DISTANCE MEASURING DEVICE

Abstract

Distance measuring device (1) comprising: a pair of deflection mirrors (211); a mirror support (212) comprising a plate element having a shape conforming to the shape of the reflective surfaces of the pair of deflection mirrors, the pair of deflection mirrors being installed on both surfaces of the mirror support; a pair of partition plates (22) being installed to horizontally support the pair of deflection mirrors and the mirror support in a direction perpendicular to the reflective surfaces of the pair of deflection mirrors; a clamp (23) gripping and securing the pair of deflection mirrors, the mirror support and the pair of partition plates;and a motor (24) rotating the pair of deflecting mirrors, the mirror support, the pair of divider plates and the clamps, each of the pair of divider plates comprising a plate-like section (22a) extending along a plane perpendicular to the axis of rotation to divide a corresponding one of the reflecting surfaces into two regions, and an upright section (22b) extending along the corresponding reflecting surface from a position on the plate-like section where the plate-like section faces the corresponding reflecting surface, and the clamp gripping the pair of deflecting mirrors and the mirror support by means of the upright section in the direction perpendicular to the reflecting surfaces.

Description

[Cross-reference to related application][Technical Field]The present disclosure relates to a distance measurement device including deflection mirrors.[Prior Art]Existing distance measurement apparatuses are configured to emit transmission waves, detect reflected waves of the emitted transmission waves from an object, and thereby measure a distance to the object. In such distance measurement apparatuses, a rotation driven deflection mirror is used, and the transmission waves output from a transmitter are reflected by the deflection mirror and projected in a direction corresponding to a rotation angle of the deflection mirror, thereby scanning a predefined scanning region. The reflected waves from the object are reflected by the deflection mirror and detected by a receiver.JP 2018-500 603 A discloses a deflection mirror arrangement for a lidar device for deflecting and projecting light. This deflection mirror assembly includes a pair of deflection mirrors and a mirror carrier, the pair of deflection mirrors being installed on the mirror carrier on opposite sides of the mirror carrier. In this deflection mirror assembly, since transmission beams and reflected beams are deflected using the same deflection mirrors, a partition wall which is a partition plate for preventing short circuits between the transmitter side and the receiver side is provided on reflecting surfaces of the deflection mirrors. The partition wall has a straight edge portion which is an edge portion facing the reflecting surface of each deflection mirror and a fixing band formed at both ends of the straight edge portion, and is engaged with each deflection mirror by the straight edge portion and fixed to the mirror mount on the fixing band.Reference is also made to DE 10 2014 118 974 A1, CN 2 07 623 512 U and DE 10 2016 114 064 A1, which were determined as prior art.[Outline of Invention]In the technique described in JP 2018-500 603 A, when the partition plate is installed on the pair of deflection mirrors and the mirror support, it is necessary to engage the partition plate with each deflection mirror by means of the rectilinear edge portion and screw the fixing band to the mirror support. However, as a result of detailed studies carried out by the inventors of the present invention, a problem has been found that the partition plate cannot be easily assembled in such an installation method.An aspect of the present disclosure is to provide a technique for easily assembling the partition plate with the pair of deflection mirrors and the mirror support.An aspect of the present disclosure provides a distance measurement device including a pair of deflection mirrors, a mirror support, a pair of partition plates, a bracket, and a motor. The mirror support is a plate member having a shape in accordance with a shape of reflecting surfaces of the pair of deflection mirrors, the pair of deflection mirrors being installed on both surfaces of the mirror support. The pair of separation plates is installed to horizontally support the pair of deflection mirrors and the mirror support in a direction perpendicular to the reflecting surfaces of the pair of deflection mirrors. The bracket grips and secures the pair of deflecting mirrors, the mirror support and the pair of separating plates. The motor rotates the pair of deflection mirrors, the mirror support, the pair of separation plates, and the brackets. Each of the pair of separation plates includes a plate-like portion and an upright portion. The plate-like portion extends along a plane perpendicular to the rotation axis to divide a corresponding one of the reflecting surfaces into two regions. The upright portion extends along the corresponding reflecting surface from a position on the plate-like portion where the plate-like portion faces the corresponding reflecting surface. The bracket grips the pair of deflection mirrors and the mirror support by the upright portion in the direction perpendicular to the reflecting surfaces.This configuration facilitates assembling the pair of separation plates with the pair of deflection mirrors and the mirror support.