Optical distance measuring device

Abstract

To provide an optical rangefinder capable of reducing the risk of miscalculating target distance without reducing the distance measurement range.SOLUTION: The optical rangefinder performs alternately a series of normal light emitting / receiving processing that irradiates at a normal level of irradiation intensity and a series of suppressed light receiving / emitting processing that suppresses irradiation intensity. The optical rangefinder compares the rising position of the received light pulse observed at the corresponding positions in the normal light receiving / emitting processing and the suppressed light receiving / emitting processing. When the two rising positions do not differ by more than a specified value, the optical rangefinder considers that the received light pulse is not that couples the light reflected from the target with the nearby body scattered light and calculates the distance relative to the rising position. On the other hand, when there is a difference of more than a specified value between the two rising positions, the optical rangefinder calculates the distance based on the trailing position.SELECTED DRAWING: Figure 14

Description

[Technical field]

[0001] The present disclosure relates to an optical distance measuring device that detects the distance to an object using a SPAD (Single Photon Avalanche Diode). [Background technology]

[0002] There is known an optical distance measuring device that measures the distance to a target by detecting the flight time of light emitted from a light source, reflected by the target, and reaching a sensor. Patent Document 1 discloses an optical distance measuring device using a SPAD as one type of such a device. That is, the optical distance measuring device disclosed in Patent Document 1 is premised on the premise that multiple SPADs are provided for each pixel, and the controller specifies the received light intensity for each pixel according to the number of SPADs responding to the reflected light from the target. Then, the distance value for each pixel is calculated based on the time from when light is irradiated from the light source to when the peak of the received light intensity is obtained. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-7950 A Summary of the Invention [Problem to be solved by the invention]

[0004] SPAD is a photodetector that uses avalanche multiplication, which amplifies electrons from a single incident photon like an avalanche, and can detect weaker light than other photodetectors. In other words, SPAD has the advantage that it can respond to even weak light, making it possible to measure distances over long distances with high accuracy.

[0005] However, in a configuration using a SPAD as a photodetector, due to the high responsiveness of the SPAD, in a real environment, the intensity value of each pixel (i.e., pixel value) is easily saturated by unwanted reflected light (so-called clutter). In addition, in order to extend the distance measurement range, which is the distance at which an object can be detected, it is necessary to increase the intensity of the sensing light, and the more the distance measurement range is extended, the more likely the pixel value is to be saturated by unwanted reflected light. Note that a state in which the pixel value is saturated refers to a state in which the upper limit of the observable range of received light intensity is reached. In addition, the unwanted reflected light may be internally scattered light generated by elements present inside the housing of the optical distance measuring device, attached object scattered light, which is scattered light by attached objects attached to the outside of the irradiation window, and multiple reflected light.

[0006] When unwanted reflected light is received at a level where the pixel value is saturated, it is difficult to determine whether the observed received light pulse is due to reflected light from the target, unwanted reflected light, or a combination of reflected light from the target and unwanted reflected light. If the entire received light pulse, which is a combination of unwanted reflected light and reflected light from the target, is considered to be due to reflected light from the target, errors will occur in feature quantities such as the peak position and rising position corresponding to the reflected light from the target, which may lead to an erroneous determination of the target position.

[0007] The present disclosure has been made based on the above considerations or points of view, and one of its objectives is to provide an optical distance measuring device that can reduce the risk of miscalculating the distance to a target without reducing the distance measurement range. [Means for solving the problem]

[0008] The optical distance measuring device disclosed herein is an optical distance measuring device that detects the distance to a target using the round-trip time of light to the target, and includes an irradiation unit (4) that irradiates sensing light, which is light having a predetermined wavelength, toward a predetermined direction to be detected, a plurality of optical detectors (5s) that respond to the sensing light and are arranged in a matrix, a level adjustment unit (F3) that switches the irradiation intensity of the sensing light output from the irradiation unit or the detection sensitivity of the plurality of optical detectors from a predetermined normal level to a suppression level that is a predetermined amount lower than the normal level, a peak detection unit (8) that detects received light pulses and their peaks corresponding to reflected light, which is light that is the sensing light reflected by an object and returned, based on time series data of the number of responses of the optical detectors, a pulse information acquisition unit (F2) that is configured to acquire a data set indicating a predetermined feature amount related to the received light pulses detected by the peak detection unit as pulse information, and that acquires normal pulse information, which is pulse information when the normal level is applied, and suppression pulse information, which is pulse information when the suppression level is applied, and a distance calculation unit (F4) that calculates a distance value to the target based on the normal pulse information and the suppression pulse information.

[0009] In the above configuration, the distance to the target is calculated using not only normal pulse information, which is pulse information observed when the normal level is applied, but also suppression pulse information, which is pulse information observed when the suppression level is applied. When the suppression level is applied, the irradiation intensity or detection sensitivity of the sensing light is reduced compared to the normal level, so that the phenomenon in which the pixel value is saturated by the unnecessary reflected light is unlikely to occur. Accordingly, the waveform of the received light pulse differs when the reflected light from the target is received, when only the unnecessary reflected light is received, and when the reflected light from the target and the unnecessary reflected light are combined. Therefore, by using the normal pulse information and the suppression pulse information in combination, it is possible to determine whether the observed received light pulse is due to the reflected light from the target, due to the unnecessary reflected light, or the reflected light from the target and the unnecessary reflected light are combined. In addition, by using not only the suppression pulse information but also the normal pulse information, it is possible to detect a target that is relatively far away. In other words, it is possible to reduce the risk of miscalculating the distance to the target without reducing the ranging range.

[0010] In addition, the symbols in parentheses in the claims indicate a correspondence with the specific means described in the embodiments described below as one aspect, and do not limit the technical scope of the present disclosure. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a block diagram showing a configuration of an optical distance measuring device. [Diagram 2] FIG. 2 is a conceptual diagram for explaining the configuration of a light receiving array. [Diagram 3] FIG. 13 is a diagram showing a modified example of the allocation of cell groups corresponding to each pixel. [Figure 4] 10A and 10B are diagrams for explaining a feature amount of a received light pulse. [Diagram 5] 11 is a diagram for explaining a method for determining a peak arrival time when the peak intensity is saturated. FIG. [Figure 6] FIG. 13 is a diagram for explaining nearby object scattered light. [Figure 7] FIG. 11 is a diagram for explaining multiple reflected light. [Figure 8] 11A and 11B are diagrams for explaining the influence of the type of unwanted reflected light on the rise determination time and the pulse width. [Figure 9] FIG. 2 is a functional block diagram of a control unit. [Figure 10] 4A to 4C are diagrams for explaining the operation of the optical distance measuring device. [Figure 11] FIG. 11 is a diagram showing an example of a calculation formula corresponding to each observation pattern. [Figure 12] 13A and 13B are diagrams illustrating other examples of arithmetic expressions corresponding to the respective observation patterns. [Figure 13] FIG. 11 is a diagram showing an example of a calculation formula corresponding to each observation pattern. [Figure 14] 13 is a flowchart showing a method for determining an observation pattern. [Figure 15] 13 is a conceptual diagram showing the difference in peak arrival time observed between normal light reception and emission processing and suppressed light reception and emission processing when the target reflected light is combined with scattered light. FIG. [Figure 16] 13 is a conceptual diagram showing the difference in peak arrival time observed between normal light reception and emission processing and suppressed light reception and emission processing when the target reflected light is combined with multiple reflected light. FIG. [Figure 17] 13 is a flowchart showing another example of a method for determining an observation pattern. [Figure 18] 13 is a flowchart showing another example of a method for determining an observation pattern. [Figure 19] 13 is a conceptual diagram showing a difference in rise determination time observed between normal light reception and emission processing and suppressed light reception and emission processing when the target reflected light is combined with multiple reflected light. FIG. [Figure 20] 13 is a conceptual diagram showing a difference in rise determination time observed between normal light reception and emission processing and suppressed light reception and emission processing in a case where the target reflected light is combined with scattered light. FIG. [Figure 21] FIG. 13 is a diagram showing a modified example of the configuration of the optical distance measuring device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. The optical distance measuring device 1 shown in FIG. 1 is a device that measures the distance to an object from the round trip time of light to the target. The optical distance measuring device 1 is also called LiDAR (Light Detection and Ranging / Laser Imaging Detection and Ranging). In the present disclosure, a target refers to various objects that can reflect light. Targets may include other vehicles, pedestrians, median strips, guardrails, and other objects that are independent of the host vehicle and may be obstacles to the vehicle's driving control. In the present disclosure, a host vehicle refers to a vehicle on which the optical distance measuring device 1 is mounted.

[0013] As described below, the optical distance measuring device 1 includes an irradiation unit 4 that irradiates sensing light, which is pulsed light, and a light receiving array 5 in which a plurality of light receiving elements are arranged in an array. The optical distance measuring device 1 generates a distance image as data indicating the distance measurement result based on the time from when the sensing light is irradiated from the irradiation unit 4 to when each light receiving element receives reflected light corresponding to the sensing light (so-called ToF: Time of Flight).

[0014] A distance image is data that has a plurality of pixels, and the value of each pixel indicates the distance to an object. As shown in Fig. 1, the optical distance measuring device 1 is connected to a vehicle condition sensor 101 and an on-board ECU 102. In this disclosure, ECU is an abbreviation for Electronic Control Unit, and means an electronic control device. The optical distance measuring device 1 is connected to the vehicle condition sensor 101 and the on-board ECU 102 via an in-vehicle network. Of course, the optical distance measuring device 1 may be directly connected to some of the sensors / ECUs using dedicated communication lines.

[0015] The irradiation pattern of the sensing light in the optical distance measuring device 1 may be a scan type or a flash type. The scan type refers to a type of sweeping irradiation of the sensing light by dynamically changing the angle of the reflector relative to the irradiation unit 4 using an actuator. The scanning direction may be horizontal or vertical. The flash type is a type of irradiation of diffused sensing light at once toward an angle range corresponding to a desired detection range. The present disclosure is applicable to both the scan type and the flash type.

[0016] The vehicle state sensor 101 is a sensor for detecting information on the behavior of the vehicle itself and information on driving operations that affect the behavior of the vehicle itself (hereinafter, vehicle information). The vehicle information includes, for example, the running speed of the vehicle itself, the acceleration acting on the vehicle itself, the yaw rate, the pedal operation amount, and the steering angle. The pedal operation amount refers to the depression amount / depression force of the accelerator pedal and the brake pedal, respectively. A signal indicating the state of the vehicle power supply can also be included in the vehicle information. The state of the vehicle power supply includes whether or not the running power supply is on. The running power supply is a power supply for running the vehicle, and refers to the ignition power supply if the vehicle is an engine vehicle. If the vehicle is an electric vehicle, the running power supply refers to the system main relay. Electric vehicles include not only electric vehicles but also plug-in hybrid vehicles, hybrid vehicles, and the like. A plurality of vehicle state sensors 101, each of which has a different detection target, can be connected to the optical distance measuring device 1. The vehicle state sensor 101 outputs a signal indicating the detection result to the optical distance measuring device 1.

