Distance measuring device, light receiving device, and distance measuring method

Abstract

The objective of the present invention is to improve security in a distance measuring device that employs a ToF method.　A light emitting unit emits a predetermined number of emitted light beams. A light receiving unit receives reflected light beams of the emitted light beams. A histogram generating unit accumulates the number of times light is received by the light receiving unit for each time point within an accumulation period to generate a histogram. If the histogram includes a plurality of peaks satisfying a predetermined condition, a detecting unit preferentially detects a peak close to the start time of the accumulation period, among the plurality of peaks. A distance calculating unit calculates distance information on the basis of the time point corresponding to the detected peak.

Description

Distance measuring device, light receiving device, and distance measuring method

[0001] The present technology relates to a distance measuring device, and more particularly to a distance measuring device, a light receiving device, and a distance measuring method that measure distance based on the time of flight of light.

[0002] Conventionally, distance measuring devices such as LIDAR (Light Detection and Ranging Laser Imaging Detection and Ranging) have used a time-of-flight (ToF) method for distance measurement. For example, a distance measuring device has been proposed that performs distance measurement using the ToF method by delaying the emission timing of pulsed light by a random time offset for each cycle of a reference clock (see, for example, Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2019-056567

[0004] In the above-mentioned conventional technology, the offset is set to a random time length to improve the accuracy of determining whether the detected light is interfering light. However, the above-mentioned distance measuring device is at risk of being subjected to a distance spoofing attack, in which attack light synchronized with the irradiated light is incident on the distance measuring device, causing the distance measuring device to measure a value different from the actual distance. This risk reduces the security of the above-mentioned distance measuring device.

[0005] This technology was developed in light of these circumstances, and aims to improve security in distance measuring devices that use the ToF method.

[0006] The present technology has been made to solve the above-mentioned problems, and a first aspect thereof is a distance measuring device and a distance measuring method for the distance measuring device, the distance measuring device including: a light emitting unit that irradiates a predetermined number of beams of irradiation light; a light receiving unit that receives light reflected from the irradiation light; a histogram generating unit that generates a histogram by integrating the number of times the light receiving unit receives the beam for each time within an accumulation period; a detection unit that, if the histogram includes multiple peaks that satisfy a predetermined condition, preferentially detects a peak that is closest to the start time of the accumulation period from among the multiple peaks; and a distance calculation unit that calculates distance information based on the time corresponding to the detected peak. This brings about the effect of preventing distance spoofing attacks.

[0007] In addition, in this first aspect, the predetermined number of irradiation lights may include first and second irradiation lights, the light-emitting unit may emit light at first and second light-emitting timings within each of a single or multiple light-emitting periods to irradiate the first and second irradiation lights, the first light-emitting timing may be delayed by an offset time with respect to a start timing of each of the single or multiple light-emitting periods, and an interval between the first and second light-emitting timings within each of the single or multiple light-emitting periods may be an interval randomly selected from a predetermined group of options. This brings about an effect of preventing close-range spoofing attacks.

[0008] In this first aspect, the offset time may be selected randomly from a predetermined group of options, thereby preventing close-range spoofing attacks.

[0009] In the first aspect, the order of the offset times of the single or multiple light emission periods may be selected randomly, thereby preventing close-range spoofing attacks.

[0010] In addition, in this first aspect, the offset time of each of the single or multiple light emission periods may be selected based on a predetermined fixed pattern, thereby providing an effect of preventing close-range spoofing attacks.

[0011] In addition, in this first aspect, the predetermined number of irradiation lights include first, second, and third irradiation lights, the light-emitting unit emits light at first, second, and third light-emitting timings within each of a single or multiple light-emitting periods to irradiate the first, second, and third irradiation lights, a first interval between the first and second light-emitting timings and a second interval between the second and third light-emitting timings may be different values, and an order of the first interval and the second interval within each of the single or multiple light-emitting periods may be selected randomly, thereby preventing close-range spoofing attacks.

[0012] In this first aspect, the first interval and the second interval may be selected from a group of options including K options obtained by multiplying a predetermined real number by each of K natural numbers obtained by omitting some of the consecutive natural numbers from 1 to L, where K is a natural number smaller than L. This brings about the effect of increasing the frequency of a specific peak.

[0013] In this first aspect, the group of options may include a plurality of options arranged in ascending order, and a value of a focused option among the plurality of options may be smaller than that of the focused option and different from the sum of two or more consecutive options, thereby bringing about an effect of increasing the frequency of a specific peak.

[0014] In addition, in this first aspect, the predetermined number of irradiation lights include first, second, and third irradiation lights, the light-emitting unit emits light at first, second, and third light-emitting timings within each of a single or multiple light-emitting periods to irradiate the first, second, and third irradiation lights, and one of a first interval between the first and second light-emitting timings and a second interval between the second and third light-emitting timings may be a predetermined fixed value, and the other may be a variable value longer than the fixed value. This brings about an effect of preventing close-range spoofing attacks.

[0015] In addition, in this first aspect, the predetermined number of irradiation lights may include first, second, third, and fourth irradiation lights, a histogram generation period in which the histogram is generated includes first and second light-emitting periods, the light-emitting unit emits light at first and second light-emitting timings within the first light-emitting period to irradiate the first and second irradiation lights, and emits light at third and fourth light-emitting timings within the second light-emitting period to irradiate the third and fourth irradiation lights, a first interval between the first and second light-emitting timings has a value different from a second interval between the third and fourth light-emitting timings, the first light-emitting timing is delayed by a first offset time with respect to a start timing of the first light-emitting period, the third light-emitting timing is delayed by a second offset time with respect to a start timing of the second light-emitting period, and the order of the first intervals and the second intervals may be selected randomly, thereby providing an effect of preventing close-range spoofing attacks.

[0016] In addition, in this first aspect, the first and second offset times may be randomly selected from a predetermined group of options, and the first and second offset times may be updated when the histogram generation period has elapsed, thereby providing an effect of preventing close-range spoofing attacks.

[0017] In addition, in this first aspect, the order of the first and second offset times within the histogram generation period may be selected randomly, and the order may be updated when the histogram generation period has elapsed, thereby providing an effect of preventing close-range spoofing attacks.

[0018] In this first aspect, the first and second offset times may be selected based on a predetermined fixed pattern, and the fixed pattern may be updated when the histogram generation period has elapsed, thereby preventing close-range spoofing attacks.

[0019] In addition, in this first aspect, the predetermined number of irradiation lights may include first and second irradiation lights, a histogram generation period during which the histogram is generated may include one or more light-emitting periods, the light-emitting unit may emit light at first and second light-emitting timings within each of the single or multiple light-emitting periods to irradiate the first and second irradiation lights, and the histogram generation unit may generate the histogram such that a first peak corresponding to the first irradiation light and a second peak corresponding to the second irradiation light coincide with each other, thereby resulting in an effect of increasing the frequency of a specific peak.

[0020] In addition, in this first aspect, the accumulation period may include a first accumulation period whose start timing is the first light emission timing and a second accumulation period whose start timing is the second light emission timing, and the histogram generation unit may generate a first histogram by integrating the number of times of light reception for each time within the first accumulation period, and may generate a second histogram by integrating the number of times of light reception for each time within the second accumulation period, and may re-accumulate the second histogram in the first histogram. This brings about an effect of increasing the frequency of a specific peak.

[0021] In this first aspect, the histogram generation unit may shift the histogram in accordance with the interval between the first and second light emission timings and re-accumulate the histogram before the shift, thereby increasing the frequency of a specific peak.

[0022] In this first aspect, the histogram generation unit may select one of the elements in the histogram and re-store, in the selected element, an element that precedes or follows the selected element by an interval of the first and second light emission timings, thereby increasing the frequency of a specific peak.

[0023] In this first aspect, the histogram generation unit may switch between a first histogram generation method and a second histogram generation method, the second histogram generation method being a histogram generation method that shifts the histogram and re-accumulates the data in the histogram before the shift, or a histogram generation method that selects one of elements in the histogram and re-accumulates an element before or after the selected element in the selected element, and the first histogram generation method being a histogram generation method that does not require the re-accumulation process, thereby providing an effect that a histogram is generated using an appropriate method.

[0024] A second aspect of the present technology is a light receiving device including a histogram generation unit that generates a histogram by integrating the number of times a light is received by a light receiving unit that receives reflected light from irradiated light for each time period within an accumulation period, and a detection unit that, when the histogram includes multiple peaks that satisfy a predetermined condition, detects a peak that is closest to the start time of the accumulation period from among the multiple peaks. This provides the effect of preventing distance spoofing attacks.

[0025] 1 is a block diagram showing an example configuration of a distance measuring device according to a first embodiment of the present technology. FIG. 2 is a block diagram showing an example configuration of a time management unit according to the first embodiment of the present technology. FIG. 3 is a block diagram showing an example configuration of a counter unit according to the first embodiment of the present technology. FIG. 4 is a block diagram showing an example configuration of a light emitting unit according to the first embodiment of the present technology. FIG. 5 is a block diagram showing an example configuration of a distance calculation unit according to the first embodiment of the present technology. FIG. 6 is a diagram showing an example relationship between a frame period, a histogram generation period, and a light emission period according to the first embodiment of the present technology. FIG. 7 is a timing chart showing an example of operation of a light emitting unit and a ToF sensor according to the first embodiment of the present technology. FIG. 8 is a diagram for describing a long-range spoofing attack. FIG. 9 is a diagram showing an example of light emission timing and a histogram according to the first embodiment of the present technology. FIG. 10 is a flowchart showing an example operation of a distance measuring device according to the first embodiment of the present technology. FIG. 11 is a block diagram showing an example configuration of a ToF sensor according to a modified example of the first embodiment of the present technology. FIG. 12 is a diagram for describing a short-range spoofing attack. FIG. 13 is a diagram showing an example of light emission timing and a histogram according to a second embodiment of the present technology. FIG. 14 is a diagram showing an example of a delay amount according to the second embodiment of the present technology. FIG. 15 is a diagram showing an example of an accumulation period according to a third embodiment of the present technology. FIG. 16 is a block diagram showing an example configuration of a histogram generation unit according to the third embodiment of the present technology. FIG. 10 is a diagram showing an example of a histogram before re-accumulation in the third embodiment of the present technology. FIG. 11 is a diagram showing an example of a histogram re-accumulated within a light emitting period in the third embodiment of the present technology. FIG. 12 is a diagram showing an example of a histogram re-accumulated within another light emitting period in the third embodiment of the present technology. FIG. 13 is a flowchart showing an example of an operation of the distance measuring device in the third embodiment of the present technology. FIG. 14 is a flowchart showing an example of a histogram generation process in the third embodiment of the present technology. FIG. 15 is a diagram showing an example of a histogram when re-accumulation is performed continuously in two light emitting periods in the third embodiment of the present technology. FIG. 16 is a block diagram showing an example of a configuration of a histogram generation unit in a first modified example of the third embodiment of the present technology. FIG. 17 is a flowchart showing an example of a histogram generation process in the first modified example of the third embodiment of the present technology.10 is a diagram showing an example of a histogram in a first modified example of the third embodiment of the present technology. FIG. 11 is a block diagram showing an example of a configuration of a histogram generation unit in a second modified example of the third embodiment of the present technology. FIG. 12 is a flowchart showing an example of a histogram generation process in a second modified example of the third embodiment of the present technology. FIG. 13 is a diagram showing an example of a histogram in a second modified example of the third embodiment of the present technology. FIG. 14 is a diagram showing an example of a light emission timing signal within a light emission period in a third modified example of the third embodiment of the present technology. FIG. 15 is a diagram showing an example of light emission timing and a histogram in a third modified example of the third embodiment of the present technology. FIG. 16 is a diagram showing an example of light emission timing and a histogram in a first comparative example. FIG. 17 is a diagram showing an example of light emission timing and a histogram in a second comparative example. FIG. 18 is a diagram showing an example of a delay amount within a histogram generation period in a fourth embodiment of the present technology. FIG. 19 is a diagram showing another example of a delay amount within a histogram generation period in a fourth embodiment of the present technology. FIG. 19 is a diagram showing an example of a delay amount for the first four lights within a histogram generation period in a fourth embodiment of the present technology. FIG. 19 is a diagram showing an example of a delay amount for the fifth light emission or later within a histogram generation period in a fourth embodiment of the present technology. Fig. 10 is a flowchart showing an example of an operation of a distance measuring device according to a fourth embodiment of the present technology. Fig. 11 is a block diagram showing an example of a configuration of a light emitting unit according to a fifth embodiment of the present technology. Fig. 12 is a block diagram showing an example of a configuration of a ToF sensor according to the fifth embodiment of the present technology. Fig. 13 is a block diagram showing an example of a schematic configuration of a vehicle control system. Fig. 14 is an explanatory diagram showing an example of installation positions of an outside-vehicle information detection unit and an imaging unit.

