Laser radar device

Abstract

This laser radar device is provided with: a light projection unit that projects laser light; a light reception unit that receives reflected light which is the laser light reflected by an object; a rotary mirror that rotates about a prescribed rotation axis; and a transmission cover that allows transmission of the laser light and the reflected light therethrough. The light projection unit and the light reception unit are arranged in parallel toward the rotary mirror. The projection axis of the laser light projected by the light projection unit is non-coaxial with the rotation axis. The rotary mirror reflects the laser light from the light projection unit toward the transmission cover and reflects the reflected light from the transmission cover toward the light reception unit. The shape of the inner surface of the transmission cover in a cross section of the laser radar device at each rotation position of the rotary mirror is a parabola, the cross section including the rotation axis and including a range of the transmission cover through which the laser light transmits. A portion of the laser light reflected by the inner surface of the transmission cover is reflected toward the focal point of the parabola. The focal point is set on the side opposite to the light reception unit across the rotary mirror. A reflection suppression member for suppressing reflection of the laser light is provided at a position where the laser light reflected by the inner surface of the transmission cover reaches.

Description

Laser radar device

[0001] The present disclosure relates to a laser radar device.

[0002] There is a laser radar device that uses laser light to detect the distance to an object, in which the direction of the light-projecting unit and the direction of the light-receiving unit form a right angle. For example, the laser radar device described in Patent Document 1 (JP2011-141261A) is provided with a fixed mirror having a reflective surface that is inclined with respect to the optical axis of the laser light from the light-projecting unit. A through-path through which the laser light passes is formed in the fixed mirror. The laser light from the light-projecting unit passes through the through-path and passes through the fixed mirror. The reflected light from the object is reflected by the reflective surface of the fixed mirror toward the light-receiving unit.

[0003] Furthermore, the laser radar device described in Patent Document 1 includes 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 outward and reflects the light reflected from the object toward the fixed mirror. This allows horizontal scanning using the laser light. The optical axis of the laser light passing from the light-emitting unit through the through-passage of the fixed mirror toward the rotating mirror (i.e., the light-projection axis), the rotation axis of the rotating mirror, and the optical axis of the reflected light from the rotating mirror toward the fixed mirror (i.e., the light-receiving axis) are all coaxial.

[0004] The laser light reflected by the rotating mirror toward the outside passes through the transparent cover and is projected toward the outside. The shape of the transparent cover is designed so that when part of the laser light traveling from the rotating mirror toward the transparent cover is reflected by the transparent cover, that laser light is not received by the light receiving unit.

[0005] However, the laser radar device described in Patent Document 1 requires a fixed mirror. Specifically, in the laser radar device, the direction in which the light-receiving unit faces and the light-receiving axis form a substantially right angle. Therefore, a fixed mirror is required to reflect the reflected light from the rotating mirror toward the light-receiving unit. On the other hand, in order to omit the fixed mirror, the positions of the light-projecting unit and the light-receiving unit may be changed. Even if the positions of the light-projecting unit and the light-receiving unit are changed, it is necessary that the laser light reflected by the transparent cover is not received by the light-receiving unit.

[0006] The present disclosure has been made to solve these problems, and its main purpose is to reduce the number of mirrors provided in a laser radar device and to make it more difficult for laser light reflected by the transparent cover to be received by the light receiving unit.

[0007] a laser radar device according to an embodiment of the present disclosure, the laser radar device comprising: a light-projecting unit that projects laser light; a light-receiving unit that receives reflected light, which is the laser light reflected by an object; a rotating mirror that rotates about a predetermined rotation axis; and a transparent cover that transmits the laser light and the reflected light, wherein the light-projecting unit and the light-receiving unit are arranged in parallel facing the rotating mirror, the 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, a cross section of the laser radar device at each rotation position of the rotating mirror, the cross section including the rotation axis and a range of the transparent cover through which the laser light transmits, has a parabolic inner shape, and a part of the laser light reflected by the inner surface of the transparent cover is reflected toward a focus of the parabola, the focus being set on the opposite side of the rotating mirror from the light-receiving unit, A reflection suppressing member for suppressing reflection of the laser light is provided at a position where the laser light reflected by the inner surface of the transparent cover reaches.

