Laser radar device

Abstract

To suppress erroneous detection of a surface existing below a monitoring area as an object in a laser radar device.SOLUTION: A light projection section (20) and a light reception section (30) are disposed side by side toward a rotating mirror (50), a light projection axis (AX) of laser beams projected by the light projection section is non-coaxial with a rotation axis (CL), the rotating mirror reflects laser beams from the light projection section toward a transmission cover (60) and reflects reflection light from the transmission cover toward the light reception section, an inner surface (62) and an outer surface (63) of the transmission cover have a positive inclination relative to an incidence axis that is a center axis of luminous fluxes of laser beams impinging on the transmission cover from the rotating mirror in each section that includes the rotation axis and passes an area that laser beams in the transmission cover are transmitted, and the inclination of the outer surface of the transmission cover relative to the incidence axis is smaller than the inclination of the inner surface of the transmission cover relative to the incidence axis in an optical path in which luminous fluxes of laser beams are transmitted through the transmission cover.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a lidar device.

Background Art

[0002] For example, there is a lidar in which a light projector and a light receiver are arranged side by side so as to have a biaxial structure and parallel optical axes (see Patent Document 1). In the lidar device described in Patent Document 1, the laser light projected from the light projector is reflected by a continuously rotating rotary mirror in the direction of the monitoring area, passes through the front panel, and travels horizontally to the monitoring area.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the lidar device described in Patent Document 1, since the optical axis of the light projector (light projecting unit) is non-coaxial with the rotation axis of the rotary mirror, the position where the laser light from the light projector is reflected by the rotary mirror changes depending on the rotation position of the rotary mirror. For this reason, the height of the laser light reflected by the rotary mirror and traveling horizontally to the monitoring area changes depending on the rotation position of the rotary mirror.

[0005] In the above configuration, when the light beam of the laser light traveling to the monitoring area is gradually thickened, the present inventors have noticed that the following problems occur. That is, when the lidar device is installed at a position close to the ground, for example, and the monitoring area is horizontally scanned with laser light, the lower part of the light beam of the laser light traveling to the monitoring area at the lowest height may hit the ground in the distance. In this case, there is a risk that the light receiver (light receiving unit) may receive the laser light reflected by the ground (the surface existing below the monitoring area) and erroneously detect the ground as an object.

[0006] In addition, the front panel (transmission cover) of a conventional lidar device is designed such that, even if the laser light transmitted through the front panel is refracted, the central axis of the light beam of the laser light incident on the front panel and the central axis of the light beam of the laser light emitted from the front panel are parallel regardless of the shape of the front panel.

[0007] The present invention has been made to solve such problems, and its main object is to arrange a light projecting unit and a light receiving unit side by side facing a rotating mirror, make the light projecting axis non-coaxial with the rotation axis of the rotating mirror, and suppress false detection of a surface existing below a monitoring area as an object in a lidar device in which the light beam of the laser light traveling to the monitoring area gradually becomes thicker.

Means for Solving the Problems

[0008] The first means for solving the above problems is a light projecting unit that projects laser light, a light receiving unit that receives the reflected light, which is the laser light reflected by an object, a rotating mirror that rotates about a predetermined rotation axis, a transmission cover that has a refractive index greater than the refractive index of air and transmits the laser light traveling from the rotating mirror to the outside and the reflected light traveling from the outside to the rotating mirror, A lidar device comprising: and the light beam of the laser light that passes through the transmission cover and travels to the monitoring area gradually becomes thicker, the light projecting unit and the light receiving unit are arranged side by side facing the rotating mirror, the light projecting axis of the laser light projected by the light projecting unit is non-coaxial with the rotation axis, the rotating mirror reflects the laser light from the light projecting unit toward the transmission cover and reflects the reflected light from the transmission cover toward the light receiving unit, In each cross-section that includes the rotation axis and passes through the range where the laser light in the transmissive cover is transmitted, the inner surface and the outer surface of the transmissive cover have a positive inclination with respect to the incident axis, which is the central axis of the light beam of the laser light incident from the rotary mirror to the transmissive cover, and in the optical path where the light beam of the laser light passes through the transmissive cover, the inclination of the outer surface of the transmissive cover with respect to the incident axis is smaller than the inclination of the inner surface of the transmissive cover with respect to the incident axis. A lidar device.

[0009] According to the above configuration, the light projecting unit projects laser light, and the light receiving unit receives the reflected light, which is the laser light reflected by the object. The rotary mirror rotates about a predetermined rotation axis. The transmissive cover has a refractive index greater than the refractive index of air and transmits the laser light directed from the rotary mirror to the outside and the reflected light directed from the outside to the rotary mirror.

[0010] Here, the light projection axis of the laser light projected by the light projecting unit is non-coaxial with the rotation axis, and the rotary mirror reflects the laser light from the light projecting unit toward the transmissive cover. For this reason, the position where the laser light from the light projecting unit irradiates the rotary mirror changes depending on the rotational position of the rotary mirror. Consequently, the position in the direction of the light projection axis of the laser light reflected by the rotary mirror and directed toward the transmissive cover changes depending on the rotational position of the rotary mirror. Also, the light beam of the laser light that passes through the transmissive cover and travels to the monitoring area is made to gradually become thicker. Therefore, for example, when the lidar device scans the monitoring area with laser light at a position close to the ground, in a conventional lidar device in which the central axis of the light beam of the laser light incident on the transmissive cover and the central axis of the light beam of the laser light emitted from the transmissive cover are parallel, there is a possibility that the lower part of the light beam of the laser light traveling to the monitoring area at the lowest height hits the ground at a distance. In this case, there is a possibility that the light receiving unit receives the laser light reflected by the ground and erroneously detects the ground as an object.

[0011] In this regard, according to the above configuration, in each cross-section including the rotation axis and passing through the range where the laser light passes through the transmissive cover, the inner surface and the outer surface of the transmissive cover have a positive inclination with respect to the incident axis, which is the central axis of the light beam of the laser light incident from the rotary mirror to the transmissive cover. In the optical path where the light beam of the laser light passes through the transmissive cover, the inclination of the outer surface of the transmissive cover with respect to the incident axis is smaller than the inclination of the inner surface of the transmissive cover with respect to the incident axis. For this reason, for example, when the incident axis is horizontal, the central axis of the light beam of the laser light emitted from the transmissive cover (hereinafter referred to as the "emission axis") can be inclined upward from the horizontal. Therefore, it is possible to suppress the lower part of the light beam of the laser light advancing to the monitoring area at the lowest height from hitting the ground at a distance, and it is possible to suppress misdetection of the ground (the surface existing below the monitoring area) as an object. In a conventional lidar device in which the incident axis and the emission axis are parallel, in the optical path where the light beam of the laser light passes through the transmissive cover, the inclination of the inner surface of the transmissive cover with respect to the incident axis and the inclination of the outer surface of the transmissive cover with respect to the incident axis are the same.

[0012] In the second means, in each cross-section, the difference between the inclination of the inner surface of the transmissive cover with respect to the incident axis and the inclination of the outer surface of the transmissive cover with respect to the incident axis in the optical path is larger in a portion where the distance from the light projecting portion in the direction of the light projection axis in the transmissive cover is shorter. According to such a configuration, for example, when the incident axis is horizontal, the laser light incident on a portion where the distance from the light projecting portion in the direction of the light projection axis in the transmissive cover is shorter can incline the emission axis more upward. Therefore, while suppressing excessive upward inclination of the emission axis of the laser light with a low possibility of hitting the ground, the emission axis can be inclined upward more for the laser light with a high possibility of hitting the ground.

