DISTANCE MEASURING DEVICE

Abstract

Distance measuring device (1) comprising: a mirror module (21) which rotates when driven by a motor (24), the mirror module comprising: two deflecting mirrors (211, 212) each comprising a small-width section in which the width of a reflective surface along a direction orthogonal to an axis of rotation is smaller than that of another section of the reflective surface; a mirror support element (213) which is configured in a disk shape having on both surfaces a shape corresponding to a shape of the reflective surface, the two deflecting mirrors being arranged on the respective two surfaces; and a clamp (214, 215) which engages the two deflecting mirrors and the mirror support element at at least one end section of two end sections of a section in the mirror support section corresponding to the small-width section in a direction orthogonal to the axis of rotation.

Description

Technical FieldThe present invention relates to a distance measuring apparatus having a deflection mirror.Prior ArtA distance measurement device that detects a distance to an object by radiating transmission waves and detecting reflection waves, which are reflected waves of the transmission waves from the object, is known. According to the distance measuring apparatus, a rotatably driven deflection mirror is used for deflecting the transmission waves in scanning, the output transmission waves are reflected at the deflection mirror and emitted in a direction depending on a rotational speed of the deflection mirror, thereby scanning a predetermined scanning range.JP 2018-500 603 A discloses a deflecting mirror device in a LIDAR device that deflects light for scanning. The deflecting mirror device includes a pair (two) of deflecting mirrors and a mirror supporting member, the pair of deflecting mirrors being disposed on the mirror supporting member on opposite sides thereof.DE 10 2014 118 974 A1 discloses an optical separating means for a deflection mirror arrangement of a laser scanner. The optical separating means comprises a substantially rigid separating wall for separating a receiving mirror region of a deflecting mirror from a transmitting mirror region, wherein the separating wall has a rectilinear edge section. The separating means has fastening webs arranged on both sides of the rectilinear edge section of the separating wall for fastening to a mirror carrier. Along the rectilinear edge portion of the partition wall, an elastically deformable sealing element is arranged.DE 10 2016 114 064 A1 discloses a scanning mirror for a laser scanning system having a carrier structure and a mirror plate connected thereto, which has a mirror surface on the side facing away from the carrier structure. The support structure is formed of a porous material having a structure with cavities. An outer surface of the support structure is sealed. A scanning mirror unit for a laser scanning system has a scanning mirror for deflecting a laser beam and a mirror holder connected thereto, which mirror holder has a holder axis about which the mirror holder is rotatable together with the scanning mirror.CN 2 07 623 512 U discloses a multi-line laser radar scanning rotary mirror system comprising: a double-sided reflector for changing the direction of an optical path, reflecting and receiving laser pulses at different angles; a motor driving the double-sided reflector to rotate it and controlling the laser radar to horizontally scan the field of view; a rotary mirror connector used for connecting the motor and the double-sided reflector, wherein a motor rotation shaft of the motor coincides with the rotation shaft of the rotary mirror connector, and the rotation shaft of the rotary mirror connector forms an angle with the extending surface of the double-sided reflector or the mirror surface of the double-sided reflector.SUMMARY OF THE INVENTIONAs a result of studies by the inventor of the present application, a problem has been found in a distance measurement apparatus equipped with a mirror module including a pair of deflection mirrors and a mirror support member. The problem is that it is necessary to easily assemble a deflection mirror and a mirror support member, and the size of the entire mirror module needs to be smaller.An object of the present invention is to provide a technique for easily assembling a deflection mirror and the mirror supporting member and reducing the size of the entire mirror module. The object is achieved by a distance measuring device having the features of claim 1. The dependent claims are directed to advantageous further developments of the invention.One aspect of the present invention relates to a distance measurement device including a mirror module that rotates when driven by a motor. The mirror module includes a pair (two) of deflection mirrors, a mirror support member, and a clamp. The pair of deflection mirrors includes a small width portion in which a width of a reflection surface along a direction orthogonal to a rotation axis is smaller than that of another portion of the reflection surface. The mirror supporting member is formed in a disc shape, both surfaces of which have a shape corresponding to a shape of the reflecting surface, and the pair of deflecting mirrors are disposed on the both surfaces. The clamp grips the pair of deflecting mirrors and the mirror support member at least one end portion of two end portions of a portion in the mirror support portion corresponding to the narrow width portion in a direction orthogonal to the rotation axis.According to such a configuration, the pair of deflection mirrors and the mirror support member can be assembled simply by sandwiching and supporting the clamp therebetween. When the clamp is disposed, there may be a problem that the outer dimension of the entire mirror module becomes larger because the clamp protrudes from the deflecting mirror. However, since the clip is disposed in the small width portion, an increase in the outer dimension of the entire mirror module can be prevented.Thus, the deflecting mirror and the mirror supporting member can be easily assembled, and the size of the entire mirror module can be reduced.Brief Description of the DrawingsFIG. 