JP7259525B2 - Optical ranging device and method - Google Patents

Description

The present disclosure relates to an object detection technology using light.

By irradiating pulsed light such as laser light, detecting the reflected light from the target with the light receiving part, and measuring the return time (TOF) from irradiation to light reception, it is possible to detect the presence or absence of the target and to detect the target. are known. In such devices, various devices have been devised to increase the resolution for catching an object (see Patent Documents 1 to 4, for example).

JP 2015-175644 A JP 2013-156139 A JP 2014-77658 A JP 2016-176721 A

However, the technique described in Patent Document 1 requires a stereo camera in addition to a distance measuring device using a TOF, which leads to an increase in the size and cost of the device configuration. Further, in the technique described in Patent Document 2, detection of objects is performed in an interlaced manner, so detection takes time and detection of small moving objects is difficult. Furthermore, in the technique described in Patent Document 3, high-sensitivity detection using an avalanche diode is possible, but improvement in resolution is not particularly devised.

The present disclosure relates to an optical distance measuring device that irradiates light to the outside and measures the distance to an object. This optical distance measuring device (20) includes a light emitting section (40) for emitting pulsed light to a predetermined range, and a light receiving surface (65) for reflecting light from the predetermined range corresponding to the pulsed light. an optical system (30) for imaging; and a plurality of light receiving circuits capable of individually detecting the reflected light as an electrical signal for each pixel (66), which is a unit for performing detection at a first resolution on the light receiving surface. (69) is arranged, and according to the result of detection of the reflected light by the light receiving circuit, the target reflected light corresponding to the target is calculated from the return time from the emission of the pulsed light, the predetermined and a specifying unit (110, 140, 150) for specifying the spatial position of the object including the distance to the object existing in the range of . In such an optical distance measuring device, the specifying unit combines a first result obtained by superimposing the outputs of the plurality of light receiving circuits arranged in the pixel and part of the plurality of light receiving circuits arranged in the pixel. and a second result obtained by superimposing the output of the light receiving circuit in the case of removing the object, from the return time of the object reflected light, the position of the object in the space is determined by a resolution higher than the first resolution. 2 resolution may be performed.

According to this optical distance measuring device, a plurality of light-receiving circuits capable of individually detecting reflected light as electrical signals are arranged for each pixel, which is a unit for detecting reflected light. A first result obtained by superimposing the outputs of the plurality of light receiving circuits arranged in each pixel, and a second result obtained by superimposing the outputs of the plurality of light receiving circuits arranged in the pixel except for some of the outputs. By comparing , it is possible to perform high-resolution identification processing with increased resolution of the position of the object. There may be a difference between the first result and the second result due to the removal of part of the light receiving circuit. can do.

1 is a schematic configuration diagram of an optical distance measuring device according to a first embodiment; FIG. Explanatory drawing which shows the detailed structure of an optical system. FIG. 3 is a block diagram showing the internal configuration of a SPAD calculation unit; FIG. 2 is an explanatory diagram showing an example of a SPAD circuit that constitutes a light receiving circuit; FIG. 10 is an explanatory diagram showing how peaks are detected by superimposing the detection results of each SPAD circuit; 4 is a flowchart showing processing for detecting an object and measuring a distance in pixel units. FIG. 4 is an explanatory diagram for explaining a partial pixel stopped in a light receiving element corresponding to a pixel; 4 is a flow chart showing an example of object detection/ranging processing in partial pixels. FIG. 5 is an explanatory diagram illustrating changes in peaks caused by stopping detection by partial pixels; Explanatory drawing which shows the mode of the peak detection by a difference histogram. 10 is a flowchart showing object detection and distance measurement processing in pixel units according to the second embodiment. 10 is a flowchart showing object detection/ranging processing for partial pixels in the second embodiment. FIG. 9 is an explanatory diagram showing how peak detection is performed in the second embodiment; 10 is a flowchart showing measurement processing in units of pixels as a third embodiment; Explanatory drawing which shows the case where several peaks are detected. Explanatory drawing which shows the case where several peaks were not detected. 14 is a flowchart showing measurement processing in units of pixels as a fourth embodiment; 14 is a flowchart illustrating object detection/ranging processing in pixels and partial pixels as a fourth embodiment; FIG. 4 is an explanatory diagram illustrating the relationship between two thresholds for a difference histogram; FIG. 4 is an explanatory diagram showing an example of a combination of two partial pixels; FIG. 11 is an explanatory diagram showing another example of a combination of two partial pixels; FIG. 4 is an explanatory diagram showing an example of a combination of four partial pixels; FIG. 4 is an explanatory diagram showing an example of a combination of two partial pixels that are not vertically and horizontally adjacent;

A. First embodiment:
(A1) Device configuration:
An optical distance measuring device 20, which is an optical device of the first embodiment, optically measures a distance, and as shown in FIG. An optical system 30 for projecting light for receiving reflected light, an optical system 30 for driving the optical system 30, and a SPAD calculation unit 100 for processing a signal obtained from the optical system 30 are provided. The optical system 30 includes a light emitting unit 40 that emits laser light, a scanning unit 50 that emits laser light from the light emitting unit 40 to a predetermined range for distance measurement and scans, and reflected light from the range scanned with the laser light. and a light receiving unit 60 for receiving the light.

Details of the optical system 30 are shown in FIG. As shown in the figure, the light emitting unit 40 includes a semiconductor laser element (hereinafter simply referred to as a laser element) 41 that emits laser light for distance measurement, a circuit board 43 incorporating a drive circuit for the laser element 41, A collimating lens 45 is provided to collimate the emitted laser light. The laser element 41 is a laser diode that can oscillate 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.

The scanning unit 50 includes a surface reflecting mirror 51 that reflects the laser beam collimated by the collimator lens 45, a holder 53 that rotatably holds the surface reflecting mirror 51 by a rotating shaft 54, and a rotary shaft that drives the rotating shaft 54 to rotate. A solenoid 55 is provided. The rotary solenoid 55 receives a control signal Sm from the outside and repeats forward and reverse rotation within a predetermined angle range (hereinafter referred to as the angle of view range). As a result, the rotary shaft 54 and, by extension, the surface reflecting mirror 51 also rotate within this range. As a result, the laser light incident from the laser element 41 through the collimator lens 45 is scanned in the horizontal direction (H direction) in the drawing within a predetermined angle of view. The rotary solenoid 55 incorporates an encoder (not shown) and can output its rotation angle. Therefore, the scanning position can be acquired by reading the rotation angle of the surface reflecting mirror 51 as the output of the encoder.

By driving the surface reflecting mirror 51 within a predetermined range, the laser light emitted from the light emitting section 40 is scanned in the horizontal direction (H direction). The laser element 41 has a shape elongated in a direction perpendicular to the H direction (hereinafter referred to as the V direction). The optical system 30 including the surface reflecting mirror 51 of the scanning unit 50 described above is housed in the housing 32, and the light emitted toward the object OBJ1 and the reflected light from the object OBJ1 are provided in the housing 32. passes through the closed cover 31. Light emitted toward the object OBJ1 and reflected from the object OBJ1 is denoted by RL1 in FIG.

The optical system 30 can perform distance measurement in a region defined by the height of the laser light in the V direction and the angle range in the H direction by the scanning unit 50 . If there is an object OBJ1 such as a person or a car, the laser beam output from the optical distance measuring device 20 toward this area is irregularly reflected by the surface of the object OBJ1. come back to This reflected light is reflected by the surface reflecting mirror 51 and enters the light receiving lens 61 of the light receiving section 60 . Reflected light condensed by the light receiving lens 61 enters a light receiving array 65 arranged on the light receiving surface.