[0017] The in-vehicle ECU 102 is any ECU mounted on the vehicle. For example, the optical distance measuring device 1 is connected to a driving assistance ECU and the like for use. The driving assistance ECU is an ECU that executes a process to assist the driver in driving operations. The driving assistance ECU notifies the driver of a collision with another moving object or a stationary object based on the detection result of the optical distance measuring device 1. The driving assistance ECU may not only provide information, but also perform automatic braking control or steering according to the detection result of the optical distance measuring device 1. The other moving objects refer to pedestrians, other vehicles, cyclists, etc. The driving assistance ECU may be an automatic driving device that autonomously drives the vehicle to a destination that is set in advance. The driver in this disclosure refers to a person sitting in the driver's seat, that is, a driver's seat occupant. The term driver refers to a person who should receive the authority to drive from the automatic driving system during automatic driving. The concept of a driver can include an operator who remotely operates the vehicle.

[0018] <Configuration of optical distance measuring device 1> As shown in FIG. 1, the optical distance measuring device 1 includes a control unit 2, an irradiation control circuit 3, an irradiation unit 4, a light receiving array 5, a response determiner 6, an adder 7, and a peak detection unit 8. As shown in a separate figure, the optical distance measuring device 1 also includes a housing 9 that houses these components. The housing 9 is provided with an irradiation window 91 for irradiating sensing light. The irradiation window 91 is realized using a light-transmitting member, such as a transparent resin panel or glass. The irradiation window 91 can also function as a window through which the light receiving array 5 receives reflected light from a target. The irradiation window 91 and the window for receiving light may be provided separately. The irradiation window 91 may also be called an optical window.

[0019] The control unit 2 controls the operation of the optical distance measuring device 1. The control unit 2 inputs a signal related to the irradiation setting of the sensing light to the irradiation control circuit 3. The control unit 2 also acquires pulse information of the received light pulse corresponding to the reflected light from the peak detection unit 8. The control unit 2 is realized by using a processor 21, a RAM (Random Access Memory) 22, and a storage 23. The control unit 2 includes a DSP (Digital Signal Processor) and a CPU (Central Processing Unit) as the processor 21. Various functions of the control unit 2 are realized by the processor 21 executing a program stored in the storage 23. Details of the functions of the control unit 2 will be described separately later.

[0020] The irradiation control circuit 3 causes the irradiation unit 4 to irradiate sensing light at a predetermined irradiation interval based on a command from the control unit 2. The irradiation control circuit 3 controls the pulse width, irradiation intensity, irradiation interval, etc. of the sensing light irradiated from the irradiation unit 4. The irradiation intensity corresponds to the peak height (so-called peak power) of the pulse light output as the sensing light. In this disclosure, the sensing light irradiated from the irradiation unit 4 is also referred to as the irradiated light in order to distinguish it from the sensing light received as reflected light. The pulse width of the irradiated light is set to, for example, 5 nanoseconds. Of course, the pulse width of the irradiated light may be 20 nanoseconds, 10 nanoseconds, or 1 nanosecond. The pulse width of the irradiated light may also be set to a value less than 1 nanosecond, such as 50 picoseconds, 100 picoseconds, or 200 picoseconds.

[0021] The irradiation control circuit 3 is configured to be able to switch the irradiation intensity of the sensing light between a normal level and a suppression level. The normal level is set to a predetermined value for realizing a desired distance measurement range. The distance measurement range corresponds to a detectable distance, which is a distance at which a predetermined object set in the target can be detected. For example, the normal level is set to an intensity that can realize a distance measurement range of about 250 m or 300 m. The suppression level is set to a value of about 1 / 50 of the normal level. The suppression level may be 1 / 10, 1 / 100, 1 / 200, or 1 / 1000 of the normal level. The suppression level is set to a value that can detect an object in a nearby area described later, for example, within 3 m. The adjustment of the irradiation intensity may be realized by using a variable gain amplifier that can adjust the degree of amplification, or may be realized by switching the drive voltage of the irradiation unit 4. In addition, the switching between the normal level and the suppression level may be realized by switching the light source itself or the number of light sources, etc. In other words, a light source for a normal level and a light source for a suppressed level may be separately provided, and the illumination control circuit 3 may be configured to selectively use them to alternately / selectively perform illumination at the normal level and illumination at the suppressed level.

[0022] The irradiation unit 4 includes, for example, a laser diode as a light source, and emits light of a predetermined wavelength as sensing light from this light source toward a predetermined detection target direction. The detection target direction corresponds to an area in which a target to be measured is to be detected. In the scanning type optical distance measuring device 1, the detection target direction may be dynamically changed using a mirror or the like. In the flash type optical distance measuring device 1, the detection target direction may have a predetermined angular range in the vertical and horizontal directions.

[0023] The sensing light is infrared light, but may be visible light. For example, the sensing light is light belonging to the 900±50 nm band, which is common for laser light. The irradiation unit 4 may be configured to output laser light with a wavelength of 1400 nm or more, such as 1550 nm. A configuration that employs electromagnetic waves of 1400 nm or more as the sensing light makes it easier to increase resistance (e.g., signal-to-noise ratio) to white noise such as sunlight. In addition, there is an advantage that the output limit stipulated by the IEC (International Electrotechnical Commission) can be relaxed from the viewpoint of human body protection.

[0024] The light receiving array 5 has a plurality of light receiving cells 5s capable of outputting a pulse signal in response to the incidence of reflected light from an object. Each light receiving cell 5s has a SPAD (Single Photon Avalanche Diode) as a light receiving element. The SPAD is a type of avalanche photodiode. The SPAD operates by applying a voltage higher than the breakdown voltage as a reverse bias voltage. The light receiving cell 5s is configured to detect a voltage change when the SPAD breaks down due to the incidence of photons, and output a digital pulse (hereinafter, a pulse signal) of a predetermined pulse width.

[0025] For example, the light receiving cell 5s includes a quench circuit connected in series to a SPAD serving as a light receiving element. The quench circuit can be configured using, for example, a resistive element having a predetermined resistance value (a so-called quench resistor) or a MOSFET. When the SPAD breaks down and a current flows through the quench circuit, the light receiving cell 5s outputs a digital pulse having a value of 0 as the above-mentioned pulse signal. In this way, each light receiving cell 5s is configured to output a pulse signal when the SPAD responds. The light receiving cell 5s corresponds to a photodetector.

[0026] The light receiving cells 5s are arranged in a two-dimensional matrix (lattice). For example, the light receiving array 5 is configured as a silicon photomultiplier (SiPM) in which the light receiving cells 5s are arranged in an array. The number of rows and columns of the light receiving array 5 is appropriately designed based on the required resolution / number of pixels. The value of a certain pixel constituting a distance image is determined by the number of responses among the light receiving cells 5s that are assigned in advance to the pixel. In other words, one pixel is constituted by one set of the light receiving cells 5s. FIG. 2 illustrates an example in which one pixel is constituted by 16 light receiving cells 5s (4×4). The dashed lines in the figure indicate the boundaries of the pixels. Of course, the number of light receiving cells 5s constituting one pixel is not limited to 16, and may be 64, 128, 256, or the like. The value of one pixel may be determined based on the output of 128 light receiving cells 5s (8 horizontal×16 vertical).

[0027] In the present disclosure, a group of a plurality of light receiving cells 5s corresponding to one pixel is also referred to as a cell group Sgr. The size of the cell group Sgr corresponds to the size of one element (i.e., pixel) constituting a distance image. Each cell group Sgr outputs 0 to 16 pulse signals according to the intensity of the received light. FIG. 2 shows an embodiment in which individual pixels are set not to share the light receiving cells 5s, but this is not limited to this embodiment. As another embodiment, as shown in FIG. 3, each cell group Sgr may be set to overlap with another adjacent cell group Sgr. That is, one light receiving cell 5s may belong to multiple cell groups Sgr. The shape of the cell group Sgr is not limited to a square, but may be a rectangle. That is, the number of rows and columns of the light receiving cells 5s corresponding to one pixel may be different. The light receiving array 5 has a number of light receiving cells 5s that can generate a distance image of, for example, one million pixels.

[0028] The light receiving array 5 is switched to a light receiving state capable of detecting light by a control signal from the control unit 2. For example, the control unit 2 outputs a signal instructing irradiation of sensing light to the irradiation control circuit 3, and drives each light receiving cell 5s for a certain period of time by inputting a predetermined control signal to the light receiving array 5. Of course, in another embodiment, each light receiving cell 5s may be configured to constantly maintain a drive state capable of responding according to the intensity of incident light.

[0029] The response determiner 6 is configured to determine whether or not a pulse signal is input from the light receiving cell 5s, i.e., whether or not the SPAD is responding. The response determiner 6 is provided for each light receiving cell 5s. The output of the light receiving cell 5s is sampled at a predetermined clock frequency. The response determiner 6 is configured to output a high level when the light receiving cell 5s is responding and a low level when the light receiving cell 5s is not responding. The response determiner 6 may be configured integrally with the light receiving cell 5s and thus the light receiving array 5.

[0030] The adder 7 adds and outputs the pulses output from the multiple response determiners 6. An adder 7 is provided for each pixel, in other words, for each cell group Sgr. Each adder 7 may be realized as software or hardware. For example, the multiple adders 7 may be realized using, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The same applies to the peak detection unit 8 described later.

[0031] The output of the adder 7 indicates the response number of the light receiving cell 5s in the cell group Sgr corresponding to the adder 7. In this disclosure, the output from the adder 7 is also referred to as the received light intensity or level value. The level value can also be said to be a value indicating the intensity of the incident light. Therefore, the output level of each adder 7 indicates the received light intensity at each pixel.

[0032] As described above, each of the multiple light receiving cells 5s constituting the light receiving array 5 outputs a pulse signal at a frequency according to the amount of surrounding light. Therefore, when reflected light from a target is incident on the light receiving cell 5s, the number of pulse signals output from the light receiving cell 5s per unit time, i.e., the pulse rate, increases significantly. Accordingly, the output level of the adder 7 may also transition in a pulsed manner at a timing corresponding to the reception of reflected light. For convenience, a continuous signal series whose peak exceeds a predetermined level is referred to as a light receiving pulse.

[0033] The peak detection unit 8 detects peaks of the received light intensity based on the time series data of the received light intensity output by the adder 7. The peak corresponds to the time when the received light intensity turns from increasing to decreasing. A peak detection unit 8 is provided for each adder 7, in other words, for each pixel. The peak detection unit 8 generates a histogram indicating the received light intensity (level value) for each time, for example. The generated histogram is stored in a memory or RAM 22 (not shown) in a predetermined format such as a table.

[0034] As shown in FIG. 4, the peak detection unit 8 detects a light receiving pulse and its peak based on the time series data (histogram) of the level value, and acquires pulse information associated with the peak. Since the light receiving pulse and the peak correspond one-to-one, the description of the light receiving pulse in the following description can be understood by replacing it with the peak. The pulse information includes, for example, peak intensity Pq, peak arrival time Tp, rising edge determination time Ta, falling edge determination time Tb, and pulse width Tw. The peak detection unit 8 can be understood as a configuration for extracting a feature amount of the light receiving pulse. In the present disclosure, a series of processes for irradiating sensing light and acquiring pulse information for each pixel as a light receiving result within a certain time from the irradiation is also referred to as a light receiving / emitting process. The light receiving / emitting process can be called a light emitting / receiving process based on the order of the actions to be performed. The light receiving / emitting process can also be called a sensing process or a scanning process.

