Optical distance measuring device

Abstract

The optical distance measuring device (200) of the present invention comprises: a light emitting unit (40) emitting outgoing light (DL); a light receiving unit (60) having a light receiving pixel (66) for receiving incident light and outputting a detection signal corresponding to the light intensity of the incident light received by the light receiving pixel; and a control device (100) acquiring the detection signal from the light receiving unit and using the detection signal to detect the distance to the object, wherein the light receiving unit receives reflected light (RL) corresponding to the outgoing light reflected by the object (OB) as incident light, and the detection signal corresponds to the light intensity of the reflected light. When a first object (OB1) and a second object (OB2) are detected and it is determined that the second object is a pseudo object corresponding to the first object, the control device can remove the detection result of the second object, wherein the second object is located at a distance (D2) N times (N is a natural number greater than 2) the distance (D1) from the first object on an extension line of a straight line (OL) connecting the optical distance measuring device and the first object.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on Japanese application No. 2020-072685 filed on April 15, 2020, and the contents thereof are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to an optical distance measuring device. Background Art

[0004] There is known a target object detection system that irradiates a preset detection range with laser light and detects the target object by receiving reflected light from the target object using a plurality of light receiving elements (for example, Japanese Patent Application Laid-Open No. 2014-098635).

[0005] In such a target object detection system, if the intensity of reflected light from the target object increases, the reflected light from the target object is further reflected toward the target object by the surface of the light receiving element, and the target object may not be detected correctly. Summary of the invention

[0006] The present disclosure has been made to solve at least a part of the above-mentioned technical problems and can be implemented as the following aspects or application examples.

[0007] According to one embodiment of the present disclosure, a light ranging device is provided. The light ranging device comprises: a light emitting unit that emits emitted light; a window unit that transmits the emitted light; a light receiving unit that has light receiving pixels for receiving incident light and outputs a detection signal corresponding to the light intensity of the incident light received by the light receiving pixels; and a control device that obtains the detection signal from the light receiving unit and uses the detection signal to detect the distance to an object, wherein the light receiving unit receives reflected light corresponding to the emitted light reflected by the object as the incident light, and the detection signal corresponds to the light intensity of the reflected light. In a case where a first object and a second object are detected and it is determined that the second object is a pseudo-object corresponding to the first object, the control device may remove the detection result of the second object, wherein the second object is located at a distance N times (N is a natural number greater than 2) the distance from the first object on an extension line of a straight line connecting the optical ranging device and the first object, and in a case where it is determined that the acquired detection signal is a detection signal corresponding to the reflected light reflected by the window portion, the detection result corresponding to the window portion is removed.

[0008] According to the optical distance measuring device of this mode, when a first object and a second object are detected and it is determined that the second object is a pseudo object corresponding to the first object, the detection result of the second object is removed. Therefore, the influence of the pseudo object on the detection of the distance can be reduced, and the object mark can be detected correctly. The vehicle equipped with the optical distance measuring device can avoid detecting the second object as an actual object mark, and suppress or prevent the execution of control for avoiding collision with the pseudo object. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above-mentioned object and other objects, features and advantages of the present disclosure will become more apparent through the following detailed description with reference to the accompanying drawings.

[0010] Figure 1 It is an explanatory diagram showing the structure of the optical distance measuring device according to the first embodiment.

[0011] Figure 2 It is an explanatory diagram showing the structure of the light receiving unit.

[0012] Figure 3 is a flowchart showing a pseudo object removal process.

[0013] Figure 4 This is an explanatory diagram showing a state in which a second object is detected in a top view.

[0014] Figure 5 It is an explanatory diagram showing peak signals of a first object and a second object.

[0015] Figure 6 This is an explanatory diagram showing a state in which a second object is detected in a side view.

[0016] Figure 7 This is an explanatory diagram for explaining the conditions under which the optical distance measuring device according to the second embodiment determines that the second object is a pseudo object.

[0017] Figure 8 This is an explanatory diagram for explaining the conditions under which the optical distance measuring device according to the third embodiment determines that the second object is a pseudo object.