[0013] The third means is a light projecting portion that projects laser light, a light receiving portion that receives the reflected light, which is the laser light reflected by an object, a rotary mirror that rotates about a predetermined rotation axis A transmission cover having a refractive index greater than the refractive index of air, and transmitting the laser light traveling from the rotary mirror to the outside and the reflected light traveling from the outside to the rotary mirror; A lidar device including the above, in which the light beam of the laser light passing through the transmission cover and advancing to the monitoring area gradually becomes thicker, The light projecting unit and the light receiving unit are arranged side by side toward the rotary mirror, The optical axis of the laser light projected by the light projecting unit is non-coaxial with the rotation axis, The rotary mirror reflects the laser light from the light projecting unit toward the transmission cover and reflects the reflected light from the transmission cover toward the light receiving unit, In each cross section including the rotation axis and passing through the range where the laser light passes through the transmission cover, the center axis of the light beam of the laser light incident from the rotary mirror to the transmission cover (incident axis), the center axis of the light beam of the laser light emitted from the transmission cover has a positive inclination. Thus, the inclination of the inner surface of the transmission cover and the inclination of the outer surface of the transmission cover are set.

[0014] According to the above configuration, for example, when the incident axis is horizontal, the central axis (emission axis) of the light beam of the laser light emitted from the transmission cover can be inclined upward from the horizontal. Therefore, it is possible to suppress the lower part of the light beam of the laser light advancing to the monitoring area at the lowest height from hitting the ground in the distance, and it is possible to suppress erroneously detecting the ground (the surface existing below the monitoring area) as an object.

[0015] In the fourth means, in each of the cross sections, the positive inclination of the central axis of the light beam of the laser light emitted from the transmission cover with respect to the incident axis is set such that it becomes larger for the laser light incident on the transmission cover at a position closer to the light projecting unit in the direction of the light projection axis. With such a configuration, for example, when the incident axis is horizontal, the laser light incident on the transmission cover at a position closer to the light projecting unit in the direction of the light projection axis can tilt the emission axis upward more. Therefore, while suppressing excessive upward tilting of the emission axis of the laser light with a low possibility of hitting the ground, the emission axis of the laser light with a high possibility of hitting the ground can be tilted upward more.

[0016] In the fifth means, in each of the cross sections, the inclination of the inner surface of the transmission cover with respect to the incident axis becomes smaller for the inner surface closer to the light projecting unit in the direction of the light projection axis, and the outer surface of the transmission cover has a shape obtained by parallelly moving the inner surface of the transmission cover in the direction of the incident axis.

[0017] According to the above configuration, in each of the cross-sections, the outer surface of the transmissive cover has a shape obtained by translating the inner surface of the transmissive cover in the direction of the incident axis. Therefore, at positions where the distances from the light projecting portion in the direction of the light projecting axis are the same on the inner and outer surfaces of the transmissive cover, the inclination of the inner surface of the transmissive cover and the inclination of the outer surface are the same. Here, the transmissive cover has a refractive index greater than that of air, and in each of the cross-sections, the inner and outer surfaces of the transmissive cover have a positive inclination with respect to the incident axis. For this reason, when the laser light is incident from air into the transmissive cover, the refractive angle becomes smaller than the incident angle of the laser light, and the laser light is refracted in a direction approaching the light projecting portion in the direction of the light projecting axis. And in each of the cross-sections, the inclination of the inner surface (i.e., the outer surface) of the transmissive cover with respect to the incident axis becomes smaller as the inner surface closer to the light projecting portion in the direction of the light projecting axis. Therefore, in the optical path where the light beam of the laser light passes through the transmissive cover, the inclination of the outer surface of the transmissive cover with respect to the incident axis can be made smaller than the inclination of the inner surface of the transmissive cover with respect to the incident axis. In a conventional lidar device in which the incident axis and the emission axis are parallel, the outer surface of the transmissive cover has, for example, a shape obtained by translating the inner surface of the transmissive cover in the thickness direction of the transmissive cover (a direction perpendicular to the inner surface).

[0018] Specifically, as in the sixth means, in each of the cross-sections, the inner surface of the transmissive cover is formed as a straight line having a first inclination with a constant inclination with respect to the incident axis, and the outer surface of the transmissive cover is formed as a straight line having a second inclination with an inclination smaller than the first inclination and constant with respect to the incident axis. Such a configuration can be adopted. According to such a configuration, while simplifying the shape of the transmissive cover, for example, when the incident axis is horizontal, the emission axis can be inclined upward from the horizontal.

Brief Description of the Drawings

[0019]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0020] Hereinafter, an embodiment embodied in a laser radar device for detecting an object that has entered a monitoring area, for example, will be described with reference to the drawings.

[0021] As shown in FIG. 1, the lidar device 10 includes a housing 11, a light projecting unit 20, a light receiving unit 30, a rotary reflection mechanism 40, a transmission cover 60, a lid 12, and the like. In FIG. 1, the direction of the optical axis AX and the direction of the central axis CL are taken as the vertical direction, and the case of performing a substantially horizontal scan by laser light (details will be described later) will be described as an example. The lidar device 10 is installed, for example, on the ground or on a low stand installed on the ground. That is, the lidar device 10 scans a position close to the ground (a position at a predetermined height) substantially horizontally with laser light.

[0022] The housing 11 is formed in a hollow rectangular parallelepiped shape (box shape) with an open upper side (upper surface). Inside the housing 11, the light projecting unit 20, the light receiving unit 30, and a partition member 29 are housed. The light projecting unit 20 and the light receiving unit 30 are arranged side by side in the horizontal direction.

[0023] The light projecting unit 20 includes a laser diode 21 and a light projecting lens 22. The laser diode 21 (light emitting element) receives a pulsed current from a drive circuit (not shown) under the control of a control circuit (not shown), and intermittently emits pulsed laser light upward according to this pulsed current. The laser light is, for example, infrared laser, visible laser, ultraviolet laser, or the like. On the optical axis AX of the laser light emitted from the laser diode 21, a light projecting lens 22 is provided. The light projecting lens 22 is configured as a collimating lens, and converts the laser light from the laser diode 21 into substantially parallel light. For example, the light beam of the laser light transmitted through the light projecting lens 22 gradually becomes thicker (the cross-sectional area of the light beam gradually becomes larger). The optical axis AX (light projecting axis) extends in the vertical direction (up and down direction). That is, the light projecting unit 20 faces upward and faces the rotary mirror 50 of the rotary reflection mechanism 40. The light projecting unit 20 projects laser light upward, that is, toward the rotary mirror 50. Note that the light beam of the laser light transmitted through the light projecting lens 22 may gradually become thinner (the cross-sectional area of the light beam may gradually become smaller). Even in that case, if the light beam of the laser light exceeds the focal point where the light beam converges, the light beam of the laser light gradually becomes thicker. The position of the focal point may be between the light projecting lens 22 and the rotary mirror 50, between the rotary mirror 50 and the transmission cover 60, or slightly ahead of the transmission cover 60. In short, it is sufficient that the light beam of the laser light transmitted through the transmission cover 60 and advancing into the monitoring area gradually becomes thicker.

