Optical detector

Abstract

The optical detector includes a light emitter (22) having a light emission window (23) extending in an extension direction (ED0) to emit a projection beam (PB) from the light emission window toward a measurement area (MA, MA1, MA2), and the optical detector detects a return beam (RB) from the measurement area. The optical detector includes a scanning mirror (34) for scanning by reflecting the projection beam. The scanning mirror swings around a rotation axis (33) in a limited angular range (AR, ARN, ARW), and the rotation axis is along a direction (ED1) corresponding to the extension direction.

Description

Technical Field

[0001] The present disclosure relates to optical detectors. Background Art

[0002] USP 9,470,520 describes an optical detector in which a scanning mirror scans a projection beam by rotating 360 degrees. Thus, a 360 degree circumference of the optical detector can be detected. Summary of the invention

[0003] However, in USP 9,470,520, scanning time may be wasted due to scanning an area that does not require detection or high detection accuracy. Due to such waste, the irradiance of the projection beam becomes insufficient for a specific area that requires detection or high detection accuracy. For a measurement target in a specific area, the detection accuracy may be low.

[0004] An object of the present disclosure is to provide an optical detector capable of achieving high detection accuracy.

[0005] According to one aspect of the present disclosure, an optical detector is configured to project a projection beam toward a measurement area and detect a return beam from the measurement area. The optical detector includes: a light emitter having a light emission window extending in an extension direction to emit a projection beam from the light emission window; and a scanning mirror that scans by reflecting the projection beam. The scanning mirror swings within a limited angular range around a rotation axis along a direction corresponding to the extension direction.

[0006] Therefore, the scanning of the projection beam by the scanning mirror is achieved by a swinging motion within a limited angular range. Since the scanning of areas that do not require detection or high detection accuracy is adjusted, the waste of scanning time can be suppressed. In addition, the light emission window for emitting the projection beam has a shape that is elongated in the extension direction, and the rotation axis used as a reference for the swinging motion is arranged along the extension direction. Therefore, a substantially long beam can be projected in a direction perpendicular to the swinging motion relative to a predetermined phase of the scanning mirror. That is, since the need for two-dimensional scanning including the extension direction is reduced, the scanning can be made more efficient. Therefore, the irradiation of the projection beam can be concentrated on a specific area, and the irradiance can be increased. Therefore, an optical detector capable of achieving high detection accuracy can be provided.

[0007] It should be noted that the reference numerals are merely illustrative of the corresponding relationship in the embodiments described below and are not intended to limit the technical scope. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a diagram showing the overall configuration of an optical detector.

[0009] Figure 2 is a diagram showing a light emitting portion.

[0010] Figure 3 It is a diagram for explaining the spot shape of the projection beam.

[0011] Figure 4 It is a diagram for explaining scanning by a scanning mirror.

[0012] Figure 5 is a diagram showing a positional relationship between a light projecting unit and a light receiving unit.

[0013] Figure 6 is a diagram showing the configuration of a detection unit.

[0014] Figure 7 is a block diagram showing a controller.

[0015] Figure 8 is a bird's-eye view showing roads and vehicles.

[0016] Fig. 9 is a diagram for explaining the swinging motion when the measurement area is at the front outer portion of the vehicle.

[0017] Fig.10 is a diagram for explaining the swinging motion when the measurement area is outside in the lateral direction of the vehicle.

[0018] Fig.11 is a flow chart executed by the decoder and the controller. DETAILED DESCRIPTION

[0019] The embodiments will be described with reference to the accompanying drawings.

[0020] (First Embodiment)

[0021] like Figure 1 As shown in , the optical detector 10 according to the first embodiment is a LiDAR (light detection and ranging / laser imaging detection and ranging) to be installed on a vehicle WC as a movable unit. For example, the optical detector 10 is arranged at the front, left / right, rear or roof of the vehicle WC. The optical detector 10 scans a projection beam PB toward a predetermined measurement area MA around the vehicle WC in an area outside the optical detector. The optical detector 10 detects a return beam (hereinafter referred to as a reflected beam RB), which is the projection beam PB reflected by the measured target. For the projection beam PB, light in the near-infrared region that is difficult for humans to visually recognize is generally selected.

[0022] The optical detector 10 can measure the measurement target by detecting the reflected beam RB. The measurement of the measurement target is, for example, the measurement of the distance from the optical detector 10 to the measurement target, the direction in which the measurement target exists, etc. In the optical detector 10 applied to the vehicle WC, typical measurement targets are pedestrians, cyclists, animals other than humans, movable objects such as other vehicles, and stationary objects such as guardrails, road signs, roadside structures, and objects on the road.

[0023] In the present embodiment, unless otherwise specified, the front, rear, up, down, left and right directions are defined with reference to the vehicle WC on a horizontal plane. In addition, the horizontal direction indicates a tangent direction relative to the horizontal plane, and the vertical direction indicates a vertical direction relative to the horizontal plane.

[0024] The optical detector 10 includes a housing 11, a light projecting unit 21, a scanning unit 31, a light receiving unit 41, and a controller 61. The housing 11 has a light shielding container 12 and a cover plate 15 and forms an outer portion of the optical detector 10.

[0025] The light shielding container 12 is made of, for example, a synthetic resin or a metal, and is formed in a box shape having an outer wall 12a with a light shielding property. The light shielding container 12 may be configured by one component, or may be configured by combining a plurality of components. The light shielding container 12 includes a storage chamber 13 surrounded by an outer wall 12a to accommodate a light projection unit 21, a scanning unit 31, a light receiving unit 41, and a controller 61. The storage chamber 13 is generally configured for the light projection unit 21 and the light receiving unit 41, and one storage chamber is provided in the present embodiment. Since the storage chamber 13 is shared by the light projection unit 21 and the light receiving unit 41, the partition wall between the light projection unit 21 and the light receiving unit 41 can be eliminated. Therefore, the size increase of the optical detector 10 can be suppressed.

[0026] The light shielding container 12 has an opened optical window 14, through which both the projection beam PB and the reflection beam RB move back and forth in a straight line between the containing chamber 13 and the measuring area MA. The optical window 14 is provided in common to both the light projection unit 21 and the light receiving unit 41, and one optical window is provided in the present embodiment.

[0027] The cover plate 15 is a member capable of forming both the transmission beams PB and RB in a plate shape (eg, a flat plate shape) and is made of a base material such as synthetic resin or glass. The cover plate 15 is arranged to cover the entire optical window 14 and blocks foreign matter from entering the housing chamber 13 from the outside.