[0018] Fig. 9 This is an explanatory diagram for explaining the conditions under which the optical distance measuring device according to the fourth embodiment determines that the second object is a pseudo object.

[0019] Fig.10 This is an explanatory diagram for explaining the conditions for determining a peak signal corresponding to clutter by the optical distance measuring device according to the fifth embodiment. DETAILED DESCRIPTION

[0020] A. First Implementation Method:

[0021] like Figure 1As shown, the optical ranging device 200 as the first embodiment of the present disclosure is mounted on a moving body such as a vehicle for use. The optical ranging device 200 detects the distance, relative speed and angle to objects such as other vehicles, pedestrians, buildings, etc. that exist in a set ranging range. The detection result of the optical ranging device 200 is used, for example, in the driving control of the vehicle. The optical ranging device 200 includes a control device 100, and includes a light emitting unit 40, a scanning unit 50 and a light receiving unit 60 inside a housing 80. A window 82 for transmitting laser light is provided on the wall surface of the housing 80.

[0022] The light emitting unit 40 includes a laser diode as a light source for optical distance measurement, and emits laser light DL as emission light for distance measurement. As the light source of the light emitting unit 40, other light sources such as solid-state lasers may be used instead of laser diodes.

[0023] The scanning unit 50 functions as a so-called one-dimensional scanner. The scanning unit 50 includes a reflector 51 and a rotating unit 52. The reflector 51 is fixed to the rotating unit 52. The rotating unit 52 receives a control signal from the control device 100 and rotates forward and reversely with the central axis AX as the rotation axis. The laser light DL emitted from the light emitting unit 40 is reflected by the reflector 51, and is emitted to the outside of the housing 80 through the window 82.

[0024] The laser beam DL passes through the reflective mirror 51 which is rotated by the rotating part 52, and travels along the Figure 1 The S direction shown scans within a predetermined range. Hereinafter, the range in which the optical distance measuring device 200 scans the laser light DL for distance measurement is also referred to as a scanning range RA. The S direction is the scanning direction of the laser light DL, and in this embodiment, the S direction is parallel to the horizontal plane. Figure 1 The V direction shown is the arrangement direction of the pixels 66 described later. The V direction is a direction perpendicular to the S direction, and in the present embodiment, the V direction is parallel to the vertical direction.

[0025] The light receiving unit 60 receives incident light and outputs a detection signal corresponding to the intensity of the incident light received. The incident light may include reflected light RL and interference light, wherein the reflected light RL corresponds to the target object within the scanning range RA, for example Figure 1 The laser light DL reflected by the object OB shown is interfering light such as sunlight, light from street lamps, and lighting of other vehicles.

[0026] The control device 100 is a microcomputer having a known microprocessor and a memory. The microprocessor executes a program pre-stored in the memory to realize the functions of the control unit 110, the adding unit 120, the histogram generating unit 130, the peak detecting unit 140, the pseudo object determining unit 150, and the distance calculating unit 160.

[0027] The control unit 110 performs drive control of the light emitting unit 40, the scanning unit 50, and the light receiving unit 60. More specifically, the control unit 110 outputs a command signal to the light emitting unit 40 to make the laser diode emit light, outputs an address signal to the light receiving unit 60 to activate the light receiving element, and outputs a control signal to the rotating unit 52 to the scanning unit 50.

[0028] The adding unit 120 is a circuit that adds the signal strengths of the light receiving elements of the light receiving unit 60. The histogram generating unit 130 generates a histogram of the signal strength with respect to the time axis by adding the addition results of the adding unit 120 multiple times. The peak detecting unit 140 analyzes the histogram input from the histogram generating unit 130 and detects the position of the peak signal of the signal corresponding to the reflected light RL with respect to time. The peak signal in the histogram indicates the intensity of the reflected light pulse, indicating that an object may exist at a position (distance) corresponding to the TOF (time of flight) corresponding to the peak signal. The position of the detected peak signal is output to the pseudo object determining unit 150.