[Brief Description of Drawings]FIG. 1 is a perspective view of a lidar device; FIG. 2 is an exploded perspective view of the lidar device; FIG. 3 is a perspective view of a photodetection module accommodated in a housing of the lidar device; FIG. 4 is an exploded perspective view of a mirror module, partition plates, and brackets in a sensing unit; FIG. 5A is a front perspective view of the partition plate; FIG. 5B is a side view of the partition plate; FIG. 5C is a rear perspective view of the partition plate; and FIG. 6 is a view of the mirror module, the partition plates, and the brackets in the scanning unit as viewed from a reflecting surface of the deflection mirror.[Description of Embodiments]Hereinafter, some exemplary embodiments of the disclosure will be described according to the drawings.[1. Configuration]A lidar device 1 illustrated in FIG. 1 is a distance measuring device that measures a distance to an object by emitting light and receiving its reflected light. The lidar device 1 is installed on a vehicle and is used to detect various objects located in front of the vehicle. LIDAR is an abbreviation for light detection and ranging.As illustrated in FIG. 1, the lidar device 1 includes a housing 100 and an optical window 200. The case 100 is a rectangular resin box having an opening in one of its six surfaces.Hereinafter, the direction along the length of the substantially rectangular opening is referred to as the X-axis direction, the direction along the width of the opening is referred to as the Y-axis direction, and the direction perpendicular to the X-axis direction and the Y-axis direction is referred to as the Z-axis direction. Right and left in the X-axis direction and up and down in the Y-axis direction are defined as viewed from the opening in the housing 100, with the lidar device 1 installed on the vehicle such that the X-Z plane is horizontal. In the Z-axis direction, forward is defined as a direction from the depth toward the opening in the housing 100, and rearward is defined as a direction toward the depth.As illustrated in FIG. 2, a photodetection module 2 is accommodated inside the housing 100. The photodetection module 2 includes a light projecting unit 10, a scanning unit 20, and a light receiving unit 30.[2. Sensing Unit]As illustrated in FIGS. 3 and 4, the sensing unit 20 includes a mirror module 21, a pair of partition plates 22, brackets 23, and a motor 24. The mirror module 21 stands on the motor 24. the mirror module 21, the pair of partition plates 22, and the brackets 23 are driven by the motor 24 to rotate about the rotation axis illustrated by the dot-dash line in FIG. 6.[3. Mirror Module, Partition Plates and Brackets]The mirror module 21 includes a pair of deflection mirrors 211 and a mirror support 212.The pair of deflection mirrors 211 are flat plate-like portions each having a reflecting surface that reflects light.The mirror support 212 includes a disc member 212 aand an installation member 212 b. The disk member 212 ais a circular and plate-like part whose center is fixed to the rotation axis of the motor 24. The installation member 212 bis a plate-like member on both surfaces of which the deflection mirrors 211 are installed, and is upright on the circular surface of the disk member 212 a.The pair of deflection mirrors 211 each has an integrated shape of two rectangles having different lengths. Specifically, each of the deflection mirrors 211 has an integrated shape of first and second rectangles arranged along their central axes extending in the width direction, the axes being aligned with each other. Hereinafter, in the pair of deflection mirrors 211, the rectangular portion corresponding to the first rectangle is referred to as a narrower portion, and the rectangular portion corresponding to the second rectangle is referred to as a wider portion.The shape of the surfaces of the installation member 212 bon which the pair of deflection mirrors 211 is installed corresponds to the shape of the pair of deflection mirrors 211.As illustrated in FIGS. 4 to 6, the pair of partition plates 22 is composed of two semicircular portions which together form a circular and plate-like member having a diameter equal to the length of the wider portion of each of the pair of deflection mirrors 211. The pair of separation plates ( 22) horizontally supports the pair of deflection mirrors 211 in a direction perpendicular to the reflecting surfaces of the pair of deflection mirrors 211, and thereby is fixed to the mirror module 21.Each partition plate 22 includes a plate-like portion 22 aand an upright portion 22 b. The plate-like portion 22 ais a semicircular plate-like portion and is positioned along a plane perpendicular to the rotation axis to divide the reflective surface of the deflection mirror 211 into two regions, that is, the narrower portion and the wider portion.The upright portion 22 bis a portion extending along the reflecting surface from a position on the plate-like portion 22 awhere the plate-like portion 22 afaces the reflecting surface of the deflection mirror 211. Hereinafter, the surface of the plate-like portion 22 awith the upright portion 22 bis referred to as a front side surface as illustrated in FIG. 5A, and the surface of the plate-like portion 22 awithout the upright portion 22 bis referred to as a back side surface as illustrated in FIG. 5C.As illustrated in FIG. 4, each bracket 23 is U-shaped and includes a base portion 23 aand a pair of gripping portions 23 bextending from the base portion 23 a. As illustrated in FIG. 6, the pair of brackets 23 with their respective pairs of gripping portions 23 bengages the pair of deflection mirrors 211 and