[0026] Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order: 1. First embodiment (an example in which a preceding peak is given priority in detection) 2. Second embodiment (an example in which burst light is emitted and a preceding peak is given priority in detection) 3. Third embodiment (an example in which a histogram is re-stored and a preceding peak is given priority in detection) 4. Fourth embodiment (an example in which a delay amount is appropriately set and a burst light is emitted, and a preceding peak is given priority in detection) 5. Fifth embodiment (an example in which a preceding peak is given priority in detection and distance measurement is performed within a ToF sensor) 6. Application example to a moving body

[0027] 1 is a block diagram showing an example of the configuration of a distance measuring device 100 according to a first embodiment of the present technology. The distance measuring device 100 is a device that measures the distance to a subject using a ToF method, and includes a light emitting unit 110, a light receiving unit 210, a time management unit 220, and a distance calculation unit 300. As the ToF method, for example, a dToF (direct time of flight) method is used. Note that the distance measuring device 100 can also measure the distance using an iToF (indirect time of flight) method instead of the dToF method.

[0028] The light-emitting unit 110 emits light intermittently to emit intermittent light as illumination light. The illumination light is reflected by the subject, and the reflected light is received by the light-receiving unit 210. The thick dotted lines in the figure indicate the light trails of the illumination light and the reflected light. The light-emitting unit 110 also generates a light-emission timing signal based on a light-emission instruction from the time management unit 220, and emits light in accordance with this light-emission timing signal.

[0029] The light receiving unit 210 and the time management unit 220 are arranged, for example, in the ToF sensor 200. The ToF sensor 200 is an example of a light receiving device in the claims.

[0030] The light receiving unit 210 receives reflected light of the irradiated light, generates a pulse signal, and supplies the pulse signal to the time management unit 220. For example, a plurality of pixels (not shown) are arranged in the light receiving unit 210, and each pixel receives reflected light and generates a pulse signal. Each pixel includes a light receiving element such as a single or multiple SPADs (Single-Photon Avalanche Diodes) and a circuit that generates a pulse signal.

[0031] The time management unit 220 receives the pulse signal from the light receiving unit 210 and generates data for calculating the distance. The time management unit 220 supplies the generated data to the distance calculation unit 300. Details of the data generated by the time management unit 220 will be described later.

[0032] The distance calculation unit 300 calculates the distance for each pixel using the data from the time management unit 220. The distance calculation unit 300 outputs distance data indicating the calculated distance to the outside.

[0033] Although the light-emitting unit 110, the light-receiving unit 210, the time management unit 220, and the distance calculation unit 300 are arranged in one device, they may also be arranged in separate devices. For example, the light-emitting unit 110, the light-receiving unit 210, and the time management unit 220 may be arranged in the distance measuring device 100, and the distance calculation unit 300 may be arranged in an external device.

[0034] 2 is a block diagram showing an example of the configuration of the time management unit 220 according to the first embodiment of the present technology. The time management unit 220 includes a light emission instruction unit 221, a counter unit 230, a delay amount instruction unit 222, and a communication unit 223.

[0035] The counter unit 230 counts a counter value for each pixel over a light-emitting period during which the light-emitting unit 110 is to emit light at least once. The counter unit 230 supplies a start signal indicating the start timing of the light-emitting period to the light-emitting instruction unit 221 and the delay amount instruction unit 222. The counter unit 230 also holds the counter value at the timing of the pulse signal (i.e., the light-receiving timing) for each pixel and supplies it to the communication unit 223.

[0036] The light emission instruction unit 221 instructs the timing of emitting the irradiated light. The light emission instruction unit 221 receives a delay amount from the delay amount instruction unit 222. The delay amount indicates the delay time of the irradiated light emission timing relative to the start timing of the light emission period. The light emission instruction unit 221 generates a light emission instruction when the delay amount has elapsed from the timing of the start signal (i.e., the start timing of the light emission period), and outputs the light emission instruction to the light emission unit 110.

[0037] The delay amount instructing section 222 sets the delay amount and instructs the delay amount. The delay amount instructing section 222 supplies the set delay amount to the light emission instructing section 221 and the communication section 223.

[0038] The communication unit 223 transmits the counter value for each pixel and the delay amount to the distance calculation unit 300. When the data transmitted by the communication unit 223 is received by an external device, the transmitted data may be protected using a protection function of the communication unit 223. Specifically, the communication unit 223 can transmit data for protecting the integrity of the transmitted data together.

[0039] 3 is a block diagram showing an example configuration of the counter unit 230 according to the first embodiment of the present technology. The counter unit 230 includes a counting control unit 231, a plurality of counters 232, and a plurality of memories 233. The counter 232 and the memory 233 are provided for each pixel, for example. For example, when driving pixels in units of rows or areas, the counters 232 and the memories 233 are provided in the same number as the number of pixels in the rows or areas.

[0040] The counting control unit 231 controls the counting operation of the counter 232 and the memory 233. The counting control unit 231 generates a start signal at the start timing of the light emission period and supplies it to the light emission instruction unit 221 and the delay amount instruction unit 222. At the start timing, the counting control unit 231 also initializes the counter values ​​of the counters 232 with a reset command RST_CNT and initializes the memories 233 with a clear command CLR. When the counting control unit 231 receives a pulse signal from the light receiving unit 210, it causes the memory 233 to hold the counter values ​​at that time with a write signal WT.

[0041] The counter 232 counts a counter value over the light emission period in synchronization with the clock signal CLK, and supplies the counter value to the memory 233. The cycle of the clock signal CLK is shorter than the light emission period.

[0042] The memory 233 stores the counter value under the control of the count control unit 231. The memory 233 outputs the stored counter value to the communication unit 223.

[0043] In addition to the reflected light of the irradiated light, natural light and attack light may also be incident on the light receiving unit 210. Therefore, even if the number of times of emission per light emission period is one, the number of times of light reception during that period is not necessarily one. For this reason, the counter unit 230 may output multiple counter values ​​during the light emission period.

[0044] 4 is a block diagram showing an example of the configuration of the light emitting unit 110 according to the first embodiment of the present technology. The light emitting unit 110 includes a light emission timing signal generating unit 111, a driver 112, and a light emitting element 113.

[0045] The light emission timing signal generating section 111 generates a pulsed light emission timing signal in response to a light emission instruction from the time management section 220 and supplies the signal to the driver 112 .

[0046] The driver 112 drives the light emitting element 113 in accordance with the light emitting timing signal from the light emitting timing signal generating section 111 .

[0047] Illumination light is emitted by the light emitting element 113. For example, a vertical cavity surface emitting laser (VCSEL) is used as a light source for the light emitting element 113. Two or more light emitting elements 113 can be arranged in the light emitting section 110.

[0048] 5 is a block diagram showing an example of the configuration of the distance calculation unit 300 according to the first embodiment of the present technology. The distance calculation unit 300 includes a communication unit 310, an intermediate data calculation unit 320, a histogram generation unit 330, a detection unit 340, and a distance data calculation unit 350.

[0049] The communication section 310 receives the counter value and the delay amount for each pixel from the time management section 220 and supplies them to the intermediate data calculation section 320 .

[0050] The intermediate data calculation unit 320 calculates intermediate data. This intermediate data calculation unit 320 calculates the difference between the time indicated by the counter value and the delay amount for each pixel. This difference indicates the light reception timing within the light emission period. The intermediate data calculation unit 320 calculates data indicating this light reception timing for each pixel and supplies it to the histogram generation unit 330 as intermediate data.

[0051] Here, the number of times that the irradiated light is emitted within the light emitting period is one or more times, and the light receiving section 210 receives the reflected light of the irradiated light for each pixel one or more times for each light emitting period.

[0052] The intermediate data calculation section 320 can also generate a part or all of a histogram based on one or more light receiving timings and output it as intermediate data.

[0053] The histogram generating unit 330 generates a histogram for each pixel by integrating (in other words, accumulating) the number of times the light receiving unit 210 receives light for each time within an accumulation period based on the intermediate data. The histogram generating unit 330 supplies the generated histogram to the detecting unit 340. An example of setting the accumulation period will be described later.

[0054] When the histogram contains multiple peaks that satisfy predetermined conditions, the detection unit 340 prioritizes the peak closest to the start time of the accumulation period (in other words, the leading peak) and detects it as the peak of normal reflected light (in other words, self-emission light). This excludes peaks of light emitted from sources other than the light-emitting unit 110, making it possible to prevent erroneous distance data from being output due to accidentally occurring light from other light sources (such as natural light). The detection unit 340 supplies the time corresponding to the detected normal peak to the distance data calculation unit 350.

[0055] Distance data calculation unit 350 calculates the time from the irradiation timing to the timing of the peak detected by detection unit 340 (i.e., the light reception timing), and calculates the distance by multiplying this time by the speed of light. Distance data is calculated for each pixel, and data including the distance data for each pixel is called a "frame."

[0056] 6 is a diagram showing an example of the relationship between a frame period, a histogram generation period, and a light emission period according to the first embodiment of the present technology. The frame period indicates a period during which the above-described frames are generated. When two or more frames are generated consecutively, the lengths of the frame periods may be the same, and the frame period may also be called a frame period.

[0057] Each frame period includes a single or multiple histogram generation periods TM, such as TM1 and TM2. The histogram generation period TM indicates the period during which a histogram is generated. The histogram generation period TM may be periodic or aperiodic. If the histogram generation period TM is periodic, the lengths of the histogram generation periods TM are the same, such as TM1 = TM2. On the other hand, if the histogram generation period TM is aperiodic, multiple histogram generation periods TM of different lengths, such as TM1 ≠ TM2, are arranged within the frame period. If the number of rows (or areas) in the light receiving unit 210 is M (M is an integer) and the light receiving unit 210 is driven in row (or area) units, the number of histogram generation periods within the frame period is M.

[0058] Each of the histogram generation periods includes a single or multiple light emission periods TS, such as TS1, TS2, etc. The light emission periods TS may be periodic or non-periodic. Note that the light emission periods TS1 and TS2 are examples of the first and second light emission periods set forth in the claims.

[0059] A predetermined period within the light emission period TS is referred to as an "accumulation period." The histogram generation unit 330 generates a histogram by accumulating (accumulating) the number of light receptions for each time within the accumulation period during the histogram generation period. The horizontal axis of this histogram represents time within the accumulation period, and the vertical axis represents the frequency (i.e., the number of light receptions at that time). Note that a lead time may be provided between the light emission timing and the start timing of the accumulation period. For example, if the number of light emission periods included in the histogram generation period is N (N is an integer), the number of light emission times per light emission period is one, and the number of SPADs constituting the ToF pixel unit is O (O is an integer), the maximum frequency is N × O. However, the maximum frequency may be limited to less than N × O.