The output signal from the light receiving array 65 of the light receiving section 60 is input to the SPAD calculation section 100 corresponding to the distance measuring section, as shown in FIG. While scanning the external space by causing the laser element 41 to emit light, the SPAD calculation unit 100 calculates the time TF from when the laser element 41 outputs an irradiation pulse to when the light receiving array 65 of the light receiving unit 60 receives the reflected light pulse. , to the object OBJ1. The SPAD calculation unit 100 includes a well-known CPU and memory, and executes a program prepared in advance to perform processing necessary for distance measurement. Specifically, the SPAD calculation unit 100 includes an addition unit 120, a histogram generation unit 130, a peak detection unit 140, a distance calculation unit 150, and the like, in addition to a control unit 110 that performs overall control.

The adding section 120 is a circuit that adds the outputs of the SPAD circuits 68 included in the light receiving elements 66 that constitute the light receiving section 60 . In this embodiment, the light receiving array 65 of the light receiving section 60 is composed of a plurality of light receiving elements 66 arranged in the V direction of the reflected light, as shown in FIG. The light receiving element 66 is a unit for detecting the object OBJ1 and measuring the distance to the object OBJ1 during distance measurement. The light receiving element 66 is also called a pixel.

Each light receiving element 66 is composed of 9×9 SPAD circuits 68 as shown in FIG. The 9.times.9 SPAD circuits 68 are grouped into 3.times.3 units, and the 3.times.3 units are grouped together so that their on/off can be controlled. As for the light receiving element 66 as a whole, in this embodiment, nine portions corresponding to light receiving circuits can be stopped individually. Each portion that can be stopped individually is called a partial pixel 69 in this embodiment, but the object OBJ1 is not detected for each partial pixel 69 alone, as will be described in detail later. The handling of signals from the 3×3 SPAD circuits 68 forming the partial pixel 69 will be described later.

The SPAD circuit 68 uses an avalanche photodiode (APD) that achieves high responsiveness and excellent detection capability. When reflected light (photons) is incident on the APD, electron-hole pairs are generated, and the electrons and holes are each accelerated in a high electric field, causing impact ionization one after another to generate new electron-hole pairs. (avalanche phenomenon). Since APDs can amplify incident photons in this way, APDs are often used when the intensity of reflected light is low, such as with distant objects. APD operating modes include a linear mode operating at a reverse bias voltage lower than the breakdown voltage and a Geiger mode operating at a reverse bias voltage equal to or higher than the breakdown voltage. In the linear mode, the number of electron-hole pairs exiting from the high electric field region and disappearing is greater than the number of generated electron-hole pairs, and the decay of electron-hole pairs stops spontaneously. Therefore, the output current from the APD is approximately proportional to the amount of incident light.

On the other hand, in the Geiger mode, the avalanche phenomenon can occur even when a single photon is incident, so the detection sensitivity can be further enhanced. An APD operated in such a Geiger mode is sometimes called a Single Photon Avalanche Diode (SPAD).

Each SPAD circuit 68, as shown in the equivalent circuit of FIG. 4, connects a quench resistor Rq and an avalanche diode Da in series between the power supply Vcc and the ground line, and the voltage at the connection point is one of the logic operation elements. is input to an inverting element INV, which is one of them, and converted into a digital signal whose voltage level is inverted. Since the output of the inverting element INV is connected to one input of the AND circuit SW, if the other input is at high level H, it is output to the outside as it is. The state of the other input of the AND circuit SW can be switched by the selection signal SC. The selection signal SC is collectively output to the 3×3 SPAD circuits 68 in the partial pixel 69, and specifies from which partial pixel 69 of the light receiving array 65 signals are to be read or not. used for If the avalanche diode Da is used in linear mode and its output is treated as an analog signal, an analog switch may be used instead of the AND circuit SW. Also, it is possible to use a PIN photodiode instead of the avalanche diode Da.

If no light is incident on the SPAD circuit 68, the avalanche diode Da remains non-conducting. Therefore, the input side of the inverting element INV is pulled up through the quench resistor Rq, that is, is maintained at the high level H. Therefore, the output of the inverting element INV is kept at low level L. When light is incident on each SPAD circuit 68 from the outside, the avalanche diode Da is energized by the incident light (photons). As a result, a large current flows through the quench resistor Rq, the input side of the inverting element INV temporarily becomes low level L, and the output of the inverting element INV is inverted to high level H. As a result of the large current flowing through the quench resistor Rq, the voltage applied to the avalanche diode Da drops, so that the power supply to the avalanche diode Da stops and the avalanche diode Da returns to the non-conducting state. As a result, the output signal of the inverting element INV is also inverted to return to the low level L. As a result, the inverting element INV outputs a pulse signal that becomes high level for a very short time when light (photon) is incident on each SPAD circuit 68 . Therefore, if the address signal SC is set to the high level H in accordance with 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 will be the output signal of the avalanche diode Da. It becomes a digital signal that reflects the state.

A total of 9 output signals Sout of the 3×3 SPAD circuits 68 included in the partial pixel 69 are supplied to a block prepared in the adder 120 as shown for one partial pixel 69 in FIG. It is input to the inner adder 121 and added. Therefore, the adder 120 is provided with nine intra-block adders 121 . When distinguishing the partial pixels 69, they are called partial pixels s1, s2, . . . s9 in order from the upper left partial pixel 69 toward the lower right. The outputs of the nine SPAD circuits 68 in each partial pixel 69 are combined by the intra-block adder 121, output to the histogram generator 130, and used to generate a histogram.

This state is illustrated in FIG. When the laser element 41 of the light emitting unit 40 is caused to emit light and the reflected light from the object OBJ1 is incident on the light receiving element 66 corresponding to one pixel arranged on the light receiving surface of the light receiving unit 60, each partial pixel 69 emits the reflected light. Outputs a pulse signal at the timing of reception. The partial pixel signal, which is the result of adding the signal Sout from the SPAD circuit 68 in each partial pixel s1, s2, . If the object OBJ1 is present at a position where the light receiving element 66 of the light receiving unit 60 receives the reflected light, the time TF until the laser element 41 receives the reflected light pulse based on the illumination pulse is substantially the same regardless of the partial pixel 69. become.

Therefore, when the histogram T is generated by adding the signals from the partial pixels s1, s2, . Due to the nature of the SPAD circuit 68, the output pulse signal also contains noise. Noise is randomly generated by ambient light such as sunlight. Since pulse signals due to noise are randomly generated, when the signals from partial pixels s1, s2, .

When the histogram generation unit 130 superimposes the signals from the partial pixels s1, s2, . A histogram is generated. The signals detected by the plurality of SPAD circuits 68 forming the light-receiving element 66 include noise due to ambient light and the like. When done, the signals corresponding to the reflected light pulses are accumulated and the signals corresponding to the noise are not accumulated so that the signals corresponding to the reflected light pulses are well defined. A so-called S/N ratio increases. Therefore, by analyzing the histogram from the histogram generator 130, the peak detector 140 detects the peak of the signal. The peak of the signal is nothing but the reflected light pulse from the object OBJ1 that is the target of distance measurement. When the peak is detected in this way, the distance calculator 150 detects the distance D to the object by measuring the time TF from the irradiation light pulse to the peak of the reflected light pulse. The detected distance D is output to an external device such as an automatic driving device if the optical distance measuring device 20 is installed in an automatic driving vehicle. Of course, it can also be used as a fixed distance measuring device in addition to mobile objects such as drones, automobiles, and ships.

The control unit 110 activates the command signal SL for determining the light emission timing of the laser element 41 to the circuit board 43 of the light emitting unit 40 and the nine SPAD circuits 68 included in each partial pixel 69 collectively. In addition to the address signal SC for determining whether or not to It outputs a driving signal Sm and the like for the rotary solenoid 55 . Control unit 110 outputs these signals at predetermined timings, so that SPAD calculation unit 100 functions as a specification unit that detects object OBJ1 existing within a predetermined range along with distance D to object OBJ1. The control unit 110 incorporates a memory 114 that stores histograms and the like generated in the process described later.

