Distance measuring device and distance measuring method

Abstract

To provide a distance measuring device and distance measuring method which can reduce the time required to acquire distance information.SOLUTION: A distance measuring device comprises: a light receiving unit that detects an optical signal including light emitted from a light emitting unit and reflected by a target object, and converts it into a pulse signal; an exposure period control unit that sets the light receiving unit to one of multiple exposure periods set correspondingly to multiple classes determined according to the time from light emission to detection for each emission of light from the light emitting unit; an information generation unit that generates information representing the relationship between the class and the frequency indicating the number of times the pulse signals are detected on the basis of the signal output from the light receiving unit during a prescribed frame period that includes multiple emissions from the light emitting unit; and a peak determination unit that determines a peak of the frequency in the information. If the peak of the frequency is detected in the information acquired during a first frame period, the exposure time control unit sets the exposure period sequentially starting from the period closer to the period corresponding to the class where the peak is detected in the next second frame period.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] One known distance measurement method for measuring the distance to an object using light is the time of flight (TOF) method. The TOF method measures the distance to an object based on the time from when light is emitted toward the object to when the light reflected by the object is detected. Patent Document 1 describes a distance measurement device that applies the TOF method to a photon detection sensor using a SPAD (Single Photon Avalanche Diode) element to measure the distance to an object.

[0003] In the distance measurement method described in Patent Document 1, a short-pulse laser beam that is repeatedly emitted at a predetermined frequency is irradiated toward an object, and the irradiation of the laser beam is synchronized with detection by a SPAD sensor to detect reflected light from the object. That is, a specific exposure period (gating period) is set in the SPAD sensor in association with the emission timing of the laser beam, and photon detection is performed during the exposure period. Then, the exposure period is shifted sequentially to obtain signals corresponding to each of the multiple exposure periods. The results are recorded in a histogram memory, and the distance to the object is calculated from the histogram peak. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2017 / 0052065 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the technology described in Patent Document 1, histogram information along the depth direction of the distance measurement range is obtained by performing measurements while sequentially shifting the exposure period, which takes time to generate the histogram information and can result in a decrease in frame rate.

[0006] An object of the present invention is to provide a technology for shortening the time required to acquire distance information in a distance measuring device and distance measuring method that acquires distance information along the depth direction of the distance measurement range by performing measurements while sequentially shifting the exposure period. [Means for solving the problem]

[0007] According to one disclosure of the present specification, there is provided a distance measuring device comprising: a light receiving unit that detects an optical signal including light emitted from an light emitting unit and reflected by an object in a measurement area and converts the light into a pulse signal; an exposure period control unit that sets the light receiving unit to one of a plurality of exposure periods set corresponding to a plurality of classes determined according to the time from when the light is emitted to when it is detected, for each light emitted by the light emitting unit; an information generating unit that generates information indicating the relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including a plurality of lights emitted by the light emitting unit; and a peak determination unit that determines a frequency peak in the information, wherein when a frequency peak is detected in the information acquired in a first frame period, the exposure period control unit sets the exposure period in a second frame period following the first frame period in order from the period closest to the period corresponding to the class in which the peak was detected.

[0008] According to another disclosure in this specification, there is provided a distance measuring device comprising: a light receiving unit that detects an optical signal including light emitted from an light emitting unit and reflected by an object in a measurement area and converts the light into a pulse signal; an exposure period control unit that sets the light receiving unit to one of a plurality of exposure periods set corresponding to a plurality of classes determined according to the time from when the light is emitted to when it is detected, for each emission of light by the light emitting unit; an information generating unit that generates information indicating the relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including multiple emissions of light by the light emitting unit; and a distance information acquisition unit that acquires distance information regarding the object from outside, wherein the exposure period control unit sets the exposure periods in order from the period closest to the period corresponding to the distance information acquired by the distance information acquisition unit.

[0009] Furthermore, according to yet another disclosure of the present specification, there is provided a distance measurement method that detects an optical signal including light emitted from an light-emitting unit and reflected by an object in a measurement area, and calculates a distance to the object based on the detected signal, wherein, for each emission of light by the light-emitting unit, a light-receiving unit is set to one of a plurality of exposure periods set corresponding to a plurality of classes determined according to the time from when the light is emitted to when it is detected, the signal detected by the light-receiving unit is converted into a pulse signal, and information representing the relationship between the class and a frequency indicating the number of times the pulse signal was detected is generated based on the signal output from the light-receiving unit during a predetermined frame period including multiple emissions of light by the light-emitting unit, and when a frequency peak is detected in the information acquired in a first frame period, the exposure period is set in a second frame period following the first frame period in order from the period closest to the period corresponding to the class in which the peak was detected. Effect of the Invention

[0010] According to the present invention, in a distance measuring device and distance measuring method that acquires distance information along the depth direction of the distance measurement range by performing measurements while sequentially shifting the exposure period, the time required to acquire distance information can be shortened. [Brief description of the drawings]

[0011] [Figure 1] 1 is a block diagram showing a schematic configuration of a distance measuring device according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a timing chart showing the basic operation of the distance measuring device according to the first embodiment of the present invention. [Diagram 3] 3A to 3C are diagrams illustrating a method of acquiring distance information in the distance measuring device according to the first embodiment of the present invention. [Figure 4] 3A to 3C are diagrams illustrating a first measurement mode in the distance measuring device according to the first embodiment of the present invention. [Diagram 5] 5A to 5C are diagrams illustrating a second measurement mode in the distance measuring device according to the first embodiment of the present invention. [Figure 6] 4 is a flowchart (part 1) showing the operation of the distance measuring device according to the first embodiment of the present invention. [Figure 7] 4 is a flowchart (part 2) showing the operation of the distance measuring device according to the first embodiment of the present invention. [Figure 8] FIG. 2 is a diagram (part 1) showing a peak detection method in the distance measuring device according to the first embodiment of the present invention. [Figure 9] FIG. 2 is a diagram (part 2) showing a peak detection method in the distance measuring device according to the first embodiment of the present invention. [Figure 10] FIG. 11 is a block diagram showing a schematic configuration of a distance measuring device according to a second embodiment of the present invention. [Figure 11] FIG. 6 is a diagram illustrating a basic operation of a distance measuring device according to a second embodiment of the present invention. [Figure 12] FIG. 11 is a block diagram showing a schematic configuration of a distance measuring device according to a third embodiment of the present invention. [Figure 13] 10 is a flowchart showing the operation of a distance measuring device according to a third embodiment of the present invention. [Figure 14] FIG. 11 is a block diagram showing a schematic configuration of a distance measuring device according to a fourth embodiment of the present invention. [Figure 15] FIG. 13 is a diagram showing a configuration example of a moving body according to a fifth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the present invention, and not all of the combinations of features described in each embodiment are necessarily essential to the solution of the present invention.

[0013] [First embodiment] A distance measuring device and a distance measuring method according to a first embodiment of the present invention will be described with reference to Figs. 1 to 9. Fig. 1 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment. Fig. 2 is a timing chart showing the basic operation of the distance measuring device according to this embodiment. Fig. 3 is a diagram explaining a method of acquiring distance information in the distance measuring device according to this embodiment. Fig. 4 is a diagram explaining a first measurement mode in the distance measuring device according to this embodiment. Fig. 5 is a diagram explaining a second measurement mode in the distance measuring device according to this embodiment. Figs. 6 and 7 are flowcharts showing the operation of the distance measuring device according to this embodiment. Figs. 8 and 9 are diagrams showing a peak detection method in the distance measuring device according to this embodiment.

