TWI744209B - Optical radar with coaxial optical path - Google Patents

Abstract

An optical radar with a coaxial optical path includes a light emitting unit for emitting light beams, a reflecting mirror for reflecting light beams, a photosensitive element for receiving light beams, a wave plate for delaying passing light beams, and a beam splitter. The light emitting unit, the beam splitter, the wave plate and the reflecting mirror are arranged along a first optical axis direction. In this way, the polarization direction of the light beam is converted by the wave plate, and the special design of the beam splitter that only allows the beam of a specific polarization direction to pass through is used, so that when the light beam travels from the light-emitting unit to an object along a forward path, it directly passes through the beam splitter , And when the beam travels along a return path from the object, it is reflected by the beam splitter and travels toward the photosensitive element, which improves the utilization and collimation of the beam without damaging the integrity of the element and the beam is fully utilized. Degree and power.

Description

Optical radar with coaxial optical path

The invention relates to an optical radar, in particular to an optical radar with a coaxial optical path.

Lidar, the full English name is Light Detection And Ranging, mainly uses light to measure the distance of the target, and is widely used in industrial manufacturing, transportation systems or logistics, and the application of vehicle assisted driving is gradually popular Later, it was even more valued.

If it is distinguished by the photosensitive structure of the detection beam, it can be divided into two types: area detection and single-point detection. The former is more expensive, so the latter is more mainstream. The single-point detection is divided into two types: non-coaxial optical path and coaxial optical path. Among them, a coaxial optical path published by JARI Research Magazine on September 1, 2016 is a coaxial optical path, as shown in Figure 1. It includes a laser diode 11 that emits a light beam along an optical axis X direction, a mirror 12 that is spaced from the laser diode 11 along the optical axis X direction and can rotate 360 degrees, and a mirror 12 arranged on the laser The hollow mirror 13 between the diode 11 and the reflecting mirror 12, a collimating lens 14 arranged between the hollow mirror 13 and the laser diode 11, is arranged in the direction perpendicular to the optical axis X A photosensitive element 15 on one side of the hollow mirror 13 and used for receiving light beams, and a focusing lens 16 arranged between the photosensitive element 15 and the hollow mirror 13 and used for converging the light beams. The hollow mirror 13 is divided into a solid part 131 and a hollow part 132.

Thereby, when the light beam emitted in a pulsed manner passes through the hollow portion 132 of the hollow mirror 13 along the optical axis X direction, and is reflected by the 360-rotating mirror 12, and scans around the optical axis X as the center, the light beam After hitting an object 2, it bounces and is again reflected by the mirror 12, and after traveling along the optical axis X direction to the physical portion 131 of the central control mirror 13, it is reflected by the hollow mirror 13 to the photosensitive element 15.

However, although this method can make the light beam go back and forth along the same optical axis X, it has the following disadvantages:

1. In the case that the hollow portion 132 of the hollow mirror 13 cannot be used to reflect the light beam, only part of the returning light beam can be collected by the photosensitive element 15, and the rest will pass directly through the hollow portion 132 without being used. Not only waste, but also power loss.

2. The diameter of the beam will determine the collimation and range of the beam. Therefore, in a limited space, if the hollow portion 132 is enlarged to increase the diameter of the beam, the area where the solid portion 131 can reflect the beam is only If the area of the solid part 131 is enlarged, the size of the hollow part 132 will be reduced. In the case where the diameter of the beam is limited by the size of the hollow part 132, There are shortcomings of beam collimation and range not as expected.

Therefore, the object of the present invention is to provide a coaxial optical radar capable of improving the utilization, collimation and power of the beam.

Therefore, the optical radar with the coaxial optical path of the present invention is used to transmit and receive light beams so that the light beams travel in opposite directions on a forward and a return journey, and includes a light-emitting unit, a photosensitive element, a mirror, a wave plate, and A beam splitter.

The light-emitting unit is used to emit light beams.

The reflecting mirror is spaced from the light emitting unit along a first optical axis direction, and is used for reflecting the light beam.

The photosensitive element is used to receive the light beam.

The wave plate is arranged between the light-emitting unit and the reflector along the first optical axis direction, and is used to delay the passing light beam so that the light beam passes through the wave plate for the first time on the outgoing path, compared to not passing through the wave plate. The light beam of the wave plate produces a phase difference of 1/4 wavelength, and passes through the wave plate for the second time on the return journey, and produces a phase difference of 1/2 wavelength compared to the light beam that does not pass through the wave plate.