[0024] A cylindrical transmission cover 60 is attached to the upper part of the housing 11. The transmission cover 60 is formed of resin, glass, or the like that transmits laser light. The refractive index of the resin or glass is larger than the refractive index of air, and the transmission cover 60 has a refractive index larger than the refractive index of air. Inside the transmission cover 60, a rotary reflection mechanism 40 is housed. The upper opening of the transmission cover 60 is closed by a lid 12.

[0025] The rotary reflection mechanism 40 includes a support base 41, a motor 42, a shaft portion 43, a rotary mirror 50, etc. The support base 41 (support member) is formed in a columnar or cylindrical shape centered on the central axis CL and is fixed to, for example, the housing 11. The motor 42 (drive unit) rotationally drives the rotary mirror 50 connected to the shaft portion 43 by rotating the shaft portion 43. The shaft portion 43 and the rotary mirror 50 rotate about the central axis CL (predetermined rotation axis). As a specific configuration of the motor 42, for example, a servo motor or the like may be used, or a motor that rotates steadily may be used, and a pulsed laser beam may be output in synchronization with the timing when the rotary mirror 50 faces the detection direction of the object. The motor 42 and the rotary mirror 50 are supported by the support base 41. Note that the support base 41 can also be fixed to the upper part of the lid 12 or the transmissive cover 60.

[0026] The rotary mirror 50 is arranged so as to intersect the optical axis AX, and deflects (reflects) the laser beam from the laser diode 21 (light projecting unit 20) toward the space outside the transmissive cover 60. Further, the rotary mirror 50 deflects (reflects) the reflected light from an object existing in the space outside the transmissive cover 60 toward the photodiode 31 (light receiving unit 30). That is, the rotary mirror 50 reflects the laser beam from the light projecting unit 20 toward the transmissive cover 60 and reflects the reflected light from the transmissive cover 60 toward the light receiving unit 30. The rotary mirror 50 is formed of, for example, a plane mirror. The rotary mirror 50 is inclined at an angle of, for example, 45° with respect to the vertical direction (optical axis AX), and is configured such that the laser beam reflected by the rotary mirror 50 is irradiated in the horizontal direction.

[0027] The transmissive cover 60 transmits the laser beam traveling from the rotary mirror 50 to the outside and the reflected light traveling from the object (outside) to the rotary mirror 50. The detailed shape of the transmissive cover 60 will be described later.

[0028] The light receiving unit 30 includes a photodiode 31 and a light receiving lens 32. The light receiving unit 30 faces upward and faces the rotary mirror 50 of the rotary reflection mechanism 40. That is, the light projecting unit 20 and the light receiving unit 30 face the same direction. The light receiving lens 32 condenses the laser light reflected downward by the rotary mirror 50 and guides it to the photodiode 31. The optical axis (light receiving axis) of the reflected light from the rotary mirror 50 toward the photodiode 31 (light receiving unit 30) coincides with the central axis CL (is coaxial). On the other hand, the central axis CL (light receiving axis) and the optical axis AX (light projecting axis) are parallel and offset (non-coaxial). The photodiode 31 (light receiving element) is composed of, for example, an avalanche photodiode. The photodiode 31 receives the reflected light of the laser light projected from the light projecting unit 20 reflected by an object and converts it into an electrical signal.

[0029] In a configuration where the light projecting unit 20 and the light receiving unit 30 are arranged side by side facing the rotary mirror 50, there is a risk that the laser light projected by the light projecting unit 20 may leak to the light receiving unit 30. Therefore, the lidar device 10 includes a light-shielding partition member 29 that partitions the light projecting unit 20 and the light receiving unit 30. The partition member 29 is formed in a plate shape and is disposed between the light projecting unit 20 and the light receiving unit 30.

[0030] In the direction of the optical axis AX and the central axis CL (the direction in which the laser light is projected from the light projecting unit 20), if the length of the light-shielding partition member 29 that partitions the light projecting unit 20 and the light receiving unit 30 is too short, the effect of blocking the laser light leaking from the light projecting unit 20 toward the light receiving unit 30 by the partition member 29 is reduced. On the other hand, in the direction of the optical axis AX and the central axis CL, if the length of the partition member 29 protruding toward the rotary mirror 50 side is too long, there is a risk that the reflected light reflected by the rotary mirror 50 and heading toward the light receiving unit 30 may be blocked by the partition member 29. Therefore, the partition member 29 protrudes 0 to 2 [mm] (for example, 1 [mm]) more than the end 22a on the rotary mirror 50 side of the light projecting lens 22 (light projecting unit 20) in the direction of the optical axis AX and the central axis CL.

[0031] The distance calculation unit (not shown) calculates the distance from the light projecting unit 20 (laser radar device 10) to the object for each light projection direction based on the elapsed time from when the laser light is projected by the light projecting unit 20 until the reflected light is received by the light receiving unit 30. Specifically, the distance calculation unit calculates the distance from the laser radar device 10 to the object in proportion to the elapsed time from when the laser light is projected until the reflected light is received, based on the principle of TOF (Time Of Flight).

[0032] The laser light projected from the light projecting unit 20 is reflected by the rotary mirror 50 and irradiated to the outside (monitoring area) of the laser radar device 10 through the transmissive cover 60. When there is any object on the optical path of the laser light irradiated to the monitoring area, the laser light is reflected by the object. The reflected light reflected by the object enters the laser radar device 10 through the transmissive cover 60, is reflected by the rotary mirror 50, and is received by the light receiving unit 30.

[0033] FIG. 2 is a schematic diagram showing a laser radar device 10A of a comparative example. This comparative example was conceived by the inventor of the present application for comparison with the present embodiment and is not a known technique. Note that the same reference numerals are given to the same parts as those in the present embodiment, and the description thereof is incorporated by reference.

[0034] In the comparative example shown in the figure, the central axis CL and the optical axis AX are coaxial (coincide). In each cross section including the optical axis AX, the shapes of the inner surface and the outer surface of the transmissive cover 60A are straight lines inclined such that the distance from the optical axis AX becomes longer toward the upper part. The inclination of the inner surface of the transmissive cover 60A and the inclination of the outer surface of the transmissive cover 60A are the same. The shape of the transmissive cover 60A is symmetric with respect to the optical axis AX in each cross section including the optical axis AX and is uniform in the circumferential direction centered on the optical axis AX. In the above configuration, the position where the laser light from the light projecting unit 20 irradiates the rotary mirror 50 does not change depending on the rotational position of the rotary mirror 50.

[0035] For example, when the rotary mirror 50 is at the rotational position represented by the solid line, the laser light from the light projecting unit 20 is irradiated onto the center of the rotary mirror 50 in the height direction (the direction of the optical axis AX). The laser light reflected by the rotary mirror 50 passes through the transmissive cover 60A at the center height of the rotary mirror 50 and is projected horizontally to the outside.

[0036] Also, when the rotary mirror 50 rotates 180° from the rotational position indicated by the solid line to the rotational position represented by the two-dot chain line, the laser light from the light projecting unit 20 is irradiated onto the center of the rotary mirror 50 in the height direction. The laser light irradiated onto the rotary mirror 50 travels horizontally to the left in the figure, but since the shape of the transmissive cover 60A is symmetric with respect to the optical axis AX, it is represented for convenience as if the laser light travels horizontally to the right.

[0037] As described above, the position of the laser light reflected by the rotary mirror 50 and traveling toward the transmissive cover 60A in the height direction is constant regardless of the rotational position of the rotary mirror 50.

