JP2021143927A - Optical distance measuring device - Google Patents

Abstract

To suppress the erroneous recognition of a target attributable to multiple reflected light.SOLUTION: A control unit 50 of an optical distance measuring device 10 scans, in the inside of a scan range using a scanner 20, a plurality of irradiation lights emitted by a plurality of light emitting units 20a, 20b, the optical axes of which are parallel, and calculates the distance to a target 200 using the emission of the plurality of irradiation lights by the plurality of light emitting units and detection of reflected lights from the target by a light receiving unit 30. When emitted in one irradiation direction within the scan range and reflected light returned to the light receiving unit from a different direction from the one irradiation direction is detected, the control unit temporarily stops light emission of the light emitting unit that corresponds to the reflected light returned to the light receiving unit from the different direction from the one irradiation direction.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an optical ranging device.

Patent Document 1 discloses a radar device that irradiates a light beam in front of a vehicle and receives reflected light to detect an obstacle existing in front of the vehicle. In this radar device, a light beam emitted from a light emitting unit is reflected by a polygon mirror and irradiated to the outside through a window.

Japanese Patent Application Laid-Open No. 2014-29317 Public Relations

A part of the light beam emitted from the light emitting unit may be reflected by the window, further reflected by the polygon mirror, transmitted through the window, and irradiate in a direction different from the original irradiation direction. The light beam that irradiates a direction different from the original irradiation direction is weak, but if a high-reflectance object with high reflectance exists at the irradiation destination, the light beam hits the high-reflectivity object and the reflected light returned is received by the light receiving unit. It will be detected. As a result, there is a risk of erroneous recognition that an object exists even though the object does not exist in the original irradiation direction.

The present disclosure can be realized in the following forms.

According to one embodiment of the present disclosure, an optical ranging device (10) is provided. This optical ranging device includes a plurality of light emitting units (20a, 20b) having parallel optical axes and a mirror (26) that reflects a plurality of irradiation lights emitted by the plurality of light emitting units, which are housed in a case (60). ) And an optical system (25) including a window (28) that transmits the plurality of irradiation lights reflected by the mirror to the outside, and by changing the angle of the mirror, the scanning range within a predetermined scanning range is described. A scanner (22) that scans with a plurality of irradiation lights, and when the scanning range is scanned by the plurality of irradiation lights by the scanner, the reflected light reflected by a target existing in the scanning range is detected in the case. Distance calculation for calculating the distance to the target using the light receiving unit (30), the light emission of the plurality of irradiation lights by the plurality of light emitting units, and the detection of the reflected light from the target by the light receiving unit. A unit (48), a control unit that controls the light emission of the plurality of light emitting units and the operation of the scanner, and the irradiation light from one of the plurality of light emitting units is within the scanning range by the scanner. When the reflected light returned to the light receiving unit is detected from a direction different from the one irradiation direction when the light is emitted in one irradiation direction, the light returns to the light receiving unit from a direction different from the one irradiation direction. A control unit (50) for temporarily stopping the light emission of the light emitting unit corresponding to the reflected light is provided. According to this form, when the reflected light returned to the light receiving portion is detected from a direction different from the irradiation direction, the light emission of the light emitting portion corresponding to the reflected light is temporarily stopped, so that the light emission direction is different from one irradiation direction. Even if there is a high-reflectivity target in the direction, the irradiation light does not hit the high-reflectivity target, so it is erroneously recognized that the high-reflection target due to the multiple reflection light exists in the irradiation direction. Can be suppressed.

It is explanatory drawing which shows the vehicle equipped with the optical ranging device. It is explanatory drawing which shows the structure of the optical ranging device. It is explanatory drawing which shows the structure of the measuring part. It is explanatory drawing which shows the example of the histogram. Shows the irradiation light and the reflected light when the mirror angle is the first angle. The irradiation light and the reflected light when the mirror angle θ is the second angle are shown. It is explanatory drawing which shows the relationship between the scanning range of irradiation light and the rotation range of a mirror. It is a flowchart of the light emission control of a light emitting part and the rotation control of a mirror executed by a control part. It is explanatory drawing which shows the relationship between the rotation angle θ of a mirror, the light emission of the 1st light emitting part and the 2nd light emitting part, and the recognition of a target. It is explanatory drawing which shows the relationship between the interval of irradiation light, the effective diameter of a mirror, the interval between the center of the surface of a mirror, and a window, and the occurrence of a ghost when the rotation angle of a mirror is less than 45 °. It is explanatory drawing which shows the relationship between the interval of irradiation light, the effective diameter of a mirror, the interval between the center of the surface of a mirror, and a window, and the occurrence of a ghost when the rotation angle of a mirror is larger than 45 °. It is explanatory drawing which shows the light emitting sequence of the 1st light emitting part and the 2nd light emitting part in 3rd Embodiment. It is a graph which shows the light-receiving intensity of the light-receiving part 30 when both the 1st light-emitting part and the 2nd light-emitting part emit light, and when only the 2nd light-emitting part emits light.

-First embodiment:
As shown in FIG. 1, the optical ranging device 10 is mounted on the vehicle 100 and measures the distance L to the target object 200, which is an object. Specifically, the optical ranging device 10 emits a light emitting beam IL within the scanning range. If the target 200 exists within the scanning range, the light emitting beam IL hits the target 200, and the reflected light RL is returned from the target 200. The optical distance measuring device 10 measures the distance L to the target 200 by using the time TOF from the time when the light emitting beam IL is emitted to the time when the reflected light RL returned after hitting the target 200 is received. Assuming that c is the speed of light, L = c · TOF / 2.