(A2) Details of distance measurement processing:
Next, details of distance measurement processing by the SPAD calculation unit 100 will be described with reference to FIG. 6 and subsequent drawings. The pixel unit measurement processing routine shown in FIG. 6 is repeatedly executed at predetermined intervals. When this processing routine starts, first, the processing of repeating steps S210 to s230 is performed for partial pixels s1 to s9 (steps S201s to S201e). In repeating this process, a variable s is used, and the variable s is incremented by 1 each time it is repeated. This also applies to other embodiments described below. In the first embodiment, steps S201s to S201e are repeated nine times from s=1 to 9.

In this process, first, all SPAD circuits 68 included in the partial pixel s are stopped (step S210). FIG. 7 is an explanatory diagram for explaining a partial pixel s stopped at the light receiving element 66 corresponding to the pixel. The light receiving element 66, which is a pixel, includes nine partial pixels s1 to s9 as shown in FIG. If s=1, sub-pixel s1 is deactivated. That is, the control unit 110 turns off the address signal SC for the partial pixel s1 and turns on the address signals SC for the partial pixels s2 to s9 other than the partial pixel s1. In this state, light emission/light reception processing is performed (step S220). That is, the laser element 41 of the light emitting section 40 is driven to emit an illumination pulse, and the reflected light is received by the light receiving element 66 of the light receiving section 60 .

As already described, the light receiving element 66 adds the pulses detected by the nine SPAD circuits 68 included in each partial pixel 69 by the intra-block adder 121, and repeats this operation multiple times to generate a histogram. A histogram Ts is generated by the unit 130 and sequentially stored in the memory 114 provided in the control unit 110 (step S230).

Control unit 110 repeats this operation from s1 to s9 while sequentially incrementing variable s. Therefore, when the nine iterations are completed (steps S201s to S201e), the memory 114 in the control unit 110 stores nine histograms T1 to T9.

When the repetition for the partial pixels s1 to s9 is completed (step S201e), then a cumulative histogram TT is created (step S240). The cumulative histogram TT is created by superimposing the histograms T1 to T9 created by stopping the partial pixels s1 to s9 and stored in the memory 114. FIG. Since the histograms T1 to T9 are created with one partial pixel s1 to s9 stopped, the number of partial pixels s1 to s9 included in the histograms T1 to T9 is eight. Therefore, the cumulative histogram TT will evenly contain data from all partial pixels.

Therefore, using this cumulative histogram TT, the detection and distance measurement processing of the object in the light receiving element 66, which is a pixel, is performed (step S310). Since the cumulative histogram TT is obtained by superimposing the detection results of all the partial pixels s1 to s9, this is equivalent to the detection and distance measurement of the object by the entire light receiving element 66, which is the pixel. . Peaks contained in the cumulative histogram TT are detected by comparing the cumulative histogram TT with a threshold. If the peak is found, it can be determined that there is an object OBJ1 that brings the reflected light to the light receiving section 60 . Also, by obtaining the peak time, the distance D to the object OBJ1 can be measured.

Following the object detection/ranging process in the pixel (light receiving element 66) using the cumulative histogram TT (step S310), the object detection/ranging process is carried out in partial pixels (step S410). The object detection and distance measurement processing (step S410) in this partial pixel will be described in detail with reference to FIGS. 8 and 9. FIG.

When the object detection/ranging process for partial pixels shown in FIG. 8 is started, preparations are first made to repeat the process for partial pixels s=1 to 9 (step S410s). The repeated processing is the following steps S412 to S415. First, a variable s specifying a partial pixel is set to a value of 1, and the cumulative histogram TT created in step S240 of FIG. 6 and the histogram Ts stored in step S230 of FIG. A process of obtaining a difference histogram ΔTs from the generated and stored histogram Ts is performed (step S412). This process can be expressed as a formula:
ΔTs = TT-8 · Ts
is. Referring to FIG. 7, this processing consists of a cumulative histogram TT obtained by accumulating histograms Ts generated by sequentially stopping (turning off) each partial pixel s (s=1 to 9) and performing light emission/light reception processing. , to determine the difference from the histogram Ts generated by stopping any of the partial pixels s. The reason why the histogram Ts is multiplied by 8 is to achieve normalization when obtaining the difference histogram. Since the cumulative histogram TT is obtained by accumulating the histogram Ts (s=1 to 9) generated by stopping any of the partial pixels s=1 to 9, the non-accumulated histogram is used when obtaining the difference histogram ΔTs. Multiply by 8 to normalize both. Although the cumulative histogram TT is obtained by accumulating the histogram Ts generated by stopping the partial pixels s nine times, the accumulation of data for each partial pixel is performed only eight times.
ΔTs = TT-8 · Ts
However, multiplication by a factor of 2 or more, such as 7 times or 9 times, can reduce the difference in size between the cumulative histogram and the normal histogram.

A high-resolution specifying process using the difference histogram Ts will be described. As shown in FIG. 9, reflected light from an object OBJ1 is incident on the entire light-receiving element 66, and a small light existing at a different distance from the object OBJ1 exists in a portion corresponding to the partial pixel s=9. Assume that reflected light from object OBJ2 is incident. Then, as shown in the top row of FIG. 9, the histogram T1 generated by stopping the partial pixel s=1 becomes a histogram in which the signals from the partial pixels s (s=2 to 9) are superimposed, and the object OBJ1 There will be a peak based on the reflected light from the object OBJ2 and a peak based on the reflected light from the object OBJ2.

These two peaks are similarly detected when any of the partial pixels s (s=1 to 8) is stopped. On the other hand, since the cumulative histogram TT is obtained by superimposing these histograms Ts (s=1 to 9), it is a histogram having two peaks as shown at the bottom of FIG. Therefore, the difference histogram,
ΔTs = TT-8 · Ts
When s=1 to 8, there is no peak in the difference histogram. Whether or not a peak exists can be easily detected by comparing the difference histogram ΔTs with the difference threshold ΔTn (step S413).

If it is determined in step S413 that there is no peak exceeding the difference threshold value ΔTn in the difference histogram ΔTs, it is determined that no object exists in that partial pixel s (step S415). On the other hand, if there is a peak exceeding the difference threshold ΔTn in the difference histogram ΔTs (step S413: “YES”), it is determined that the object OBJ2 exists in the partial pixel s, and the position of the object OBJ2 is detected and the distance to the peak is detected. Distance measurement based on time is performed (step S414).

The difference histogram ΔTs has a peak exceeding the difference threshold ΔTn when the histogram Ts is generated by stopping the partial pixel s=9 in FIG. 9 and the difference histogram ΔTs is obtained. In this case, since the partial pixel s=9 is stopped, the reflected light from the object OBJ2 that was detected by the partial pixel s is not detected. As shown, the peak corresponding to object OBJ2 disappears. Therefore, as shown in FIG. 10, when the histogram T9 when the partial pixel s=9 is stopped is subtracted from the cumulative histogram TT to find the difference histogram ΔTs, the peak corresponding to the object OBJ2 remains. A peak corresponding to the object OBJ2 is detected as a peak exceeding the threshold ΔTn. Therefore, detection of the object OBJ2 and distance measurement based on the time to peak are possible.

By repeating the above processing for partial pixel s from s=1 to 9 (steps S410s to S410e), if reflected light from an object enters each partial pixel s, it can be detected. Therefore, according to the optical distance measuring device 20 of the first embodiment, the light receiving elements 66 constituting the light receiving array 65 can be used as pixels, which are units of object detection, to not only detect and measure an object, but also to configure the light receiving elements 66. Object detection is possible with partial pixels s=1 to 9. In other words, the object can be detected with a resolution (second resolution) higher than the resolution (first resolution) of the pixel that uses the light receiving element 66 as a unit of detection. Moreover, in the first embodiment, the histogram is not generated in a state where all the partial pixels s are operated, but the generated histograms T1 to T9 are stored and superimposed to obtain the cumulative histogram TT. . Therefore, it is not necessary to find the histogram of the entire light receiving element 66, which is a pixel. Further, in the above-described embodiment, the histogram Ts is normalized when obtaining the difference histogram ΔTs. can be high enough.

