Figure 7 In the embodiment shown, 3×3 small pixels 69 are provided, so in the actual structure, the delay time DL is set in such a way that the light emission cycle of the light emission pulse of the light emitting unit 40 is divided into 9. That is, the time interval of the detection based on the small pixels s1 to s9 is shorter than the width of the pulse light emitted by the light emitting unit 40.

[0053] (A2) Details of ranging processing:

[0054] Based on the hardware structure described above, use Fig. 9 Control performed by the CPU included in the control unit 110 will be described. Fig. 9 The distance measurement processing routine shown is repeatedly executed at predetermined intervals. When the processing routine is started, first, a process of repeating steps S210 to S230 a predetermined number of times is performed on small pixels s1 to s9 (steps S201s to S201e).

[0055] In this repeated process, firstly, timing control is performed (step S210). The so-called timing control is such as using Figure 7 , Figure 8 As shown in FIG. 2 , the processing of the timing control signals Sa1 to Sa9 output to the adding unit 120 and the histogram generating unit 130 during the ranging is prepared. In the present embodiment, each timing control signal Sa1 to Sa9 is determined as the output of the clock signal CLK and the delay circuits 172 to 179. As described later, each timing control signal Sa1 to Sa9 may be arbitrarily specified. Therefore, it is assumed that the timing control processing (step S210) is performed.

[0056] After the timing control is performed, the control unit 110 performs a light emission process (step S220) in which the command signal SL is output to the light emitting unit 40 to make the laser element 41 emit pulsed light, and then performs a light receiving process (step S230). Here, in the light receiving process, the control unit 110 outputs a selection signal SC to the light receiving unit 60, and outputs timing control signals Sa1 to Sa9 to the adding unit 120, and performs calculation and output of the SPAD response numbers As1 to As9 based on the above-mentioned adders 121 to 129, and storage of the SPAD response numbers As1 to As9 based on the memories m1 to m9.

[0057] The above-mentioned processing (steps S210 to S230) is repeated a predetermined number of times, so when the repeated processing is completed, the memories m1 to m9 store the SPAD response numbers As1 to As9 of the corresponding small pixels s1 to s9, which are based on the timing control signals Sa1 to Sa9 from the timing control unit 170, for the number of repeated times. Therefore, in the next step S240, the SPAD response numbers As1 to As9 of the multiple times stored in the corresponding memories m1 to m9 are summed up by the histogram generators 131 to 139 of the histogram generating unit 130 to generate respective histograms.

[0058] Using the histograms obtained in this way about each small pixel s1 to s9, in the next step S250, detection and distance measurement processing for pixels and small pixel objects is performed. This processing is equivalent to the processing based on peak detection by each peak detector 141 to 149 and the total peak detector 160 in the peak detection unit 140. In addition, in step S250, as described later, detection and distance measurement (first processing) in units of small pixels 69 and detection and distance measurement (second processing) in units of pixels 66 can be performed. If this processing is completed, the distance measurement processing routine is terminated.

[0059] The detection and ranging process for the pixel and the small pixel object shown as step S250 is described. At the time of starting the process of step S250, the histogram generators 131 to 139 of the histogram generating unit 130 generate a histogram obtained by summing the SPAD response numbers As1 to As9 of multiple quantities stored in the memories m1 to m9. The histogram obtained for the small pixels s1 to s9 is as follows: Figure 8 As shown, the timings at which the number of SPAD responses is detected are different.

[0060] The peak detection unit 140 detects a peak value using the histograms T1 to T9 corresponding to the small pixels s1 to s9 and a total histogram TT obtained by calculating the total of these histograms. Fig.10 This state is shown. Each peak detector 141 to 149 of the peak detection unit 140 and the total peak detector 160 compare the obtained histograms T1 to T9 and the total histogram TT with the thresholds r1 to r9 and the threshold R, thereby detecting the existence of the peak and its position on the time axis (return time). At this time, there is also a histogram in which there is no peak exceeding the threshold. That is, it functions as a limit of the spatial resolution in space when the small pixels s1 to s9 detect the object OBJ1. Furthermore, the detection of the SPAD response numbers As1 to As9 for each small pixel s1 to s9 is not at the same timing, but as Figure 8 As shown in FIG. 1 , the timing is shifted by the delay time DL each time. As a result, the positions of the histograms T1 to T9 obtained by superimposing the SPAD response numbers As1 to As9 multiple times are different on the time axis, so the time axis has a higher time resolution than the interval of the pulse emission. As a result, the total histogram TT obtained by further summing these calculations is as follows: Figure 8 The top level is shown with high resolution on the time axis.

