Laser radar device

Abstract

To prevent laser light from entering a light receiving unit when a portion of the laser light heading toward a transparent cover from a rotating mirror is reflected by the transparent cover.SOLUTION: A light emitting unit (20) and a light receiving unit (30) are arranged side by side toward a rotating mirror (50), and a light projection axis (AX) of the laser light emitted by the light emitting unit is non-coaxial with a rotation axis (CL) of the rotating mirror (50). In each cross-section that includes the rotation axis and passes through a range (61) through which the laser light passes in a transparent cover (60), the shape of an inner surface (62) of the transparent cover is formed in a parabola that reflects a portion of the laser light heading from the rotating mirror toward the inner surface and reflected from the inner surface toward a focal point (F) set at a position apart from the light receiving unit relative to the rotating mirror in the direction of the light projection axis. The laser radar device includes a reflection suppression part (41c) that suppresses reflection of the irradiation laser light at a position of irradiation with the laser light reflected from the inner surface.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a laser radar device. [Background technology]

[0002] In some laser radar devices that use laser light to detect the distance to a detection object, the direction in which the light projector faces and the direction in which the light receiver faces form a right angle. For example, the laser radar device described in Patent Document 1 is provided with a fixed mirror having a reflective surface inclined with respect to the optical axis of the laser light from the light projector. Then, a through passage through which the laser light passes is formed in the fixed mirror, and the laser light from the light projector passes through the through passage, while the reflected light from the detection object is reflected by the reflective surface of the fixed mirror toward the light receiver.

[0003] Furthermore, the laser radar device described in Patent Document 1 is provided with a rotating mirror that rotates around a rotation axis that is coaxial with the optical axis of the laser light passing through the through passage of the fixed mirror. The rotating mirror reflects the laser light toward the outside and reflects the reflected light from the detection object toward the fixed mirror, thereby performing horizontal scanning with the laser light. The optical axis (light projection axis) of the laser light passing from the light projecting unit through the through passage of the fixed mirror toward the rotating mirror, the rotation axis of the rotating mirror, and the optical axis (light receiving axis) of the reflected light from the rotating mirror toward the fixed mirror are all coaxial.

[0004] The laser light reflected by the rotating mirror toward the outside passes through the transparent cover and is projected to the outside. The shape of the transparent cover is designed so that when a part of the laser light traveling from the rotating mirror toward the transparent cover is reflected by the transparent cover, the laser light does not enter the light receiving unit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2011-141261 A Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, in the laser radar device described in Patent Document 1, the direction in which the light receiving unit faces is perpendicular to the light receiving axis, so a fixed mirror is required to reflect the reflected light from the rotating mirror toward the light receiving unit. In response to this, it is possible to omit the fixed mirror by arranging the light projecting unit and the light receiving unit side by side toward the rotating mirror above or below, and making the light projecting axis non-coaxial with the rotation axis of the rotating mirror. However, in this case, since the light projecting axis is non-coaxial with the rotation axis of the rotating mirror, the position where the laser light from the light projecting unit is reflected by the rotating mirror changes depending on the rotation position of the rotating mirror. Therefore, the height of the laser light reflected by the rotating mirror and heading toward the transparent cover changes depending on the rotation position of the rotating mirror. Therefore, compared to the laser radar device described in Patent Document 1 in which the height of the laser light reflected by the rotating mirror and heading toward the transparent cover is constant, it becomes difficult to design the shape of the transparent cover so that some of the laser light reflected by the transparent cover does not enter the light receiving unit.

[0007] The present invention has been made to solve these problems, and its main object is to prevent laser light from entering the light-receiving unit when part of the laser light traveling from the rotating mirror to the transparent cover is reflected by the transparent cover in a laser radar device in which the light-projecting unit and the light-receiving unit are arranged side by side facing a rotating mirror and the light-projecting axis is non-coaxial with the rotation axis of the rotating mirror. [Means for solving the problem]

[0008] The first means for solving the above problem is a light projection unit that projects a laser beam; a light receiving unit that receives reflected light, which is the laser light reflected by an object; a rotating mirror that rotates around a predetermined rotation axis; a transmission cover that 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 laser radar device comprising: the light projecting unit and the light receiving unit are arranged side by side facing the rotating mirror, a projection 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 transparent cover and reflects the reflected light from the transparent cover toward the light-receiving unit, In each cross section including the rotation axis and passing through a range in the transparent cover through which the laser light passes, the shape of the inner surface of the transparent cover is formed into a parabola that reflects a part of the laser light traveling from the rotating mirror to the inner surface and reflected by the inner surface, toward a focal point set at a position farther away from the light receiving unit than the rotating mirror in the direction of the light projection axis, A reflection suppression portion that suppresses reflection of the irradiated laser light is provided at a position where the laser light reflected by the inner surface is irradiated.

