EP-4737981-A1 - MIRROR OSCILLATION DEVICE AND LIDAR DEVICE

EP4737981A1EP 4737981 A1EP4737981 A1EP 4737981A1EP-4737981-A1

Abstract

A mirror unit (10) has a mirror surface (11) that reflects light. An extending portion (20) extends from a rear surface (12) of the mirror unit (10), facing away from the mirror surface (11). A shaft (30) is fixed to the extending portion (20). A base (40) is disposed in a region on a side of the mirror unit (10) facing away from the mirror surface (11). A bearing (50) is disposed on the base (40) and faces the extending portion (20) in an axial direction of the shaft (30). The bearing (50) supports the shaft (30) to be rotatable relative to the base (40). The mirror unit (10) is capable of oscillating within a predetermined angular range about a central axis (CL) of the shaft (30), together with the shaft (30) and the extending portion (20). At least a part of the bearing (50) and at least a part of the base (40) are disposed within a height range (H1) of the mirror unit (10) in the axial direction of the shaft (30) and in the region on the side of the mirror unit (10) facing away from the mirror surface (11).

Inventors

INUZUKA, YOSHINORI
KAIFU TERUAKI
OKADA KEITA
TOMITA SHODAI

Assignees

DENSO CORPORATION

Dates

Publication Date: 20260506
Application Date: 20240527

Claims (15)