[0029] The pseudo object determination unit 150 uses the peak signal detected by the peak detection unit 140 to determine whether the detected object is a pseudo object. The so-called "pseudo object" means an object that does not actually exist and is detected by the light receiving unit 60 due to multiple reflections of the emitted light emitted from the optical ranging device 200 on the object and the light receiving element. The pseudo object is also called a "ghost". If the vehicle equipped with the optical ranging device detects the pseudo object as an actual object, it may perform control such as braking control to avoid collision with the pseudo object.

[0030] If the laser light DL emitted from the light emitting unit 40 irradiates an object having a high reflectivity such as a highly reflective material, a high-intensity reflected light RL can be obtained. If the high-intensity reflected light RL is incident on the light receiving element 68, a portion of the reflected light RL is detected by the light receiving element 68 as a peak signal corresponding to the distance from the object. The reflected light RL that is not received by the light receiving element 68 may, for example, not be incident on the light receiving element 68 but be reflected by the surface of the light receiving element 68 and travel again in the direction of the object. Hereinafter, the reflected light that is reflected by the surface of the light receiving element 68 and travels again in the direction of the object will also be referred to as "second reflected light". If the second reflected light is reflected by the object and incident on the light receiving element 68, it is detected as a peak signal corresponding to a pseudo object that is different from the peak signal of the reflected light RL. In the case where the second reflected light is not incident on the light receiving element 68 but is further reflected by the light receiving element 68, it is detected as a peak signal that is different from the second reflected light, and the same process can be repeated later. The laser beam is reflected by the object N times (N is a natural number greater than 2) through multiple reflections from the object and the light receiving element. Therefore, a pseudo object can be detected as a peak signal at a position N times the distance from the optical ranging device 200 to the object.

[0031] The distance calculation unit 160 uses TOF to measure the distance to the target object, such as the object OB, that exists in the scanning range RA. More specifically, the distance calculation unit 160 calculates the distance to the object OB based on the time from the time when the light emitting unit 40 emits the laser light DL to the time when the peak signal of the reflected light RL is received, that is, the flight time of the laser light DL. In the optical ranging device 200 of this embodiment, the pseudo object removal process described later is performed. When a pseudo object is detected by the pseudo object determination unit 150, the distance calculation unit 160 removes the detection result corresponding to the pseudo object to detect the distance. When no pseudo object is detected, the distance is detected using the acquired peak signal.

[0032] use Figure 2 , the structure of the light receiving unit 60 will be described. The light receiving unit 60 includes a plurality of pixels 66 on the light receiving surface. The pixels 66 are arranged in a long rectangular shape along the V direction on a two-dimensional plane corresponding to the S direction and the V direction. Figure 2 The arrangement of the light receiving units 60 shown corresponds to light receiving pixels corresponding to one time slot in the scanning range RA of the laser light DL.

[0033] Each pixel 66 includes a plurality of light receiving elements 68. In the present embodiment, the pixel 66 is arranged by five light receiving elements 68 in the S direction and the V direction respectively. In the present embodiment, a single photon avalanche diode (SPAD) is used in the light receiving element 68. If light (photons) is input to each SPAD, a pulsed signal representing the incident light can be output. The adding unit 120 calculates the added value for each pixel 66 by counting the number of signals output from the plurality of light receiving elements 68 of each pixel 66. The pixel 66 can be composed of one light receiving element 68, or can include any number of light receiving elements 68 of more than two. The light receiving elements 68 can also be arranged in any shape. In the light receiving element 68, a PIN photodiode can also be used instead of a SPAD.

[0034] use Figure 3 , the pseudo object removal process performed by the optical ranging device 200 of the present embodiment is described. For example, the pseudo object removal process is started by turning on the power of the optical ranging device 200. For example, the pseudo object removal process is performed on each pixel 66 in each time slot (direction) included in the scanning range RA. Figure 3 The illustrated flowchart shows an example of processing in one pixel 66 in one time slot (direction) in the scanning range RA.

