JP2020112528A - Optical ranging device and method for controlling the same - Google Patents

Abstract

To provide a technique enabling a failure of a light receiving element to be detected by a simple method.SOLUTION: An optical ranging device 10 comprises: an irradiation unit 20 irradiating space with light by driving a light source 21; a light receiving unit 30 having a light receiving element 311 detecting reflection light from an object in the space; an intensity signal output unit 41 outputting an intensity signal which indicates the intensity of the reflection light detected by the light receiving element; a measurement unit 40 detecting a peak signal from the intensity signal successively output from the intensity signal output unit and measuring distance to the object according to time from light irradiation by the irradiation unit to detection of the peak signal; and a failure detection unit 60 detecting a failure of the light receiving element by comparing the intensity signal with a reference value.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an optical distance measuring device and a control method thereof.

Regarding the optical distance measuring device, for example, Patent Document 1 discloses a device that employs a SPAD (single photon avalanche photodiode) as a light receiving element. In this device, a histogram is generated based on the intensity of the reflected light detected by the SPAD array, the flight time (ToF: Time of Flight) of the light is obtained from the peak position of the histogram, and the measurement object is calculated based on the flight time. Calculate the distance to.

JP, 2008-91760, A JP, 2016-176750, A Japanese Patent No. 5644294

When a failure occurs in the light receiving element due to deterioration over time, the signal intensity of the reflected light to be detected becomes inaccurate. For example, if the light receiving element fails and its output is fixed at the minimum level (for example, zero), the signal intensity of the detected reflected light is detected even though the reflected light of sufficient intensity is received. May be low. Further, when a failure occurs in the light receiving element and the output is fixed to the maximum level (for example, 1), the detected reflected light signal intensity is low even though the weak reflected light is received. It can be high. Therefore, there is a demand for a technique capable of detecting a failure of the light receiving element by a simple method.

The present disclosure can be realized as the following modes.

According to an aspect of the present disclosure, an optical distance measuring device (10) is provided. This optical distance measuring device includes a light emitting unit (20) for driving a light source (21) to emit light into the space, and a light receiving element (311) for detecting reflected light from an object in the space. A peak signal from the intensity signal output unit (41) that outputs an intensity signal representing the intensity of the reflected light detected by the light receiving element, and the intensity signal that is sequentially output from the intensity signal output unit. Comparing the intensity signal and a reference value with a measuring unit (40) that detects and measures the distance to the object according to the time from the irradiation of light by the irradiation unit to the detection of the peak signal. A failure detection unit (60) for detecting a failure of the light receiving element.

According to the optical distance measuring apparatus of this aspect, the failure of the light receiving element can be detected by a simple method by comparing the intensity signal of the reflected light with the reference value.

The present disclosure can be realized in various forms other than the optical distance measuring device. For example, it can be realized in the form of a control method of the optical distance measuring device, a vehicle equipped with the optical distance measuring device, or the like.

The figure which shows schematic structure of an optical ranging device. The figure which shows the structure of an optical distance measuring device. The figure which shows the structure of a light-receiving surface. The figure which shows an example of a histogram. The figure explaining the 1st function with which a failure detection part is equipped. The figure explaining the 2nd function with which a failure detection part is equipped. The flowchart which shows the control method of an optical ranging device. The figure which shows the signal level of the histogram in a dark environment. The figure which shows the signal level of the histogram in a bright environment. The figure which shows a light-shielding mechanism. The figure which shows the state shielded by the light-shielding mechanism. FIG. 6 is a first diagram showing a method of determining a failure using intensity signals of adjacent pixels. The 2nd figure showing the method of judging a failure using the intensity signal of an adjacent pixel.