[0028] The cover plate 15 transmits light in the near-infrared region by coloring the substrate, forming an optical thin film, or attaching a film to the surface of the substrate. In addition, it is preferred to have a wavelength dependency of the transmittance that shields visible light to prevent the interior of the receiving chamber 13 from being seen from the outside. The mirror-like surface of the substrate may be exposed from the surface of the cover plate 15 facing the receiving chamber 13 and / or the surface of the cover plate 15 facing the measurement area MA. An anti-reflection film or a moth-eye structure may be provided on the surface of the cover plate 15 facing the receiving chamber 13 and / or the surface of the cover plate 15 facing the measurement area MA.

[0029] For example, the cover plate 15 may have a flat plate shape. In this case, the accuracy of detecting the position of the measurement target can be improved by suppressing the angle variation caused by the refraction of the projection beam PB passing through the cover plate 15 and the angle variation caused by the refraction of the reflection beam RB.

[0030] The light projection unit 21 includes a light emitting unit 22, a projection optical system 26, and a projection holding member 28. Figure 2 As shown in , the light emitting unit 22 has a plurality of laser oscillation elements 24 arranged in an array along the extension direction ED0 so as to form a light emission window 23 elongated along the extension direction ED0. The light emitting unit 22 uses a plurality of laser oscillation elements 24 to increase the total output of the laser. The light emitting unit 22 projects a projection beam PB from the light emission window 23 at the light emission timing in response to an electrical signal from the controller 61.

[0031] Each of the laser oscillation elements 24 can be, for example, a laser diode (LD). Each of the laser oscillation elements 24 has a structure in which a P-type semiconductor and an N-type semiconductor are bonded to each other via a PN junction layer, and a resonator structure that resonates light generated in the PN junction layer. In the resonator structure, the PN junction layer is arranged between mirrors, and one of the mirrors forms a half-mirror small window 25. Each of the laser oscillation elements 24 can emit laser light as coherent light in a beam state through the small window 25. The laser light is a small beam that forms a part of the projection beam PB. In the present embodiment, a group of beamlets oscillated from each of the small windows 25 is defined as a projection beam PB. The PN junction layer of each laser oscillation element 24 is arranged in a direction perpendicular to the arrangement direction of the small window 25 (i.e., the extension direction ED0). The axis along the vertical direction is the fast axis FA of the laser diode.

[0032] A plurality of small windows 25 are arranged as close to each other as possible to form the light emission window 23 as a macroscopic opening formed by an aggregate of the small windows 25. The light emission window 23 of the present embodiment has a substantially rectangular shape. The size of the light emission window 23 in the extension direction ED0 is set to, for example, 100 times or more of the size in the direction perpendicular to the extension direction ED0 (the direction along the fast axis FA).

[0033] When the optical detector is mounted on a vehicle in a general form, the extension direction ED0 of the light emission window 23 is along the vertical direction. When the optical detector is mounted on a vehicle, the fast axis FA is along the horizontal direction.

[0034] Each of the laser oscillation elements 24 oscillates the linear polarized light in the TE mode so that the polarization direction of the laser beam is common and along the extension direction ED0. Then, since the polarization direction of the projection beam PB is along the vertical direction in the vehicle-mounted state, the projection beam PB can be incident on the road surface in a vertical polarization direction substantially in the horizontal direction. Therefore, the conventional reflectivity is reduced and the diffuse reflectivity is increased. Therefore, when it rains or freezes, the reflected beam RB can easily return from the road surface to the optical window 14.

[0035] The projection beam PB oscillates in a short pulse manner. The corresponding small beams emitted from each of the laser oscillation elements 24 may oscillate substantially simultaneously, or may oscillate sequentially with a slight time difference. The projection beam PB travels to the measurement area MA via the projection optical system 26 and the scanning mirror 34 of the scanning unit 31.

[0036] The projection optical system 26 collects and projects the projection beam PB emitted from the light emitting unit 22. The projection optical system 26 is arranged between the light emitting unit 22 and the scanning mirror 34. The projection optical system 26 includes at least one optical lens 27. The projection optical system 26 forms a projection optical axis POA. The projection optical axis POA is defined as, for example, an axis along an imaginary ray that passes through the center of curvature of the corresponding refractive surface of the optical lens 27. The imaginary ray along the projection optical axis POA can pass through the projection optical system 26 by passing straight through each lens vertex 27a without deflection. In the present embodiment, the main ray of the projection beam PB emitted from the center point of the light emission window 23 is along the projection optical axis POA. When the center point of the light emission window 23 is located in the gap between the small windows 25, the main ray of the projection beam PB is an imaginary ray in the optical design. When the light beam along the projection optical axis POA is deflected by the scanning unit 31, the projection optical axis POA is also defined as including an extension portion along the deflection direction.

[0037] The focal length of the projection optical system 26 is substantially equal to the distance from the principal point of the projection optical system 26 to the light emission window 23 along the projection optical axis POA. Figure 3As shown in , the projection optical system 26 collimates the projection beam PB emitted from the light emission window 23. The distance Dp from the light emission window 23 along the projection optical axis POA is infinite (Dp=∞) at the following position: a point conjugated with the light emission window 23 on the opposite side of the light emission window 23, outside the accommodation chamber 13, through the projection optical system 26 on the optical path. The spot shape of the projection beam PB at infinity is the far-field pattern FFP. An image corresponding to the light emission window 23 is formed at infinity, but the image is more affected by diffraction in the extension direction ED0 than the near-field pattern NFP. Therefore, the spot shape of the projection beam PB at infinity has a line shape in which each small beam is elongated, for example, along the extension direction ED0, while leaving gaps between the small windows in the light emission window 23. Alternatively, since the gaps between the small windows 25 in the light emission window 23 are substantially eliminated, the spot shape of the projection beam PB at infinity has a line shape in which the small beams are integrated and elongated along the extension direction ED0.

[0038] In the accommodation chamber 13 at a small distance Dp from the light emission window 23, the spot shape of the projection beam PB is a near-field pattern NFP. This spot shape is less affected by diffraction in the extension direction of the fast axis FA than the far-field pattern FFP. In this spot shape, small spots SS corresponding to the corresponding small beams can be identified respectively. Each small spot SS has an elliptical pattern in which the fast axis FA corresponds to the long axis. The small spots SS can be completely separated from each other, or can partially overlap each other.

[0039] The extent of the footprint PF of the projection beam PB can be defined by the light emission window 23 acting as a substantial aperture, while the image formation mode is adjusted by the projection optical system 26. The projection optical axis POA penetrates the center point of the light emission window 23. Alternatively, the extent of the footprint PF can be defined by providing an aperture in the projection optical system 26, the center point of which the projection optical axis POA penetrates. In the present embodiment, the footprint means the space that can be covered by the beam trajectory that contributes to the measurement.

