WO2022209137A1 - 光学系及び光走査装置 - Google Patents
光学系及び光走査装置 Download PDFInfo
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- WO2022209137A1 WO2022209137A1 PCT/JP2022/000998 JP2022000998W WO2022209137A1 WO 2022209137 A1 WO2022209137 A1 WO 2022209137A1 JP 2022000998 W JP2022000998 W JP 2022000998W WO 2022209137 A1 WO2022209137 A1 WO 2022209137A1
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- reflecting surface
- light
- axis
- optical system
- reflected light
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- 230000003287 optical effect Effects 0.000 title claims abstract description 87
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Classifications
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/0816—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light by means of one or more reflecting elements
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/481—Constructional features, e.g. arrangements of optical elements
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
- G02B26/08—Optical devices or arrangements for the control of light using movable or deformable optical elements for controlling the direction of light
- G02B26/10—Scanning systems
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/28—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising
- G02B27/286—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for polarising for controlling or changing the state of polarisation, e.g. transforming one polarisation state into another
Definitions
- the technology of the present disclosure relates to an optical system and an optical scanning device.
- LiDAR Light Detection And Ranging
- the first method is a mechanical scanning method in which a laser light source and a light receiving element are rotated by a mechanical mechanism such as a motor, and laser light is scanned in all directions of 360 degrees (hereinafter referred to as omnidirectional scanning).
- the second method is a MEMS method in which laser light is scanned by deflecting it with a movable mirror (also called a MEMS mirror) made up of MEMS (Micro Electro Mechanical Systems).
- MEMS Micro Electro Mechanical Systems
- Omnidirectional scanning is also possible in MEMS-type LiDAR (for example, WO 2019/167587 and non-patent literature (“Resonant biaxial 7-mm MEMS mirror for omnidirectional scanning”, J. Micro/Nanolith. MEMS MOEMS 13(1), 011103 (Jan-Mar 2014)).
- MEMS type LiDAR omnidirectional scanning is enabled by using a rotationally symmetric optical system for converting light deflected by a movable mirror into a horizontal direction. is described.
- a MEMS-type LiDAR when omnidirectional scanning is performed using a rotationally symmetric optical system, the light deflected by the movable mirror is reflected by the optical system and then emitted from the LiDAR to the outside as scanning light.
- the beam diameter of the scanning light emitted from the LiDAR may expand due to reflection in the optical system.
- the spatial resolution of distance measurement decreases.
- the optical system described in WO 2019/167587 does not take into account the decrease in resolution due to the spread of the beam diameter.
- the optical system described in the above non-patent document is realized only when the movable angle (also referred to as the deflection angle) of the MEMS mirror reaches 15°.
- the movable angle also referred to as the deflection angle
- the optical system described in the above non-patent document has not been realized.
- An object of the technique of the present disclosure is to provide an optical system and an optical scanning device capable of suppressing deterioration in resolution.
- an optical system of the present disclosure is an optical system into which polarized light deflected by a movable mirror is incident, is rotationally symmetrical about a first axis, and reflects the polarized light.
- a first reflecting member having a first reflecting surface that emits the first reflected light, and a second reflecting surface that is rotationally symmetrical about the first axis and reflects the first reflected light and emits the second reflected light.
- the movable mirror rotates in a state in which the normal direction is tilted within a certain angular range with respect to the first axis.
- the polarized light is parallel light, and is reflected by the second reflecting surface when the parallel light is virtually incident on the second reflecting surface from the condensing position of the first reflected light and the optical path of the second reflected light. It is preferable that the condensing position of the virtual image of the reflected light matches.
- the distance from the first reflecting surface to the condensing position of the first reflected light is f1
- the distance from the second reflecting surface to the condensing position of the virtual image is f2
- the first axis between the first reflecting surface and the second reflecting surface is within the range of 0.9 ⁇ d ⁇ f1 ⁇ f2 ⁇ 1.1 ⁇ d.
- the shape of either one of the first reflecting surface and the second reflecting surface is preferably a hyperboloid.
- the shape of either one of the first reflecting surface and the second reflecting surface is preferably an odd-order aspherical surface.
- a prism that is rotationally symmetrical with respect to the first axis, is arranged outside the second reflecting member, and refracts the second reflected light.