the mirror support 212 via the upright portion 22 bat both ends of the narrower portion of each deflection mirror 211 in the direction perpendicular to the rotation axis. The pair of partition plates 22 is fixed to the mirror module 21.In a state where the pair of partition plates 22 is fixed to the mirror module 21, portions of each plate-like portion 22 aare positioned on side surfaces of the installation member 212 bthat form steps between the narrower and wider portions. Specifically, these side surfaces of the installation member 212 bare side surfaces of the wider portion of the installation member 212 bwhich are perpendicular to the rotation axis and are continuous with side surfaces of the narrower portion of the installation member 212 b. Both ends of a portion of the plate-like portion 22a where the upright portion 22b is formed are positioned on such side surfaces.Hereinafter, the upper part of the pair of deflection mirrors 211 relative to the pair of separation plates 22, that is, on the narrower portion side, is referred to as an emitted light deflector 20 a, and the lower part of the pair of deflection mirrors 211 relative to the pair of separation plates 22, that is, on the wider portion side, is referred to as a received light deflector 20 b.As illustrated in FIGS. 4 and 6, the installation member 212 bof the mirror bracket 212 includes a pair of mirror brackets 213, a pair of protrusions 214, and a pair of guides 215. The pair of mirror brackets 213 and the pair of guides 215 are formed on both side surfaces, across the rotation axis, of the narrower portion of the installation member 212 b. The pair of protrusions 214 are formed on the side surfaces of the installation member 212 bthat form the steps between the narrower portion and the wider portion.Each separator plate 22 includes a pair of bracket supports 216 and a pair of recesses 217. As illustrated in FIGS. 5A and 5B, the pair of bracket brackets 216 are formed on the front side surface of the plate-like portion 22 a. As illustrated in FIG. 5C, the pair of recesses 217 are formed on the back surface of the plate-like portion 22 a.The pair of bracket holders 216 are protrusions positioned farther from the rotation axis than the position of the base portion 23 aof the bracket 23 on the front side surface of the plate-like portion 22 aas illustrated in FIG. 6. Each pair of bracket holders 216 contacts a corresponding one of brackets 23 such that base 23 ais sandwiched between the pair of bracket holders 216 and mirror module 21, thereby restricting movement of brackets 23 in a direction perpendicular to the rotation axis on the reflecting surfaces.The pair of mirror brackets 213, as illustrated in FIG. 4, are protrusions protruding toward the pair of deflection mirrors 211 from both side surfaces, across the rotation axis, of the narrower portion of the installation member 212 b. As illustrated in FIG. 6, the pair of mirror holders 213 contact the pair of deflection mirrors 211 on both sides of the narrower portion of the installation member 212 bin the direction perpendicular to the rotation axis, thereby restricting movement of the pair of deflection mirrors 211 in the direction perpendicular to the rotation axis on the reflecting surfaces.The pair of projections 214, as illustrated in FIG. 4, are projections that project toward both of the pair of deflection mirrors 211 from the side surfaces of the installation member 212 bforming the steps between the narrower and wider portions of the installation member 212 b. The pair of projections 214 contact the deflection mirrors 211 at side surfaces forming the steps between the narrower and wider portions of the deflection mirrors 211, thereby restricting movement of the pair of deflection mirrors 211 in a direction from the wider portion to the narrower portion, that is, in the upward direction.The pair of recesses 217 are formed on the back surface of each plate-like portion 22a at positions facing the pair of projections 214 of the mirror support 212. The engagement of the pair of recesses 217 with the pair of protrusions 214 restricts the movement of the partition plate 22.The pair of guides 215 are protrusions protruding toward the pair of deflection mirrors 211 from both side surfaces, across the rotation axis, of the narrower portion of the installation member 212 b, and is positioned below the pair of mirror brackets 213. As illustrated in FIG. 6, the pair of guides 215 contact the pair of deflection mirrors 211 on both sides of the narrower portion of the installation member 212 bin the direction perpendicular to the rotation axis, thereby restricting the movement of the pair of deflection mirrors 211 in the direction perpendicular to the rotation axis on the reflecting surfaces. Further, the pair of guides 215 contact the respective brackets 23 to sandwich the brackets 23 with the plate-like portions 22 a, thereby restricting the movement of the brackets 23 in a direction parallel to the rotation axis.