[0035] like Figure 3 As shown, the control device 100 drives and controls the light emitting unit 40, the scanning unit 50, and the light receiving unit 60 through the control unit 110, and starts detecting the target object and the distance within the scanning range RA (hereinafter, also referred to as "distance measurement processing") (step S10). The adding unit 120 counts the number of signals output from the light receiving element 68 of the pixel 66, and the histogram generating unit 130 generates a histogram of the signal intensity with respect to the time axis. The peak detecting unit 140 analyzes the histogram and detects the peak signal of the first object by receiving the reflected light from the first object as an object within the scanning range RA (step S20).

[0036] If the first object is detected, the peak detection unit 140 confirms whether there is a peak signal corresponding to the second object in the histogram, that is, whether the second object is detected (step S30). The so-called second object means an object that can be determined as a pseudo object corresponding to the first object among the objects detected together with the first object. In this embodiment, an object located at a distance N times (N is a natural number greater than 2) from the first object on the extension line of the straight line connecting the optical ranging device 200 and the first object, that is, the emission direction of the laser DL, is determined as the second object. In the case where the second object is not detected (S30: No), the distance calculation unit 160 uses the peak signals of the detected first object and other objects to detect the distance (step S60) and completes the processing. In the case where the second object is detected (S30: Yes), the pseudo object determination unit 150 determines whether the detected second object is a pseudo object (step S40).

[0037] In this embodiment, when an object that does not transmit light, that is, an object having light non-transmittance (hereinafter, also referred to as a "third object") is detected, and the second object is detected at a position farther from the optical ranging device 200 than the third object, the pseudo object determination unit 150 determines that the second object is a pseudo object. The third object includes, for example, various objects having light non-transmittance such as roads, ground, and walls of buildings. It is also possible to determine whether the third object is detected based on the distance measurement result of the optical ranging device 200, for example, it is also possible to determine based on the detection result of a detector other than the optical ranging device 200, such as a camera, a radar, etc.

[0038] If the second object is determined to be a pseudo object (S40: Yes), the distance calculation unit 160 excludes the peak signal corresponding to the second object from the distance calculation, and uses the detected peak signals of the first object and other objects to detect the distance (step S50), and the processing is completed. Instead of excluding the peak signal corresponding to the second object from the distance calculation, the processing of deleting the peak signal corresponding to the second object from the histogram may be performed. In the case where the second object is not determined to be a pseudo object (S40: No), the distance calculation unit 160 uses the detected peak signals of the first object and the second object and other objects to detect the distance (step S60), and the processing is completed.

[0039] use Figures 4 to 6 , a specific example of pseudo object removal processing performed by the optical ranging device 200 of this embodiment is described. Figure 4 FIG. 2 shows a state where a vehicle C1 equipped with the optical distance measuring device 200 of the present embodiment is traveling on a road RS. Figure 4, a first object OB1 and a second object OB2 as a pseudo object corresponding to the first object OB1 are conceptually shown. The first object OB1 is a so-called strong reflective material that utilizes so-called recursive reflection in which incident light is reflected toward a light source of the incident light. The first object OB1 is also called, for example, a retroreflector, a corner cube, a recursive reflector, a recursive reflective material, etc. The intensity of the reflected light from the first object OB1 can be greater than usual. Figure 4 As shown, the first object OB1 is located at a distance D1 from the optical ranging device 200 in the direction OL, and the second object OB2 is located at a distance D2 from the optical ranging device 200 in the direction OL. The distance D2 is equivalent to twice the distance D1. The optical ranging device 200 completes the detection of the road RS as the third object during the driving of the vehicle C1.

[0040] like Figure 4 As shown, the laser emitted in the direction OL for distance measurement is reflected by the first object OB1 among the objects in the direction OL. Figure 5 As shown in the histogram of the signal intensity, a portion of the reflected light from the first object OB1 is received by the light receiving element 68 of the light receiving unit 60 and detected as a peak signal PS1 corresponding to the first object OB1. The distance calculation unit 160 uses TOF and the time T1 when the peak signal PS1 is detected to calculate the distance D1 to the first object OB1.