[0035] The peak intensity Pq indicates the intensity at the point when the intensity in the waveform is at its maximum (i.e., the peak value). The peak intensity Pq corresponds to the value immediately before the received light intensity starts to decrease, in other words, the intensity at the time when the slope becomes 0. The slope here corresponds to the time rate of change of the received light intensity. If the intensity of the received light pulse reaches the measurement upper limit value Pmx as shown in FIG. 5, the measurement upper limit value Pmx becomes the peak intensity Pq. The measurement upper limit value Pmx corresponds to the maximum value in the range of values ​​that can be output by the adder 7. The measurement upper limit value Pmx corresponds to the number of light-receiving cells 5s that make up the cell group Sgr. If the number of light-receiving cells 5s that make up one cell group Sgr is 256, the sensor upper limit value is 256.

[0036] Ta shown in FIG. 4 and FIG. 5 indicates the timing when the received light intensity becomes the judgment threshold Pth in the rising section, in other words, the rising judgment time which is the elapsed time from the irradiation of the sensing light until the received light intensity reaches the judgment threshold Pth. The rising judgment time Ta can also be called the threshold arrival time. The rising judgment time Ta corresponds to the rising position of the received light pulse. Moreover, Tb shown in the figure indicates the timing when the received light intensity becomes the judgment threshold Pth in the falling section, in other words, the falling judgment time which is the elapsed time until the received light intensity falls below the judgment threshold Pth. The falling judgment time Tb can also be called the below-threshold time. The falling judgment time Tb corresponds to the falling position of the received light pulse. In the present disclosure, the time when the received light intensity becomes the judgment threshold Pth in the rising section is also called the rising point, and the time when the received light intensity becomes the judgment threshold Pth in the falling section is also called the falling point.

[0037] The judgment threshold Pth is set to a value obtained by multiplying the actually observed peak intensity Pq by a predetermined coefficient k. The coefficient k may be, for example, 0.45, 0.50, 0.55, or 0.60. Here, as an example, k is set to 0.55 (corresponding to 55%). The judgment threshold Pth is a parameter that defines the so-called half-value point, which is the timing at which the received light intensity is half of the peak. The half-value point here is not limited to the point at which it is exactly 50%, and may be, as described above, a point at which it is 45%, 60%, or the like.

[0038] The light receiving intensity output by the adder 7 may include a stationary noise component, which is a stationary noise due to sunlight or the like. Therefore, the peak intensity Pq may be a value in which the stationary noise component is superimposed on the target reflected light component. If 50% of the raw value of the peak intensity Pq is considered to be the rising position, the rising position will be determined at a point lower than the true rising position due to the stationary noise component. In order to detect the half-value point of the pure target reflected light component as the rising position / falling position, the peak detection unit 8 may dynamically adjust the coefficient k according to the magnitude of the stationary disturbance component due to sunlight or the like. For example, the coefficient k may be set to a larger value as the stationary noise component becomes larger. Alternatively, if the magnitude of the stationary noise component is Pn, the peak detection unit 8 may be configured to detect the points at which (Pq-Pn)·k+Pn are satisfied as the rising position and the falling position. The magnitude of the stationary noise component can be determined based on the light receiving intensity before the irradiation of the sensing light. Additionally, the peak detector 8 may determine the peak intensity Pq, the rising edge position / falling edge position, etc. from time-series data of the corrected received light intensity obtained by removing stationary noise components from the output value of the adder 7.

[0039] Tpa in FIG. 5 indicates the upper limit arrival time, which is the time when the intensity reaches the measurement upper limit value Pmx in the waveform. Tpb indicates the upper limit departure time, which is the time immediately before the intensity starts to fall (leave) from the measurement upper limit value Pmx in the waveform. The upper limit departure time Tpb is the point corresponding to the latest time in the period in which the received light intensity is saturated, and specifically corresponds to the point one bin / one frame before the time when the intensity leaves the measurement upper limit value Pmx. Tpc indicates an intermediate time located between the upper limit arrival time Tpa and the upper limit departure time Tpb. In this disclosure, the observation point corresponding to the upper limit arrival time Tpa is also referred to as the upper limit arrival point, and the observation point corresponding to the upper limit departure time Tpb is also referred to as the falling start point or the upper limit departure point.

[0040] The peak arrival time Tp is the elapsed time from the irradiation of the sensing light to the observation of the peak intensity Pq. The peak arrival time Tp can be expressed by the number of clocks from the irradiation of the sensing light to the observation of the peak intensity Pq. The peak arrival time Tp indicates the peak position on the time axis. If the peak detected by the peak detection unit 8 corresponds to the reflected light from the target, the peak arrival time Tp corresponding to the peak corresponds to the round-trip flight time (ToF: Time of Flight) to the target. Therefore, the control unit 2 can calculate the distance to the target for each pixel by multiplying the peak arrival time Tp by C / 2 (C is the speed of light).

[0041] 5, when the true peak becomes unclear due to the received light intensity reaching the measurement upper limit value Pmx, the peak detection unit 8 adopts the intermediate time Tpc as the peak arrival time Tp. In another aspect, the peak detection unit 8 may adopt the upper limit arrival time Tpa as the peak arrival time Tp. The peak detection unit 8 may estimate the peak arrival time Tp based on the slope at the determination threshold value Pth in the rising section and the slope at the determination threshold value Pth in the falling section.

[0042] The pulse width Tw is a parameter indicating the width of the received light pulse. The pulse width Tw corresponds to the length of time during which the received light intensity is equal to or greater than the judgment threshold Pth. In other words, the pulse width Tw can be determined by subtracting the rising judgment time Ta from the falling judgment time Tb. As described above, the judgment threshold Pth can be dynamically determined according to the peak intensity, for example, 50% of the maximum intensity in the waveform. In addition, considering that the output of the adder 7 is superimposed with stationary noise components, the calculation method of the judgment threshold Pth and the rising / falling positions is designed so that the peak detection unit 8 can calculate (evaluate) the pulse width of the pure target reflected light component.

[0043] Various parameters such as the peak intensity Pq, peak arrival time Tp, rising edge determination time Ta, falling edge determination time Tb, and pulse width Tw correspond to the feature quantity of the received light pulse. The upper limit arrival time Tpa and the upper limit departure time Tpb can also be included in the feature quantity of the received light pulse. Note that the peak detection unit 8 does not necessarily need to acquire all of the above-mentioned parameters as the detected object information. The peak detection unit 8 may be configured to acquire only the predetermined parameters necessary for the distance calculation process among all of the above-mentioned parameters. In this disclosure, "acquisition" also includes generation / detection by internal calculation.

[0044] Note that multiple light receiving pulses (peaks) may appear for one pixel. For example, this can occur when reflected light from different objects reaches the same pixel, when light scattered by attached objects is received, when internally scattered light is received, or when multiple reflection occurs between a target that is some distance away.

[0045] When multiple light receiving pulses are detected in one light receiving / emitting process, the peak detection unit 8 of this embodiment outputs pulse information about the light receiving pulse with the largest peak intensity Pq among the multiple light receiving pulses. Note that the operation of the peak detection unit 8 is not limited to this, and the above-mentioned feature amount may be calculated for each light receiving pulse and output as pulse information. For example, the selection of peak information for each observed light receiving pulse may be performed by the control unit 2 instead of the peak detection unit 8. The peak detection unit 8 may be configured to output pulse information about the two light receiving pulses with the highest peak intensities Pq, for example.

[0046] In addition, the attachment scattered light in the present disclosure refers to sensing light reflected / scattered by an attachment 10, which is an object attached to the irradiation window 91, as indicated by xSL in FIG. 6. The irradiation window 91 is a window portion for outputting light from the light source to the outside of the housing 9. Since the irradiation window 91 also corresponds to a part of the housing, the attachment 10 can be understood as an object attached to the housing. The attachment 10 is, for example, mud, sand dust, raindrops, bird droppings, etc. In other words, the attachment scattered light refers to light reflected by raindrops, mud, etc. attached to the outer surface of the irradiation window 91.

[0047] The internal scattered light refers to light reflected by the inner surface of the irradiation window 91 or components inside the housing. In each figure, TgL indicates target reflected light, which is light reflected from the target. In this disclosure, scattered light by a sensor-proximate body, such as attachment scattered light or internal scattered light, is also referred to as proximity body scattered light or simply scattered light. The sensor-proximate body is an object that exists within 0.1 m from the irradiation unit 4, and refers to the irradiation window 91, components inside the housing, and attachments 10 on the irradiation window 91. If the optical distance measuring device 1 is attached to the interior surface of the windshield and used, the windshield can also be a sensor-proximate body.

[0048] In addition, the multiple reflected light in this disclosure refers to light that is reflected from the target by a part of the light reflected by the housing 9 of the optical distance measuring device 1, the vehicle body, or surrounding objects, and is then reflected back by the target, as indicated by MRL in Fig. 7. The dashed-dotted line in Fig. 7 indicates re-emitted light, which is a part of the light reflected from the target that is reflected by the housing 9 of the optical distance measuring device 1, etc. The two-dot dashed line indicates multiple reflected light, that is, double reflected light, which is the re-emitted light that is reflected back by the target. In this disclosure, the nearby object scattered light and the multiple reflected light are also collectively referred to as unwanted reflected light.

[0049] Incidentally, the pulse width of the sensing light is very short, about a few nanoseconds. In consideration of such circumstances, when the target is sufficiently far from the irradiation window 91, the target pulse, which is a light receiving pulse corresponding to the target reflected light, and the noise pulse, which is a light receiving pulse corresponding to the unnecessary reflected light, can be separated. However, when the target is present in the vicinity of the optical distance measuring device 1, the target pulse and the noise pulse can be combined. More specifically, the light receiving pulse corresponding to the attached object scattered light or the internally scattered light can be combined with the target pulse in a manner that it is located before the target pulse on the time axis. This is because the irradiation window 91, the attached object 10, etc. are located closer to the light receiving array 5 than the target. The light receiving pulse corresponding to the multiple reflected light can be combined with the target pulse in a manner that it is located after the target pulse on the time axis. This is because the optical path length is longer by the amount of multiple reflection.

[0050] In addition, due to the high responsiveness of the SPAD, in a real environment, the intensity value of each pixel (i.e., pixel value) may be saturated by unwanted reflected light (so-called clutter). A state in which the pixel value is saturated refers to a state in which the output level of the adder 7 has reached the measurement upper limit value Pmx.

[0051] Figure 8(A) conceptually shows the transition of the intensity output when the received light pulse corresponding to the nearby scattered light is combined with the target pulse. Also, Figure 8(C) conceptually shows the transition of the intensity output when the received light pulse derived from the multiple reflected light is combined with the target pulse. Note that Figure 8(B) shows the transition of the intensity output when there is no influence of unwanted reflected light. "When there is no influence of unwanted reflected light" refers to the case where the unwanted reflected light is not superimposed (combined) with the target reflected light (target pulse).