[0014] First, a schematic configuration of the distance measuring device according to this embodiment will be described with reference to Fig. 1. The distance measuring device 100 according to this embodiment may be configured with a light emitting unit 10, a control unit 20, an exposure period control unit 30, a light receiving unit 40, a histogram information generating unit 70, a peak determination unit 80, and an output unit 90, as shown in Fig. 1, for example. The control unit 20 is connected to the light emitting unit 10 and the exposure period control unit 30. The exposure period control unit 30 is connected to the light receiving unit 40. The light receiving unit 40 is connected to the histogram information generating unit 70. The histogram information generating unit 70 is connected to the peak determination unit 80 and the output unit 90. The peak determination unit 80 is connected to the control unit 20 and the output unit 90.

[0015] The light emitting unit 10 has a light emitting element (not shown) and has a role of emitting pulsed light (irradiation light 12) such as laser light emitted from the light emitting element to the measurement target area. As the light emitting element, for example, an element capable of high-speed modulation such as an LED (Light Emitting Diode) or an LD (Laser Diode) is preferable. The light emitting element may be a VCSEL (Vertical Cavity Surface Emitting Laser) or a surface light emitting element in which the VCSEL is arranged in an array. The light emitting unit 10 is preferably configured to irradiate the measurement target area with a uniform amount of light, and may further include an optical element, such as a lens, for optically converting the light emitted from the light emitting element and irradiating the measurement target area.

[0016] The light receiving unit 40 has a light receiving element (not shown) and serves to detect light incident from the measurement target area. The light incident on the light receiving unit 40 includes ambient light (external light such as sunlight) in the measurement target area, as well as light (reflected light 14) of the irradiated light 12 reflected by the distance measurement target object 110 in the measurement target area. The light receiving element converts the incident light (optical signal) into an electrical signal (pulse signal), counts the generated pulse signal, and holds the counting result. The light receiving unit 40 may be configured to include a plurality of light receiving elements (pixels) arranged in a two-dimensional array. For example, a SPAD (Single Photon Avalanche Diode) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor can be used as the light receiving element. The light receiving unit 40 may further include an optical element, such as a lens, for efficiently guiding the reflected light 14 to the light receiving element 42.

[0017] The exposure period control unit 30 is a control circuit that outputs a control signal that controls the drive timing of the light receiving unit 40. Specifically, the exposure period control unit 30 has a role of generating a control signal that controls the timing of the start and end of the exposure period in the light receiving unit 40 in response to a setting signal from the control unit 20, and outputting the generated control signal to the light receiving unit 40.

[0018] The control unit 20 is a control circuit that controls the overall operation of the distance measuring device 100. Fig. 1 shows only those functions of the control unit 20 that are related to the control of the light emitting unit 10 and the light receiving unit 40. That is, the control unit 20 outputs a control signal to the light emitting unit 10 to control the light emitting timing of the light emitting element. The control unit 20 also outputs a setting signal to the exposure period control unit 30 to set the exposure period in the light receiving unit 40.

[0019] The histogram information generating section 70 has a role of accumulating information output from the light receiving section 40 to generate and hold histogram information. Here, the histogram information is information that indicates the relationship between a plurality of classes (bins) determined according to the time from when the pulsed light is emitted from the light emitting section 10 to when it is detected by the light receiving section 40, and the frequency indicating the number of times the pulsed light is detected in each class.

[0020] The peak determination unit 80 refers to the histogram information held by the histogram information generation unit 70, and calculates the distance to the object 110 to be measured based on the time information corresponding to the class with the highest number of photon detections (frequency). The peak determination unit 80 also determines an initial setting for the exposure period in the next frame, and outputs it to the control unit 20. In this specification, the term "frame" refers to a unit period from the start of distance measurement to the calculation of distance information. In one frame period, one piece of distance information is output for each pixel (light receiving element) constituting the light receiving unit 40. The initial setting of the exposure period will be described later.

[0021] The output unit 90 has a role of outputting information held by the histogram information generating unit 70 and the peak determining unit 80 to the outside of the distance measuring device 100. Specifically, the output unit 90 outputs the histogram information held by the histogram information generating unit 70 and information on the distance to the object 110 to be measured calculated by the peak determining unit 80.

[0022] Fig. 2 is a timing diagram showing the basic operation of the distance measuring device according to this embodiment. During the distance measuring period in the distance measuring device of this embodiment, a frame F of a predetermined length is sequentially performed multiple times. Fig. 2 assumes that N frames F including frame F1, frame F2, ..., frame FN are performed during the distance measuring period.

[0023] Each frame F has a plurality of subframes SF and a peak determination period PP. In FIG. 2, it is assumed that M subframes SF including subframes SF1, SF2, ..., SFM and a peak determination period PP are executed in one frame F. In this specification, the term "subframe" refers to a unit period of measurement performed for a predetermined distance range. The processing in the peak determination period PP will be described later.

[0024] In each subframe SF, a plurality of microframes MF are executed. In Fig. 2, it is assumed that L microframes MF including microframes MF1, MF2, ..., MFL are executed in one subframe SF. In each microframe MF, one emission of pulsed light by the light-emitting unit 10 and an exposure period in which the light-receiving unit 40 detects incident light are executed.

[0025] In each microframe MF, the interval T from the timing when the pulsed light starts to be emitted to the timing when the exposure period starts corresponds to a distance range determined for each subframe SF. For example, the interval T is set to interval T1 in the microframes MF1 to MFL of subframe SF1, and the interval T is set to interval T2 (not shown) different from interval T1 in the microframes MF1 to MFL of subframe SF2. In each microframe MF, a signal (received light data) corresponding to the incident light during the exposure period is output from the light receiving section 40. In this specification, the term "microframe" refers to a unit period during which the light receiving section 40 outputs the received light data.

[0026] The distance range determined for each subframe SF will be described in more detail with reference to Fig. 3. Here, as shown in Fig. 3, a region X is assumed to be located in the measurement target region 120, which is an irradiation region of the light (irradiation light 12) emitted from the light-emitting unit 10, at a distance L from the light-emitting unit 10 and the light-receiving unit 40 and with a thickness LX in the depth direction. In this case, the optical path length of the reflected light 14 (indicated by a solid line in the figure) emitted from the light-emitting unit 10, reflected at the position of the surface of the region X on the side of the light-emitting unit 10 and the light-receiving unit 40, and reaches the light-receiving unit 40 is 2L. On the other hand, the optical path length of the reflected light 14 (indicated by a dashed line in the figure) emitted from the light-emitting unit 10, reflected at the position of the surface of the region X on the opposite side of the light-emitting unit 10 and the light-receiving unit 40, and reaches the light-receiving unit 40 is 2(L+LX). Due to this difference in optical path length, a time difference occurs between the timing at which light reflected at a position on the side of the light-emitting unit 10 and the light-receiving unit 40 in region X reaches the light-receiving unit 40 and the timing at which light reflected at a position on the opposite side of region X from the light-emitting unit 10 and the light-receiving unit 40 reaches the light-receiving unit 40. This time difference can be expressed as 2LX / c, where c is the speed of light.