[0060] 7 is a timing chart showing an example of the operation of the light emitting unit 110 and the ToF sensor 200 according to the first embodiment of the present technology. In the figure, "a" is a timing chart showing an example of the light emitting operation of the light emitting unit 110. In the figure, "b" is a timing chart showing an example of the operation of the light receiving unit 210 in the ToF sensor 200. In the figure, "c" is a timing chart showing an example of the operation of the time management unit 220 in the ToF sensor 200.

[0061] In the figure, the vertical axis of a indicates the signal level of the light emission timing signal, and the horizontal axis indicates time. In the first embodiment, the light emitting unit 110 emits light only once within the light emission period TS. The delay amount of the light emission timing relative to the start timing of the light emission period TS is referred to as the "offset time." In the figure, a delay amount TDa1 from the start timing T0 of the light emission period TS1 to the light emission timing signal corresponds to the offset time within TS1. A delay amount TDa2 from the start timing T1 of the light emission period TS2 to the light emission timing signal corresponds to the offset time within TS2.

[0062] The offset time for each light-emitting period may be the same, or multiple different offset times may be set. For example, TDa1 = TDa2, or TDa1 ≠ TDa2. Alternatively, the light-emitting unit 110 may emit light simultaneously with the start timing of the light-emitting period TS without providing an offset time.

[0063] As will be described later, the light emitting unit 110 can emit light multiple times within the light emitting period TS. The operation of emitting light multiple times within the light emitting period TS is called "burst light emission."

[0064] In the figure, the vertical axis of b represents the light receiving intensity of the light receiving unit 210, and the horizontal axis represents time. The light receiving unit 210 receives reflected light at timings t1 and t2 and generates a pulse signal. Note that there is no guarantee that the light receiving unit 210 can reliably detect the reflected light, so a pulse signal may not be generated within the light emission period TS. Furthermore, since natural light and attack light may also be incident on the light receiving unit 210 in addition to reflected light from the irradiated light, even if the number of light emissions per light emission period TS is one, the number of pulse signals within that period is not necessarily one.

[0065] In the figure, the vertical axis of c represents the counter value, and the horizontal axis represents time. The time management unit 220 initializes the counter value at the start of the light emission period and increments the counter value as time passes. The time management unit 220 obtains the counter value at light reception timings such as timing t1 and t2 and transmits it to the distance calculation unit 300.

[0066] 8 is a diagram illustrating a long-distance spoofing attack. The portion a in the figure is a timing chart showing an example of the light-emitting operation of the light-emitting unit 110. The portion b in the figure is a timing chart showing an example of the operation of the light-receiving unit 210 when a long-distance spoofing attack is performed.

[0067] As illustrated in FIG. 10A, when an offset time is inserted for each light emission period TS, a distance spoofing attack may be carried out.

[0068] For example, as illustrated in FIG. 1B, if times t1 and t3 are the normal light-receiving timings for reflected light from the self-emission light, an attacker may inject attack light at times t2 and t4 synchronized with the reflected light. Timing t2 is the timing immediately after timing t1, and timing t4 is the timing immediately after timing t3. In this case, the attack is carried out with the intention of making the distance appear farther than the actual distance.

[0069] However, as described above, when a histogram includes multiple peaks that satisfy a predetermined condition, the detector 340 detects the preceding peak with priority, which makes it possible to prevent long-distance spoofing attacks.

[0070] 9 is a diagram showing an example of light emission timing and a histogram according to the first embodiment of the present technology, where a in the figure shows the light emission timing within the light emission period TS, and b in the figure shows an example of a histogram for the accumulation period TH.

[0071] As shown in FIG. 1A, the offset time from the start timing of the light-emitting period TS to the light-emitting timing is defined as a delay amount TDa. Also, a predetermined timing immediately before the end timing of the light-emitting period TS is defined as te. In this case, as shown in FIG. 1B, the accumulation period TH is set from the timing at which the delay amount (offset time) TDa has elapsed to the timing te.

[0072] When a histogram is generated by integrating the number of times light is received for each time during this accumulation period TH, multiple peaks such as peaks P1, P2, and P3 may appear, as shown in FIG.

[0073] In an actual measurement environment, reflections may occur not only from objects to be measured, such as people, cars, and signs, but also from objects outside the object to be measured, such as rain, fog, and smoke. Therefore, a peak P1 of reflection from rain, fog, or smoke may appear before a peak P2 of light reflected from the object to be measured.

[0074] In order to accurately measure the distance to the subject, it is preferable to remove peak P1 that precedes peak P2. Peaks P1 and P2 are likely to have different peak frequencies and time distribution trends. Therefore, the detection unit 340 determines whether predetermined conditions regarding the peak frequencies and time distribution trends are met.

[0075] For example, the detection unit 340 determines whether the frequency of the peak exceeds a fixed or variable threshold. When the threshold is variable, the threshold is set by a function Th(t) that returns a smaller threshold as the time t from the start timing of the accumulation period becomes longer. The dashed-dotted line in the figure shows an example of the locus of the function Th(t).

[0076] Furthermore, as the time distribution tendency, for example, the kurtosis of the distribution including the peak is calculated, and it is determined whether or not the kurtosis is higher than a predetermined value.

[0077] The detection unit 340 may set the predetermined condition to be that the frequency of the peak exceeds a threshold, or that the kurtosis is higher than a predetermined value, or that the frequency of the peak exceeds the threshold and that the kurtosis is higher than a predetermined value.

[0078] If there are multiple peaks that satisfy the predetermined conditions, the detection unit 340 prioritizes the peak that is closest to the start timing of the accumulation period (in other words, the earlier peak) and detects it as the legitimate peak. In the figure, peak P1 does not satisfy the predetermined conditions, while peaks P2 and P3 do. Of these, the earlier peak P2 is detected with priority. This makes it possible to prevent long-distance spoofing attacks.

[0079] 10 is a flowchart showing an example of the operation of the distance measuring device 100 according to the first embodiment of the present technology. This operation is started, for example, when a predetermined application for performing distance measurement is executed.

[0080] The light-emitting unit 110 starts emitting light (step S901), and the light-receiving unit 210 starts receiving reflected light of the irradiated light to generate a pulse signal (step S902). The time management unit 220 generates intermediate data based on the pulse signal (step S903), and the distance calculation unit 300 generates a histogram by a histogram generation process (step S904). Here, the histogram generation method in the first embodiment is referred to as the "first method."

[0081] The distance calculation unit 300 determines whether or not there is a peak in the histogram that satisfies a predetermined condition (step S905).

[0082] If there is a peak that satisfies the predetermined condition (step S905: Yes), the distance calculation unit 300 determines whether there are two or more peaks that satisfy the predetermined condition (step S906). If there are two or more peaks that satisfy the predetermined condition (step S906: Yes), the distance calculation unit 300 measures the distance based on the timing of the preceding peak (step S907). If there is only one peak that satisfies the predetermined condition (step S906: No), the distance calculation unit 300 measures the distance based on the timing of that peak (step S908).

[0083] If there is no peak that satisfies the predetermined condition (step S905: No), or after step S907 or S908, the distance calculation unit 300 determines whether the frame period has ended (step S909).

[0084] If the frame period has not ended (step S909: No), the distance calculation unit 300 repeatedly executes steps S903 and thereafter. On the other hand, if the frame period has ended (step S909: Yes), the distance calculation unit 300 outputs the frame and ends the operation for distance measurement.

[0085] When a plurality of frames are generated consecutively, steps S903 to S909 are repeatedly executed in synchronization with a synchronization signal such as a vertical synchronization signal.

[0086] As described above, according to the first embodiment of the present technology, the detection unit 340 detects the preceding peaks from among multiple peaks that satisfy a predetermined condition, thereby preventing long-distance spoofing attacks.

[0087] In the first embodiment described above, the intermediate data is calculated by the distance calculation unit 300 downstream of the ToF sensor 200, but this configuration is not limiting. The distance measuring device 100 in this modification of the first embodiment differs from the first embodiment in that the intermediate data is calculated on the ToF sensor 200 side.

[0088] 11 is a block diagram showing an example of a configuration of a ToF sensor 200 according to a modification of the first embodiment of the present technology. The ToF sensor 200 according to the modification of the first embodiment differs from the first embodiment in that an intermediate data calculation unit 224 is further included in the time management unit 220.

[0089] The intermediate data calculation unit 224 calculates intermediate data by the same process as in the first embodiment, based on the counter value and the delay amount from the counter unit 230 and the delay amount instruction unit 222. The intermediate data calculation unit 224 supplies the calculated intermediate data to the communication unit 223. In the distance calculation unit 300 at the subsequent stage, the intermediate data calculation unit 320 is omitted.

[0090] As illustrated in the figure, by calculating intermediate data on the ToF sensor 200 side, the amount of processing on the distance calculation unit 300 side can be reduced.

[0091] As described above, according to the modification of the first embodiment of the present technology, the ToF sensor 200 calculates intermediate data, so that the amount of processing on the distance calculation unit 300 side can be reduced.

[0092] 2. Second Embodiment In the first embodiment described above, the detection unit 340 prevents long-distance spoofing attacks by detecting the preceding peaks preferentially among a plurality of peaks that satisfy a predetermined condition.

[0093] However, as illustrated in Fig. 12, a close-range spoofing attack may also be carried out. In Fig. 12, "a" is a timing chart showing an example of the light-emitting operation of the light-emitting unit 110. "b" is a timing chart showing an example of the operation of the light-receiving unit 210 when a close-range spoofing attack is carried out.

[0094] As shown in the example of b in the figure, if the timing of receiving the normal reflected light within the light emission period TS2 is timing t5, an attacker may inject attack light at the preceding timings t2, t3, or t4. In this case, the attack is carried out with the intention of making the distance appear closer than the actual distance. In the first embodiment, it is difficult to prevent such short-distance spoofing attacks.

[0095] The distance measuring device 100 in the second embodiment differs from the first embodiment in that it prevents close-range spoofing attacks by using burst light emission.

[0096] 13 is a diagram showing an example of light emission timing and a histogram according to the second embodiment of the present technology, where "a" in the figure shows the light emission timing within the light emission period TS1, and "b" in the figure shows an example of a histogram for the accumulation period TH1.

[0097] As shown in the diagram a, the light-emitting unit 110 emits light multiple times (for example, three times) during the light-emitting period TS1. The delay amount until the first of the three light-emitting times corresponds to the delay amount (offset time) TDa1. The delay amount (in other words, the interval) from the first light-emitting time to the second light-emitting time is TDb1, and the delay amount (interval) from the second light-emitting time to the third light-emitting time is TDc1. These delay amounts TDa1, TDb1, and TDc1 are set by the delay amount specifying unit 222.

[0098] It is preferable that the intervals (TDb1, TDc1, etc.) between the second and subsequent light emission timings do not overlap. In the example of a in the figure, it is preferable that TDb1≠TDc1.

[0099] As shown in FIG. 1B, if the peak group of reflected light from the subject of distance measurement is Gr2, then Gr1, which is a peak group of reflection from rain, fog, or smoke, may appear before Gr2.

[0100] In order to accurately measure the distance to the subject, it is preferable to remove the peak group Gr1 that precedes the peak group Gr2. The peak intervals between the peak groups Gr1 and Gr2 are similar, but the frequency of the peaks and the time distribution trends are likely to differ. Therefore, the detection unit 340 determines whether predetermined conditions regarding the frequency of the peaks and the time distribution trends are satisfied.

[0101] If there are multiple peaks that satisfy the specified conditions, the detection unit 340 prioritizes detecting the preceding peak as the legitimate peak. In the figure, in the area indicated by b, the peaks in peak group Gr1 do not satisfy the specified conditions, while the peaks in peak groups Gr2 and Gr3 satisfy the specified conditions. Of these, the three peaks in the preceding peak group Gr2 are prioritized for detection. This makes it possible to prevent long-distance spoofing attacks.