[0008] The laser radar device according to the present invention has a structure in which the reflection suppressing member is irradiated with light reflected internally from the laser radar device.

[0009] The laser radar device described in Patent Document 1 requires a fixed mirror. Alternatively, it is possible to omit the fixed mirror by arranging the light-projecting unit and the light-receiving unit in parallel facing the rotating mirror and changing the light-projection axis to be non-coaxial with the rotation axis of the rotating mirror. However, in this case, because the light-projection axis is non-coaxial with the rotation axis of the rotating mirror, the position at which the laser light from the light-projecting unit is reflected by the rotating mirror changes depending on the rotation position of the rotating mirror. As a result, the height of the laser light reflected by the rotating mirror and heading toward the transparent cover (i.e., the position at which the laser light passes through 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 is more difficult to design the shape of the transparent cover so that some of the laser light reflected by the transparent cover is not received by the light-receiving unit. A laser radar device according to an embodiment of the present disclosure reduces the number of mirrors included in the laser radar device and makes it difficult for the laser light reflected by the transparent cover to be received by the light-receiving unit.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A laser radar device according to an embodiment of the present disclosure will now be described with reference to the drawings. For example, the laser radar device detects an object that has entered a monitoring area.

[0011] 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. Fig. 1 illustrates a case where horizontal scanning is performed by laser light, with the direction of the optical axis AX and the direction of the central axis CL being vertical. However, the arrangement direction of the laser radar device 10 is not limited to this.

[0012] The housing 11 is formed in the shape of a hollow rectangular parallelepiped (i.e., box) with an open top (i.e., 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.

[0013] The light-projecting unit 20 includes a laser diode 21 and a projection lens 22. The laser diode 21 (i.e., a light-emitting element) is controlled by a control circuit (not shown), receives a pulse current from a drive circuit (not shown), and intermittently emits pulsed laser light upward in response to the pulse current. The laser light may be, for example, an infrared laser, a visible laser, or an ultraviolet laser. A projection lens 22 is provided on the optical axis AX of the laser light emitted from the laser diode 21. The projection lens 22 may be a collimating lens. The projection lens 22 converts the laser light from the laser diode 21 into parallel light. The optical axis AX (i.e., the projection axis) extends vertically (i.e., up and down). More specifically, the projection direction of the light-projecting unit 20 is directed upward, toward the rotating mirror 50 of the rotary reflection mechanism 40. The light-projecting unit 20 projects the laser light upward, toward the rotating mirror 50.

[0014] A cylindrical transmission cover 60 is attached to the top 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 opening at the top of the transmission cover 60 is closed by the lid 12.

[0015] The rotary reflection mechanism 40 includes a support base 41, a motor 42, a shaft 43, and a rotating mirror 50. The support base 41 (i.e., a support member) is cylindrically shaped and centered on a central axis CL. The support base 41 may be fixed to, for example, the housing 11. The motor 42 (i.e., a drive unit) rotates the shaft 43 to rotate the rotating mirror 50 connected to the shaft 43. The shaft 43 and the rotating mirror 50 rotate about the central axis CL (i.e., a predetermined rotation axis). The motor 42 may be, for example, a servo motor or a motor that rotates at a steady speed. When a motor that rotates at a steady speed is used, pulsed laser light may be output in synchronization with the timing at which the rotating mirror 50 faces the object detection direction. The motor 42 and the rotating mirror 50 are supported by the support base 41. The support base 41 may be fixed to the top of the lid 12 or the transparent cover 60.

[0016] The rotating mirror 50 is disposed so as to intersect with the optical axis AX and deflects (i.e., reflects) the laser light from the laser diode 21 (i.e., the light-emitting unit 20) toward the space outside the transparent cover 60. The rotating mirror 50 also deflects (i.e., reflects) the light reflected from an object in the space outside the transparent cover 60 (distinguished from internally reflected light, described later) toward the photodiode 31 (i.e., the light-receiving unit 30). That is, the rotating mirror 50 reflects the laser light from the light-emitting unit 20 toward the transparent cover 60, and also reflects the light reflected from the transparent cover 60 toward the light-receiving unit 30. The rotating mirror 50 may be, for example, a plane mirror. The rotating mirror 50 is inclined at an angle of, for example, 45° with respect to the vertical direction (i.e., the optical axis AX). The laser light irradiated onto the rotating mirror 50 is reflected horizontally by the rotating mirror 50.