[0027] By setting the light receiving unit 40 to an exposure period only during the period corresponding to this time difference, information on the object to be measured located in the area X of the measurement target area 120 can be selectively acquired. That is, in the timing diagram of FIG. 2, the interval T from the timing of starting the emission of the pulsed light to the timing of starting the exposure period is set to a time corresponding to a distance of 2L, and the length of the exposure period is set to a time corresponding to a distance of 2LX. By setting the exposure period of the light receiving unit 40 in this manner, information on the object to be measured located in the area X can be acquired. Then, by dividing the measurement target area 120 into a plurality of areas along the depth direction and performing microframe MF with an exposure period set corresponding to each area, information on the object to be measured can be acquired throughout the entire measurement target area 120.

[0028] In each subframe SF, multiple (L) microframes MF are executed with a fixed interval T from the timing when the pulsed light starts to be emitted to the timing when the exposure period starts. For example, in the subframe SF1 in FIG. 2, L microframes MF1 to MFL are executed with the interval T set to interval T1. Then, the number of times that the light receiving unit 40 detects photons during the L microframes MF1 to MFL is counted. By executing multiple subframes SF while changing the interval T, it is possible to obtain information (histogram information) that links the distance range (class) corresponding to each subframe SF with the number of photon detections (frequency) in that class.

[0029] The distance measuring device according to this embodiment has, as its operation modes, a first measurement mode in which measurements are performed over the entire area to be measured while changing the distance range of the measurement object, and a second measurement mode in which measurements are performed with priority given to the vicinity of the distance range corresponding to the distance information obtained immediately before. In either measurement mode, the distance range is changed by the exposure period control unit 30 controlling the period during which the light receiving unit 40 is active (exposure period) in response to a setting signal from the control unit 20.

[0030] First, the first measurement mode will be described with reference to FIG. 4. The upper part of FIG. 4 shows distance ranges set for each of the subframes SF1, ..., SFm, ..., SFM constituting one frame Fn. The 1, ..., m, ..., M attached to each block are the numbers of the subframes SF and also the order in which each subframe SF is performed. The horizontal axis is the interval T, and indicates that the distance range of the subframe SF on the right side of the figure is farther away from the distance measuring device. The middle part of FIG. 4 shows a schematic diagram of the execution of subframes SF1, SF2, ..., SFM in this order. The lower part of FIG. 4 shows an example of a histogram based on information acquired in one frame Fn.

[0031] In the first measurement mode, as described above, measurements are performed over the entire distance measurement range while changing the distance range (exposure period) for each subframe SF. When the measurement target area is divided into M distance ranges, measurements are performed in order from the distance range corresponding to the subframe SF1 with the shortest interval T to the distance range corresponding to the subframe SFM with the longest interval T, as shown in Fig. 4 for example. The order in which subframes SF1 to SFM are performed is not particularly limited.

[0032] When the light receiving unit 40 detects a photon in a microframe MF, it outputs a signal indicating that a photon has been detected to the histogram information generating unit 70 for each pixel. The histogram information generating unit 70 counts the number of detected photons for each pixel in each subframe SF. That is, the information acquired in each subframe SF is the result of accumulating the number of photons detected in multiple microframes MF belonging to that subframe SF, and indicates the total number of photons detected within a predetermined distance range. The value counted in this way is the number of photons detected in each subframe SF.

[0033] By performing measurements from subframe SF1 to subframe SFM, information can be obtained that links the distance range (class) corresponding to each subframe SF with the number of photon detections (frequency) in that distance range. The histogram information generating unit 70 holds the information thus obtained. In this specification, this information is referred to as histogram information, as it is likened to a histogram (see the lower part of FIG. 4) that shows the relationship between the classes and the frequencies.

[0034] In the final peak determination period PP of frame Fn, the peak determination unit 80 extracts the distance range with the highest number of detected photons from the histogram information held by the histogram information generation unit 70. For example, in the example of Fig. 4, since the distance range corresponding to subframe SFm has the highest number of detected photons, the distance to the object 110 to be measured is calculated based on the interval Tm set for that subframe SFm.

[0035] Next, the second measurement mode will be described with reference to FIG. 5. The upper part of FIG. 5 shows an example of a histogram based on information acquired in a frame F(n-1) immediately before a certain frame Fn. The middle part of FIG. 5 shows distance ranges set for each of the subframes SF1, ..., SFm, ..., SFM constituting the frame Fn. The 1, ..., m, ..., M attached to each block are the numbers of the subframes SF, and also the order in which each subframe SF is executed. The horizontal axis is the interval T, and indicates that the distance range of the subframe SF on the right side of the figure is farther away from the distance measuring device. The lower part of FIG. 5 shows that the subframes SF1, SF2, ..., SFM are executed in this order.

[0036] In the second measurement mode, as described above, the measurement is performed with priority given to the vicinity of the distance range corresponding to the distance information acquired immediately before. The distance information acquired immediately before may be distance information calculated based on the histogram information of the immediately previous frame held by the histogram information generating unit 70, or may be distance information acquired immediately before from the outside. When performing different control for each pixel or control for each region, distance information may be acquired based on the peak of histogram information acquired by other pixels. In addition, when acquiring distance information, in addition to the number of photon detections in the peak distance range of the histogram information, the number of photon detections in the distance range around the peak may be further considered. When acquiring distance information from the outside, the distance information can be acquired using, for example, an ultrasonic sensor, a radar, a visible image camera, an infrared sensor, or another LiDAR system. In this case, the distance measuring device may further include a distance information acquiring unit for acquiring distance information from the outside.

[0037] Here, the distance information previously acquired is assumed to be distance information calculated based on histogram information of the immediately preceding frame F(n-1). If the immediately preceding frame F(n-1) is assumed to be frame Fn in the measurement example of FIG. 4, the distance range corresponding to subframe SFm in FIG. 4 becomes the immediately preceding distance information calculated. In this case, in the second measurement mode, the distance range corresponding to subframe SFm in FIG. 4 is set as the reference distance range. Then, the distance range set as the reference distance range is set as the subframe SF to be executed first, and an unmeasured distance range closer to the reference distance range is preferentially set as the subframe SF to be executed next.

[0038] In the example of Fig. 5, the exposure period control unit 30 first sets the distance range corresponding to the subframe SFm in Fig. 4 as the subframe SF1 to be executed first, and executes the subframe SF1. The peak determination unit 80 refers to the information acquired by measuring the subframe SF1, and determines whether the information has a peak equivalent to the peak acquired in the immediately preceding frame F. The method of determining the peak will be described in detail later.

[0039] If there is no peak in subframe SF1, the exposure period control unit 30 sets the distance range with the next highest priority after the reference distance range as the subframe SF2 to be executed next, and executes the subframe SF2. In the example of Fig. 5, a distance range adjacent to the reference distance range and located closer to the distance measuring device 100 than the reference distance range is set as the subframe SF2. The peak determination unit 80 refers to the information acquired by measuring the subframe SF2, and determines whether the information has a peak equivalent to the peak acquired in the immediately preceding frame F.

[0040] If no peak exists in subframe SF2, the exposure period control unit 30 sets the distance range with the next highest priority after the reference distance range as the subframe SF3 to be executed next, and executes the subframe SF3. In the example of FIG. 5, a distance range adjacent to the reference distance range and located on the opposite side of the reference distance range from the distance measuring device 100 is set as the subframe SF3. The peak determination unit 80 refers to the information acquired by measuring the subframe SF3, and determines whether the information has a peak equivalent to the peak acquired in the immediately preceding frame F. Thereafter, the distance ranges with the highest priority are set as the subframes SF in order, starting from the one with the highest priority, until a peak is detected in the acquired information, and the subframe SF is executed.