[0038] FIG. 3 is a schematic diagram showing a laser radar device 10B of a comparative example. This comparative example was conceived by the inventor of the present application for comparison with the present embodiment and is not a known technique. Note that the same reference numerals are given to the same parts as those in the present embodiment, and the description thereof is incorporated by reference.

[0039] In the comparative example shown in the figure, the central axis CL and the optical axis AX are non-coaxial. The shape of the transmissive cover 60B is the same as the shape of the above-described transmissive cover 60A. That is, the central axis CL and the optical axis AX are parallel and offset. In each cross section including the optical axis AX, the shapes of the inner surface and the outer surface of the transmissive cover 60B are straight lines inclined such that the distance from the optical axis AX increases toward the upper part. The inclination of the inner surface of the transmissive cover 60B is the same as the inclination of the outer surface of the transmissive cover 60B. The shape of the transmissive cover 60B is symmetric with respect to the optical axis AX in each cross section including the optical axis AX and is uniform in the circumferential direction centered on the optical axis AX. In the above configuration, the position where the laser light from the light projecting unit 20 is irradiated onto the rotary mirror 50 changes depending on the rotational position of the rotary mirror 50.

[0040] For example, when the rotary mirror 50 is at the rotational position represented by the two-dot chain line, the laser light from the light projecting unit 20 is irradiated below the center of the rotary mirror 50 in the height direction (the direction of the optical axis AX). The laser light reflected by the rotary mirror 50 (displayed as the laser light traveling rightward for convenience) passes through the transmissive cover 60B at a position lower than the center of the rotary mirror 50 and is horizontally projected outside.

[0041] Also, when the rotary mirror 50 rotates 180° from the rotational position indicated by the two-dot chain line to the rotational position represented by the solid line, the laser light from the light projecting unit 20 is irradiated above the center of the rotary mirror 50 in the height direction. The laser light reflected by the rotary mirror 50 passes through the transmissive cover 60B at a position higher than the center of the rotary mirror 50 and is horizontally projected outside.

[0042] As described above, the position in the height direction of the laser light reflected by the rotary mirror 50 and heading toward the transmissive cover 60B changes according to the rotational position of the rotary mirror 50. Therefore, as shown in the elliptical region R1 of FIG. 4, there is a possibility that the lower part of the light beam LF3 of the laser light traveling to the monitoring region A at the lowest height hits the ground G (the surface existing below the monitoring region A) in the distance. For example, there is a possibility that the lower part of the light beam LF3 of the laser light hits the ground G near the maximum distance (for example, 10 [m]) at which the lidar device 10B can measure the distance to an object. In this case, there is a possibility that the light receiving unit 30 receives the laser light reflected by the ground G and erroneously detects the ground G as an object. On the other hand, the light beam LF2 of the laser light traveling to the monitoring region A at the central height and the light beam LF1 of the laser light traveling to the monitoring region A at the highest height do not hit the ground G even near the maximum distance. Note that, for example, even if the lower part of the light beam LF2 of the laser light traveling to the monitoring region A at the central height hits the ground G beyond the maximum distance, the possibility of erroneously detecting the ground G as an object is low.

[0043] Figs. 5 to 7 are schematic diagrams showing the propagation directions of laser beam L when laser beam L is incident on substance M from air. First, the common matters among Figs. 5 to 7 will be described. The refractive index of substance M is larger than that of air. Laser beam L is indicated by the central axis of the light beam of laser beam L. Laser beam L is projected horizontally and is incident on substance M. The incident angle θ1 and the refractive angle θ2 are from air to substance M, and the incident angle θ3 and the refractive angle θ4 (exit angle θ4) are from substance M to air.

[0044] In Fig. 5, the incident angle θ1 = 0 [°], and the inclination of the inner surface Mi of substance M with respect to the horizontal is the same as the inclination of the outer surface Mo with respect to the horizontal. For this reason, the refractive angle θ2 = 0 [°], the incident angle θ3 = 0 [°], and the refractive angle θ4 = 0 [°].

[0045] In Fig. 6, the incident angle θ1 ≠ 0 [°], and the inclination of the inner surface Mi of substance M with respect to the horizontal is the same as the inclination of the outer surface Mo of substance M with respect to the horizontal. The angle of the inner surface Mi of substance M with respect to the horizontal and the angle of the outer surface Mo of substance M with respect to the horizontal are both the angle γ. For this reason, θ1 > θ2, θ2 = θ3, θ3 < θ4, and θ1 = θ4. The incident axis, which is the central axis of the light beam of laser beam L incident from air to substance M, and the exit axis, which is the central axis of the light beam of laser beam L exiting from substance M to air, are parallel, and the incident axis and the exit axis of laser beam L are horizontal.

[0046] In FIG. 7, the incident angle θ1≠0 [°], and the inclination of the inner surface Mi of the substance M with respect to the horizontal is greater than the inclination of the outer surface Mo of the substance M with respect to the horizontal. The angle of the inner surface Mi of the substance M with respect to the horizontal is the angle γ, and the angle of the outer surface Mo of the substance M with respect to the horizontal is the angle γ-β. Therefore, θ1>θ2, θ3=θ2+β, θ4=θ1+α, and α>β. The incident axis, which is the central axis of the laser beam L incident from the air into the substance M, is horizontal, and the emission axis, which is the central axis of the laser beam L emitted from the substance M into the air, is inclined upward from the horizontal. That is, the emission axis of the laser beam L has a positive inclination with respect to the incident axis of the laser beam L. Therefore, in the present embodiment, in the optical path (on the path of the laser beam L indicated by the arrow) through which the laser beam L passes through the transmission cover 60, the inclination of the inner surface and the inclination of the outer surface of the transmission cover 60 are set so as to satisfy the relationship in FIG. 7.

[0047] FIG. 8 is a cross-sectional view showing the shape of the inner surface 62 of the transmission cover 60. In each cross-section including the central axis CL and passing through the range 61 through which the laser beam L passes in the transmission cover 60, the shape of the inner surface 62 of the transmission cover 60 is formed as a parabola (parabolic shape). In each of the above cross-sections, the inner surface 62 and the outer surface 63 of the transmission cover 60 have a positive inclination with respect to the incident axis of the laser beam L. The outer peripheral surface 41c of the support base 41 constitutes a reflection suppression portion that suppresses the reflection of the irradiated laser beam L, such as a low reflection surface such as black or a diffusion reflection surface formed with fine irregularities. That is, the reflection suppression portion is a part of the support base 41 (support member) and is integrated with the support base 41. The reflection suppression portion is disposed on the side opposite to the light projecting portion 20 and the light receiving portion 30 with respect to the rotary mirror 50. In the horizontal direction (the direction in which the laser beam L travels from the rotary mirror 50 to the transmission cover 60), the distance y2 from the central axis CL to the outer peripheral surface 41c of the support base 41 is longer than the distance y3 from the central axis CL to the end of the light receiving portion 30 and the distance y4 from the central axis CL to the end of the rotary mirror 50. That is, the outer peripheral surface 41c (reflection suppression portion) is disposed at a position closer to the transmission cover 60 (specifically, the portion 62a closest to the central axis CL in the transmission cover 60) than the light receiving portion 30 and the rotary mirror 50 in the horizontal direction.