A. First embodiment:
As shown in FIG. 1, an optical distance measuring apparatus 10 according to the first embodiment of the present disclosure includes a housing 15, an irradiation unit 20, a light receiving unit 30, and a measuring unit 40. The irradiation unit 20 emits the irradiation light IL to a predetermined measurement range MR in space. In the present embodiment, the irradiation unit 20 scans the irradiation light IL in the scanning direction SD. The irradiation light IL is formed in a rectangular shape whose longitudinal direction is the direction orthogonal to the scanning direction SD. The light receiving unit 30 receives the reflected light from a range including the measurement range MR corresponding to the irradiation of the irradiation light IL. The measuring unit 40 measures the distance to the object existing within the measurement range MR according to the intensity of the reflected light received by the light receiving unit 30. The optical distance measuring device 10 is mounted on a vehicle, for example, and is used for detecting an obstacle and measuring a distance to the obstacle. Hereinafter, a time unit in which the measurement range MR is entirely scanned by the irradiation light IL is referred to as a frame.

FIG. 2 shows a more specific configuration of the optical distance measuring device 10. As shown in FIG. 2, the optical distance measuring device 10 includes a control unit 50 in addition to the irradiation unit 20, the light receiving unit 30, and the measurement unit 40 shown in FIG. The control unit 50 is configured as a computer including a CPU and a memory, and controls the irradiation unit 20, the light receiving unit 30, and the measurement unit 40. The control unit 50 of this embodiment includes a failure detection unit 60.

The irradiation unit 20 drives the light source 21 to irradiate the space with light. The light source 21 is composed of a semiconductor laser diode and emits pulsed laser light as irradiation light. The irradiation light emitted from the light source 21 is formed into the vertically long irradiation light IL shown in FIG. 1 by an optical system (not shown). The irradiation unit 20 includes a scanning unit 22. The scanning unit 22 rotates the mirror 222 around the rotation shaft 221 to perform one-dimensional scanning of the irradiation light IL over the measurement range MR. The mirror 222 is, for example, a MEMS mirror. The rotation of the mirror 222 is controlled by the control unit 50. In this embodiment, the semiconductor laser is used as the light source 21 of the irradiation unit 20, but other light sources such as a solid-state laser may be used.

The irradiation light emitted by the irradiation unit 20 is reflected by the object OB within the measurement range MR. The reflected light reflected by the object OB is received by the light receiving unit 30.

As shown in FIGS. 2 and 3, the light receiving unit 30 includes a plurality of pixels 31 arranged in a two-dimensional array on the light receiving surface 32 irradiated with the reflected light from the object. As shown in FIG. 3, each pixel 31 has a plurality of light receiving elements 311 for detecting the reflected light from the object OB. In the present embodiment, each pixel 31 includes a SPAD (single photon avalanche diode) as the light receiving element 311. In the present embodiment, each pixel 31 has a total of 45 light receiving elements 311 which are 9 in the horizontal direction and 5 in the vertical direction. The light receiving surface 32 of the light receiving unit 30 is configured by, for example, 64 pixels 31 arranged in the vertical direction and 256 pixels arranged in the horizontal direction. When receiving light (photons), the SPAD as the light receiving element 311 outputs a pulsed signal indicating the incidence of light with a certain probability. That is, each SPAD outputs a signal of 0 (low level) or 1 (high level) as an output level. In the present embodiment, since each pixel 31 includes 45 SPADs, each pixel 31 outputs 0 to 45 pulse signals according to the intensity of the received light.

An intensity signal output unit 41 is connected to the light receiving unit 30. The intensity signal output unit 41 is a circuit that outputs an intensity signal indicating the intensity of the reflected light detected by the light receiving element 311. The intensity signal output unit 41 adds the number of pulse signals output from the plurality of light receiving elements 311 included in each pixel 31 substantially simultaneously for each pixel. Then, the added value is output as an intensity signal indicating the intensity of the reflected light received by each pixel 31. In the present embodiment, as described above, each pixel includes 45 light receiving elements 311. Therefore, the intensity signal output unit 41 outputs an intensity signal having a value of 0 to 45 for each pixel 31. ..

The measuring unit 40 detects the peak signal from the intensity signals sequentially output from the intensity signal output unit 41, and measures the distance to the object according to the time from the irradiation of light by the irradiation unit 20 to the detection of the peak signal. It has a function to do. The measurement unit 40 includes a histogram generation unit 42, a signal processing unit 43, and a distance calculation unit 44 in order to realize this function. These are configured as, for example, one or two or more integrated circuits. Note that these may be functional units realized by software by the CPU executing the program.