[0040] Figure 4 and Figure 5 The projection holding member 28 shown in FIG. 2 is formed in a tubular shape that holds one or more optical lenses 27 of the projection optical system 26. The projection holding member 28 is formed of, for example, a synthetic resin or metal to have a light shielding property as a lens barrel of the projection optical system 26. The projection holding member 28 may be formed to also hold the light emitting unit 22.

[0041] like Figure 1 and Figure 4As shown in , the scanning unit 31 includes a driving motor 32 and a scanning mirror 34. The driving motor 32 can be, for example, a voice coil motor, a brushed DC motor, a stepping motor, etc. The driving motor 32 drives the rotating shaft 33 mechanically coupled to the scanning mirror 34 at a certain rotation amount and rotation speed in response to an electrical signal from the controller 61. The rotating shaft 33 is arranged along an extension corresponding direction ED1 corresponding to the extension direction ED0 of the light emission window 23. When the light emission window 23 is virtually projected onto an object on the optical path (e.g., a reflective surface 36 of the scanning mirror 34) along the projection optical axis POA, the projection of the light emission window 23 on the object (e.g., on the reflective surface 36) is along the extension corresponding direction ED1. In the present embodiment, the rotating shaft 33 is substantially consistent with the extension direction ED0 of the light emission window 23.

[0042] The scanning mirror 34 is capable of reflecting and scanning the projection beam PB. The scanning mirror 34 has a main body 35 and a reflecting surface 36. The scanning mirror 34 is mechanically coupled to the rotation shaft 33, and is formed with a flat plate made of, for example, a synthetic resin. The reflecting surface 36 is formed as a mirror surface, for example, by depositing a metal film such as aluminum on one surface of the main body 35. The reflecting surface 36 is, for example, flat, and extends in a direction parallel to the rotation shaft 33 so as to include an extending corresponding direction ED1.

[0043] The reflecting surface 36 is commonly provided to both of the beams PB and RB. The reflecting surface 36 is formed in a rectangular shape whose length direction substantially coincides with the extending corresponding direction ED1. Figure 3 As shown in , the reflective surface 36 is arranged at a position where the spot shape of the projection beam PB forms a near field pattern NFP (Dp=Ds). That is, each small spot SS of the projection beam PB on the reflective surface 36 has an elliptical shape corresponding to the short axis in the extension corresponding direction ED1. Therefore, compared with the aspect ratio of the light emission window 23 having an elongated shape and the line-shaped spot at infinity, the aspect ratio of the projection beam PB on the reflective surface 36 is compressed in the extension corresponding direction ED1. Since the coverage area PF of the projection beam PB is also compressed in the extension corresponding direction ED1, the size of the scanning mirror 34 in the extension corresponding direction ED1 is shortened.

[0044] like Figure 4 As shown in FIG. 1 , the scanning mirror 34 can be swung within a limited angular range AR relative to a rotation axis 33 parallel to the extension corresponding direction ED1. The reflection angle of the projection beam PB reflected by the reflection surface 36 also changes due to the swung movement according to the orientation change of the reflection surface 36. The projection beam PB toward the measurement area MA is scanned in time and space.

[0045] The scanning in the present embodiment means one-dimensional scanning, in which the scanning in the extension corresponding direction ED1 is omitted. The spot shape of the projection beam PB reflected by the reflection surface 36 at infinity basically corresponds to the illumination range of the projection beam PB in the swing motion stage. In the vehicle-mounted state, the illumination range is elongated in the vertical direction. Therefore, even if the scanning mirror 34 does not perform scanning corresponding to the vertical direction, the vertical viewing angle in the measurement area MA can be expanded.

[0046] The illumination range of the projection beam PB elongated in the vertical direction is moved by a swinging motion in a direction perpendicular to the extension corresponding direction ED1, that is, in the horizontal direction. The limited angular range AR in the swinging motion defines the horizontal viewing angle in the measurement area MA. A portion of the projection optical axis POA between the scanning mirror 34 and the measurement area MA swings in the horizontal direction according to the swinging motion of the scanning mirror 34. However, the direction and position of the portion of the projection optical axis POA between the scanning mirror 34 and the measurement area MA are uniquely determined relative to the predetermined phase of the swinging motion (in other words, the predetermined orientation of the reflection surface 36).

[0047] The limited angle range AR is limited by a mechanical stopper, an electromagnetic stopper or by controlling a driving mechanism. The reflection angle of the projection beam PB is maximum at the end AR1 within the maximum limited angle range AR. The end AR1 is arranged so that the projection beam PB reflected by the scanning mirror 34 avoids deviating from the optical window 14 and avoids interference with the light shielding container 12.

[0048] The reflection angle of the projection beam PB is minimum at the end AR2 within the maximum limited angle range AR. The end AR2 is set so as to prevent the projection beam PB reflected by the scanning mirror 34 from interfering with the light projection unit 21. The corner of the projection holding member 28 facing the optical window 14, at which the projection beam PB is emitted, has a concave portion 29 that is recessed toward the projection optical axis POA that penetrates the projection optical system 26. The coverage area PF of the projection beam PB reflected by the scanning mirror 34 enters the space formed by the concave portion 29. Therefore, in the case where the reflection angle of the projection beam PB is minimum within the limited angle range AR, the settable range of the end AR2 can be expanded.

[0049] The projection beam PB scanned within a limited angular range AR passes through the optical window 14. Figure 3As shown in , the optical window 14 is arranged at a position where the spot shape of the projection beam PB forms a near field pattern NFP (Dp=Dw). That is, each small spot SS of the projection beam PB on the reflection surface 36 has a smaller ellipticity than each small spot on the reflection surface 36 (i.e., close to a circle), and the elliptical shape has a short axis along the extension corresponding direction ED1. Therefore, compared with the aspect ratio of the elongated light emission window 23 and the line-shaped spot at infinity, the aspect ratio of the coverage area PF of the projection beam PB on the optical window 14 is compressed in the extension corresponding direction ED1. Therefore, the size of the optical window 14 in the extension corresponding direction ED1 can be shortened.

[0050] The projection beam PB is transmitted through the optical window 14 and then reflected by the measurement target object present in the measurement area MA. The reflected beam RB, which is the projection beam PB reflected by the measurement target object, passes through the optical window 14 again and enters the scanning mirror 34. The speeds of the projection beam PB and the reflected beam RB are sufficiently higher than the speed of the swinging motion of the scanning mirror 34. Therefore, the difference between the phase of the swinging motion when the projection beam PB is reflected by the scanning mirror 34 and the phase of the swinging motion when the reflected beam RB is incident on the scanning mirror 34 is slight and can be ignored. Therefore, the reflected beam RB is reflected at a reflection angle substantially the same as that of the projection beam PB, and is guided to the light receiving unit 41 to travel in the opposite direction to the projection beam PB.

