JP2021081374A - Sensor device - Google Patents

Abstract

To reduce stray light of a transmission-reception system in a sensor device having a movable reflection part.SOLUTION: A movable reflection part 110 scans an object located outside a sensor device 10 by electromagnetic waves. A first reflection part 120 bends along a first curved surface CS1. The first curved surface CS1 uses a first axis AX1 as an axis of symmetry. The first reflection part 120 also has a focal point (a first focal point FP1) in a part that overlaps with the first axis AX1 in the direction in which the first axis AX1 extends. The position of the first focal point FP1 and the position of the movable reflection part 110 are substantially the same position. The first reflection part 120 does not overlap with the movable reflection part 110 in the direction of extension of the first axis AX1. The second reflection part 130 bends along a second curved surface CS2. The second curved surface CS2 uses a second axis AX2 as an axis of symmetry. The second axis AX2 expands parallel to the first axis AX1 of the first curved surface CS1. The second reflection part 130 and the first reflection part 120 face opposite directions.SELECTED DRAWING: Figure 2

Description

The present invention relates to a sensor device.

In recent years, a LiDAR (Light Detection And Ringing) system has been developed as sensing using a laser. For example, Patent Document 1 describes a LiDAR system having a Schmidt-Cassegrain telescope. In this LiDAR system, the pulsed light emitted from the laser is sent to an object in the atmosphere via the Schmidt-Cassegrain telescope. The pulsed light sent to the object and scattered by the object is collected by the Schmidt-Cassegrain telescope and detected by the photodiode.

Patent Document 2 describes a sensor LiDAR system having a MEMS (Micro Electro Mechanical Systems) mirror and a light emitting / receiving lens. The MEMS mirror uses electromagnetic waves such as infrared rays to scan an object located outside the LiDAR system. In this LiDAR system, the light emitted from the light source is reflected by the MEMS mirror, transmitted through the light emitting / receiving lens, and irradiated to the object. The light that is applied to the object and is reflected or scattered by the object is transmitted through the light emitting / receiving lens and detected by the photodetector.

Patent Document 3 describes a surveillance system having an optical scanning mechanism and a wide-angle lens. In this monitoring system, the light emitted from the light source passes through the wide-angle lens via the optical scanning mechanism and irradiates the object. The light that is applied to the object and is reflected or scattered by the object passes through the wide-angle lens and enters the image sensor.

Japanese Unexamined Patent Publication No. 2003-130955 JP-A-2019-178966 JP-A-2017-195569

In recent years, unlike the LiDAR system of Patent Document 1, a sensor device having a movable reflecting portion such as a MEMS mirror has been developed. Such a sensor device may include a transmission / reception system having a lens (for example, a telescope system or a wide-angle system), as described in, for example, Patent Document 2 or 3. However, when a lens is used in the transmission / reception system, stray light generated by the reflection of light on the surface of the lens can become noise in the sensor device.

As an example of the problem to be solved by the present invention, it is possible to reduce the stray light of the transmission / reception system in the sensor device having the movable reflection unit.

The invention according to claim 1
It ’s a sensor device,
A movable reflector that scans an object located outside the sensor device with electromagnetic waves, and
It has a focal point that is curved along a virtual first curved surface with the virtual first axis as the axis of symmetry, is located at a position overlapping the first axis in the extending direction of the first axis, and has a focal point of the focal point. A first reflecting portion whose position and the position of the movable reflecting portion substantially coincide with each other and do not overlap with the movable reflecting portion in the extending direction of the first axis.
A second reflection that is curved along a virtual second curved surface whose axis of symmetry is a virtual second axis that extends parallel to the first axis of the first curved surface and faces the first reflecting portion. Department and
Is a sensor device equipped with

It is a figure which shows the structure of the sensor device which concerns on embodiment. It is a figure which shows the structure of the transmission / reception system shown in FIG. It is a figure which shows the modification of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all drawings, similar components are designated by the same reference numerals, and description thereof will be omitted as appropriate.

FIG. 1 is a diagram showing a configuration of a sensor device 10 according to an embodiment. FIG. 2 is a diagram showing the configuration of the transmission / reception system 100 shown in FIG.