[0009] According to the above configuration, the light-projecting unit projects a laser beam, and the light-receiving unit receives reflected light, which is the laser beam reflected by an object. The rotating mirror rotates about a predetermined rotation axis. The transparent cover transmits the laser beam traveling from the rotating mirror to the outside and the reflected light traveling from the outside to the rotating mirror.

[0010] Here, the light-projecting unit and the light-receiving unit are arranged side by side facing the rotating mirror. Therefore, it is possible to omit a fixed mirror that reflects the reflected light from the rotating mirror toward the light-receiving unit and a fixed mirror that reflects the laser light from the light-projecting unit toward the rotating mirror. However, the projection axis of the laser light projected by the light-projecting unit is not coaxial with the rotation axis, and the rotating mirror reflects the laser light from the light-projecting unit toward the transparent cover. Therefore, the position at which the laser light from the light-projecting unit is irradiated onto the rotating mirror changes depending on the rotation position of the rotating mirror. In turn, the position in the direction of the projection axis of the laser light reflected by the rotating mirror toward the transparent cover changes depending on the rotation position of the rotating mirror.

[0011] In this regard, in each cross section including the rotation axis and passing through the range through which the laser light in the transparent cover passes, the shape of the inner surface of the transparent cover is formed into a parabola that reflects a part of the laser light that travels from the rotating mirror to the inner surface and is reflected by the inner surface toward a focal point set at a position farther away from the light receiving unit than the rotating mirror in the direction of the light projection axis. That is, by forming the shape of the inner surface of the transparent cover into a parabola in each cross section, even if the position in the direction of the light projection axis of the laser light reflected by the rotating mirror and traveling toward the transparent cover changes, the laser light reflected by the transparent cover can be reflected toward the focal point of the parabola. In addition, a reflection suppression unit that suppresses reflection of the irradiated laser light (hereinafter referred to as "internal reflection light") is provided at a position where the laser light reflected by the inner surface of the transparent cover is irradiated. Therefore, reflection from the reflection suppression unit can be suppressed by irradiating the internal reflection light to the reflection suppression unit, and the internal reflection light can be suppressed from entering the light receiving unit.

[0012] Furthermore, the focus of the parabola is set at a position farther away from the light receiving unit (relative to the light receiving unit) in the direction of the light projection axis than the rotating mirror. Therefore, the internally reflected light can be reflected toward the side away from the light receiving unit in the direction of the light projection axis while avoiding reflection toward the rotating mirror. Although a portion of the internally reflected light irradiated to the reflection suppression unit is diffusely reflected by the reflection suppression unit, the amount of the diffusely reflected internally reflected light that enters the light receiving unit decreases as the reflection suppression unit is farther away from the light receiving unit. Therefore, it is possible to effectively suppress the internally reflected light from entering the light receiving unit.

[0013] If the reflection suppression unit, to which the internally reflected light is irradiated, is located farther from the transparent cover (relative to the transparent cover) than the light receiving unit, the internally reflected light may enter the light receiving unit when passing in front of it. Also, if the reflection suppression unit is located far from the transparent cover, it becomes difficult to arrange the components in the laser radar device to pass the internally reflected light from the transparent cover to the reflection suppression unit.

[0014] In this regard, in the second means, the reflection suppression unit is disposed at a position closer to the transparent cover than the light receiving unit and the rotating mirror in the direction in which the laser light travels from the rotating mirror to the transparent cover. With this configuration, the internally reflected light does not pass in front of the light receiving unit before reaching the reflection suppression unit, and it is possible to suppress the internally reflected light from entering the light receiving unit. In addition, since the reflection suppression unit is disposed in front of the light receiving unit and the rotating mirror with respect to the transparent cover, it is easy to arrange each component in the laser radar device to pass the internally reflected light from the transparent cover to the reflection suppression unit. Therefore, it is possible to improve the degree of freedom in arranging each component in the laser radar device.

[0015] When the focus of the parabola on which the internally reflected light is concentrated is set on the surface of the reflection suppression unit, the internally reflected light is concentrated on the surface of the reflection suppression unit, and the intensity of the laser light irradiated to the reflection suppression unit increases. In this case, the intensity of the laser light reflected by the reflection suppression unit is not sufficiently reduced, and there is a risk that the laser light reflected by the reflection suppression unit will enter the light receiving unit.