- the cross-sectional shape obtained by cutting the prism along a plane parallel to the first axis is preferably triangular.
- An optical scanning device of the present disclosure includes any one of the optical systems described above, a movable mirror device having a movable mirror, and a light source that emits light to be incident on the movable mirror.
- the second reflected light is preferable to emit the second reflected light as scanning light in all directions around the first axis.
- FIG. 1 is a block diagram showing an example of a schematic configuration of a LiDAR device;
- FIG. It is a perspective view showing an example of a schematic structure of a movable mirror device. It is a figure which shows a mode that a movable mirror precesses.
- It is a schematic perspective view showing an example of an optical system.
- 1 is a schematic exploded perspective view showing an example of an optical system;
- FIG. It is a schematic sectional drawing which shows an example of an optical system. It is a figure explaining the positional relationship of a 1st reflective surface, a 2nd reflective surface, and a movable mirror.
- 4 is a diagram showing values of parameters representing shapes of a first reflecting surface and a second reflecting surface according to the first embodiment;
- FIG. 1 is a block diagram showing an example of a schematic configuration of a LiDAR device
- FIG. is a perspective view showing an example of a schematic structure of a movable mirror device. It is a figure which shows a
- FIG. 4 is a simulation image representing a cross-sectional shape of scanning light according to the first embodiment
- FIG. 10 is a diagram showing values of parameters representing shapes of a first reflecting surface and a second reflecting surface according to the second embodiment
- It is a simulation image showing the cross-sectional shape of the scanning light according to the second embodiment.
- FIG. 11 is a schematic cross-sectional view showing the configuration of an optical system according to a third embodiment
- FIG. 11 is a diagram showing values of parameters representing shapes of a first reflecting surface and a second reflecting surface according to the third embodiment
- FIG. 10 is a diagram showing values of parameters representing shapes of a refracting surface, a reflecting surface, and a second reflecting surface according to the third embodiment
- It is a figure explaining the vertical scanning which concerns on 4th Embodiment.
- FIG. 10 is a diagram showing values of parameters representing shapes of a first reflecting surface and a second reflecting surface according to the fourth embodiment; It is a simulation image showing the cross-sectional shape of scanning light according to the fourth embodiment. It is a schematic sectional drawing which shows the structure of the optical system which concerns on a comparative example.
- FIG. 5 is a diagram showing values of parameters representing shapes of a first reflecting surface and a second reflecting surface according to a comparative example; It is a simulation image showing the cross-sectional shape of scanning light according to a comparative example.
- FIG. 1 shows a schematic configuration of a LiDAR device 2 according to one embodiment.
- the LiDAR device 2 emits scanning light Ls to the object 3 and receives its return light Lr to measure the distance to the object 3 .
- the LiDAR device 2 is mounted, for example, on an automobile, and acquires distance information of surrounding obstacles.
- the LiDAR device 2 is an example of an “optical scanning device” according to the technology of the present disclosure.
- the LiDAR device 2 includes a light source 10, a movable mirror device 11, an optical system 12, a light receiving section 13, and a control section .
- the movable mirror device 11 includes a movable mirror 20 and a driving section 35 for driving the movable mirror 20 .
- the optical system 12 includes a first reflecting member 40 , a second reflecting member 41 and a prism 42 .
- the light source 10 is, for example, a laser diode, and emits laser light L toward the movable mirror 20 of the movable mirror device 11 .
- the laser light L is, for example, infrared rays with a wavelength of 905 nm. Also, the laser light L is, for example, pulsed. Note that the laser light L is an example of “light emitted by a light source” according to the technology of the present disclosure.
- the light source 10 is not limited to laser diodes, and lasers of various configurations such as DPSS (Diode Pumped Solid State) lasers and fiber lasers can be used.
- the laser light is not limited to the above laser light, and pulsed laser light generally used for LiDAR having a wavelength from 850 nm to near-infrared light in the band of 1550 nm can be used, for example.
- the movable mirror 20 deflects the laser light L incident from the light source 10 by reflecting it. That is, the movable mirror 20 reflects the incident laser light L and emits it as the polarized light Ld.
- the polarized light Ld emitted from the movable mirror 20 enters the optical system 12 .
- the polarized light Ld incident on the optical system 12 is sequentially reflected by the first reflecting member 40 and the second reflecting member 41, refracted by the prism 42, and then emitted to the outside of the LiDAR device 2 as the scanning light Ls.