[4. Light Projection Unit]As illustrated in FIG. 3, the light projecting unit 10 includes a pair of light emitting modules 11, 12.The light emitting module 11 includes a light source 111 and an emission lens 112 both of which are disposed facing each other. A semiconductor laser is used as the light source 111. The emission lens 112 is a lens that narrows the beam width of light emitted from the light source 111. Similarly, the light emitting module 12 includes a light source 121 and an emission lens 122. Since the light emitting module 12 is similar to the light emitting module 11, its description is omitted.The emitted light folding mirror 15 is a mirror that changes the direction of propagation of light.The light emitting module 11 is arranged such that light output from the light emitting module 11 is directly incident on the emitted light deflector 20 a.The light emitting module 12 is arranged such that the propagation direction of light output from the light emitting module 12 is deflected substantially 90 degrees by the emitted light folding mirror 15, and the light is then incident on the emitted light deflector 20 a.Here, the light emitting module 11 is arranged to output light from left to right in the X-axis direction, and the light emitting module 12 is arranged to output light from back to front in the Z-axis direction. The emitted light folding mirror 15 is arranged so as not to block the path of the light from the light emitting module 11 to the emitted light deflector 20 a.[5. Light Receiving Unit]The light receiving unit 30 includes a light receiving element 31. the light receiving unit 30 may include a light receiving lens 32 and a received light folding mirror 33.The light receiving element 31 includes an APD array in which a plurality of APDs are arranged in a row. Each APD is an avalanche photodiode.The light receiving lens 32 is a lens that focuses the light arriving from the received light deflector 20 b.The received light folding mirror 33 is disposed on the left side of the light receiving lens 32 in the X-axis direction and configured to change the propagation direction of light. The light receiving element 31 is disposed below the received light folding mirror 33.The received light folding mirror 33 is arranged to bend the optical path downward substantially by 90 degrees such that light incident from the received light deflector 20 bvia the light receiving lens 32 reaches the light receiving element 31.The light receiving lens 32 is disposed between the received light deflector 20 band the received light folding mirror 33. The light receiving lens 32 narrows the light beam incident on the light receiving element 31 such that the beam diameter is approximately the element width of the APD.[6. Operation of Photodetection Module]The light output from the light emitting module 11 is incident on the emitted light deflector 20 a. The light output from the light emitting module 12 is incident on the emitted light deflector 20 aafter the propagation direction is bent by 90 degrees at the emitted light folding mirror 15. The light incident on the emitted light deflector 20 ais emitted through the optical window 200 in a direction corresponding to the rotation angle of the mirror module 21. A region irradiated with the light by the mirror module 21 corresponds to a scanning range. For example, assuming that the forward direction along the Z axis is 0 degrees, the sensing range may be a range of -60 degrees to +60 degrees spreading along the X axis direction.The light reflected from an object positioned in a specific direction according to a rotational position of the mirror module 21, that is, in a direction in which light is emitted from the emitted light deflector 20 apass through the optical window 200 and is reflected by the received light deflector 20 b. The reflected light is received by the light receiving element 31 via the light receiving lens 32 and the received light folding mirror 33.[7] Advantages]The present embodiment described above in detail can provide the following advantages.(7a) In the lidar device 1, the pair of partition plates 22 is fixed to the mirror module 21 by the pair of brackets 23 gripping the pair of deflection mirrors 211 and the mirror support 212 via the upright portions 22b. With this configuration, the separation plates 22 can be easily assembled to the pair of deflection mirrors 211 and the mirror support 212 by simply gripping the pair of deflection mirrors 211, the mirror support 212, and the pair of separation plates 22 with the brackets 23.(7 b) In the lidar device 1, the pair of partition plates 22 includes the bracket brackets 216. Each bracket holder 216 is a protrusion that extends from a position farther from the rotation axis than the position of the base 23 aof the bracket 23 on the plate-like portion 22 a, and restricts the movement of the bracket 23 in a direction perpendicular to the rotation axis on the reflecting surfaces. This prevents the brackets 23 from shifting in a direction perpendicular to the rotation axis on the reflecting surfaces during the mounting of the partition plates 22 to the mirror module 21 with the brackets 23, thereby improving the assembling accuracy.(7 c) In the lidar device 1, the mirror support 212 includes the pair of mirror brackets 213. The pair of mirror brackets 213 are protrusions protruding toward the pair of deflection mirrors 211 from both side surfaces, across the rotation axis, of the narrower portion of the installation member 212 b, and restricts the movement of the pair of deflection mirrors 211 in the direction perpendicular to the rotation axis on the reflecting surfaces. This prevents the pair of deflection mirrors 211 from being displaced in the direction perpendicular to the rotation axis on the reflecting surfaces, thereby improving assembly accuracy and simplifying assembly.(7d) In the lidar device 1, there are portions of each plate-like portion 22a of the partition plate 22 disposed on the side surfaces of the installing member 212b of the mirror bracket 212 that form steps between the narrower portion and the wider portion of the installing member 212. This configuration enables, during assembly of the partition plate 22 to the mirror module 21, the partition plate 22 to be positioned to divide the reflective surface of each deflection mirror 211 into two regions, that is, the narrower portion and the wider portion, thereby further facilitating assembly.