[0048] The shape of the inner surface 62 of the transmissive cover 60 will be described in detail. Taking the cross section shown in FIG. 8 as the xy plane, the vertical direction (perpendicular direction) is the x-axis direction, and the horizontal direction is the y-axis direction. The origin O is set within the range from the lower end 41a (first end) to the upper end 41b (second end) of the support base 41 in the vertical direction. The parabola is represented by the equation y = (x^2) / 4a. x^2 represents the square of x. The focus is F(0,a), and the equation of the directrix is y = -a. a is set to be smaller than the distance y1 from the origin O to the support base 41. That is, the focus F is set at a position closer to the transmissive cover 60 than the outer peripheral surface 41c of the support base 41 in the horizontal direction (the direction in which the laser beam L travels from the rotary mirror 50 to the transmissive cover 60). As described above, the shape of the inner surface 62 of the transmissive cover 60 is formed as a parabola that reflects a part of the laser beam traveling from the rotary mirror 50 to the inner surface 62 and reflected by the inner surface 62 toward the focus F set at a position farther from the rotary mirror 50 than the light receiving portion 30 in the direction of the optical axis AX. That is, the inner surface 62 of the transmissive cover 60 reflects the laser beam L to the side opposite to the light projecting portion 20 and the light receiving portion 30 in the direction of the optical axis AX (light projecting axis). And the outer peripheral surface 41c of the support base 41 is provided at the position irradiated with the laser beam reflected by the inner surface 62.

[0049] In the figure, the relative relationship in which the position of the laser beam L reflected by the rotary mirror 50 and traveling toward the transmissive cover 60 changes depending on the rotational position of the rotary mirror 50 is represented as follows for convenience. That is, the rotational position of the rotary mirror 50 is fixed, and instead, the position of the laser beam irradiated from the light projecting unit 20 to the rotary mirror 50 is changed. As a result, as indicated by the arrows, the laser beams reflected at each position of the rotary mirror 50 are all conveniently shown as laser beams L traveling in the right direction. Also, the laser beam L is represented by the central axis of the light flux of the laser beam L. Each laser beam L reflected at each position of the rotary mirror 50 and traveling horizontally toward the transmissive cover 60 is reflected by the inner surface 62 of the transmissive cover 60 toward the focus F. Each laser beam concentrated at the focus F passes through the focus F and slightly spreads to irradiate the outer peripheral surface 41c of the support base 41. Then, the laser beam irradiated on the outer peripheral surface 41c is suppressed from being reflected by the outer peripheral surface 41c as a reflection suppression unit.

[0050] In the direction of the optical axis AX, the inclination of the inner surface 62 with respect to the incident axis (horizontal), which is the central axis of the light flux of the laser beam L at a point P2 located lower than the point P1, is smaller than the inclination of the inner surface 62 with respect to the incident axis (horizontal) of the laser beam L at the point P1. The angle γ2 of the inner surface 62 with respect to the incident axis of the laser beam L at the point P2 is smaller than the angle γ1 of the inner surface 62 with respect to the incident axis of the laser beam L at the point P1. That is, in each cross section passing through the range 61 through which the laser beam L passes in the transmissive cover 60 and including the central axis CL, the inclination of the inner surface 62 of the transmissive cover 60 with respect to the incident axis of the laser beam L becomes smaller as the inner surface 62 closer to the light projecting unit 20 is in the direction of the optical axis AX. The outer surface 63 of the transmissive cover 60 has a shape obtained by translating the inner surface 62 of the transmissive cover 60 in the direction of the incident axis of the laser beam (horizontal). In a conventional lidar device in which the incident axis of the laser beam and the emission axis, which is the central axis of the light flux of the laser beam emitted from the transmissive cover, are parallel, the outer surface of the transmissive cover has a shape obtained by translating the inner surface of the transmissive cover in the thickness direction of the transmissive cover (a direction perpendicular to the inner surface), for example.

[0051] FIG. 9 is an enlarged cross-sectional view showing an enlarged view of the region R2 of the transmissive cover 60 in FIG. 8. The laser beam L is indicated by the central axis of the light beam of the laser beam L.

[0052] As described above, the outer surface 63 of the transmissive cover 60 has a shape obtained by translating the inner surface 62 of the transmissive cover 60 in the direction of the incident axis of the laser beam L (horizontal). Therefore, at the points P21 and P31 having the same height, the inclination of the inner surface 62 with respect to the horizontal at the point P21 is the same as the inclination of the outer surface 63 with respect to the horizontal at the point P31. In the cross-section shown in FIG. 9, the inclination of the inner surface 62 of the transmissive cover 60 with respect to the incident axis (horizontal) of the laser beam L becomes smaller as the position is lower (the inner surface 62 closer to the light projecting unit 20 in the direction of the optical axis AX). Similarly, in the cross-section shown in FIG. 9, the inclination of the outer surface 63 of the transmissive cover 60 with respect to the incident axis (horizontal) of the laser beam L becomes smaller as the position is lower.

[0053] For example, the inclination of the outer surface 63 with respect to the horizontal at point P33 is smaller than the inclination of the outer surface 63 with respect to the horizontal at point P31, that is, the inclination of the inner surface 62 with respect to the horizontal at point P21. Similarly, the inclination of the outer surface 63 with respect to the horizontal at point P32 is smaller than the inclination of the inner surface 62 with respect to the horizontal at point P22. Points P22 and P32 are points on the optical path (the advancing path of the laser beam L) of the laser beam L passing through the transmissive cover 60. Therefore, in the optical path (the advancing path of the laser beam L) where the laser beam L passes through the transmissive cover 60, the inclination of the inner surface 62 and the inclination of the outer surface 63 satisfy the relationship shown in FIG. 7. That is, θ1>θ2, θ3>θ2, θ4>θ1. And θ4 - θ1>θ3 - θ2. For this reason, the incident axis, which is the central axis of the light beam of the laser beam L incident from the air (in the air) to the transmissive cover 60, is horizontal, and the emission axis, which is the central axis of the light beam of the laser beam L emitted from the transmissive cover 60 to the air, is inclined upward from the horizontal. That is, the emission axis of the laser beam L has a positive inclination with respect to the incident axis of the laser beam L. In a conventional lidar device where the incident axis and the emission axis of the laser beam are parallel, in the optical path where the light beam of the laser beam passes through the transmissive cover, the inclination of the inner surface of the transmissive cover with respect to the incident axis of the laser beam and the inclination of the outer surface of the transmissive cover with respect to the incident axis of the laser beam are the same.

[0054] Furthermore, in the cross sections shown in FIGS. 8 and 9, the difference between the inclination of the inner surface 62 of the transmissive cover 60 with respect to the incident axis and the inclination of the outer surface 63 of the transmissive cover 60 with respect to the incident axis in the optical path of the laser beam L is larger in the portion where the distance from the light projecting unit 20 in the direction of the optical axis AX in the transmissive cover 60 is shorter. For example, in FIG. 8, the difference between the inclination of the inner surface 62 with respect to the incident axis and the inclination of the outer surface 63 with respect to the incident axis in the optical path of the laser beam L passing through point P2 is larger than the difference between the inclination of the inner surface 62 with respect to the incident axis and the inclination of the outer surface 63 with respect to the incident axis in the optical path of the laser beam L passing through point P1.