[0016] In this regard, in the third means, the focal point is set at a position closer to the transparent cover than the reflection suppression unit in the direction in which the laser light travels from the rotating mirror to the transparent cover. With this configuration, the internally reflected light can be concentrated in front of the reflection suppression unit, and the intensity of the laser light irradiated to the reflection suppression unit can be prevented from increasing. Therefore, the internally reflected light can be further prevented from entering the light receiving unit.

[0017] In general, a drive unit that rotates the rotating mirror is provided on the opposite side of the rotating mirror from the light projector, and the rotating mirror and the drive unit are supported by a support member on the opposite side of the rotating mirror from the light projector.

[0018] In this regard, the fourth aspect of the present invention includes a drive unit that rotates the rotating mirror, and a support member that supports the rotating mirror and the drive unit, and the reflection suppression unit is integrated with the support member. With this configuration, the support member that supports the rotating mirror and the drive unit can be used to position the reflection suppression unit that suppresses reflection of internally reflected light.

[0019] In a configuration in which the light-projecting unit and the light-receiving unit are arranged side by side facing the rotating mirror, there is a risk that the laser light projected by the light-projecting unit may leak to the light-receiving unit.

[0020] In this regard, the fifth aspect of the present invention includes a light-shielding partition member that separates the light-projecting unit and the light-receiving unit. With this configuration, the light-shielding partition member can prevent the laser light projected by the light-projecting unit from leaking into the light-receiving unit.

[0021] If the length of the light-shielding partition member separating the light-projecting unit and the light-receiving unit is too short in the direction in which the laser light is projected from the light-projecting unit, the effect of the partition member blocking the laser light leaking from the light-projecting unit toward the light-receiving unit decreases. On the other hand, if the length of the partition member is too long in the direction in which the laser light is projected from the light-projecting unit, there is a risk that the partition member will block the reflected light reflected by the rotating mirror toward the light-receiving unit.

[0022] In this regard, in the sixth aspect, the partition member protrudes 0 to 2 mm from the end of the light projecting unit in the direction in which the laser light is projected from the light projecting unit. With this configuration, the partition member can effectively block the laser light leaking from the light projecting unit toward the light receiving unit while preventing the reflected light reflected by the rotating mirror from being blocked by the partition member toward the light receiving unit. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view showing an overview of a laser radar device. [Diagram 2] FIG. 1 is a schematic diagram showing a laser radar device of a comparative example. [Diagram 3]FIG. 1 is a schematic diagram showing a laser radar device of a comparative example. [Figure 4] 4 is a cross-sectional view showing a state in which internally reflected light is irradiated onto a reflection suppressing portion. FIG. [Diagram 5] FIG. 11 is a cross-sectional view showing an outline of a modified example of the laser radar device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, an embodiment in which the present invention is embodied in a laser radar device that detects an object that has entered a surveillance area will be described with reference to the drawings.

[0025] As shown in Fig. 1, the laser radar device 10 includes a housing 11, a light projecting unit 20, a light receiving unit 30, a rotary reflecting mechanism 40, a transparent cover 60, and a lid 12. Note that in Fig. 1, the direction of the optical axis AX and the direction of the central axis CL are set to the up-down direction, and a case where horizontal scanning is performed by laser light is described as an example, but the arrangement direction of the laser radar device 10 is not limited to this.

[0026] The housing 11 is formed in a hollow rectangular parallelepiped (box-shaped) shape with an open upper side (top surface). A light projecting unit 20, a light receiving unit 30, and a partition member 29 are housed inside the housing 11. The light projecting unit 20 and the light receiving unit 30 are arranged side by side in the horizontal direction.

[0027] 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 pulse current from a drive circuit (not shown) under the control of a control circuit (not shown), and intermittently emits a pulse laser light corresponding to the pulse current upward. The laser light is, for example, an infrared laser, a visible laser, an ultraviolet laser, or the like. A light projecting lens 22 is provided on an optical axis AX of the laser light emitted from the laser diode 21. The light projecting lens 22 is configured as a collimating lens, and converts the laser light from the laser diode 21 into a parallel light. 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, toward the rotating mirror 50 of the rotary reflection mechanism 40. The light projecting unit 20 projects the laser light upward, that is, toward the rotating mirror 50.

[0028] A cylindrical transmission cover 60 is attached to the upper part of the housing 11. The transmission cover 60 is made of resin, glass, or the like that transmits laser light. The rotation reflection mechanism 40 is housed inside the transmission cover 60. The upper opening of the transmission cover 60 is closed by the lid 12.