As shown in FIG. 2, the optical ranging device 10 includes a light emitting unit 20, a scanner 22, a light receiving unit 30, a measuring unit 40, and a control unit 50. In the present embodiment, the light emitting unit 20 has two light emitting units, a first light emitting unit 20a and a second light emitting unit 20b. The first light emitting unit 20a and the second light emitting unit 20b are composed of, for example, a semiconductor laser diode, and their optical axes are parallel to each other. In response to an instruction from the control unit 50, the first light emitting unit 20a and the second light emitting unit 20b emit light of irradiation light ILA and ILB parallel to each other toward the mirror 26 of the scanner 22. The irradiation light ILA and ILB are, for example, pulsed laser light.

The scanner 22 includes a motor 24 and an optical system 25. The optical system 25 includes a mirror 26 and a window 28. The mirror 26 reflects the irradiation lights ILA and ILB emitted from the first light emitting unit 20a and the second light emitting unit 20b toward the window 28 as the irradiation lights ILA1 and ILB1. The window 28 transmits the irradiation lights ILA1 and ILB1 generated by reflection by the mirror 26 to the outside of the window 28. In the present embodiment, the light up to hitting the target 200 is called "irradiation light", and the light reflected and returned by the target 200 is called "reflected light". The motor 24 rotates the mirror 26 in response to an instruction from the control unit 50. Since the angle at which the irradiation lights ILA and ILB hit the mirror 26 changes, the directions of the irradiation lights ILA1 and ILB1 also change. If the mirror 26 is gradually rotated, the irradiation light ILA1 and ILB1 can scan within a predetermined scanning range. That is, the scanner 22 receives an instruction from the control unit 50 and scans within a predetermined scanning range using the plurality of irradiation lights ILA1 and ILB1. In the present embodiment, the angle of the mirror 26 is changed by using the motor 24, but the angle of the mirror 26 is changed by having a forced / resonant MEMS (Micro Electro Mechanical System) and driving the forced / resonant MEMS. May be changed. Further, a rotary solenoid may be used instead of the motor 24.

The control unit 50 controls the light emission in the first light emitting unit 20a and the second light emitting unit 20b and the operation of the scanner 22. Specifically, the control unit 50 controls the scanning of the scanner 22, detects the angle of the mirror 26 at this time, and irradiates from the first light emitting unit 20a and the second light emitting unit 20b based on the detection result. Controls the emission of light ILA and ILB. When the control unit 50 emits the irradiation light from one of the plurality of light emitting units 20a and 20b into one irradiation direction within the scanning range by the scanner 22, the control unit 50 receives light from a direction different from one irradiation direction. It has a storage unit 52 that holds in advance the rotation angle of the mirror 26 and the corresponding light emitting units 20a and 20b in which the reflected light returned to 30 is detected.

The light receiving unit 30 includes a light receiving element array 34 and a decoder 36 arranged in two dimensions of n × m (n and m are natural numbers of 2 or more). The light receiving element array 34 is configured by arranging a plurality of light receiving elements 32 in a two-dimensional matrix. The light receiving element 32 is composed of a single photon avalanche diode (SPAD), and the light receiving element array 34 is a SPAD array. The light receiving element 32 outputs a detection signal when light such as reflected light is incident on the light receiving surface. The configuration of the light receiving element 32 will be described later.

The decoder 36 is a circuit for selecting the light receiving element 32. The decoder 36 includes a selection control line CL provided for each row of a matrix composed of a plurality of light receiving elements 32 constituting the light receiving element array 34. The selection control line CL is connected to all of the light receiving elements 32 arranged in the corresponding row. The decoder 36 applies a selective control voltage to the selective control line CL, so that the light receiving element 32 is selected in column units. The data of the light receiving element 32 selected in column units is output to the data line DL provided in each row.

The measuring unit 40 measures the distance to the target 200 based on the difference between the time Lt when the first light emitting units 20a and 20b irradiate the pulsed laser light and the time when the light receiving unit 30 detects the reflected light. I do. The measuring unit 40 is connected to a data line DL provided for each row of the light receiving element array 34. Details of the configuration of the measuring unit 40 and data processing will be described later.

As shown in FIG. 3, the light receiving element 32 is composed of a well-known circuit including an avalanche photodiode 32d, a quenching resistor 32r, and an inverter circuit 32i. More specifically, in the light receiving element 32, the quenching resistor 32r and the avalanche photodiode 32d are connected in series between the power supply and the grounding line, and the input side of the inverter circuit 32i is connected to the connection point. It is composed of. The quenching resistor 32r is connected to the power supply side, and the avalanche photodiode 32d is connected to the ground line side so as to have a reverse bias. The light receiving element 32 operates in the Geiger mode, and when the reflected light (one or more photons) reflected from the object 200 is incident, a pulse signal indicating that the reflected light is incident is transmitted as a data line with a certain probability. Output to DL.

The measurement unit 40 includes an addition unit 42, a histogram generation unit 44, a peak detection unit 46, and a distance calculation unit 48.