A mirror oscillation device, comprising: a mirror unit (10) including a mirror surface (11) that reflects light; an extending portion (20) that extends from a surface (12) of the mirror unit facing away from the mirror surface; a shaft (30) fixed to the extending portion; a base (40) disposed in a region on a side of the mirror unit facing away from the mirror surface of the mirror unit; and a bearing (50) disposed on the base and facing the extending portion in an axial direction of the shaft, the bearing supporting the shaft to be rotatable relative to the base, wherein the mirror unit is configured to oscillate within a predetermined angular range about a central axis (CL) of the shaft, together with the shaft and the extending portion, and at least a portion of the bearing and at least a portion of the base are disposed within a height range (H1) of the mirror unit in the axial direction of the shaft in the region on the side of the mirror unit facing away from the mirror surface.
The mirror oscillation device according to claim 1, wherein the mirror unit has one outer edge (13) facing one side of the mirror oscillation device in the axial direction and an other outer edge (14) facing an other side of the mirror oscillation device in the axial direction, the bearing has one outer edge (56) facing the one side of the mirror oscillation device in the axial direction, and an other outer edge (57) facing the other side of the mirror oscillation device in the axial direction, the base has one outer edge (46) facing the one side of the mirror oscillation device in the axial direction, and an other outer edge (47) facing the other side of the mirror oscillation device in the axial direction, the one outer edge of the bearing and the one outer edge of the base are positioned at a same height as the one outer edge of the mirror unit in the axial direction, or between the one outer edge of the mirror unit and the other outer edge of the mirror unit in the axial direction, and the other outer edge of the bearing and the other outer edge of the base are positioned at a same height as the other outer edge of the mirror unit in the axial direction, or between the other outer edge of the mirror unit and the one outer edge of the mirror unit in the axial direction.
The mirror oscillation device according to claim 1 or 2, further comprising an actuator (60) configured to drive the mirror unit in an oscillatory manner, together with the shaft and the extending portion, within the predetermined angular range about the central axis of the shaft, wherein at least a portion of the actuator is disposed within the height range of the mirror unit in the axial direction of the shaft in the region on the side of the mirror unit facing away from the mirror surface.
The mirror oscillation device according to claim 3, wherein the actuator has one outer edge (601) facing the one side of the mirror oscillation device in the axial direction and an other outer edge (602) facing the other side of the mirror oscillation device in the axial direction, the one outer edge of the actuator is positioned at a same height as the one outer edge of the mirror unit in the axial direction, or between the one outer edge of the mirror unit and the other outer edge of the mirror unit in the axial direction, and the other outer edge of the actuator is positioned at a same height as the other outer edge of the mirror unit in the axial direction, or between the other outer edge of the mirror unit and the one outer edge of the mirror unit in the axial direction.
The mirror oscillation device according to claim 1 or 2, further comprising a sensor (70) configured to detect an angle of the mirror unit relative to the base, wherein at least a portion of the sensor is disposed within the height range of the mirror unit in the axial direction of the shaft in the region on the side of the mirror unit facing away from the mirror surface.
The mirror oscillation device according to claim 5, wherein the sensor has one outer edge (75) facing the one side of the mirror oscillation device in the axial direction and an other outer edge (76) facing the other side of the mirror oscillation device in the axial direction, the one outer edge of the sensor is positioned at a same height as the one outer edge of the mirror unit in the axial direction, or between the one outer edge of the mirror unit and the other outer edge of the mirror unit in the axial direction, and the other outer edge of the sensor is positioned at a same height as the other outer edge of the mirror unit in the axial direction, or between the other outer edge of the mirror unit and the one outer edge of the mirror unit in the axial direction.
The mirror oscillation device according to claim 1 or 2, further comprising: an actuator configured to drive the mirror unit in an oscillatory manner, together with the shaft and the extending portion, within a predetermined angular range about the central axis of the shaft; and a sensor configured to detect an angle of the mirror unit relative to the base, wherein at least a portion of the actuator and at least a portion of the sensor are disposed within the height range of the mirror unit in the axial direction of the shaft in the region on the side of the mirror unit facing away from the mirror surface.
The mirror oscillation device according to claim 7, wherein the actuator has one outer edge facing the one side of the mirror oscillation device in the axial direction and an other outer edge facing the other side of the mirror oscillation device in the axial direction, the sensor has one outer edge facing the one side of the mirror oscillation device in the axial direction and an other outer edge facing the other side of the mirror oscillation device in the axial direction, the one outer edge of the actuator and the one outer edge of the sensor are positioned at a same height as the one outer edge of the mirror unit in the axial direction, or between the one outer edge of the mirror unit and the other outer edge of the mirror unit in the axial direction, and the other outer edge of the actuator and the other outer edge of the sensor are positioned at a same height as the other outer edge of the mirror unit in the axial direction, or between the other outer edge of the mirror unit and the one outer edge of the mirror unit in the axial direction.
The mirror oscillation device according to claim 5, wherein the sensor is a rotary encoder including a rotary disk (71) configured to rotate together with the shaft and a detecting element (72) configured to detect a position of the rotary disk relative to the base.
The mirror oscillation device according to claim 3, wherein a maximum angle of oscillation of the mirror unit in a counterclockwise direction when viewed from the one side of the mirror oscillation device in the axial direction is referred to as a first angle, a maximum angle of oscillation of the mirror unit in a clockwise direction when viewed from the one side of the mirror oscillation device in the axial direction is referred to as a second angle, an angle at a midpoint between the first angle and the second angle is referred to as a third angle, the base has a surface (44, 45) that faces the mirror unit, and the surface of the base is inclined relative to the mirror unit and extends away from both the shaft and the mirror unit in a state where the mirror unit is positioned at the third angle such that interference between the base and the mirror unit is prevented during oscillation of the mirror unit driven by the actuator.
The mirror oscillation device according to claim 3, wherein the actuator includes: a magnet (61) fixed to the shaft; an electromagnetic coil (63) configured to generate a magnetic field upon energization; and a stator (62) that constitutes a magnetic circuit between the electromagnetic coil and the magnet, and is configured to supply a magnetic flux generated by the electromagnetic coil around the magnet, a maximum angle of oscillation of the mirror unit in a counterclockwise direction when viewed from the one side of the mirror oscillation device in the axial direction is referred to as a first angle, a maximum angle of oscillation of the mirror unit in a clockwise direction when viewed from the one side of the mirror oscillation device in the axial direction is referred to as a second angle, an angle at a midpoint between the first angle and the second angle is referred to as a third angle, the stator has a surface (68) that faces the mirror unit, and the surface of the stator is inclined relative to the mirror unit and extends away from both the shaft and the mirror unit in a state where the mirror unit is positioned at the third angle such that interference between the stator and the mirror unit is prevented during oscillation of the mirror unit driven by the actuator.
The mirror oscillation device according to claim 1 or 2, further comprising a counterweight (22) disposed in a region on a side of the central axis facing away from the mirror unit, and fixed to the extending portion or the shaft.
The mirror oscillation device according to claim 12, wherein the counterweight includes: a resin body (23) fixed to the extending portion or the shaft; and a weight portion (24) made of a material having a higher specific gravity than a specific gravity of the resin body, and fixed to the resin body.
The mirror oscillation device according to claim 12, wherein a center of gravity of an integrated component including the mirror unit, the extending portion, and the counterweight coincides with the central axis of the shaft.
A LiDAR device, comprising: a housing (3) including a window (8) through which laser light passes; the mirror oscillation device (1) according to claim 1, disposed inside the housing; a light source device (4) that is disposed inside the housing, and is configured to irradiate the mirror surface of the mirror unit in the mirror oscillation device with the leaser light; and a light receiving device (5) that is disposed inside the housing, and is configured to receive the laser light that has been scanned by the mirror surface of the mirror unit in the mirror oscillation device, emitted to an outside through the window of the housing, reflected by an external object, returned through the window of the housing, and reflected by the mirror surface of the mirror unit.