[0029] The rotary reflection mechanism 40 includes a support base 41, a motor 42, an axis portion 43, a rotary mirror 50, and the like. The support base 41 (support member) is formed in a columnar or cylindrical shape centered on a central axis CL, and is fixed to, for example, the housing 11. The motor 42 (drive unit) rotates the axis portion 43 to rotate the rotary mirror 50 connected to the axis portion 43. The axis portion 43 and the rotary mirror 50 rotate about the central axis CL (a 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. The support base 41 may also be fixed to the upper part of the lid 12 or the transparent cover 60.

[0030] The rotating mirror 50 is disposed so as to intersect with the optical axis AX, and deflects (reflects) the laser light from the laser diode 21 (light projecting unit 20) toward the space outside the transparent cover 60. The rotating mirror 50 also deflects (reflects) the reflected light from an object present in the space outside the transparent cover 60 toward the photodiode 31 (light receiving unit 30). That is, the rotating mirror 50 reflects the laser light from the light projecting unit 20 toward the transparent cover 60, and reflects the reflected light from the transparent cover 60 toward the light receiving unit 30. The rotating mirror 50 is formed, for example, by a plane mirror. The rotating mirror 50 is inclined, for example, at an angle of 45° with respect to the vertical direction (optical axis AX), so that the laser light reflected by the rotating mirror 50 is irradiated in the horizontal direction.

[0031] The transmissive cover 60 transmits the laser light traveling from the rotating mirror 50 to the outside, and the reflected light traveling from an object (outside) to the rotating mirror 50. The detailed shape of the transmissive cover 60 will be described later.

[0032] The light receiving unit 30 includes a photodiode 31 and a light receiving lens 32. The light receiving unit 30 faces upward, toward the rotating mirror 50 of the rotary reflection mechanism 40. That is, the light projecting unit 20 and the light receiving unit 30 face in the same direction. The light receiving lens 32 collects the laser light reflected downward by the rotating mirror 50 and guides it to the photodiode 31. The optical axis (light receiving axis) of the reflected light from the rotating mirror 50 toward the photodiode 31 (light receiving unit 30) coincides with the central axis CL (they are coaxial). Meanwhile, 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 and reflected by an object, and converts it into an electric signal.

[0033] In a configuration in which the light-projecting unit 20 and the light-receiving unit 30 are arranged side by side facing the rotating mirror 50, there is a risk that the laser light projected by the light-projecting unit 20 may leak into the light-receiving unit 30. To address this issue, the laser radar device 10 is provided with a light-shielding partition member 29 that separates the light-projecting unit 20 and the light-receiving unit 30. The partition member 29 is formed in a plate shape and is arranged between the light-projecting unit 20 and the light-receiving unit 30.

[0034] If the length of the light-shielding partition member 29 separating the light-projecting unit 20 from the light-receiving unit 30 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), is too short, the effect of the partition member 29 blocking the laser light leaking from the light-projecting unit 20 toward the light-receiving unit 30 is reduced. On the other hand, if the length by which the partition member 29 protrudes toward the rotating mirror 50 in the direction of the optical axis AX and the central axis CL is too long, the reflected light reflected by the rotating mirror 50 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) from the end 22a of the light-projecting lens 22 (light-projecting unit 20) on the rotating mirror 50 side in the direction of the optical axis AX and the central axis CL.

[0035] A 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 to when the reflected light is received by the light receiving unit 30. In detail, the distance calculation unit calculates the distance from the laser radar device 10 to the object based on the principle of time of flight (TOF) in proportion to the elapsed time from when the laser light is projected to when the reflected light is received.

[0036] The laser light projected from the light-projecting unit 20 is reflected by the rotating mirror 50 and irradiated to the outside of the laser radar device 10 (monitoring area) through the transparent cover 60. If an object is present 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 transparent cover 60, is reflected by the rotating mirror 50, and is received by the light-receiving unit 30.

[0037] 2 is a schematic diagram showing a laser radar device 10A of a comparative example. This comparative example was devised by the inventor of the present application for comparison with this embodiment, and is not a publicly known technique. Note that the same parts as in this embodiment are denoted by the same reference numerals and the description thereof is incorporated herein.

[0038] In the comparative example shown in the figure, the central axis CL and the optical axis AX are coaxial. In each cross section including the optical axis AX, the shape of the inner surface of the transparent cover 60A is a straight line that is inclined so that the distance from the optical axis AX increases toward the upper part. The shape of the transparent cover 60A is symmetrical about 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 on the rotating mirror 50 does not change depending on the rotation position of the rotating mirror 50.