[0052] 8(A), (B), and (C), the upper graph shows the transition of the intensity of the light incident on the light receiving array 5, and the lower graph shows the transition of the output level of the adder 7. Note that the intensity of the incident light is expected to have a waveform with one apex as shown in the upper graph of Fig. 8(B), but since the adder 7 has an upper measurement limit value Pmx, the output level may have a trapezoidal shape.

[0053] As can be seen by comparing (A) and (B) in Figure 8, when the light reflected from the target is combined with the light scattered by a nearby object, the rising point or the upper limit arrival point shifts forward. As a result, the distance to the target may be calculated to be shorter than it actually is. On the other hand, when the light reflected from the target is combined with the light reflected multiple times, the falling point or the upper limit departure point shifts backward. In addition, in either case, the pulse width Tw itself becomes longer.

[0054] When the light receiving pulse due to the unwanted reflected light is combined with the target pulse in this way, the true feature value of the light receiving pulse corresponding to the target reflected light becomes unclear, and the target position may be erroneously determined. In other words, the distance to the target may be calculated shorter / longer than the actual distance. The optical distance measuring device 1 disclosed herein was created with a focus on the above problem, and incorporates a process for improving distance measurement accuracy by changing at least one of the parameters and the calculation formula used in the calculation process based on the observation results of the light receiving / emitting process at the normal / suppressed level.

[0055] The vicinity area of ​​the optical distance measuring device 1 is a range in which a noise pulse and a target pulse can be combined. The vicinity area refers to a range that is less than a predetermined vicinity distance determined according to the pulse width of the irradiated light from the optical distance measuring device 1. The vicinity distance can be a value obtained by adding a predetermined value determined according to the response characteristics of the circuit to half the distance obtained by multiplying the pulse width of the irradiated light by the speed of light. The response characteristics of the circuit include the recharge time (dead time) of the SPAD. For example, assuming that the pulse width is several nanoseconds, the vicinity distance can be set to about 2 m to 3 m. A state in which the target is sufficiently far away from the optical distance measuring device 1 corresponds to a state in which the target is present outside the vicinity area.

[0056] <Functions and operation of the control unit> The control unit 2 executes a program stored in the storage 23 to provide functions corresponding to various functional blocks shown in Fig. 9. That is, the control unit 2 includes, as functional blocks, an external information acquisition unit F1, a pulse information acquisition unit F2, a level adjustment unit F3, a distance calculation unit F4, and an image generation unit F5. The control unit 2 also includes a calculation parameter storage unit M1.

[0057] The calculation parameter storage unit M1 is a storage unit that stores various parameters used in the distance calculation process described below. The parameters used in the distance calculation process include a rise offset value. The calculation parameter storage unit M1 is realized using a part of the storage area of ​​the storage 23. The calculation parameter storage unit M1 may be realized using a non-volatile storage medium that is physically independent from the storage 23. The calculation parameter storage unit M1 is configured to allow the processor 21 to write, read, delete, and so on data.

[0058] The external information acquisition unit F1 acquires various information related to the state of the vehicle and the external environment from the vehicle state sensor 101 and the in-vehicle ECU 102. For example, the external information acquisition unit F1 may acquire information on three-dimensional objects existing around the optical distance measuring device 1 from the in-vehicle ECU 102, which corresponds to the driving assistance ECU. The surrounding three-dimensional objects may be identified based on the image analysis results of an in-vehicle camera that captures the outside of the vehicle or the output signal of a sonar. For example, assuming a scene just before or just after parking, other parked vehicles or walls may exist within a few meters from the vehicle. The control unit 2 may determine whether or not a three-dimensional object exists in the vicinity of the optical distance measuring device 1 based on the detection results of the external environment by other sensors, such as an in-vehicle camera or a sonar, as reference information. The control unit 2 may perform distance calculation processing that preferentially uses the results of reception and emission at a suppression level described later, on the condition that the other sensors have determined that a three-dimensional object exists within a predetermined distance from the optical distance measuring device 1.

[0059] Pulse information acquisition unit F2 acquires pulse information from peak detection unit 8 corresponding to each pixel. That is, pulse information acquisition unit F2 acquires pulse information for each pixel. Each pixel can be distinguished by a pixel number, which is a unique number for each pixel. Note that pulse information acquisition unit F2 may have some of the functions of peak detection unit 8. For example, peak detection unit 8 may only detect peaks, and pulse information acquisition unit F2 may perform the process of extracting the features of the received light pulse including the detected peaks. The functional arrangement can be changed as appropriate.

[0060] The level adjustment unit F3 is configured to adjust the irradiation intensity of the sensing light. Based on a switching pattern registered in advance, the level adjustment unit F3 switches the irradiation intensity from a normal level to a suppressed level, or from the suppressed level to the normal level. For example, the level adjustment unit F3 alternates between a state set at the normal level and a state set at the suppressed level for each light receiving and emitting process. This control mode corresponds to a configuration in which light receiving and emitting processes at the normal level and light receiving and emitting processes at the suppressed level are alternately performed.

[0061] Hereinafter, for the sake of simplicity, the light-receiving and emitting process at the normal level will be referred to as the normal light-receiving and emitting process, and the light-receiving and emitting process at the suppressed level will be referred to as the suppressed light-receiving and emitting process. Furthermore, the pulse information acquired by the normal light-receiving and emitting process will be referred to as the normal pulse information, and the pulse information acquired by the suppressed light-receiving and emitting process will be referred to as the suppressed pulse information. Furthermore, the peak arrival time Tp observed by the normal light-receiving and emitting process will be referred to as the normal peak time Tp1, and the peak arrival time Tp observed by the suppressed light-receiving and emitting process will be referred to as the suppressed peak time Tp2. The rising judgment time Ta observed by the normal light-receiving and emitting process will be referred to as the normal rising time Ta1, and the rising judgment time Ta observed by the suppressed light-receiving and emitting process will be referred to as the suppressed falling time Ta2. Furthermore, the pulse width Tw observed by the normal light-receiving and emitting process will be referred to as the normal pulse width Tw1, and the pulse width Tw observed by the suppressed light-receiving and emitting process will be referred to as the suppressed pulse width Tw2.

[0062] The distance calculation unit F4 generates a distance value for each pixel based on the feature amount of the received light pulse for each pixel observed in the normal / suppressed light reception / emission process. The operation of the distance calculation unit F4 will be described in detail later. The image generation unit F5 generates a data set in which the distance value for each pixel calculated by the distance calculation unit F4 is assigned as an element value of each pixel as a distance image. The image generation unit F5 may generate intensity image data, which is a data set in which the peak intensity Pq detected by the peak detection unit 8 is associated with each pixel. The image generation unit F5 may also generate image data in which each pixel includes distance information and intensity information.

[0063] FIG. 10 is a flowchart showing an example of the flow of distance measurement processing, which is processing in which the optical distance measuring device 1 calculates a distance value at each pixel. The distance measurement processing shown in FIG. 10 is performed at a predetermined sensing period on the condition that the driving power supply is on. The sensing period can be set to, for example, 100 milliseconds or 200 milliseconds. In this embodiment, as an example, the distance measurement processing includes steps S101 to S106. Note that the flowcharts in this disclosure are all examples, and the number of steps, processing order, execution conditions, etc. can be changed as appropriate.

[0064] Step S101 is a step for executing normal light receiving and emitting processing. Specifically, the level adjustment unit F3 cooperates with the irradiation control circuit 3 to cause the irradiation unit 4 to emit sensing light at a normal level. In addition, in conjunction with this, the light receiving array 5 is set to a standby state. Of course, the light receiving array 5 may be set to a standby state in which light can be detected at all times. In addition, the control unit 2 may set the light receiving array 5 to a standby state prior to the irradiation of the sensing light. The response state of each light receiving cell 5s constituting the light receiving array 5 is input to the peak detection unit 8 via the adder 7 corresponding to each pixel. Each peak detection unit 8 generates pulse information for each pixel based on the time series data of the output value of the corresponding adder 7, and inputs it to the control unit 2.

[0065] In step S102, the pulse information acquisition unit F2 acquires pulse information for each pixel as a result of the normal light receiving and emitting process (i.e., step S101). The pulse information may include predetermined types of features such as the peak arrival time Tp, the peak arrival time Tp, the rising edge determination time Ta, and the falling edge determination time Tb.

[0066] Step S103 is a step of executing suppressed light reception / emission processing. Specifically, the level adjustment unit F3 cooperates with the irradiation control circuit 3 to cause the irradiation unit 4 to irradiate the sensing light at a suppressed level. In step S104, the pulse information acquisition unit F2 acquires pulse information for each pixel as a result of the suppressed light reception / emission processing (i.e., step S103).

[0067] In the normal light receiving / emitting process, the output level is easily saturated even with the unwanted reflected light component, and it is difficult to distinguish whether the unwanted reflected light component is combined with the front or rear of the target pulse. On the other hand, in the suppressed light receiving / emitting process, the output level is less likely to be saturated with the unwanted reflected light component. In the suppressed light receiving / emitting process, a different waveform output is obtained depending on whether the unwanted reflected light combined with the target reflected light is scattered light or multiple reflected light. In other words, the control unit 2 as the distance calculation unit F4 can identify the type of unwanted reflected light combined with the target reflected light or the combined position of the unwanted reflected light by referring to the time series data of the received light intensity at the suppression level. The combined position of the unwanted reflected light corresponds to whether the unwanted reflected light is combined with the front side of the target reflected light or the rear side of the target reflected light.

[0068] The normal sequence consisting of steps S101 and S102 and the suppression sequence consisting of steps S103 and S104 differ only in the irradiation intensity of the sensing light, and other signal processing can be similar. The combination of features acquired in each sequence may be the same or different. According to a configuration in which the same combination of features is acquired in each sequence, the operation of the peak detection unit 8 and the pulse information acquisition unit F2 can be made common to each sequence. In addition, it is possible to increase the amount of information required for selecting an observation pattern, which will be described later. Here, as an example, the combination of features to be extracted in the suppression sequence is set to be the same as that to be extracted in the normal sequence.

[0069] As another aspect, the number of features extracted in the suppression sequence may be set to be less than the number of features acquired in the normal sequence. In other words, the suppression sequence may be configured to extract only a part of the features extracted in the normal sequence. For example, the normal sequence extracts five items, namely, peak intensity Pq, peak arrival time Tp, rising judgment time Ta, falling judgment time Tb, and pulse width Tw. On the other hand, the suppression sequence may extract three items, namely, peak arrival time Tp, rising judgment time Ta, and falling judgment time Tb. In addition, the extraction targets in the suppression sequence may be three items, namely, pulse width Tw, rising judgment time Ta, and falling judgment time Tb. By restricting the number of features to be extracted (calculated) in the suppression sequence compared to the normal sequence, it is possible to reduce calculation resources (time, memory, etc.).