[0017] The transmissive cover 60 transmits the laser light directed from the rotating mirror 50 to the outside and the reflected light directed from an object (i.e., the outside) to the rotating mirror 50. The detailed shape of the transmissive cover 60 will be described later.

[0018] The light-receiving unit 30 includes a photodiode 31 and a light-receiving lens 32. The light-receiving direction of the light-receiving unit 30 faces upward, toward the rotating mirror 50 of the rotary reflection mechanism 40. That is, the light-projecting direction of the light-projecting unit 20 and the light-receiving direction of the light-receiving unit 30 are the same. 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 (i.e., light-receiving axis) of the reflected light from the rotating mirror 50 toward the photodiode 31 (i.e., the light-receiving unit 30) coincides with the central axis CL. That is, the light-receiving axis is coaxial with the central axis CL. On the other hand, the optical axis AX (i.e., light-projecting axis) is parallel to the central axis CL (i.e., light-receiving axis). An offset is provided between the central axis CL and the optical axis AX. That is, the light-projecting axis is not coaxial with the central axis CL. The photodiode 31 (i.e., light receiving element) may be, for example, an avalanche photodiode. The photodiode 31 converts the received reflected light into an electrical signal. The reflected light is laser light projected from the light projecting unit 20 and reflected by an object.

[0019] When the light-projecting unit 20 and the light-receiving unit 30 are arranged in parallel 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. Therefore, the laser radar device 10 is provided with a light-blocking 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.

[0020] If the length of the light-shielding partition member 29 separating the light-projecting unit 20 and the light-receiving unit 30 is too short in the directions of the optical axis AX and the central axis CL (i.e., the direction in which the laser light is projected from the light-projecting unit 20), the effect of the partition member 29 in blocking the laser light leaking from the light-projecting unit 20 toward the light-receiving unit 30 will be reduced. On the other hand, if the length of the partition member 29 is too long in the directions of the optical axis AX and the central axis CL, there is a risk that the reflected light reflected by the rotating mirror 50 and traveling toward the light-receiving unit 30 will be blocked by the partition member 29. Therefore, the partition member 29 protrudes by 0 to 2 mm (millimeters) (for example, 1 mm) from the end 22 a of the light-projecting lens 22 (i.e., the light-projecting unit 20) on the rotating mirror 50 side in the directions of the optical axis AX and the central axis CL.

[0021] A distance calculation unit (not shown) calculates the distance from the light projecting unit 20 (i.e., the laser radar device 10) to the object for each light projection direction based on the 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. Specifically, the distance calculation unit calculates the distance from the laser radar device 10 to the object using the TOF (Time Of Flight) principle, which states that distance is proportional to the time from when the laser light is projected to when the reflected light is received.

[0022] 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 (i.e., the monitored area) through the transparent cover 60. If an object is present on the optical path of the laser light irradiated to the monitored area, the laser light is reflected by the object. The reflected light from 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.

[0023] 2 is a schematic diagram showing an example of a laser radar device 10A. This example was devised by the inventors of the present application and is not a publicly known technique. Note that the same parts as those in the laser radar device 10 are designated by the same reference numerals and the description thereof will be incorporated herein.

[0024] In the example shown in Figure 2, the optical axis AX is coaxial with the center axis CL. In a cross section of the laser radar device 10A at each rotational position of the rotating mirror 50 and 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 of the inner surface. The shape of the transparent cover 60A is symmetrical about the optical axis AX in a cross section including the optical axis AX at each rotational position, and is uniform in the circumferential direction centered on the optical axis AX. With the above configuration, the position at which the laser light from the light-projecting unit 20 is irradiated onto the rotating mirror 50 does not change depending on the rotational position of the rotating mirror 50.