[0039] For example, when the rotating mirror 50 is in the rotation position indicated by the solid line, the laser light from the light projecting unit 20 is irradiated to the center of the rotating mirror 50 in the height direction (the direction of the optical axis AX). The laser light reflected by the rotating mirror 50 is irradiated to a point P11 on the inner surface of the transparent cover 60A, and a part of it is reflected and irradiated to a point P12 on the support base 41. The part of the support base 41 corresponding to the point P12 is a reflection suppression part that suppresses reflection of the irradiated laser light, such as a low reflection surface such as black or a diffuse reflection surface formed with fine irregularities. This makes it possible to suppress reflection of the laser light from the point P12, and to suppress the laser light reflected by the inner surface of the transparent cover 60A (hereinafter referred to as "inner reflection light") from entering the light receiving unit 30.

[0040] In addition, even when the rotating mirror 50 is rotated 180[°] from the rotation position shown by the solid line to the rotation position shown by the two-dot chain line, the laser light from the light projecting unit 20 is irradiated to the center of the rotating mirror 50 in the height direction. The laser light irradiated to the rotating mirror 50 travels to the left in the figure, but since the shape of the transparent cover 60A is symmetrical with respect to the optical axis AX, it is conveniently shown as the laser light traveling to the right. In the detection direction corresponding to the rotation position shown by the two-dot chain line, the laser light reflected by the rotating mirror 50 is irradiated to a point corresponding to the point P11 on the inner surface of the transparent cover 60A, and a part of it is reflected and irradiated to a point corresponding to the point P12 on the support base 41. In this case, reflection of the laser light from the point corresponding to the point P12 can be suppressed, and the light reflected on the inner surface by the transparent cover 60A can be suppressed from entering the light receiving unit 30.

[0041] As described above, the position in the height direction of the laser light reflected by the rotating mirror 50 and directed toward the transmissive cover 60A is constant regardless of the rotational position of the rotating mirror 50.

[0042] 3 is a schematic diagram showing a laser radar device 10B of a comparative example. This comparative example was devised by the inventor of the present application for comparison with this embodiment, and is not a publicly known technique. Note that the same parts as in this embodiment are given the same reference numerals and their explanations are incorporated herein.

[0043] In the comparative example shown in the figure, the central axis CL and the optical axis AX are not coaxial. The central axis CL and the optical axis AX are parallel and offset. In each cross section including the optical axis AX, the shape of the inner surface of the transparent cover 60A is a straight line that is inclined so that the distance from the optical axis AX increases toward the upper part. The shape of the transparent cover 60A is symmetrical about 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 on the rotating mirror 50 changes depending on the rotation position of the rotating mirror 50.

[0044] For example, when the rotating mirror 50 is in the rotation position indicated by the two-dot chain line, the laser light from the light projecting unit 20 is irradiated below the center of the rotating mirror 50 in the height direction (the direction of the optical axis AX). The laser light reflected by the rotating mirror 50 (for convenience, shown as laser light traveling in the right direction) is irradiated to a point corresponding to point P21 on the inner surface of the transparent cover 60B, and a part of it is reflected and irradiated to a point corresponding to point P22 on the support base 41. The part of the support base 41 corresponding to point P22 is a reflection suppression unit as in FIG. 2. This makes it possible to suppress reflection of the laser light from the point corresponding to point P22, and to suppress the light reflected internally by the transparent cover 60B from entering the light receiving unit 30.

[0045] Furthermore, when the rotating mirror 50 is rotated 180° from the rotation position indicated by the two-dot chain line to the rotation position indicated by the solid line, the laser light from the light-projecting unit 20 is irradiated above the center of the rotating mirror 50 in the height direction. The laser light reflected by the rotating mirror 50 is irradiated to point P23 on the inner surface of the transparent cover 60B, and a part of it is reflected and irradiated to a position outside the support base 41. In this case, the light reflected internally by the transparent cover 60B cannot be irradiated to the reflection suppression section of the support base 41, and there is a risk that the light reflected internally by the transparent cover 60A will enter the light-receiving unit 30.

[0046] As described above, the position in the height direction of the laser light reflected by the rotating mirror 50 and traveling toward the transparent cover 60B changes depending on the rotational position of the rotating mirror 50. Therefore, it becomes difficult to design the shape of the transparent cover 60B so that a part of the laser light reflected by the transparent cover 60B does not enter the light receiving unit 30.