[0051] like Figure 1 and Figure 5 As shown in FIG. 4 , the light receiving unit 41 includes a detection unit 42, a receiving optical system 49, and a light receiving holding member 51. Figure 6 As shown in , the detection unit 42 in this embodiment has a light receiving element array 43 and a decoder 46. The light receiving element array 43 has a plurality of light receiving elements 44 arranged in an array. Single photon avalanche photodiode (SPAD) light receiving elements are used as the light receiving elements 44. The light receiving elements 44 are two-dimensionally arranged on a rectangular detection surface 45 in a highly integrated state. Note that Figure 6 Only some of the light receiving elements 44 shown in FIG. 4 are denoted by reference numerals.

[0052] The length direction of the detection surface 45 is aligned with the extension direction ED0 of the light emission window 23. The reflected beam RB corresponding to the projection beam PB which is a straight line at infinity can also be a straight line beam. The detection surface 45 has a shape that matches the dispersion of the reflected beam RB. Therefore, the detection unit 42 can effectively receive the reflected beam RB and improve the detection accuracy.

[0053] When one or more photons are incident, each SPAD light receiving element 44 generates an electrical pulse through the electron multiplication operation of avalanche doubling (so-called Geiger mode). That is, each light receiving element 44 can directly generate an electrical pulse as a digital signal without using an AD conversion circuit from an analog signal to a digital signal. Therefore, the detection result of the reflected beam RB focused on the detection surface 45 via the receiving optical system 49 can be read at high speed.

[0054] The decoder 46 is configured to output the electrical pulse generated by the light receiving element 44, and includes a selection circuit 47 and a clock oscillator 48. The selection circuit 47 is installed in the form of, for example, an integrated circuit, and sequentially selects the light receiving element 44 from which the electrical pulse is output among the light receiving element array 43. The selected light receiving element 44 outputs the electrical pulse to the controller 61. In this way, when the selection circuit 47 completes the selection of the light receiving element 44 to output once each time, one sampling is completed. The selection circuit 47 periodically repeats sampling starting from the time when the projection beam PB is emitted at a predetermined emission timing. The sampling period corresponds to the clock frequency output from the clock oscillator 48. The clock oscillator 48 is provided inside or outside the integrated circuit of the selection circuit 47.

[0055] like Figure 1 and Figure 5 As shown in , the receiving optical system 49 receives the reflected beam RB and focuses the reflected beam RB on the detection surface 45. The receiving optical system 49 is arranged between the detection unit 42 and the scanning mirror 34. The receiving optical system 49 includes one or more optical lenses 50. The diameter of the optical lens 50 of the receiving optical system 49 is made larger than the diameter of the optical lens 27 of the projection optical system 26. In this way, the efficiency of collecting the reflected beam RB by the receiving optical system 49 can be improved. The receiving optical system 49 forms a receiving optical axis ROA. The receiving optical axis ROA is defined as, for example, along the following imaginary light, which passes through the center of curvature of each refractive surface of one or more optical lenses 50. The imaginary light along the receiving optical axis ROA can pass through the receiving optical system 49 by traveling straight through each lens vertex 50a without deflection. In the present embodiment, the main light of the reflected light RB incident on the center point of the detection surface 45 is along the receiving optical axis ROA. The main light of the reflected beam RB can be a virtual light depending on the reflection mode of the measurement target object to the projection beam PB. When the light beam along the receiving optical axis ROA is deflected by the scanning unit 31 , the receiving optical axis ROA is also defined to include an extension along the deflection direction.

[0056] A portion of the receiving optical axis ROA between the measuring area MA and the scanning mirror 34 swings in the horizontal direction in the vehicle-mounted state according to the swinging motion of the scanning mirror 34. However, the direction and position of the portion of the receiving optical axis ROA between the measuring area MA and the scanning mirror 34 are uniquely determined relative to a predetermined phase of the swinging motion.

[0057] When the receiving optical axis ROA penetrates the center point, the range of the coverage area RF of the reflected beam RB received by the receiving optical system 49 can be defined by the detection surface 45 used as a substantial aperture. Alternatively, when the receiving optical axis ROA penetrates the center point, the range of the coverage area RF can be defined by providing an aperture in the receiving optical system 49.

[0058] Figure 5 The light receiving holding member 51 shown in FIG. 4 is formed as a lens barrel of the receiving optical system 49. The light receiving holding member 51 is formed in a tubular shape to hold one or more optical lenses 50 of the receiving optical system 49, and is made of, for example, a synthetic resin or metal to have a light shielding property. The light receiving holding member 51 may be formed to also hold the detection unit 42.

[0059] like Figure 1 and Figure 5 As shown in , the projection optical axis POA and the reception optical axis ROA are offset from each other in the entire area outside the accommodation chamber 13 and inside the accommodation chamber 13. Specifically, the projection optical axis POA and the reception optical axis ROA are arranged to be substantially parallel to each other with a gap therebetween and along a common direction. The utilization efficiency of the projection beam PB and the reflection beam RB can be improved by arranging the projection optical axis POA and the reception optical axis ROA in a direction perpendicular to the rotation axis 33.

[0060] The positional relationship between the projection optical axis POA and the reception optical axis ROA in the region between the measurement region MA and the scanning mirror 34 is also uniquely determined by the orientation of the reflection surface 36 common to the beams PB and RB. Regardless of the phase of the swinging motion, the mutually offset form (specifically, the parallel arrangement form) is maintained.

[0061] The projection optical system 26 and the receiving optical system 49 are arranged side by side in the direction along the rotation axis 33 for the swinging motion, that is, along the extension direction ED0 of the light emission window 23. Then, the receiving optical system 49 can effectively receive the reflected beam RB reflected by the common reflecting surface 36 at a reflection angle substantially the same as that of the projection beam PB.

[0062] Due to the arrangement of the projection optical system 26 and the receiving optical system 49, it is possible to suppress the projection beam PB from interfering with the light receiving holding member 51 and suppress the reflected beam RB from interfering with the projection holding member 28. In addition, as a result of adjusting the distance from the scanning mirror 34 to the projection optical system 26 and the distance from the scanning mirror 34 to the receiving optical system 49, the size of the accommodating chamber 13 can be reduced in a common direction along the optical axes POA, ROA.