[0041] The first object OB1 is a highly reflective material, and the intensity of the reflected light from the first object OB1 is relatively large. Therefore, a portion of the reflected light from the first object OB1 is reflected by the surface of the light receiving unit 60 and moves toward the direction OL as the second reflected light. The second reflected light is reflected by the first object OB1 and received by the light receiving element 68. Figure 5 As shown, since the second reflected light incident on the light receiving element 68 reciprocates twice between the first object OB1 and the light receiving element 68, a position at a distance D2 twice as long as the distance D1 in the direction OL is detected as a peak signal PS2 corresponding to the second object OB2.

[0042] exist Figure 6 , a state where the distances of the first object OB1 and the second object OB2 are detected by the optical distance measuring device 200 is conceptually shown as viewed from the side of the vehicle C1. Figure 6 As shown, the optical distance measuring device 200 detects the road RS together with the first object OB1 and the second object OB2. The pseudo object determination unit 150 uses the detection result of the road RS and the detection result of the distance of the second object OB2 to determine whether the second object OB2 is located farther from the optical distance measuring device 200 than the road RS. Figure 6As shown, the second object OB2 is detected on the straight line OL at a position farther from the optical distance measuring device 200 than the road RS, which is the third object. Therefore, the pseudo object determination unit 150 determines that the second object OB2 is a pseudo object. The distance calculation unit 160 excludes the peak signal corresponding to the second object OB2 from the distance calculation and uses the peak signal of the first object OB1 to detect the distance.

[0043] As described above, according to the optical ranging device 200 of this embodiment, when the first object OB1 and the second object OB2 are detected and it is determined that the second object OB2 is a pseudo object corresponding to the first object OB1, the detection result of the second object OB2 is removed. Therefore, the influence of the pseudo object can be reduced and the object mark can be detected correctly. The vehicle equipped with the optical ranging device 200 can avoid detecting the second object OB2 as an actual object mark, and suppress or prevent the execution of control for avoiding collision with the pseudo object.

[0044] According to the optical ranging device 200 of the present embodiment, when the road RS is detected as a third object having light non-transmittance and the second object OB2 is detected at a position farther from the optical ranging device 200 than the road RS, the pseudo object determination unit 150 determines the second object OB2 as a pseudo object. By using the state where the object target is not physically detected as a pseudo object determination condition, it is possible to reliably determine whether it is a pseudo object.

[0045] B. Second Implementation Method:

[0046] use Figure 7 The optical distance measuring device 200 of the second embodiment is described. The optical distance measuring device 200 of the second embodiment differs from the optical distance measuring device 200 of the first embodiment in the method of determining a pseudo object in step S40 of pseudo object removal processing, but the other configurations are the same as those of the optical distance measuring device 200 of the first embodiment.

[0047] When the optical ranging device 200 of this embodiment detects a second object during the movement of the optical ranging device 200, the result of tracking the relative position of the second object relative to the first object is used to determine whether the second object is a pseudo object. More specifically, the pseudo object determination unit 150 tracks the relative position of the second object relative to the first object within a predetermined period from the moment the second object is detected. The so-called predetermined period is the movement period of the optical ranging device 200, and can be set to an arbitrary period. When the relative position of the second object relative to the first object maintains a position that is N times the distance from the optical ranging device 200 to the first object, the pseudo object determination unit 150 determines that the second object is a pseudo object.

[0048] like Figure 7As shown, the optical ranging device 200 is mounted on the vehicle C2. The optical ranging device 200 moves sequentially to the position CP1, the position CP2, and the position CP3 on the road RS2 during a predetermined period as the vehicle C2 travels. The optical ranging device 200 detects the first object OB21, which is a strong reflective material, at the position CP1, and detects the second object OB22 at the position OP1. The optical ranging device 200 detects the first object OB21 at the position CP2, and detects the second object OB22 at the position OP2, and detects the first object OB21 at the position CP3, and detects the second object OB22 at the position OP3. During the predetermined period from the moment when the second object OB22 is detected at the position CP1 to the moment when the vehicle C2 moves to the position CP3, the relative position of the second object OB22 with respect to the first object OB21 maintains a distance twice the distance from the optical ranging device 200 to the first object OB21. Therefore, the pseudo object determination unit 150 determines the second object OB22 as a pseudo object.