[0047] In contrast, in this embodiment, as shown in FIG. 4, in each cross section including the central axis CL and passing through the range 61 in the transparent cover 60 through which the laser light passes, the shape of the inner surface 62 of the transparent cover 60 is formed into a parabola (parabolic). The outer peripheral surface 41c of the support base 41 constitutes a reflection suppression portion that suppresses reflection of the irradiated laser light, such as a low reflection surface such as black, or a diffuse 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 opposite side of the light projecting unit 20 and the light receiving unit 30 with respect to the rotating mirror 50. In the horizontal direction (the direction in which the laser light travels from the rotating mirror 50 to the transparent 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 unit 30 and the distance y4 from the central axis CL to the end of the rotating mirror 50. That is, the outer peripheral surface 41c (reflection suppression unit) is disposed in a position in the horizontal direction closer to the transparent cover 60 (more specifically, a portion 62a of the transparent cover 60 that is closest to the central axis CL) than the light receiving unit 30 and the rotating mirror 50. If the reflection suppression unit is disposed in a position farther away from the transparent cover 60 (with respect to the transparent cover 60) than the light receiving unit 30, there is a risk that the internally reflected light by the transparent cover 60 may enter the light receiving unit 30 when passing in front of the light receiving unit 30. Also, if the reflection suppression unit is disposed in a position farther away from the transparent cover 60, it becomes difficult to arrange the components in the laser radar device 10 to pass the internally reflected light from the transparent cover 60 to the reflection suppression unit.

[0048] The shape of the inner surface 62 of the transparent cover 60 will be described in detail. The cross section shown in FIG. 4 is an 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 in 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 expressed by the formula y=(x^2) / 4a. x^2 represents the square of x. The focus is F(0,a), and the formula 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 transparent cover 60 than the outer circumferential surface 41c (reflection suppression part) of the support base 41 in the horizontal direction (the direction in which the laser light travels from the rotating mirror 50 to the transparent cover 60). As a result, the shape of the inner surface 62 of the transparent cover 60 is formed into a parabola that reflects a portion of the laser light directed from the rotating mirror 50 toward the inner surface 62 and reflected by the inner surface 62, toward a focal point F set at a position farther away from the light receiving unit 30 than the rotating mirror 50, in the direction of the optical axis AX. That is, the inner surface 62 of the transparent cover 60 reflects the laser light toward the opposite side to the light projecting unit 20 and the light receiving unit 30 in the direction of the optical axis AX (light projection axis). Then, the outer peripheral surface 41c (reflection suppression unit) of the support base 41 is provided at a position where the laser light reflected by the inner surface 62 is irradiated.

[0049] In the figure, the relative relationship in which the position in the height direction of the laser light reflected by the rotating mirror 50 toward the transparent cover 60 changes depending on the rotation position of the rotating mirror 50 is shown as follows for convenience. That is, the rotation position of the rotating mirror 50 is fixed, and instead the position of the laser light irradiated from the light projector 20 to the rotating mirror 50 is changed. As a result, as shown by the arrow, the laser light reflected at each position of the rotating mirror 50 is conveniently shown as laser light traveling in the right direction. Each laser light reflected at each position of the rotating mirror 50 and traveling horizontally toward the transparent cover 60 is reflected toward the focal point F by the inner surface 62 of the transparent cover 60. Each laser light concentrated at the focal point F spreads slightly past the focal point F and is irradiated to the outer peripheral surface 41c of the support base 41. Then, the reflection of the laser light irradiated to the outer peripheral surface 41c is suppressed by the outer peripheral surface 41c as a reflection suppression unit. When the focal point F on which the light reflected internally by the transparent cover 60 is concentrated is set to the outer peripheral surface 41c, the light reflected internally is concentrated on the outer peripheral surface 41c, and the intensity of the laser light irradiated to the outer peripheral surface 41c increases. In that case, the intensity of the laser light reflected by the outer peripheral surface 41c is not sufficiently reduced, and the laser light reflected by the outer peripheral surface 41c may enter the light receiving unit 30.

[0050] The present embodiment described above in detail has the following advantages.