The histogram generation unit 42 is a circuit that generates a histogram for each pixel 31 based on the intensity signal output from the intensity signal output unit 41. FIG. 4 shows an example of the histogram. The class (horizontal axis) of the histogram indicates the flight time of light from the irradiation of the irradiation light IL from the irradiation unit 20 to the reception of the reflected light by the pixel 31. Hereinafter, this time is referred to as TOF (TOF: Time Of Flight). On the other hand, the frequency (vertical axis) of the histogram is the value of the intensity signal output from the intensity signal output unit 41, and represents the intensity of the light reflected from the object. The histogram generation unit 42 generates a histogram by recording the intensity signal output from the intensity signal output unit 41 for each TOF. When an object exists in the measurement range MR, light is reflected from the object, and an intensity signal is recorded in the TOF class according to the distance to the object.

The signal processing unit 43 is a circuit that detects, as a peak signal, the part of the class having the highest frequency in the histogram. The frequency in the peak signal is hereinafter referred to as a peak value. The peak signal in the histogram indicates that the object exists at the position (distance) corresponding to the TOF corresponding to the peak signal. The signals other than the peak signal are signals due to the influence of ambient light or the output from the defective light receiving element 311. The signal processing unit 43 may detect, as a peak signal, a portion of the class of the frequency equal to or higher than a predetermined threshold.

The distance calculation unit 44 is a circuit that calculates the distance value D from the TOF corresponding to the peak signal detected by the signal processing unit 43. When the TOF corresponding to the peak signal is “Δt”, the speed of light is “c”, and the distance value is “D”, the distance calculation unit 44 calculates the distance value D by the following equation (1). The distance calculation unit 44 calculates the distance value D for all histograms, that is, for all pixels 31.
D=(c×Δt)/2 (1)

The distance value D of each pixel 31 measured by the measurement unit 40 is output from the optical distance measuring device 10 to the ECU or the like of the vehicle in frame units. The ECU of the vehicle can detect the obstacle in the measurement range MR and measure the distance to the obstacle by using the distance value for each pixel 31 acquired from the optical distance measuring device 10.

The failure detection unit 60 detects the failure of the light receiving element 311 in each pixel 31 by comparing the value of the intensity signal output from the intensity signal output unit 41 with the reference value for each pixel 31. In the present embodiment, the failure detection unit 60 is realized by the CPU included in the control unit 50 executing a predetermined program stored in the memory. The failure detection unit 60 may be realized by a circuit.

The failure detection unit 60 of the present embodiment acquires, for each pixel 31, the maximum value (that is, the peak value) of the intensity signal output from the intensity signal output unit 41 a plurality of times over a plurality of frames and a plurality of times. When the maximum value thereof does not exceed the predetermined first reference value (see FIG. 4), it is determined that there is the light receiving element 311 whose output level is fixed to the minimum level. Hereinafter, this function is referred to as a first function. The number of times the maximum value of the intensity signal is acquired is arbitrary, and is, for example, the number of times acquired during the period from daytime to nighttime (12 to 24 hours). The first reference value is, for example, a theoretical maximum value of the intensity signal that is preset in consideration of the output error and the output variation of the pixel 31.

In addition, the failure detection unit 60 of the present embodiment acquires, for each pixel 31, the minimum value of the intensity signal output from the intensity signal output unit 41 a plurality of times over a plurality of frames, and acquires the minimum value of those obtained a plurality of times. It has a function of determining that there is a light receiving element 311 whose output level is fixed to the maximum level when the value does not fall below a predetermined second reference value. Hereinafter, this function is referred to as a second function. The number of times the minimum value of the intensity signal is acquired is arbitrary, and is, for example, the number of times acquired during the period from daytime to nighttime (12 to 24 hours). The second reference value is, for example, a theoretical minimum value of the intensity signal that is preset in consideration of the output error and the output variation of the pixel 31.