[0102] The distance data calculation unit 350 calculates the distance based on the light emission timing of at least one of the three burst-emitted irradiated light beams and the light reception timing of at least one of the three peaks in peak group Gr2. For example, the distance is calculated from the first light emission timing and the light reception timing of the first peak in peak group Gr2. Furthermore, when all three light emission timings and the light reception timings of the three peaks in peak group Gr2 are used, three distances are calculated, and their statistics (such as the average value) are calculated as the final distance.

[0103] 14 is a diagram illustrating an example of a delay amount according to the second embodiment of the present technology. The histogram generation period includes light emission periods TS1 and TS2. The delay amount (offset time) until the first light emission timing within light emission period TS1 is set to TDa1, and the delay amount (offset time) until the first light emission timing within light emission period TS2 is set to TDa2.

[0104] In addition, in the light emission period TS1, the delay amount (interval) from the first light emission timing to the second light emission timing is TDb1, and the delay amount (interval) from the second light emission timing to the third light emission timing is TDc1. In the light emission period TS2, the delay amount (interval) from the first light emission timing to the second light emission timing is TDb2, and the delay amount (interval) from the second light emission timing to the third light emission timing is TDc2.

[0105] The lengths of the light emission periods TS1 and TS2 may be the same or different.

[0106] Furthermore, it is preferable that at least some of the light emission timings in the light emission period TS1 are different from some of the light emission timings in the adjacent light emission period TS2. In the figure, for example, it is preferable that at least one of the following three equations is satisfied: TDa1≠TDa2 (TDa1+TDb1)≠(TDa2+TDb2) (TDa1+TDb1+TDc1)≠(TDa2+TDb2+TDc2)

[0107] Furthermore, it is preferable that TDb and TDc, which are the intervals between light emission timings, are randomly selected from a predetermined group of options including a plurality of options. For example, the delay amount specifying unit 222 generates a true random number or a pseudo-random number, selects an option corresponding to the random number from the group of options, and sets it as TDb or TDc.

[0108] Alternatively, it is preferable that TDb1, TDc1, TDb2, and TDc2 are selected in a random order. For example, if the group of options includes options S1, S2, S3, S4, etc., and four of these are selected and arranged, the arrangement order (i.e., permutation) is 4! possible. The delay amount specifying unit 222 randomly selects one of all possible arrangement orders (e.g., 4! possible). Assume that the selected arrangement order is, for example, S1, S3, S2, and S4. In this case, the delay amount specifying unit 222 sets S1 to TDb1, S3 to TDc1, S2 to TDb2, and S4 to TDc2.

[0109] It is also preferable that the intervals within the light emission period do not overlap. In the example shown in the figure, it is preferable that TDb1≠TDc1 and TDb2≠TDc2.

[0110] Furthermore, the detection unit 340 performs detection by adding a predetermined condition that the interval between peaks in the histogram matches the TDb (TDb1, etc.) and TDc (TDc1, etc.) on the light-emitting side.

[0111] As described above, by setting the delay amount, an attacker cannot synchronize the attack light for short-distance spoofing with the regular reflected light, which makes it possible to prevent short-distance spoofing attacks in addition to long-distance spoofing attacks.

[0112] Similarly to the first embodiment, the histogram generation unit 330 integrates the number of light receptions using the accumulation period TH1 as the period from the time when the delay (offset time) TDa1 of the light emission period TS1 has elapsed to the timing te immediately before the end timing. Similarly to the first embodiment, the histogram generation unit 330 integrates the number of light receptions using the accumulation period TH2 as the period from the time when the delay (offset time) TDa2 of the light emission period TS2 has elapsed to the timing te immediately before the end timing. Similarly to the first embodiment, the histogram generation method of the second embodiment is also the first method.

[0113] The histogram generation period may further include a light-emitting period TS3 having delay amounts TDa3, TDb3, and TDc3 in addition to the light-emitting periods TS1 and TS2. The histogram generation period may further include a light-emitting period TS4 and subsequent periods for which delay amounts are individually set.

[0114] The three light beams emitted during the light emission period are examples of the first, second, and third light beams described in the claims. The delay amounts TDb and TDc are examples of the first interval and the second interval described in the claims.

[0115] Thus, according to the second embodiment of the present technology, the light emitting unit 110 emits burst light, and the delay amount indication unit 222 individually sets the delay amount for each of the light emitting periods TS1 and TS2, so that close-range spoofing attacks can also be prevented.

[0116] 3. Third Embodiment In the second embodiment described above, the histogram was generated using the first method, but it is also possible to generate a histogram using a different method. The distance measuring device 100 in this third embodiment differs from the first embodiment in that the frequency of another histogram is re-stored in the frequency of a histogram so that multiple peaks coincide.

[0117] 15 is a diagram showing an example of an accumulation period according to the third embodiment of the present technology. In the figure, "a" indicates an accumulation period within a light-emitting period TS1, and "b" indicates an accumulation period within a light-emitting period TS2. For ease of explanation, hereinafter, the start timing of the light-emitting periods TS1 and TS2 is set to "0."

[0118] As shown in FIG. 10A, in the third embodiment, the light emitting unit 110 emits light three times based on the delay amounts TDa1, TDb1, and TDc1 within the light emitting period TS1.

[0119] The period from when TDa1 has elapsed within the light-emitting period TS1 to when te is defined as the accumulation period THa1. The period from when (TDa1 + TDb1) has elapsed within the light-emitting period TS1 to when te is defined as the accumulation period THb1. The period from when (TDa1 + TDb1 + TDc1) has elapsed within the light-emitting period TS1 to when te is defined as the accumulation period THc1. The histogram generating unit 330 in the third embodiment integrates the number of light receptions within these accumulation periods to generate a histogram.

[0120] As illustrated in FIG. 11B, within the light emission period TS2, the accumulation periods THa2, THb2, and THc2 are set based on the delay amounts TDa2, TDb2, and TDc2.

[0121] The accumulation periods THa1 and THb1 are examples of the first and second accumulation periods set forth in the claims.

[0122] 16 is a block diagram showing an example configuration of a histogram generation unit 330 according to the third embodiment of the present technology. The histogram generation unit 330 according to the third embodiment includes storage units 331, 332, and 333, accumulation processing units 334, 335, and 336, and a re-accumulation processing unit 337.

[0123] The accumulation processing unit 334 accumulates the number of times light is received for each time within the accumulation period THa1 based on the delay amount and the counter value, and generates a histogram HSa1. This histogram HSa1 is held in the storage unit 331.

[0124] The accumulation processing unit 335 accumulates the number of times light is received for each time within the accumulation period THb1 based on the delay amount and the counter value, and generates a histogram HSb1. This histogram HSb1 is held in the storage unit 332.

[0125] The accumulation processing unit 336 accumulates the number of times light is received for each time within the accumulation period THc1 based on the delay amount and the counter value, and generates a histogram HSc1. This histogram HSc1 is held in the storage unit 333.

[0126] The re-storage processing unit 337 re-stores the frequencies of histograms HSb1 and HSc1 in the frequency of histogram HSa1 so that the peaks of each histogram coincide. For example, the re-storage processing unit 337 reads histogram HSb1 from the storage unit 332 and re-stores the frequency of histogram HSb1 in the frequency of histogram HSa1 in the storage unit 331. The re-stored histogram is designated as HSa1'. Next, the re-storage processing unit 337 reads histogram HSc1 from the storage unit 333 and re-stores the frequency of histogram HSc1 in the frequency of histogram HSa1' in the storage unit 331. The re-storage processing unit 337 then reads the re-stored histogram from the storage unit 331 and outputs it as the final histogram HS1.

[0127] For the light emission period TS2, histograms HSa2, HSb2 and HSc2 are generated, and the histogram HS2 is generated by re-accumulating them.

[0128] The histograms HSa1 and HSb1 are examples of the first and second histograms set forth in the claims.

[0129] 17 is a diagram showing an example of a histogram before re-accumulation according to the third embodiment of the present technology. In the figure, "a" is an example of a histogram HSa1 generated by the histogram generation unit 330 accumulating the number of times of light reception for each time within an accumulation period THa1. In the figure, "b" is an example of a histogram HSb1 generated by the histogram generation unit 330 accumulating the number of times of light reception for each time within an accumulation period THb1. In the figure, "c" is an example of a histogram HSc1 generated by the histogram generation unit 330 accumulating the number of times of light reception for each time within an accumulation period THc1.

[0130] As illustrated in the figure, the start timing (TDa1+TDb1) of the accumulation period THb1 is delayed by the delay amount TDb1 relative to the start timing (TDa1) of the accumulation period THa1. Therefore, when the histogram generating unit 330 re-accumulates the histogram HSb1 in the histogram HSa1, it re-accumulates the frequency of the histogram HSb1 from time t-TDb1 into the frequency of the histogram HSa1 at time t.

[0131] Furthermore, the start timing of the accumulation period THc1 (TDa1+TDb1+TDc1) is delayed by the delay amount (TDb1+TDc1) relative to the start timing (TDa1) of the accumulation period THa1. Therefore, when the histogram generator 330 re-stores the histogram HSc1 in the re-stored histogram HSa1, it re-stores the frequency of the histogram HSc1 at time t-(TDb1+TDc1) as the frequency of the histogram HSa1 at time t. This re-store process allows the peak of the histogram HSa1 to coincide with the peaks of the histograms HSb1 and HSc1. In the figure, the start times of the histograms HSb1 and HSc1 (in other words, the left ends) are aligned with the start time of the histogram HSa1.

[0132] Fig. 18 is a diagram showing an example of a histogram re-accumulated within a light emission period TS1 according to the third embodiment of the present technology. The histogram HS1 of Fig. 18 is obtained by re-accumulating the histograms HSb1 and HSc1 of Fig. 17 b and c in Fig. 17 into the histogram HSa1 of Fig. 17 a.

[0133] As described above, the histogram generator 330 has performed re-storage so that the peaks of the histograms HSa1, HSb1, and HSc1 coincide with each other, and therefore, as shown in the figure, the frequency of the specific peak P1 increases compared to when re-storage is not performed. Therefore, the detector 340 does not need to determine whether the intervals between the peaks are TDb and TDb, as in the second embodiment.

[0134] Furthermore, peaks P1 and P2 that satisfy a predetermined condition appear in the histogram, but the detector 340 preferentially detects the preceding peak P1.

[0135] The method of generating a histogram by re-accumulation illustrated in FIGS. 17 and 18 will be referred to as the "second method."

[0136] 19 is a diagram showing an example of a histogram re-accumulated within a light emission period TS2 according to the third embodiment of the present technology. As illustrated in the drawing, a histogram HS2 is generated by re-accumulation also during the light emission period TS2.

[0137] 20 is a flowchart showing an example of the operation of the distance measuring device 100 according to the third embodiment of the present technology. The operation of the distance measuring device 100 according to the third embodiment differs from that of the first embodiment in that step S910 is executed instead of step S904.

[0138] After generating the intermediate data (step S903), the histogram generating unit 330 executes a histogram generating process using the second method (step S910).

[0139] 21 is a flowchart showing an example of a histogram generation process according to the third embodiment of the present technology. The histogram generation unit 330 initializes each of the storage units 331 to 333 (step S911) and starts storing the histogram HSa (HSa1 or HSa2) in the storage unit 331 (step S912). Then, the histogram generation unit 330 starts storing the histogram HSb (HSb1 or HSb2) in the storage unit 332 (step S913) and starts storing the histogram HSc (HSc1 or HSc2) in the storage unit 333 (step S914).

[0140] The histogram generator 330 then reads out the histogram HSb from the storage unit 332 and starts restoring it to the histogram HSa in the storage unit 331 (step S915). The histogram generator 330 then reads out the histogram HSc from the storage unit 333 and starts restoring it to the histogram HSa in the storage unit 331 (step S916). When the histogram is generated after step S916, the histogram generator 330 ends the histogram generation process.

[0141] In the second embodiment described above, while it is possible to change the set value of the delay amount TDa for each light emission period TS, there are cases where it is not possible to change the set values ​​of the delay amounts TDb and TDc for each light emission period TS. In other words, there are cases where it is necessary to make the light emission patterns based on the delay amounts TDb and TDc the same for multiple light emission periods TS in which histograms are continuously accumulated. This is because a histogram that is correlated with the light emission pattern is required.