[0041] If the acquired information has a peak equivalent to the peak acquired in the immediately preceding frame F(n-1), acquisition of subsequent subframes SF is stopped, and the distance range corresponding to the subframe SF in which the peak was detected is set as a new reference distance range.

[0042] Since the time from the previous frame F(n-1) to frame Fn is short, if the object to be measured is the same, it is expected that the distance ranges in which peaks are detected will be close in successive frames F. Therefore, according to the second measurement mode, it is possible to reduce the number of subframes SF performed in one frame F and quickly obtain distance information about the object to be measured.

[0043] Next, the specific operation of the distance measuring device according to this embodiment will be described with reference to Figures 6 and 7. The flowcharts in Figures 6 and 7 show an example of operation in which, when a peak exists in the histogram information acquired in the immediately preceding frame F(n-1), a reference distance range is calculated from the peak, and measurement is preferentially performed from the vicinity of the calculated reference distance range. In this example of operation, when the position of the object to be measured has been identified, acquisition of subsequent subframes SF of frame Fn is suspended, and the operation proceeds to distance measurement of the next frame F(n+1).

[0044] First, in step S101, a variable n indicating the number of frame F is set to 1. Note that, although it is assumed here that a predetermined number (N) of frames are continuously executed as the distance measurement operation, it is also possible to configure the number of frames to be executed not to be predetermined, and to stop the distance measurement operation in response to, for example, an external signal. In this case, step S101 is not necessary.

[0045] Next, in step S102, a variable m indicating the order of subframes SF and a variable k indicating the number of the distance range of the measurement target are set to 1. Here, the maximum number of subframes executed during one frame is M. The distance range number k is, for example, a consecutive number 1, 2, 3, ..., K-2, K-1, K indicating the distance range corresponding to the class of the histogram information from the side closer to the distance measuring device. K indicates the number of the distance range farthest from the distance measuring device among the distance ranges included in the distance measuring range.

[0046] Next, in step S103, it is determined whether or not a reference distance range is set in the peak determination unit 80. If the result of the determination is that a reference distance range is not set in the peak determination unit 80 ("YES" in step S103), the process proceeds to step S106. If the result of the determination is that a reference distance range is set in the peak determination unit 80 ("NO" in step S103), the process proceeds to step S104, and the variable k is set to the number ks of the reference distance range. This causes the measurement mode to transition to the second measurement mode. After step S104, the process proceeds to step S106.

[0047] Next, in step S106, the microframe MF is executed. In step S106, a series of processes from step S201 to step S203 shown in Fig. 7 is regarded as one microframe MF, and is executed repeatedly L times as shown in Fig. 2. The variable A shown in Fig. 7 is a variable indicating the number of times the microframe MF is executed. "A=1,L,1" indicates that A is repeatedly executed from microframe MF1 to microframe MFL while incrementing by 1.

[0048] The measurement mode in the microframe MF is determined depending on whether or not a reference distance range is set in the peak judgment unit 80. That is, when a reference distance range is not set in the peak judgment unit 80, the first measurement mode is executed, and when a reference distance range is set in the peak judgment unit 80, the second measurement mode is executed.

[0049] In step S201, the control unit 20 controls the light-emitting unit 10 and the exposure period control unit 30 to set the interval T from the timing when the light-emitting unit 10 starts emitting pulsed light to the timing when the exposure period starts to an interval Tk, and measurement is performed. For example, the interval Tk is set to an interval T1 corresponding to the distance range closest to the distance measuring device in the case of the microframe MF1 in the first measurement mode, and is set to an interval Tks corresponding to the reference distance range in the case of the microframe MF1 in the second measurement mode. When each pixel constituting the light-receiving unit 40 detects a photon during the exposure period, it generates and internally stores received light data indicating the number of detected photons.

[0050] In the next step S202, the histogram information generating section 70 performs a readout scan on the multiple pixels that make up the light receiving section 40, and sequentially reads out the light reception data held by the pixels in a predetermined region.

[0051] In the next step S203, the histogram information generating section 70 accumulates the number of photons indicated by the read-out light reception data for each pixel.

[0052] In this way, by executing the microframe MF L times and accumulating the number of photons detected for each pixel, the number of photon detections (frequency) in the distance range (class) corresponding to the interval Tk can be obtained as data for the subframe SFm.

[0053] Next, in step S107, it is determined whether or not a reference distance range is set in peak determination unit 80. If the result of the determination is that a reference distance range is not set in peak determination unit 80 ("YES" in step S107), the process proceeds to step S108. If the result of the determination is that a reference distance range is set in peak determination unit 80 ("NO" in step S107), the process proceeds to step S116.

[0054] In step S108, it is determined whether the currently active subframe SFm is the last subframe SFM constituting frame Fn. If the determination result shows that the currently active subframe SFm is the last subframe SFM constituting frame F (m=M, "YES" in step S108), the process proceeds to step S110. If the determination result shows that the currently active subframe SFm is not the last subframe SFM constituting frame Fn (m≠M, "NO" in step S108), the process proceeds to step S109. In step S109, the variable m representing the number of the subframe SF and the variable k representing the distance range number are incremented by 1. After step S109, the process returns to step S106, and the microframe MF of the next subframe SF(m+1) is executed.

[0055] When the reference distance range is not set in the peak determination unit 80, the series of processes from step S106 to step S109 described above are repeatedly executed M times while sequentially changing the distance range of the measurement target. That is, the first measurement mode is executed, and histogram information over the entire distance measurement range is acquired.

[0056] In step S110, the peak determination unit 80 determines whether or not a peak has been detected in the histogram information acquired in the first distance measurement mode. If the result of the determination is that a peak has not been detected ("NO" in step S110), the process proceeds to step S113. If the result of the determination is that a peak has been detected ("YES" in step S110), the process proceeds to step S111. The method of determining a peak will be described in detail later.

[0057] In step S111, the peak determination unit 80 sets the number of the distance range in which the peak was detected as the reference distance range number ks, and calculates distance information to the object to be measured based on the distance range in which the peak was detected.

[0058] In the following step S112, the output unit 108 outputs the distance information calculated by the peak determination unit 107 to the outside.

[0059] In step S113, it is determined whether the currently executing frame Fn is the last frame FN. If the determination result is that the currently executing frame Fn is the last frame FN (n=N, "YES" in step S113), the series of distance measurement processes ends. If the determination result is that the currently executing frame Fn is not the last frame FN (n≠N, "NO" in step S113), the process proceeds to step S121, and the variable n representing the number of frame F is incremented by 1. After step S121, the process returns to step S102, and the next frame F(n+1) is executed.

[0060] In step S116, the peak determination unit 80 determines whether or not a peak has been detected in subframe SFm. If the result of the determination is that a peak has been detected (step S116 "YES"), the control unit 20 stops processing the subframes SF of frame Fn and the process proceeds to step S111. If a peak has not been detected (step S116 "NO"), the process proceeds to step S117. The method of determining a peak will be described in detail later.

[0061] In step S117, it is determined whether the distance range of the measurement target is the distance range (k=1) closest to the distance measuring device or the distance range (k=K) farthest from the distance measuring device among the distance measuring ranges.