[0049] According to the optical ranging device 200 of the present embodiment, the ranging process is performed while the optical ranging device 200 is moving, and the second object OB22 is tracked within a predetermined period from the moment when the second object OB22 is detected. When the relative position of the second object OB22 with respect to the first object OB21 maintains a distance N times the distance from the optical ranging device 200 to the first object OB21, the pseudo object determination unit 150 determines the second object OB2 as a pseudo object. Whether the second object OB2 is a pseudo object can be determined by using the behavior of the second object OB2 during the movement of the optical ranging device 200. Therefore, whether the second object OB2 is a pseudo object can be determined during the movement of the optical ranging device 200.

[0050] C. Third Implementation Method:

[0051] use Figure 8 The optical distance measuring device 200 of the third embodiment is described below. The optical distance measuring device 200 of the third embodiment differs from the optical distance measuring device 200 of the first embodiment in the method of determining a pseudo object in step S40 of pseudo object removal processing, but the other configurations are the same as those of the optical distance measuring device 200 of the first embodiment.

[0052] In the optical ranging device 200 of the present embodiment, as a method for determining a pseudo object, the so-called law of light attenuation, in which the intensity of light is inversely proportional to the square of the distance from the light source, is used. When the signal intensity of the second object conforms to the so-called inverse square law relative to the signal intensity of the first object, the second object is determined to be a pseudo object. More specifically, when the signal intensity of the second object located at a distance N times the distance from the optical ranging device 200 to the first object OB1 is inversely proportional to the square of N relative to the signal intensity of the first object, the second object is determined to be a pseudo object.

[0053] like Figure 8 As shown, the first object OB31, which is a strongly reflective material located at a distance D31 from the optical distance measuring device 200, is detected as a peak signal PS31. The second object OB22, which is located at a distance D32 from the optical distance measuring device 200 equivalent to twice the distance D31, is detected as a peak signal PS32. Figure 8 The curve PL shown is a graph that is inversely proportional to the square of the ratio relative to the distance D31, based on the distance D31 to the first object OB31. When the signal strength of the second object OB32 is on the curve PL, the pseudo object determination unit 150 determines that the second object OB32 is a pseudo object. This is not limited to the case where the signal strength of the second object OB32 is on the curve PL. In addition, the second object OB32 may be determined to be a pseudo object when the signal strength of the second object OB32 is within a predetermined range including the curve PL, taking into account detection errors and the like. Figure 8 The distance D32 shown is twice the distance D31 (N=2), and the signal strength P32 of the peak signal PS32 is one-fourth of the square of N, which is about one-fourth of the signal strength P31 of the peak signal PS31. The pseudo object determination unit 150 determines that the signal strength of the second object OB32 is inversely proportional to the square of N relative to the signal strength of the first object OB31, and determines that the second object OB32 is a pseudo object.

[0054] According to the optical ranging device 200 of this embodiment, when the signal intensity P32 of the second object OB32 relative to the signal intensity P31 of the first object OB31 is inversely proportional to the square of N, the pseudo object determination unit 150 determines that the second object OB32 is a pseudo object. Whether the second object is a pseudo object can be determined based on the histogram of the signal intensity, and a pseudo object can be detected by a simple method.

[0055] D. Fourth Implementation Method:

[0056] use Fig. 9, a fourth embodiment of the optical ranging device 200 is described. In the optical ranging device 200 of the fourth embodiment, the method of determining a pseudo object in step S40 of the pseudo object removal process is different from that of the optical ranging device 200 of the first embodiment, and the other structures are the same as those of the optical ranging device 200 of the first embodiment.

[0057] After detecting the first object and the second object, the optical ranging device 200 of the present embodiment performs ranging processing based on the first ranging condition in which the output of the light emitting unit 40 is reduced compared to the output when the first object and the second object are detected. The optical ranging device 200 may perform ranging processing based on the second ranging condition in which the number of times the detection signal is obtained from the light receiving unit 60 by the histogram generating unit 130 is reduced compared to the number of times the first object and the second object are detected, together with or instead of the first ranging condition.