[0142] In contrast, in the third embodiment, in addition to the delay amount TDa, the delay amounts TDb and TDc can also be freely changed for each light emission period TS. For this reason, the third embodiment is considered to be more difficult for an attacker to execute than the second embodiment.

[0143] Furthermore, in the third embodiment, the histograms can be re-accumulated continuously during the light emission periods TS1 and TS2.

[0144] 22 shows a histogram obtained by successively re-accumulating the histograms during the light emission periods TS1 and TS2. As shown in the figure, the frequency of peaks further increases, improving noise resistance.

[0145] As described above, according to the third embodiment of the present technology, the histogram generating unit 330 re-stores the histograms HSb and HSc in the histogram HSa so that the peaks match, thereby improving noise resistance.

[0146] [First Modification] In the third embodiment described above, the histogram generation unit 330 stores histograms in each of the storage units 331 to 333. However, it is preferable to reduce the number of storage units. The distance measuring device 100 in this first modification of the third embodiment differs from the third embodiment in that the storage unit 333 is eliminated by shifting and re-storing the histograms.

[0147] 23 is a block diagram showing an example configuration of a histogram generation unit 330 in a first modified example of the third embodiment of the present technology. The histogram generation unit 330 in the first modified example of the third embodiment differs from the third embodiment in that it further includes a re-storage processing unit 338 and eliminates the storage unit 333, the storage processing unit 335, and the storage processing unit 336.

[0148] In the first modification of the third embodiment, the accumulation processing unit 334 accumulates the histogram HSa in the storage units 331 and 332 .

[0149] The re-storage processing unit 337 reads out the histogram HSa from the storage unit 331 and shifts the histogram by the delay amount TDb in the direction going back in time along the time axis. For example, if the direction going back in time is the left direction, the histogram is shifted left. The re-storage processing unit 337 re-stores the frequency of the shifted histogram as the frequency of the histogram HSa. The histogram after re-storage is designated as HSa'.

[0150] The re-storage processing unit 338 then reads out the histogram HSa from the storage unit 332 and shifts (e.g., shifts left) the histogram in the direction going back in time along the time axis by the delay amount (TDb+TDc). The re-storage processing unit 338 re-stores the frequency of the shifted histogram as the frequency of the histogram HSa' in the storage unit 331. The re-storage processing unit 338 then reads out the re-stored histogram from the storage unit 331 and outputs it as the final histogram HS.

[0151] The above-described process generates a histogram similar to that in the third embodiment, which results in a reduction in the storage unit 333.

[0152] 24 is a flowchart illustrating an example of a histogram generation process according to a first modified example of the third embodiment of the present technology. The histogram generation process according to the first modified example of the third embodiment differs from the third embodiment in that steps S921 and S922 are executed instead of steps S913 to S916.

[0153] The histogram generating unit 330 initializes the storage units 331 and 332 (step S911) and starts storing the histogram HSa in the storage units 331 and 332 (step S912).

[0154] The histogram generator 330 then reads out the histogram HSa from the storage unit 331, shifts it by TDb, and starts re-accumulating it in the histogram HSa in the storage unit 331 (step S921). The histogram generator 330 then reads out the histogram HSa from the storage unit 332, shifts it by (TDb+TDc), and starts re-accumulating it in the histogram HSa' in the storage unit 331 (step S922).

[0155] 25 is a diagram showing an example of a histogram according to a first modified example of the third embodiment of the present technology. In the figure, "a" shows an example of a histogram before shifting that is stored in the storage units 331 and 332. In the figure, "b" and "c" show examples of a histogram after shifting.

[0156] As described above, the histogram generator 330 reads out the histogram HSa from the storage unit 331 and shifts it to the left by TDb. This generates the histogram b in the figure. The histogram b in the figure is then re-stored in the histogram a in the storage unit 331.

[0157] The histogram generator 330 then reads out the histogram HSa from the storage unit 332 and shifts it to the left by (TDb+TDc). This generates the histogram c in the figure. The histogram c in the figure is then re-stored in the histogram HSa' in the storage unit 331.

[0158] Although the histogram generator 330 shifts the histogram in the direction going backward in time (e.g., to the left), it can also shift the histogram in the direction going forward in time (e.g., to the right). In this case, the histogram generator 330 reads the histogram HSa from the storage unit 331, shifts it to the right by TDc, and reads the histogram HSa from the storage unit 332, and shifts it to the right by (TDb+TDc).

[0159] The histogram generator 330 can also perform both a process of shifting the histogram backward in time (e.g., to the left) and a process of shifting the histogram forward in time (e.g., to the right). In this case, the histogram generator 330 reads the histogram HSa from the storage unit 331 and shifts it to the right by TDb, and reads the histogram HSa from the storage unit 332 and shifts it to the left by TDc.

[0160] As described above, according to the first modified example of the third embodiment of the present technology, the histogram generating unit 330 shifts and re-stores the histogram, so that the storage unit 333 can be reduced.

[0161] [Second Modification] In the third embodiment described above, histogram generation unit 330 stores histograms in each of storage units 331 to 333, but it is preferable to reduce the number of storage units. Range finding device 100 in this second modification of the third embodiment differs from the third embodiment in that storage units 332 and 333 are reduced by restoring histogram element units.

[0162] 26 is a block diagram showing an example configuration of a histogram generation unit 330 in a second modified example of the third embodiment of the present technology. The histogram generation unit 330 in the second modified example of the third embodiment differs from the third embodiment in that the storage units 332 and 333 and the re-storage processing unit 338 are omitted.

[0163] The re-storage processing unit 337 selects elements (in other words, bins) from the histogram stored in the storage unit 331 in chronological order from the point in time after (TDa + TDb + TDc) has elapsed since the start of the storage period. The re-storage processing unit 337 reads the selected elements and elements TDc before them from the storage unit 331, and re-stores them as elements (TDb + TDc) before the selected elements. The histogram generation unit 330 performs the above-described re-storage each time an element is selected, up to the last element of the histogram, reads the re-stored histogram from the storage unit 331, and outputs it as the final histogram HS.

[0164] The above-described process generates a histogram similar to that in the third embodiment, which results in a reduction in the storage units 332 and 333.

[0165] 27 is a flowchart illustrating an example of a histogram generation process according to a second modified example of the third embodiment of the present technology. The histogram generation process according to the first modified example of the third embodiment differs from the third embodiment in that steps S931 to S934 are executed instead of steps S913 to S916.

[0166] The histogram generating unit 330 initializes the storage unit 331 (step S911) and starts storing the histogram HSa in the storage unit 331 (step S912).

[0167] After the histogram HSa is generated, the histogram generator 330 selects one of the elements from the point in time after (TDa + TDb + TDc) has elapsed since the start of the accumulation period (step S931). From the second time onward, step S931 selects an element later than the previous time. The histogram generator 330 then reads from the storage unit 331 an element that precedes the selected element by TDc, and stores it again as an element (TDb + TDc) before the selected element (step S932). The histogram generator 330 also reads from the storage unit 331 the selected element, and stores it again as an element (TDb + TDc) before the selected element (step S933).

[0168] The histogram generator 330 then determines whether the selected element is the last element in the histogram HSa (step S934). If the selected element is not the last element (step S934: No), the histogram generator 330 repeatedly executes steps S931 and onward. If the selected element is the last element (step S934: Yes), the histogram generator 330 ends the histogram generation process.

[0169] FIG. 28 is a diagram illustrating an example of a histogram according to a first modified example of the third embodiment of the present technology.

[0170] As shown in FIG. 1A, the histogram generator 330 selects the element at timing t3 in the histogram. At this time, the histogram generator 330 reads the element at timing t3 and the element at timing t2, which is TDc before timing t3, from the storage unit 331, and stores them again as the element at timing t1, which is TDb before timing t2. As a result, the histogram shown in FIG. 1B is generated.

[0171] The histogram generator 330 can also re-store, into the selected element, the element that occurred TDc before the selected element and the element that occurred (TDb+TDc) before the selected element. In the example shown in the figure, the histogram generator 330 re-stores, into the element at timing t3, the elements from the previous timings t1 and t2.

[0172] The third embodiment and its first and second variations share the commonality that the histogram generator 330 re-accumulates the histogram so that multiple peaks in the histogram coincide on the time axis, thereby generating a final histogram. The histogram generator 330 may perform a process other than re-accumulation as long as the peaks coincide. In that case, the re-accumulation process may be unnecessary. The peak coincidence process may also be a pseudo-peak coincidence process. For example, a non-burst emission may be performed in which the number of emissions per emission period is set to one, and at least some of the elements corresponding to TDb, TDc, and TDb+TDc are shifted in the same manner as in the peak coincidence process (pseudo-peak coincidence process). In this case, the signal levels of the multiple beams of illumination emitted in bursts may be the same or different. Therefore, by setting at least some of the signal levels, excluding the signal level of the final beam of illumination in a burst, to a reference value or below (e.g., zero), it can be interpreted that some of the multiple beams of illumination emitted in bursts have been omitted.

[0173] As described above, according to the second modification of the third embodiment of the present technology, the histogram generation unit 330 re-stores the histogram element by element, and therefore the storage units 332 and 333 can be reduced.

[0174] [Third Modification] In the first modification of the third embodiment described above, the intervals of the light emission timing signals are set to TDb and TDc, but it is preferable that the delay amount specifying unit 222 randomly selects these intervals from a plurality of options having a predetermined relationship. The distance measuring device 100 in this third modification of the third embodiment differs from the first modification of the third embodiment in that the intervals of the light emission timing signals are randomly selected from a plurality of options having a predetermined relationship.

[0175] FIG. 29 is a diagram showing an example of a light emission timing signal within a light emission period TS in a third modified example of the third embodiment of the present technology.

[0176] In order to reduce erroneous ranging, it is preferable that the intervals (TDb, TDc, etc.) of the multiple light emission timing signals within the light emission period TS have a predetermined relationship. For example, it is preferable that the multiple intervals do not overlap with each other.

[0177] For example, the delay amount specifying unit 222 holds a group of options including at least a portion of a plurality of options with a ratio of "1:2:4:5:8:10:14:21...". The delay amount specifying unit 222 then randomly selects (number of times of light emission - 1) options from the group of options and sets them as the respective interval values. In the figure, "a" is an example of the light emission timing set using the group of options described above.

[0178] The delay amount specifying unit 222 can also use a group of options that includes at least some of the multiple options with a ratio of "2:3:4:6:8:11:16:17...." In the figure, "b" is an example of the light emission timing set using the group of options.

[0179] Alternatively, the delay amount specifying unit 222 can use a group of options including at least some of the multiple options with a ratio of "3:4:5:6:8:13:16:17...." In the figure, c is an example of the light emission timing set using the group of options.

[0180] If A is a real number and L is a natural number, it is preferable that the options in the option group do not fall under the L options obtained by multiplying consecutive natural numbers from 1 to L by A, such as "A x 1, A x 2, A x 3, A x 4, A x 5, A x 6, A x 7, A x 8 ... A x L." For example, it is preferable that, where K is a natural number smaller than L, the option group includes K options obtained by multiplying K natural numbers, some of which are missing from the consecutive natural numbers from 1 to L, by A. In the figure, a, b, and c indicate examples set using option groups having this relationship.

[0181] Furthermore, in order to concentrate the frequency at a specific peak and distribute the other peaks evenly, it is preferable that a focused option among the multiple options arranged in ascending order has a value smaller than that option and different from the sum of two or more consecutive options. For example, in a in the same figure, when focusing on "4," the sum of the consecutive options smaller than "4" is "3" (=1+2), which does not correspond to "4." When focusing on "5," the sum of the consecutive options smaller than "5" is "3," "6" (=2+4), or "7" (=1+2+4), none of which correspond to "5." When focusing on "8," the sum of the consecutive options smaller than "8" is "3," "6," "7," "9," "11," or "12," none of which correspond to "8." The same applies to "10" and onward.