[0025] For example, when the rotating mirror 50 is in the rotational position indicated by the solid line, the laser light from the light-projecting unit 20 is irradiated onto the center of the rotating mirror 50 in the height direction (i.e., the direction of the optical axis AX). The laser light reflected by the rotating mirror 50 reaches point P11 on the inner surface of the transparent cover 60A. A portion of the laser light that reaches point P11 is reflected at point P11 and reaches point P12 on the support base 41. The portion of the support base 41 corresponding to point P12 is a reflection-suppressing member that suppresses reflection of the irradiated laser light. For example, the portion corresponding to point P12 may be a low-reflectivity surface colored black or a diffuse-reflectivity surface with fine irregularities. This suppresses reflection of the laser light from point P12. This suppresses reception of the laser light reflected by the inner surface of the transparent cover 60A (hereinafter referred to as "internal reflection light") by the light-receiving unit 30.

[0026] Furthermore, even when the rotating mirror 50 is rotated 180 degrees from the rotation position indicated by the solid line to the rotation position indicated by the two-dot chain line, the laser light from the light projector 20 is irradiated onto the center of the rotating mirror 50 in the height direction. The laser light irradiated onto the rotating mirror 50 actually travels leftward in FIG. 2 . However, because the shape of the transparent cover 60A is symmetrical with respect to the optical axis AX, for convenience, when the rotating mirror 50 is in the rotation position indicated by the two-dot chain line, the direction of travel of the laser light is reversed from left to right, and the laser light is depicted as traveling rightward. At the rotation position indicated by the two-dot chain line, the laser light reflected by the rotating mirror 50 reaches a point corresponding to point P11 on the inner surface of the transparent cover 60A. A portion of the laser light that reaches the point corresponding to point P11 is reflected at the point corresponding to point P11 and reaches a point corresponding to point P12 on the support base 41. In this case, reflection of the laser light from the point corresponding to point P12 can also be suppressed. This makes it possible to prevent the light reflected internally by the transparent cover 60A from being received by the light receiving unit 30.

[0027] As described above, the position in the height direction of the laser light reflected by the rotating mirror 50 and directed toward the transmitting cover 60A is constant regardless of the rotation position of the rotating mirror 50.

[0028] 3 is a schematic diagram showing another example of a laser radar device 10B. This example was devised by the inventors of the present application and is not a publicly known technique. Note that the same components as those in the laser radar device 10 are designated by the same reference numerals and the description thereof will be incorporated herein.

[0029] In the example shown in FIG. 3 , the optical axis AX is not coaxial with the central axis CL. The optical axis AX is parallel to the central axis CL. An offset is provided between the central axis CL and the optical axis AX. In a cross section of the laser radar device 10A at each rotational position of the rotating mirror 50 and including the optical axis AX, the shape of the inner surface of the transparent cover 60B is a straight line inclined such that the distance from the optical axis AX increases toward the upper part of the inner surface. The shape of the transparent cover 60A is symmetrical about the optical axis AX in a cross section including the optical axis AX at each rotational position, and is uniform in the circumferential direction centered on the optical axis AX. In the above configuration, the position at which the laser light from the light-projecting unit 20 is irradiated on the rotating mirror 50 changes depending on the rotational position of the rotating mirror 50.

[0030] For example, when the rotating mirror 50 is in the rotational position indicated by the two-dot chain line, the laser light from the light-projecting unit 20 is irradiated to the right of the center of the rotating mirror 50 in the height direction (i.e., the direction of the optical axis AX). In FIG. 3 , as in FIG. 2 , when the rotating mirror 50 is in the rotational position indicated by the two-dot chain line, the laser light reflected by the rotating mirror 50 is conveniently shown traveling to the right. The reflected laser light reaches a point corresponding to point P21 on the inner surface of the transparent cover 60B. A portion of the laser light that reaches the point corresponding to point P21 is reflected at the point corresponding to point P21 and reaches a point corresponding to point P22 on the support base 41. The portion of the support base 41 corresponding to point P22 is a reflection-suppressing member, as in FIG. 2 . This suppresses reflection of the laser light from the point corresponding to point P22. This suppresses reception of the light reflected internally by the transparent cover 60B by the light-receiving unit 30.