[0062] If the result of the determination in step S117 is that the variable k is not 1 or K ("NO" in step S117), the process proceeds to step S118. In step S118, the variable m, which represents the number of the subframe SF, is incremented by 1. In the following step S119, the distance range of the measurement object in the next subframe SF(m+1) is selected from unmeasured distance ranges that are closer to the reference distance range. For example, the number k of the distance range of the measurement object in subframe SFm is calculated as (ks-INT(m / 2)×(-1)) where ks is the reference distance range number and m is the subframe SF number. m ), where INT is a function that rounds down to the nearest integer. By setting the number k of the distance range to be measured in this manner, the distance ranges in subframes SF1, SF2, SF3, SF4, SF5, SF6, ... are assigned in the order of distance ranges ks, ks-1, ks+1, ks-2, ks+2, ks-3, .... This allows unmeasured distance ranges closest to the reference distance range to be assigned to subframes SF with priority. After step S119, the process returns to step S106, and the next subframe SF(m+1) of frame Fn is executed.

[0063] If the result of the determination in step S117 is that the variable k is 1 or K ("YES" in step S117), the process proceeds to step S120, where the registered reference distance range is deleted. In other words, the variable k reaching 1 or K means that no peak was detected in the second measurement mode, and the registered reference distance range is deleted in order to execute the next frame F(n+1) in the first measurement mode. After step S120, the process proceeds to step S121, where the variable n, which represents the number of frame F, is incremented by 1. After step S121, the process returns to step S102, where the next frame F(n+1) is executed.

[0064] Next, the peak detection methods in steps S110 and S116 will be described with reference to Figures 8 and 9. Figures 8(a) and 9(a) show an example of a histogram in frame Fn measured in the first measurement mode. Figure 8(b) shows an example of a histogram in the next frame F(n+1) measured in the second measurement mode with a reference distance range set based on the histogram in Figure 8(a). Figure 9(b) shows an example of a histogram in the next frame F(n+1) measured in the second measurement mode with a reference distance range set based on the histogram in Figure 9(a).

[0065] FIG. 8 shows an example in which only one clear peak is detected in the histogram of frame Fn measured in the first measurement mode. In frame Fn, the first measurement mode is used to measure subframes SF1 to SFM corresponding to the entire distance measurement range while sequentially changing the distance range of the measurement object in a direction away from the distance measurement device (see FIG. 8(a)). In the case of this frame Fn, since a peak in the number of detected photons exists in subframe SFm, the class number m of the distance range corresponding to subframe SFm is set as the reference distance range number ks. When only one clear peak is detected in the histogram obtained by measuring the entire distance measurement range as in this case, the distance range corresponding to subframe SFm in which the peak was detected is set as the reference distance range in the next frame F(n+1).

[0066] In frame F(n+1), the second measurement mode is used to sequentially select unmeasured distance ranges that are closer to the reference distance range set in frame Fn, with the reference distance range at the center, and measurement is continued until a peak is detected. In the example of FIG. 8(b), distance ranges corresponding to classes m, m-1, m+1, m-2, ... are sequentially selected, and subframe SF is executed. Then, when a peak corresponding to the peak detected in frame Fn is detected, execution of subsequent frames is stopped. For example, if a peak corresponding to the peak of frame Fn is detected in class (m-2) of frame F(n+1), subframe SF corresponding to class (m+2) and after is not executed, and the process moves to frame F(n+2).

[0067] The detection of a peak corresponding to the peak of frame Fn can be performed, for example, by comparing the number of photon detections in the class of frame Fn set as the reference distance range with the number of photon detections in the class of the distance range of interest. For example, the number of photon detections in the class of frame Fn set as the reference distance range is multiplied by a predetermined error rate and stored in memory as a value including the error range. Then, the number of photon detections in the class acquired in frame F(n+1) is compared with the value stored in memory. If the number of photon detections in the class acquired in frame F(n+1) is greater than the value stored in memory, the number of photon detections can be determined to be a peak. In addition, a threshold value for determining the magnitude of the peak may be set in advance, and the determination may be performed by comparing the magnitude of the peak acquired in frame F(n+1) with the threshold value. Note that the method of detecting a peak corresponding to the peak of frame Fn is not limited to these methods as long as the method can specify the magnitude of the peak.

[0068] FIG. 9 shows an example in which a plurality of classes showing the same number of photon detections as the class with the maximum number of photon detections are detected in the histogram of the frame Fn measured in the first measurement mode. In this measurement example, as in the example of FIG. 8, in the frame Fn, the first measurement mode is used to measure the subframes SF1 to SFM corresponding to the entire distance measurement range while sequentially changing the distance range of the measurement object in the direction away from the distance measurement device (see FIG. 9(a)). When a plurality of classes showing the same number of photon detections as the class with the maximum number of photon detections are detected, the reference distance range can be set according to the purpose of use of the distance measurement device, etc. For example, when the distance measurement device is applied to an on-vehicle sensor, the class closest to the distance measurement device can be set as the reference distance range from among the plurality of classes showing the same number of photon detections as the class with the maximum number of photon detections, from the viewpoint of improving the detection sensitivity of a closer object to be measured. In the example of FIG. 9(a), the distance range corresponding to class m can be set as the reference distance range.

[0069] In frame F(n+1), the second measurement mode is used to sequentially select unmeasured distance ranges closer to the reference distance range set in frame Fn, and measurement is continued until a peak is detected. In the example of FIG. 9(b), distance ranges corresponding to classes m, m-1, m+1, m-2, ... are sequentially selected, and subframe SF is executed. Then, when a peak corresponding to the peak detected in frame Fn is detected, execution of subsequent frames is stopped. For example, if a peak corresponding to the peak of frame Fn is detected in class (m+1) of frame F(n+1), subframe SF corresponding to class (m-2) and after is not executed, and the process proceeds to frame F(n+2). The method of detecting a peak may be the same as that of FIG. 8.

[0070] In addition, when multiple classes showing the same number of photon detections as the class with the largest number of photon detections are detected, the class selected as the reference distance range does not necessarily have to be the class with the closest distance from the distance measuring device. For example, it may be set to the class with the furthest distance from the distance measuring device among the multiple classes showing the same number of photon detections as the class with the largest number of photon detections, or it may be set to an intermediate class among the multiple classes showing the same number of photon detections as the class with the largest number of photon detections. In addition, the class to be used as the reference distance range may be selected using the integrated value of the number of photon detections of the class of interest and the number of photon detections of the surrounding classes. The class with the largest number of photon detections in the histogram information does not necessarily have to match the class corresponding to the distance information to the object to be measured calculated by the peak determination unit 80 or the reference distance range.

[0071] In this embodiment, when a peak is detected in histogram information in a certain frame by measurement in the first measurement mode, the next frame is measured in the second measurement mode, and the distance range close to the distance range in which the peak was detected is measured preferentially. Then, the measurement of the frame is stopped when a peak corresponding to the peak of the previous frame is detected. Therefore, it is possible to quickly determine the distance to the object to be measured, compared to the case where the presence or absence of a peak is determined after histogram information over the entire distance measurement range is acquired in all frames. In addition, the frame rate can be improved by stopping acquisition of subframes after distance determination and moving to the next frame.

[0072] In the above embodiment, the microframes MF are executed L times in each subframe SF, but when reflected light 14 is detected in a certain microframe MF, it is not necessary to acquire the microframes MF after that subframe SF. With this configuration, it is possible to reduce power consumption while keeping the frame rate constant.

[0073] Thus, according to this embodiment, in a distance measuring device and distance measuring method that acquires distance information along the depth direction of the distance measurement range by performing measurements while sequentially shifting the exposure period, the time required to acquire distance information can be shortened.