[0055] FIG. 10 is a schematic diagram showing the traveling directions of the laser beams L1 to L3 of the lidar device 10. The laser beams L1 to L3 are indicated by the central axes of the light beams of the laser beams L1 to L3. Note that FIG. 10 shows an overview of the traveling directions of the laser beams L1 to L3, and the detailed refraction patterns shown in the enlarged cross-sectional view of FIG. 9 are omitted.

[0056] The emission axes of the laser beams L1 to L3 each have a positive inclination with respect to the incident axis (horizontal) of the laser beams L1 to L3. And the inclination of the emission axis of the laser beam L2 with respect to the incident axis of the laser beam L2 is larger than the inclination of the emission axis of the laser beam L1 with respect to the incident axis of the laser beam L1. The inclination of the emission axis of the laser beam L3 with respect to the incident axis of the laser beam L3 is larger than the inclination of the emission axis of the laser beam L2 with respect to the incident axis of the laser beam L2. That is, in the cross section shown in FIG. 10, the positive inclinations of the respective emission axes of the laser beams L1 to L3 with respect to the incident axis are such that the laser beam (for example, the laser beam L3) incident on the transmission cover 60 at a lower position (a position closer to the light projecting unit 20) in the height direction (the direction of the optical axis AX) is larger. The inclination of the inner surface 62 and the inclination of the outer surface 63 of the transmission cover 60 are set.

[0057] FIG. 11 is a diagram showing the simulation results of the respective light beams LF1 and LF2 of the laser beams at the rotation mirror angles 0 [°] and 90 [°] in the comparative example. The comparative example is obtained by removing the transmission cover 60B from the lidar device 10B in FIG. 4. Here, as an example, the height of each light beam LF1 and LF2 of each laser beam is shown at the position of the maximum distance (10 [m]) at which the lidar device 10B can measure the distance to the object. FIG. 11(a) shows the light beam LF1 of the laser beam when the rotation mirror angle is 0 [°], which corresponds to the light beam LF1 of the laser beam in FIG. 4. FIG. 11(b) shows the light beam LF2 of the laser beam when the rotation mirror angle is 90 [°], which corresponds to the light beam LF2 of the laser beam in FIG. 4. As shown in FIG. 4, the position in the height direction of the laser beam reflected by the rotation mirror 50 and traveling toward the monitoring area A changes depending on the rotation position of the rotation mirror 50. Therefore, the height of the light beam LF1 of the laser beam in FIG. 11(a) is higher by the height h than the height of the light beam LF2 of the laser beam in FIG. 11(b).

[0058] FIG. 12 is a diagram showing simulation results of the light beams LF1 and LF2 of the laser beams L1 and L2 at the rotation mirror angles of 0[°] and 90[°] in the present embodiment. Here, as an example, the height of the light beams LF1 and LF2 of the laser beams L1 and L2 is shown at the position of the maximum distance (10 [m]) at which the lidar device 10 can measure the distance to an object. FIG. 12(a) shows the light beam LF1 of the laser beam L1 when the rotation mirror angle is 0[°], which corresponds to the light beam of the laser beam L1 in FIG. 10. FIG. 12(b) shows the light beam LF2 of the laser beam L2 when the rotation mirror angle is 90[°], which corresponds to the light beam of the laser beam L2 in FIG. 10. As shown in FIG. 10, the position in the height direction of the laser beam reflected by the rotation mirror 50 and directed toward the transmission cover 60 changes depending on the rotation position of the rotation mirror 50. And the inclination of the emission axis of the laser beam L2 with respect to the incident axis (horizontal) of the laser beam L2 is larger than the inclination of the emission axis of the laser beam L1 with respect to the incident axis (horizontal) of the laser beam L1. For this reason, at the position of the maximum distance, the height of the light beam LF1 of the laser beam L1 in FIG. 12(a) is substantially equal to the height of the light beam LF2 of the laser beam L2 in FIG. 12(b). Note that the inclination of the emission axis of the laser beam L3 with respect to the incident axis (horizontal) of the laser beam L3 is larger than the inclination of the emission axis of the laser beam L2 with respect to the incident axis (horizontal) of the laser beam L2. For this reason, in one example, at the position of the maximum distance, the height of the light beam LF1 of the laser beam L1 is substantially equal to the height of the light beam LF3 of the laser beam L3.

[0059] The present embodiment described in detail above has the following advantages.

[0060] · In each cross-section that includes the central axis CL and passes through the range 61 through which the laser light L in the transmissive cover 60 passes, the inner surface 62 and the outer surface 63 of the transmissive cover 60 have a positive inclination with respect to the incident axis, which is the central axis of the light beam of the laser light L incident from the rotary mirror 50 to the transmissive cover 60. In the optical path where the light beam of the laser light L passes through the transmissive cover 60, the inclination of the outer surface 63 of the transmissive cover 60 with respect to the incident axis is smaller than the inclination of the inner surface 62 of the transmissive cover 60 with respect to the incident axis. For this reason, when the incident axis is horizontal, the emission axis, which is the central axis of the light beam of the laser light L emitted from the transmissive cover 60, can be inclined upward from the horizontal. Therefore, it is possible to suppress the lower part of the light beam of the laser light L advancing to the monitoring area A at the lowest height from hitting the ground G far away, and it is possible to suppress misdetecting the ground G (the surface existing below the monitoring area A) as an object.

[0061] · In each of the above cross-sections, the difference between the inclination of the inner surface 62 of the transmissive cover 60 with respect to the incident axis of the laser light L in the optical path of the laser light L and the inclination of the outer surface 63 of the transmissive cover 60 with respect to the incident axis is larger in the part where the distance from the light projecting unit 20 in the direction of the optical axis AX (height direction) in the transmissive cover 60 is short (low). That is, in each of the above cross-sections, the inclination of the inner surface 62 of the transmissive cover 60 and the inclination of the outer surface 63 of the transmissive cover 60 are set such that the positive inclination of the emission axis of the laser light L with respect to the incident axis of the laser light L becomes larger for the laser light L3 incident on the transmissive cover 60 at a position closer to the light projecting unit 20 in the direction of the optical axis AX. According to such a configuration, when the incident axis of the laser light L is horizontal, the emission axis of the laser light L can be inclined more upward for the laser light L3 incident on the part where the distance from the light projecting unit 20 in the direction of the optical axis AX in the transmissive cover 60 is short. Therefore, while suppressing excessively inclining the emission axis of the laser light L1, which has a low possibility of hitting the ground G, upward, the emission axis can be inclined upward more for the laser light L3, which has a high possibility of hitting the ground G.

[0062] · In each of the above cross-sections, the outer surface 63 of the transmissive cover 60 has a shape obtained by translating the inner surface 62 of the transmissive cover 60 in the direction of the incident axis of the laser beam L (horizontal direction). For this reason, at positions where the distances (heights) from the light projecting unit 20 in the direction of the optical axis AX are the same on the inner surface 62 and the outer surface 63 of the transmissive cover 60, the inclination of the inner surface 62 of the transmissive cover 60 and the inclination of the outer surface 63 are the same. Here, the transmissive cover 60 has a refractive index greater than the refractive index of air, and in each of the above cross-sections, the inner surface 62 and the outer surface 63 of the transmissive cover 60 have a positive inclination with respect to the incident axis of the laser beam L. For this reason, when the laser beam L enters from the air into the transmissive cover 60, the refraction angle θ2 is smaller than the incident angle θ1 of the laser beam L, and the laser beam L refracts in the direction approaching the light projecting unit 20 in the direction of the optical axis AX. And in each of the above cross-sections, the inclination of the inner surface 62 (that is, the outer surface 63) of the transmissive cover 60 with respect to the incident axis of the laser beam L becomes smaller as the inner surface 62 closer to the light projecting unit 20 in the direction of the optical axis AX. Therefore, in the optical path through which the light beam of the laser beam L passes through the transmissive cover 60 (on the traveling path of the laser beam L), the inclination of the outer surface 63 of the transmissive cover 60 with respect to the incident axis of the laser beam L can be made smaller than the inclination of the inner surface 62 of the transmissive cover 60 with respect to the incident axis of the laser beam L.