[0051] In each cross section including the central axis CL and passing through the range 61 through which the laser light in the transparent cover 60 transmits, the shape of the inner surface 62 of the transparent cover 60 is formed into a parabola that reflects a part of the laser light directed from the rotating mirror 50 to the inner surface 62 and reflected by the inner surface 62 toward a focal point F set at a position farther away from the light receiving unit 30 than the rotating mirror 50 in the direction of the optical axis AX. That is, by forming the shape of the inner surface 62 of the transparent cover 60 into a parabola in each of the cross sections, even if the position in the direction of the optical axis AX of the laser light reflected by the rotating mirror 50 and directed toward the transparent cover 60 changes, the laser light reflected by the transparent cover 60 can be reflected toward the focal point F of the parabola. The laser radar device 10 includes an outer peripheral surface 41c (reflection suppression portion) of the support base 41 that suppresses reflection of the irradiated laser light at a position where the laser light reflected by the inner surface 62 of the transparent cover 60 (inner reflected light) is irradiated. Therefore, by irradiating the outer peripheral surface 41c with the internally reflected light, reflection from the outer peripheral surface 41c can be suppressed, and the internally reflected light can be prevented from entering the light receiving unit 30.

[0052] The focus F of the parabola is set at a position farther away from the light receiving unit 30 (relative to the light receiving unit 30) in the direction of the optical axis AX than the rotating mirror 50. Therefore, the internally reflected light by the transparent cover 60 can be reflected toward the side away from the light receiving unit 30 in the direction of the optical axis AX while avoiding reflection toward the rotating mirror 50. Although a part of the internally reflected light irradiated to the outer peripheral surface 41c is diffusely reflected by the outer peripheral surface 41c, the amount of the diffusely reflected internally reflected light that enters the light receiving unit 30 decreases as the outer peripheral surface 41c is farther away from the light receiving unit 30. Therefore, the internally reflected light can be effectively prevented from entering the light receiving unit 30.

[0053] The outer peripheral surface 41c of the support base 41 is disposed at a position closer to the portion 62a of the transparent cover 60 than the light receiving unit 30 and the rotating mirror 50 in the horizontal direction (the direction in which the laser light travels from the rotating mirror 50 to the transparent cover 60). With this configuration, the internally reflected light does not pass in front of the light receiving unit 30 before reaching the outer peripheral surface 41c, and the internally reflected light can be prevented from entering the light receiving unit 30. In addition, since the outer peripheral surface 41c is disposed in front of the light receiving unit 30 and the rotating mirror 50 with respect to the transparent cover 60 in the horizontal direction, it is easy to arrange each component in the laser radar device 10 to pass the internally reflected light from the transparent cover 60 to the outer peripheral surface 41c. Therefore, the degree of freedom in arranging each component in the laser radar device 10 can be improved.

[0054] The focal point F is set at a position closer to the transparent cover 60 than the outer peripheral surface 41c in the direction of the laser light from the rotating mirror 50 to the transparent cover 60. With this configuration, the internally reflected light can be concentrated in front of the outer peripheral surface 41c, and the intensity of the laser light irradiated to the outer peripheral surface 41c can be prevented from increasing. Therefore, the internally reflected light can be further prevented from entering the light receiving unit 30.

[0055] The laser radar device 10 includes a support base 41 that supports a rotating mirror 50 and a motor 42, and the outer circumferential surface 41c (reflection suppression portion) is part of the support base 41 (integrated with the support base 41). With this configuration, the support base 41 that supports the rotating mirror 50 and the motor 42 can be used to dispose a reflection suppression portion that suppresses reflection of internally reflected light.

[0056] The laser radar device 10 includes a light-shielding partition member 29 that separates the light-projecting unit 20 and the light-receiving unit 30. With this configuration, the light-shielding partition member 29 can prevent the laser light projected by the light-projecting unit 20 from leaking into the light-receiving unit 30.

[0057] The partition member 29 protrudes 0 to 2 mm from the end 22a of the light projecting lens 22 (light projecting unit 20) in the direction in which the laser light is projected from the light projecting unit 20. With this configuration, the partition member 29 can effectively block the laser light leaking from the light projecting unit 20 in the direction of the light receiving unit 30, while preventing the reflected light reflected by the rotating mirror 50 and traveling toward the light receiving unit 30 from being blocked by the partition member 29.

[0058] The above embodiment can be modified as follows: The same parts as those in the above embodiment are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0059] The length by which partition member 29 protrudes from end 22a of light-projecting lens 22 (light-projecting unit 20) may be -1 to 3 mm in the direction in which laser light is projected from light-projecting unit 20. If there is no risk of laser light leaking from light-projecting unit 20 to light-receiving unit 30, partition member 29 can be omitted.