[0061] For example, in Fig.10In the example shown, the histogram T1 for the small pixel s1 exceeds the threshold value r1 at time t1, and a peak is detected. On the other hand, the histogram T9 for the small pixel s9 does not have a peak that exceeds the threshold value r9 at any time. In addition, the total histogram TT exceeds the threshold value R at time t1. As a result, the distance calculation unit 150 determines that the object OBJ1 exists at least at the position corresponding to the small pixel s1 and at the place of return time t1, and calculates its position and distance D. On the other hand, in the small pixel s9, it is determined that the object OBJ1 does not exist. Furthermore, as a whole, the pixel 66 composed of small pixels s1 to s9 is determined to exist at the position corresponding to the pixel 66 and at the distance D corresponding to the return time t1. Furthermore, assuming that a peak is detected at time t2 immediately after time t1 in the histogram T2 for the small pixel s2, it is determined that the object OBJ1 exists at the spatial position corresponding to the small pixel s2 and at the distance corresponding to the return time t2, and based on the total histogram TT, it is determined that the object OBJ1 exists at the distance corresponding to the return times t1 and t2 in the pixel 66. In other words, it can be determined that the object OBJ1 of a size at least spanning the small pixels s1 and s2 exists near the return times t1 and t2.

[0062] Fig.11 Other detection states are illustrated. Fig.11 In the example shown, the histogram T1 for the small pixel s1 exceeds the threshold value r1 at time t1, and a peak is detected. On the other hand, the histogram T9 for the small pixel s9 exceeds the threshold value r9 at time t9, and a peak is detected. In addition, no peak is detected in the other small pixels s2 to s8. On the other hand, the total histogram TT is lower than the threshold value R at time t1 and time t9, and no peak is detected. In this case, small objects OBJ1 and OBJ2 exist in the small pixels s1 and s9, and the distances to the objects are quite different as shown in the return times t1 and t9. Therefore, in this case, it can be judged that objects of a size corresponding to the small pixels exist at different distances. That is, the SPAD operation unit 100 of this embodiment is capable of performing the following processing: based on the results of detection of separated time intervals performed by small pixels s1 to s9, detecting objects existing in a specified range with a first spatial resolution and a resolution on a first time axis; based on the result obtained by superimposing the results of detection of separated time intervals performed by multiple small pixels with different detection phases, detecting objects OBJ1 and OBJ2 existing in a specified range with a second spatial resolution lower than the first spatial resolution and a resolution on a second time axis higher than the resolution on the first time axis.

[0063] As described above, according to the optical distance measuring device 20 of the first embodiment, the position and distance of an object can be detected with a higher temporal resolution than the interval of the light emitting pulses of the light emitting unit 40 and a higher spatial resolution than the pixel 66. Moreover, the required memory capacity is suppressed to be equal to or less than the case where the temporal resolution is increased in units of the pixel 66 for detection. That is, although the spatial resolution is increased, the Figure 8 Compared with the case of detecting the entire pixel as shown in the top level, there is no need to increase the amount of pre-stored data. In this embodiment, detection using the timing control signals Sa1 to Ss9 from the timing control unit 170 is repeated, and all the data is stored in the memories m1 to m9, and then a histogram is generated. However, if the number of SPAD responses As1 to As9 detected this time is added to the number of SPAD responses As1 to As9 detected in the previous cycle and stored in the memories m1 to m9 each time the timing control signals Sa1 to Sa9 are output, the capacity of the memories m1 to m9 can be further reduced. In this case, the histogram generation unit 130 can also be configured to read only the accumulated values ​​stored in the memories m1 to m9.

[0064] B. Second Implementation Method:

[0065] Next, the second embodiment will be described. The optical distance measuring device 20 of the second embodiment has the same structure as the first embodiment except that the structures of the control unit 110A and the adding unit 120A constituting the SPAD operation unit 100 are different. In the second embodiment, the control unit 110A and the adding unit 120A have Fig.12 The structure shown. In the second embodiment, 110A includes an oscillator 180A and a memory selector 190 as a timing control unit 170A. The oscillation frequency of the oscillator 180A in the second embodiment is about 9 times higher than that in the first embodiment. The clock signal CLK output from the oscillator 180A is supplied to the adders 121 to 129 and the memories m1 to m9 provided in the adder 120A. In addition, 9 timing control signals Sa1 to Sa9 are output from the memory selector 190 to the memories m1 to m9. Through the memory selector 190, the timing control signals Sa1 to Sa9 are output from the memory selector 190, but the output timing is determined by the timing control of step S210 described in the ranging processing routine in the first embodiment. The timing control signals Sa1 to Sa9 will be described in detail later.