[0058] like Fig. 9 As shown, the dotted lines represent the peak signal PS41 corresponding to the first object OB41 which is a strong reflective material, and the peak signal PS42 corresponding to the second object OB42 which is located at a distance twice the distance from the first object OB41, detected by the peak detection unit 140. In the present embodiment, if the second object OB42 is detected together with the first object OB41, the control unit 110 controls the light emitting unit 40 to detect the distance in a state where the output of the laser is lower than the output when the first object OB41 and the second object OB42 are detected. The ranging process based on at least one of the first ranging condition or the second ranging condition is also referred to as "strong reflective object detection process." The output of the laser light which is reduced in the strong reflective object detection process is set to an output level capable of detecting the peak signal PS41W of the first object OB41 which is a strong reflective material. By reducing the output of the laser light, as Fig. 9 As shown, the signal intensity P41 of the peak signal PS41 corresponding to the first object OB41 is reduced, and a peak signal PS41W having a signal intensity P41W can be obtained. The peak signal PS42 having a signal intensity P42 corresponding to the second object OB42 disappears and is not detected as a peak signal. In this way, by performing a strong reflective object detection process after detecting the first object OB41 and the second object OB42, it is determined whether the first object OB41 is a strong reflective material by determining whether the first object OB41 is detected. In the case where it is determined that the first object OB41 is a strong reflective material, the pseudo object determination unit 150 determines the second object OB42 as a pseudo object.

[0059] According to the optical distance measuring device 200 of this embodiment, when the first object OB41 and the second object OB42 are detected, a strong reflective object detection process is performed to reduce the output of the laser light compared to the output when the first object OB41 and the second object OB42 are detected. When the first object OB41 is detected, the first object OB41 is determined to be a strong reflective material, and the second object OB42 is determined to be a pseudo object. Therefore, pseudo objects can be detected by a simple method.

[0060] E. Fifth Implementation Method:

[0061] use Fig.10 The optical ranging device 200 of the fifth embodiment is described. The optical ranging device 200 of the fifth embodiment is different from the optical ranging device 200 of the first embodiment in that, in addition to the pseudo object removal process of the first embodiment, a clutter removal process is further performed to remove the clutter detection result. The structure other than this is the same as the optical ranging device 200 of the first embodiment. The so-called "clutter" refers to the reflected light emitted from the light emitting unit 40 and reflected by the window 82 of the housing 80. Since the clutter can be detected as a peak signal by being incident on the light receiving unit 60, there is a case where the ranging accuracy of the optical ranging device 200 is reduced. Generally speaking, the clutter is detected as a peak signal at a close distance from the optical ranging device 200 and with an intensity smaller than the reflected light from the object OB.

[0062] exist Fig.10 , a peak signal PS5 corresponding to clutter is shown. The peak signal PS5 is detected together with the peak signal PS1 of the first object OB1 and the like through the histogram analysis performed by the peak detection unit 140. In the present embodiment, when the detection distance of the detected peak signal is less than a predetermined time threshold Tt, and the received light intensity is less than a predetermined intensity threshold Pt, the pseudo object determination unit 150 determines that the detected peak signal is a peak signal corresponding to clutter. The distance calculation unit 160 removes the detection result of the peak signal PS5 corresponding to clutter and detects the distance.

[0063] exist Fig.10 The maximum value Pmax of the light intensity is shown in FIG. 1 . The maximum value Pmax is the total number of light receiving elements 68 for each pixel used in making the histogram. Figure 2As described in , one pixel 66 is composed of 5×5 light receiving elements 68. When N is set to an integer greater than 2, when the light receiving results of N times of light emission are summed up to make a histogram, the maximum value Pmax of the light receiving intensity is equal to N×5×5. The intensity threshold Pt is usually set to a value smaller than the maximum value Pmax of the light receiving intensity. In the present embodiment, the intensity threshold Pt is set to a light receiving intensity of 50% of the maximum value Pmax. The intensity threshold Pt can also be set to a value equal to the maximum value Pmax. The time threshold Tt is set to an arbitrary distance close to the optical ranging device 200. The time threshold Tt can also be set to a specific flight time equivalent to the distance of the optical path from the light emitting unit 40 to the window 82, or it can be set to a distance greater than the distance of the optical path from the light emitting unit 40 to the window 82 in consideration of errors, etc. In the present embodiment, the time threshold Tt is set to 1 meter from the light emitting unit 40, which is greater than the distance of the optical path from the light emitting unit 40 to the window 82.