- the return light Lr from the object 3 enters the optical system 12 .
- the return light Lr incident on the optical system 12 is refracted by the prism 42 , reflected by the second reflecting member 41 and the first reflecting member 40 in order, and then incident on the movable mirror 20 .
- the return light Lr incident on the movable mirror 20 is deflected by the movable mirror 20 and then guided to the light receiving section 13 by being reflected by, for example, a half mirror 50 (see FIG. 6).
- a half mirror 50 instead of the half mirror 50, a mirror having a through hole for passing the laser light L and a reflecting surface for reflecting the return light Lr may be used.
- the light receiving unit 13 receives the return light Lr and generates a detection signal corresponding to the light amount of the received return light Lr.
- the light receiving section 13 is composed of, for example, an avalanche photodiode.
- a detection signal generated by the light receiving unit 13 is input to the control unit 14 .
- the control unit 14 controls the emission of the laser light L from the light source 10 and performs processing for calculating the distance to the object 3 based on the detection signal input from the light receiving unit 13 . Also, the control unit 14 supplies a driving voltage for driving the movable mirror 20 to the driving unit 35 .
- FIG. 2 shows a schematic configuration of the movable mirror device 11.
- the movable mirror device 11 is a micromirror device formed by etching an SOI (Silicon On Insulator) substrate.
- SOI Silicon On Insulator
- the movable mirror device 11 is also called a MEMS mirror device.
- the movable mirror device 11 has a movable mirror 20 , a first support section 21 , a first movable frame 22 , a second support section 23 , a second movable frame 24 , a connection section 25 and a fixed frame 26 .
- the movable mirror device 11 is a so-called MEMS scanner.
- the movable mirror 20 has a reflecting surface 20A that reflects incident light.
- the reflecting surface 20A is formed of a metal thin film such as gold (Au), aluminum (Al), silver (Ag), or a silver alloy provided on one surface of the movable mirror 20, for example.
- the shape of the reflecting surface 20A is, for example, a circular shape centered on the intersection of the a1 axis and the a2 axis.
- the first support portions 21 are arranged outside the movable mirror 20 at positions opposed to each other across the a2 axis.
- the first support portion 21 is connected to the movable mirror 20 on the a1 axis, and supports the movable mirror 20 so as to swing about the a1 axis.
- the first support portion 21 is a torsion bar extending along the a1 axis.
- the first movable frame 22 is a rectangular frame surrounding the movable mirror 20, and is connected to the movable mirror 20 via the first support 21 on the a1 axis.
- Piezoelectric elements 30 are formed on the first movable frame 22 at opposing positions across the a1 axis.
- a pair of first actuators 31 are configured by forming two piezoelectric elements 30 on the first movable frame 22 .
- the pair of first actuators 31 are arranged at positions facing each other across the a1 axis.
- the first actuator 31 causes the movable mirror 20 to swing about the a1 axis by applying a rotational torque about the a1 axis to the movable mirror 20 .
- the second support portions 23 are arranged outside the first movable frame 22 at positions opposed to each other across the a1 axis.
- the second support portion 23 is connected to the first movable frame 22 on the a2 axis, and supports the first movable frame 22 and the movable mirror 20 so as to be swingable about the a2 axis.
- the second support portion 23 is a torsion bar extending along the a2 axis.
- the second movable frame 24 is a rectangular frame surrounding the first movable frame 22, and is connected to the first movable frame 22 via the second support portion 23 on the a2 axis.
- Piezoelectric elements 30 are formed on the second movable frame 24 at opposing positions across the a2 axis.
- a pair of second actuators 32 are configured by forming two piezoelectric elements 30 on the second movable frame 24 .
- the pair of second actuators 32 are arranged at positions facing each other across the a2 axis.
- the second actuator 32 causes the movable mirror 20 to swing about the a2 - axis by applying rotational torque about the a2 - axis to the movable mirror 20 and the first movable frame 22 .
- the connecting portions 25 are arranged outside the second movable frame 24 at positions opposed to each other with the a1 axis interposed therebetween.
- the connecting portion 25 is connected to the second movable frame 24 on the a2 axis.