[0066] In the optical distance measuring device 20 of the second embodiment having the above-mentioned structure, a high-frequency clock signal CLK is input to the adders 121 to 129 of the adding section 120A. Figure 8As shown in the top level, the SPAD response numbers As1 to As9 are calculated for each clock signal CLK. Figure 4 As shown, the adder 121 adds the outputs of the SPAD circuits 68 by hardware to obtain the SPAD response numbers As1 to As9, so its responsiveness is high. Therefore, the SPAD response numbers As1 to As9 can be obtained following the clock signal CLK having a higher frequency than that of the first embodiment.

[0067] On the other hand, the memories m1-m9 store the signals of the SPAD response numbers As1-As9 from the adders 121-129 respectively according to the corresponding timing control signals Sa1-Sa9. Figure 8 The top level operates as above, and the SPAD response numbers As1 to As9 are calculated at all timings, such as Figure 8 As shown below, each time a timing control signal Sa1-Sa9 is output, memories m1-m9 store the SPAD response numbers As1-As9 output at the timing.

[0068] Therefore, if the timing control signals Sa1 to Sa9 are output at substantially the same timing as in the first embodiment, that is, at the timing after each delay of the clock signal CLK, the position and distance of the object can be detected with a higher temporal resolution than the interval of the light emitting pulses of the light emitting unit 40 and a higher spatial resolution than the pixel 66, as in the first embodiment. Moreover, the required memory capacity is suppressed to be equal to or less than the case where the temporal resolution is increased in units of the pixel 66 for detection. That is, although the spatial resolution is increased, the memory capacity is higher than that of the first embodiment. Figure 8 Compared with the case of detecting the entire pixel as shown in the top level, there is no need to increase the amount of pre-stored data, etc., and the same function and effect as the first embodiment can be achieved. In addition, such function and effect are also the same in the following other embodiments including the third embodiment.

[0069] C. Third Implementation Method:

[0070] like Fig.12 As shown, according to the hardware used in the second embodiment, the timing of the timing control signals Sa1 to Sa9 output to the memories m1 to m9 of the adder 120 can be freely set according to the memory selector 190. Therefore, for example, when the emission of the light emitting pulse by the light emitting unit 40 and the light receiving process by the light receiving unit 60 are repeated multiple times ( Fig. 9 , steps S201s to S201e), the timing control signals Sa1 to Sa9 output from the memory selector 190 can be changed each time. This example is described below as a third embodiment.

[0071] For example, Fig.13 As shown, in each repetitive process, in the timing control (step S210), the timing stored in the memories m1 to m9 may be replaced. Fig.13 In order to facilitate understanding, Figure 8 Similarly, the figure shows processing of the SPAD response numbers As1 to As4 from four small pixels s1 to s4. In this example, the memory selector 190 outputs the timing control signals Sa1 to Sa4 stored in the memories m1 to m4 to the small pixels s1 to s4 in the first iteration, each delaying the timing of the clock signal CLK. As a result, the SPAD response numbers As1 to As4 stored in the memories m1 to m4 are equal to Figure 8 The unfilled circle, filled circle, unfilled square, filled square and Figure 8 The same. It is shown as SPAD response number As11~As41. For the addition of SPAD response number Asij, the former i represents the number of small pixels s1~s4, and the latter j represents the number of repetitions. Compared with the first repetition, the SPAD response number As12~As42 of the second repetition is staggered one by one for the small pixels as shown in the figure. The timing control signals Sa1~Sa4 are further staggered one by one for the third and fourth repetitions.

[0072] exist Fig.13 The right column of shows the superimposed response numbers At1 to At4 obtained by superimposing the SPAD response numbers detected and stored in the memories m1 to m4 in the case of four repetitions. This is equivalent to the histograms T1 to T4 generated by the histogram generators 131 to 134 of the histogram generating unit 130. It is also possible to further calculate these sums to obtain the total response number Att equivalent to the total histogram TT. Fig.13 The next lower level is shown.