[0063] In the vehicle-mounted state, the receiving optical system 49 is arranged to be lower than the projection optical system 26. Since the diameter of the optical lens 50 is larger than the diameter of the optical lens 27 of the projection optical system 26, the weight of the receiving optical system 49 or the light receiving unit 41 is larger than the weight of the projection optical system 26 or the light projection unit 21. Therefore, the center of gravity of the optical detector 10 can be lowered downward, and the installation stability of the optical detector 10 in the vehicle can be improved.

[0064] like Figure 1 As shown in , the coverage area PF of the projection beam PB increases with the cross-sectional area perpendicular to the projection optical axis POA as it travels from the projection optical system 26 toward the measurement area MA on the projection optical axis POA. Due to the scanning by the scanning mirror 34, the horizontal expansion width of the cross-sectional area of ​​the coverage area PF increases in the area between the measurement area MA and the scanning mirror 34 relative to the area between the projection optical system 26 and the scanning mirror 34.

[0065] Similarly, the coverage area RF of the reflected beam RB increases in cross-sectional area perpendicular to the receiving optical axis ROA as it travels from the receiving optical system 49 toward the measuring area MA on the receiving optical axis ROA. Due to the scanning by the scanning mirror 34, the horizontal expansion width of the cross-sectional area of ​​the coverage area RF increases in the area between the measuring area MA and the scanning mirror 34 relative to the horizontal expansion width of the cross-sectional area of ​​the coverage area RF in the area between the receiving optical system 49 and the scanning mirror 34. The horizontal expansion width means the increase in the cross-sectional area of ​​the coverage area per unit length along the optical axis in the horizontal direction.

[0066] An overlap OL where the coverage area PF of the projection beam PB and the coverage area RF of the reflection beam RB overlap each other is formed inside the accommodation chamber 13. Compared with a comparative structure in which the coverage areas PF and RF are completely separated from each other, the size of the accommodation chamber 13 can be reduced by the volume of the overlap OL in the present embodiment in which the overlap OL is provided.

[0067] In the present embodiment, the coverage area PF of the projection beam PB and the coverage area RF of the reflection beam RB partially overlap each other on the reflection surface 36 of the scanning mirror 34. Specifically, the coverage areas PF and RF overlap each other on the cross section of the reflection surface 36 including the direction along the rotation axis 33. Therefore, the size of the reflection surface 36 along the extension corresponding direction ED1 can be reduced. Therefore, the size of the scanning mirror 34 or the accommodation chamber 13 can be reduced.

[0068] The controller 61 controls the measurement in the measurement area MA and controls the swinging motion of the scanning mirror 34. Figure 1 As shown in , the controller 61 has a computer including a processing unit 62, a RAM 63, a storage unit 64, an input / output interface 65, and a bus connecting them. The processing unit 62 is hardware for arithmetic processing and is combined with the RAM 63. The processing unit 62 includes at least one arithmetic core, such as a CPU (central processing unit), a GPU (graphics processing unit), and a RISC (reduced instruction set computer). The processing unit 62 may include at least one arithmetic core, such as an FPGA (field programmable gate array) and an ASIC (application-specific integrated circuit). The processing unit 62 performs various processes for implementing the functions of each functional unit described later by accessing the RAM 63. The storage unit 64 includes at least one non-volatile storage medium. The program executed by the processing unit 62 is stored in the storage unit 64.

[0069] The controller 61 is electrically connected to the light emitting unit 22, the driving motor 32, and the detecting unit 42 or can communicate wirelessly with the light emitting unit 22, the driving motor 32, and the detecting unit 42. Figure 7 As shown in , the controller 61 has functional units such as a light emission control unit 66 , a scanning control unit 67 , and a measurement calculator 68 .

[0070] The light emission control unit 66 outputs an electric signal to the light emission unit 22 so that each laser oscillation element 24 emits the projection beam PB at the light emission timing associated with the scanning performed by the scanning mirror 34 .

[0071] The scanning control unit 67 outputs an electrical signal to the drive motor 32, so that scanning associated with the light emission timing of the projection beam PB is achieved. In the present embodiment, in the reciprocating movement in the swinging motion within the limited angular range AR, the speed is precisely controlled in the forward path starting from the initial phase. In cooperation with such precise speed control, the light emission control unit 66 continuously emits a short pulse projection beam PB, and the projection beam is scanned. In the return path of the reciprocating movement, the scanning mirror 34 rebounds to the initial phase at a speed higher than the speed in the forward path. During this time period, the light emission control unit 66 stops emitting the projection beam PB. The necessity of changing the processing between the forward path and the return path of the swinging motion in the measurement calculation of the measurement target object can be reduced by performing the scanning of the projection beam PB in only one direction of the reciprocating movement. Therefore, the processing can be performed at high speed, or computer resources can be saved.

[0072] The scanning control unit 67 causes the scanning mirror 34 to continuously reciprocate a plurality of times in a short time. The projection beam PB is strongly emitted in each forward path.

[0073] In addition, the scanning control unit 67 of the controller 61 of the present embodiment can change the limited angular range AR and / or the speed HS, LS of the swinging motion, for example, by storing the swinging adjustment parameters, such as the value of the angular range AR and the value of the speed HS, LS or the parameters that assign an electrical signal to the drive motor 32 for controlling the swinging motion to meet these values, in the storage medium of the storage unit 64. The scanning control unit 67 reads the swinging adjustment parameters by accessing the storage unit 64, and controls the limited angular range AR and the speed HS, LS of the swinging motion.

[0074] In the present embodiment, a plurality of swing adjustment parameters are stored in the storage unit 64 respectively corresponding to the vehicle-mounted conditions of the optical detector 10. The scanning control unit 67 selects an appropriate swing adjustment parameter from the swing adjustment parameters by reading out the setting information of the vehicle-mounted conditions stored in the storage unit 64 or acquiring the setting information of the vehicle-mounted conditions from an external device.

[0075] For example, Figure 8 As shown in , the measurement area MA1 can be limited to the front outer part of the vehicle WC by the optical detector 10. In this case, the travel lane of the vehicle WC is very likely to correspond to the central part of the measurement area MA1. Therefore, for example, in order to measure the inter-vehicle distance relative to another vehicle TC1 located on the front side, the measurement accuracy at a relatively far range FR is required. In the side part of the measurement area MA1, for example, in order to measure a building BLD, a cyclist BYC, a pedestrian on the roadside, or another vehicle TC2 in the adjacent lane, the measurement accuracy at a relatively close range NR is required.