The adding unit 42 adds the number of pulse signals output substantially simultaneously from the plurality of light receiving elements 32 included in the light receiving unit 30 to obtain an added value. The addition unit 42 outputs the obtained addition value to the histogram generation unit 44. The addition unit 42 may be configured to add the number of pulse signals output from one light receiving element 32 every predetermined period to obtain an addition value.

The histogram generation unit 44 generates a histogram based on the addition value output from the addition unit 42. FIG. 4 shows an example of a histogram. The class (horizontal axis) of the histogram indicates the flight time of the light from the time Lt when the light is irradiated from the first light emitting units 20a and 20b until the reflected light is received. This time is also referred to as TOF (TOF: Time Of Flight). The frequency (vertical axis) of the histogram is an added value calculated by the adding unit 42, and indicates the intensity of the reflected light RL reflected from the target 200. The histogram generation unit 44 records the addition value output from the addition unit 42 at predetermined time intervals according to the recording timing synchronized with the cycle of the pulsed laser light emitted from the first light emitting units 20a and 20b. Generates a histogram by. If the target 200 is present in the range where the light is irradiated by the first light emitting unit 20a and the second light emitting unit 20b, the frequency of the class corresponding to the time when the reflected light RLA and RLB from the target 200 are incident is large. Become. That is, if there is a class having a large frequency in the histogram, the distance to the target 200 can be calculated based on the time corresponding to the class. In this way, the distance calculation unit uses a histogram in which the detection results along the elapsed time from the light emission timing Lt of the plurality of first light emitting units 20a and the second light emitting unit 20b are superimposed to reach the target 200. Is calculated. In addition, in generating one histogram, the frequency may be integrated by irradiating light a plurality of times. By doing so, the SN ratio can be improved.

The peak detection unit 46 detects a peak from the histogram. In the present embodiment, the peak means a class having a frequency exceeding a predetermined threshold value TL. The distance calculation unit 48 acquires the TOF from the time tp corresponding to the peak and calculates the distance to the target 200.

Although the outline of the optical ranging device 10 has been described above, in the present embodiment, two light emitting units 20a and 20b are provided as light sources. The optical ranging device 10 using the two light emitting units 20a and 20b will be described below.

FIG. 5 is an explanatory diagram showing irradiation light and reflected light when the angle θ of the mirror 26 is the first angle θ1. The first light emitting unit 20a, the second light emitting unit 20b, the mirror 26, and the light receiving unit 30 are housed in the case 60. A window 28 is provided on one surface of the case 60. The mirror 26 is rotatable around the center 26o. The angle θ of the mirror 26 is an angle formed by the optical axis of the first light emitting unit 20a or the second light emitting unit 20b and the surface 26s of the mirror 26. The irradiation light ILA and the irradiation light ILB are parallel. The irradiation light ILA and the irradiation light ILB are reflected by the surface 26s of the mirror 26 to become the irradiation light ILA1 and the irradiation light ILB1, respectively. The irradiation light ILA1 and the irradiation light ILB1 pass through the window 28 and irradiate the target irradiation direction.

The irradiation light ILA1 and the irradiation light ILB1 pass through the window 28, and a part thereof is reflected by the window 28 to become the irradiation light ILA2 and the irradiation light ILB2, respectively. In the example shown in FIG. 5, the irradiation light ILA2 is further reflected by the surface 26s of the mirror 26 to become the irradiation light ILA3, passes through the window 28, and irradiates in a direction different from the target irradiation direction. The irradiation light ILB2 is repeatedly reflected inside the case 60, is absorbed, and is attenuated.

In the example of FIG. 5, it is assumed that the target 202, which is a high-reflectivity object, exists in the irradiation direction of the irradiation light ILA3. The reflected light RLA3 when the irradiation light ILA3 hits the target 202 passes through the window 28, is reflected by the surface 26s of the mirror 26, is reflected by the window 28, is reflected by the surface 26s of the mirror 26, and hits the light receiving portion 30. , Detected. In this case, even if the target does not exist in the original irradiation direction of the irradiation light ILA1, the target 202 is erroneously detected as if it exists in the original irradiation direction. This false positive is called "ghost 202g".

FIG. 6 shows the irradiation light and the reflected light when the angle θ of the mirror 26 is the second angle θ2. Similar to the case of FIG. 5, the irradiation light ILA and the irradiation light ILB are reflected by the surface 26s of the mirror 26 to become the irradiation light ILA1 and the irradiation light ILB1, respectively. The irradiation light ILA1 and the irradiation light ILB1 pass through the window 28 and irradiate the target irradiation direction.

Further, the irradiation light ILA1 and the irradiation light ILB1 pass through the window 28, and a part thereof is reflected by the window 28 to become the irradiation light ILA2 and the irradiation light ILB2, respectively. In the example shown in FIG. 6, the irradiation light ILA2 is further reflected by the surface 26s of the mirror 26 to become the irradiation light ILA3, but does not pass through the window 28, is repeatedly reflected inside the case 60, is absorbed, and is attenuated. I will do it. On the other hand, the irradiation light ILB2 is further reflected by the surface 26s of the mirror 26 to become the irradiation light ILB3, passes through the window 28, and irradiates in a direction different from the target irradiation direction.