[0070] 10 illustrates a procedure in which the normal sequence is performed first and then the suppression sequence is performed, but the order of execution may be reversed. It may also be configured to perform the suppression sequence first and then the normal sequence. The execution interval between the normal light receiving / emitting process and the suppression light receiving / emitting process is set to a sufficiently small value, such as 1 millisecond or 10 milliseconds, so as to reduce the influence of changes in the surrounding environment. The execution interval between the normal light receiving / emitting process and the suppression light receiving / emitting process may be set to be longer than the response waiting time, which is the time for waiting for a response from the light receiving array 5.

[0071] Step S105 is a step of determining an observation pattern of the light receiving pulse to be processed for each pixel based on the pulse information observed in the normal light receiving and emitting process and the pulse information observed in the suppressed light receiving and emitting process. The observation patterns are divided into three types, for example, (A) normal, (B) multiple reflection light combination, and (C) scattered light combination. (A) normal corresponds to a case where the target pulse is not combined with unnecessary reflected light. (B) multiple reflection light combination corresponds to a case where the target pulse is combined with multiple reflection light. (C) scattered light combination corresponds to a case where the target pulse is combined with scattered light from a nearby object. Step S105 corresponds to a step of identifying whether or not the light receiving pulse observed in the normal light receiving and emitting process is affected by unnecessary reflected light, and if so, the type of the affected light, from the pulse information observed in the normal / suppressed light receiving and emitting process. In one aspect, step S105 corresponds to determining whether or not the light receiving pulse is affected by scattered light from a nearby object.

[0072] Step S106 is a step of calculating the distance using an arithmetic expression corresponding to the observation pattern selected in step S105. The arithmetic expression for each observation pattern is registered in advance. The arithmetic expression for each observation pattern is individually designed to suit whether or not unwanted reflected light is superimposed and the type of unwanted reflected light that is superimposed. The various arithmetic expressions may use different features, etc. However, depending on the features used in the calculation, the arithmetic expression when the observation pattern is determined to be normal and the arithmetic expression when it is determined that multiple reflected light is combined may be integrated (common). Details of the arithmetic expression for each observation pattern will be described separately later.

[0073] The above-mentioned steps S102, S104, S105, and S106 are executed for each pixel. The processes of steps S105 to S106 are performed on the received light pulse / peak detected at a common position in the same pixel in both the normal light reception / emission process and the suppressed light reception / emission process. The distance calculation unit F4 can execute the above process for each received light pulse observed in the normal light reception / emission process. In this disclosure, the received light pulse to be processed is also referred to as the target pulse.

[0074] The process from step S105 onwards can be performed on the received light pulse / peak observed until the time elapsed from the irradiation of the sensing light becomes the vicinity time, which is the time corresponding to the vicinity distance. The vicinity time can be set to, for example, a value obtained by dividing twice the vicinity distance by the speed of light. The time period from the irradiation of the sensing light to the vicinity time is also referred to as the vicinity time period.

[0075] In addition, when a peak observed in the vicinity time zone as a result of the normal light reception / emission process is not observed in the suppressed light reception / emission process, the control unit 2 may regard the peak as noise derived from unnecessary reflected light and discard it. This is because, if a target exists in the vicinity area, a peak corresponding to the target is likely to be detected at a similar position even at the suppression level. A peak observed in the vicinity time zone as a result of the normal light reception / emission process and not observed in the suppressed light reception / emission process can be regarded as a peak derived from unnecessary reflected light. It is assumed that reflected light from a target existing in the distance can be observed in the normal light reception / emission process due to the relationship of irradiation intensity, but cannot be observed in the suppressed light reception / emission process. Therefore, it is preferable that the control unit 2 is configured not to determine that a received light pulse observed outside the vicinity time zone as a result of the normal light reception / emission process is noise derived from unnecessary reflected light even if a received light pulse cannot be detected at the corresponding position in the suppressed light reception / emission process. A received light pulse observed outside the vicinity time zone as a result of the normal light reception / emission process may be determined to be noise using another algorithm.

[0076] <Example of calculation formula for each observation pattern (1)> Here, the calculation formula for each observation pattern will be described. Fig. 11 is a diagram summarizing an example of the calculation formula applied to each observation pattern as one embodiment. In this disclosure, the calculation method for the normal pattern is also called the normal method, the calculation method for the multiple reflection light combination pattern is also called the multiple reflection light compatible method, and the calculation method for the scattered light combination pattern is also called the scattered light compatible method. Each calculation method is set to correspond to the cases where there is no influence of unnecessary reflected light, where there is influence of multiple reflection light, and where there is influence of scattered light, respectively.

[0077] 11 is a calculation formula used for the normal pattern and the multiple reflection light combination pattern, and formula 1c is a calculation formula used for the scattered light combination pattern. Formula 1a: L = C / 2 × Ta - δa Formula 1c: L=C / 2×Tb-δb According to the formula 1a applied to the normal pattern and the multiple reflection light coupling pattern, the value obtained by multiplying the rising judgment time (Ta) observed in the normal receiving and emitting process by half the speed of light (C / 2) and subtracting a predetermined rising offset value (δa) from the result is adopted as the distance value (L). The rising offset value (δa) used in the formula 1a is a parameter for offsetting (correcting) the response delay of the circuit. The rising offset value (δa) can be designed appropriately. In addition, in the scattered light corresponding method, as shown in the formula 1c, the value obtained by multiplying the falling judgment time (Tb) observed in the normal receiving and emitting process by half the speed of light (C / 2) and subtracting a predetermined falling offset value (δb) from the result is adopted as the distance value (L). The falling offset value (δb) is also a parameter for offsetting the response delay of the circuit. The falling offset value is designed to be larger than the rising offset value so as to compensate for the error component derived from the time difference between the rising and falling of the receiving light pulse.

[0078] As mentioned above, when the target reflected light is affected by multiple reflected light, the trailing edge point and other information originate from the multiple reflected light and may be incorrect. Therefore, when the target reflected light is affected by multiple reflected light, the distance is calculated based on the rising edge point as shown in formula 1a. On the other hand, when scattered light is combined, the rising section is due to the scattered light component, so the distance is calculated based on the trailing edge point / upper limit departure point. In this way, by adopting a calculation formula according to the type of unwanted reflected light, it is possible to improve the accuracy of the distance.

[0079] <Example of calculation formula for each observation pattern (2)> As another embodiment, the control unit 2 may employ formulas 2a to 2c as the arithmetic formula for each observation pattern. Fig. 12 is a diagram summarizing the arithmetic formula for each observation pattern. Formula 2a is the arithmetic formula for a normal pattern. Formula 2b is the arithmetic formula for a multiple reflection light combination pattern. Formula 2c is the arithmetic formula for a scattered light combination pattern. Formula 2a: L=C / 2×Ta-α1×Pq-β×Tw-δa Equation 2b: L = C / 2 × Ta-α2 × Pq-δa Formula 2c: L=C / 2×Tb-α3×Pq-δb The rising judgment time Ta, falling judgment time Tb, pulse width Tw, and peak intensity Pq used in each of the formulas 2a to 2c can adopt values ​​observed in normal light receiving and emitting processing. α1, α2, and α3 are coefficients for performing correction according to the intensity of the received light pulse (i.e., peak intensity Pq). α1, α2, and α3 can be set to different values. β is a coefficient for performing correction according to the width of the received light pulse (i.e., pulse width Tw). The rising offset value (δa) used in the formulas 2a and 2b may be the same, or different values ​​may be applied.

[0080] The peak intensity Pq and the pulse width Tw indicate the shape of the received light pulse, in other words, the rising speed and falling speed. It has been experimentally found that there is a correlation between the intensity of the target reflected light and the deviation of the distance calculation value. In addition, when the received light intensity is saturated, the relationship between the received light intensity and the true intensity of the target reflected light becomes unclear, but it has been experimentally found that there is a correlation between the intensity of the target reflected light and the pulse width. In other words, the pulse width can function as a parameter that indirectly indicates the true intensity of the target reflected light. Therefore, if the observed received light pulse is not the target reflected light superimposed with unnecessary reflected light, the distance measurement accuracy can be improved by introducing a correction value using the pulse width Tw. However, if the target pulse is affected by multiple reflected light or scattered light from a nearby object, the pulse width Tw will be a value that deviates from the width of the target pulse. If the target pulse is affected by multiple reflected light or scattered light, there is a concern that introducing a correction term using the pulse width Tw may actually deteriorate the distance measurement accuracy.

[0081] The above formulas 2a to 2c were created based on the above concerns, and in this method, the distance correction method is switched depending on the observation pattern. With this configuration, it is expected that the distance measurement accuracy will be further improved. In this disclosure, the combination can also be rephrased as superposition.

[0082] <Example of calculation formula for each observation pattern (3)> As another embodiment, the control unit 2 may employ formulas 3a1, 3a2, 3c1, and 3c2 as the calculation formulas for each observation pattern, as shown in FIG. 13. Formula 3a1 is a calculation formula applied when the normal peak intensity Pq1, which is the peak intensity Pq observed in the normal light receiving and emitting process, is less than a predetermined calculation material switching threshold Thx in the normal pattern and the multiple reflection light combination pattern. Formula 3a2 is a calculation formula applied when the normal peak intensity Pq1 is equal to or greater than the calculation material switching threshold Thx in the normal pattern and the multiple reflection light combination pattern. Formula 3c1 is a calculation formula applied when the normal peak intensity Pq1 is less than the calculation material switching threshold Thx in the scattered light combination pattern. Formula 3c2 is a calculation formula applied when the normal peak intensity Pq is equal to or greater than the calculation material switching threshold Thx in the scattered light combination pattern.

[0083] The calculation material switching threshold Thx can be, for example, the measurement upper limit value Pmx. The calculation material switching threshold Thx may be, for example, 90% of the measurement upper limit value Pmx. Formula 3a1: L=C / 2×Ta1-δa1 Formula 3a2: L=C / 2×Ta2-δa2 Formula 3c1: L=C / 2×Tb1-δb1 Formula 3c2: L=C / 2×Tb2-δb2 As described above, Ta1 in formula 3a1 is the normal rise time. Ta2 in formula 3a2 is the suppressed rise time. δa1 in formula 3a1 and δa2 in formula 3a2 are both rise offset values, and are parameters for offsetting errors due to delay times required for rise. Different predetermined values ​​can be set for δa1 and δa2.

[0084] Furthermore, Tb1 included in formula 3c1 is the normal fall time, and Tb2 included in formula 3c2 is the suppressed fall time. δb1 included in formula 3c1 and δb2 included in formula 3c2 are both rise offset values, and are parameters for offsetting errors due to delay times required for rise, etc. Different predetermined values ​​can be set for δb1 and δb2.

[0085] The developers of the present disclosure have found that distance accuracy may deteriorate when the light receiving intensity becomes saturated during repeated testing and simulation. This is because when saturation occurs, the waveform of the target reflected light cannot be sampled correctly. For example, when the light receiving intensity is saturated, the true peak value may become unclear. The configuration using the above formula 3a1 etc. was created based on the above knowledge, and when the light receiving intensity obtained by the normal light receiving and emitting process is equal to or greater than the calculation material switching threshold Thx, the control unit 2 calculates the distance based on the data of the suppressed light receiving and emitting process. In other words, when saturation occurs in the normal light receiving and emitting process, the result of the suppressed light receiving and emitting process, which is relatively less likely to become saturated, is used. With this configuration, it is expected that the distance measurement accuracy will be further improved.