1 is a perspective view showing an appearance of a LIDAR device. FIG. 2 is an exploded perspective view showing the LIDAR device. FIG. 3 is a perspective view showing a configuration of a light sensing module accommodated in the LIDAR device. FIG. 4 is an exploded view showing a mirror module and a partition plate in a sensing unit. FIG. 5 is a diagram showing the mirror module as viewed from a reflecting surface on a deflection mirror.DESCRIPTION OF THE EMBODIMENTSHereinafter, exemplary embodiments of the present invention will be described with reference to the drawings.1. ConfigurationThe LIDAR device 1 shown in FIG. 1 emits light and receives the reflected light thereof, thereby measuring a distance to an object according to a function as a distance measurement device. The LIDAR device 1 is mounted on a vehicle and is used to detect various objects present in front of the vehicle. LIDAR is an abbreviation for light detection and ranging (light detection and ranging).As shown in FIG. 1, the LIDAR device 1 includes a housing 100 and an optical window 200. The housing 100 is made of a box body made of resin and is formed in a rectangular parallelepiped shape with one surface open.Hereinafter, a direction along the longitudinal direction of the opening portion having a substantially rectangular shape in the housing 100 is defined as an X-axis direction, a direction along a short direction of the opening portion is defined as a Y-direction, and a direction orthogonal to an XY plane is defined as a Z-axis direction. Note that left and right in the X-axis direction and upper and lower in the Y-axis direction are defined as viewed from an opening portion of the housing in a state where the LIDAR device 1 is mounted on the vehicle. In addition, front and rear in the Z-axis direction are defined such that the front side is the side of the opening portion of the housing 100 and the rear side is the side of the depth of the housing 100.As shown in FIG. 2, the light detecting module 2 is accommodated inside the housing 100. The light detection module 2 includes a light projecting unit 10, a sensing unit 20, and a light receiving unit 30.Next, a configuration of the light detection module 2, specifically, a configuration of a mirror module 21, will be described in more detail.2. The scanning unit is a scanning unitAs shown in FIGS. 3 and 4, the sensing unit 20 includes a mirror module 21, a pair (two) of partition plates 22 and 23, and a motor 24. The mirror module 21 is disposed standing on the motor 24, and the mirror module 21 and the pair of partition plates 22 and 23 fixed to the mirror module 21 rotate about a rotation axis indicated by a dot-and-dash line in FIG. 5 when driven by the motor 24.3. Mirror Module and Separator PlateThe mirror module 21 includes a pair (two) of deflection mirrors 211 and 212, a mirror support member 213, and a pair (two) of clamps 214 and 215.The two deflection mirrors 211 and 212 each serve as a flat plate-shaped member having a reflecting surface that reflects light.The mirror support member 213 includes a disc portion 213 aand an installation member 213 b. The disk portion 213 ais a member having a circular plate shape, and the center of the circle is fixed to a rotation shaft of the motor 24. The installation member 213 bis a plate-shaped member to which the two deflection mirrors 211 and 212 are installed on both sides thereof, the installation member 213 bprotruding upward from a circular surface of the disk member 213 a.The two deflection mirrors 211 and 212 are each formed to have a shape integrating two rectangles having different widths in the longitudinal direction. In particular, the shape is formed such that a first rectangle and a second rectangle whose longitudinal width is greater than that of the first rectangle are arranged along a common central axis, wherein the central axes are aligned with one another along the short directions of the respective rectangles, whereby both rectangles are integrated or form a unit. Hereinafter, in the two deflecting mirrors 211 and 212, a portion corresponding to the first rectangle is referred to as a narrow width portion, and a portion corresponding to the second rectangle is referred to as a wide width portion.The shape of the installation surface for the two deflection mirrors 211 and 212 in the installation member 213 bcorresponds to the shape of the pair of deflection mirrors 211 and 212. The installation member 213 bhas a pair (two) of guides 216 and 217 on both side surfaces, respectively, with respect to the rotation axis in a portion corresponding to the narrow width portion.The two guides 216 and 217 are protrusions that protrude toward the deflection mirrors 211 and 212 from both