In the example of FIG. 6, the target 204, which is a high-reflectivity object, exists in the irradiation direction of the irradiation light ILB3. The reflected light RLB3 when the irradiation light ILB3 hits the target 204 passes through the window 28, is reflected by the surface 26s of the mirror 26, is reflected by the window 28, is reflected by the surface 26s of the mirror 26, and hits the light receiving portion 30. , Detected. In this case, even if the target does not exist in the original irradiation direction of the irradiation light ILB1, the target 204 is erroneously detected as if it exists in the original irradiation direction. That is, 204 g of ghost is detected.

FIG. 7 is an explanatory diagram briefly showing the relationship between the scanning range (−θ to + θ) of the irradiation light IL1 and the rotation range (θst to θen) of the mirror 26. In the present embodiment, as described above, since there are two light emitting units 20, the first light emitting unit 20a and the second light emitting unit 20b, there are also two irradiation lights, ILA and ILB. , For the sake of simplicity, it will be described as one irradiation light IL. Assuming that the scanning range of the irradiation light IL1 is in the range of angles −φ to + φ centered on 0, 2 * θst + φ = 90 ° is satisfied at the start of scanning, that is, when the rotation angle θ of the mirror 26 is θst. = (90-φ) / 2. Further, at the end of scanning, that is, when the rotation angle θ of the mirror 26 is θen, 2 * θen = φ + 90 ° is satisfied, so θen = (φ + 90 °) / 2. By determining the scanning range (−φ to + φ) of the irradiation light IL1 in this way, the rotation range (θst to θen) of the mirror 26 can be determined. For example, assuming that the scanning range of the irradiation light IL1 is −30 ° to + 30 °, the rotation range of the mirror 26 is from 30 ° to 60 °. When the rotation angle θ of the mirror 26 is 45 °, the irradiation light IL1 is irradiated in the direction of 0 °.

FIG. 8 is a flowchart of the first light emitting unit 20a, the second light emitting unit 20b, and the rotation control of the mirror 26 executed by the control unit 50. In step S100, the control unit 50 sets the rotation angle θ of the mirror 26 so that the rotation angle θ of the mirror 26 becomes the initial value θst. In step S110, the control unit 50 acquires the rotation angle θ of the mirror 26. The rotation angle θ of the mirror 26 can be obtained by using, for example, an encoder connected to the motor 24 that rotates the mirror 26. The motor 24 does not rotate the mirror 26 by 360 °, but repeatedly rotates the mirror 26 from the rotation angle θst to the rotation angle θen described later.

In step S120, the control unit 50 determines whether the rotation angle θ of the mirror 26 is larger than θa and less than θb. When the rotation angle θ of the mirror 26 is larger than θa and less than θb, the control unit 50 shifts the process to step S130. When the rotation angle θ of the mirror 26 is larger than θa and less than θb, the irradiation light ILA3 irradiates in a direction different from the target irradiation direction as described with reference to FIG. When the target 202, which is a high-reflectivity object, exists in the irradiation direction of the irradiation light ILA3, the reflected light RLA3 when the irradiation light ILA3 hits the target 202 is also strong, so that the irradiation light ILA1 Even if the target 202 does not exist in the original irradiation direction, the ghost 202g may be erroneously detected as if the target 202 exists in the original irradiation direction. Therefore, in step S130, the control unit 50 causes only the second light emitting unit 20b to emit light. When the rotation angle θ of the mirror 26 is θa or less or θb or more, the control unit 50 shifts the process to step S140.

In step S140, the control unit 50 determines whether the rotation angle θ of the mirror 26 is larger than θc and less than θd. Note that θc is a value larger than θb. When the rotation angle θ of the mirror 26 is larger than θc and less than θd, the control unit 50 shifts the process to step S150. When the rotation angle θ of the mirror 26 is larger than θc and less than θd, the irradiation light ILB3 irradiates in a direction different from the target irradiation direction as described with reference to FIG. When the target 204, which is a highly reflective object, exists in the irradiation direction of the irradiation light ILB3, the reflected light RLB3 when the irradiation light ILB3 hits the target 204 is also strong, so that the irradiation light ILB1 Even if the target 204 does not exist in the original irradiation direction, there is a possibility that the ghost 204g is erroneously detected as if the target 204 exists in the original irradiation direction. Therefore, in step S150, the control unit 50 causes only the first light emitting unit 20a to emit light. When the rotation angle θ of the mirror 26 is θc or less or θd or more, the control unit 50 shifts the process to step S160 and causes both the first light emitting unit 20a and the second light emitting unit 20b to emit light.

In step S170, the control unit 50 rotates the mirror 26 by Δθ. In step S180, the control unit 50 determines whether or not the rotation angle θ of the mirror 26 is θed or more. When the rotation angle θ of the mirror 26 is θed or more, the control unit 50 shifts the process to step S190, and when the rotation angle θ is less than the rotation angle θ of the mirror 26, the control unit 50 is the control unit. 50 shifts the process to step S110, and repeats the processes after step S110. In step S190, the control unit 50 determines whether or not to end the process. For example, when the switch of the vehicle 100 is turned off, the control unit 50 ends the process. If the control unit 50 does not end the process, the control unit 50 shifts the process to step S100 and repeats the processes after step S100.