[0086] In addition, although the above describes a mode in which distance calculation is performed using the rising edge determination time Ta / falling edge determination time Tb as the main variables, the distance may be calculated using the peak arrival time Tp. The offset value such as δa may be changed according to the feature quantity used in the calculation process. In addition, the correction process of the distance value using the peak intensity Pq or the pulse width Tw can also be applied to the above-mentioned formulas 3a to 3c.

[0087] <Method of distinguishing observation patterns (1)> Here, a method for discriminating an observation pattern will be described with reference to Fig. 14. Fig. 14 is a flowchart showing an example of the observation pattern discrimination process. The observation pattern discrimination process is executed as step S105 described above. Here, as an example, the observation pattern discrimination process includes steps S201 to S205. The processes of steps S201 to S205 are executed for each pixel. For convenience, a pixel that is the target of the process is also referred to as a target pixel.

[0088] Step S201 is a step for determining whether or not the received light pulse observed in the normal receiving and emitting process may be combined with a component derived from unwanted reflected light in the target pulse. For convenience, the received light pulse in which the component derived from unwanted reflected light is combined with the target pulse is also referred to as an unwanted reflected light combined pulse. In addition, the process for determining whether or not the received light pulse is an unwanted reflected light combined pulse, such as step S201 and steps S301 and S401 described later, is also referred to as an unwanted reflected light combination determination process.

[0089] In step S201, for example, the distance calculation unit F4 determines whether the normal pulse width Tw1 is less than a predetermined pulse width threshold Thw. If the target reflected light is combined with unwanted reflected light, the normal pulse width Tw1 may be longer than a predetermined value. Step S201 corresponds to a step of determining whether or not the target reflected light is affected by unwanted reflected light from the viewpoint of pulse width. The pulse width threshold Thw is set to a value according to the pulse width of the irradiated light. For example, the pulse width threshold Thw is set to 0.8 times, 1.0 times, 1.2 times, etc., the pulse width of the irradiated light.

[0090] If the normal pulse width Tw1 is less than the pulse width threshold Thw, the process proceeds to step S202, where the observed pattern is determined to be a normal pattern. Step S202 corresponds to a step of determining that the observed received light pulse is a target pulse that is not affected by unwanted reflected light. On the other hand, if the normal pulse width Tw1 is equal to or greater than the pulse width threshold Thw, step S203 is executed.

[0091] Step S203 corresponds to a step of identifying the type of unwanted reflected light combined (superimposed) with the target pulse based on the context of the normal peak time Tp1 and the suppression peak time Tp2. Note that, as a premise of step S203, the peak detection unit 8 is configured to adopt an intermediate time Tpc located midway between the upper limit arrival time Tpa and the upper limit departure time Tpb as the peak arrival time Tp when the received light intensity reaches the measurement upper limit value Pmx.

[0092] 15 and 16 are diagrams for explaining the technical concept of step S203. The solid line graphs in the lower graphs of FIG. 15 and FIG. 16 show the transition of the output level by the normal light receiving and emitting process, and the dashed line graphs show the transition of the output level by the suppressed light receiving and emitting process. If the scattered light from the nearby object is combined with the reflected light from the target, as shown in FIG. 15, the suppressed peak time Tp2 is located behind the normal peak time Tp1. This is because, in the normal light receiving and emitting process, the received light intensity is saturated even for the scattered light component from the nearby object, and the normal peak time Tp1 is calculated as the midpoint of the saturation period, that is, a value that is before the true peak. Therefore, the fact that the value obtained by subtracting the normal peak time Tp1 from the suppressed peak time Tp2 is positive suggests that the unnecessary reflected light (hereinafter, the combined noise) combined with the reflected light from the target may be scattered light from the nearby object.

[0093] Furthermore, if multiple reflected light is combined with the target reflected light, the suppression peak time Tp2 is located earlier than the normal peak time Tp1, as shown in Fig. 16. This is because the normal peak time Tp1 is located in the middle of the saturation period and is calculated to be later than the true peak. Therefore, the fact that the value obtained by subtracting the normal peak time Tp1 from the suppression peak time Tp2 is negative suggests that the combined noise may be multiple reflected light.

[0094] Step S203 was created with the above tendency in mind, and if the peak time difference ΔTp (=Tp2-Tp1) is less than a predetermined peak time difference threshold Thdp, the combined noise is determined to be multiple reflected light. In other words, if the peak time difference ΔTp is less than the peak time difference threshold Thdp, the process proceeds to step S204, and the observed pattern is determined to be a multiple reflected light combined pattern. The peak time difference ΔTp is a value obtained by subtracting the normal peak time Tp1 from the suppression peak time Tp2.

[0095] On the other hand, if the peak time difference ΔTp is equal to or greater than the peak time difference threshold Thdp, the coupling noise is deemed to be nearby object scattered light, and the observed pattern is determined to be a scattered light coupling pattern (step S205). The peak time difference threshold Thdp used in step S203 may be 0 or 0.5 nanoseconds. It may also be dynamically determined according to the length of the saturation period obtained by subtracting the upper limit arrival time Tpa from the upper limit departure time Tpb observed in the normal light receiving and emitting process. For example, the peak time difference threshold Thdp may be set to a value equivalent to 1% or 10% of the saturation time.

[0096] <Method of distinguishing observation patterns (2)> Here, another example of the observation pattern discrimination method will be described with reference to Fig. 17. Fig. 17 is also a flowchart showing an example of the observation pattern discrimination process executed as the above-mentioned step S105. The observation pattern discrimination process shown in Fig. 17 includes steps S301 to S305.

[0097] Step S301 corresponds to a step of determining whether the target reflected light is combined with the unwanted reflected light based on the pulse width change amount ΔTw, which is the change amount (difference) between the normal pulse width Tw1 and the suppression pulse width Tw2. The pulse width change amount ΔTw is a value obtained by subtracting the suppression pulse width Tw2 from the normal pulse width Tw1.

[0098] If the target reflected light is not combined with the unwanted reflected light, the difference between the normal pulse width Tw1 and the suppression pulse width Tw2 is expected to be equal to or less than a predetermined value. On the other hand, if the target reflected light is combined with the unwanted reflected light, the normal pulse width Tw1 may be longer than the suppression pulse width Tw2 by the amount of the combined noise. Alternatively, the suppression pulse width Tw2 is likely to be the width of a component purely derived from the target reflected light, and may be smaller than the normal pulse width Tw1. In other words, the pulse width change amount ΔTw being equal to or greater than a predetermined value suggests that the target reflected light is affected by the unwanted reflected light.

[0099] Step S301 of the present disclosure is created based on the above idea, and if the pulse width change amount ΔTw is less than a predetermined width difference threshold Thdw, the process proceeds to step S302, where the observed pattern is determined to be a normal pattern. Step S302 corresponds to a step of regarding the observed received light pulse as a target pulse that is not affected by unnecessary reflected light.

[0100] On the other hand, if the pulse width change amount ΔTw is equal to or larger than the predetermined width difference threshold Thdw, step S303 is executed. The processes of steps S303 to S305 are similar to the above-mentioned steps S203 to S205, and therefore a description thereof will be omitted. The specific value of the width difference threshold Thdw used in the determination process of step S301 can be designed as appropriate. The width difference threshold Thdw may be dynamically determined according to the normal pulse width Tw1 or the suppression pulse width Tw2. The width difference threshold Thdw may be a value obtained by multiplying the normal pulse width Tw1 by a predetermined coefficient (for example, 0.2).

[0101] <Method of distinguishing observation patterns (3)> Here, another example of the observation pattern discrimination method will be described with reference to Fig. 18. Fig. 18 is a flowchart showing an example of the observation pattern discrimination process executed as the above-mentioned step S105. The observation pattern discrimination process shown in Fig. 18 includes steps S401 to S405.

[0102] Step S401 is a determination step similar to step S201 described above. If the normal pulse width Tw1 is less than the pulse width threshold Thw, the process proceeds to step S402, where the observed pattern is determined to be a normal pattern. On the other hand, if the normal pulse width Tw1 is equal to or greater than the pulse width threshold Thw, step S403 is executed.

[0103] Step S403 corresponds to a step of identifying the type of coupled noise based on a rise time difference ΔTa, which is the change (difference) between the normal rise time Ta1 and the suppression rise time Ta2. The rise time difference ΔTa is a value obtained by subtracting the normal rise time Ta1 from the suppression rise time Ta2.

[0104] 19 and 20 are diagrams for explaining the technical concept of step S403. The solid line graphs in the lower graphs of Fig. 19 and Fig. 20 show the transition of the output level of the adder 7 by the normal light receiving / emitting process, and the dashed line graphs show the transition of the output level of the adder 7 by the suppressed light receiving / emitting process. If multiple reflected light is combined with the target reflected light, as shown in Fig. 19, the difference between the suppressed rise time Ta2 and the normal rise time Ta1 will be a relatively small value. This is because the multiple reflected light is not combined with the front of the target reflected light due to the relationship of the optical path length. In other words, if the combined noise is multiple reflected light, the rise section originates from the target reflected light in both the normal light receiving / emitting process and the suppressed light receiving / emitting process, so the difference between the normal rise time Ta1 and the suppressed rise time Ta2 will be small.

[0105] On the other hand, when the target reflected light is combined with a nearby object scattered light component, the suppression rise time Ta2 can be longer than the normal rise time Ta1 by the amount corresponding to the nearby object scattered light, as shown in FIG. 20. This is because when the combined noise is nearby object scattered light, the rise section in the normal light receiving and emitting process is derived from nearby object scattered light as combined noise. When the combined noise is nearby object scattered light, the difference between the normal rise time Ta1 and the suppression rise time Ta2 is relatively large compared to when the combined noise is multiple reflected light. In other words, a rise time difference ΔTa of a predetermined value or more suggests that there is an influence of nearby object scattered light.

[0106] Step S403 of the present disclosure is created based on the above idea, and if the rise time difference ΔTa is less than a predetermined rise time difference threshold Thda, the process proceeds to step S404, where the observed pattern is determined to be a multiple reflection light combination pattern. Step S404 corresponds to a step of determining that the observed received light pulse is affected by multiple reflection light.

[0107] On the other hand, if the rise time difference ΔTa is equal to or greater than the rise time difference threshold Thda, the process proceeds to step S405, where the observed pattern is determined to be a scattered light coupling pattern. Step S405 corresponds to a step of determining that the coupling noise is nearby object scattered light. The rise time difference threshold Thda used in step S403 can be a constant value, such as 0.5 nanoseconds or 1.0 nanoseconds. The rise time difference threshold Thda may also be dynamically determined according to the suppression peak intensity Pq2, which is the peak intensity Pq observed in the suppression light receiving and emitting process, or the rise speed observed in the normal light receiving and emitting process. For example, the rise time difference threshold Thda may be applied with a larger value as the suppression peak intensity Pq2 is smaller.