- the fixed frame 26 is a rectangular frame that surrounds the second movable frame 24 and is connected to the second movable frame 24 via a connecting portion 25 on the a2 axis.
- the direction normal to the reflecting surface 20A in the state in which the movable mirror 20 is not tilted is defined as the Z-axis direction
- one direction orthogonal to the Z-axis direction is defined as the X-axis direction
- the Z-axis direction and the X-axis direction are orthogonal. Let the direction to do so be the Y-axis direction.
- the pair of first actuators 31 and the pair of second actuators 32 correspond to the driving section 35 described above.
- the control unit 14 described above causes the movable mirror 20 to precess by applying sine-wave driving voltages having different phases to the pair of first actuators 31 and the pair of second actuators 32 .
- FIG. 3 shows how the movable mirror 20 precesses.
- the precession motion is a motion in which the normal line N of the reflecting surface 20A of the movable mirror 20 swings like drawing a circle. That is, the movable mirror 20 rotates in a state in which the normal direction is inclined within a certain angular range with respect to the Z-axis az .
- the Z-axis az is an axis parallel to the Z-axis direction and passing through the center of the movable mirror 20 .
- the Z-axis az is an example of the "first axis" according to the technology of the present disclosure.
- a laser beam L emitted from the light source 10 is incident on the center of the movable mirror 20 along the Z-axis az . As shown in FIG. 3, the deflected light Ld deflected by the movable mirror 20 precessing is emitted from the movable mirror 20 so as to draw a circle.
- FIG. 4 to 6 show the configuration of the optical system 12.
- FIG. FIG. 4 is a schematic perspective view of the optical system 12.
- FIG. FIG. 5 is a schematic exploded perspective view of the optical system 12.
- FIG. FIG. 6 is a schematic cross-sectional view of the optical system 12 cut along the Z-axis az .
- the first reflecting member 40, the second reflecting member 41, and the prism 42, which constitute the optical system 12, are all rotationally symmetrical with respect to the Z axis az .
- the first reflecting member 40 and the second reflecting member 41 are arranged in the order of the first reflecting member 40 and the second reflecting member 41 along the traveling direction of the laser light L emitted from the light source 10 .
- the first reflecting member 40 has a substantially disc-shaped outer shape, and has a hole 40A through which the laser light L passes through in the center.
- a first reflecting surface 40B is formed on the second reflecting member 41 side of the first reflecting member 40 .
- the first reflecting surface 40B is rotationally symmetrical with respect to the Z-axis az . Further, the cross-sectional shape of the first reflecting surface 40B cut along a plane parallel to the Z-axis az is concave.
- the polarized light Ld emitted from the movable mirror 20 is incident on the first reflecting surface 40B.
- the first reflecting surface 40B reflects the incident polarized light Ld and emits it as a first reflected light Lh1.
- the optical path of the first reflected light Lh1 emitted from the first reflecting surface 40B is parallel to the Z-axis az .
- a hole 41A is formed in the center of the second reflecting member 41 for passing the laser light L and the polarized light Ld.
- a second reflecting surface 41B is formed on the first reflecting member 40 side of the second reflecting member 41 .
- the second reflecting surface 41B is rotationally symmetrical with respect to the Z-axis az . Further, the cross-sectional shape of the second reflecting surface 41B cut along a plane parallel to the Z-axis az is convex.
- the first reflected light Lh1 is incident on the second reflecting surface 41B from the first reflecting surface 40B.
- the second reflecting surface 41B reflects the incident first reflected light Lh1 and emits it as a second reflected light Lh2.
- the optical path of the second reflected light Lh2 emitted from the second reflecting surface 41B is directed outward from the Z-axis az .
- the outward direction from the Z-axis az is the radial direction of a circle centered on the Z-axis az .
- a cavity 42A for accommodating the second reflecting member 41 is formed in the center of the prism 42 .
- the prism 42 is rotationally symmetrical with respect to the Z-axis az and is arranged outside the second reflecting member 41 .
- the cross-sectional shape of the prism 42 cut along a plane parallel to the Z-axis az is triangular.
- the second reflected light Lh2 enters the prism 42 from the second reflecting surface 41B.
- the prism 42 refracts the second reflected light Lh2 incident from the second reflecting surface 41B and emits it as the scanning light Ls.