B. Second embodiment:
The optical distance measuring device 20 of the second embodiment has the same hardware configuration as that of the first embodiment, and differs only in object detection and distance measurement processing by the controller 110 of the SPAD calculator 100 . Particularly, in the second embodiment, the pixel unit measurement processing routine and the partial pixel object detection/distance measurement processing routine are different. Each processing routine of the second embodiment is shown in FIGS. 11 and 12. FIG. In each processing routine, the same step numbers are assigned to the same processes as in the first embodiment. Therefore, the description of these processes is simplified.

The pixel unit measurement processing routine shown in FIG. 11 is repeatedly executed at predetermined intervals. When this processing routine is started, the content of the cumulative histogram TT is once reset and emptied (step S200). After that, the process of repeating steps S210 to S420 is performed for the partial pixel s (variable s=0 to 9) (steps S202s to S202e). In this process, the variable s is incremented by 1 each time it is repeated, and steps S202s to S202e are repeated from 0 to 9 for the variable s.

In this process, as in the first embodiment, the SPAD circuit 68 included in the partial pixel s is stopped (step S210). However, unlike the first embodiment, s=0 at first, that is, all the partial pixels s are operated. In this state, light emission/light reception processing is performed (step S220). That is, the laser element 41 of the light emitting section 40 is driven to emit an illumination pulse, and the reflected light is received by the light receiving element 66 of the light receiving section 60 .

As already described, the light receiving element 66 adds the pulses detected by the nine SPAD circuits 68 included in each partial pixel 69 by the intra-block adder 121, and repeats this operation multiple times to generate a histogram. A histogram Ts is generated by the unit 130 and stored in the memory 114 provided in the control unit 110 (step S232). Here, the histogram T0 when the variable s=0 is a histogram when all the partial pixels s (s=1 to 9) forming the pixel are in motion. Therefore, this histogram T0 is called a pixel histogram T0. Further, processing is performed to add the generated histogram Ts to the cumulative histogram TT whose content has been reset in step S200 (step S242). As a result, when s=0, the content of the cumulative histogram TT becomes a histogram when all the partial pixels s are in operation.

After that, it is determined whether or not the variable s indicating the number of iterations is 0 (step S252). Step S262) and the processing from step S210 are repeated. At this time, since the variable s has been incremented by 1, by executing steps S210 to S232, the histogram Ts is generated with the partial pixels s=1 to 9 stopped (steps S210 to S232). , are sequentially added to the cumulative histogram TT (step S242).

If the variable s indicating the position of the partial pixel has a value of 1 to 9, the determination in step S252 becomes "NO", and object detection and distance measurement processing is performed in the partial pixel (step S420). The object detection and distance measurement processing in this partial pixel will be described with reference to FIG. 12 .

When the object detection/ranging process for partial pixels is started, as shown in FIG. 12, first, the process for obtaining the difference histogram Ts is performed (step S412). This process
ΔTs←T0−k・Ts
The difference between the pixel histogram T0 stored in the memory 1 and the histogram Ts for the s-th partial pixel is the pixel histogram T0 when the variable s=0 shown in step S262 of FIG. This is a process that takes The pixel histogram T0 is a histogram when all partial pixels s=1 to 9 are operating. Also, k is a coefficient for normalization. In this embodiment, when the variable s=1 to 9, one of the partial pixels s is stopped, so the number of partial pixels involved in the generation of the histogram Ts is eight. When the variable s=0, the nine partial pixels forming the pixel are involved in the generation of the pixel histogram T0, so both are normalized when obtaining the difference. In this example, k=9/8. Note that if two partial pixels s are stopped when obtaining the histogram Ts, the coefficient k should be 9/7. Furthermore, the coefficient k should be set so that the pixel histogram T0 and each histogram Ts are closer to each other.

After obtaining the difference histogram ΔTs in this way, it is then determined whether or not there is a peak exceeding the difference threshold ΔTn in the difference histogram ΔTs (step S413).

For example, as shown in FIG. 13, reflected light from an object OBJ1 is incident on the entire light-receiving element 66, and the portion corresponding to the partial pixel s=9 exists at a different distance from the object OBJ1. Assume that reflected light is incident from a small object OBJ2. Then, as shown in the top row of FIG. 13, the pixel histogram T0 generated when s=0, that is, when not even a single partial pixel is stopped, is obtained by adding the signals from the partial pixels s=1 to 9. Thus, there are a peak based on the reflected light from the object OBJ1 and a peak based on the reflected light from the object OBJ2.

These two peaks are similarly detected when any of the partial pixels s (s=1 to 8) is stopped. Whether or not a peak exists can be easily detected by comparing the difference histogram ΔTs with the difference threshold ΔTn (step S413 described above).

If it is determined in step S413 that there is no peak exceeding the difference threshold value ΔTn in the difference histogram ΔTs, it is determined that no object exists in that partial pixel s (step S415). For example, as shown in the bottom of FIG. 13, when the difference histogram ΔT1 is obtained for the histogram T1 when partial pixel s=1 is stopped, no peak (ΔTs>ΔTn) is found. On the other hand, if there is a peak exceeding the difference threshold ΔTn in the difference histogram ΔTs (step S413: "YES"), it is determined that the object OBJ2 exists in the partial pixel s. For example, when the partial pixel s=9 shown in FIG. 13 is stopped, the histogram T9 does not have a peak due to the object OBJ2, so a peak appears in the difference histogram ΔT9. Therefore, by comparing the difference histogram ΔT9 with the difference threshold ΔTn, the existence of the object OBJ2 can be detected. In this case, it can be seen that the object OBJ2 exists at the position corresponding to the stopped partial pixel s. Therefore, in this case, detection of the position of the object OBJ2 and distance measurement based on the time to the peak are performed (step S414).

In this way, the variable s indicating the partial pixel is set to a value of 0 to 9, and when this is completed (step S202e), object detection and distance measurement are performed for the entire pixels (step S320). In the second embodiment, since the histogram Ts is sequentially accumulated to obtain the cumulative histogram TT (step S242), it is possible to detect an object in all pixels and to measure the distance to that object. can. Note that the pixel histogram T0 when all the partial pixels s=1 to 9 are turned on is also obtained and stored in the area 1 of the memory 114. Using this, object detection and distance measurement processing in the entire pixels are performed. and may be performed. The use of the cumulative histogram TT makes it possible to increase the S/N ratio and the accuracy of detection, since multiple detections are repeated.

According to the optical distance measuring device 20 of the second embodiment described above, similarly to the first embodiment, the light-receiving elements 66 constituting the light-receiving array 65 are used as pixels, which are units of object detection, and the object is detected at the first resolution. , and the partial pixels s=1 to 9 forming the light receiving element 66 enable object detection at a second resolution higher than the first resolution. Moreover, in the second embodiment, since it is not necessary to store all the histograms when the partial pixels s=1 to 9 are turned off, the capacity of the memory 114 can be reduced. In addition, in the above embodiment, since the histogram Ts is normalized when obtaining the difference histogram ΔTs, it is possible to sufficiently improve the accuracy of peak detection by the difference histogram ΔTs.

C. Third embodiment:
The optical distance measuring device 20 of the third embodiment has the same hardware configuration as that of the first embodiment, and differs only in object detection and distance measurement processing by the controller 110 of the SPAD calculator 100 . The third embodiment differs from the first and second embodiments in that it is determined whether there are multiple peaks, and if it is determined that there are multiple peaks, high-resolution detection and ranging are performed. . An outline of processing in the third embodiment is shown in FIG.

The pixel unit measurement processing routine shown in FIG. 14 is repeatedly executed at predetermined intervals. When this processing routine starts, first, all partial pixels s=1 to 9 are turned on (step S510), and light emission/light reception processing is performed (step S520). In the light receiving process, the reflected light generated by the irradiation of the laser light is detected, and the pixel histogram T0 is created (step S530). It is determined whether or not the pixel histogram T0 created by turning on all the partial pixels s=1 to 9 included in the light receiving element 66 has a plurality of peaks (step S540).