[0074] [Second embodiment] A distance measuring device and a distance measuring method according to a second embodiment of the present invention will be described with reference to Figs. 10 and 11. Components similar to those of the distance measuring device according to the first embodiment are given the same reference numerals, and their description will be omitted or simplified. Fig. 10 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment. Fig. 11 is a diagram showing a schematic positional relationship between the distance measuring device and the object to be measured when they are moving.

[0075] In this embodiment, a configuration of a distance measuring device and a distance measuring method suitable for calculating the distance to an object to be measured when the distance measuring device or the object to be measured is moving will be described.

[0076] First, the schematic configuration of the distance measuring device according to this embodiment will be described with reference to FIG. 10. As shown in FIG. 10, the distance measuring device 100 according to this embodiment is similar to the distance measuring device according to the first embodiment, except that it further includes a speed information acquisition unit 50. The speed information acquisition unit 50 is connected to the control unit 20. The speed information acquisition unit 50 is a functional block having a role of measuring the relative moving speed between the distance measuring device and the object to be measured and supplying the measured speed information to the control unit 20. The speed information acquisition unit 50 may itself have a function of measuring the moving speed of the distance measuring device 100, or may be configured to acquire speed information acquired by a speed measurement device other than the distance measuring device 100.

[0077] Fig. 11 is a schematic diagram showing the positional relationship between the distance measuring device 100 and an object 110 to be measured, assuming an in-vehicle sensor as an application example of the distance measuring device 100. Fig. 11 assumes that the distance measuring device 100 and the object 110 to be measured are moving at the same speed (30 m / s) in directions approaching each other.

[0078] 11, X5, X10, and X50 represent distances in units of distance ranges used for the classes of histogram information. For example, in frame Fn, distance measuring device 100 and object 110 are separated by distance X50, which represents that distance measuring device 100 and object 110 are separated by a distance corresponding to the 50th distance range (k=50) from the side of distance measuring device 100. In other words, when histogram information of frame Fn is acquired, a clear peak is detected in subframe SF corresponding to the 50th distance range (k=50).

[0079] When the distance measuring device 100 is driven at a predetermined frame rate, it is assumed that the distance between the distance measuring device 100 and the object 110 to be measured approaches distance X' 40 in the frame F(n+1) following frame Fn. Note that distance X' represents the distance based on the position of the distance measuring device 100 after the transition to frame F(n+1). The number after X' represents the distance in units of the distance range used for the ranks of the histogram information, as in the case of distance X.

[0080] 11, a circle symbol (◯) represents an exposure start position (reference distance range) in the next frame F(n+1) calculated from the histogram information of frame Fn, corrected using speed information acquired by speed information acquisition unit 50. By correcting the reference distance range obtained from the measurement of frame Fn using the speed information of distance measuring device 100 acquired by speed information acquisition unit 50, it becomes possible to start measurement from a position closer to object 110 to be measured. This will be explained below with an example.

[0081] When the speed information is not used, the exposure start position (reference distance range) set for the frame F(n+1) is a position that is a distance X50 away from the position of the distance measuring device 100 in the frame F(n+1), that is, the position of the distance X'50 in FIG. 11. On the other hand, when the speed information of the speed information acquisition unit 50 is used, it is possible to know that the position of the distance measuring device 100 in the frame F(n+1) moves by the distance X5 toward the object of distance measurement 110. This makes it possible to correct the exposure start position (reference distance range) set for the frame F(n+1) to a position that is a distance X'45 away from the position of the distance measuring device 100 in the frame F(n+1). Then, by approaching the exposure start position to the distance range where the peak is expected to be detected, it becomes possible to reduce the number of subframes to be performed in the second measurement mode, and the frame rate can be improved.

[0082] In this embodiment, the exposure start position (reference distance range) is corrected using the speed information of the distance measuring device 100, but the exposure start position (reference distance range) may be corrected using the speed information of the object 110 to be measured. For example, the information of the reference exposure range calculated from the peak of the histogram information can be corrected using the speed information of the object 110 to be measured acquired using another measuring device, and the reference distance range for starting measurement in the next frame can be set.

[0083] In addition, the effect of improving the frame rate can be further enhanced by correcting the exposure start position (reference distance range) of the next frame using the speed information of the distance measuring device 100 and the speed information of the object 110 to be measured. That is, when the exposure start position (reference distance range) is set using the information of the reference distance range and the speed information of the distance measuring device 100, the exposure start position is a position at a distance of X'45 from the distance measuring device 100. In contrast, by further considering the speed information of the object 110 to be measured, it is possible to set the exposure start position at a distance of X'40 from the distance measuring device 100. If the moving direction of the object 110 to be measured is reversed, it is also possible to set the exposure start position at a distance of X'50 from the distance measuring device 100.

[0084] Thus, according to this embodiment, in a distance measuring device and distance measuring method that acquires distance information along the depth direction of the distance measurement range by performing measurements while sequentially shifting the exposure period, the time required to acquire distance information can be shortened.

[0085] [Third embodiment] A distance measuring device and distance measuring method according to a third embodiment of the present invention will be described with reference to Figs. 12 and 13. Components similar to those of the distance measuring device according to the first or second embodiment are given the same reference numerals, and descriptions thereof will be omitted or simplified. Fig. 12 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment. Fig. 13 is a flowchart showing the operation of the distance measuring device according to this embodiment.

[0086] First, the schematic configuration of the distance measuring device according to this embodiment will be described with reference to FIG. 12. The distance measuring device 100 according to this embodiment is similar to the distance measuring device according to the first embodiment, except that it further includes a mode control unit 60 as shown in FIG. 12. The mode control unit 60 is connected to the control unit 20. The mode control unit 60 is a functional block that generates a control signal for switching between the first measurement mode and the second measurement mode and supplies the generated control signal to the control unit 20. For example, the mode control unit 60 can be configured to include a binary counter that counts the number of frames in which measurements have been performed, and to execute the first measurement mode, for example, once every four frames. Alternatively, the mode control unit 60 can be configured to include a binary counter that counts the number of frames performed since the setting of the reference distance range, and to execute the first measurement mode when a predetermined number of frames are consecutively measured in the second measurement mode. In the configuration example shown in FIG. 12, the mode control unit 60 is a part of the components of the distance measuring device 100, but a mode control unit may be prepared as a device separate from the distance measuring device 100, and the mode control unit may be configured to switch the measurement mode.

[0087] Next, a specific operation of the distance measuring device according to this embodiment will be described with reference to Fig. 13. The flowchart in Fig. 13 is similar to the flowchart of the first embodiment shown in Fig. 6, except that it further includes steps S105, S114, and S115. The variable j is a variable for counting the number of consecutive frames F in the second measurement mode. J is a value that is predefined as the upper limit of the number of frames for which consecutive measurement in the second measurement mode is permitted.

[0088] When the measurement is started, the variable j is initialized to 0 in step S101. When the reference distance range is registered in the peak determination unit 80, the process transitions to the second measurement mode, and the value of the variable j is incremented by 1 in step S105 before the start of the subframe SF of the next frame F. When the processing of frame F is completed, it is determined in step S114 whether the value of the variable j has reached J. If the result of the determination is that the variable j has not reached J ("NO" in step S114), the process transitions to step S121. If the result of the determination is that the variable j has reached J ("YES" in step S114), the process transitions to step S115, where the variable j is initialized to 0. After step S115, the process transitions to step S120, where the reference distance range registered in the peak determination unit 80 is deleted. As a result, the measurement mode of the next frame to be executed becomes the first measurement mode.