- the emission direction of the scanning light Ls is, for example, a direction orthogonal to the Z-axis az . That is, the scanning light Ls is emitted in all directions around the Z-axis az .
- a half mirror 50 is arranged on the optical path of the laser light L emitted from the light source 10. As shown in FIG. The half mirror 50 transmits the laser light L from the light source 10 and makes it enter the movable mirror 20 , and reflects the return light Lr reflected by the movable mirror 20 so that it enters the light receiving section 13 .
- the laser light L emitted from the light source 10 passes through the half mirror 50, passes through the hole 40A of the first reflecting member 40 and the hole 41A of the second reflecting member 41, and enters the movable mirror 20.
- the laser beam L that has entered the movable mirror 20 is reflected by the movable mirror 20 and emitted from the movable mirror 20 as deflected light Ld.
- the deflected light Ld emitted from the movable mirror 20 passes through the hole 41A of the second reflecting member 41 and enters the first reflecting surface 40B of the first reflecting member 40 .
- the polarized light Ld incident on the first reflecting surface 40B is reflected by the first reflecting surface 40B, and is emitted from the first reflecting surface 40B as the first reflected light Lh1.
- the first reflected light Lh1 emitted from the first reflecting surface 40B travels along the Z-axis az and enters the second reflecting surface 41B of the second reflecting member 41 .
- the first reflected light Lh1 incident on the second reflecting surface 41B is reflected by the second reflecting surface 41B, and is emitted from the second reflecting surface 41B as a second reflected light Lh2.
- the second reflected light Lh2 emitted from the second reflecting surface 41B travels in a direction extending outward from the Z-axis az and enters the prism .
- the second reflected light Lh2 incident on the prism 42 is refracted and then emitted from the prism 42 toward the object 3 (see FIG. 1) as scanning light Ls.
- the return light Lr from the object 3 enters the prism 42, travels in the opposite direction along the optical paths of the deflected light Ld, the first reflected light Lh1, and the second reflected light Lh2, and enters the movable mirror 20. After being reflected by the movable mirror 20 , the return light Lr passes through the hole 40A of the first reflecting member 40 and the hole 41A of the second reflecting member 41 to enter the half mirror 50 . Part of the return light Lr that has entered the half mirror 50 is reflected by the half mirror 50 and enters the light receiving section 13 .
- the first reflecting surface 40B and the second reflecting surface 41B are formed of metal films such as gold (Au), aluminum (Al), or silver (Ag) compounds, for example. Note that the first reflecting surface 40B and the second reflecting surface 41B may be formed of a multilayer reflecting film.
- the prism 42 is made of optical resin such as acrylic, polycarbonate, or Zeonex.
- FIG. 7 explains the positional relationship among the first reflecting surface 40B, the second reflecting surface 41B, and the movable mirror 20.
- h1 represents the distance from the incident position of the polarized light Ld on the first reflecting surface 40B to the Z-axis az .
- h2 represents the distance from the incident position of the first reflected light Lh1 on the second reflecting surface 41B to the Z-axis az .
- d1 represents the distance in the Z-axis direction from the incident position of the deflected light Ld on the first reflecting surface 40B to the movable mirror 20;
- the convergence angle of the laser beam L with respect to the horizontal direction on the first reflecting surface 40B and the second reflecting surface 41B is the same as the spread angle of the laser light L with respect to the horizontal direction.
- the convergence and spread of the laser light L cancel each other, so that the laser light L in the horizontal direction becomes parallel light.
- h1 and h2 do not have to be exactly the same value as long as they are substantially the same.
- the polarized beam Ld is incident on the first reflecting surface 40B as parallel beam. Since the first reflecting surface 40B is a concave surface, the first reflected light Lh1 emitted from the first reflecting surface 40B becomes convergent light. Since the second reflecting surface 41B is a convex surface, the second reflecting surface 41B diverges the first reflected light Lh1 when reflecting it. The curvature of the second reflecting surface 41B is determined so that the second reflected light Lh2 is substantially parallel light.
- P indicates the condensing position of the first reflected light Lh1 when the second reflecting surface 41B does not exist.
- the condensing position of the virtual image of the reflected light reflected by the second reflecting surface 41B is the position of the first reflected light Lh1. It is preferable that it coincides with the condensing position P.