[0031] Furthermore, when the rotating mirror 50 is rotated 90 degrees (or 270 degrees) 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 reaches point P23 on the inner surface of the transparent cover 60B, and a portion of the laser light that reaches point P23 is reflected at point P23 and reaches a position outside the support base 41. In this case, the light reflected internally by the transparent cover 60B does not reach the reflection suppressing member of the support base 41, and therefore there is a risk that the light reflected internally by the transparent cover 60B will be received by the light-receiving unit 30.

[0032] As described above, the position in the height direction of the laser light reflected by the rotating mirror 50 and directed toward the transparent cover 60B changes depending on the rotational position of the rotating mirror 50. Therefore, it is difficult to design the shape of the transparent cover 60B so that a portion of the laser light reflected by the transparent cover 60B is not received by the light receiving unit 30.

[0033] In contrast, in this embodiment, as shown in FIG. 4 , the cross section of the laser radar device 10 at each rotational position of the rotating mirror 50, which cross section includes the central axis CL and the range 61 through which the laser light of the transmitting cover 60 passes, has a parabolic shape of the inner surface 62 of the transmitting cover 60. The outer peripheral surface 41c of the support base 41 is a reflection suppressing member that suppresses reflection of the irradiated laser light. For example, the outer peripheral surface 41c may be a low-reflectivity surface colored black or the like, or a diffuse-reflectivity surface with fine irregularities. In other words, the reflection suppressing member is part of the support base 41 (i.e., the support member) and is integrated with the support base 41. The reflection suppressing member is disposed on the opposite side of the rotating mirror 50 from the light-projecting unit 20 and the light-receiving unit 30. The distance y2 from the central axis CL to the outer peripheral surface 41c of the support base 41 in the horizontal direction (i.e., the direction in which the laser light travels from the rotating mirror 50 to the transparent cover 60) 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 (i.e., the reflection suppressing member) is positioned closer to the transparent cover 60 (more specifically, the portion 62a of the transparent cover 60 closest to the central axis CL) in the horizontal direction than the light-receiving unit 30 and the rotating mirror 50. Note that if the reflection suppressing member is positioned farther from the transparent cover 60 than the light-receiving unit 30, there is a risk that the light-receiving unit 30 will receive the internally reflected light from the transparent cover 60 as it passes in front of the light-receiving unit 30. Furthermore, if the reflection suppressing member is positioned farther from the transparent cover 60, it is difficult to arrange the components in the laser radar device 10 to allow the internally reflected light to pass from the transparent cover 60 to the reflection suppressing member.

[0034] 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 considered as an xy plane, with the vertical direction being the x-axis direction and the horizontal direction being the y-axis direction. The origin O of the xy plane is set as any point in the vertical range from the lower end 41a (i.e., the first end) to the upper end 41b (i.e., the second end) of the support base 41. The parabola is expressed by the equation y = (x^2) / 4a, where x^2 represents the square of x. The focus of the parabola is focus F(0, a). The equation of the directrix is ​​y = -a, where a is set to a value smaller than the distance y1 from the origin O to the support base 41. That is, the focus F is set at a position where the distance from the transparent cover 60 in the horizontal direction (i.e., the direction in which the laser light travels from the rotating mirror 50 to the transparent cover 60) is shorter than the distance from the transparent cover 60 to the outer peripheral surface 41c of the support base 41 (i.e., the reflection suppressing member). As described above, the shape of the inner surface 62 of the transparent cover 60 is a parabola. A portion of the laser light reflected by the inner surface 62 is reflected toward the focal point of the parabola. The focal point is set at a position farther 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 of the light-projecting unit 20 and the light-receiving unit 30 with respect to the rotating mirror 50 in the direction of the optical axis AX (i.e., the light-projection axis). The outer peripheral surface 41c of the support base 41 (i.e., the reflection suppression member) is provided at a position where the laser light reflected by the inner surface 62 reaches.