The failure detection unit 60 of the present embodiment has both the above-described first function and second function, but the failure detection unit 60 may have only one of these.

The above-mentioned first function will be described with reference to FIG. The failure detection unit 60 receives the maximum value x (peak value x) of the intensity signal from the intensity signal output unit 41 a plurality of times, and one or more of the received intensity signals have a first reference value or more. In case of, the failure detection unit 60 can determine that the pixel 31 is normal. On the other hand, when all of the received plurality of intensity signals do not exceed the first reference value, the failure detection unit 60 includes the light receiving element 311 whose output is fixed to 0 in the pixel 31, and thus the failure occurs. Is determined to have occurred.

The failure detection unit 60 of this embodiment has a function of estimating the number of failed light receiving elements 311 based on the difference between the maximum value of the intensity signal and the first reference value. The value of the intensity signal output from the intensity signal output unit 41 for each pixel 31 is the number of the light receiving elements 311 whose outputs become 1 at the same time among the light receiving elements 311 included in each pixel 31. Therefore, for example, when the first reference value is 45, the failure detection unit 60 determines that the output of the five light receiving elements 311 is 0 if the maximum value of the maximum values of the intensity signals received a plurality of times is 40. It is presumed that it is stuck to and is out of order.

The intensity signal output unit 41 of the present embodiment has a function of correcting the intensity signal in accordance with the number of defective light receiving elements 311 estimated by the failure detection unit 60. Specifically, assuming that the number of light-receiving elements included in the pixel 31 is N and the number of light-receiving elements 311 that have failed is M, a gain G is calculated by the following equation (2), and the gain G is obtained. The intensity signal is corrected by multiplying it by the value of the intensity signal. The histogram generation unit 42 generates a histogram using the intensity signal corrected in this way. The intensity signal output unit 41 recalculates the gain G every time the number of failures of the light receiving element 311 estimated by the failure detection unit 60 changes. The calculation of the gain G may be performed by the failure detection unit 60 instead of the intensity signal output unit 41.

G=N/(NM)... (2)

Subsequently, the second function described above will be described with reference to FIG. The failure detection unit 60 receives the minimum value y of the intensity signal from the intensity signal output unit 41 a plurality of times, and at least one of the received intensity signals has a second reference value (see FIG. 4) or less, The failure detection unit 60 can determine that the pixel 31 is normal. On the other hand, when all of the received plurality of received intensities do not fall below the second reference value, the failure detection unit 60 includes the light receiving element 311 whose output is fixed at 1 in the pixel 31, and the failure is detected. Judge that it is occurring.

The failure detection unit 60 of this embodiment has a function of estimating the number of failed light receiving elements 311 based on the difference between the minimum value of the intensity signal and the second reference value. The value of the intensity signal output from the intensity signal output unit 41 for each pixel 31 is the number of the light receiving elements 311 whose outputs become 1 at the same time among the light receiving elements 311 included in each pixel 31. Therefore, for example, when the second reference value is 0, the failure detection unit 60 determines that the output of the five light receiving elements 311 is 1 if the smallest value among the minimum values of the intensity signals received a plurality of times is 5. It is presumed that it is stuck to and is out of order. Even when the light receiving element 311 whose output is fixed to 1 is detected, the intensity signal output unit 41 calculates the gain G according to the number of the light receiving elements 311 that have failed, and corrects the intensity signal. The gain G in this case is represented by the following equation (3), for example.

G=(NM)/N (3)

When detecting the failure of the light receiving element 311, the failure detecting unit 60 outputs error information indicating that the failure of the light receiving element 311 is detected to the external device. The error information includes, for example, the coordinates of the pixel 31 having the failed light receiving element 311, the number of failed light receiving elements 311, the number of 0 fixed light receiving elements 311 and the 1 fixed light receiving elements of the failed light receiving elements 311. Information such as a breakdown of the number of 311 is included.