[0108] In one aspect, the above configuration corresponds to a configuration in which the feature quantity used in the distance calculation is switched depending on whether the time difference between the normal rise time Ta1 and the suppression rise time Ta2 is less than a predetermined value. That is, when the time difference between the normal rise time Ta1 and the suppression rise time Ta2 is less than a predetermined value, it is presumed that the light is combined with the multiple reflected light or not combined with the unnecessary reflected light, and the distance is calculated based on the rise determination time Ta. On the other hand, when the time difference between the normal rise time Ta1 and the suppression rise time Ta2 is equal to or greater than a predetermined value, it is presumed that the light is combined with the nearby object scattered light, and the distance is calculated based on the fall determination time Tb. The rise determination time Ta / fall determination time Tb used in the calculation may be the observation value in the normal light receiving / emitting process or the observation value in the suppression light receiving / emitting process. The control unit 2 may switch which observation value in the light receiving / emitting process is used based on the peak intensity Pq observed in the normal light receiving / emitting process as described in FIG. 13.

[0109] The rise time difference ΔTa may be a value obtained by subtracting the suppression rise time Ta2 from the normal rise time Ta1, or may be an absolute value of the difference. The rise time difference threshold Thda may be adjusted according to the definition of the rise time difference ΔTa.

[0110] In addition, although the above describes a configuration for determining the type of superimposed noise based on the rise time difference ΔTa, the fall time difference can also be used as a parameter for distinguishing the type of superimposed noise. The fall time difference is the difference between the normal fall time, which is the fall time Tb observed in the normal light reception / emission process, and the suppressed fall time, which is the fall time Tb observed in the suppressed light reception / emission process. When the superimposed noise is multiple reflected light, the fall time difference can be larger than when the superimposed noise is nearby object scattered light. Therefore, the control unit 2 can determine that the superimposed noise is multiple reflected light based on the fact that the fall time difference is equal to or greater than a predetermined value.

[0111] <About the effects, etc.> In the optical distance measuring device 1 described above, the control unit 2 first uses the normal pulse width Tw1 to determine whether or not the received light pulse observed in the normal light receiving and emitting process is combined with unwanted reflected light. Note that since the pulse width change amount ΔTw is also a parameter determined by the normal pulse width Tw1, the mode in which the control unit 2 performs the above determination based on the pulse width change amount ΔTw is also included in the configuration in which the normal pulse width Tw1 is used to determine whether or not the received light pulse is combined with unwanted reflected light.

[0112] The normal pulse width Tw1 is a parameter that can be extracted by signal analysis, and no special circuit or the like is required for parameter extraction. Therefore, according to the above configuration, it is possible to determine whether or not the received light pulse is affected by unwanted reflected light without introducing any special configuration.

[0113] In addition, the normal pulse width Tw1 may vary depending on the reflection characteristics of the target or the distance to the target. In light of such circumstances, it is practically difficult to determine a pulse width threshold Thw that is suitable for all scenes. In addition, in a configuration in which the unwanted reflected light coupling determination is performed by comparing the normal pulse width Tw1 with the pulse width threshold Thw, it may occur that a pulse that is actually an unwanted reflected light coupling pulse is not considered to be an unwanted reflected light coupling pulse depending on the situation. In response to such issues, a configuration in which the unwanted reflected light coupling determination process is performed using the pulse width change amount ΔTw can suppress erroneous determinations resulting from the distance or reflection characteristics of the target.

[0114] Furthermore, the control unit 2 identifies the type of unwanted reflected light combined with the target reflected light based on the pulse information obtained by the normal light receiving and emitting process and the pulse information obtained by the suppressed light receiving and emitting process. Specifically, the control unit 2 determines whether the unwanted reflected light combined with the target reflected light is scattered light from a nearby object using the peak time difference ΔTp or the rise time difference ΔTa. If the control unit 2 determines that the unwanted reflected light combined with the target reflected light is scattered light from a nearby object, it calculates a distance value using an arithmetic expression / feature value different from that of the normal pattern.

[0115] For example, in the normal pattern, the rise judgment time Ta is used to calculate the distance, whereas in the scattered light combination pattern, the fall judgment time Tb is used to calculate the distance. Also, for example, in the normal pattern, correction using the pulse width Tw is performed, whereas in the scattered light combination pattern, correction using the pulse width Tw is not performed. With this configuration, it is possible to reduce the risk of calculating the distance to the target as shorter than the actual distance due to the nearby object scattered light component.

[0116] Furthermore, the control unit 2 judges whether the unwanted reflected light combined with the target reflected light is multiple reflected light or not by comparing the pulse information obtained by the normal light receiving and emitting process with the pulse information obtained by the suppressed light receiving and emitting process. If the unwanted reflected light combined with the target reflected light is judged to be multiple reflected light, the normal pulse width Tw1 is not used for distance calculation. This configuration can reduce the risk of calculating the distance to the target as a value longer than the actual distance due to multiple reflected light components.

[0117] In addition, as an example, in the above configuration, when the normal peak intensity Pq1 is less than a predetermined value, distance calculation is performed using the feature obtained by the normal light receiving and emitting process, whereas when the normal peak intensity Pq1 is equal to or greater than the predetermined value, distance calculation is performed using the feature obtained by the suppressed light receiving and emitting process. With this configuration, distance calculation is performed using the feature observed under conditions that are relatively unlikely to cause saturation. The longer the saturation period, the more the distance measurement accuracy may deteriorate. With the above configuration, it is expected that the distance measurement accuracy can be further improved.

[0118] In addition, as another assumed configuration for suppressing erroneous calculation of distance due to the influence of unwanted reflected light, a configuration in which the output intensity of the sensing light at the normal level is sufficiently weakened, in other words, a configuration in which the receiving and emitting process at the normal level is not performed and only the suppressed receiving and emitting process is performed is also considered. This assumed configuration can certainly reduce the risk of saturation of the pixel value, and is expected to be able to suppress the influence of the unwanted reflected wave. However, if the set value of the normal level is made small enough to be able to determine whether or not the unwanted reflected light is combined, the distance measurement range will be shortened. In response to the problem of such an assumed configuration, according to the above embodiment, it is possible to improve the accuracy of the distance value for each pixel while maintaining the distance measurement range.

[0119] Although the embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-mentioned embodiment, and various modified examples described below are also included in the technical scope of the present disclosure, and further, various modifications other than those described below can be implemented without departing from the gist of the present disclosure. For example, the following various supplements and modified examples can be implemented in appropriate combinations as long as no technical contradiction occurs. Note that the same reference numerals are used for components having the same functions as the components described above, and their description may be omitted. In addition, when only a part of the configuration is mentioned, the above description can be applied to the other parts.

[0120] <About the device configuration> In the above, the suppressed light reception / emission process is realized by suppressing the intensity of the irradiated light. However, the suppressed light reception / emission process may be realized by lowering the detection sensitivity of the light receiving system. For example, as shown in FIG. 21, the optical distance measuring device 1 may include a transmittance adjustment panel 11 arranged in front of the light receiving array 5 and configured to be able to switch the transmittance. A liquid crystal panel can be used as the transmittance adjustment panel 11. In this case, the level adjustment unit F3 dynamically switches the transmittance of the transmittance adjustment panel 11 between a predetermined normal level and a suppressed level to realize the normal light reception / emission process and the suppressed light reception / emission process. With this configuration, it is not necessary to adjust the irradiation intensity. Of course, the optical distance measuring device 1 may be configured to realize the normal light reception / emission process and the suppressed light reception / emission process by performing the adjustment of the irradiation intensity and the adjustment of the light receiving sensitivity (detection sensitivity) in parallel.

[0121] <Control unit behavior> The optical distance measuring device 1 is usually designed so that the internally scattered light does not reach the light receiving array 5 as much as possible. Therefore, the cause of the nearby object scattered light is essentially dirt (sand, soil, water droplets, snow, etc.) attached to the outside of the irradiation window 91. These deposits 10 are accidentally attached and can be removed by cleaning. Therefore, when the control unit 2 determines that the superimposed noise is nearby object scattered light, it may be configured to execute a cleaning process for cleaning the surface of the irradiation window 91. The cleaning process may include some or all of the following: spraying a cleaning liquid, driving a wiper, and spraying compressed air.

[0122] Moreover, receiving nearby object scattered light corresponds to losing a part of the irradiated light. If the intensity of the irradiated light is lost, there is a concern that the detection distance will decrease. In view of this, the control unit 2 may be configured to increase the irradiation intensity by a predetermined amount when it is determined that there is an effect of nearby object scattered light. With this configuration, it is possible to reduce the risk of the detection distance decreasing even if an attachment 10 is attached to the irradiation window 91.

[0123] When the control unit 2 determines that the vehicle is affected by the nearby object scattered light, the control unit 2 may output an alert signal to the driving assistance ECU or the like, indicating that the detection performance is impaired or that the vehicle is not operating normally. According to this configuration, the driving assistance ECU can respond by limiting the driving speed or transferring driving authority to the driver based on the input of the alert signal. The alert signal may be a signal instructing the vehicle to stop or hand over.

[0124] Furthermore, when the control unit 2 determines that the system is affected by nearby object scattered light, it may display an image on the in-vehicle display indicating that the detection performance is impaired or that the system is not operating normally, or may output the above message as sound from the speaker. This configuration makes it easier for the occupant to recognize that the outer surface of the irradiation window 91 needs to be cleaned. This in turn makes it easier to quickly take measures such as stopping the vehicle for cleaning. In other words, in the automatic driving device, it becomes easier to properly carry out maintenance to ensure that the system functions normally.

[0125] The notification of the influence of nearby object scattered light may be sent not only to the occupants but also to an operator outside the vehicle, such as a center. When it is determined that the vehicle is influenced by nearby object scattered light, the control unit 2 may be configured to wirelessly transmit an alert signal to an external server / center / surrounding vehicles in cooperation with an in-vehicle communication device.

[0126] The control unit 2 may be configured to transmit an alert signal to another ECU, an external server / center, or a surrounding vehicle when multiple reflected light is detected. The content of the alert signal output when multiple reflected light is detected may be the same as that when nearby object scattered light is detected, or may be different. The content of the alert signal output when multiple reflected light is detected may be a signal indicating that distance accuracy / reliability has decreased.

[0127] Furthermore, the control unit 2 may be configured to output an image or a voice message indicating that the distance accuracy / reliability has decreased when multiple reflected light is detected. This configuration makes it easier for the occupant to recognize the operating state of the optical distance measuring device 1. An example of a case where multiple reflected light is received is when a highly reflective object is present relatively nearby. The above case where multiple reflected light is detected can be rephrased as a case where a highly reflective object is present within a predetermined distance from the optical distance measuring device 1. The highly reflective object is a retroreflective object.

[0128] Furthermore, when an external device detects an object defined as a highly reflective object in the vicinity of the optical distance measuring device 1 by analyzing an image from an in-vehicle camera or the like, a signal indicating the presence of the highly reflective object may be input from the external device to the optical distance measuring device 1. The optical distance measuring device 1 may dynamically change the discrimination formula for the observation pattern based on the above input signal from the outside. When the optical distance measuring device 1 is notified of the presence of a highly reflective object from the outside, it may change the setting values ​​of various thresholds related to discrimination of the observation pattern so as to make it easier to determine that multiple reflected light is being received.