[0182] In the figure, the intervals between the light emission timings are arranged in ascending order in a, b, and c, but this arrangement is merely an example. As mentioned above, the order of the intervals is not limited to ascending order and can be set randomly.

[0183] 30 is a diagram showing an example of light emission timing and a histogram in a third modified example of the third embodiment of the present technology. In the figure, "a" shows an example of light emission timing within a light emission period TS. In the figure, "b" shows the initially generated histogram. In the figure, "b," "c," "d," "e," and "f" show histograms shifted to the left. In the figure, "g" shows the final histogram obtained by re-accumulating "b," "c," "d," "e," and "f" in the figure.

[0184] The interval between light emission timing signals indicated by a in the figure is selected from a group of options containing K options, the value of which is obtained by multiplying K consecutive natural numbers from 1 to L, some of which are missing, by A. This relationship is referred to as the first relationship. Furthermore, among the multiple options arranged in ascending order in the group of options, the option of interest has a value smaller than that option and different from the sum of the values ​​of two or more consecutive options. This relationship is referred to as the second relationship. By having these relationships, the frequency of only a specific peak is concentrated, while the other peaks are evenly distributed, as illustrated by f in the figure. This further improves noise resistance.

[0185] In contrast to this, a configuration using a group of options that have the first relationship but do not have the second relationship is assumed as a first comparative example.

[0186] 31 is a diagram showing an example of light emission timing and a histogram in the first comparative example. In the figure, "a" shows an example of light emission timing within a light emission period TS. In the figure, "b" shows the initially generated histogram. In the figure, "b," "c," "d," "e," and "f" show histograms shifted to the left. In the figure, "g" shows the final histogram obtained by re-accumulating "b," "c," "d," "e," and "f" in the figure.

[0187] The interval between light emission timing signals indicated by a in the figure is selected from a group of options containing K options, the value of which is calculated by multiplying K consecutive natural numbers from 1 to L, some of which are omitted, by A. However, among the multiple options arranged in ascending order in the group of options, a focused option may have a smaller value than that option and may be equal to the sum of two or more consecutive options. For example, if one focuses on "5," the sum of two or more consecutive options that are smaller than that option is "5" (= 2 + 3). In this case, as illustrated by g in the figure, the frequency of only a specific peak is concentrated, while the other peaks are difficult to distribute evenly.

[0188] Also, a configuration in which multiple intervals overlap is considered as a second comparative example.

[0189] 32 is a diagram showing an example of light emission timing and a histogram in the second comparative example. In the figure, "a" shows an example of light emission timing within the light emission period TS. In the figure, "b" shows the initially generated histogram. In the figure, "b," "c," "d," "e," and "f" show histograms shifted to the left. In the figure, "g" shows the final histogram obtained by re-accumulating "b," "c," "d," "e," and "f" in the figure.

[0190] As shown in the example of a in the figure, all of the intervals have the same value. In this case, as shown in the example of g in the figure, the frequency is less likely to concentrate at a specific peak.

[0191] The third modified example can also be applied to the third embodiment, the first modified example of the third embodiment, and the second modified example of the third embodiment.

[0192] In this way, according to the third variant example of the third embodiment of the present technology, the delay amount indication unit 222 randomly selects from a plurality of options having a predetermined relationship and sets the interval between light emission timings, thereby further improving noise resistance.

[0193] 4. Fourth Embodiment In the first embodiment described above, the detection unit 340 prevents long-distance spoofing attacks by preferentially detecting the earliest peak among multiple peaks that satisfy a predetermined condition, but as mentioned above, short-distance spoofing attacks can also be carried out. The distance measuring device 100 in this fourth embodiment differs from the first embodiment in that it prevents short-distance spoofing attacks by using burst light emission with an appropriately set delay amount.

[0194] 33 is a diagram showing an example of the delay amount within a histogram generation period TM1 according to the fourth embodiment of the present technology. In the figure, "a" shows an example of the delay amount for each of light emission periods TS1 and TS2 within the histogram generation period TM1. In the figure, "b" shows an example of the delay amount for each of light emission periods TS3 and TS4 within the histogram generation period TM1.

[0195] 34 is a diagram showing an example of the delay amount within the histogram generation period TM2 according to the fourth embodiment of the present technology. In the figure, "a" shows an example of the delay amount for each of the light emission periods TS1 and TS2 within the histogram generation period TM2. In the figure, "b" shows an example of the delay amount for each of the light emission periods TS3 and TS4 within the histogram generation period TM2.

[0196] 33 and 34, the number of times light is emitted in each light-emitting period TS is 2. In addition, in each of the light-emitting periods TS1, TS2, TS3, and TS4, the delay amount until the first light emission is denoted by TDa1, TDa2, TDa3, and TDa4, and the delay amount from the first light emission to the second light emission is denoted by TDb1, TDb2, TDb3, and TDb4.

[0197] The two beams of light emitted during the light-emitting period TS1 are examples of the first and second beams of light emitted in the claims, and the two beams of light emitted during the light-emitting period TS2 are examples of the third and fourth beams of light emitted in the claims. The delay amounts TDa1 and TDa2 are examples of the first and second offset times.

[0198] The delay amount described above may be selected from the group of options across multiple light-emitting periods TS, or may be selected for each histogram generation period TM. Furthermore, the light-emitting period TS may be periodic or aperiodic. If the light-emitting period TS is periodic, TS1 = TS2 = TS3 = TS4. If the light-emitting period TS is aperiodic, at least one of TS1 ≠ TS2, TS1 ≠ TS3, TS1 ≠ TS4, TS2 ≠ TS3, TS2 ≠ TS4, and TS3 ≠ TS4 is true. Similarly, the histogram generation period TM may be periodic or aperiodic.

[0199] The respective intervals of the light emission periods TS, i.e., the delay amounts TDb1, TDb2, TDb3, and TDb4, are preferably selected randomly based on true random numbers or pseudo-random numbers. The order of the delay amounts TDb1, TDb2, TDb3, and TDb4 is also preferably selected randomly. These measures prevent an attacker from accurately synchronizing the timing of the attack light for close-range camouflage with the timing of the regular illumination light (self-emission), thereby effectively preventing close-range camouflage attacks.

[0200] Furthermore, when the order is random, it is preferable that the delay amounts (intervals) TDb1, TDb2, TDb3, and TDb4 do not overlap. That is, it is preferable that TDb1 ≠ TDb2 ≠ TDb3 ≠ TDb4. Furthermore, it is preferable to use a group of options having the above-mentioned first and second relationships when selecting the delay amounts (intervals) TDb1, TDb2, TDb3, and TDb4 so that the frequencies are concentrated at a specific peak.

[0201] The order of the delay amounts (offset times) TDa1, TDa2, TDa3, and TDa4 is preferably an almost unpredictable random order within the histogram generation period TM. However, if the delay amount specifying unit 222 randomly selects the order of the delay amounts TDb1 to TDb4, the same algorithm can be applied if the order of the delay amounts TDa1 to TDa4 is also randomly selected, thereby improving efficiency. However, the delay amounts (offset times) TDa1, TDa2, TDa3, and TDa4 may also be randomly selected based on true random numbers or pseudo-random numbers.

[0202] The delay amounts (offset times) TDa1 to TDa4 may be selected based on a fixed pattern within the histogram generation period TM. This fixed pattern may be, for example, a monotonically increasing pattern, a monotonically decreasing pattern, or a combination thereof. The fixed pattern may be the same for each histogram generation period TM, but from the perspective of preventing close-range spoofing attacks, it is preferable that the fixed pattern be different for each histogram generation period TM. When a different pattern is used for each histogram generation period TM, the fixed pattern may be a variable pattern randomly selected from a plurality of fixed patterns prepared in advance for each histogram generation period TM.

[0203] The delay amounts (offset times) TDa1 to TDa4 may not be provided. In other words, the timing of the first light emission may be the same as the start timing of the light emission period TS. However, if the light emission period TS is periodic, the first light emission timing signal becomes a periodic signal, which makes close-range spoofing attacks easier.

[0204] In addition, in FIGS. 33 and 34, the order of the delay amounts (intervals) TDb1, TDb2, TDb3, and TDb4 within the histogram generation period TM does not change within that period, but this is not limiting.

[0205] For example, as illustrated in Figures 35 and 36, the order of intervals within the histogram generation period TM may include multiple patterns of order. In the examples of Figures 35 and 36, the histogram generation period TM1 includes light emission periods TS1 to TS8, and the respective delay amounts are TDa1 to TDa8 and TDb1 to TDb8.

[0206] For example, in FIG. 35, the ratio of delay amounts (intervals) TDb1, TDb2, TDb3, and TDb4 is 4:3:2:6, and in FIG. 36, the ratio of delay amounts (intervals) TDb5, TDb6, TDb7, and TDb8 is 3:2:6:4.

[0207] Furthermore, although not shown, multiple arrangement patterns may be repeated during the histogram generation period TM. Furthermore, although not shown, multiple light-emitting periods TS with the same delay amount TDb may be consecutive. In this case, for example, the interval between light-emitting periods TS1 is set to TDb1, the interval between light-emitting periods TS2 is set to TDb1, the interval between light-emitting periods TS3 is set to TDb2, and the interval between light-emitting periods TS4 is set to TDb2.

[0208] Furthermore, in the case of multiple sequence patterns or repeated sequence patterns, at least some of them may be nested. For example, it is not necessary for a first sequence pattern to be followed by a second sequence pattern, and at least some of the second sequence pattern may be inserted in the middle of the first sequence pattern.

[0209] As shown in FIG. 37, the light emitting unit 110 may generate three or more light emitting timing signals within the light emitting period TS.

[0210] The delay amount specifying unit 222 may select the delay amounts (offset times) TDa1 to TDan for the light emission periods TS1 to TSn from a general group of options including n options, where n is a natural number, each of which is a natural number from 1 to n multiplied by A. Here, it is preferable that the real number A is as small as possible. This is because the smaller the real number A, the narrower the distance range in which close-distance camouflage is possible.

[0211] On the other hand, there are constraints on the intervals between burst emissions such as TDb and TDc. For example, if the light-emitting unit 110 is a laser resonator, there is a pause time for resonance, and if the light-receiving unit 210 includes a SPAD, there is a pause time during which light cannot be received continuously. For this reason, it is preferable that the minimum value of the option group for delay amounts TDa1 to TDan is smaller than the minimum value of the option group for delay amounts TDb1 to TDbn. It is also preferable that the minimum value of the option group for delay amounts TDa1 to TDan is smaller than the minimum value of the option group for delay amounts TDc1 to TDcn.

[0212] The delay amount specifying unit 222 can set the intervals between burst emissions, such as the delay amounts TDb1 to TDbn and the delay amounts TDc1 to TDcn, based on a random number or a fixed pattern, or can set the intervals based on a predetermined code. For example, the delay amount specifying unit 222 encodes data using a predetermined encoding method and sets the delay amount based on the generated code. The ToF sensor 200 can decode the code corresponding to the delay amount.

[0213] Incidentally, during the light emission period TS, the ToF sensor 200 can calculate multiple distances as unit distances based on the light reception timing and use them to generate an intermediate histogram. In this case, the ToF sensor 200 generates a final histogram from the intermediate histogram during the histogram generation period TM and calculates final distance data. A period during which distance data is calculated once may also be a frame period. As described above, each element of a set within a frame period is a histogram generation period, and each element of a set within a histogram generation period is a light emission period. However, this relationship is not limited to this. For example, a subset of a set within a frame period may be a histogram generation period, and a subset of a set within a histogram generation period may be a light emission period. Alternatively, a proper subset of a set within a frame period may be a histogram generation period, and a proper subset of a set within a histogram generation period may be a light emission period.