(7e) In the lidar device 1, the mirror support 212 includes the pair of protrusions 214. The pair of projections 214 are projections that project toward both of the pair of deflection mirrors 211 from the side surfaces of the installation member 212 bthat form the steps between the narrower and wider portions of the installation member 212. The pair of protrusions 214 restrict the movement of the pair of deflection mirrors 211 in the direction from the wider portion to the narrower portion, that is, in the upward direction. This configuration prevents the pair of deflection mirrors 211 from shifting in the direction from the wider portion to the narrower portion, that is, in the upward direction, thereby improving assembly accuracy and further facilitating assembly.(7f) In the lidar device 1, the pair of partition plates 22 has the pair of recesses 217 formed on the back surface of each plate-like portion 22a at positions facing the pair of protrusions 214 of the mirror support 212. The engagement of the pair of recesses 217 with the pair of protrusions 214 restricts the movement of the partition plate 22, which configuration prevents the partition plate 22 from displacing in the direction perpendicular to the rotation axis during the mounting of the partition plate 22 to the mirror module 21, thereby improving assembly accuracy and simplifying assembly.(7 g) In the lidar device 1, the mirror support 212 includes the pair of guides 215. The pair of guides 215 are protrusions protruding toward the pair of deflection mirrors 211 from both side surfaces, across the rotation axis, of the narrower portion of the installation member 212 b, and is positioned below the pair of mirror brackets 213. The pair of guides 215 restrict the movement of the pair of deflection mirrors 211 in the direction perpendicular to the rotation axis on the reflecting surfaces. This configuration prevents the pair of deflection mirrors 211 from displacing in the direction perpendicular to the rotation axis on the reflecting surfaces, thereby improving assembly accuracy and simplifying assembly. Further, the pair of guides 215 contact the respective brackets 23 to sandwich the brackets 23 with the plate-like portions 22 a, thereby restricting the movement of the brackets 23 in a direction parallel to the rotation axis. This can prevent the brackets 23 from shifting in the direction parallel to the rotation axis during the mounting of the partition plate 22 to the mirror module 21 with the brackets 23, thereby improving the assembly accuracy.[8 Further Embodiments]While the specific embodiment of the present disclosure has been described above, the present disclosure is not limited to the above-described embodiment and may include various modifications.(8a) In the above embodiment, the pair of deflection mirrors 211, the mirror support 212, and the pair of separation plates 22 are gripped by the pair of brackets 23 at both ends of the narrower portion of each pair of deflection mirrors 211 in the direction perpendicular to the rotation axis, but the present disclosure is not limited to this embodiment. For example, the pair of deflection mirrors 211, the mirror support 212, and the pair of separation plates 22 may be gripped by only one bracket at one end. In this case, the bracket holders 216 may be formed on the plate-like portions 22 aon only the side where the bracket is provided.(8b) In the above embodiment, each plate-like portion 22a is a semicircular plate having the same diameter as the length of the wider portion of the pair of deflection mirrors 211, but the shape of the plate-like portion 22a is not limited thereto. For example, each plate-like portion 22 amay be a square plate or the like. Each plate-like portion 22 amay extend outward beyond the length of the wider portion of each of the pair of deflection mirrors 211.(8c) In the above embodiment, the installation member 212b of the mirror support 212 includes only a pair of mirror brackets 213, but the number of mirror brackets 213 is not limited thereto. For example, the installation member 212 bmay include two or more pairs of mirror brackets 213.(8d) In the above-described embodiment, the installation member 212b of the mirror bracket 212 includes a pair of protrusions 214 and a pair of recesses 217 for engaging the one pair of protrusions 214 formed in the partition plate 22, but the number of protrusions 214 and the number of recesses 217 are not limited thereto. For example, the installation member 212 bof the mirror bracket 212 may include only one protrusion 214, and a recess 217 for engaging with the protrusion 214 may be formed in the partition plate 22.(8e) In the above embodiment, the lidar device 1 is illustrated as a ranging device, but the type of the ranging device is not limited thereto. For example, the distance measurement device may be a millimeter wave radar or the like.(8f) The functions of a single component may be distributed among a plurality of components, or the functions of a plurality of components may be combined into a single component. At least a part of the configuration of the above embodiments can be removed. Further, at least a part of the configuration of any of the above embodiments may be added to or replaced with the configuration of another of the above embodiments.