The sensor device 10 includes a transmission unit 210, a reception unit 220, a collimator lens 230, a beam splitter 240, a first lens 250, a second lens 260, and a transmission / reception system 100. The transmission / reception system 100 (sensor device 10) includes a movable reflection unit 110, a first reflection unit 120, and a second reflection unit 130. In FIG. 1, the electromagnetic waves propagating through the transmission unit 210, the reception unit 220, the collimator lens 230, the beam splitter 240, the first lens 250, the second lens 260, and the transmission / reception system 100 are indicated by broken lines. In FIG. 1, the electromagnetic wave is light, and the broken line indicates the main ray.

In FIG. 2, the path in which the electromagnetic wave reflected or scattered by the object located at the second focal point FP2 follows in order through the reflection by the second reflection unit 130, the reflection by the first reflection unit 120, and the reflection by the movable reflection unit 110. It is shown.

In FIG. 2, the first direction X is the extension direction of the first axis AX1 (details will be described later) of the first reflection unit 120 or the second axis AX2 (details will be described later) of the second reflection unit 130. , The second direction Y is a direction orthogonal to the first direction X. In the positive direction of the first direction X (the direction indicated by the arrow of the first direction X in FIG. 2), the second reflecting portion 130 is located from the side where the first reflecting portion 120 is located along the first direction X. The direction toward the side, and the negative direction of the first direction X (the direction opposite to the direction indicated by the arrow of the first direction X in FIG. 2) is the side on which the second reflecting portion 130 is located along the first direction X. This is the direction toward the side where the first reflecting unit 120 is located. The positive direction of the second direction Y (the direction indicated by the arrow of the second direction Y in FIG. 2) is the direction from the side where the first axis AX1 is located to the side where the second axis AX2 is located, and is the second direction. The negative direction of Y (the direction opposite to the direction indicated by the arrow of the second direction Y in FIG. 2) is the direction from the side where the second axis AX2 is located to the side where the first axis AX1 is located.

In FIG. 2, the first curved surface CS1 (details will be described later) of the first reflecting unit 120 and the second curved surface CS2 (details will be described later) of the second reflecting unit 130 are virtual surfaces. That is, the first curved surface CS1 and the second curved surface CS2 do not physically exist. In FIG. 2, for the sake of explanation, the first curved surface CS1 and the second curved surface CS2 are shown by broken lines. In FIG. 2, the first axis AX1 of the first reflection unit 120 and the second axis AX2 of the second reflection unit 130 are virtual axes. That is, the first axis AX1 and the second axis AX2 do not physically exist. In FIG. 2, for the sake of explanation, the first axis AX1 and the second axis AX2 are shown by broken lines.

The outline of the transmission / reception system 100 will be described with reference to FIG. The movable reflection unit 110 scans an object (not shown in FIG. 2) located outside the sensor device 10 by electromagnetic waves. The first reflecting portion 120 is curved along the first curved surface CS1. The first curved surface CS1 has the first axis AX1 as the axis of symmetry. Further, the first reflecting unit 120 has a focal point (first focal point FP1) at a position overlapping with the first axis AX1 in the stretching direction (first direction X) of the first axis AX1. The position of the first focus FP1 and the position of the movable reflection unit 110 substantially coincide with each other. Further, the first reflecting portion 120 does not overlap with the movable reflecting portion 110 in the stretching direction (first direction X) of the first axis AX1. The second reflecting portion 130 is curved along the second curved surface CS2. The second curved surface CS2 has the second axis AX2 as the axis of symmetry. The second axis AX2 extends parallel to the first axis AX1 of the first curved surface CS1 (that is, in the first direction X). Further, the second reflecting unit 130 faces the first reflecting unit 120.

In the present embodiment, the transmission / reception system 100 uses reflections (that is, first reflection unit 120 and second reflection unit 130). That is, the transmission / reception system 100 does not need to have a lens. Therefore, the stray light due to the lens can be reduced. When the stray light from the lens enters the receiving unit 220, which will be described later, the signal generated by the stray light in the receiving unit 220 is the signal generated in the receiving unit 220 by the light reflected by the object located at a short distance from the sensor device 10. It can be noise. However, in the present embodiment, the generation of such noise can be reduced. Further, in the present embodiment, the light propagating between the first lens 250 (FIG. 1) and the movable reflection unit 110 passes through the first axis AX1 of the first reflection unit 120, and the first reflection unit 120 is not located on the first axis AX1. Therefore, the light propagating between the first lens 250 (FIG. 1) and the movable reflection unit 110 can be prevented from being blocked by the first reflection unit 120.