The beam splitter is arranged between the light emitting unit and the wave plate along the direction of the first optical axis, for the forward beam to pass through, and to reflect the return beam.

The effect of the present invention is that the wave plate is used to convert the polarization direction of the light beam, and the beam splitter is designed to allow only light beams with a specific polarization direction to pass through, so that the light beam passes directly through the light-emitting unit along a forward path toward an object. The beam splitter is reflected by the beam splitter when the beam travels along a return path from the object and travels toward the photosensitive element. This improves the utilization rate of the beam without damaging the integrity of the element and the beam is fully utilized. , Collimation and power.

Referring to FIGS. 2, 3 and 4, an embodiment of an optical radar 3 (LiDAR) with a coaxial optical path of the present invention is installed in a vehicle 4 for detecting the distance between the vehicle 4 and an object 5. The optical radar 3 is used to transmit and receive light beams so that the light beams travel along a forward path L1 and a return path L2 in opposite directions, and includes a light emitting unit 31, a reflector 32, a wave plate 33, a beam splitter 34, and a The photosensitive element 35, a collimating lens 36, and a focusing lens 37.

The light-emitting unit 31 is fixed at a fixed point and includes a light-emitting element 311 for emitting light beams. In this embodiment, the light-emitting element 311 is a laser diode (LD) for emitting a P-polarized light beam. It should be noted that the number of the light-emitting element 311 is not limited to one, and in other variations of this embodiment, it may also be two or more.

In addition, it is worth noting that the polarization direction of the P-polarized beam is shown by the solid line arrow in Figure 3, parallel to the plane of the drawing, while the polarization direction of the S-polarized beam is shown by the symbol ☉ in Figure 4, which is perpendicular to the plane of the drawing. .

The reflecting mirror 32 is spaced from the light-emitting unit 31 along a first optical axis X direction, and is used for reflecting light beams. In this embodiment, the reflecting mirror 32 can be driven to rotate around the first optical axis X, so that the reflected light beam diverges to four directions with the first optical axis X as the center.

In this embodiment, the wave plate 33 is a quarter-wave plate (Quarter-wave plate), which is arranged between the light-emitting unit 31 and the mirror 32 along the first optical axis X direction, and is used to delay passing The light beam makes the passing beam produce a phase difference of 1/4 wavelength.

In this embodiment, the beam splitter 34 is a Polarization Beam Splitter (PBS), which is arranged between the light emitting unit 31 and the wave plate 33 along the X direction of the first optical axis, and only serves for P-polarized beams. Passes and reflects the S-polarized beam.

In this embodiment, the photosensitive element 35 is a single-point sensor fixed at a fixed point, and is spaced from the beam splitter 34 along a second optical axis Y direction for receiving light beams. The second optical axis Y is substantially perpendicular to the first optical axis X.

The collimating lens 36 is arranged between the beam splitter 34 and the light emitting unit 31 along the first optical axis X direction, and is used to converge and collimate the light beam of the forward path L1.

The focusing lens 37 is arranged between the beam splitter 34 and the photosensitive element 35 along the direction of the first optical axis X, and is used for condensing the light beam of the return path L2.

2 and 3, when the light-emitting unit 31 uses the flight time of the laser pulse to emit a P-polarized light beam, the light beam will sequentially pass through the first optical axis X in the process of traveling along the forward path L1. The collimator lens 36, the beam splitter 34, and the wave plate 33 travel to the mirror 32, whereby the light beam will be reflected by the 360-rotating mirror 12 and scan the surroundings with the optical axis X as the center.

It is worth noting that when the P-polarized light beam is emitted by the light-emitting unit 31 and passes through the collimating lens 36, the light beam will be converged and collimated to travel along the first optical axis X direction. In addition, since the beam splitter 34 only passes through the P-polarized beam, the P-polarized beam passing through the collimating lens 36 will pass through the beam splitter 34 completely and smoothly without interference from foreign objects and the beam diameter is not reduced. After passing through the wave plate 33 for the first time, a phase difference of 1/4 wavelength is generated and converted into a circularly polarized light beam. March.

2 and 4, when the circularly polarized light beam emitted from the reflector 32 hits the object 5, the reflected circularly polarized light beam will follow the original optical path, that is, the return path L2 and travel to the reflector 32, and be After the mirror 32 is completely reflected, it passes through the wave plate 33 for the second time and again produces a phase difference of 1/4 wavelength. Because the light beam produces a phase difference of 1/4 wavelength between the forward path L1 and the return path L2, respectively, Compared with the light beam that does not pass through the wave plate 33, a phase difference of 1/4 wavelength + 1/4 wavelength = 1/2 wavelength is generated, and the circularly polarized light beam is converted into an S-polarized light beam. The S-polarized light beam that travels to the beam splitter 34 in the direction of axis X cannot pass through the beam splitter 34, and is completely reflected to the focusing lens 37 without reducing the beam diameter, and along the second optical axis Y The direction is focused to the photosensitive element 35 to achieve the purpose of collecting light.