[0035] In FIG. 4 , the relative relationship in which the position in the height direction of the laser light reflected by the rotating mirror 50 and heading toward the transparent cover 60 changes depending on the rotational position of the rotating mirror 50 is conveniently represented as follows: That is, in a cross section where the rotational position of the rotating mirror 50 is fixed, the position of the laser light irradiated from the light projector 20 to the rotating mirror 50 for each rotational position is illustrated by an arrow. Furthermore, as indicated by the arrows, all of the laser light reflected at each position on the rotating mirror 50 is conveniently shown as laser light traveling in the right direction. Each laser light reflected at each position on the rotating mirror 50 and heading horizontally toward the transparent cover 60 is reflected by the inner surface 62 of the transparent cover 60 toward a focal point F. The laser light beams, which are conveniently concentrated at the focal point F, disperse after passing through the focal point F and reach the outer peripheral surface 41 c of the support base 41. The reflection of each laser light beam that reaches the outer peripheral surface 41 c is suppressed by the outer peripheral surface 41 c, which serves as a reflection suppressing member.

[0036] The laser light projected at each rotational position has a width. In other words, the laser light projected at each rotational position is a beam of light. When the laser light is reflected by the transparent cover 60, multiple internally reflected lights with different reflection angles are generated. Therefore, if the focal point F at which the internally reflected lights from the transparent cover 60 are concentrated is set to the outer peripheral surface 41c, the internally reflected lights are concentrated on the outer peripheral surface 41c, increasing the intensity of the laser light that reaches the outer peripheral surface 41c. In this case, the intensity of the laser light that reaches the outer peripheral surface 41c is not sufficiently reduced, and the laser light may be reflected by the outer peripheral surface 41c. As a result, the laser light reflected by the outer peripheral surface 41c may be received by the light receiving unit 30.

[0037] The present embodiment described above in detail has the following advantages.

[0038] (1) According to this embodiment, 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 around 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.

[0039] Here, the light-projecting unit and the light-receiving unit are arranged in parallel facing the rotating mirror. Therefore, it is possible to omit a fixed mirror that reflects the light reflected 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. 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. As a result, the position in the direction of the projection axis of the laser light reflected by the rotating mirror and directed toward the transparent cover changes depending on the rotation position of the rotating mirror.

[0040] According to this embodiment, in a cross section of the laser radar device 10 at each rotational position of the rotating mirror 50, the cross section includes the central axis CL and the range 61 through which the laser light of the transparent cover 60 passes, the shape of the inner surface 62 of the transparent cover 60 is a parabola. A portion of the laser light reflected by the inner surface 62 is reflected toward the focus of the parabola. The focus is set on the opposite side of the rotating mirror 50 from the light receiving unit 30. In other words, the focus is set at a position farther from the light receiving unit 30 than the rotating mirror 50 in the direction of the optical axis AX. In this way, because the shape of the inner surface 62 of the transparent cover 60 is a parabola in the cross section at each rotational position, even if the position in the direction of the optical axis AX of the laser light reflected by the rotating mirror 50 and heading toward the transparent cover 60 changes, the laser light reflected by the transparent cover 60 can be reflected toward the focus F of the parabola. Furthermore, the laser radar device 10 includes an outer peripheral surface 41c (i.e., a reflection suppressing member) of the support base 41 that suppresses reflection of the laser light at a position where the laser light reflected by the inner surface 62 of the transparent cover 60 (i.e., the internally reflected light) reaches. In this way, by guiding the internally reflected light to the outer peripheral surface 41c, which is the reflection suppressing member, it is possible to suppress further reflection of the internally reflected light. As a result, it is possible to suppress the internally reflected light from being received by the light receiving unit 30.

[0041] (2) According to this embodiment, the focus F of the parabola is set on the opposite side of the rotating mirror 50 from the light receiving unit 30. In other words, the focus F is set at a position farther from the light receiving unit 30 than the rotating mirror 50 in the direction of the optical axis AX. Therefore, the internally reflected light by the transparent cover 60 can be reflected in a direction away from the light receiving unit 30 in the direction of the optical axis AX without being reflected toward the rotating mirror 50. A portion of the internally reflected light that reaches the outer peripheral surface 41c may be diffusely reflected by the outer peripheral surface 41c. However, the amount of diffusely reflected internally reflected light received by the light receiving unit 30 decreases as the outer peripheral surface 41c is farther from the light receiving unit 30. Therefore, the internally reflected light can be further suppressed from being received by the light receiving unit 30.

[0042] (3) If the reflection suppressing member onto which the internally reflected light is irradiated is located farther from the transparent cover than the light receiving unit, the internally reflected light may be received by the light receiving unit. Also, if the reflection suppressing member is located far from the transparent cover, it is difficult to arrange the components in the laser radar device to allow the internally reflected light to pass from the transparent cover to the reflection suppressing member.