[0089] By performing the distance measurement operation in this manner, the number of times that frame F performed in the second measurement mode continues is a maximum of J. Therefore, even if an object to be measured appears in a distance range that is included in the distance measurement range of the first measurement mode but not included in the distance measurement range of the second measurement mode being executed, it is possible to detect the object to be measured.

[0090] Thus, according to this embodiment, in a distance measuring device and distance measuring method that acquires distance information along the depth direction of the distance measurement range by performing measurements while sequentially shifting the exposure period, the time required to acquire distance information can be shortened.

[0091] [Fourth embodiment] A distance measuring device and a distance measuring method according to a fourth embodiment of the present invention will be described with reference to Fig. 14. The same components as those in the distance measuring devices according to the first to third embodiments are given the same reference numerals, and their description will be omitted or simplified. Fig. 14 is a block diagram showing a schematic configuration of the distance measuring device according to this embodiment.

[0092] In the distance measuring device 100 according to this embodiment, the pixel region of the light receiving section 40 is divided into a plurality of regions (light receiving sections 40a, 40b) as shown in Fig. 14. An exposure period control section 30, a histogram information generating section 70, and a peak determination section 80 are provided corresponding to each of the plurality of regions of the light receiving section 40. That is, the distance measuring device 100 according to this embodiment has the light receiving section 40a, and the corresponding exposure period control section 30a, histogram information generating section 70a, and peak determination section 80a. The distance measuring device 100 according to this embodiment also has the light receiving section 40a, and the corresponding exposure period control section 30b, histogram information generating section 70b, and peak determination section 80b.

[0093] The control unit 20 transmits a setting signal to each of the exposure period control units 30a, 30b to drive the corresponding light receiving units 40a, 40b. The operation of each of the other components is the same as that of the first embodiment except for the target light receiving unit area (light receiving units 40a, 40b), and therefore the description thereof will be omitted here. The distance measuring device 100 creates histogram information for each of the light receiving units 40a, 40b, and calculates the distance to the object 110 to be measured and the reference distance range.

[0094] By controlling the exposure period for each of the divided light receiving sections 40a, 40b independently, it is possible to detect the object 110 to be measured for each of the light receiving sections 40a, 40b. Even if there are multiple objects 110a, 110b to be measured in the measurement target area as shown in Fig. 14, it is possible to change the exposure conditions for each of the light receiving sections 40a, 40b. Therefore, it is possible to calculate the distance to the objects 110a, 110b to be measured more accurately than when the same exposure conditions are used for the entire pixel area of ​​the light receiving section 40 to measure the distance.

[0095] In this embodiment, an example has been shown in which the number of exposure period control units 30, histogram information generating units 70, and peak determining units 80 is the same as the number of divisions of the light receiving unit 40, but these do not necessarily have to be the same. In other words, as long as the configuration is such that each of the multiple regions of the divided light receiving unit 40 can be controlled independently, the number of exposure period control units 30, histogram information generating units 70, and peak determining units 80 do not necessarily have to be the same as the number of divided regions of the light receiving unit 40. In addition, the number of divisions of the light receiving unit 40 does not necessarily have to be two, and may be three or more.

[0096] Thus, according to this embodiment, in a distance measuring device and distance measuring method that acquires distance information along the depth direction of the distance measurement range by performing measurements while sequentially shifting the exposure period, the time required to acquire distance information can be shortened.

[0097] [Fifth embodiment] A moving body according to the fifth embodiment of the present invention will be described with reference to Fig. 15. Fig. 15 is a diagram showing an example of the configuration of a moving body according to this embodiment.

[0098] Fig. 15(a) shows a configuration example of a device mounted on a vehicle as an on-board camera. The device 300 has a distance measurement unit 303 that measures the distance to an object to be measured, and a collision determination unit 304 that determines whether or not there is a possibility of collision based on the distance measured by the distance measurement unit 303. The distance measurement unit 303 is configured by the distance measurement device 100 described in any one of the first to fourth embodiments. Here, the distance measurement unit 303 is an example of a distance information acquisition means that acquires distance information to the object to be measured. In other words, the distance information is information related to the distance to the object to be measured, etc.

[0099] The device 300 is connected to a vehicle information acquisition device 310 and can acquire vehicle information such as vehicle speed, yaw rate, and steering angle. In addition, the device 300 is connected to a control ECU 320, which is a control device that outputs a control signal to generate a braking force for the vehicle based on the judgment result of the collision judgment unit 304. In addition, the device 300 is also connected to an alarm device 330 that issues an alarm to the driver based on the judgment result of the collision judgment unit 304. For example, when the judgment result of the collision judgment unit 304 indicates that there is a high possibility of a collision, the control ECU 320 performs vehicle control to avoid a collision and reduce damage by applying the brakes, releasing the accelerator, suppressing engine output, etc. The alarm device 330 warns the user by sounding an alarm such as a sound, displaying alarm information on the screen of a car navigation system, etc., and applying vibrations to a seat belt or steering wheel. These devices of the device 300 function as a mobile object control unit that controls the operation of controlling the vehicle as described above.

[0100] In this embodiment, the device 300 measures distances around the vehicle, for example, in front or behind. Fig. 15(b) shows the device when measuring distances in front of the vehicle (distance measurement range 350). A vehicle information acquisition device 310, which serves as a distance measurement control means, sends an instruction to the device 300 or the distance measurement unit 303 to perform a distance measurement operation. This configuration can further improve the accuracy of distance measurement.

[0101] Although the above describes an example of control to prevent collision with other vehicles, the present invention can also be applied to control of automatic driving by following other vehicles, control of automatic driving to prevent deviation from lanes, etc. Furthermore, the device is not limited to vehicles such as automobiles, but can be applied to moving bodies (moving devices) such as ships, aircraft, artificial satellites, industrial robots, and consumer robots. In addition, the present invention can be applied to devices that use object recognition or biometric recognition, such as intelligent transport systems (ITS) and surveillance systems, in addition to moving bodies.

[0102] [Modified embodiment] The present invention is not limited to the above-described embodiment, and various modifications are possible.

[0103] For example, an example in which part of the configuration of any one of the embodiments is added to another embodiment, or an example in which part of the configuration of another embodiment is substituted therefor, is also an embodiment of the present invention.

[0104] In addition, in the above embodiment, the light-emitting unit 10 and the light-receiving unit 40 are described as parts of the components of the distance measuring device 100, but at least one of the light-emitting unit 10 and the light-receiving unit 40 does not necessarily have to be part of the configuration of the distance measuring device 100.