Figures 15 and 16 illustrate the cases with and without multiple peaks. If there are two or more objects at different distances from the optical distance measuring device 20 in the range irradiated with the laser beam, and the reflected light from both objects is received at different positions of the same light receiving element 66, FIG. As shown, two or more peaks appear at different positions on the time axis, ie return times. In this case, high-resolution detection/ranging processing is performed to detect the position and distance of an object corresponding to two or more peaks (step S600). The process of step S600 corresponds to the process of the first or second embodiment.

On the other hand, if there is only one object in the range irradiated with the laser beam by the light emitting unit 40, and only the light reflected from this object is received by the light receiving element 66, then the time axis as shown in FIG. A single peak appears at the top. In this case, detection and distance measurement processing (step S620) is performed at the first resolution to detect the position and distance of the object corresponding to the peak. In step S620, object detection and distance measurement are performed based on a single peak included in the pixel histogram T0 obtained in step S530.

In the third embodiment described above, first, it is determined whether or not a plurality of peaks exist in the histogram of the entire pixels. do On the other hand, when a plurality of peaks exist, object detection and distance measurement processing are performed in units of partial pixels as described in the first and second embodiments, that is, at a second resolution higher than the first resolution. and Therefore, if multiple peaks do not exist, the processing can be completed within a short period of time. Object detection and ranging can also be performed at a second higher resolution if desired.

D. Fourth embodiment:
The optical distance measuring device 20 of the fourth embodiment has the same hardware configuration as those of the first to third embodiments, and differs only in object detection and distance measurement processing by the controller 110 of the SPAD calculator 100 . In the fourth embodiment, the method of determining the peak of the difference histogram is different from that in the previous examples. 17 and 18 show object detection and distance measurement processing in the fourth embodiment.

The processing shown in FIG. 17 is repeatedly executed at predetermined intervals. This processing routine is the same as the processing of the first embodiment (steps S201s to S201e and step S240 in FIG. 6) except for the final step S700. When these processes are completed, the histograms T1 to T9 of each partial pixel s (s=1 to 9) shown in FIG. Then, the SPAD calculation unit 100 executes the process of step S700, that is, the object detection/distance measurement process in pixels and partial pixels. Details of this process are shown in FIG.

When the processing shown in FIG. 18 is started, the following processing is repeated for all partial pixels s (s=1 to 9) (steps S710s to S710e). In the repetitive process, first, a difference histogram ΔTs is obtained (step S712). The difference histogram ΔTs is
ΔTs = TT-8 · Ts
Ask as This is the same processing as the derivation of the difference histogram ΔTs (FIG. 8, step S412) in the first embodiment. Next, the relationship between the peak of the difference histogram ΔTs and the two threshold values TH and TL is compared and determined (step S713). The difference histogram ΔTs is a histogram that extracts the peak when the reflected light from the object is incident on the partial pixel s by turning off the partial pixel s, as already described in other embodiments. is.

As for the threshold TH and the threshold TL for comparing the difference histogram ΔTs, as shown in FIG. 19, the threshold TH is larger than the threshold TL. The threshold value TH is a threshold value that is set such that if the peak of the difference histogram ΔTs is equal to or higher than this value, it can be judged that the object has been detected. On the other hand, the threshold value TL is a threshold value that is set such that if the peak of the difference histogram ΔTs is equal to or less than this value, it can be judged that the peak is not detected as an object. As illustrated in FIG. 19, the range from the thresholds TL to TH is a range including cases where an object is detected and cases where the peaks within this range are noise. A peak in the range of thresholds TL to TH may be an object detection peak or simply noise.

Therefore, in the present embodiment, it is determined what kind of relationship the peak of the difference histogram ΔTs has with the thresholds TH and TL (step S713). If the peak of the difference histogram ΔTs is equal to or greater than the threshold TH, it can be determined that the peak is due to reflected light reflected by an object present at the location corresponding to the partial pixel s. Therefore, by using the difference histogram ΔTs, an object is detected at the position corresponding to the partial pixel s, and the distance to the object is measured from the position of the peak of the difference histogram ΔTs on the time axis ( step S715).

After that, all partial pixels s (s=1 to 9) are turned on to perform light emission/light reception processing, and the obtained histograms are accumulated to generate a cumulative histogram TT again. An object to be used as a unit is detected and the distance is measured (step S716). Since the cumulative histogram TT has already been obtained once, object detection and distance measurement in units of pixels may be performed using the cumulative histogram TT. Since it is secured, there is a margin for the processing time when the difference histogram ΔTs is higher than the threshold TH. Therefore, in the present embodiment, the cumulative histogram TT is obtained again to make a reliable judgment.

On the other hand, if the peak of the difference histogram ΔTs is equal to or less than the threshold value TL in the determination in step S713, it can be determined that there is no object in the partial pixel s. That is, the processing of object detection and distance measurement is executed in units of pixels.

If it is determined in step S713 that the peak of the difference histogram ΔTs is greater than the threshold TL and less than the threshold TH, a cumulative histogram TT is generated in the same manner as in step S716, and an object is detected in units of pixels. and distance measurement (step S718), furthermore, light emission/light reception processing is performed while only the partial pixel s is stopped to generate a cumulative histogram (hereinafter referred to as a partial cumulative histogram) for the partial pixels, and in step S718 The difference histogram ΔTs with the obtained cumulative histogram TT is updated, and based on this difference histogram ΔTs, the detection and distance measurement of the object in the partial pixel s are performed (step S719). The partial cumulative histogram obtained in this process is obtained by performing the light emitting/light receiving process more times than the number of partial pixels s to be stopped (here, nine). Therefore, the differential histogram ΔTs obtained in step S719 has a higher S/N ratio than the differential histogram ΔTs shown in FIG. Therefore, if the object is located at the position corresponding to the partial pixel s, the probability of being able to detect it increases.

Of course, in the process of step S719, if the updated difference histogram ΔTs does not exceed the threshold TH, it is determined that there is no object, and the detection and distance measurement are not performed. In step S719, not only is the cumulative histogram TT determined again, but also the histogram Ts for the partial pixels s is generated more times than the number of partial pixels, and the partial cumulative histograms are obtained by accumulating them. is updated, if there is an object at the position corresponding to the partial pixel s, there is a high possibility that the peak will be equal to or greater than the threshold TH and detected. Even if the difference histogram ΔTs is obtained after obtaining the partial cumulative histogram, if the peak is less than the threshold value TH, it is determined that the peak is due to noise, and the detection of the object and the distance measurement are not performed. Naturally.

The above-described repetitive processing (processing from steps S710s to S710e) is repeated while sequentially moving the partial pixel s, and when all the partial pixels have been determined, the process exits to "NEXT" and ends this routine. .

According to the fourth embodiment described above, the same effects as those of the first to third embodiments can be obtained. If it cannot be determined that there is no object, the cumulative histogram TT is generated again, and the partial cumulative histogram is obtained to update the difference histogram ΔTs. , the detection of the position of an object and the ranging to the object can be performed. Therefore, it is possible to reliably determine whether a peak appearing in the histogram is due to noise or a small object.

E. Other embodiments:
In each of the above-described embodiments, the difference histogram ΔTs is obtained as the difference between the cumulative histogram TT and the histogram Ts when one partial pixel s is stopped. In addition, it is possible to obtain a difference histogram from the cumulative histogram TT. For example, among histograms Ts (s=1 to 9) obtained by sequentially turning off partial pixels s1 to s9, as shown in FIG. The group histogram Tu may be obtained collectively in the direction, and the difference histogram ΔTu between the cumulative histogram TT and the group histogram Tu may be obtained. In the example shown in FIG. 20, two histograms Ts1 to Ts9 are combined to form group u. Specifically, the group histogram Tu is
Tu1: Ts1 + Ts4
Tu2: Ts2 + Ts5
Tu3: Ts3+Ts6
Tu4: Ts4 + Ts7
Tu5: Ts5 + Ts8
Tu6: Ts6 + Ts9
Ask as The two histograms that are combined correspond to the case where the partial pixels that were turned off in generating the histograms are vertically adjacent. A difference histogram ΔTu between each group histogram Tu and the cumulative histogram TT is obtained, and it is determined whether or not an object exists in the group based on whether or not the difference histogram ΔTu includes a peak larger than the threshold. Therefore, the group histogram can be used to detect small objects, minute parts of objects, etc. at a second resolution that is higher than the first resolution, which is a pixel-by-pixel resolution. When obtaining the difference histogram ΔTu, it is preferable to obtain the difference after normalization, as in the above-described embodiment.