[0043] According to this embodiment, the outer peripheral surface 41c of the support base 41 is positioned 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 (i.e., the direction in which the laser light travels from the rotating mirror 50 to the transparent cover 60). This prevents the internally reflected light that reaches the outer peripheral surface 41c from passing in front of the light receiving unit 30. This prevents the internally reflected light from being received by the light receiving unit 30. Furthermore, the outer peripheral surface 41c is positioned closer to the transparent cover 60 than the light receiving unit 30 and the rotating mirror 50 in the horizontal direction. This facilitates the arrangement of components within the laser radar device 10 to allow the internally reflected light to pass from the transparent cover 60 to the outer peripheral surface 41c. This improves the degree of freedom in the arrangement of components within the laser radar device 10.

[0044] (4) If the focal point where the multiple internally reflected beams at each rotation position converge is set on the outer peripheral surface, the internally reflected beams converge on the outer peripheral surface, increasing the intensity of the laser beam that reaches the outer peripheral surface. In this case, the intensity of the laser beam that reaches the outer peripheral surface is not sufficiently reduced, and the laser beam may be reflected by the outer peripheral surface. As a result, the laser beam reflected by the outer peripheral surface may be received by the light receiving unit.

[0045] According to this embodiment, the focal point F is set at a position where, in the direction of the laser light from the rotating mirror 50 toward the transparent cover 60, the distance from the transparent cover 60 is shorter than the distance from the transparent cover 60 to the outer peripheral surface 41c. This allows multiple internally reflected light beams at each rotation position to be concentrated just before the outer peripheral surface 41c. As a result, the intensity of the laser light beam irradiated onto the outer peripheral surface 41c can be reduced. This further reduces the internally reflected light beam from being received by the light receiving unit 30.

[0046] (5) Generally, a drive unit for rotating the rotating mirror is provided at a position opposite the light projecting unit with respect to the rotating mirror. The rotating mirror and the drive unit are supported by a support member at a position opposite the light projecting unit with respect to the rotating mirror.

[0047] According to this embodiment, the laser radar device 10 includes a support base 41 that supports the rotating mirror 50 and the motor 42, and the outer circumferential surface 41c (i.e., the reflection suppressing member) is part of the support base 41. In other words, the outer circumferential surface 41c is integrated with the support base 41. This makes it possible to use the support base 41 that supports the rotating mirror 50 and the motor 42 to arrange a reflection suppressing member that suppresses reflection of internally reflected light. In other words, the reflection suppressing member can be arranged without adding any additional components.

[0048] (6) When the light-emitting unit and the light-receiving unit are arranged in parallel facing the rotating mirror, there is a risk that the laser light emitted by the light-emitting unit may leak into the light-receiving unit.

[0049] According to this embodiment, the laser radar device 10 includes a light-blocking partition member 29 that separates the light-projecting unit 20 from the light-receiving unit 30. This allows the light-blocking partition member 29 to prevent the laser light projected by the light-projecting unit 20 from leaking into the light-receiving unit 30.

[0050] (7) 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 partition member will be less effective in blocking the laser light leaking from the light-projecting unit toward the light-receiving unit. 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, the partition member may block the light reflected by the rotating mirror toward the light-receiving unit.

[0051] According to this embodiment, the partition member 29 protrudes 0 to 2 mm beyond the end 22 a of the light-projecting lens 22 (i.e., the light-projecting unit 20) in the direction in which the laser light is projected from the light-projecting unit 20. This prevents the partition member 29 from blocking the light reflected by the rotating mirror 50 and traveling toward the light-receiving unit 30, and allows the partition member 29 to block the laser light leaking from the light-projecting unit 20 toward the light-receiving unit 30.

[0052] Next, a modified example of the above embodiment will be described. The same parts as those in the above embodiment will be denoted by the same reference numerals and the description thereof will be incorporated.