FIG. 7 schematically shows a control method of the optical distance measuring device 10 of the present embodiment using a flowchart. In the optical distance measuring device 10 of the present embodiment, in step S10, the light source 21 is driven by the irradiation unit 20 to irradiate the space with light. In step S20, the light receiving section 30 including the light receiving element 311 detects the reflected light from the object in the space. In step S30, an intensity signal representing the intensity of the reflected light detected by the light receiving element 311 is output from the intensity signal output unit 41. At this time, when the failure detection unit 60 detects the failure of the light receiving element 311, the intensity signal output unit 41 obtains the gain G according to the number of failures of the light receiving element 311 and outputs the intensity signal by the gain G. to correct. In step S40, the peak signal is detected by the signal processing unit 43 using the histogram generated by the histogram generation unit 42 from the sequentially output intensity signals, and the peak signal is detected in step S40 from the light irradiation in step S10. The distance calculation unit 44 calculates the distance to the object in accordance with the time required to reach the object. In step S50, the distance value calculated in step S40 is output to the external device. In step S60, the failure detection unit 60 detects a failure of the light receiving element 311 included in each pixel 31 based on the maximum value and the minimum value of the intensity signal output from the intensity signal output unit 41. Information on the detected failure is output to the external device as an error. The series of processing shown in FIG. 7 is repeatedly executed in the optical distance measuring apparatus 10 in units of one frame. The process flow shown in FIG. 7 is a simplified flow, and the order of the processes may be appropriately changed. For example, the failure detection in step S60 may be performed in parallel with the processing in step S40 or step S50.

According to the optical distance measuring apparatus 10 of the present embodiment described above, the maximum value and the first reference value of the intensity signal of the reflected light obtained a plurality of times, or the minimum value and the second reference of the intensity signal obtained a plurality of times. Since the failure of the light receiving element 311 can be detected by comparing with the value, the failure of the light receiving element 311 can be detected by a simple method. Further, in the present embodiment, the number of failures of the light receiving element 311 is estimated, and the intensity signal is corrected according to the estimation result, so that the peak signal can be accurately detected from the histogram. As a result, the accuracy of distance measurement can be improved. Further, in the present embodiment, when the failure is detected, the error information is output, so that the external device can take an appropriate countermeasure based on the error information. For example, the external device determines, based on the error information, whether to use the distance value output from the optical distance measuring device 10, whether to stop the vehicle, or whether to cancel the automatic driving function. You can

B. Second embodiment:
In the second embodiment, the failure detection unit 60 changes the reliability of failure determination according to the brightness of the surroundings. The failure detection unit 60 can determine the ambient brightness by determining day and night based on the current time, for example. Further, the failure detection unit 60 can also determine the ambient brightness by receiving a signal indicating the intensity of the amount of solar radiation from the solar distance measuring device 10 or the solar radiation sensor provided in the vehicle. The ambient brightness can also be referred to as the amount of ambient light. When the failure detection unit 60 is attached to the vehicle, the ambient brightness also changes depending on the traveling time zone of the vehicle and the traveling location of the vehicle. Therefore, the brightness of the surroundings can be regarded as the traveling state of the vehicle.

In an environment where the surrounding brightness is dark, such as at night or in a tunnel, the signal level of the entire histogram decreases as shown in FIG. Therefore, in an environment where the surrounding brightness is dark, the maximum value of the intensity signal is unlikely to be the first reference value or more. Therefore, it becomes difficult for the failure detection unit 60 to determine whether or not the light receiving element 311 has failed, more specifically, whether or not the output level is fixed to the minimum level. On the other hand, in an environment with bright surroundings such as daytime, the signal level of the entire histogram increases as shown in FIG. Therefore, in an environment with bright surroundings, the maximum value of the intensity signal is likely to be the first reference value or more. Therefore, the failure detection unit 60 can easily determine whether or not the light receiving element 311 has failed, more specifically, whether or not the output level is fixed to the minimum level.