FIG. 9 is an explanatory diagram showing the relationship between the rotation angle θ of the mirror 26, the light emission of the first light emitting unit 20a and the second light emitting unit 20b, and the recognition of the target. In the first cycle, the control unit 50 causes both the first light emitting unit 20a and the second light emitting unit 20b to emit light in the entire section where the rotation angle of the mirror 26 is from θst to θen. In this case, the rotation angle θ of the mirror 26 and the recognition of the target have the following relationship.
(1) θst ≤ θ ≤ θa: The target is not recognized.
(2) θa <θ <θb: Recognize the target.
(3) θb ≦ θ ≦ θc: The target is not recognized.
(4) θc <θ <θd: Recognize the target.
(5) θd ≦ θ ≦ θen: The target is not recognized.
When this target is recognized, it is unclear whether it is recognized by the reflected light from the target existing in the irradiation direction or the reflected light from the target existing in the direction different from the irradiation direction, that is, the recognition of the ghost.

In the second cycle, the control unit 50 causes the first light emitting unit 20a and the second light emitting unit 20b to emit light as follows according to the rotation angle θ of the mirror 26 according to the flowchart shown in FIG. As a result, the first light emitting unit 20a and the second light emitting unit 20b emit light as follows. That is,
(6) θst ≦ θ ≦ θa: Both the first light emitting unit 20a and the second light emitting unit 20b emit light.
(7) θa <θ <θb: The first light emitting unit 20a does not emit light, but the second light emitting unit 20b emits light.
(8) θb ≦ θ ≦ θc: Both the first light emitting unit 20a and the second light emitting unit 20b emit light.
(9) θc <θ <θd: The first light emitting unit 20a emits light, and the second light emitting unit 20b does not emit light.
(10) θd ≦ θ ≦ θen: Both the first light emitting unit 20a and the second light emitting unit 20b emit light.
In this case, the reflected light is not recognized regardless of the value in the range of θst to θen of the rotation angle θ of the mirror 26. Therefore, in the first cycle, when θa <θ <θb, the irradiation light from the first light emitting unit 20a is irradiated in a direction different from the original irradiation direction, and the reflected light from the different direction is recognized, that is, the ghost is generated. It is probable that it was recognized. Further, in the first cycle, when θc <θ <θd, the irradiation light from the second light emitting unit 20b is irradiated in a direction different from the original irradiation direction, and the reflected light from the different direction is recognized, that is, the ghost is generated. It is probable that it was recognized.

In this way, when the light receiving unit 30 in the first cycle recognizes the target by the reflected light received and it is doubtful whether or not a ghost has occurred, the control unit 50 determines whether or not a ghost has occurred in the next second cycle. At a suspicious angle of rotation, one of the first light emitting unit 20a and the second light emitting unit 20b is stopped. At this time, if the ghost disappears when the light emission is stopped, it can be determined that the recognized target in the first cycle is due to the ghost. The control unit 50 stores the light emitting unit in which the ghost is generated and the rotation angle in association with each other in the storage unit 52. In this way, in the distance measurement in the next cycle, it is possible to distinguish whether or not the target detected in the direction is due to a ghost. By holding the correspondence between the light emitting units 20a and 20b corresponding to the rotation angle of the mirror 26 in which ghost does not occur in the storage unit 52 in advance, the control unit 50 dynamically operates the corresponding light emitting units 20a and 20b. It is possible to switch the stop.

In FIG. 9, in the second cycle, the first light emitting unit 20a is not emitted when θa <θ <θb, and the second light emitting unit 20b is not emitted when θc <θ <θd, but the second light emitting unit 20b is not emitted in the second cycle. The first light emitting unit 20a may not emit light, and the second light emitting unit 20b may not emit light in the third cycle. It is possible to reliably recognize whether or not the recognized reflected light is due to a ghost.

As described above, according to the first embodiment, the control unit 50 scans the irradiation light ILA1 and ILB1 from one of the first light emitting unit 20a and the second light emitting unit 20b, which are a plurality of light emitting units, into the scanner 22. Injects light in one irradiation direction within the scanning range. At this time, when the reflected light RLA3 or RLB3 returning to the light receiving unit 30 is detected from a direction different from the irradiation direction, the control unit 50 temporarily stops the light emission of the light emitting unit corresponding to the irradiation light in the irradiation direction. do. The above detection is executed when it is determined by a recognition algorithm that the obtained target in the irradiation direction deviates from the shape of a person or an object registered in advance, and the probability of ghost exists in the corresponding direction above a certain level. NS. The irradiation light ILA1 and ILB1 from the first light emitting unit 20a and the second light emitting unit 20b, which are a plurality of light emitting units whose optical axes are parallel to each other, are irradiated by the scanner 22 onto a target existing in the same irradiation direction. At this time, since the light emitting portion that irradiates the irradiation light is temporarily stopped in the irradiation direction in which the ghost can exist according to the above determination, high reflection is obtained in a direction different from one irradiation direction, that is, in the irradiation direction in which the ghost can occur. Even if there is a target with a rate, the irradiation light does not hit the target with a high reflectance. As a result, ghosts do not occur, and it is possible to suppress erroneous recognition that a target with high reflectance exists in the irradiation direction. If the period from the timing when it is determined that the ghost can exist to the time when one of the light emitting parts is temporarily stopped and the distance is measured is sufficiently long, the target targeted for the ghost is the movement of the vehicle, etc. It is possible to predict that the light emitting part appears in a different irradiation direction depending on the irradiation direction, and temporarily stop one of the light emitting parts in the corresponding irradiation direction.