In the present embodiment, the position of the first focal point FP1 and the position of the movable reflection unit 110 do not have to be exactly the same, and may be substantially the same. For example, the position of the first focal point FP1 and the position of the movable reflecting portion 110 may deviate by tolerances such as component accuracy and assembly accuracy. Further, the position of the first focal point FP1 and the position of the movable reflection unit 110 are d in the first direction x when the maximum deflection angle of the movable reflection unit 110 is Φmax and the effective diameter of the movable reflection unit 110 is d. It may be deviated by a distance of / (4sinΦmax), or may be deviated by d / 2 in the second direction.

In this embodiment, the transmission / reception system 100 is a telescope system. However, the transmission / reception system 100 may be a transmission / reception system different from the telescope system, for example, a wide-angle system.

The details of the sensor device 10 will be described with reference to FIG.

The transmission unit 210 transmits an electromagnetic wave. In one example, the electromagnetic wave transmitted by the transmitter 210 is light, specifically infrared. However, the electromagnetic wave transmitted by the transmission unit 210 may be light having a wavelength different from the wavelength of infrared rays (for example, visible light or ultraviolet rays), or an electromagnetic wave having a wavelength different from the wavelength of light (for example, radio waves). There may be. In one example, the transmission unit 210 transmits a pulse wave. However, the transmission unit 210 may transmit a continuous wave (CW). In one example, the transmitter 210 is an element (eg, a laser diode (LD)) capable of converting electrical energy (eg, current) into electromagnetic waves.

The electromagnetic wave transmitted from the transmission unit 210 is incident on the collimator lens 230. The electromagnetic wave incident on the collimator lens 230 is collimated by the collimator lens 230. The electromagnetic wave transmitted through the collimator lens 230 is transmitted through the beam splitter 240 and converged on the movable reflection unit 110 by the first lens 250. That is, the first lens 250 functions as a convergence unit that converges the electromagnetic wave transmitted from the transmission unit 210 to the movable reflection unit 110.

The electromagnetic wave incident on the movable reflection unit 110 from the transmission unit 210 via the collimator lens 230, the beam splitter 240, and the first lens 250 in this order is reflected by the movable reflection unit 110. This electromagnetic wave is emitted toward the outside of the sensor device 10 through the reflection by the first reflection unit 120 and the reflection by the second reflection unit 130 in order. The electromagnetic wave emitted toward the outside of the sensor device 10 is irradiated to an object (not shown in FIG. 1) located outside the sensor device 10, and is reflected or scattered by this object. The electromagnetic wave reflected or scattered by the object enters the movable reflection unit 110 through the reflection by the second reflection unit 130 and the reflection by the first reflection unit 120 in order. This electromagnetic wave enters the receiving unit 220 through the reflection by the movable reflection unit 110, the transmission of the first lens 250, the reflection by the beam splitter 240, and the transmission of the second lens 260 in this order. The receiving unit 220 receives the electromagnetic wave incident on the receiving unit 220. In one example, the receiver 220 is an element (eg, an avalanche photodiode (APD)) capable of converting electromagnetic waves into electrical energy (eg, current).

The sensor device 10 is, for example, LiDAR (Light Detection And Ringing). In one example, the sensor device 10 measures the distance between the sensor device 10 and an object located outside the sensor device 10 based on ToF (Time of Flight). In this example, the sensor device 10 is located outside the sensor device 10 and the time when the electromagnetic wave is transmitted from the sensor device 10 (for example, the time when the electromagnetic wave is transmitted from the transmission unit 210) and the time when the electromagnetic wave is transmitted from the sensor device 10. The distance is calculated based on the difference between the time when the electromagnetic wave reflected or scattered by the object is received by the sensor device 10 (for example, the time when the electromagnetic wave is received by the receiving unit 220).