Therefore, in the present embodiment, when the failure detection unit 60 determines that the light receiving element 311 has failed, the failure detection unit 60 changes the reliability of the determination result according to the ambient brightness. Specifically, the failure detection unit 60 represents the reliability of the determination result as a percentage and outputs the percentage as error information. For example, the failure detection unit 60 outputs an error by setting the possibility of failure to, for example, 50% when it is determined that there is a failure when the surrounding brightness is dark. Further, when the surrounding brightness is bright, the failure detection unit 60 outputs an error by setting the possibility of failure to, for example, 100% when the failure is determined. By doing so, the external device that has acquired the error information can take measures according to the possibility of failure of the light receiving element 311. The value of the possibility of failure may be changed according to the brightness of the surroundings. Specifically, the brighter the surroundings, the larger the percentage value. By doing so, the optimum reliability can be output according to the ambient brightness.

In the present embodiment, the reliability of the failure determination is changed according to the brightness of the surroundings, but the failure detection unit 60 may change the first reference value according to the brightness of the surroundings. Good. For example, the failure detection unit 60 lowers the first reference value when the surrounding brightness is dark, and increases the first reference value when the surrounding brightness is bright. In this way, if the first reference value is changed according to the brightness of the surroundings, the optimum first reference value can be dynamically set according to the brightness of the surroundings, so that the failure determination can be performed accurately. It can be carried out.

C. Third embodiment:
As shown in FIG. 10, in the third embodiment, the optical distance measuring device 10 includes a light shielding mechanism 35 configured to shield the light receiving unit 30 in the housing 15. The light blocking mechanism 35 includes a rotary mirror 36 and a non-reflective material 37. The drive of the rotary mirror 36 is controlled by the controller 50 (see FIG. 2). As shown in FIG. 10, the control unit 50 normally guides the reflected light incident through the window 16 provided in the housing 15 to the light receiving unit 30 by the rotary mirror 36. On the other hand, when the failure detection unit 60 detects the light receiving element 311 whose output level is fixed to 1, the control unit 50 rotates the rotary mirror 36 to cause reflection, as shown in FIG. The light is guided to the non-reflecting material 37 so that the reflected light does not reach the light receiving section 30. In the state where the reflected light does not reach the light receiving unit 30, the influence of the ambient brightness can be suppressed to the minimum, so that when the light receiving element 311 having the output level fixed to 1 exists, the intensity signal output unit. The intensity signal output from 41 (see FIG. 2) is likely to be larger than the second reference value. Therefore, it is possible to accurately detect the light receiving element whose output level is fixed to 1. It should be noted that FIGS. 10 and 11 schematically show only a part of the configuration of the optical distance measuring device 10.

D. Fourth Embodiment:
In the fourth embodiment, the failure detection unit 60 uses the intensity signal of the pixel 31 adjacent to the target pixel among the plurality of pixels 31 as a reference value and compares it with the intensity signal of the target pixel to determine the target pixel. A failure of the included light receiving element 311 is detected.

Specifically, as shown in FIG. 12, in the failure detection unit 60, the maximum value of the intensity signal in the target pixel E is lower than the maximum value of the intensity signal of the adjacent pixels B and H (or the pixels D and F). , If it is significantly small, it is determined that the light receiving element having the output level fixed to 0 exists in the target pixel E. In the failure detection unit 60, the minimum value of the intensity signal of the target pixel E is significantly larger than the minimum value of the intensity signals of the adjacent pixels B and H (or the pixels D and F), as shown in FIG. In this case, it is determined that the light receiving element whose output level is fixed to 1 exists in the target pixel E.

If the pixels 31 are normal, the intensity signals output from the adjacent pixels 31 are likely to have similar values. Therefore, as in the present embodiment, it is also possible to determine the failure of the light receiving element 311 in the target pixel by using the intensity signal of the adjacent pixel as the reference value.