Description

CROSS REFERENCE TO RELATED APPLICATION This application is based on Japanese Patent Application No. 2023-108420, filed on June 30, 2023, the contents of which are incorporated herein by reference. TECHNICAL FIELD The present disclosure relates to a mirror oscillation device and a LiDAR device including the mirror oscillation device. BACKGROUND ART Conventionally, mirror oscillation devices have been known as components used in LiDAR devices and other devices. LiDAR is an abbreviation for Light Detection and Ranging, or Laser Imaging Detection and Ranging. LiDAR is a technology that emits laser light and measures a distance to a target object and a shape of the target object based on information from reflected light. The mirror oscillation device described in Patent Literature 1 has a configuration in which a shaft is fixed to a hole provided at a central portion in a thickness direction of a mirror unit, and two bearings, an actuator, and a rotation angle sensor are provided on a portion of the shaft protruding from the mirror unit. Specifically, one bearing and the actuator are disposed on the portion of the shaft protruding from one side of the mirror unit, while the other bearing and the rotation angle sensor are disposed on a portion of the shaft protruding from the other side of the mirror unit. In Patent Literature 1, the shaft is referred to as a "shaft portion", and the actuator is referred to as a "drive unit". PRIOR PATENT LITERATURE PATENT LITERATURE Patent Literature 1:JP 2022-30904 A SUMMARY OF INVENTION However, in the mirror oscillation device described in Patent Literature 1, the actuator, the one bearing, the mirror unit, the other bearing, and the rotation angle sensor are arranged in series in an axial direction in which a central axis of the shaft extends, thereby increasing a size in the axial direction. In addition, a proportion of a mirror surface of the mirror unit by size in the axial direction relative to the mirror oscillation device is small. Therefore, when the mirror oscillation device described in Patent Literature 1 is used in a LiDAR device, a size of the mirror unit in the axial direction increases as the mirror oscillation device becomes large. Furthermore, the proportion of the mirror surface of the mirror unit relative to the mirror unit in the axial direction is small. When the LiDAR device is mounted on, for example, a roof of a vehicle, a rooftop has a convex shape protruding significantly upward by a size of the LiDAR device, which may increase air resistance during driving and may decrease fuel efficiency or electric efficiency. Alternatively, the LiDAR device may protrude significantly from the roof toward an interior of the vehicle, which may reduce forward visibility of the driver. In view of the two above circumstances, a size of the mirror unit in the axial direction may be reduced. However, when the mirror unit is small, a spot diameter of laser beam also becomes small, which may result in performance degradation, such as degradation in S/N ratio or decrease in the measurement range. The objective of the present disclosure is to reduce a size of a mirror unit of a mirror oscillation device in an axial direction, and increase a proportion of the mirror unit by size in the axial direction relative to the mirror oscillation device. According to an aspect of the present disclosure, a mirror oscillation device includes a mirror unit, an extending portion, a shaft, a base, and a bearing. The mirror unit includes a mirror surface that reflects light. The extending portion extends from a surface of the mirror unit facing away from the mirror surface. The shaft is fixed to the extending portion. The base is disposed in a region on a side of the mirror unit facing away from the mirror surface of the mirror unit. The bearing is disposed on the base and faces the extending portion in an axial direction of the shaft. The bearing supports the shaft to be rotatable relative to the base. The mirror unit is configured to oscillate within a predetermined angular range about a central axis of the shaft, together with the shaft and the extending portion. At least a portion of the bearing and at least a portion of the base are disposed within a height range of the mirror unit in the axial direction of the shaft in the region on the side of the mirror unit facing away from the mirror surface. Accordingly, the size of the mirror unit of the mirror oscillation device in the axial direction can be reduced by arranging the bearing and the base in the region on the side of the mirror unit facing away from the mirror surface. Furthermore, the proportion of the mirror surface of the mirror unit by size in the axial direction relative to the mirror oscillation device can be increased. Thus, the LiDAR device using this mirror oscillation device can reduce the size of the mirror unit in the axial direction, i.e., the size perpendicular to the direction in which the mirror unit oscillates. As