[0129] <Additional remarks> The device, system, and method thereof described in the present disclosure may be realized by a dedicated computer that configures a processor programmed to execute one or more functions embodied by a computer program. The device and method described in the present disclosure may also be realized by a dedicated hardware logic circuit. Furthermore, the device and method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor that executes a computer program and one or more hardware logic circuits. For example, some or all of the functions of the optical distance measuring device 1 may be realized as hardware. The embodiment in which a certain function is realized as hardware includes an embodiment in which it is realized using one or more ICs. As the processor (computation core), a CPU, an MPU, a GPU, a DFP (Data Flow Processor), or the like can be adopted. Furthermore, some or all of the functions of the optical distance measuring device 1 may be realized by combining multiple types of computation processing devices. Some or all of the functions of the optical distance measuring device 1 may be realized by using a system-on-chip (SoC), an FPGA, an ASIC, or the like. FPGA is an abbreviation for Field-Programmable Gate Array. ASIC stands for Application Specific Integrated Circuit.

[0130] The computer program may be stored as instructions executed by a computer on a computer-readable non-transitive tangible storage medium. The program may be stored on a hard disk drive (HDD), a solid state drive (SSD), a flash memory, or the like. [Explanation of symbols]

[0131] 1 Optical distance measuring device, 2 Control unit, 4 Irradiation unit, 5 Light receiving array, 5s Light receiving cell (photodetector), 6 Response judger, 7 Adder, 8 Peak detection unit, 9 Housing, 91 Irradiation window, 10 Adherent matter, F2 Pulse information acquisition unit, F3 Level adjustment unit, F4 Distance calculation unit, Tw Pulse width, Tw1 Normal pulse width, Tw2 Suppression pulse width, Ta Rising judgement time, Ta1 Normal rising time, Ta2 Suppression rising time, Tb Falling judgement time, Tp Peak arrival time, Tp1 Normal peak time, Tp2 Suppression peak time

Claims

1. An optical distance measuring device that detects a distance to a target using a round-trip time of light to the target, an irradiation unit (4) that irradiates sensing light, which is light having a predetermined wavelength, in a predetermined direction toward a detection target; A plurality of photodetectors (5s) arranged in a matrix and responsive to the sensing light; a level adjustment unit (F3) that switches the irradiation intensity of the sensing light output from the irradiation unit or the detection sensitivity of the plurality of photodetectors from a predetermined normal level to a suppression level that is a predetermined amount lower than the normal level; a peak detection unit (8) for detecting a light receiving pulse and its peak corresponding to a reflected light, which is a light that is returned by being reflected from an object, based on time series data of the number of responses of the light detector; A pulse information acquisition unit (F2) configured to acquire, as pulse information, a data set indicating a predetermined feature amount related to the received light pulse detected by the peak detection unit, and to acquire normal pulse information which is the pulse information when the normal level is applied, and suppression pulse information which is the pulse information when the suppression level is applied; a distance calculation unit (F4) that calculates a distance value to the target based on the normal pulse information and the suppression pulse information.

2. 2. The optical distance measuring device according to claim 1, The normal pulse information includes at least a pulse width, The distance calculation unit is determining whether or not the target pulse is a combination of reflected light from the target and unwanted reflected light, based on a value of the pulse width included in the normal pulse information for the target pulse, which is the received light pulse to be processed; An optical distance measuring device configured to change at least one of the calculation formula and the feature value used to calculate the distance value depending on whether the target pulse is a combination of reflected light from the target and the unwanted reflected light.

3. 3. The optical distance measuring device according to claim 2, The distance calculation unit is An optical ranging device configured to determine that the target pulse is a combination of reflected light from the target and the unwanted reflected light based on the pulse width included in the normal pulse information for the target pulse being greater than or equal to a predetermined value.

4. 4. The optical distance measuring device according to claim 2, The suppression pulse information includes a pulse width; The distance calculation unit is An optical ranging device that determines that the target pulse is a combination of reflected light from the target and the unwanted reflected light based on the difference between the pulse width contained in the normal pulse information for the target pulse and the pulse width contained in the suppression pulse information being greater than or equal to a predetermined value.

5. 5. An optical distance measuring device according to claim 2, The distance calculation unit is When it is determined that the target pulse is a combination of the unwanted reflected light and the reflected light from the target, determining the type of the unwanted reflected light by comparing the normal pulse information and the suppression pulse information for the target pulse; The optical distance measuring device is configured to change at least one of an arithmetic expression and a feature amount used to calculate the distance value according to the determined type of the unwanted reflected light.

6. 6. An optical distance measuring device according to claim 5, The normal pulse information and the suppression pulse information each include a peak arrival time (Tp) which is a time from when the sensing light is irradiated to when a peak is observed, The distance calculation unit is An optical ranging device that is configured, when it is determined that the target pulse is a combination of reflected light from the target and unwanted reflected light, to determine the type of combined noise which is the unwanted reflected light by comparing the peak arrival time contained in the normal pulse information for the target pulse with the peak arrival time contained in the suppression pulse information.

7. 7. An optical distance measuring device according to claim 6, The normal pulse information and the suppression pulse information each include, in addition to the peak arrival time, a rising judgment time (Ta) at which the intensity of the received light pulse becomes equal to or greater than a threshold, and a falling judgment time (Tb) indicating the timing at which the intensity of the received light pulse becomes equal to or less than the threshold, The distance calculation unit is determining whether or not the combined noise corresponds to a nearby object scattered light, which is an attachment to an irradiation window or scattered light inside a housing, by comparing the peak arrival time included in the normal pulse information for the target pulse with the peak arrival time included in the suppression pulse information; When it is determined that the combined noise is nearby object scattered light, the distance value is calculated using the falling edge determination time, the optical distance measuring device being configured to calculate the distance value using the rise determination time when it is determined that the combined noise is not light scattered by a nearby object.

8. 6. An optical distance measuring device according to claim 5, The normal pulse information and the suppression pulse information each include a rising edge determination time (Ta) at which the intensity of the received light pulse becomes equal to or greater than a threshold value, The distance calculation unit is An optical ranging device that is configured such that when it is determined that the target pulse is a combination of reflected light from the target and unwanted reflected light, the type of combined noise which is the unwanted reflected light is determined by comparing the rise judgment time contained in the normal pulse information for the target pulse with the rise judgment time contained in the suppression pulse information.

9. 9. An optical distance measuring device according to claim 8, The normal pulse information and the suppression pulse information each include, in addition to the rising judgment time, a falling judgment time (Tb) indicating a timing at which the intensity of the received light pulse becomes equal to or less than the threshold value, The distance calculation unit is determining whether or not the combined noise corresponds to a nearby object scattered light, which is an attachment to an irradiation window or scattered light inside a housing, by comparing the rising judgment time included in the normal pulse information for the target pulse with the rising judgment time included in the suppression pulse information; When it is determined that the combined noise is nearby object scattered light, the distance value is calculated using the falling edge determination time, the optical distance measuring device being configured to calculate the distance value using the rise determination time when it is determined that the combined noise is not light scattered by a nearby object.

10. 5. An optical distance measuring device according to claim 2, The distance calculation unit is When it is determined that the target pulse is a combination of the unwanted reflected light and the reflected light from the target, by comparing the normal pulse information and the suppression pulse information for the target pulse, it is determined whether or not the combined noise, which is the unwanted reflected light combined with the reflected light from the target, corresponds to an attachment on an irradiation window or nearby object scattered light, which is scattered light inside a housing; An optical distance measuring device configured to change at least one of an arithmetic expression and a feature value used to calculate the distance value depending on whether the combined noise is light scattered by a nearby object.

11. 11. An optical distance measuring device according to claim 2, the normal pulse information includes a rising edge determination time indicating a timing at which the intensity of the received light pulse becomes equal to or greater than a threshold value; The distance calculation unit is An optical ranging device configured to calculate the distance value using the rise judgment time contained in the normal pulse information when it is determined that the target pulse is due to reflected light from the target that is not combined with the unwanted reflected light.

12. 12. The optical distance measuring device according to claim 11, The distance calculation unit is When it is determined that the target pulse is due to reflected light from the target that is not combined with the unwanted reflected light, the distance value is determined by performing a correction according to the pulse width on a value obtained by multiplying the rising judgment time by half the speed of light, while An optical distance measuring device configured not to perform correction using the pulse width when it is determined that the target pulse is a combination of reflected light from the target and the unwanted reflected light.

13. 13. An optical distance measuring device according to claim 1, The normal pulse information includes a peak intensity indicating an intensity at a peak, The distance calculation unit is When the peak intensity included in the normal pulse information is equal to or greater than a predetermined value, the distance value is calculated using the suppression pulse information, An optical distance measuring device configured to calculate the distance value using the normal pulse information when the peak intensity contained in the normal pulse information is less than a predetermined value.

14. 2. The optical distance measuring device according to claim 1, The normal pulse information and the suppression pulse information each include a rising edge determination time (Ta) at which the light receiving pulse becomes equal to or greater than a predetermined threshold value, The distance calculation unit is An optical distance measuring device configured to change at least one of the arithmetic equation and the feature value used to calculate the distance value depending on whether the rise time difference, which is the difference between the rise judgment time included in the normal pulse information for a target pulse, which is the received light pulse to be processed, and the rise judgment time included in the suppression pulse information, is less than a predetermined value.

15. 15. An optical distance measuring device according to claim 14, The normal pulse information and the suppression pulse information each include, as a parameter other than the rising judgment time (Ta), at least one of a falling judgment time (Tb) indicating a timing at which the intensity of the received light pulse becomes equal to or less than the threshold value and a peak arrival time (Tp) which is a time from when the sensing light is irradiated to when a peak is observed, The distance calculation unit is When the rise time difference is less than a predetermined value, the rise determination time is used to calculate the distance value, An optical distance measuring device configured to calculate the distance value using a parameter other than the rise determination time when the rise time difference is equal to or greater than the predetermined value.

16. 16. An optical distance measuring device according to claim 1, The distance calculation unit is An optical ranging device configured to determine that if a received light pulse observed within a predetermined time after the sensing light is irradiated at the normal level is not observed when the suppression level is applied, the received light pulse is due to unwanted reflected light.

17. 17. An optical distance measuring device according to claim 1, The distance calculation unit is detecting an object attached to the irradiation window by comparing the normal pulse information with the suppression pulse information; The optical distance measuring device is configured to execute a process for cleaning the irradiation window when an attachment to the irradiation window is detected.

18. 18. An optical distance measuring device according to claim 1, The distance calculation unit is detecting an object attached to the irradiation window by comparing the normal pulse information with the suppression pulse information; The optical distance measuring device is configured to, when detecting an object adhering to the irradiation window, execute a process to notify an occupant, an operator outside the vehicle, or another device that an object is attached to the irradiation window.

19. 19. An optical distance measuring device according to any one of claims 1 to 18, The distance calculation unit is determining whether or not a situation in which multiple reflected light is likely to be received is present by comparing the normal pulse information with the suppression pulse information; The optical ranging device is configured to execute a process to notify an occupant, an operator outside the vehicle, or another device that the ranging accuracy to the target has decreased when it is determined that the situation is such that the multiple reflected light is likely to be received.

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