[0053] (A) The length by which the partition member 29 protrudes beyond the end 22a of the light-projecting lens 22 (i.e., the light-projecting unit 20) may be −1 to 3 mm in the direction in which the laser light is projected from the light-projecting unit 20. Furthermore, if there is no risk of the laser light leaking from the light-projecting unit 20 to the light-receiving unit 30, the partition member 29 may be omitted.

[0054] (B) As shown in FIG. 5 , in the parabola y = (x^2) / 4a, which represents the shape of the inner surface 62 of the transparent cover 60, a may be set to a value 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 where the distance from the transparent cover 60 in the horizontal direction (i.e., the direction of the laser light from the rotating mirror 50 to the transparent cover 60) is greater than the distance from the transparent cover 60 to the outer peripheral surface 41c of the support base 41 (i.e., the reflection suppressing member). This allows the position at which multiple internally reflected beams at each rotation position reach the outer peripheral surface 41c of the support base 41 to be closer to the focal point F where the internally reflected beams concentrate. As a result, the intensity of the laser beams reaching the outer peripheral surface 41c can be reduced. Therefore, the reception of the internally reflected beam by the light receiving unit 30 can be suppressed. Note that even if the laser beams reaching the outer peripheral surface 41c are received by the light receiving unit 30, the focal point F of the parabola may be set to the outer peripheral surface 41c as long as the amount of received light is sufficiently small. In this case, the arrival position of the internally reflected light at each rotation position is located on a straight line on the outer periphery of the outer periphery 41c. On the other hand, when the focal point F is not set on the outer periphery 41c, the arrival position of the laser light is located on a sine curve (or cosine curve) on the outer periphery of the outer periphery 41c. Therefore, when the focal point F is set on the outer periphery 41c, the width of the outer periphery 41c can be reduced compared to when the focal point F is not set on the outer periphery 41c.

[0055] (C) In the formula of the parabola y = (x^2) / 4a, a may be increased, and the distance y1 from the origin O to the support base 41 may be increased. This allows the outer peripheral surface 41c of the support base 41 to be positioned farther from the portion 62a of the transparent cover 60 in the horizontal direction than the light receiving unit 30 and the rotating mirror 50.

[0056] (D) By moving the origin O of the xy plane upward (i.e., 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 may move upward. Furthermore, the light reflected internally by the transparent cover 60 may be guided to the underside of the lid 12 (i.e., the inner surface of the lid 12), and a reflection suppressing member may be provided on the underside of the lid 12.

[0057] (E) 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.

[0058] (F) The rotating mirror 50 may be a concave mirror. In this case, the laser light reflected by the rotating mirror 50 travels toward the transmitting cover 60 in a substantially horizontal direction.

[0059] (G) 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 relatively close to the laser radar device 10 to the photodiode 31. The long-distance lens portion guides the laser light reflected by an object relatively far from the laser radar device 10 to the photodiode 31.

[0060] The above-described embodiments and their modifications may be combined to the extent possible.

Claims

1. A laser radar device comprising: a light-projecting unit that projects laser light; 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; and a transparent cover that transmits the laser light and the reflected light, wherein the light-projecting unit and the light-receiving unit are arranged in parallel toward the rotating mirror, the 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, a cross section of the laser radar device at each rotation position of the rotating mirror, the cross section including the rotation axis and the range of the transparent cover through which the laser light transmits is a parabola, and a portion of the laser light reflected by the inner surface of the transparent cover is reflected toward the focus of the parabola, and the focus is set on the opposite side of the rotating mirror to the light-receiving unit, a reflection suppressing member that suppresses reflection of the laser light, the reflection suppressing member being provided at a position where the laser light reflected by an inner surface of the transparent cover reaches.

2. The laser radar device according to claim 1, wherein the reflection suppression member is arranged 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.

3. A laser radar device as described in claim 1 or 2, wherein the focal point is set at a position that is shorter from the transparent cover in the direction in which the laser light travels from the rotating mirror to the transparent cover than the distance from the transparent cover to the reflection suppression member.

4. A laser radar device as described in claim 1 or 2, further comprising: a drive unit that rotates the rotating mirror; and a support member that supports the rotating mirror and the drive unit, wherein the reflection suppression member is integrated with the support member.

5. The laser radar device according to claim 1 or 2, further comprising a light-blocking partition member separating the light-projecting section and the light-receiving section.

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

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