By adopting such a configuration, it is possible to increase the resolution of object detection, and to detect an object existing across positions corresponding to two partial pixels with high precision, as in the above-described embodiments. . Also, there is no need to change the process of generating a histogram with partial pixels turned off.

When the histograms are superimposed and grouped, as shown in FIG. 21, the two histograms to be combined are selected corresponding to the case where the partial pixels that were turned off when generating the histograms are horizontally adjacent. may In the example shown in FIG. 21, the histograms Ts1 to Ts9 are combined differently from the example shown in FIG. 20, and the group histogram Tv is obtained as follows.
Tv1: Ts1 + Ts2
Tv2: Ts2 + Ts3
Tv3: Ts4 + Ts5
Tv4: Ts5 + Ts6
Tv5: Ts7 + Ts8
Tv6: Ts8 + Ts9
The method of object position detection and distance measurement is the same as that shown in FIG. When the group histogram Tv is configured in this way, it can be said that detection is easy when the objects are arranged in the horizontal direction of the light receiving element 66 . It should be noted that both the cases of groups u1 to u6 and the cases of groups v1 to v6 may be performed.

The histogram Ts obtained by turning off the partial pixels is not limited to the case of grouping by two, and may be grouped by M (M≧3). FIG. 22 exemplifies the case of grouping by four. In this case, four histograms Ts1 to Ts9 are combined to obtain the group histogram Tw. Specifically, the group histogram Tw is
Tw1=Ts1+Ts2+Ts4+Ts5
Tw2=Ts2+Ts3+Ts5+Ts6
Tw3=Ts4+Ts5+Ts7+Ts8
Tw4=Ts5+Ts6+Ts8+Ts9
Ask as The processing of obtaining the group histogram Tw, detecting an object with high resolution, and measuring the distance is the same as in other embodiments.

Grouping of partial pixels is not necessarily limited to vertically and horizontally adjacent ones. For example, as shown in FIG. 23, histograms Ts1 to Ts9 obtained by turning off partial pixels may be superimposed to obtain a group histogram Tx as follows.
Tx1: Ts1 + Ts5
Tx2: Ts2+Ts4
Tx3: Ts2+Ts6
Tx4: Ts3+Ts5
Tx5: Ts4 + Ts8
Tx6: Ts5+Ts7
Tx7: Ts5 + Ts9
Tx8: Ts6+Ts8
The method of object position detection and ranging is the same as in other forms. When obtaining the group histogram Tx as described above, it can be said that detection is easy when the object is tilted with respect to the vertical and horizontal arrangement of the light receiving elements 66 . The position detection and distance measurement for other groups and the position detection and distance measurement for groups x1 to x8 may be combined. This increases the possibility of detecting small objects that can only be detected by high-resolution detection and ranging techniques, even if they exist in vertical, horizontal, or diagonal directions. As for the oblique combination, the number of histograms to be superimposed may be set to M (M≧3).

In the above-described first to fourth embodiments and other embodiments, in addition to the detection that the size of the pixel (light receiving element 66) is lewd, the SPAD circuit 68 size and the SPAD size of the SPAD circuit 68 are detected by high resolution specific processing. High-resolution detection corresponding to the size of a combination of a plurality of circuits 68 can be performed. Detection by such high-resolution specific processing may be used for detecting an object different from detection performed in units of pixels, or may be used for detecting the shape of a portion of the same object at high resolution. good.

In the above embodiment, 3×3 partial pixels 69 corresponding to the light receiving circuit are provided for each light receiving element 66, but a different number such as 4×4 may be used. Of course, it is not necessary to have the same number of vertical and horizontal sides, and it is sufficient if the number is p×q (where p and q are integers of 1 or more, but p×q is 2 or more). In the above embodiment, one partial pixel 69 incorporates 3×3 SPAD circuits 68, and the intra-block adder 121 adds the outputs of the 3×3 SPAD circuits 68. The number of SPAD circuits 68 constituting the pixel 69 may be any number as long as it is one or more.

In the above embodiment, the high-resolution processing is performed by superimposing the detection result (first result) obtained by turning on all the partial pixels s=1 to 9 and by turning off some of the partial pixels. By taking the difference from the combined detection result (second result), the spatial position of the object was specified with high resolution. Identification may be performed at high resolution.

In addition, the present disclosure can be implemented in the following aspects.
(1) A first aspect is an aspect as an optical distance measuring device that irradiates light to the outside and measures the distance to an object. This optical distance measuring device includes a light emitting unit that emits pulsed light to a predetermined range, an optical system that forms an image of reflected light from the predetermined range corresponding to the pulsed light on a light receiving surface, and the light receiving surface. a light-receiving unit in which a plurality of light-receiving circuits capable of individually detecting the reflected light as electrical signals are arranged for each pixel, which is a unit for performing detection at a first resolution; A spatial position of the object, including a distance to the object existing within the predetermined range, is calculated from the return time of the object reflected light corresponding to the object from the emission of the pulsed light, according to the detection result. and a specifying part for specifying. Here, the specifying unit includes a first result obtained by superimposing the outputs of the plurality of light receiving circuits arranged in the pixel, and the result obtained by excluding some of the plurality of light receiving circuits arranged in the pixel. the position of the object in the space from the return time of the object reflected light at a second resolution higher than the first resolution, based on a second result obtained by superimposing the output of the light receiving circuit; A high-resolution identification process to identify may be performed. In this way, the spatial position of the object can be specified with increased resolution from the return time of the object reflected light from the object.

(2) Such an optical distance measuring device further includes a storage unit that stores the second result in association with the position of the removed light receiving circuit, and the specifying unit performs the above high resolution specifying process as the high resolution specifying process. The spatial position of the object is specified at the first resolution from the return time at which the first result obtained by superimposing the detection results of the plurality of light receiving circuits is larger than a predetermined first threshold. and generating a difference between the first result and the second result stored in the storage unit in association with the position of the removed light receiving circuit, and the difference is a predetermined second threshold value. A position in space corresponding to the position of the removed light receiving circuit may be identified at the second resolution by the larger return time. In this way, it is possible to easily realize object detection and distance measurement at the first resolution corresponding to the pixels and object detection and distance measurement at the second resolution corresponding to the size of the removed light receiving circuit. can. Here, the second resolution is higher than the first resolution. By removing one light receiving circuit, the resolution can be increased to the size of the light receiving circuit. When a plurality of light receiving circuits are removed, the direction of arrangement of the light receiving circuits can be freely combined as required, such as vertically, horizontally, and diagonally.

(3) In such an optical distance measuring device, the specifying unit performs the high-resolution specifying process, wherein the first result obtained by superimposing the detection results of the plurality of light receiving circuits is larger than a predetermined first threshold. from the return time, the spatial position of the object is specified at the first resolution corresponding to the pixel, and some of the plurality of light receiving circuits are sequentially removed by changing the positions of the light receiving circuits. The result of superimposing the outputs of the remaining light receiving circuits in each case is stored in a storage unit in association with the difference in position of the removed light receiving circuit, and is associated with the difference in position of the removed light receiving circuit. A result obtained by combining at least two of the stored superimposed results is generated as the second result, and a difference between the first result and the second result is associated with the combination. generating a position in space corresponding to the position of the light receiving circuit excluded by the combination by the return time at which the difference is larger than a predetermined second threshold, at a position in space higher than the first resolution; 2 resolution may be specified. By doing so, it is possible to accurately and easily detect an object existing across a plurality of light receiving circuits.