[0076] In this vehicle-mounted situation, if Fig. 9 As shown in , the scanning control unit 67 sets the speed LS of the swinging motion in the central part ARc of the limited angular range AR to be lower than the speed HS of the swinging motion in the side part ARs. Therefore, the retention time per unit angle in the swinging motion is longer in the central part ARc than in the side part ARs. Then, the projection beam PB can be irradiated to the angle corresponding to the central part ARc with high irradiance (light density) by using the long retention time of the central part ARc. Since the projection beam PB is sufficiently supplied to the far range FR in the central part of the measuring area MA1, a sufficient amount of the reflected beam RB reflected on the far range FR and incident on the detection surface 45 is also obtained. In addition, the scanning control unit 67 can set the limited angular range AR to a relatively narrow angular range ARN compared to the measuring area MA2 described later. The retention time per unit angle in the central part ARc can also be extended.

[0077] In contrast, Figure 8 As shown in , the measurement area MA2 can be formed by the optical detector 10 in the lateral outside (for example, the left outside or the right outside) of the vehicle WC. In this vehicle-mounted case, in the central part of the measurement area MA2, for example, in order to measure the building BLD adjacent to the road, the cyclist BYC, the pedestrian, and the other vehicle TC2 in the adjacent lane, the measurement accuracy of the relatively close range NR is required. Even in the side part of the measurement area MA2, the building BLD on the road side, the cyclist BYC, the pedestrian, and the other vehicle TC2 in the adjacent lane are also measurement targets. In this case, the measurement target is positioned diagonally in front or behind. Therefore, the measurement accuracy of the far range FR is relatively required.

[0078] In this vehicle-mounted situation, if Fig.10 As shown in , the scanning control unit 67 sets the speed HS of the swinging motion in the central part ARc of the limited angular range AR to be higher than the speed LS of the swinging motion in the side part ARs. Therefore, the retention time per unit angle in the swinging motion is longer in the side part ARs than in the central part ARc. Then, the projection beam PB can be irradiated to the angle corresponding to the side part ARs with high irradiance (light density) by using the long retention time of the side part ARs. Since the projection beam PB is sufficiently supplied to the long range FR in the side part of the measurement area MA2, a sufficient amount of the reflected beam RB reflected by the long range FR and incident on the detection surface 45 can be obtained. In addition, the scanning control unit 67 can set the limited angular range AR to an angular range ARW that is relatively wider than the measurement area MA1, because it is not necessary to measure the measurement target object located in an area relatively far outside the vehicle WC laterally.

[0079] In the present embodiment, the side portion ARs is defined as a pair of areas in contact with both ends of the limited angular range AR, ARN, ARW divided into three equal areas. The central portion ARc is defined as an area sandwiched by a pair of side portions ARs of the limited angular range AR, ARN, ARW divided into three equal areas. The speeds HS, LS are not limited to constant speeds and can be accelerated or decelerated. The comparison of the speeds between the central portion ARc and the side portions ARs is a comparison between the average speed at the central portion ARc and the average speed at the side portions ARs. When the swinging motion has a constant cycle, the retention time per unit angle in the swinging motion can be standardized to the time period of each cycle of the swinging motion. The retention time per unit angle in the swinging motion can be the integral time of multiple swinging motions at different times in the cycle among multiple swinging motions.

[0080] The measurement calculator 68 performs arithmetic processing on the electric pulses input from the detection unit 42 to detect the presence / absence of the measurement target object in the measurement area MA and measure the distance to the measurement target object. The measurement calculator 68 counts the number of electric pulses output from each of the light receiving elements 44 in each sampling after the emission of the projection beam PB. The measurement calculator 68 generates a histogram in which the number of electric pulses for each sampling is recorded in each category. The categories of the histogram show the flight time of light from the emission of the projection beam PB to the incidence of the reflected beam RB on the light receiving element 44, i.e., TOF (time of flight). The sampling period of the decoder 46 corresponds to the time resolution in the TOF measurement.

[0081] The measurement calculator 68 generates a histogram of a plurality of phase regions obtained by dividing the limited angular range AR according to the reciprocating movement of the scanning mirror 34 and the emission of the projection beam PB from the initial position on the forward path. The histogram corresponding to each phase region is temporarily or non-temporarily stored in the RAM 63 or the storage unit 64.

[0082] In the present embodiment, when the scanning mirror 34 passes through a phase region in the forward path starting from an initial position of a swinging motion, the light emission control unit 66 emits the projection beam PB multiple times with periodic light emission timing. The number of times the projection beam PB is emitted for the phase region where the speed of the swinging motion is low can be increased compared to the phase region where the speed is high.

[0083] In contrast, the measurement calculator 68 of the present embodiment integrates the histogram of each phase region having an electric pulse generated by detecting the reflected beam RB corresponding to the multiple transmissions of the projection beam PB in each phase region. After multiple integrations, the measurement calculator 68 calculates the TOF corresponding to the category with the highest frequency in the histogram as a measurement result. The distance to the measurement target object can be specified by converting the TOF into a distance. The TOF measurement accuracy and the distance measurement accuracy can be improved by multiple integrations.

[0084] Next, we will refer to Fig.11 The flowchart of describes a method of measuring a target object performed by the decoder 46 and the controller 61. For example, each time the scanning mirror 34 passes through one phase region, the processing configured by each step in the flowchart is performed.

[0085] In S11, the measurement calculator 68 identifies the phase region into which the scanning mirror 34 has entered, and selects the histogram corresponding to the phase region alone, ie, the histogram to be integrated and counted. After the processing in S11, the processing shifts to S12.

[0086] In S12, light emission control unit 66 causes projection beam PB to be emitted. After the processing in S12, the processing shifts to S13.

[0087] In S13, the decoder 46 and the measurement calculator 68 count the electric pulses of the light receiving element 44. The count is not reset until the TOF is calculated, and is integrated. After the processing in S13, the processing shifts to S14.

[0088] In S14, measurement calculator 68 increments a counter stored in, for example, RAM 63 to count the number of times projection beam PB is emitted. After the processing in S14, the processing transfers to S15.

[0089] In S15, the measurement calculator 68 determines whether the number of times the projection beam PB has been emitted reaches a prescribed number of times. The prescribed number of times is set to correspond to the transit time of the scanning mirror 34 through the phase region under measurement. When a negative determination is made in S15, the process returns to S12. When an affirmative determination is made in S15, the process proceeds to S16.

[0090] In S16, the measurement calculator 68 calculates TOF from the histogram recording the integration result. In addition, TOF is converted into distance, thereby specifying the distance to the measurement target object. After S16, a series of processing ends.

[0091] In the first embodiment, the decoder 46 of the detection unit 42 and the processing unit 62 of the controller 61 correspond to “at least one processor.” Furthermore, the cover plate 15 corresponds to a “cover member.”