side surfaces with respect to the rotation axis in a portion corresponding to the narrow width portion of the installation member 213 b. The two guides 216 and 217 contact the two deflection mirrors 211 and 212 on both sides of the narrow width portion in a direction orthogonal to the rotation axis and regulate a movement of the two deflection mirrors on the reflecting surface in a direction orthogonal to the rotation axis.As shown in FIG. 4, the clamp 214 is formed in a U-shape including a base portion 214 aand a pair of gripping members 214 band 214 cextending from the base portion 214 a. The clamp 214 is configured such that the two gripping portions 214 band 214 cengage the pair of deflecting mirrors 211 and 212 and the installation member 213 bat the end portions of the narrow width portions in a direction orthogonal to the rotation axis of the pair of deflecting mirrors 211 and 212. The clamp 215 is formed in the same shape as the clamp 214, and includes a base portion 215a and two gripping members 215b and 215c extending from the base portion 215a. The clamp 215 is disposed at an end portion of both end portions of the narrow width portions of the two deflection mirrors 211 and 212 opposite to each other in a direction orthogonal to the rotation axis of the clamp 214.FIG. 5 shows a state in which the two clamps 214 and 215 grip the two deflecting mirrors 211 and 212 and the installing member 213 b. The two clamps 214 and 215 and the guides 216 and 217 are disposed more inward in the longitudinal direction than the width of the wide width portion of the two deflection mirrors 211 and 212.The two partition plates 22 and 23 are formed such that a plate member formed in a circular plate shape whose diameter is the same as the width in the longitudinal direction of the large width portion in the two deflection mirrors 211 and 212 is divided into two semicircular members. The two partition plates 22 and 23 are fixed to the mirror module 21 in a state in which the narrow width portions of the two deflection mirrors 211 and 212 are disposed between the two partition plates 22 and 23, and the two partition plates 22 and 23 contact a step portion between the wide width portion and the narrow width portion of the two deflection mirrors 211 and 212.As shown in FIGS. 3 and 5, hereinafter, a portion in the two deflecting mirrors 211 and 212 disposed on an upper side of the two separating plates 22 and 23, that is, a portion on the small width portion side, is referred to as a projection deflecting portion 20 a. In addition, a portion in the two deflection mirrors 211 and 212 located on a lower side of the two partition plates 22 and 23, that is, a portion on the side of the large width portion, is referred to as a light receiving deflection portion 20 b.4. Light Projection UnitAs shown in FIG. 3, the light projecting unit 10 includes a pair (two) of light emitting modules 11 and 12. The light projecting unit 10 may include a light projecting reflecting mirror 15.The light emitting module 11 includes a light source 111 and a light emitting lens 112 disposed facing each other. A semiconductor laser device is used for the light source 11. The light emitting lens 112 reduces a width of the beam emitted from the light source 111. Similarly, the light emitting module 12 includes a light source 121 and a light emitting lens 122. Since the light emitting module 12 is the same as the light emitting module 11, the explanation thereof is omitted.The light projection reflecting mirror 15 is configured to change the direction of propagation of light.The light emitting module 11 is arranged such that the light output from the light emitting module 11 directly impinges on the projection deflection portion 20 a.The light emitting module 12 is arranged such that the light projection reflecting mirror 15 changes the direction of propagation of the light output from the light emitting module 12 by approximately 90 degrees so as to be incident on the projection deflecting portion 20 a.Here, the light emitting module 11 is arranged to output light from the left side in the X-axis direction to the right, and the light emitting module 12 is arranged to output the light from the back side in the Z-axis direction to the front side. In addition, the light projection reflecting mirror 15 is disposed such that the path of the light from the light emitting module 11 propagates toward the projection deflecting portion 20 aand is not disturbed.5. Light Receiving UnitThe light receiving unit 30 includes a light receiving element 31. The light receiving unit 30 may include a light receiving lens 32 and a light receiving reflecting mirror 33.The light receiving element 31 includes an APD array in which a plurality of APDs are arranged in a row. APD is an abbreviation for avalanche photodiode.The light receiving lens 32 focuses the light coming from the light receiving deflection portion 20 b.The light receiving reflecting mirror 33 is disposed on the left side of the light receiving lens 32 in the X-axis direction, and changes the direction of propagation of the light. The light receiving element 31 is disposed in a lower portion of the light receiving reflecting mirror 33.The light-receiving reflecting mirror 33 is arranged such that the path of the light is deflected downward by approximately 90 degrees, whereby the light from the light-receiving deflecting portion 20b is incident on the light-receiving element 31 via the light-receiving