- the condensing position of the virtual image and the condensing position P of the first reflected light Lh1 coincide with each other, so that the second reflected light Lh2 becomes parallel light.
- f1 is the distance from the incident position of the polarized light Ld on the first reflecting surface 40B to the condensing position of the first reflected light Lh1.
- f2 is the distance from the incident position of the first reflected light Lh1 on the second reflecting surface 41B to the condensing position of the virtual image.
- d2 is the distance from the incident position of the polarized light Ld on the first reflecting surface 40B to the incident position of the first reflected light Lh1 on the second reflecting surface 41B.
- the condensing position of the virtual image and the condensing position P of the first reflected light Lh1 do not have to match completely, and may substantially match.
- the difference between f1 and f2 may be within the range of 0.9 ⁇ d2 ⁇ f1 ⁇ f2 ⁇ 1.1 ⁇ d2. This is because astigmatism occurs due to oblique incidence on the curved surface, and the focal lengths in the horizontal direction and the vertical direction are slightly deviated.
- Both the first reflecting surface 40B and the second reflecting surface 41B are aspherical surfaces.
- the shape of the reflecting surface is represented by the following aspheric surface definition formula (1).
- z represents a coordinate in the Z-axis direction.
- h represents the distance from the Z-axis az .
- R is the radius of curvature.
- K is the conic coefficient.
- A1 to A3 are aspheric coefficients.
- R, K, and A1 to A3 are parameters that determine the shape of the reflecting surface. Note that, in the present disclosure, all aspherical coefficients of fourth or higher order are set to zero.
- both the first reflecting surface 40B and the second reflecting surface 41B are hyperboloids.
- Parameters representing the shapes of the first reflecting surface 40B and the second reflecting surface 41B are set to the values shown in FIG. d1 and d2 described above are set to the values shown in FIG.
- FIG. 9 is a simulation image showing the cross-sectional shape of the scanning light Ls at a location about 1 m away from the optical system 12.
- FIG. The image shown in FIG. 9 has a vertical direction parallel to the Z-axis direction and a horizontal direction parallel to a direction orthogonal to the Z-axis direction.
- both the first reflecting surface 40B and the second reflecting surface 41B are hyperboloids, but in this embodiment, the first reflecting surface 40B is a hyperboloid and the second reflecting surface 41B is a paraboloid and Parameters representing the shapes of the first reflecting surface 40B and the second reflecting surface 41B are set to the values shown in FIG. Also, the above d1 and d2 are set to the values shown in FIG.
- FIG. 11 is a simulation image representing the cross-sectional shape of the scanning light Ls at a location about 1 m away from the optical system 12.
- FIG. The image shown in FIG. 11 has a vertical direction parallel to the Z-axis direction and a horizontal direction parallel to a direction orthogonal to the Z-axis direction.
- a back surface type concave mirror called a Mangin mirror is used as the first reflecting member 40 .
- the configuration of the optical system 12 according to the third embodiment is the same as that of the optical system 12 according to the first embodiment, except that the first reflecting member 40 is a back concave mirror.
- the first reflecting member 40 of this embodiment has a refracting surface 40C and a reflecting surface 40D having rotationally symmetrical shapes with respect to the Z-axis az . Both of the cross-sectional shapes obtained by cutting the refracting surface 40C and the reflecting surface 40D along a plane parallel to the Z-axis az are concave.
- the reflective surface 40D is an example of the "first reflective surface” according to the technology of the present disclosure. That is, the reflecting surface 40D corresponds to the first reflecting surface 40B of the first embodiment.
- the polarized light Ld emitted from the movable mirror 20 enters the first reflecting member 40, is refracted by the refracting surface 40C, and then enters the reflecting surface 40D.
- the first reflected light Lh1 emitted from the reflecting surface 40D by reflecting the polarized light Ld on the reflecting surface 40D enters the second reflecting surface 41B of the second reflecting member 41 after being refracted by the refracting surface 40C.
- the refracting surface 40C is a hyperboloid
- the reflecting surface 40D is a paraboloid
- the second reflecting surface 41B is an ellipsoid.
- Parameters representing the shapes of the refracting surface 40C, the reflecting surface 40D, and the second reflecting surface 41B are set to the values shown in FIG.
- the above d1 and d2 are set to the values shown in FIG.
- FIG. 14 is a simulation image representing the cross-sectional shape of the scanning light Ls at a location about 1 m away from the optical system 12.