(4) In such an optical distance measuring device, when the specifying unit determines from the first result that there are a plurality of return times greater than the predetermined first threshold value, the high-resolution specifying process If it is not determined that there are a plurality of positions by performing the identification by the second resolution, the identification by the second resolution by the high resolution identification processing may not be performed. In this way, the high-resolution specifying process is not performed when there are not a plurality of return times greater than the first threshold value, so the time required for the process can be partially shortened.

(5) In such an optical distance measuring device, the emission of the pulsed light by the light-emitting section and the detection of the reflected light by the plurality of light-receiving circuits of the light-receiving section are repeated multiple times, and the specifying section has a high resolution. As the specific processing, each of the second results obtained when some of the plurality of light receiving circuits are sequentially removed by changing the position of the light receiving circuits of the plurality of light receiving circuits each time the repetition is performed, and the removed part of the light receiving circuits are obtained. and sequentially stored in a storage unit in association with the position of the object, and the spatial position of the object from the return time at which the accumulated result of accumulating the respective stored second results becomes larger than a predetermined first threshold value is specified at a first resolution corresponding to the pixel, a difference between the accumulated result and the stored second result is obtained, and if the difference is larger than a predetermined second threshold, the Assuming that target reflected light from a position in space corresponding to the position of the removed light receiving circuit exists, the return time in which the difference is greater than the second threshold determines the space corresponding to the position of the removed light receiving circuit. The upper position may be specified at a second resolution higher than the first resolution. By doing so, it is not necessary to obtain the result when all the plurality of light receiving circuits are operated, and the processing can be simplified.

(6) In such an optical distance measuring device, the emission of the pulsed light by the light-emitting section and the detection of the reflected light by the plurality of light-receiving circuits of the light-receiving section are repeated a plurality of times, and the specifying section has a high resolution. As the specific processing, in the first iteration, the first result obtained by superimposing the outputs of the plurality of light receiving circuits is obtained and stored in a storage unit (114), and the first result is determined in advance. If it is larger than the first threshold, the position in space corresponding to the position of the pixel is specified by the position of the return time of the target reflected light at the first resolution corresponding to the pixel, and the second and subsequent times Each time it is repeated, the difference between the second result and the first result stored in the storage unit is obtained when the positions of the light receiving circuits of the plurality of light receiving circuits are changed and sequentially removed. , a position in space corresponding to the position of the removed photodetector circuit may be identified at a second resolution higher than the first resolution from the return time at which the difference is greater than the second threshold. This eliminates the need to individually store the second results obtained when part of the light-receiving circuits are sequentially removed, thereby reducing the storage capacity.

(7) In such an optical distance measuring device, the emission of the pulsed light by the light-emitting section and the detection of the reflected light by the plurality of light-receiving circuits of the light-receiving section are repeated a plurality of times, and the specifying section has a high resolution. As the specific processing, in the first iteration, the first result obtained by superimposing the outputs of the plurality of light receiving circuits is obtained and stored in a storage unit, and each time the iteration is performed from the second time onward, The second result obtained when some of the plurality of light receiving circuits are sequentially removed by changing the position of the light receiving circuit is included in the first result and stored as an accumulated result, and after completion of the plurality of repetitions, From the return time at which the cumulative result becomes larger than a predetermined first threshold, the spatial position of the object is specified at a first resolution corresponding to the pixel, and the second and subsequent repetitions are performed. Then, the difference between the first result and the second result stored in the storage unit is obtained, and the position of the removed light receiving circuit corresponds to the return time when the difference is larger than the second threshold. A spatial position to be detected may be identified by a second resolution higher than the first resolution. By doing this, when the spatial position of the object is obtained at the first resolution corresponding to the pixel, the accumulated result is used, so that the accuracy can be improved.

(8) In the specifying unit, the number of times the light receiving circuits are overlapped when some of the plurality of light receiving circuits are excluded when obtaining the second result may be equal to or greater than the total number of the light receiving circuits. In this way, the number of superpositions is equal to or greater than the total number of light receiving circuits, so the S/N ratio can be increased, and the object can be detected more reliably in the high-resolution identification process.

(9) normalizing the second result with respect to the first result when specifying the position of the object in the space based on the accumulated result and the second result. It is also preferable to In this way, the difference can be obtained under the same conditions even if the cumulative number of times is different.

(10) Each of the plurality of light receiving circuits may be excluded one or more times when obtaining the second result. The number of times of removal may be two or more, and may differ for each light receiving circuit. By doing so, it is possible to flexibly change the contents of the high-resolution specifying process and specify the spatial position of the object from the return time of the target reflected light.

(11) The number of times the plurality of light receiving circuits are removed may be the same. This simplifies the processing.

(12) When superimposing the outputs of the light receiving circuits when some of the plurality of light receiving circuits are removed, the operation of the removed light receiving circuits may be stopped. In this way, the energy required for light reception can be reduced. Of course, it is also possible to have a structure in which the operation of the light-receiving circuit is continued and the output is not superimposed, or a structure in which superimposition is performed and the result is not used. In such a case, there is no need to change the operation of the light receiving circuit, and the processing can be simplified. In line with FIG. 4, the address signal SC may be turned off, and the power supply Vcc that supplies current to the avalanche diode Da via the quench resistor Rq may be turned off. Alternatively, the operation or output of intra-block adder 121 may be turned off.

(13) In such an optical distance measuring device, the specifying of the position in the space of the object based on the first result and the second result is based on the first result and the second result. may be done by comparing In this way, the difference between the two can be easily recognized, and high-resolution processing can be performed.

(14) A second aspect of the present disclosure is an aspect as an optical ranging method that measures the distance to an object by irradiating light to the outside. In this optical distance measuring method, pulsed light is emitted to a predetermined range, reflected light from the predetermined range corresponding to the pulsed light is formed on a light receiving surface, and a first resolution is obtained on the light receiving surface. A plurality of light-receiving circuits capable of individually detecting the reflected light are arranged for each pixel, which is a unit of detection in the light-receiving circuit, and the target reflected light corresponding to the object is detected according to the result of detection of the reflected light by the light-receiving circuit. , when specifying the spatial position of the object including the distance to the object existing in the predetermined range from the return time from the emission of the pulsed light, arranged in one pixel of the light receiving surface A first result obtained by superimposing the outputs of the plurality of light receiving circuits arranged in the pixel and a second result obtained by superimposing the outputs of the plurality of light receiving circuits when part of the plurality of light receiving circuits arranged in the pixel are excluded. and the position of the object in the space is identified at a second resolution higher than the first resolution from the return time of the reflected light from the object. According to this method, as with the above-described optical distance measuring device, it is possible to perform high-resolution identification processing with increased resolution of the position of the object. As a result, the spatial position of the object can be specified with high resolution by the return time of the object reflected light from the object.

(15) In each of the above embodiments, part of the configuration implemented by hardware may be replaced by software. At least part of the configuration implemented by software can also be implemented by a discrete circuit configuration. In addition, when part or all of the functions of the present disclosure are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. "Computer-readable recording medium" means not only portable recording media such as flexible disks and CD-ROMs, but also various internal storage devices such as RAM and ROM, and fixed to computers such as hard disks. It also includes an external storage device. That is, the term "computer-readable recording medium" has a broad meaning including any recording medium on which data and programs can be fixed rather than temporarily.

The present disclosure is not limited to the embodiments described above, and can be implemented in various configurations without departing from the scope of the present disclosure. For example, the technical features in the embodiments corresponding to the technical features in the respective modes described in the Summary of the Invention column may be used to solve some or all of the above problems, or Substitutions and combinations may be made as appropriate to achieve part or all. Also, if the technical features are not described as essential in this specification, they can be deleted as appropriate.