The details of the transmission / reception system 100 will be described with reference to FIG.

The movable reflection unit 110 is, for example, a MEMS (Micro Electro Mechanical Systems) mirror. The movable reflecting unit 110 relates to a virtual axis passing through the first focal point FP1 of the first reflecting unit 120 in a direction orthogonal to both the first direction X and the second direction Y (direction perpendicular to the paper surface of FIG. 2). It is rotatable. The movable reflector 110 may be rotatable with respect to another virtual axis orthogonal to the virtual axis. That is, the movable reflection unit 110 may be a two-axis mirror. However, the movable reflection unit 110 may be a uniaxial mirror.

The first reflecting unit 120 is, for example, a concave mirror lacking a region through which the first axis AX1 of the first curved surface CS1 passes. In this case, the electromagnetic wave propagating between the first lens 250 (FIG. 1) and the movable reflection unit 110 (first focus FP1) can be prevented from being blocked by the first reflection unit 120. The first curved surface CS1 of the first reflecting portion 120 is, for example, a paraboloid. In this example, the first reflecting unit 120 can be, for example, a non-axis paraboloid mirror. The focal length f1 of the first reflecting portion 120 (the distance between the intersection of the first curved surface CS1 and the first axis AX1 and the first focal length FP1 in the first direction X) is the shape of the first reflecting portion 120 (for example,). , The radius of curvature of the first curved surface CS1). The first curved surface CS1 of the first reflecting portion 120 may be a curved surface different from the paraboloid surface, for example, an ellipsoidal surface.

ｚ：サグ量
ｈ：第１軸ＡＸ１からの第２方向Ｙにおける距離
ｃ：曲率
ｋ：円錐定数
Ａ、Ｂ、Ｃ、Ｄ、・・・：実数（非球面係数） More specifically, the first curved surface CS1 may be represented by, for example, the following equation (1).

z: Sag amount h: Distance from the first axis AX1 in the second direction Y c: Curvature k: Conical constants A, B, C, D, ...: Real numbers (aspherical coefficients)

The second curved surface CS2 of the second reflecting portion 130 is, for example, a paraboloid. The second curved surface CS2 may be a curved surface different from the paraboloid, for example, an ellipsoidal surface. The focal length f2 of the second reflecting portion 130 (the distance between the intersection of the second curved surface CS2 and the second axis AX2 and the second focal length FP2 in the first direction X) is the shape of the second reflecting portion 130 (for example,). , The radius of curvature of the second reflecting portion 130). In the example shown in FIG. 2, the second reflecting portion 130 includes a region located on the positive side of the second direction Y with respect to the second axis AX2 and a region through which the second axis AX2 of the second curved surface CS2 passes. It lacks a part of the region located on the negative direction side of the second direction Y with respect to the second axis AX2. Therefore, the transmission / reception system 100 can be miniaturized. However, the second reflecting unit 130 does not have to lack the region lacking in the present embodiment.

The type of curved surface of the first curved surface CS1 (for example, a paraboloid or an ellipsoid) and the type of the curved surface of the second curved surface CS2 (for example, a paraboloid or an ellipsoid) may be the same as each other, or They may be different from each other. That is, each of the first curved surface CS1 and the second curved surface CS2 can be a paraboloid or an ellipsoid, for example, independently of each other.

The second axis AX2 of the second reflection unit 130 is the direction of the first reflection unit 120 from the first axis AX1 side to the first reflection unit 120 side (positive direction of the second direction Y). The distance Δy is shifted with respect to the first axis AX1. Therefore, the electromagnetic wave incident on the movable reflection unit 110 from the first lens 250 (FIG. 1) passes through the reflection by the first reflection unit 120 and the reflection by the second reflection unit 130 in order, and is in the second direction with respect to the first axis AX1. It will be converged to the region moved in the positive direction of Y.

The first reflecting portion 120 and the second reflecting portion 130 face each other in the first direction X. Therefore, the electromagnetic wave reflected by the movable reflection unit 110 and incident on the first reflection unit 120 is incident on the second reflection unit 130. Further, the electromagnetic wave reflected or scattered by an object located outside the sensor device 10 and incident on the second reflection unit 130 is incident on the first reflection unit 120.