- FIG. The image shown in FIG. 14 has a vertical direction parallel to the Z-axis direction and a horizontal direction parallel to a direction orthogonal to the Z-axis direction.
- the deflection angle ⁇ of the movable mirror 20 is fixed.
- scanning in the Z-axis direction vertical scanning
- the scanning light Ls emitted from the optical system 12 is between the direction forming +15° with respect to the YZ plane and the direction forming ⁇ 15° with respect to the YZ plane.
- the scanning light Ls is scanned in the Z-axis direction.
- both the first reflecting surface 40B and the second reflecting surface 41B are hyperboloids. Parameters representing the shapes of the first reflecting surface 40B and the second reflecting surface 41B are set to the values shown in FIG. Also, the above d1 and d2 are set to the values shown in FIG.
- FIG. 17 shows an example of the cross-sectional shape of the scanning light Ls emitted from the optical system 12 when the optical system 12 configured based on the conditions shown in FIG. 16 is used and the deflection angle ⁇ is changed.
- FIG. 17A is a simulation image showing the cross-sectional shape of the scanning light Ls when the deflection angle ⁇ is set such that the angle formed by the YZ plane and the scanning light Ls is +15°.
- FIG. 17B is a simulation image showing the cross-sectional shape of the scanning light Ls when the deflection angle ⁇ is set so that the angle formed by the YZ plane and the scanning light Ls is 0°.
- FIG. 17A is a simulation image showing the cross-sectional shape of the scanning light Ls when the deflection angle ⁇ is set such that the angle formed by the YZ plane and the scanning light Ls is +15°.
- FIG. 17B is a simulation image showing the cross-sectional shape of the scanning light Ls when the deflection angle
- FIG. 17C is a simulation image showing the cross-sectional shape of the scanning light Ls when the deflection angle ⁇ is set so that the angle formed by the YZ plane and the scanning light Ls is ⁇ 15°. All the images in FIGS. 17A to 17C are simulation images representing the cross-sectional shape of the scanning light Ls at a location approximately 1 m away from the optical system 12.
- FIG. 18 shows the configuration of an optical system 12 according to a comparative example.
- the first reflecting surface 40B is a flat surface
- the second reflecting surface 41B is a conical surface. That is, the cross-sectional shapes obtained by cutting the first reflecting surface 40B and the second reflecting surface 41B along a plane parallel to the Z-axis az are both linear.
- the parameters representing the shapes of the first reflecting surface 40B and the second reflecting surface 41B are set to the values shown in FIG. Also, the above d1 is set to the value shown in FIG.
- FIG. 14 is a simulation image representing the cross-sectional shape of the scanning light Ls at a location about 1 m away from the optical system 12.
- FIG. The image shown in FIG. 20 has a vertical direction parallel to the Z-axis direction and a horizontal direction parallel to a direction orthogonal to the Z-axis direction.
- the cross-sectional shapes of the first reflecting surface 40B and the second reflecting surface 41B are linear, the beam diameter spreads.
- the dependency on the deflection angle ⁇ is large, and the spread of the beam diameter in the horizontal direction increases when the deflection angle ⁇ is small.
- the cross-sectional shape of the first reflecting surface 40B is concave, and the cross-sectional shape of the second reflecting surface 41B is convex, thereby suppressing the spread of the beam diameter.
- the first reflecting surface of the first reflecting member is a hyperboloid or paraboloid
- the second reflecting surface of the second reflecting member is a hyperboloid, paraboloid, or ellipsoid.
- one or both of the first reflecting surface and the second reflecting surface have an odd-order aspherical surface.
- An odd-order aspherical surface means a curved surface expressed including an odd-order aspherical surface coefficient as in the above equation (1).
- the direction of incidence of the laser light L on the movable mirror 20 is the Z-axis direction, but the direction of incidence of the laser light L is not limited to the Z-axis direction. (For example, a direction perpendicular to the Z-axis direction).