[0073] In this way, for all small pixels s1 to s9, the peak value of the reflected light can be detected with a high spatial resolution corresponding to the size of the small pixels s1 to s9 and a high temporal resolution corresponding to the clock signal CLK. In addition, the capacity of the memories m1 to m9 does not increase compared to the first and second embodiments. In addition, the timing control signals Sa1 to Sa9 output from the memory selector 190 can be changed each time the detection of the SPAD response numbers As1 to As9 is repeated, so it is not necessarily necessary to Fig.13 The timing can be changed periodically as shown in FIG. 2 or more of the detections that are repeated multiple times can be set to the same timing, and the others can be set to different timings.

[0074] D. Fourth Implementation Method:

[0075] Similarly, the timing control signals Sa1 to Sa9 outputted from the memory selector 190 can be changed each time the detection of the SPAD response numbers As1 to As9 is repeated, and the timing after the second detection can be changed using the first detection result. This example is described below as a fourth embodiment. Fig.14 This shows an example in which the timing of the second and subsequent detections is changed and measured by the first detection. Fig.14 also with Figure 8 , Fig.13 Similarly, for ease of understanding, only small pixels s1 to s4 are illustrated, but it is of course also possible to implement the method on small pixels s1 to s9 .

[0076] exist Fig.14 In the example shown, the left column shows the first action of the repetition, and the right column shows the second and subsequent actions. Figure 8 Similarly, for small pixels s1 to s4, the SPAD response numbers Bs11 to Bs41 are read at the timing of dividing the light-emitting and light-receiving cycle into four equal parts. Fig.13 same.

[0077] If the first action is performed, the SPAD response numbers Bs1 to Bs4 are summed up and calculated to obtain the total histogram Bt1. If the total histogram Bt1 is detected, the approximate position of the peak of the reflected light can be known. Therefore, the total histogram Bt1 is detected in the first action, and the timing control signals Sa1 to Sa4 are adjusted so that the rising and falling parts of the part considered to be the peak can be detected in detail. Specifically, the timing control signals Sa1 and Sa2 for small pixels s1 and s2 are slightly delayed, the timing control signal Sa3 for small pixel s3 is slightly advanced, and the timing control signal Sa4 for small pixel s4 is maintained in the original state, so that the SPAD response number can be detected in detail in the rising part Ra1 and the falling part Ra2 of the waveform forming the peak. As a result, the timing control signals Sa1 to Sa4 for each small pixel s1 to s4 can be concentrated on the rising part Ra1 and the falling part Ra2 of the waveform forming the peak. As a result, the information of the most important part of the waveform forming the peak can be obtained in detail. The rising and falling shapes of the waveform forming the peak can help to know whether the detected object OBJ1 is an object with clear outlines such as metal and concrete, or an object with blurred outlines such as a tree or a human body.

[0078] In the above embodiment, the detection interval of each small pixel s1 to s4 is kept constant, and the detection phase of each small pixel is advanced or delayed, but the timing control signal Sa output from the timing control unit 170 can also be freely set at intervals. In this way, the detection accuracy of the rise and fall of the reflected light pulse can be further improved. Of course, not only the rise and fall, but also the places near the peak of the reflected light pulse, etc., which improve the detection accuracy, can be freely set. In addition, in the above embodiment, the first measurement is used to adjust the phase of the second measurement, but the phase of the next measurement can also be adjusted by using the measurement results of each measurement.

[0079] E. Fifth Implementation Method:

[0080] (1) Several embodiments have been described above, but other embodiments are also possible. A fifth embodiment is to collect a plurality of small pixels to detect the number of SPAD responses from small pixels s1 to s9. In this case, Figure 6 In the structure shown in the figure, the histogram generator of the histogram generator 130 may read the contents of the memories m1 and m2 alternately and perform sum calculation. Fig.15 In Fig.15 In the example shown, the histogram generator calculates the total number of SPAD responses of two small pixels arranged vertically and generates a histogram. The histogram Tu1 generated as the total value of the number of SPAD responses after the small pixels s1 and s4 are combined in this case is consistent with the histogram Ts1+Ts4 generated for the small pixels s1 and s4 respectively. Hereinafter, the histogram generated as the total value of the number of SPAD responses of a plurality of small pixels combined is referred to as a group histogram.

[0081] exist Fig.15 In the example shown, the histograms for each group are as follows.

[0082] Tu1: Ts1+Ts4

[0083] Tu2: Ts2+Ts5

[0084] Tu3: Ts3+Ts6

[0085] Tu4: Ts4+Ts7

[0086] Tu5: Ts5+Ts8

[0087] Tu6: Ts6+Ts9

[0088] According to the above configuration, an object existing astride a position corresponding to two small pixels arranged in the longitudinal direction with respect to the pixel 66 can be detected with high accuracy.