[0060] As shown in FIG. 5, in the formula of the parabola y=(x^2) / 4a that defines the shape of the inner surface 62 of the transparent cover 60, a may be set to be greater than the distance y1 from the origin O to the support base 41. That is, the focal point F may be set at a position farther from the transparent cover 60 than the outer peripheral surface 41c (reflection suppression unit) of the support base 41 in the horizontal direction (the direction in which the laser light travels from the rotating mirror 50 to the transparent cover 60). With this configuration, the inner reflected light can be irradiated onto the outer peripheral surface 41c of the support base 41 before the focal point F where the inner reflected light is concentrated, and the intensity of the laser light irradiated onto the outer peripheral surface 41c can be suppressed from increasing. Therefore, it is possible to suppress the inner reflected light from entering the light receiving unit 30. If the amount of the laser light reflected by the outer peripheral surface 41c that enters the light receiving unit 30 is sufficiently small, the focal point F of the parabola can also be set on the outer peripheral surface 41c.

[0061] In the formula of the parabola y=(x^2) / 4a, a can be increased and the distance y1 from the origin O to the support base 41 can be increased. This allows the outer peripheral surface 41c of the support base 41 to be located farther from the portion 62a of the transparent cover 60 than the light receiving unit 30 and the rotating mirror 50 in the horizontal direction.

[0062] The focus F(0,a) of the parabola y=(x^2) / 4a may be moved upward by moving the origin O of the xy plane upward (away from the light-projecting unit 20 and the light-receiving unit 30 in the direction of the optical axis AX). Then, the light reflected internally by the transparent cover 60 may be irradiated onto the lower surface (inner surface) of the lid 12, and the lower surface of the lid 12 may form a reflection suppression unit.

[0063] The laser radar device 10 may be arranged upside down relative to the arrangement shown in Figures 1, 4, and 5. In other words, the laser radar device 10 may be arranged so that the housing 11 is on the upper side and the lid 12 is on the lower side.

[0064] The rotating mirror 50 may be formed of a concave mirror. In this case, the laser light reflected by the rotating mirror 50 can be irradiated to the transparent cover 60 horizontally (approximately horizontally).

[0065] The light receiving lens 32 may include a short distance lens portion and a long distance lens portion. The short distance lens portion guides the laser light reflected by an object at a short distance from the laser radar device 10 to the photodiode 31. The long distance lens portion guides the laser light reflected by an object at a long distance from the laser radar device 10 to the photodiode 31.

[0066] The above-described embodiments and their modifications can be combined to the extent possible. [Explanation of symbols]

[0067] 10...laser radar device, 20...light-projecting section, 21...laser diode, 22...light-projecting lens, 29...partition member, 30...light-receiving section, 31...photodiode, 32...light-receiving lens, 40...rotating reflection mechanism, 41c...outer surface (reflection suppression section), 50...rotating mirror, 60...transparent cover, 61...transparent range, 62...inner surface.

Claims

1. a light projection unit that projects a laser beam; a light receiving unit that receives reflected light, which is the laser light reflected by an object; a rotating mirror that rotates around a predetermined rotation axis; a transmission cover that 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 laser radar device comprising: the light projecting unit and the light receiving unit are arranged side by side facing the rotating mirror, a projection 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 transparent cover and reflects the reflected light from the transparent cover toward the light-receiving unit, In each cross section including the rotation axis and passing through a range in the transparent cover through which the laser light passes, the shape of the inner surface of the transparent cover is formed into a parabola that reflects a part of the laser light traveling from the rotating mirror to the inner surface and reflected by the inner surface, toward a focal point set at a position farther away from the light receiving unit than the rotating mirror in the direction of the light projection axis, a reflection suppression section that suppresses reflection of the irradiated laser light at a position where the laser light reflected by the inner surface is irradiated.

2. 2 . The laser radar device according to claim 1 , wherein the reflection suppression unit is disposed at a position closer to the transparent cover than the light receiving unit and the rotating mirror in a direction in which the laser light travels from the rotating mirror to the transparent cover.

3. 3 . The laser radar device according to claim 1 , wherein the focal point is set at a position closer to the transparent cover than the reflection suppression portion is in a direction in which the laser light travels from the rotating mirror to the transparent cover.

4. A drive unit that rotates the rotating mirror; a support member supporting the rotating mirror and the drive unit, The laser radar device according to claim 1 , wherein the reflection suppressing portion is integrated with the support member.

5. 3. The laser radar device according to claim 1, further comprising a light-shielding partition member that separates the light-projecting section from the light-receiving section.

6. 6. The laser radar device according to claim 5, wherein the partition member protrudes 0 to 2 mm beyond an end of the light-projecting portion in a direction in which the laser light is projected from the light-projecting portion.

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