20 optical distance measuring device 30 optical system 31 cover 32 housing 40 light emitting unit 41 laser element 43 circuit board 45 collimating lens 50 scanning unit 51 surface reflecting mirror 53 holder 54 rotating shaft 55 rotary solenoid, 60 light receiving section, 61 light receiving lens, 65 light receiving array, 66 light receiving element, 68 SPAD circuit, 69 partial pixel, 100 SPAD calculation section, 110 control section, 114 memory, 120 addition section, 121 intra-block adder, 130 Histogram generation unit 140 peak detection unit 150 distance calculation unit

Claims (14)

An optical distance measuring device (20) for measuring the distance to an object by irradiating light to the outside,
a light emitting unit (40) that emits pulsed light to a predetermined range;
an optical system (30) for forming an image of reflected light from the predetermined range corresponding to the pulsed light on a light receiving surface (65);
In the light receiving surface, a light receiving unit (69) arranged with a plurality of light receiving circuits (69) capable of individually detecting the reflected light as an electrical signal for each pixel (66), which is a unit for performing detection at a first resolution. 60) and
According to the result of detection of the reflected light by the light receiving circuit, the target reflected light corresponding to the target including the distance from the return time from the emission of the pulsed light to the target existing in the predetermined range a specifying unit (110, 140, 150) for specifying the spatial position of an object;
with
The specifying unit includes a first result obtained by superimposing outputs of the plurality of light receiving circuits arranged in the pixel, and the light receiving circuit when a part of the plurality of light receiving circuits arranged in the pixel is excluded. and a second result obtained by superimposing the outputs of and from the return time of the target reflected light, specifying the position of the object in the space at a second resolution higher than the first resolution. An optical ranging device that performs resolution specific processing. 2. The optical distance measuring device according to claim 1, further comprising a storage unit that stores the second result in association with the position of the removed light receiving circuit,
The specifying unit, as the high-resolution specifying process,
The spatial position of the object is determined at the first resolution from the return time at which the first result obtained by superimposing the detection results of the plurality of light receiving circuits is larger than a predetermined first threshold. identify,
generating a difference between the first result and the second result stored in the storage unit in association with the position of the removed light receiving circuit;
A position in space corresponding to the position of the removed light receiving circuit is specified at the second resolution by the return time when the difference is greater than a predetermined second threshold.
optical rangefinder. The optical distance measuring device according to claim 1,
The specifying unit, as the high-resolution specifying process,
The spatial position of the object corresponding to the pixel is determined from the return time at which the first result obtained by superimposing the detection results of the plurality of light receiving circuits is greater than a predetermined first threshold value. specified at a first resolution;
When some of the plurality of light-receiving circuits are sequentially removed by changing the position of the light-receiving circuits, a result of superimposing the outputs of the remaining light-receiving circuits is associated with the positional difference of the removed light-receiving circuits. stored in a storage unit (114),
generating, as the second result, a result obtained by combining at least two of the superimposed results stored in association with the difference in position of the removed light receiving circuit;
generating a difference between the first result and the second result in association with the combination;
The position in space corresponding to the position of the light receiving circuit removed by the combination is determined to a second resolution higher than the first resolution by the return time whose difference is greater than a predetermined second threshold. Identify with
optical rangefinder. The optical distance measuring device according to any one of claims 1 to 3,
The identification unit
If it is determined from the first result that there are a plurality of return times that are greater than the predetermined first threshold value, the high resolution identification process performs identification at the second resolution,
If it is not determined that there are a plurality of positions, the second resolution is not specified by the high resolution specifying process,
optical rangefinder. The optical distance measuring device according to claim 1,
Repeating the emission of the pulsed light by the light emitting unit and the detection of the reflected light by the plurality of light receiving circuits a plurality of times,
The specifying unit, as the high-resolution specifying process, each time it repeats,
a storage unit (114) in which each of the second results obtained when the positions of some of the plurality of light receiving circuits are changed and sequentially removed is associated with the positions of the removed one of the light receiving circuits; ), and
The spatial position of the object is identified at a first resolution corresponding to the pixel from the return time at which the cumulative result of accumulating the respective stored second results is greater than a predetermined first threshold. death,
A difference between the accumulated result and each of the stored second results is obtained, and a spatial position corresponding to the position of the removed light receiving circuit is determined by the return time when the difference is greater than a predetermined second threshold. identifying a position at a second resolution higher than the first resolution;
optical rangefinder. The optical distance measuring device according to claim 1,
Repeating the emission of the pulsed light by the light emitting unit and the detection of the reflected light by the plurality of light receiving circuits of the light receiving unit a plurality of times,
The specifying unit, as the high-resolution specifying process,
In the first iteration, the first result obtained by superimposing the outputs of the plurality of light receiving circuits is obtained and stored in a storage unit (114);
If the first result is greater than a predetermined first threshold, a position in space corresponding to the position of the pixel is specified by a return time of the target reflected light at a first resolution corresponding to the pixel. ,
The second result when the positions of some of the plurality of light receiving circuits are changed and sequentially removed each time the repetition is performed from the second time onward, and the first stored in the storage unit. Find the difference from the result,
An optical distance measuring device that identifies a position in space corresponding to the position of the removed light receiving circuit from the return time in which the difference is greater than the second threshold, with a second resolution higher than the first resolution. The optical distance measuring device according to claim 1,
Repeating the emission of the pulsed light by the light emitting unit and the detection of the reflected light by the plurality of light receiving circuits of the light receiving unit a plurality of times,
The specifying unit, as the high-resolution specifying process,
in the first iteration, obtaining the first result obtained by superimposing the outputs of the plurality of light receiving circuits and storing it in a storage unit;
The second result when the positions of some of the plurality of light receiving circuits are changed and sequentially removed each time the repetition is performed for the second and subsequent times is included in the first result as a cumulative result. remember,
After the completion of the plurality of iterations, from the return time at which the cumulative result becomes greater than a predetermined first threshold, the spatial position of the object is specified at a first resolution corresponding to the pixel;
Each time the iteration is repeated from the second time onward, a difference between the first result and the second result stored in the storage unit is obtained, and from the return time when the difference is greater than a predetermined second threshold, , an optical distance measuring device that specifies a position in space corresponding to the position of the removed light receiving circuit with a second resolution higher than the first resolution. 2. The specifying unit according to claim 1, wherein the number of times the light receiving circuits are overlapped when some of the plurality of light receiving circuits are excluded when obtaining the second result is equal to or greater than the total number of the light receiving circuits. The optical distance measuring device according to claim 7 . 2. When identifying the spatial position of the object based on the first result and the second result, normalizing the second result with respect to the first result. 9. The optical rangefinder according to any one of claims 8 to 9. 10. The optical ranging device according to any one of claims 1 to 9, wherein each of said plurality of light receiving circuits is excluded one or more times when determining said second result. 11. The optical distance measuring device according to claim 10, wherein the number of times of exclusion of said plurality of light receiving circuits is the same. 12. The method according to any one of claims 1 to 11, wherein when the outputs of the light receiving circuits with some of the plurality of light receiving circuits removed are superimposed, the operation of the removed light receiving circuits is stopped. An optical rangefinder as described. 2. From claim 1, wherein said specifying of said spatial position of said object based on said first result and said second result is performed by comparing said first result and said second result. 13. The optical ranging device according to claim 12. An optical ranging method for measuring the distance to an object by irradiating light to the outside,
A pulsed light is emitted in a predetermined range,
forming an image of reflected light from the predetermined range corresponding to the pulsed light on a light receiving surface;
arranging a plurality of light-receiving circuits capable of individually detecting the reflected light on the light-receiving surface for each pixel, which is a unit for performing detection at a first resolution;
According to the result of detection of the reflected light by the light receiving circuit, the target reflected light corresponding to the target including the distance from the return time from the emission of the pulsed light to the target existing in the predetermined range When specifying a spatial position of an object, a first result obtained by superimposing outputs of the plurality of light receiving circuits arranged in one pixel of the light receiving surface and the plurality of light receiving circuits arranged in the pixel the position of the object in the space from the return time of the object reflected light based on a second result obtained by superimposing the output of the light receiving circuit when part of the light receiving circuit is removed; An optical ranging method that identifies at a second resolution that is higher than the first resolution.

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