[0089] (2) The method of aggregating small pixels when obtaining a group histogram is not limited to Fig.15 The example shown is Fig.16 In this case, each set of histograms Tv1 to Tv6 and the histogram generated for the small pixels have the following correspondence relationship.

[0090] Tv1: Ts1+Ts2

[0091] Tv2: Ts2+Ts3

[0092] Tv3: Ts4+Ts5

[0093] Tv4: Ts5+Ts6

[0094] Tv5: Ts7+Ts8

[0095] Tv6: Ts8+Ts9

[0096] The method of detecting the position of the object and measuring the distance in this case is the same as that described in the above embodiment. In this way, an object existing across the position corresponding to two small pixels 69 arranged horizontally with respect to the pixel 66 can be detected with high accuracy.

[0097] (3) The histogram Ts of small pixels is not limited to being grouped in pairs, but may be grouped in M ​​pairs (M ≥ 3). Fig.17 The case of grouping every 4 is illustrated. In this case, the structure is to combine every 4 histograms Ts1 to Ts9 to obtain the group histogram Tw. Specifically, the group histogram Tw is obtained as:

[0098] Tw1=Ts1+Ts2+Ts4+Ts5

[0099] Tw2=Ts2+Ts3+Ts5+Ts6

[0100] Tw3=Ts4+Ts5+Ts7+Ts8

[0101] Tw4=Ts5+Ts6+Ts8+Ts9.

[0102] The processes of obtaining the group histogram Tw, detecting the object, and measuring the distance are the same as those in the other embodiments.

[0103] In this way, the SPAD operation unit 100 can detect the spatial position of the above-mentioned object OBJ1 existing in the above-mentioned range with a resolution higher than the resolution using pixel 66 as a unit, based on the result obtained by superimposing the detection results of a part of the multiple small pixels s1~s9 with different detection phases at separated time intervals.

[0104] F. Sixth Implementation Method:

[0105] The number of small pixels combined in this way and the structure of the combination are changed in the middle of the measurement as a sixth embodiment. Fig.18A as well as Fig.18B As shown, when there are 4×4 small pixels (a total of 16) constituting pixel 66, the pixels can be grouped by 3×3 small pixels or 2×2 small pixels. For such grouping, it is useful to increase the number of small pixels in the group when it can be judged that the return time of the reflected light is short and the object OBJ1 is nearby in the first repeated detection, and to reduce the number of small pixels in the group when it can be judged that the return time of the reflected light is long and the object OBJ1 is far away in the first repeated detection. This is because if the object OBJ1 is nearby, the possibility that the reflected light from the object OBJ1 enters multiple small pixels at the same time is high, and if the object OBJ1 is far away, the possibility that the reflected light from the object OBJ1 enters multiple small pixels is low. In addition, the combination of small pixels can also be changed in the middle of the measurement. For example, when it is judged that there is a high possibility of a slender object in the vertical direction, the combination of small pixels is made vertically long, and when it is judged that there is a high possibility of a slender object in the horizontal direction, the combination of small pixels is made horizontally long, etc. Such a number of combinations is sometimes called a merging number.

[0106] In this way, by changing the number of merging according to the distance of the object OBJ1, it is easy to switch whether to prioritize time resolution or spatial resolution. If the number of small pixels in the group is increased, the number of SPAD responses included in the group histogram increases, so the time for generating the histogram can be shortened, and the number of distance measurements at the same position can be reduced, increasing the number of scans.

[0107] G. Other implementations:

[0108] In each of the above-mentioned embodiments, part of the structure implemented by hardware can also be replaced by software. At least a part of the structure implemented by software can also be implemented by a discrete circuit structure. In addition, in the case where part or all of the functions of the present invention are implemented by software, the software (computer program) can be provided in the form of a recording medium that can be read by a computer. The so-called "computer-readable recording medium" is not limited to portable recording media such as floppy disks and CD-ROMs, but also includes various internal storage devices in computers such as RAM and ROM, and external storage devices fixed to computers such as hard disks. That is, the so-called "computer-readable recording medium" has a broad meaning of any recording medium that includes not temporary but fixed data packets. In addition, the processing performed in the above-mentioned optical ranging device can be understood as being implemented as an optical ranging method.