FIG. 3 is a diagram showing a modified example of FIG. The example shown in FIG. 3 is the same as the example shown in FIG. 2 except for the following points. In FIG. 3, the positive direction of the second direction Y (the direction indicated by the arrow of the second direction Y in FIG. 3) is the direction from the side where the second axis AX2 is located to the side where the first axis AX1 is located. The negative direction of the second direction Y (the direction opposite to the direction indicated by the arrow of the second direction Y in FIG. 3) is the direction from the side where the first axis AX1 is located to the side where the second axis AX2 is located. Is.

In FIG. 3, four electromagnetic waves incident on the movable reflection unit 110 from the first lens 250 (FIG. 1) are traced in order through reflection by the movable reflection unit 110, reflection by the first reflection unit 120, and reflection by the second reflection unit 130. The route is shown. Which of the four paths the electromagnetic wave incident on the movable reflection unit 110 from the first lens 250 (FIG. 1) follows is determined by the electromagnetic wave incident on the movable reflection unit 110 from the first lens 250 (FIG. 1). It depends on the orientation of the movable reflector 110 at the time.

The second axis AX2 of the second reflection unit 130 is the first reflection unit in the direction from the first axis AX1 side of the first reflection unit 120 to the opposite side of the first reflection unit 120 (negative direction of the second direction Y). It is shifted by a distance Δy with respect to the first axis AX1 of 120. Therefore, the electromagnetic wave incident on the movable reflection unit 110 from the first lens 250 (FIG. 1) passes through the reflection by the first reflection unit 120 and the reflection by the second reflection unit 130 in order, and is in the second direction with respect to the first axis AX1. It will be converged to the region moved in the negative direction of Y. Also in this example, the first reflecting unit 120 does not block the light propagating between the first lens 250 (FIG. 1) and the movable reflecting unit 110. Further, since the transmission / reception system 100 does not need to have a lens, the stray light of the transmission / reception system 100 can be reduced.

Although the embodiments and modifications have been described above with reference to the drawings, these are examples of the present invention, and various configurations other than the above can be adopted.

10 Sensor device 100 Transmission / reception system 110 Movable reflector 120 First reflector 130 Second reflector 210 Transmitter 220 Receiver 230 Collimeter lens 240 Beam splitter 250 First lens 260 Second lens AX1 First axis AX2 Second axis CS1 First 1 Curved surface CS2 2nd curved surface FP1 1st focus FP2 2nd focus X 1st direction Y 2nd direction f1 Focal length f2 Focal length

Claims (5)

It ’s a sensor device,
A movable reflector that scans an object located outside the sensor device with electromagnetic waves, and
It has a focal point that is curved along a virtual first curved surface with the virtual first axis as the axis of symmetry, is located at a position overlapping the first axis in the extending direction of the first axis, and has a focal point of the focal point. A first reflecting portion whose position and the position of the movable reflecting portion substantially coincide with each other and do not overlap with the movable reflecting portion in the extending direction of the first axis.
A second reflection that is curved along a virtual second curved surface whose axis of symmetry is a virtual second axis that extends parallel to the first axis of the first curved surface and faces the first reflecting portion. Department and
A sensor device equipped with. In the sensor device according to claim 1,
The second axis of the second reflecting portion moves in a direction from the first axis side of the first reflecting portion toward the first reflecting portion side with respect to the first axis of the first reflecting portion. Being a sensor device. In the sensor device according to claim 1 or 2.
The electromagnetic wave reflected by the movable reflecting portion and incident on the first reflecting portion is incident on the second reflecting portion.
A sensor device in which the electromagnetic wave reflected or scattered by the object located outside the sensor device and incident on the second reflecting portion is incident on the first reflecting portion. In the sensor device according to claim 1,
A sensor device in which each of the first curved surface and the second curved surface is a paraboloid or an ellipsoid independently of each other. In the sensor device according to any one of claims 1 to 4.
The transmitter that transmits the electromagnetic waves and
A converging unit that converges the electromagnetic wave transmitted from the transmitting unit to the movable reflecting unit, and a converging unit.
A sensor device further equipped with.

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