[0092] The operation and effects of the first embodiment will be described below.

[0093] According to the first embodiment, scanning of the projection beam PB is achieved by the swinging motion of the scanning mirror 34 within a limited angular range AR. Since the scanning of the area that does not need to be detected or has high detection accuracy is adjusted, the waste of scanning time can be suppressed. The light emission window 23 for emitting the projection beam PB has a shape that is elongated in the extension direction ED0. The rotation axis 33 used as a reference for the swinging motion is arranged to extend in the direction ED1 along the extension direction ED0. Therefore, a substantially long beam can be projected in a direction perpendicular to the swinging motion relative to a predetermined phase of the scanning mirror 34. That is, since the necessity of two-dimensional scanning including the extension direction ED0 is reduced, the scanning is more efficient. As described above, the irradiation of the projection beam PB can be concentrated on a specific area, and the irradiance can be increased. Therefore, an optical detector 10 capable of achieving high detection accuracy can be provided.

[0094] Furthermore, according to the first embodiment, the swinging motion is controlled by the controller 61. Therefore, the projection beam PB can be scanned to achieve high detection accuracy.

[0095] In addition, according to the first embodiment, the projection beam PB is emitted multiple times while passing through at least one of the multiple phase regions obtained by dividing the limited angle range AR in the swinging motion of the scanning mirror 34. The electric pulse is integrated by the multiple emissions of the projection beam PB and the detection of the reflected beam RB corresponding to the multiple emissions. Since the SPAD light receiving element 44 can generate an electronic pulse corresponding to the reception of photons as a digital signal, the detection of the projection beam PB can be processed at high speed. Therefore, the integration of the electric pulse can be performed within the passage time of the phase region in which the measurement direction of the scanning mirror 34 can be considered to be the same or within the time in which the movement of the measurement target object can be ignored. Since such integration is used to calculate TOF, the detection accuracy of the measurement target object can be improved.

[0096] Furthermore, according to the first embodiment, the limited angle ranges AR, ARN, ARW are changeable. With such a change, waste of scanning time can be appropriately suppressed according to the use environment. Therefore, the irradiation of the projection beam PB can be concentrated on a necessary area.

[0097] Furthermore, according to the first embodiment, the speeds HS and LS of the swinging motion are changeable. By making such a change, it is possible to exert appropriate detection accuracy for a specific area.

[0098] Furthermore, according to the first embodiment, as the distance to the measurement target becomes longer in the measurement area MA corresponding to the limited angular range AR, the retention time per unit angle in the swinging motion is set to be longer. The projection beam PB can be irradiated with a high irradiance by utilizing a long retention time at an angle where the distance to the measurement target is long. Therefore, the amount of light irradiated to the measurement target existing at a long distance and the amount of the reflection beam RB reflected from the measurement target to be detected can be increased. Therefore, the detection accuracy of the measurement target can be improved.

[0099] Furthermore, according to the first embodiment, when the optical detector 10 is configured so that the measurement area MA1 corresponding to the angular range AR, ARN is located at the front outer portion of the vehicle WC, within the limited angular range AR, ARN in the swinging motion, the retention time in the central portion ARc is longer than the retention time in the side portion ARs. Then, for example, with respect to the vehicle WC, which tends to be relatively far from the other vehicle TC1, the other vehicle TC1 can be detected with high detection accuracy.

[0100] Furthermore, according to the first embodiment, in the case where the optical detector 10 is configured so that the measurement area MA2 corresponding to the angular range AR, ARW is set laterally outside the vehicle WC, within the limited angular range AR, ARW in the swinging motion, the retention time in the side portion ARs is set longer than the retention time in the center portion ARc. Then, the measurement object on the road side or the measurement object on the adjacent lane can be detected with appropriate detection accuracy according to the assumed distance.

[0101] Furthermore, according to the first embodiment, the scanning mirror 34 has a reflection surface 36 which is a common surface for reflecting the projection beam PB toward the measurement area MA and for reflecting the reflection beam RB from the measurement area MA. By making the reflection surface 36 common, the reflection beam RB which can be elongated in a shape in the extension direction ED0 can be detected without interference.

[0102] In addition, according to the first embodiment, the projection optical system 26 and the receiving optical system 49 are arranged side by side along the extension direction ED0. When the projection beam PB and the reflected beam RB have the same reflection angle due to the swinging motion based on the common rotation axis 33 and the common reflection surface 36, the collection efficiency of the projection beam PB by the projection optical system 26 and the collection efficiency of the reflected beam RB by the receiving optical system 49 are both optimized at the same time. Therefore, the reflected beam RB to be detected based on the irradiance of the projection beam PB can obtain a high gain, and high detection accuracy can be achieved.

[0103] Furthermore, according to the first embodiment, the projection holding member 28 has a concave portion 29 that is recessed toward the projection optical axis POA so as to avoid interference with the projection beam PB reflected by the end AR2 of the ends AR1 and AR2 of the limited angular range AR, where the reflection angle at the scanning mirror 34 is the smallest. Since the mechanical limit of the limited angular range AR can be extended toward the end AR2 according to the volume of the space recessed by the concave portion 29, accurate scanning can be achieved according to the use environment.

[0104] Furthermore, according to the first embodiment, the projection beam PB and the reflection beam RB have an overlap OL in which the footprints PF and RF overlap each other within the housing 11. The size of the housing 11 can be reduced according to the volume of the overlap OL.

[0105] (Other embodiments)

[0106] Although one embodiment has been described, the present disclosure should not be limited to the above embodiment and may be applied to various other embodiments within the scope of the present disclosure.

[0107] Specifically, as a first modification, the number of laser oscillation elements 24 in the light emitting unit 22 may be appropriately changed. That is, the number of small windows 25 in the light emitting window 23 may be appropriately changed, and may be one or more.

[0108] As a second modification, the light emitting unit 22 may be provided at a plurality of positions. For example, a plurality of light emitting units 22 may be provided so that the light emitting windows 23 are arranged in a horizontal direction in a vehicle-mounted state. One projection optical system 26 may be provided for a plurality of light emitting units 22, or the same number of projection optical systems 26 as the number of light emitting units 22 may be provided.

[0109] As a third modification, the focal length of the projection optical system 26 is set so that the light emission window 23 is imaged outside the accommodation chamber 13, and is not limited to the focal length for imaging the light emission window 23 at infinity.