Based on the above description, the advantages of the foregoing embodiments can be summarized as follows:

1. With the special design of the wave plate 33 and the beam splitter 34 in the present invention, the beam can be fully utilized regardless of the forward path L1 or the return path L2, and the beam can be improved without reducing the beam diameter. The degree of collimation and light utilization.

2. The present invention only uses one reflector 32, and the reflector 32 does not require additional processing holes. Therefore, the light beam reflected back along the return path L2 can be completely collected by the photosensitive element 35, and the power can be greatly increased.

However, the above are only examples of the present invention. When the scope of implementation of the present invention cannot be limited by this, all simple equivalent changes and modifications made in accordance with the scope of the patent application of the present invention and the content of the patent specification still belong to This invention patent covers the scope.

3: Optical radar 31: Light-emitting unit 311: Light-emitting element 32: mirror 33: wave plate 34: Spectroscope 35: photosensitive element 36: collimating lens 37: Focusing lens 4: Vehicle 5: Object X: first optical axis Y: second optical axis L1: Outbound L2: Return

Other features and effects of the present invention will be clearly presented in the embodiments with reference to the drawings, in which: Figure 1 is a schematic diagram illustrating a conventional LiDAR; Figure 2 is a perspective view illustrating an embodiment of the present invention where the optical radar of the coaxial optical path is installed in a self-driving car; Figure 3 is a schematic diagram illustrating that the light beam generated by this embodiment travels along a forward path; and Fig. 4 is a schematic diagram illustrating that the light beam generated by this embodiment travels along a return path.

31: Light-emitting unit

311: Light-emitting element

32: mirror

33: wave plate

34: Spectroscope

35: photosensitive element

36: collimating lens

37: Focusing lens

5: Object

X: first optical axis

Y: second optical axis

L2: Return

Claims (9)

An optical radar with a coaxial optical path, used to transmit and receive light beams so that the light beams travel in opposite directions on a forward and a return journey, and includes: A light-emitting unit for emitting light beams; A reflecting mirror, spaced apart from the light-emitting unit along a first optical axis direction, and used for reflecting the light beam; A photosensitive element for receiving light beams; A wave plate is arranged between the light emitting unit and the reflector along the first optical axis direction, and is used to delay the passing light beam so that the light beam passes through the wave plate for the first time in the outgoing journey, compared to the non-passing light beam. The light beam of the wave plate produces a phase difference of 1/4 wavelength, and passes through the wave plate for the second time on the return journey, and produces a phase difference of 1/2 wavelength compared to the light beam that does not pass through the wave plate; and A beam splitter is arranged between the light-emitting unit and the wave plate along the direction of the first optical axis, for the forward beam to pass through, and to reflect the return beam. The optical radar of the coaxial optical path according to claim 1, wherein the light beam traveling along the forward path and not passing through the wave plate is a P-polarized light beam, and the wave plate is a quarter-wave plate (Quarter-wave plate), Used to convert the light beam that passes through the wave plate for the second time into an S-polarized light beam. The optical radar with a coaxial optical path according to claim 2, wherein the beam splitter is a Polarization Beam Splitter (PBS), which only passes P-polarized light beams and reflects S-polarized light beams. In the optical radar with a coaxial optical path according to claim 1, the photosensitive element is spaced from the beam splitter along a second optical axis direction, and the second optical axis direction is substantially perpendicular to the first optical axis. The optical radar with a coaxial optical path according to claim 1, wherein the reflector can be driven to rotate around the first optical axis, and the light-emitting unit and the photosensitive element are fixed at a fixed point. The optical radar with a coaxial optical path according to claim 1, further comprising a collimating lens arranged between the beam splitter and the light-emitting unit along the direction of the first optical axis for converging and collimating the defocusing lens. Cheng's beam. The optical radar with a coaxial optical path according to claim 1, further comprising a focusing lens arranged between the beam splitter and the photosensitive element along the direction of the first optical axis, for concentrating the returning light beam. The optical radar with a coaxial optical path according to claim 1, wherein the light-emitting unit includes at least one light-emitting element. The optical radar with a coaxial optical path according to claim 8, wherein the at least one light-emitting element is a laser diode (LD).

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