lens 32.The light receiving lens 32 is disposed between the light receiving deflection unit 20 band the light receiving reflecting mirror 33. The light receiving lens 32 focuses the diameter of the light beam incident on the light receiving element 31 to be approximately the same as the element width of an APD.6. Operation of Light Receiving ModuleThe light emitted from the light emitting module 11 impinges on the projection deflection section 20 a. In addition, the direction of propagation of the light emitted from the light emitting module 12 is deflected at the light projection reflecting mirror 15 by approximately 90 degrees, and then impinges on the projection deflecting portion 20a. The light incident on the projection deflection portion 20 ais emitted through the optical window 200 in a direction depending on the rotation angle of the mirror module 21. A region where light is radiated via the mirror module 21 is referred to as a scanning region. A range spreading by about ±60 degrees along the X-axis direction, the front direction along the Z-axis being defined as 0 degrees, may be the sensing range.The light reflected from an object disposed in a predetermined direction depending on the rotational position of the mirror module 21, that is, the light reflected in the emission direction of the light from the projection deflection section 20 apass through the optical window 200 and is reflected at the light receiving deflection section 20 b. Then, the reflected light is received by the light receiving element 31 via the light receiving lens 32 and the light receiving reflecting mirror 33.7. Effects and AdvantagesAccording to the above-described embodiments, the following effects and advantages can be obtained.(7a) In the LIDAR device 1, the two deflection mirrors 211 and 212 and the mirror support member 213 are gripped by the clamps 214 and 215 at both ends of the narrow width portions in a direction orthogonal to the rotation axis of the two deflection mirrors 211 and 212. According to this configuration, the two deflecting mirrors 211 and 212 and the mirror supporting member 213 can be easily assembled by placing and supporting the clamps 214 and 215 therearound. In addition, according to the present embodiment, the clamps 214 and 215 are disposed at the small width portion, thereby preventing the clamps from protruding from the deflection mirror. Thus, an increase in the outer dimension of the entire mirror module 21 can be prevented, and the entire size of the mirror module 21 can be reduced.(7b) In the LIDAR device 1, the installation member 213b has two guides 216 and 217 protruding toward the deflection mirrors 211 and 212 from both side surfaces with respect to the rotation axis in a portion corresponding to the narrow width portion. The two guides 216 and 217 regulate a movement of the two deflection mirrors on the reflecting surface in a direction orthogonal to the rotation axis. According to this configuration, since the two deflection mirrors 211 and 212 can be prevented from being displaced on the reflection surface in a direction orthogonal to the rotation axis, the two deflection mirrors 211 and 212 and the mirror support member 213 can be easily assembled. Since the two guides 216 and 217 are disposed in a portion corresponding to the narrow width portion of the installation member 213 b, whereby an increase in the outer dimension of the entire mirror module 21 can be prevented, the size of the entire mirror module 21 can be reduced.(7c) In the LIDAR device 1, the narrow width portion of the deflection mirrors 211 and 212 is formed on one side out of the two sides of the reflection surface with respect to a direction parallel to the rotation axis. The two deflection mirrors 211 and 212 have a shape in which a first rectangle and a second rectangle whose longitudinal width is larger than that of the first rectangle are arranged along a common central axis, the central axes being aligned with each other along the short directions of the respective rectangles, thereby integrating both rectangles. A portion corresponding to the first rectangle is the narrow width portion. Thus, the shape of the deflection mirrors can be simplified. Therefore, the deflection mirrors 211 and 212 and the mirror supporting member 213 can be easily manufactured, and they can be easily assembled.The beam of light in the LIDAR device 1 output from the light projecting unit 10 and incident on the projection deflecting unit 20 ais punctiform and is reflected and emitted at approximately the central portion of the projection deflecting unit 20 a. In contrast, the beam of the light reflected from the object spreads and is reflected at the entire light receiving deflection unit 20 b, and the diameter of the beam is focused by the light receiving lens 32 to approximately the width of the light receiving element 31 upon incidence thereon. Even when the width of the projection deflection unit 20 ais small, the emission light is less affected by the small width. However, when the width of the light receiving deflection unit 20 bis smaller, the reflected light is less likely to be detected because the amount of the reflected light is reduced.According to the present embodiment, the small width portion is formed in the projection deflection portion 20 a, thus less affecting the distance measurement accuracy. In addition, the occurrence of ghost images generated by reflecting transmission waves at the end portion of the projection deflection unit 20 ain a direction different from the reflection direction can be reduced.According to the present embodiment, the light projecting unit 10 corresponds to a transmitting unit, the light receiving unit 30 corresponds to a receiving unit, the projection deflecting unit 20 acorresponds to a transmitting deflecting unit, and the light receiving deflecting section 20 bcorresponds to a receiving deflecting unit.8. Further EmbodimentsThe embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments and can be obviously modified in various ways.