In the present embodiment, the adjacent pixels used for comparison are not limited to the two pixels that are adjacent to the target image in the left-right direction or in the vertical direction, but may be four pixels that are adjacent in the vertical and horizontal directions. Further, it may be eight pixels surrounding the target image. Further, the criterion of being significantly small or significantly large is, for example, the average value of the maximum value or the minimum value of the intensity signals of a plurality of adjacent pixels is obtained as a reference value, and the reference value is set to a predetermined ratio (eg, 20%). %) or more, it can be judged to be significantly small, and if the signal strength exceeds the reference value by a predetermined ratio (for example, 20%) or more, it is judged to be significantly large. be able to. Further, the intensity signal of the target pixel to be compared and the intensity signal of the adjacent pixel may each be one value acquired in each frame, or a plurality of intensity signals acquired over a plurality of frames. It may be a representative value such as an average value, maximum value, minimum value, or the like. Note that, also in the present embodiment, the failure detection unit 60 can estimate the value of the difference between the intensity signal of the target pixel and the intensity signal of the adjacent pixel used as the reference value as the number of the light-receiving elements 311 that have failed. Is.

E. Other embodiments:
(E-1) In each of the above-described embodiments, the optical distance measuring apparatus 10 has a function of estimating the number of light-receiving elements 311 that have failed, a function of correcting the intensity signal according to the number of light-receiving elements 311 that have failed, and error information. May be provided at all, or at least a part or all may not be provided.

(E-2) In each of the above-described embodiments, the histogram generation unit 42 may generate a histogram by integrating the intensity signals output from the intensity signal output unit 41 multiple times. By doing so, the SN ratio of the histogram can be improved. Specifically, the irradiation unit 20 irradiates the same position in space with light a plurality of times, and the light receiving unit 30 receives reflected light with respect to the same pixel 31 a plurality of times. Then, the intensity signal output unit 41 outputs the intensity signal for the same pixel 31 a plurality of times, so that the histogram generation unit 42 integrates the intensity signals a plurality of times to generate a histogram.

When the intensity signals are integrated a plurality of times in this way to generate a histogram, the failure detection unit 60 uses the integrated intensity signal (maximum value or minimum value) and a reference value (first reference value or second reference value). ) Is divided by a predetermined coefficient of 1 or more according to the number of times of integration, the number of defective light receiving elements 311 can be estimated.

(E-3) In the above-described embodiment, each pixel 31 included in the light receiving unit 30 includes the SPAD as the light receiving element 311. On the other hand, each pixel 31 may include a light receiving element other than the SPAD, such as a pin photodiode or an avalanche photodiode, as the light receiving element 311. In this case, if the light receiving element can output a signal of stepless or multistep levels according to the intensity of the received reflected light, the distance is measured using the level of the signal without generating a histogram. It is also possible to do so.

(E-4) In the above-described embodiment, the optical distance measuring device 10 employs the different axis type optical system in which the optical axis for light projection and the optical axis for light reception are different. On the other hand, the optical distance measuring device 10 may employ a coaxial type optical system in which the optical axis of light projection and the optical axis of light reception coincide with each other. Further, in the above-described embodiment, the pixels are arranged in a plane in the vertical direction and the horizontal direction, but the pixels GT may be arranged in one line in a predetermined direction. Further, in the above-described embodiment, the optical distance measuring apparatus 10 adopts the 1D scanning method that scans the strip-shaped light in one direction as the scanning method, but the 2D that scans the point-shaped light in the two-dimensional direction. A scanning method may be adopted. Further, the optical distance measuring device 10 may be a flash type device that does not scan the light but irradiates the light in a wide range.

(E-5) In the above embodiment, when the failure detection unit 60 detects a failure of the light receiving element 311, the gain is obtained by the above equation (2) or equation (3) and is multiplied by the value of the intensity signal for correction. It is carried out. However, the method of correcting the intensity signal is not limited to this. For example, a value according to the number of failures of the light receiving element 311 may be simply added to or subtracted from the intensity signal. Specifically, when the light receiving element 311 whose output is fixed to 1 is detected, the intensity signal output unit 41 subtracts the number of the light receiving elements 311 from the intensity signal. Further, when the light receiving element 311 whose output is fixed to 0 is detected, the intensity signal output unit 41 adds the number of the light receiving elements 311 to the intensity signal. This also makes it possible to correct the intensity signal in accordance with the number of failures of the light receiving element 311.