In the above embodiment, the rotation angle θ of the mirror 26 is
If less than θa
When it is θb or more and θc or less
If it is θd or more
In the case of any of the above, both the first light emitting unit 20a and the second light emitting unit 20b are emitting light. Generally, by emitting light from both the first light emitting unit 20a and the second light emitting unit 20b, the amount of light can be doubled and the SN ratio can be improved. If there is no highly reflective object in the irradiation direction of the irradiation lights ILA3 and ILB3, ghosts are unlikely to occur. That is, by lengthening the period in which both the first light emitting unit 20a and the second light emitting unit 20b emit light, it is possible to improve the SN ratio and suppress the occurrence of ghosts at the same time.

-Second embodiment:
FIG. 10 shows the distance lav between the irradiation lights ILA and ILB, the effective diameter lm of the mirror 26, and the distance dmw between the center of the surface 26s of the mirror 26 and the window 28 when the rotation angle θ of the mirror 26 is less than 45 °. It is explanatory drawing which shows the relationship with the occurrence of a ghost. The distance between the center of the surface 26s of the mirror 26 and the window 28 when the irradiation light ILA2 hits the end portion P1 of the mirror is dmw1. When the rotation angle θ of the mirror is less than 45 ° and the interval dmw is shorter than dmw1, the irradiation light ILA2 generated by the irradiation light ILA1 reflected by the window 28 hits the mirror 28 as shown by the alternate long and short dash line. On the other hand, when the interval dmw is longer than dmw1, as shown by the broken line, the irradiation light ILA2 generated by the irradiation light ILA1 reflected by the window 28 does not hit the mirror 28. Therefore, if the interval dmw is made longer than dmw1, ghosts do not occur.

Next, consider how to determine the effective diameter lm of the mirror 26 and the interval dmw. The effective diameter lm of the mirror 26 is such that when the angle θ of the mirror 26 is θst, which is the shallowest with respect to the irradiation light ILA and ILB, both the irradiation light ILA and ILB need to hit the mirror 26.
lm ≧ lab / sin θst
Can be decided to meet.

As shown in FIG. 10, the end portions of the mirror 26 are designated as points P1 and P4, and the midpoint of the mirror 26 is designated as a point Pc. Further, a line that divides the angle formed by the irradiation light ILA1 and the irradiation light ILA2 into two equal parts is drawn from the position where the irradiation light ILA1 hits the window 28, and the position where the line hits the mirror 26 is defined as the point P2. The position where the irradiation light ILA hits the mirror is defined as point P3. The distance lm1 is the distance between the points P1 and P2, the distance lm2 is the distance between the points P2 and P3, and the distance lm3 is the distance between the points P3 and P4. Further, lm4 is the distance between the point Pc and the point P3. The distances lm1 to lm3 are expressed as follows.
lm1 = [dmw1- (lm / 2) * sinθ] * tanφ
lm2 = [dmw1 + (lab / 2)] * tanφ
lm3 = (lm * cosθ) /2-lm4
Here, lm4 = (lab / 2) / tanθ
Therefore, lm3 is
lm3 = [(lm-lab / sinθ) * cosθ] / 2
Is shown.

As can be seen from FIG. 10, as the rotation angle θ of the mirror 26 approaches 45 °, the angle φ2 formed by the irradiation light ILA3 and the window 28 increases. Determine the allowable φ2, obtain the rotation angle θ1 corresponding to φ2, and set the distance dmw within the range of θ1 <45 °.
lm1 + lm2 + lm3 = lm * cosθ1
It may be larger than dmw1 that satisfies. That is,
[dmw1- (lm / 2) * sinθ1] * tanφ + [dmw1 + (lab / 2)] * tanφ + = [(lm-lab / sinθ1) * cosθ1] / 2 = lm * cosθ1
If it is made larger than dmw1 that satisfies the condition, the irradiation light ILA2 hits the mirror 26 and no ghost is generated. In addition, φ = 90-2θ1.

FIG. 11 shows the distance lav between the irradiation lights ILA and ILB, the effective diameter lm of the mirror 26, and the distance between the center of the surface 26s of the mirror 26 and the window 28 when the rotation angle θ of the mirror 26 is larger than 45 °. It is explanatory drawing which shows the relationship between dmw and occurrence of a ghost. The distance between the center of the surface 26s of the mirror 26 and the window 28 when the irradiation light ILB2 hits the end portion P5 of the mirror is dmw2. When the rotation angle θ of the mirror is larger than 45 ° and the interval dmw is shorter than dmw2, the irradiation light ILB2 generated by the irradiation light ILB1 reflected by the window 28 hits the mirror 28 as shown by the alternate long and short dash line. On the other hand, when the interval dmw is longer than dmw2, as shown by the broken line, the irradiation light ILB2 generated by the irradiation light ILB1 reflected by the window 28 does not hit the mirror 28. In FIG. 11, when points P5, P6, P7, P8, and lm5, lm6, and lm7 are defined in the same manner as in FIG. 10, lm5, lm6, and lm7 are represented as follows.
lm5 = [dmw + (lm / 2) * sinθ] * tanφ
lm6 = (dmw- (lab / 2) * tanφ
lm7 = [(lm-lab / sinθ) * cosθ] / 2
Here, in the range of θ> 45 °, the distance dmw is set.
lm5 + lm6 + lm7 = lm * cosθ
If it is made larger than dmw2 that satisfies the condition, the irradiation light ILB2 hits the mirror 26, and no ghost is generated. When θ> 45 °, even if the irradiation light ILB2 hits the mirror 26, the irradiation light ILB3 is reflected in the direction away from the window 28. Therefore, the irradiation light IBL3 does not hit the target, but the reflected light generated by the irradiation light IBL3 further hitting the object in the case 60 hits the target.