[0109] The present invention is not limited to the above-mentioned embodiments, and can be implemented in various structures within the scope of the main purpose. For example, in order to solve part or all of the above-mentioned problems, or to achieve part or all of the above-mentioned effects, the technical features in the embodiments corresponding to the technical features in each mode recorded in the summary column of the invention can be appropriately replaced or combined. In addition, as long as the technical feature is not described as necessary in this specification, it can be appropriately deleted.

Claims

1. An optical distance measuring device that uses light to measure the distance to an object. The optical distance measuring device comprises: A light emitting unit emits pulse light to a specified range; An optical system for imaging the reflected light from the specified range corresponding to the pulsed light on a pixel for detection; A light receiving unit, in which a plurality of small pixels capable of respectively detecting the reflected light are arranged in the pixel; a timing control unit for performing, at different phases, a first detection of the reflected light repeatedly performed by at least a part of the plurality of small pixels at intervals of time, and a second detection of the reflected light repeatedly performed by the other small pixels at intervals of time; as well as The specifying unit specifies the spatial position of the object including the distance to the object existing in the predetermined range by superimposing the result of the first detection and the result of the second detection repeatedly performed by each of the small pixels at the time interval.

2. The optical distance measuring device according to claim 1, wherein: The small pixel has a plurality of light detection circuits capable of independently detecting incident light as electrical response signals. The determining unit comprises, for each of the small pixels: an adding section that performs a total calculation on the number of response signals of the light detection circuit included in the small pixel at the timing of the first detection and the second detection separated by the time interval; as well as The storage unit stores the number of the response signals calculated by the sum of at least one distance measurement amount.

3. The optical distance measuring device according to claim 2, wherein: The light detection circuit is a circuit using a single-photon avalanche diode.

4. The optical distance measuring device according to any one of claims 1 to 3, wherein: The timing control section makes a phase of the first detection or the second detection different for each of the plurality of small pixels.

5. The optical distance measuring device according to any one of claims 1 to 3, wherein: The timing control section sets the time interval in each of the small pixels to be constant.

6. The optical distance measuring device according to any one of claims 1 to 3, wherein: The timing control section can change the time interval of the first detection or the second detection in each of the small pixels.

7. The optical distance measuring device according to claim 6, wherein: Before changing the time interval, the pulse light is emitted and the first detection or the second detection is performed using the small pixels at the time interval, and based on the results of the first detection or the second detection, the time interval of the first detection or the second detection performed by each small pixel is determined.

8. The optical distance measuring device according to any one of claims 1 to 3, wherein: A time interval between the first detection and a time interval between the second detection performed by the small pixel are shorter than a width of the pulse light emitted by the light emitting unit.

9. The optical distance measuring device according to any one of claims 1 to 3, wherein: The determining part performs: A first process of detecting an object existing in the predetermined range at a first spatial resolution and a first time axis resolution based on a result of the first detection or the second detection performed by the small pixel at intervals of the time interval; as well as The second processing detects the object existing in the specified range with a second spatial resolution lower than the first spatial resolution and with a resolution on a second time axis higher than the first time axis resolution based on a result obtained by superimposing the results of the first detection and the second detection performed at time intervals by multiple small pixels with different phases from each other.

10. The optical distance measuring device according to any one of claims 1 to 3, wherein: The determination unit detects the spatial position of the object existing in the specified range with a resolution higher than the resolution using the pixel as a unit, based on a result obtained by superimposing the results of the first detection and the second detection performed at time intervals by a part of a plurality of small pixels whose phases are different from each other.

11. The optical distance measuring device according to claim 10, wherein: The number of the part of small pixels on which the results of the first detection and the second detection separated by the time interval are superimposed can be changed.

12. The optical distance measuring device according to claim 11, wherein: Before changing the number of superimposed small pixels, the first detection or the second detection is performed with the time interval between the emission of the pulse light and the use of the small pixels, and the number of superimposed small pixels is determined based on the result of the first detection or the second detection.

13. An optical distance measurement method that uses light to measure the distance to an object. In the optical ranging method, Emits pulsed light to a specified range. The reflected light from the predetermined range corresponding to the pulse light is imaged on a pixel for detection, wherein a plurality of small pixels capable of respectively detecting the reflected light are arranged in the pixel, At least a portion of the plurality of small pixels repeatedly perform a first detection of the reflected light at intervals of time, and the other small pixels repeatedly perform a second detection of the reflected light at intervals of time, in different phases. The result of the first detection and the result of the second detection repeatedly performed by each of the small pixels at the time interval are superimposed to determine the spatial position of the object including the distance to the object existing in the predetermined range.

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