[0110] As a fourth modification, the coverage area PF of the projection beam PB and the coverage area RF of the reflection beam RB may have an overlap OL only in the space inside the accommodation chamber 13 after reflection by the scanning mirror 34. The coverage area PF of the projection beam PB and the coverage area RF of the reflection beam RB may have no overlap OL inside the accommodation chamber 13. In these cases, the reflection surface 36 of the scanning mirror 34 may be provided separately for the beams PB and RB, or the scanning mirror 34 itself may be provided separately for the beams PB and RB.

[0111] As a fifth modification, the measurement calculator 68 does not have to reset the count of the electric pulses regarding one swing motion of the scanning mirror 34, and may continuously count the electric pulses regarding a plurality of swing motions of the scanning mirror 34 to calculate the TOF.

[0112] As a sixth modification, the light receiving element 44 used in the detection unit 42 may be another light receiving element such as an APD light receiving element instead of a SPAD light receiving element.

[0113] As a seventh modification, the projection beam PB may be emitted and scanned corresponding to both the forward path and the backward path of the reciprocating swinging motion within a limited angular range AR. In this case, the detection unit 42 may detect the reflected beam RB on both the forward path and the backward path. In addition, the measurement calculator 68 may integrate and count the electric pulses of the reflected beam RB detected in a predetermined phase region on the forward path and the electric pulses of the reflected beam RB detected in the same phase region on the backward path as the same histogram to calculate TOF.

[0114] As an eighth modification, the measurement calculator 68 may calculate TOF without using a histogram. For example, TOF may be calculated based on the average value of the timing at which the electric pulse is detected.

[0115] As a ninth modification, the optical detector 10 may be configured so that the measurement area MA corresponding to the angular range AR, ARN is located at the rear outer portion of the vehicle WC. In this case, in a swinging motion, the retention time in the central portion ARc of the limited angular range AR, ARN may be longer than the retention time in the side portion ARs.

[0116] As a tenth modification, the controller 61 may be provided outside the housing chamber 13. Furthermore, the controller 61 may be configured as an electronic control device independent of the optical detector 10.

[0117] As an eleventh modification, a measurement calculation circuit may be provided in the detection unit 42. The calculation of the measurement calculator 68 of the controller 61 may be processed by the measurement calculation circuit of the detection unit 42. In this case, the histogram may be temporarily or permanently stored in the RAM 63 or the storage unit 64 of the controller 61. The detection unit 42 may have a RAM or a non-volatile storage medium in addition to the measurement calculation circuit. In this case, the histogram may be temporarily or permanently stored in the RAM 63 or the storage medium of the detection unit 42. In addition, the measurement calculation circuit may be separated from the selection circuit 47 of the decoder 46, or may be installed as an integrated circuit shared with the selection circuit 47.

[0118] The processor and method described in the present disclosure can be implemented by a processing unit of a special-purpose computer, and the processing unit of the special-purpose computer is programmed to perform one or more functions implemented by a computer program. Alternatively, the processor and method described in the present disclosure can be implemented by a dedicated hardware logic circuit. In addition, the processor and method described in the present disclosure can be implemented by a discrete circuit. Alternatively, the processor and method described in the present disclosure can be selected from any one of one or more processing units, one or more hardware logic circuits, and one or more discrete circuits of a computer that executes a computer program. It can be implemented by combination. A computer program can be stored in a tangible non-transient computer-readable medium as an instruction to be executed by a computer.

Claims

1. An optical detector configured to project a projection beam (PB) towards a measurement area (MA, MA1, MA2) and to detect a return beam (RB) from the measurement area, the optical detector comprising: A light emitter (22) having a light emission window (23) extending in an extension direction (ED0) to emit the projection beam from the light emission window; a scanning mirror (34) for scanning by reflecting the projection beam, wherein the scanning mirror is configured to move within a limited angular range (AR, ARN, ARW) around a rotation axis (33), the rotation axis being along a direction (ED1) corresponding to the extension direction; a projection optical system (26) configured to collect the projection beam emitted from the light emitter and project the collected beam toward the scanning mirror; and a receiving optical system (49) configured to detectably converge the return beam reflected by the scanning mirror, wherein The scanning mirror has a reflecting surface (36) which is common for reflecting the projection beam towards the measurement area and for reflecting the return beam from the measurement area, The projection beam and the return beam have an overlap (OL) in which a footprint (PF) of the projection beam and a footprint (RF) of the return beam partially overlap each other on the reflective surface, and The projection optical system and the receiving optical system are arranged side by side along the extension direction, The optical detector further comprises a projection holding member (28), wherein the projection holding member (28) holds the projection optical system, wherein: The projection holding member has a concave portion (29) recessed toward the optical axis (POA) of the projection optical system to avoid interference with the projection beam reflected at the end (AR2) of the angular range, where the reflection angle at the scanning mirror is minimum.

2. The optical detector of claim 1, further comprising at least one processor to control the swinging motion of the scanning mirror.

3. The optical detector according to claim 2, further comprising a single-photon avalanche photodiode light receiving element (44) which generates an electrical pulse as a digital signal in response to reception of a photon by the return beam, wherein The angular range is divided into a plurality of phase regions in the oscillating motion of the scanning mirror, The at least one processor causes the projection beam to be emitted a plurality of times while passing through at least one phase region of the plurality of phase regions, and The at least one processor integrates the electrical pulses generated by detecting the projection beam and the return beam corresponding to the emission of the projection beam to calculate a time of flight of light from the emission to the detection.

4. The optical detector according to claim 2, wherein: The at least one processor is capable of varying the angular range.

5. The optical detector according to claim 2, wherein: The at least one processor is capable of varying the speed (HS, LS) of the oscillating movement.

6. The optical detector according to claim 2, wherein: The at least one processor lengthens the retention time per unit angle in the swinging motion as the angular range corresponds to a farther region where the distance to the measurement target in the measurement region is farther.

7. An optical detector according to any one of claims 2 to 6, for use in a vehicle (WC), wherein: The measurement area corresponding to the angular range is located at the front exterior or the rear exterior of the vehicle, and The at least one processor sets a retention time per unit angle in the swinging motion to be longer in a central portion (ARc) of the angular range than in a side portion (ARs) of the angular range.

8. An optical detector according to any one of claims 2 to 6, for use in a vehicle (WC), wherein: The measurement area corresponding to the angular range is located laterally outside the vehicle, and The at least one processor sets a retention time per unit angle in the swinging motion to be longer in a side portion of the angular range than in a central portion of the angular range.

9. The optical detector according to any one of claims 1 to 6, further comprising a housing (11) having an optical window (14) for reciprocating the projection beam and the return beam between the interior of the housing and the measurement region, the housing forming an outer portion of the optical detector, wherein In the overlap (OL), the footprint of the projection beam (PF) and the footprint of the return beam (RF) overlap each other inside the housing.

Images