If the distance dmw is larger than the larger of dmw1 determined in FIG. 10 and dmw2 determined in FIG. 11, ghost generation is suppressed in the entire scan range.

As described above, according to the second embodiment, two or more irradiation lights from the first light emitting unit 20a and the second light emitting unit 20b, which are a plurality of light emitting units, in the same irradiation direction within the scanning range (−φ to φ). Corresponding to ILA and ILB, the effective diameter lm of the mirror 26 and the distance dmw between the mirror 26 and the window 28 are set so that two or more reflected lights returning to the light receiving unit 30 from a direction different from the irradiation direction are not detected. Since the adopted optical system 25 is arranged, it is possible to suppress the generation of ghosts due to the irradiation lights RLA3 and RLB3.

In the optical system 25 described in the second embodiment, the directions of two or more irradiation lights ILA and ILB from the first light emitting unit 20a and the second light emitting unit 20b are parallel to the window 28, and the mirror 26 reflects 45 °. The case of scanning in the range of −φ to + φ centered on the direction in which the light is generated has been described as an example. Even when the directions of the irradiation lights ILA and ILB are different, it is possible to obtain the effective diameter lm of the mirror 26 and the distance dmw between the mirror 26 and the window 28 in the same way.

-Third embodiment:
The hardware configuration of the third embodiment is the same as that of the first embodiment, but the scanning and the light emitting methods of the first light emitting unit 20a and the second light emitting unit 20b are different. Specifically, the control unit 50 emits the first light emitting unit 20a and the second light emitting unit 20b a plurality of times when the scanner 22 emits a plurality of irradiation lights ILA1 and ILB1 in one irradiation direction (θ). For a plurality of times of light emission, both the first light emitting unit 20a and the second light emitting unit 20b emit light independently, and both the first light emitting unit 20a and the second light emitting unit 20b emit light at the same time. The second case is included.

FIG. 12 is an explanatory diagram showing a light emitting sequence of the first light emitting unit 20a and the second light emitting unit 20b in the third embodiment. In the example shown in FIG. 12, the control unit 50 emits light only from the second light emitting unit 20b at time t1 with the rotation angle θ of the mirror 26 as θ11, and at time t2, the first light emitting unit 20a and the second light emitting unit 20a and the second light emitting unit. Both 20b are emitted. Next, the control unit 50 emits only the second light emitting unit 20b at time t3, and emits both the first light emitting unit 20a and the second light emitting unit 20b at time t4, with the rotation angle θ of the mirror 26 being θ12. do.

FIG. 13 is a graph showing the light receiving intensity of the light receiving unit 30 when the rotation angle θ of the mirror 26 is θ11. In FIG. 13, the case where only the first light emitting unit 20a is irradiated is shown as a reference. The horizontal axis of FIG. 13 is the distance between the optical ranging device 10 and the target. When only the second light emitting unit 20b emits light, one peak of the light receiving intensity appears at the distance d1. On the other hand, when both the first light emitting unit 20a and the second light emitting unit 20b emit light, another peak appears at the distance d2 in addition to the distance d1. Comparing the two, the peak at the distance d1 when both the first light emitting unit 20a and the second light emitting unit 20b emit light is from the target 200 when the irradiation lights ILA1 and ILB1 are directed in the desired direction. It can be determined that the light is caused by the reflected light RLA1 and RLB1. On the other hand, the peak at the distance d1 can be determined to be a peak caused by the reflected light RLA3, that is, a ghost, when the irradiation light RLA3 irradiated in a direction different from the desired direction hits the target 202 of the light reflectance. The distance calculation unit 48 compares the detection results of the light receiving unit 30 with the reflected light RLA1 and RLB1 returning to the light receiving unit 30 from the irradiation direction and the reflected light RLA3 returning to the light receiving unit 30 from a direction different from the irradiation direction. Can be determined and the distance to the target 200 can be calculated.

As described above, according to the third embodiment, the control unit 50 uses the first light emitting unit 20a and the second light emitting unit 20b, which are a plurality of light emitting units, when the scanner 22 emits the plurality of irradiation lights in one irradiation direction. In the first case where one of the plurality of light emitting units is made to emit light independently, and two or more of the first light emitting unit 20a and the second light emitting unit 20b are used for the multiple light emission. The distance calculation unit 48 compares the detection result of the light receiving unit 30 in the first case with the detection result of the light receiving unit 30 in the second case, and irradiates the light. The reflected light RLA1 and RLB1 returning to the light receiving unit 30 from the direction and the reflected light RLA3 returning to the light receiving unit 30 from a direction different from the irradiation direction are discriminated, and the distance to the target 200 is used by using the detection result in the second case. Can be calculated.

In the third embodiment, in the above description, the control unit 50 does not emit light from the first light emitting unit 20a but emits light from the second light emitting unit 20b in the first case. The first light emitting unit 20a may emit light, and the second light emitting unit 20b may not emit light.