Claims

A distance measurement device (1) comprising: a pair of deflection mirrors (211); a mirror support (212) which is a plate member having a shape in accordance with a shape of reflecting surfaces of the pair of deflection mirrors, the pair of deflection mirrors being installed on both surfaces of the mirror support; a pair of partition plates (22) installed to horizontally support the pair of deflection mirrors and the mirror support in a direction perpendicular to the reflecting surfaces of the pair of deflection mirrors; a bracket (23) which grips and secures the pair of deflection mirrors, the mirror support, and the pair of partition plates; and a motor (24) that rotates the pair of deflection mirrors, the mirror support, the pair of separation plates, and the brackets, wherein each of the pair of separation plates includes a plate-like portion (22a) that extends along a plane perpendicular to the rotation axis to divide a corresponding one of the reflecting surfaces into two regions, and an upright portion (22b) that extends along the corresponding reflecting surface from a position on the plate-like portion where the plate-like portion faces the corresponding reflecting surface, and the bracket grips the pair of deflection mirrors and the mirror support via the upright portion in the direction perpendicular to the reflecting surfaces.The distance measurement device according to claim 1, wherein the bracket is U-shaped and includes a base portion (23a) and a pair of gripping portions (23b) extending from the base portion, and the bracket having the gripping portions grips the pair of deflection mirrors and the mirror support via the upright portion at an end of the mirror support in a direction perpendicular to the rotation axis, and each of the pair of separation plates includes a bracket holder (216) that is a protrusion extending from a position farther from the rotation axis than a position of the base portion of the bracket on the plate-like portion, and restricts the movement of the bracket in the direction perpendicular to the rotation axis on the reflecting surfaces.The distance measurement device according to claim 1 or 2, wherein the mirror support includes a pair of mirror brackets (213) that are protrusions protruding toward the pair of deflection mirrors from both ends of the mirror support in the direction perpendicular to the rotation axis, and restricts the movement of the pair of deflection mirrors in the direction perpendicular to the rotation axis on the reflecting surfaces.The distance measurement device according to any one of claims 1 to 3, wherein each of the pair of deflection mirrors includes a narrower portion and a wider portion, a width of the reflective surface of the narrower portion along the direction perpendicular to the rotation axis is smaller than a width of the reflective surface of the wider portion along the direction perpendicular to the rotation axis, the narrower portion is formed on one of sides of the reflective surface in a direction parallel to the rotation axis, and the pair of separation plates are arranged to divide the reflective surfaces of the respective deflection mirrors into the narrower and wider portions, and a portion of the plate-like portion of each of the pair of separation plates is arranged on a side surface of the mirror support forming a step between narrower and wider portions of the mirror support corresponding to the narrower and wider portions of each deflection mirror, respectively.The distance measurement device according to claim 4, wherein the mirror support includes a protrusion (214) that protrudes toward each of the pair of deflection mirrors from the side surface forming the step between the narrower and wider portions of the mirror support, and restricts the movement of the pair of deflection mirrors in a direction from the wider portion to the narrower portion.The distance measuring apparatus according to claim 5, wherein each of the pair of partition plates has a recess (217) formed at a position on the plate-like portion facing the protrusion formed on the mirror support to engage with the protrusion.The distance measurement device according to any one of claims 4 to 6, wherein the mirror support includes a pair of guides (215) that are protrusions protruding toward the pair of deflection mirrors from both ends of a portion of the mirror support corresponding to the narrower portion in the direction perpendicular to the rotation axis and restrict the movement of the pair of deflection mirrors in the direction perpendicular to the rotation axis on the reflecting surfaces, and the bracket is sandwiched between one of the pair of guides and the plate-like portion and the movement of the bracket in the direction parallel to the rotation axis is restricted thereby.

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