[0063] ·In each cross-section including the central axis CL and passing through the range 61 through which the laser light passes in the transmissive cover 60, the shape of the inner surface 62 of the transmissive cover 60 is a parabola that reflects a part of the laser light traveling from the rotary mirror 50 toward the inner surface 62 and reflected by the inner surface 62 toward the focal point F set at a position farther from the rotary mirror 50 than the light-receiving unit 30 in the direction of the optical axis AX. That is, by forming the shape of the inner surface 62 of the transmissive cover 60 as a parabola in each of the above cross-sections, even if the position of the laser light reflected by the rotary mirror 50 and traveling toward the transmissive cover 60 changes in the direction of the optical axis AX, the laser light reflected by the transmissive cover 60 can be reflected toward the focal point F of the parabola. And the lidar device 10 includes an outer peripheral surface 41c (reflection suppression portion) of the support base 41 that suppresses the reflection of the irradiated laser light at the position where the laser light (inner surface reflected light) reflected by the inner surface 62 of the transmissive cover 60 is irradiated. Therefore, by irradiating the outer peripheral surface 41c with the inner surface reflected light, reflection from the outer peripheral surface 41c can be suppressed, and entry of the inner surface reflected light into the light-receiving unit 30 can be suppressed.

[0064] ·The focal point F of the above parabola is set at a position farther from the light-receiving unit 30 (with respect to the light-receiving unit 30) than the rotary mirror 50 in the direction of the optical axis AX. Therefore, while avoiding reflecting the inner surface reflected light by the transmissive cover 60 toward the rotary mirror 50, the inner surface reflected light can be reflected to the side away from the light-receiving unit 30 in the direction of the optical axis AX. And although a part of the inner surface reflected light irradiated on the outer peripheral surface 41c is diffusely reflected by the outer peripheral surface 41c, the amount of the diffusely reflected inner surface reflected light entering the light-receiving unit 30 decreases as the outer peripheral surface 41c is farther from the light-receiving unit 30. Therefore, entry of the inner surface reflected light into the light-receiving unit 30 can be effectively suppressed.

[0065] · The outer peripheral surface 41c of the support base 41 is disposed at a position closer to the portion 62a of the transmission cover 60 than the light receiving portion 30 and the rotary mirror 50 in the horizontal direction (the direction in which the laser light travels from the rotary mirror 50 to the transmission cover 60). According to such a configuration, the internally reflected light does not pass in front of the light receiving portion 30 before reaching the outer peripheral surface 41c, and the entry of the internally reflected light into the light receiving portion 30 can be suppressed. Also, in the horizontal direction, since the outer peripheral surface 41c is disposed in front of the light receiving portion 30 and the rotary mirror 50 with respect to the transmission cover 60, the arrangement of the components within the lidar device 10 for passing the internally reflected light from the transmission cover 60 to the outer peripheral surface 41c becomes easy. Therefore, the degree of freedom in arranging the components within the lidar device 10 can be improved.

[0066] · The focal point F is set at a position closer to the transmission cover 60 than the outer peripheral surface 41c in the direction in which the laser light travels from the rotary mirror 50 to the transmission cover 60. According to such a configuration, the internally reflected light can be concentrated in front of the outer peripheral surface 41c, and the increase in the intensity of the laser light irradiated onto the outer peripheral surface 41c can be suppressed. Therefore, the entry of the internally reflected light into the light receiving portion 30 can be further suppressed.

[0067] · The lidar device 10 includes a support base 41 that supports the rotary mirror 50 and the motor 42, and the outer peripheral surface 41c (reflection suppression portion) is a part of the support base 41 (integrated with the support base 41). According to such a configuration, a reflection suppression portion for suppressing the reflection of the internally reflected light can be arranged by using the support base 41 that supports the rotary mirror 50 and the motor 42.

[0068] · The lidar device 10 includes a light shielding partition member 29 that partitions the light projecting portion 20 and the light receiving portion 30. According to such a configuration, the leakage of the laser light projected by the light projecting portion 20 to the light receiving portion 30 can be suppressed by the light shielding partition member 29.

[0069] · In the direction in which the laser light is projected from the light projecting unit 20, the partition member 29 protrudes 0 to 2 [mm] from the end 22a of the light projecting lens 22 (light projecting unit 20). According to such a configuration, while suppressing the reflection light reflected by the rotary mirror 50 and heading toward the light receiving unit 30 from being blocked by the partition member 29, the laser light leaking from the light projecting unit 20 toward the light receiving unit 30 can be effectively blocked by the partition member 29.

[0070] In addition, the above-described embodiment can also be implemented with the following modifications. For the parts that are the same as those in the above-described embodiment, the same reference numerals are given and the description thereof is incorporated by reference.

[0071] · In each of the above cross-sections, the outer surface 63 of the transmission cover 60 may be shaped such that the inner surface 62 of the transmission cover 60 is translated slightly upward from the direction of the incident axis of the laser light L. Even with such a configuration, in the optical path where the light beam of the laser light L passes through the transmission cover 60, the inclination of the outer surface 63 of the transmission cover 60 with respect to the incident axis of the laser light L can be made smaller than the inclination of the inner surface 62 of the transmission cover 60 with respect to the incident axis of the laser light L. In each of the above cross-sections, the outer surface 63 of the transmission cover 60 may be shaped such that it is translated upward (the side away from the light projecting unit 20 in the direction of the optical axis AX) from the direction of the optical path of the laser light L inside the transmission cover 60 (the direction in which the laser light L refracts and advances at the refraction angle θ2).

[0072] · In each of the above cross-sections, the shape of the inner surface 62 of the transmission cover 60 is not limited to a parabola (parabolic shape), and may be formed as a quadratic curve or a quartic curve having the origin O as the vertex. In each of the above cross-sections, if the inclination of the inner surface 62 (that is, the outer surface 63) of the transmission cover 60 with respect to the incident axis of the laser light L becomes smaller as the inner surface 62 closer to the light projecting unit 20 in the direction of the optical axis AX (height direction) is, the laser light L3 incident at a lower position of the transmission cover 60 can incline the emission axis of the laser light L more upward.

[0073] · At a position at a distance shorter or longer than the maximum distance (e.g., 10 [m]) at which the lidar device 10 can measure the distance to an object, the heights of the light beams LF1, LF2, and LF3 of the respective laser lights L1, L2, and L3 may be substantially equal. Also, at the position of the maximum distance (e.g., 10 [m]), among the light beams LF1, LF2, and LF3 of the respective laser lights L1, L2, and L3, the heights of only two light beams may be substantially equal. Further, at a position at a distance shorter or longer than the maximum distance, among the light beams LF1, LF2, and LF3 of the respective laser lights L1, L2, and L3, the heights of only two light beams may be substantially equal.