(8a) In the above-described embodiments, an example has been described in which the two deflection mirrors 211 and 212 and the mirror support member 213 are gripped by the clamps 214 and 215 at both ends of the narrow width portions in a direction orthogonal to the rotation axis of the two deflection mirrors 211 and 212. However, the two deflecting mirrors 211 and 212 and the mirror supporting member 213 may be gripped by the clamps at one end out of the two ends.(8b) According to the above-described embodiments, all the portions of the clamps 214 and 215 and the guides 216 and 217 are arranged within the width in the longitudinal direction of the large width portion of the two deflection mirrors 211 and 212. However, a part of the portions of the clamps 214 and 215 and the guides 216 and 217 may be disposed outside the width in the longitudinal direction of the large width portion.(8c) According to the above-described embodiments, the deflection mirrors 211 and 212 are formed to have a shape integrating two rectangles having different widths in the longitudinal direction. More specifically, it is configured that a first rectangle and a second rectangle whose longitudinal width is larger than that of the first rectangle are arranged along a common central axis, the central axes being aligned with each other along the short directions of the respective rectangles, thereby integrating both rectangles. However, it is not limited to the above-described shape as long as the two deflection mirrors have the small width portions. The two deflection mirrors 211 and 212 may be formed to have a narrow width portion interposed between one wide width portion and another wide width portion, for example.(8d) According to the above-described embodiments, an upper portion with respect to the two partition plates 22 and 23 is the projection deflection portion 20a, and a lower portion is the light receiving deflection portion 20b in the two deflection mirrors 211 and 212. However, the LIDAR device 1 may be configured such that the upper portion is the light receiving baffle portion 20 band the lower portion is the projection baffle portion 20 a.(8e) According to the above-described embodiments, the distance measurement device is, for example, a LIDAR device 1. The distance measurement device may be formed of, for example, a millimeter wave radar device or the like.(8f) The functions of a single component in the above-described embodiments may be distributed to a plurality of components, or the functions of a plurality of components may be integrated into a single component. A part of the configuration of the above-described embodiments may be omitted. In addition, a part of the configuration of the above-described embodiments may be added to or replaced with the configuration of another above-described embodiment.

Claims

A distance measurement device (1) comprising: a mirror module (21) that rotates when driven by a motor (24), the mirror module comprising: two deflection mirrors (211, 212) each having a small width portion in which a width of a reflection surface along a direction orthogonal to a rotation axis is smaller than that of another portion of the reflection surface; a mirror support member (213) formed in a disk shape having a shape corresponding to a shape of the reflection surface on both surfaces, the two deflection mirrors being disposed on the respective both surfaces; and a clamp (214, 215) that grips the two deflection mirrors and the mirror support member at at least one end portion of two end portions of a portion in the mirror support portion corresponding to the small width portion in a direction orthogonal to the rotation axis.The distance measurement device according to claim 1, wherein the mirror support member includes two guides (216, 217) each formed as a protrusion disposed on a side surface of a portion in the mirror support member corresponding to the narrow width portion, and the protrusion adjusts a position of the two deflection mirrors on both sides with respect to a direction orthogonal to the rotation axis in the narrow width portion.The distance measurement apparatus according to claim 1 or 2, further comprising: a transmission unit (10) configured to transmit transmission waves; and a reception unit (30) configured to detect reflection waves from an object to which the transmission waves are radiated, wherein the small width portion is formed on one side of two sides of the two deflection mirrors with respect to a direction parallel to the rotation axis; the two deflection mirrors include two portions, of which a transmission deflection unit (20a) is a portion disposed on the transmission unit side, and a reception deflection unit (20b) is a portion disposed on the reception unit side; and the small width portion is formed in the transmission deflection unit.

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