[0105] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0106] It should be noted that the above-mentioned embodiments are merely examples of the implementation of the present invention, and the technical scope of the present invention should not be interpreted as being limited by these embodiments. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

[0107] The disclosure of the above embodiment includes the following configurations and methods. (Configuration 1) a light receiving unit that detects an optical signal including light emitted from the light emitting unit and reflected by an object in a measurement target area and converts the optical signal into a pulse signal; an exposure period control unit that sets the light receiving unit to one of a plurality of exposure periods that are set corresponding to a plurality of classes determined according to a time from when the light is emitted to when the light is detected, for each light emission by the light emitting unit; an information generating unit that generates information representing a relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including a plurality of light emission from the light emitting unit; a peak determination unit that determines a frequency peak in the information, When a frequency peak is detected in the information acquired in a first frame period, the exposure period control unit sets the exposure period in a second frame period following the first frame period in order from a period closest to a period corresponding to the class in which the peak was detected. A distance measuring device comprising: (Configuration 2) In the second frame period, the measurement is stopped at the class in which the peak corresponding to the peak is detected, and the measurement is not performed in the subsequent classes, and the process proceeds to the next frame period. 2. The distance measuring device according to configuration 1, (Configuration 3) When no frequency peak is detected in the information acquired in the first frame period, the exposure period control unit sets the exposure period in the second frame period to a plurality of periods corresponding to the plurality of classes in sequence. 3. The distance measuring device according to configuration 1 or 2. (Configuration 4) The peak determination unit calculates distance information to the object based on time information corresponding to the class in which the peak is detected. 4. A distance measuring device according to any one of configurations 1 to 3. (Configuration 5) A speed information acquisition unit that acquires speed information indicating a moving speed relative to the object, The exposure period control unit calculates a period corresponding to the class in which the peak is detected, taking into account the speed information. 5. A distance measuring device according to any one of configurations 1 to 4. (Configuration 6) When a frame period in which a frequency peak is detected in the information acquired in the previous frame period continues for a predetermined number of frames, the exposure period control unit sets a plurality of periods corresponding to the plurality of classes in the next frame period in order. 6. A distance measuring device according to any one of configurations 1 to 5. (Configuration 7) the light receiving section has a plurality of regions each including a plurality of pixels; the exposure period control unit sets the exposure period independently for each of the plurality of regions; The information generating unit generates a plurality of pieces of information corresponding to the plurality of regions. 7. A distance measuring device according to any one of configurations 1 to 6. (Configuration 8) the frame period includes a plurality of subframes, Each of the plurality of subframes includes a plurality of light emissions from the light emitting unit, and the same exposure period is set for the plurality of light emissions. 8. A distance measuring device according to any one of configurations 1 to 7. (Configuration 9) a light receiving unit that detects an optical signal including light emitted from the light emitting unit and reflected by an object in a measurement target area and converts the optical signal into a pulse signal; an exposure period control unit that sets the light receiving unit to one of a plurality of exposure periods that are set corresponding to a plurality of classes determined according to a time from when the light is emitted to when the light is detected, for each light emission by the light emitting unit; an information generating unit that generates information representing a relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including a plurality of light emission from the light emitting unit; a distance information acquisition unit that acquires distance information relating to the object from an external source, The exposure period control unit sets the exposure periods in order from a period closest to a period corresponding to the distance information acquired by the distance information acquisition unit. A distance measuring device comprising: (Configuration 10) A mobile object, A distance information acquisition device according to any one of configurations 1 to 9, a control means for controlling the moving object based on the distance information acquired by the distance information acquisition device; A moving object comprising: (Method 1) A distance measuring method for detecting an optical signal including light emitted from a light emitting unit and reflected by an object in a measurement target area, and calculating a distance to the object based on the detected signal, comprising: setting a light receiving unit to one of a plurality of exposure periods set corresponding to a plurality of classes determined according to a time from when the light is emitted to when the light is detected, for each light emitted by the light emitting unit, and converting a signal detected by the light receiving unit into a pulse signal; generating information indicating a relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including a plurality of light emission from the light emitting unit; When a frequency peak is detected in the information acquired in a first frame period, in a second frame period following the first frame period, the exposure period is set in order from the period closest to the period corresponding to the class in which the peak was detected. A distance measuring method comprising: [Explanation of symbols]

[0108] 10…Light emitting part 20...Control section 30...Exposure period control unit 40,40a,40b...light receiving section 50…Speed ​​information acquisition unit 60...Mode control section 70, 70a, 70b...Histogram information generating unit 80, 80a, 80b...Peak determination section 90...Output section 100…Distance measuring device

Claims

1. a light receiving unit that detects an optical signal including light emitted from the light emitting unit and reflected by an object in a measurement target area and converts the optical signal into a pulse signal; an exposure period control unit that sets the light receiving unit to one of a plurality of exposure periods that are set corresponding to a plurality of classes determined according to a time from when the light is emitted to when the light is detected, for each light emission by the light emitting unit; an information generating unit that generates information representing a relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including a plurality of light emission from the light emitting unit; a peak determination unit that determines a frequency peak in the information, When a frequency peak is detected in the information acquired in a first frame period, the exposure period control unit sets the exposure period in a second frame period following the first frame period in order from a period closest to a period corresponding to the class in which the peak was detected. A distance measuring device comprising:

2. In the second frame period, the measurement is stopped at the class in which the peak corresponding to the peak is detected, and the measurement is not performed in the subsequent classes, and the process proceeds to the next frame period.

2. The distance measuring device according to claim 1.

3. When no frequency peak is detected in the information acquired in the first frame period, the exposure period control unit sets the exposure period to a plurality of periods corresponding to the plurality of classes in sequence in the second frame period.

3. A distance measuring device according to claim 1 or 2.

4. The peak determination unit calculates distance information to the object based on time information corresponding to the class in which the peak is detected.

3. A distance measuring device according to claim 1 or 2.

5. A speed information acquisition unit that acquires speed information indicating a moving speed relative to the object, The exposure period control unit calculates a period corresponding to the class in which the peak is detected, taking into account the speed information.

3. A distance measuring device according to claim 1 or 2.

6. When a frame period in which a frequency peak is detected in the information acquired in the previous frame period continues for a predetermined number of frames, the exposure period control unit sets a plurality of periods corresponding to the plurality of classes in the next frame period in order.

3. A distance measuring device according to claim 1 or 2.

7. the light receiving section has a plurality of regions each including a plurality of pixels; the exposure period control unit sets the exposure period independently for each of the plurality of regions; The information generating unit generates a plurality of pieces of information corresponding to the plurality of regions.

3. A distance measuring device according to claim 1 or 2.

8. the frame period includes a plurality of subframes; Each of the plurality of subframes includes a plurality of light emissions from the light emitting unit, and the same exposure period is set for the plurality of light emissions.

3. A distance measuring device according to claim 1 or 2.

9. a light receiving unit that detects an optical signal including light emitted from the light emitting unit and reflected by an object in a measurement target area and converts the optical signal into a pulse signal; an exposure period control unit that sets the light receiving unit to one of a plurality of exposure periods that are set corresponding to a plurality of classes determined according to a time from when the light is emitted to when the light is detected, for each light emission by the light emitting unit; an information generating unit that generates information representing a relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including a plurality of light emission from the light emitting unit; a distance information acquisition unit that acquires distance information relating to the object from an external source, The exposure period control unit sets the exposure periods in order from a period closest to a period corresponding to the distance information acquired by the distance information acquisition unit. A distance measuring device comprising:

10. A mobile object, A distance information acquisition device according to claim 1 or 9, a control means for controlling the moving object based on the distance information acquired by the distance information acquisition device; A moving object comprising:

11. A distance measuring method for detecting an optical signal including light emitted from a light emitting unit and reflected by an object in a measurement target area, and calculating a distance to the object based on the detected signal, comprising: setting a light receiving unit to one of a plurality of exposure periods set corresponding to a plurality of classes determined according to a time from when the light is emitted to when the light is detected, for each light emitted by the light emitting unit, and converting a signal detected by the light receiving unit into a pulse signal; generating information indicating a relationship between the class and a frequency indicating the number of times the pulse signal is detected, based on a signal output from the light receiving unit during a predetermined frame period including a plurality of light emission from the light emitting unit; When a frequency peak is detected in the information acquired in a first frame period, in a second frame period following the first frame period, the exposure period is set in order from the period closest to the period corresponding to the class in which the peak was detected. A distance measuring method comprising:

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