[0214] As described above, the light-emitting period TS may be periodic or aperiodic. When the light-emitting period TS is aperiodic, the length of the TS is selected randomly. Alternatively, the order of the TS is selected randomly. Alternatively, the TS is selected based on a variable or fixed pattern. When the light-emitting period TS is aperiodic, the delay amount specifying unit 222 may not set the delay amount TDa. When the light-emitting period TS is periodic, the light-emitting period TS needs to be lengthened in consideration of the maximum value of the delay amount TDa. However, when the light-emitting period TS is aperiodic, the maximum value of the delay amount TDa does not need to be considered, and therefore the length of the light-emitting period TS can be minimized. This reduces the time required to calculate distance data.

[0215] Incidentally, the histogram generator 330 can generate a final histogram using one intermediate histogram within the histogram generation period TM, and the lengths of the light emission period TS and the histogram generation period TM can be the same. In this case, the interval (e.g., TDc) between the most recent light emission and the immediately preceding light emission in the light emission period TS is set to a fixed value that does not change for each light emission period. In this case, it is preferable to set the interval (e.g., TDb) between the most recent light emission and the immediately following light emission in the light emission period TS to a variable value greater than the fixed value.

[0216] However, some light emission intervals (such as TDb) in the light emission period TS may be set to fixed values ​​that do not change for each light emission period TS, and other light emission intervals (such as TDc) may be set to variable values ​​that are larger than the fixed values. The fixed values ​​are preferably values ​​that exceed the pause time and are preferably as small as possible.

[0217] If the histogram generation unit 330 generates a final histogram using one intermediate histogram within the histogram generation period TM, the risk of a short-distance or long-distance spoofing attack may increase. However, the distance range in which distance spoofing is possible can be limited to a range corresponding to a fixed value. In other words, distance spoofing attacks become more difficult. For example, for a general option group such as "A×1, A×2, A×3, A×4...", TDc may be set to A×1, and TDb may be selected from a predetermined option group of "A×2, A×3, A×4..." excluding "A×1".

[0218] In the second embodiment, the light emission timing signal was generated primarily to prevent at least one of optical interference due to other light emissions and close-range camouflage attacks. However, the histogram generation unit 330 does not re-accumulate the light so that the multiple peaks of the self-emission light coincide with each other. On the other hand, in the third and fourth embodiments, the histogram generation unit 330 re-accumulates the light so that the multiple peaks of the self-emission light coincide with each other, thereby increasing the frequency of the histogram and improving noise resistance. Therefore, in addition to preventing at least one of interference due to other light emissions and close-range camouflage attacks, the third and fourth embodiments enable more accurate or longer-distance distance measurement than the second embodiment.

[0219] Incidentally, in the fourth embodiment, it is possible to switch between at least a part of the first method of the second embodiment and at least a part of the second method of the third or fourth embodiment.

[0220] 38 , after step S903, the histogram generator 330 determines whether to use the first method (step S950). If the first method is to be used (step S950: Yes), the histogram generator 330 performs the histogram generation process (step S904) using the first method. If the first method is not to be used (step S950: No), the histogram generator 330 performs the histogram generation process (step S910) using the second method.

[0221] The ToF sensor 200 can select and switch between outputting the intermediate histogram as is as intermediate data, or outputting the result of re-accumulating the intermediate histogram as intermediate data.

[0222] The detecting unit 340 performs a process of prioritizing an earlier peak among peaks that satisfy a predetermined condition, but can also switch to another process. For example, the detecting unit 340 can switch between at least one of a process of detecting the peak with the highest frequency among peaks that satisfy a predetermined condition and a process of prioritizing a later peak among peaks that satisfy a predetermined condition, and a process of prioritizing an earlier peak among peaks that satisfy a predetermined condition.

[0223] Thus, according to the fourth embodiment of the present technology, the delay amount indication unit 222 randomly selects the delay amounts TDb1, TDb2, TDb3, and TDb4, and randomly selects their order, thereby preventing close-range spoofing attacks.

[0224] 5. Fifth Embodiment In the first embodiment described above, the distance data is calculated by the distance calculation unit 300 subsequent to the ToF sensor 200, but this is not limiting. The distance measuring device 100 in this fifth embodiment differs from the first embodiment in that the ToF sensor 200 calculates the distance data.

[0225] 39 is a block diagram showing an example configuration of a light-emitting unit 110 according to a fifth embodiment of the present technology. The light-emitting unit 110 according to the fifth embodiment differs from the light-emitting unit 110 according to the first embodiment in that it further includes a light-emission instruction unit 114 and a delay amount instruction unit 115.

[0226] The configurations of the light emission instruction section 114 and the delay amount instruction section 115 are similar to those of the light emission instruction section 221 and the delay amount instruction section 222 described above in the first embodiment.

[0227] 40 is a block diagram showing an example configuration of a ToF sensor 200 according to a modification of the fifth embodiment of the present technology. In the ToF sensor 200 according to the fifth embodiment, the light emission instruction unit 221 and the delay amount instruction unit 222 are eliminated. The ToF sensor 200 further includes an intermediate data calculation unit 224, a histogram generation unit 225, a detection unit 226, a distance data calculation unit 227, and a protection unit 228.

[0228] The configurations of the intermediate data calculation unit 224, histogram generation unit 225, detection unit 226, and distance data calculation unit 227 are similar to those of the intermediate data calculation unit 320, histogram generation unit 330, detection unit 340, and distance data calculation unit 350 described above.

[0229] The protection unit 228 performs processing to protect the calculated distance data. For example, the protection unit 228 may perform various processing using a CRC (Cyclic Redundancy Check) value, a MAC (Media Access Control) value, or the like to ensure integrity. Alternatively, the protection unit 228 may perform processing to encrypt the distance data as transmission data using some kind of encryption technology to ensure confidentiality. The protection unit 228 is provided as needed.

[0230] The intermediate data calculation unit 224 can also calculate one or more unit distances and use them to generate an intermediate histogram.

[0231] As shown in the figure, the processing up to the calculation of distance data is performed within the ToF sensor 200, thereby making it possible to sufficiently protect privacy regarding the measurement data.

[0232] The second and third embodiments and the first and third modifications of the third embodiment can be applied to the fifth embodiment.

[0233] As described above, according to the fifth embodiment of the present technology, the ToF sensor 200 calculates the distance data, so that privacy regarding the measurement data can be sufficiently protected.

[0234] 6. Application Examples to Mobile Bodies The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0235] FIG. 41 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0236] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 41 , the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (Interface) 12053.

[0237] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0238] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0239] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0240] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0241] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0242] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0243] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0244] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0245] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying information to vehicle occupants or the outside of the vehicle. In the example of Fig. 41, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0246] FIG. 42 is a diagram showing an example of the installation position of the imaging unit 12031.

[0247] In FIG. 42, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0248] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0249] 42 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0250] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0251] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which runs autonomously without relying on driver operation.

[0252] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0253] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0254] An example of a vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to, for example, the image capturing unit 12101 of the above-described configuration. Specifically, the ToF sensor 200 in FIG. 1 can be applied to the image capturing unit 12101. Applying the technology according to the present disclosure to the image capturing unit 12101 can prevent distance spoofing attacks, thereby improving the security of the vehicle control system.

[0255] The effects described in this specification are merely examples and are not limiting, and other effects may also be present.

[0256] Furthermore, the above-described examples may be combined in any manner, and even when various combinations are used, the various effects described above can be obtained.

[0257] The timing and position of each element shown in the block diagrams and flowcharts in each figure are merely examples, and at least some of the elements may be configured differently. Various modifications are possible to the embodiments described in each example. That is, some of the components of each example may be the same, some may be integrated, some may be integrated, or some may be separate. Furthermore, some of the components of each example may be omitted, some or all may be changed, or some or all may be modified. Furthermore, some of the components of each example may be replaced with other components, or other components may be added to some or all of the components. Furthermore, some or all of the components of each example may be divided into multiple components, some or all may be separated into multiple components, or at least some of the divided or separated components may have different functions and / or features.

[0258] Furthermore, different embodiments may be implemented by moving at least some of the components. Furthermore, different embodiments may be implemented by adding at least one of a coupling element and a relay element to a combination of at least some of the components. Furthermore, different embodiments may be implemented by adding at least one of a switching function and a selection function to a combination of at least some of the components.

[0259] In this specification, the processing performed by a computer according to a program does not necessarily have to be performed in chronological order according to the order described in the flowchart. In other words, the processing performed by a computer according to a program also includes processing that is executed in parallel or individually (for example, parallel processing or processing by objects).

[0260] The program may be processed by a single computer (processor), or may be distributed among multiple computers. Furthermore, the program may be transferred to a remote computer for execution.

[0261] Furthermore, in this specification, a system refers to a collection of multiple components (devices, modules (components), etc.), regardless of whether all of the components are contained in the same housing. Therefore, multiple devices housed in separate housings and connected via a network, and a single device housed in a single housing with multiple modules, are both systems.

[0262] Also, for example, a configuration described as one device (or processing unit) may be divided and configured as multiple devices (or processing units). Conversely, configurations described above as multiple devices (or processing units) may be combined and configured as one device (or processing unit). Of course, configurations other than those described above may be added to the configuration of each device (or each processing unit). Furthermore, as long as the configuration and operation of the entire system are substantially the same, part of the configuration of one device (or processing unit) may be included in the configuration of another device (or other processing unit).

[0263] Furthermore, for example, the present technology can be configured as a cloud computing system in which a single function is shared and processed collaboratively by multiple devices via a network.

[0264] Furthermore, for example, the above-described program can be executed in any device, as long as the device has the necessary functions (functional blocks, etc.) and can obtain the necessary information.

[0265] Also, for example, each step described in the above flowchart can be executed by one device or can be shared and executed by multiple devices. Furthermore, if one step includes multiple processes, the multiple processes included in that one step can be executed by one device or can be shared and executed by multiple devices. In other words, multiple processes included in one step can be executed as multiple step processes. Conversely, processes described as multiple steps can be executed collectively as a single step.

[0266] In addition, the processing of the steps of a program executed by a computer may be executed in chronological order according to the order described in this specification, or may be executed in parallel or individually at the required timing, such as when a call is made. In other words, as long as no contradiction occurs, the processing of each step may be executed in an order different from the order described above. Furthermore, the processing of the steps of this program may be executed in parallel with the processing of another program, or may be executed in combination with the processing of another program.

[0267] It should be noted that the present technologies described in this specification can be implemented independently and singly, unless a contradiction arises. Of course, any two or more of the present technologies can also be implemented in combination. For example, part or all of the present technologies described in any embodiment can be implemented in combination with part or all of the present technologies described in other embodiments. Furthermore, part or all of any of the present technologies described above can also be implemented in combination with other technologies not described above.