The present disclosure is not limited to the above-described embodiments, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in each embodiment are appropriately replaced or combined in order to solve some or all of the above problems or to achieve some or all of the above effects. It is possible. If the technical features are not described as essential in this specification, they can be deleted as appropriate.

10 optical distance measuring device, 15 housing, 16 window, 20 irradiation unit, 21 light source, 22 scanning unit, 30 light receiving unit, 31 pixels, 32 light receiving surface, 35 light shielding mechanism, 36 rotary mirror, 37 non-reflective material, 40 Measurement unit, 41 intensity signal output unit, 42 histogram generation unit, 43 signal processing unit, 44 distance calculation unit, 50 control unit, 60 failure detection unit, 221 rotation axis, 222 mirror, 311 light receiving element

Claims (11)

There is an optical distance measuring device (10),
An illuminating section (20) for activating a light source (21) to illuminate the space with light;
A light receiving section (30) including a light receiving element (311) for detecting reflected light from an object in the space;
An intensity signal output section (41) for outputting an intensity signal representing the intensity of the reflected light detected by the light receiving element,
A measurement for detecting a peak signal from the intensity signals sequentially output from the intensity signal output unit, and measuring the distance to the object according to the time from the irradiation of light by the irradiation unit to the detection of the peak signal. Part (40),
A failure detection unit (60) for detecting a failure of the light receiving element by comparing the intensity signal with a reference value;
Optical distance measuring device. The optical distance measuring device according to claim 1, wherein
The failure detection unit obtains the maximum value of the intensity signal output from the intensity signal output unit multiple times, and the maximum value obtained multiple times, when the maximum value does not become a predetermined first reference value or more, An optical distance measuring device that determines that there is a light receiving element whose output level is fixed to the minimum level. The optical distance measuring device according to claim 1 or 2, wherein
The failure detection unit obtains a minimum value of the intensity signal output from the intensity signal output unit a plurality of times, and the minimum value obtained a plurality of times does not become a predetermined second reference value or less, An optical distance measuring device that determines that there is a light receiving element whose output level is fixed to the maximum level. The optical distance measuring device according to claim 2 or 3, wherein
The optical distance measuring device, wherein the failure detection unit estimates the number of failed light receiving elements based on a difference between a maximum value or a minimum value of the intensity signal and the reference value. The optical distance measuring device according to claim 4,
The optical distance measuring device, wherein the intensity signal output unit corrects the intensity signal in accordance with the number of the light-receiving elements in failure estimated by the failure detection unit. The optical distance measuring device according to any one of claims 1 to 5,
The optical distance measuring device, wherein the failure detection unit changes reliability of failure determination according to ambient brightness. The optical distance measuring device according to any one of claims 1 to 5,
The optical distance measuring device, wherein the failure detection unit changes the reference value according to ambient brightness. The optical distance measuring device according to claim 3,
A light-shielding mechanism (35) configured to shield the light-receiving part from light,
The optical distance measuring device, wherein the failure detection unit determines whether or not there is a light receiving element in which the output level is fixed to the maximum level in a state where the light receiving unit is shielded from light by using the light shielding mechanism. The optical distance measuring device according to claim 1, wherein
The light receiving unit has a plurality of pixels (31), and each pixel includes a plurality of the light receiving elements,
The failure detection unit uses the intensity signal of a pixel adjacent to the target pixel of the plurality of pixels as the reference value and compares the intensity signal of the target pixel with the intensity signal of the target pixel to detect a light receiving element included in the target pixel. Optical distance measuring device that detects the breakdown of The optical distance measuring device according to any one of claims 1 to 9,
The optical distance measuring device, wherein the failure detection unit outputs error information when a failure of the light receiving element is detected. A method of controlling an optical distance measuring device, comprising:
Drive the light source to illuminate the space with light,
The reflected light from the object in the space is detected by a light receiving element,
Outputting an intensity signal representing the intensity of the reflected light detected by the light receiving element,
Detecting a peak signal from the intensity signal sequentially output, measuring the distance to the object according to the time from the irradiation of the light until the peak signal is detected,
Detecting a failure of the light receiving element by comparing the intensity signal with a reference value,
Control method.

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