[0074] · As shown in FIG. 13, in each cross section including the central axis CL and passing through the range where the laser light passes through the transmission cover 160, the inner surface 162 and the outer surface 163 of the transmission cover 160 can also be formed in a straight line. The inclination of the inner surface 162 with respect to the incident axis (horizontal) of the laser light is a constant first inclination k1. The inclination of the outer surface 163 with respect to the incident axis (horizontal) of the laser light is a constant second inclination k2 smaller than the first inclination k1 (k1 > k2). According to such a configuration, the inclination of the inner surface 162 and the inclination of the outer surface 163 satisfy the relationship shown in FIG. 7. For this reason, with respect to the incident axis of the laser light, the emission axis of the laser light has a positive inclination. That is, when the incident axis is horizontal, the emission axis of the laser light can be inclined upward from the horizontal. Therefore, it is possible to suppress the lower part of the light beam of the laser light traveling to the monitoring area A at the lowest height from hitting the ground G in the distance, and it is possible to suppress erroneously detecting the ground G (the surface existing below the monitoring area A) as an object. In the above configuration, in each of the above cross sections, the positive inclination of the emission axis of the laser light with respect to the incident axis of the laser light is constant regardless of the height of the laser light incident on the transmission cover 60. Also, in each of the above cross sections, the inclination of the inner surface 162 and the inclination of the outer surface 163 may change in a plurality of steps in the middle in the height direction of the transmission cover 160. Even in that case, it is sufficient that the inclination of the outer surface 163 at each step with respect to the incident axis (horizontal) of the laser light is smaller than the inclination of the inner surface 162 at each step.

[0075] · The surface existing below the monitoring area A may be not only the ground G but also the floor surface. That is, the lidar device 10 may scan a position close to the floor surface (a position at a predetermined height) substantially horizontally with laser light.

[0076] · In the direction in which the laser light is projected from the light projecting unit 20, the length by which the partition member 29 protrudes beyond the end 22a of the light projecting lens 22 (light projecting unit 20) may be -1 to 3 [mm]. Also, if there is no possibility of the laser light leaking from the light projecting unit 20 to the light receiving unit 30, the partition member 29 can be omitted.

[0077] · By moving the origin O of the xy plane upward (the side away from the light projecting unit 20 and the light receiving unit 30 in the direction of the optical axis AX), the focus F(0, a) of the parabola y = (x^2) / 4a can be moved upward. Then, the internally reflected light by the transmission cover 60 can be irradiated onto the lower surface (inner surface) of the lid 12, and the lower surface of the lid 12 can also constitute the reflection suppression portion.

[0078] · The rotating mirror 50 can also be formed by a concave mirror. Also in that case, the laser light reflected by the rotating mirror 50 can be irradiated onto the transmission cover 60 horizontally (substantially horizontally). Even in that case, if it exceeds the focus where the light beam of the laser light converges, the light beam of the laser light gradually becomes thicker. In short, the light beam of the laser light passing through the transmission cover 60 and advancing to the monitoring area A may gradually become thicker.

[0079] In addition, the above-described embodiments and their modification examples can also be implemented in combination within a combinable range.

Explanation of Reference Numerals

[0080] 10... Lidar device, 20... Light projecting unit, 21... Laser diode, 22... Light projecting lens, 30... Light receiving unit, 31... Photodiode, 32... Light receiving lens, 40... Rotating reflection mechanism, 50... Rotating mirror, 60... Transmission cover, 61... Transmission range, 62... Inner surface, 63... Outer surface, 160... Transmission cover, 162... Inner surface, 163... Outer surface.

Claims

1. A light projecting unit that projects a laser beam, A light receiving unit that receives the reflected light, which is the laser beam reflected by an object, A rotating mirror that rotates about a predetermined rotation axis, A transmission cover that has a refractive index greater than the refractive index of air and transmits the laser beam traveling from the rotating mirror to the outside and the reflected light traveling from the outside to the rotating mirror, A lidar device including the above components, wherein the light beam of the laser beam passing through the transmission cover and advancing to the monitoring area gradually becomes thicker, The light projecting unit and the light receiving unit are arranged side by side facing the rotating mirror, The light projection axis of the laser beam projected by the light projecting unit is non-coaxial with the rotation axis, The rotating mirror reflects the laser beam from the light projecting unit toward the transmission cover and reflects the reflected light from the transmission cover toward the light receiving unit, In each cross section including the rotation axis and passing through the range where the laser beam passes through the transmission cover, the inner surface and the outer surface of the transmission cover have a positive inclination with respect to the incident axis, which is the central axis of the light beam of the laser beam incident from the rotating mirror to the transmission cover. In the optical path where the light beam of the laser beam passes through the transmission cover, the inclination of the outer surface of the transmission cover with respect to the incident axis is smaller than the inclination of the inner surface of the transmission cover with respect to the incident axis. A lidar device.

2. In each of the cross sections, the difference between the inclination of the inner surface of the transmission cover with respect to the incident axis in the optical path and the inclination of the outer surface of the transmission cover with respect to the incident axis is greater in a portion where the distance from the light projecting unit in the direction of the light projection axis in the transmission cover is shorter. The lidar device according to claim 1.

3. A light projecting unit that projects a laser beam, A light receiving unit that receives the reflected light, which is the laser beam reflected by an object, A rotating mirror that rotates about a predetermined rotation axis, A transmission cover that has a refractive index greater than the refractive index of air and transmits the laser beam traveling from the rotating mirror to the outside and the reflected light traveling from the outside to the rotating mirror, A lidar device including the above components, wherein the light beam of the laser beam passing through the transmission cover and advancing to the monitoring area gradually becomes thicker, The light projecting unit and the light receiving unit are arranged side by side facing the rotating mirror, The light projection axis of the laser beam projected by the light projecting unit is non-coaxial with the rotation axis, The rotary mirror reflects the laser light from the light projecting unit toward the transmissive cover and reflects the reflected light from the transmissive cover toward the light receiving unit. A lidar device, wherein in each cross-section including the rotation axis and passing through a range where the laser light passes through the transmissive cover, the inclination of the inner surface of the transmissive cover and the inclination of the outer surface of the transmissive cover are set such that the central axis of the light beam of the laser light exiting the transmissive cover has a positive inclination with respect to the incident axis, which is the central axis of the light beam of the laser light incident from the rotary mirror to the transmissive cover. **Claim 4** The lidar device according to claim 3, wherein in each cross-section, the inclination of the inner surface of the transmissive cover and the inclination of the outer surface of the transmissive cover are set such that the positive inclination of the central axis of the light beam of the laser light exiting the transmissive cover with respect to the incident axis is greater for the laser light incident on the transmissive cover at a position closer to the light projecting unit in the direction of the light projection axis. **Claim 5** The lidar device according to any one of claims 1 to 4, wherein in each cross-section, the inclination of the inner surface of the transmissive cover with respect to the incident axis becomes smaller as the inner surface closer to the light projecting unit in the direction of the light projection axis, and the outer surface of the transmissive cover has a shape obtained by translating the inner surface of the transmissive cover in the direction of the incident axis. **Claim 6** The lidar device according to any one of claims 1 to 4, wherein in each cross-section, the inner surface of the transmissive cover is formed as a straight line having a constant first inclination with respect to the incident axis, and the outer surface of the transmissive cover is formed as a straight line having a second inclination that is smaller than the first inclination and is constant with respect to the incident axis.

Images