[0064] According to the optical distance measuring device 200 of this embodiment, in addition to the detection result of the pseudo object, the peak signal caused by clutter is removed during the distance measuring process. Therefore, it is possible to suppress the reduction of the distance measuring accuracy of the optical distance measuring device 200 caused by clutter and detect the target object more accurately.

[0065] Other implementations:

[0066] The control unit and method described in the present disclosure may also be implemented by a special-purpose computer, wherein the special-purpose computer is provided by constituting a processor and a memory programmed to execute one or more functions concretized by a computer program. Alternatively, the control unit and method described in the present disclosure may also be implemented by a special-purpose computer provided by constituting a processor by one or more special-purpose hardware logic circuits. Alternatively, the control unit and method described in the present disclosure may also be implemented by one or more special-purpose computers, wherein the one or more special-purpose computers are constituted by a combination of a processor and a memory programmed to execute one or more functions and a processor constituted by one or more hardware logic circuits. In addition, the computer program may also be stored as an instruction executed by a computer in a computer-readable non-transient tangible recording medium.

[0067] The present disclosure is not limited to the above-mentioned embodiments, and can be implemented in various structures within the scope of the main purpose. For example, in order to solve part or all of the above-mentioned problems, or to achieve part or all of the above-mentioned effects, the technical features in the embodiments corresponding to the technical features recorded in the column of the invention content can be appropriately replaced or combined. In addition, if the technical feature is not stated to be necessary in this specification, it can be appropriately deleted.

Claims

1. An optical distance measuring device, comprising: a light emitting portion for emitting light; a window portion through which the light is emitted; a light receiving unit having light receiving pixels for receiving incident light, and outputting a detection signal corresponding to the light intensity of the incident light received by the light receiving pixels; and A control device acquires a detection signal from the light receiving portion and uses the detection signal to detect the distance to the object, wherein: The light receiving unit receives reflected light corresponding to the emitted light reflected by the object as the incident light, and the detection signal corresponds to the received light intensity of the reflected light. The control device removes the detection result of the second object when a first object and a second object are detected and it is determined that the second object is a pseudo object corresponding to the first object, wherein the second object is located at a distance N times the distance from the first object on an extension line of a straight line connecting the optical ranging device and the first object, where N is a natural number greater than 2, When it is determined that the acquired detection signal is a detection signal corresponding to the reflected light reflected by the window, the detection result corresponding to the window is removed, and After detecting the first object and the second object, the control device further performs ranging including at least one of the first ranging condition or the second ranging condition, i.e., strong reflective object detection processing, wherein the first ranging condition is to reduce the output of the emitted light compared to the output when the first object and the second object are detected, and the second ranging condition is to reduce the number of times the detection signal is obtained from the light receiving unit compared to the number of times the first object and the second object are detected. In the strongly reflective object detection process, when the first object is detected, the control device determines that the second object is the pseudo object.

2. The optical distance measuring device according to claim 1, wherein: When a third object having light opacity is further detected and the second object is detected at a position farther from the optical distance measuring device than the third object, the control device determines that the second object is the pseudo object.

3. The optical distance measuring device according to claim 1, wherein: When the optical ranging device detects the distance to the object during a predetermined period of movement and the relative position of the second object with respect to the first object maintains the N times distance, the control device determines that the second object is the pseudo object.

4. The optical distance measuring device according to claim 2, wherein: When the optical ranging device detects the distance to the object during a predetermined period of movement and the relative position of the second object with respect to the first object maintains the N times distance, the control device determines that the second object is the pseudo object.

5. The optical distance measuring device according to any one of claims 1 to 4, wherein: When the signal strength of the second object relative to the signal strength of the first object is inversely proportional to the square of N, the control device determines that the second object is the pseudo object.

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