In the third embodiment, in FIG. 14, the distance d2 corresponding to the ghost (target 202) is longer than the distance d1 corresponding to the target 200, but the distances d1 and d2 are the optical distance measuring device. Since it depends on the distances to the targets 200 and 202, the distance d2 may be shorter than the distance d1.

In each of the above embodiments, SPAD is used as the light receiving unit 30, and the distance calculation unit 48 superimposes the detection results along the elapsed time from the light emission timing of the first light emitting unit 20a and the second light emitting unit 20b, which are the light emitting units. Although the distance is detected using the combined histogram, it may be a light receiving part other than SPAD. For example, the distance may be detected by using the phase difference between the phase in light emission and the phase in light reception.

The present disclosure is not limited to the above-described embodiment, and can be realized by various configurations within a range not deviating from the gist thereof. For example, the technical features in the embodiments may be replaced or combined as appropriate to solve some or all of the above-mentioned problems, or to achieve some or all of the above-mentioned effects. Is possible. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

10 ... Optical distance measuring device, 20 ... Light emitting unit, 20a ... First light emitting unit, 20b ... Second light emitting unit, 22 ... Scanner, 24 ... Motor, 25 ... Optical system, 26 ... Mirror, 26o ... Mirror center, 26s ... Mirror surface, 28 ... window, 28a, 28e ... window edge, 28b ... position, 28c ... window center, 28d ... position, 30 ... light receiving part, 32 ... light receiving element, 32d ... avalanche photodiode, 32i ... Inverter circuit, 32r ... quenching resistor, 34 ... light receiving element array, 36 ... decoder, 40 ... measurement unit, 42 ... addition unit, 44 ... histogram generation unit, 46 ... peak detection unit, 48 ... distance calculation unit, 50 ... Control unit, 60 ... case, 100 ... vehicle, 200, 202, 204 ... target, 202g, 204g ... ghost

Claims (7)

Optical ranging device (10)
A plurality of light emitting parts (20a, 20b) having parallel optical axes housed in the case (60),
An optical system (25) including a mirror (26) that reflects a plurality of irradiation lights emitted by the plurality of light emitting units and a window (28) that transmits the plurality of irradiation lights reflected by the mirror to the outside is provided. A scanner (22) that scans a predetermined scanning range with the plurality of irradiation lights by changing the angle of the mirror, and
When the scanning range is scanned by the scanner with the plurality of irradiation lights, the light receiving unit (30) that detects the reflected light reflected by the target existing in the scanning range in the case.
A distance calculation unit (48) that calculates the distance to the target by using the light emission of the plurality of irradiation lights by the plurality of light emitting units and the detection of the reflected light from the target by the light receiving unit.
A control unit that controls the light emission of the plurality of light emitting units and the operation of the scanner, and the irradiation light from one of the plurality of light emitting units is emitted by the scanner in one irradiation direction within the scanning range. At a mirror angle at which the reflected light that has returned to the light receiving portion from a direction different from the one irradiation direction is detected when the light is emitted, the reflected light that has returned to the light receiving portion from a direction different from the one irradiation direction. A control unit (50) that temporarily stops the light emission of the corresponding light emitting unit, and
An optical ranging device equipped with. In the same irradiation direction within the scanning range, two or more reflected lights returning to the light receiving unit from a direction different from the one irradiation direction are detected corresponding to the two or more irradiation lights from the plurality of light emitting units. The optical ranging device according to claim 1, wherein the optical system is arranged so as not to be affected. The control unit is the control unit in the one irradiation direction of the plurality of irradiation lights by the scanner.
The light emitting unit in which the reflected light returned to the light receiving unit from a direction different from the one irradiation direction is detected is stopped.
The light emitting unit in which the reflected light returned to the light receiving unit from a direction different from the one irradiation direction is not detected is operated.
The optical ranging device according to claim 1 or 2. The control unit causes the plurality of light emitting units to emit light a plurality of times when the plurality of irradiation lights are emitted by the scanner in the one irradiation direction, and the plurality of light emitting units are among the plurality of light emitting units. Including a first case in which one of the light emitting units is emitted independently and a second case in which two or more of the plurality of light emitting units are emitted at the same time.
The distance calculation unit compares the detection result of the light receiving unit in the first case with the detection result of the light receiving unit in the second case, and reflects back from the one irradiation direction to the light receiving unit. The light and the reflected light returning to the light receiving portion from a direction different from the one irradiation direction are discriminated, and the distance to the target is calculated by using the detection result in the second case.
The optical ranging device according to any one of claims 1 to 3. The method according to any one of claims 1 to 4, wherein the distance calculation unit calculates the distance to the target from the elapsed time from the light emission by the plurality of light emitting units to the detection by the light receiving unit. Optical distance measuring device. The light receiving unit is a SPAD, and the light receiving unit is a SPAD.
The distance calculation unit calculates the distance to the target using a histogram in which the detection results along the elapsed time from the light emission timing of the plurality of light emitting units are superimposed.
The optical ranging device according to claim 5. When the control unit emits the irradiation light from one of the plurality of light emitting units into one irradiation direction within the scanning range by the scanner, the control unit receives the light from a direction different from the one irradiation direction. The optical ranging device according to any one of claims 1 to 6, further comprising a storage unit (52) that holds in advance the rotation angle of the mirror on which the reflected light returned to the unit is detected and the corresponding light emitting unit. ..

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