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Abstract
Description
図1は、一実施形態に係るLiDAR装置2の概略構成を示す。LiDAR装置2は、対象物3に対して走査光Lsを出射し、その戻り光Lrを受光して対象物3までの距離を計測する。LiDAR装置2は、例えば自動車に搭載され、周辺障害物の距離情報を取得する。LiDAR装置2は、本開示の技術に係る「光走査装置」の一例である。
上記第1実施形態では、第1反射面40B及び第2反射面41Bをともに双曲面としているが、本実施形態では、第1反射面40Bを双曲面とし、第2反射面41Bを放物面とする。第1反射面40B及び第2反射面41Bの形状を表すパラメータは、図10に示す値に設定されている。また、上述のd1及びd2は、図10に示す値に設定されている。
第3実施形態では、第1反射部材40としてマンギンミラーと呼ばれる裏面型凹面ミラーを用いる。第3実施形態に係る光学系12の構成は、第1反射部材40を裏面型凹面ミラーとすること以外は、第1実施形態に係る光学系12と同様である。
上記各実施形態では、可動ミラー20の振れ角θを固定しているが、可動ミラー20を歳差運動させている間に振れ角θを偏向することにより、走査光Lsを、Z軸回りの周方向に走査するとともに、Z軸方向に走査(垂直走査)することも可能である。図15に示すように、本実施形態では、光学系12から出射される走査光Lsが、YZ面に対して+15°をなす方向と、YZ面に対して-15°をなす方向との間で、走査光LsをZ軸方向に走査する。
次に、比較例について説明する。図18は、比較例に係る光学系12の構成を示す。本比較例では、第1反射面40Bは平面であり、第2反射面41Bは円錐面である。すなわち、第1反射面40B及び第2反射面41BをZ軸azに平行な面で切断した断面形状は、いずれも直線状である。本比較例では、第1反射面40B及び第2反射面41Bの形状を表すパラメータは、図19に示す値に設定されている。また、上述のd1は、図19に示す値に設定されている。
Claims (11)
- 可動ミラーによって偏向された偏向光が入射する光学系であって、
第1軸に対して回転対称であって、前記偏向光を反射して第1反射光として出射する第1反射面を有する第1反射部材と、
前記第1軸に対して回転対称であって、前記第1反射光を反射して第2反射光として出射する第2反射面を有する第2反射部材と、を備え、
前記第1反射面を前記第1軸に平行な面で切断した断面形状は凹状であり、
前記第2反射面を前記第1軸に平行な面で切断した断面形状は凸状であり、
前記第1反射光の光路は、前記第1軸と平行であり、
前記第2反射光の光路は、前記第1軸から外側に向かう方向である、
光学系。 - 前記可動ミラーは、法線方向が前記第1軸に対して一定の角度範囲で傾斜した状態で回動する、
請求項1に記載の光学系。 - 前記偏向光は平行光であって、
前記第1反射光の集光位置と、前記第2反射光の光路から前記第2反射面に仮想的に平行光を入射させた場合において前記第2反射面により反射された反射光の虚像の集光位置とが一致する、
請求項1又は請求項2に記載の光学系。 - 前記第1反射面から前記第1反射光の集光位置までの距離をf1、前記第2反射面から前記虚像の集光位置までの距離をf2、前記第1反射面と前記第2反射面との前記第1軸への距離をdとした場合に、
0.9×d≦f1-f2≦1.1×dの範囲内である、
請求項3に記載の光学系。 - 前記第1反射面と前記第2反射面とのうちいずれか一方の形状は、双曲面である、
請求項1から請求項4のうちいずれか1項に記載の光学系。 - 前記第1反射面と前記第2反射面とのうちいずれか一方の形状は、奇数次非球面である、
請求項1から請求項5のうちいずれか1項に記載の光学系。 - 前記第1軸に対して回転対称であって前記第2反射部材より外側に配置され、前記第2反射光を屈折させるプリズムを備える、
請求項1から請求項6のうちいずれか1項に記載の光学系。 - 前記プリズムを前記第1軸に平行な面で切断した断面形状は三角形である、
請求項7に記載の光学系。 - 請求項1から請求項8のうちいずれか1項に記載の光学系と、
前記可動ミラーを有する可動ミラー装置と、
前記可動ミラーに入射させる光を発する光源と、
を備える光走査装置。 - 前記可動ミラーには、前記第1軸に沿って前記光が入射する、
請求項9に記載の光走査装置。 - 前記第2反射光を走査光として、前記第1軸周りの全方位に向けて出射する
請求項9又は請求項10に記載の光走査装置。
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