[0268] The present technology may also be configured as follows: (1) A distance measuring device including: a light emitting unit that emits a predetermined number of beams of irradiation light; a light receiving unit that receives reflected light of the irradiation light; a histogram generating unit that generates a histogram by integrating the number of times the light receiving unit receives light for each time within an accumulation period; a detecting unit that, when the histogram includes multiple peaks that satisfy a predetermined condition, detects, from among the multiple peaks, a peak that is closest to a start time of the accumulation period; and a distance calculating unit that calculates distance information based on the time corresponding to the detected peak. (2) The distance measuring device according to (1), wherein the predetermined number of irradiation lights include first and second irradiation lights, the light emitting unit emits light at first and second light emission timings within each of a single or multiple light emission periods to irradiate the first and second irradiation lights, the first light emission timing is delayed by an offset time with respect to the start timing of each of the single or multiple light emission periods, and the interval between the first and second light emission timings within each of the single or multiple light emission periods is an interval randomly selected from a predetermined group of options. (3) The distance measuring device according to (2), wherein the offset time is selected randomly from a predetermined group of options. (4) The distance measuring device according to (2) or (3), wherein the order of the offset times for each of the single or multiple light emission periods is selected randomly. (5) The distance measuring device according to (2), wherein the offset time for each of the single or multiple light emission periods is selected based on a predetermined fixed pattern. (6) The distance measuring device described in (1), wherein the predetermined number of irradiation lights include first, second, and third irradiation lights, the light emitting unit emits light at first, second, and third light emission timings within each of a single or multiple light emission periods to irradiate the first, second, and third irradiation lights, a first interval between the first and second light emission timings and a second interval between the second and third light emission timings are different values, and the order of the first intervals and the second intervals within each of the single or multiple light emission periods is selected randomly.(7) The distance measuring device according to (6), wherein the first interval and the second interval are selected from a group of options including K options each obtained by multiplying a predetermined real number by K consecutive natural numbers from 1 to L, where K is a natural number smaller than L, with some of the consecutive natural numbers omitted. (8) The distance measuring device according to (7), wherein the group of options includes a plurality of options arranged in ascending order, and a focused option among the plurality of options has a value smaller than the focused option and different from a sum of two or more consecutive options. (9) The distance measuring device according to (1), wherein the predetermined number of irradiation lights include first, second, and third irradiation lights, and the light-emitting unit emits light at first, second, and third light-emitting timings within each of a single or multiple light-emitting periods to irradiate the first, second, and third irradiation lights, and one of the first interval between the first and second light-emitting timings and the second interval between the second and third light-emitting timings is a predetermined fixed value, and the other is a variable value longer than the fixed value. (10) The distance measuring device according to (1), wherein the predetermined number of irradiation lights include first, second, third, and fourth irradiation lights; a histogram generation period during which the histogram is generated includes first and second light emission periods; the light emitting unit emits light at first and second light emission timings within the first light emission period to irradiate the first and second irradiation lights, and emits light at third and fourth light emission timings within the second light emission period to irradiate the third and fourth irradiation lights; a first interval between the first and second light emission timings has a value different from a second interval between the third and fourth light emission timings; the first light emission timing is delayed by a first offset time from the start timing of the first light emission period; and the third light emission timing is delayed by a second offset time from the start timing of the second light emission period; and the order of the first intervals and the second intervals is selected randomly. (11) The distance measuring device according to (10), wherein the first and second offset times are randomly selected from a predetermined group of options, and the first and second offset times are updated when the histogram generation period has elapsed.(12) The distance measuring device according to (10) or (11), wherein an order of the first and second offset times within the histogram generation period is selected randomly, and the order is updated when the histogram generation period has elapsed. (13) The distance measuring device according to (10), wherein the first and second offset times are selected based on a predetermined fixed pattern, and the fixed pattern is updated when the histogram generation period has elapsed. (14) The distance measuring device according to (1), wherein the predetermined number of irradiation lights include first and second irradiation lights, and the histogram generation period during which the histogram is generated includes one or more light emission periods, and the light emission unit emits light at first and second light emission timings within each of the single or multiple light emission periods to irradiate the first and second irradiation lights, and the histogram generation unit generates the histogram so that a first peak corresponding to the first irradiation light and a second peak corresponding to the second irradiation light coincide with each other. (15) The distance measuring device according to (14), wherein the accumulation period includes a first accumulation period whose start timing is the first light emission timing and a second accumulation period whose start timing is the second light emission timing, and the histogram generation unit generates a first histogram by integrating the number of times of light reception for each time during the first accumulation period and generates a second histogram by integrating the number of times of light reception for each time during the second accumulation period, and re-accumulates the second histogram in the first histogram. (16) The distance measuring device according to (14), wherein the histogram generation unit shifts the histogram according to the interval between the first and second light emission timings and re-accumulates the histogram before the shift. (17) The distance measuring device according to (14), wherein the histogram generation unit selects one of the elements in the histogram and re-accumulates an element that is earlier or later than the selected element by the interval between the first and second light emission timings in the selected element.(18) The distance measuring device according to (1), wherein the histogram generation unit switches between a first histogram generation method and a second histogram generation method, wherein the second histogram generation method is a histogram generation method that shifts the histogram and re-accumulates the histogram before the shift, or a histogram generation method that selects one of elements in the histogram and re-accumulates elements before or after the selected element in the selected element, and the first histogram generation method is a histogram generation method that does not require the re-accumulation process. (19) A light receiving device comprising: a histogram generation unit that generates a histogram by integrating the number of times a light receiving unit that receives reflected light of irradiated light for each time within an accumulation period, and a detection unit that, when the histogram includes multiple peaks that satisfy a predetermined condition, detects from the multiple peaks with priority a peak that is closest to a start time of the accumulation period. (20) A distance measurement method comprising: an emission step of irradiating a predetermined number of beams of irradiation light; a light receiving step of receiving reflected light from the irradiation light by a light receiving unit; a histogram generation step of generating a histogram by accumulating the number of times the light receiving unit receives light for each time within an accumulation period; a detection step of, if the histogram includes multiple peaks that satisfy predetermined conditions, preferentially detecting a peak from among the multiple peaks that is closest to the start time of the accumulation period; and a distance calculation step of calculating distance information based on the time corresponding to the detected peak.

[0269] 100 Distance measuring device 110 Light emitting unit 111 Light emitting timing signal generating unit 112 Driver 113 Light emitting element 114, 221 Light emitting instruction unit 115, 222 Delay amount instruction unit 200 ToF sensor 210 Light receiving unit 220 Time management unit 223, 310 Communication unit 224, 320 Intermediate data calculation unit 225, 330 Histogram generation unit 226, 340 Detection unit 227, 350 Distance data calculation unit 228 Protection unit 230 Counter unit 231 Counting control unit 232 Counter 233 Memory 300 Distance calculation unit 331 to 333 Storage unit 334 to 336 Accumulation processing unit 337 to 338 Re-accumulation processing unit 12101 Imaging unit

Claims

1. A distance measuring device comprising: an emitter that emits a predetermined number of beams of light; a receiver that receives reflected light from the emitted light; a histogram generator that generates a histogram by accumulating the number of times the receiver receives light for each time within an accumulation period; a detector that, if the histogram includes multiple peaks that satisfy predetermined conditions, detects, from among the multiple peaks, a peak that is closest to the start time of the accumulation period; and a distance calculator that calculates distance information based on the time corresponding to the detected peak.

2. A distance measuring device as described in claim 1, wherein the predetermined number of irradiation lights include first and second irradiation lights, the light emitting unit emits light at first and second light emission timings within each of a single or multiple light emission periods to irradiate the first and second irradiation lights, the first light emission timing is delayed by an offset time with respect to the start timing of each of the single or multiple light emission periods, and the interval between the first and second light emission timings within each of the single or multiple light emission periods is an interval randomly selected from a predetermined group of options.

3. The distance measuring device according to claim 2, wherein the offset time is selected randomly from a predetermined group of options.

4. The distance measuring device according to claim 2, wherein the order of the offset times for each of the single or multiple light emission periods is selected randomly.

5. The distance measuring device according to claim 2, wherein the offset time for each of the single or multiple light emission periods is selected based on a predetermined fixed pattern.

6. A distance measuring device according to claim 1, wherein the predetermined number of irradiation lights include first, second and third irradiation lights, the light emitting unit emits light at first, second and third light emission timings within each of a single or multiple light emission periods to irradiate the first, second and third irradiation lights, a first interval between the first and second light emission timings and a second interval between the second and third light emission timings are different values, and the order of the first intervals and the second intervals within each of the single or multiple light emission periods is selected randomly.

7. A distance measuring device according to claim 6, wherein the first interval and the second interval are selected from a group of options including K options obtained by multiplying each of K consecutive natural numbers from 1 to L, omitting some of the natural numbers, where K is a natural number smaller than L, by a predetermined real number.

8. The distance measuring device according to claim 7, wherein the group of options includes a plurality of options arranged in ascending order, and a selected option among the plurality of options has a value smaller than the selected option and different from the sum of two or more consecutive options.

9. A distance measuring device as claimed in claim 1, wherein the predetermined number of irradiation lights include first, second and third irradiation lights, the light emitting unit emits light at first, second and third light emission timings within each of a single or multiple light emission periods to irradiate the first, second and third irradiation lights, and one of a first interval between the first and second light emission timings and a second interval between the second and third light emission timings is a predetermined fixed value, and the other is a variable value longer than the fixed value.

10. A distance measuring device as described in claim 1, wherein the predetermined number of irradiation lights include first, second, third and fourth irradiation lights; a histogram generation period during which the histogram is generated includes first and second light emission periods; the light emitting unit emits light at first and second light emission timings within the first light emission period to irradiate the first and second irradiation lights, and emits light at third and fourth light emission timings within the second light emission period to irradiate the third and fourth irradiation lights; a first interval between the first and second light emission timings has a different value from a second interval between the third and fourth light emission timings; the first light emission timing is delayed by a first offset time from the start timing of the first light emission period; and the third light emission timing is delayed by a second offset time from the start timing of the second light emission period; and the order of the first intervals and the second intervals is selected randomly.

11. The distance measuring device according to claim 10, wherein the first and second offset times are randomly selected from a predetermined group of options, and the first and second offset times are updated when the histogram generation period has elapsed.

12. The distance measuring device according to claim 10, wherein the order of the first and second offset times within the histogram generation period is selected randomly, and the order is updated when the histogram generation period has elapsed.

13. The distance measuring device according to claim 10, wherein the first and second offset times are selected based on a predetermined fixed pattern, and the fixed pattern is updated when the histogram generation period has elapsed.

14. A distance measuring device as described in claim 1, wherein the predetermined number of illumination lights include first and second illumination lights, the histogram generation period during which the histogram is generated includes a single or multiple light emission periods, the light emitting unit emits light at first and second light emission timings within each of the single or multiple light emission periods to irradiate the first and second illumination lights, and the histogram generation unit generates a histogram so that a first peak corresponding to the first illumination light and a second peak corresponding to the second illumination light coincide with each other.

15. A distance measuring device as described in claim 14, wherein the accumulation period includes a first accumulation period whose start timing is the first light emission timing and a second accumulation period whose start timing is the second light emission timing, and the histogram generation unit generates a first histogram by integrating the number of times of light reception for each time within the first accumulation period, and generates a second histogram by integrating the number of times of light reception for each time within the second accumulation period, and re-accumulates the second histogram in the first histogram.

16. The distance measuring device according to claim 14, wherein the histogram generating section shifts the histogram in accordance with the interval between the first and second light emission timings and stores the data back into the histogram before the shift.

17. A distance measuring device according to claim 14, wherein the histogram generating unit selects one of the elements in the histogram and re-stores, in the selected element, an element that is located before or after the selected element by the interval of the first and second light emission timings.

18. The distance measuring device of claim 1, wherein the histogram generation unit switches between a first histogram generation method and a second histogram generation method, the second histogram generation method being a histogram generation method that shifts the histogram and re-accumulates the histogram before the shift, or a histogram generation method that selects one of the elements in the histogram and re-accumulates an element before or after the selected element in the selected element, and the first histogram generation method being a histogram generation method that does not require the re-accumulation process.

19. A light receiving device comprising: a histogram generating unit that generates a histogram by accumulating the number of times a light receiving unit that receives reflected light from irradiated light for each time during an accumulation period; and a detecting unit that, when the histogram includes multiple peaks that satisfy predetermined conditions, detects, from among the multiple peaks, a peak that is closest to the start time of the accumulation period.

20. A distance measurement method comprising: an emission step of emitting a predetermined number of beams of radiation; a light receiving step of receiving reflected light from the radiation beam by a light receiving unit; a histogram generation step of integrating the number of times the light receiving unit receives the beam for each time within an accumulation period to generate a histogram; a detection step of, if the histogram includes multiple peaks that satisfy predetermined conditions, detecting, from among the multiple peaks, a peak that is closest to the start time of the accumulation period; and a distance calculation step of calculating distance information based on the time corresponding to the detected peak.

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