A laser radar using a liquid crystal device as a beam deflection device

Abstract

The present invention discloses a laser radar (LIDAR) using a liquid crystal device as a beam deflection device. The device comprises a first angle deflection system, comprising a first deflection unit and at least one second deflection unit. The first deflection unit deflects incident light to produce deflected light. The second deflection unit comprises a second polarization grating and at least one second liquid crystal phase retarder, which delays the deflected light to a total delay equal to that of a half-wave plate. The second polarization grating further deflects the deflected light. The use of the liquid crystal phase retarder and polarization grating in a LIDAR system enables high-efficiency operation, high reliability, good stability, and low cost, enabling large-scale commercialization.

Description

Technical Field

[0001] The present invention relates to the technical field of laser radar, and in particular to a laser radar using a liquid crystal device as a beam deflection device. Background Art

[0002] LiDAR (LiDAR) is a system that uses laser beams to detect target characteristics such as position and velocity. It is widely used in the field of laser detection. To accommodate two-dimensional or three-dimensional detection, the laser beam emitted by LiDAR must be rotated. Optical phased array components are typically used to control the laser beam's wavefront phase, thereby controlling the direction of the emitted beam. Advances in liquid crystal display technology have led to the use of liquid crystal devices as optical phased array components. However, this approach has drawbacks such as high etching precision for the liquid crystal substrate electrodes and low diffraction efficiency. Summary of the Invention

[0003] The technical problem to be solved by the present invention is: the problem of low diffraction efficiency when using liquid crystal devices as optical phase-controlled elements.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a laser radar using a liquid crystal device as a beam deflection device includes a first angle deflection system, wherein the first deflection system includes a first deflection unit and at least one second deflection unit;

[0005] The first deflection unit deflects the incident light to obtain deflected light;

[0006] The second deflection unit includes a second polarization grating and at least one second liquid crystal phase retarder. The at least one second liquid crystal phase retarder is used to delay the deflected light so that the total delay amount of the liquid crystal device reaches that of a half-wave plate. The second polarization grating is used to deflect the deflected light again.

[0007] Furthermore, the first deflection unit includes a first liquid crystal phase retarder and a first polarization grating. The first liquid crystal phase retarder is used to delay the incident light, and its phase delay amount is a quarter-wave plate, so that the incident linearly polarized light is converted into circularly polarized light or maintains linear polarization. The first polarization grating can deflect the incident light by an angle θ, where θ is greater than or equal to 0.

[0008] Furthermore, there are multiple second deflection units, which are arranged in a row, and each deflection unit deflects or does not deflect the angle of the light.

[0009] Furthermore, it includes a second deflection system, which is located at the rear end of the first deflection system and is used to adjust the deflected light of the first deflection system to a maximum deflection angle.

[0010] Furthermore, the second deflection system includes at least one third deflection unit, which includes at least one third liquid crystal phase retarder and at least two third polarization gratings. The at least two third polarization gratings can deflect the deflected light by 2*θ, where θ is greater than or equal to 0. The at least one third liquid crystal phase retarder is used to delay the deflected light so that the total delay amount of the deflected light reaches that of a half-wave plate.

[0011] Furthermore, there are multiple third deflection units, which are arranged in a row, and each deflection unit deflects or does not deflect the angle of the light.

[0012] Furthermore, it further includes a first anti-reflection layer and a second anti-reflection layer, wherein the first anti-reflection layer is located at the front end of the first deflection system, and the second anti-reflection layer is located at the rear end of the second deflection system.

[0013] Furthermore, it includes a first heating layer and a second heating layer, wherein the first heating layer is located between the first anti-reflection layer and the first deflection system, and the second heating layer is located between the second anti-reflection layer and the second deflection system.

[0014] Furthermore, it also includes at least a third heating layer, and the third heating layer is located between the first deflection unit and the second deflection unit, or between the second deflection unit and the third deflection unit.

[0015] Furthermore, the first deflection system and the second deflection system operate in an infrared band of 800-1100 nm.

[0016] The beneficial effects of the present invention are: applying the liquid crystal phase retarder and the polarization grating to the laser radar system enables the system to operate efficiently, with high reliability, good stability, low cost, and large-scale commercialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The specific structure of the present invention is described in detail below with reference to the accompanying drawings

[0018] Figure 1 This is a partial structural diagram of a laser radar that uses liquid crystal devices for light beam deflection according to the present invention.

[0019] Figure 2 This is a component indication diagram of a laser radar that uses liquid crystal devices for beam deflection according to the present invention.

[0020] The labels are as follows:

[0021] 1-first liquid crystal phase retarder / second liquid crystal phase retarder / third liquid crystal phase retarder; 2-first polarization grating / second polarization grating / third polarization grating; 10-first anti-reflection layer; 20-first heating layer; 30-second heating layer; 40-second anti-reflection layer; 50-first deflection system; 60-second deflection system. DETAILED DESCRIPTION

[0022] In order to explain the technical content, structural features, achieved objectives and effects of the present invention in detail, the following is a detailed description in conjunction with the embodiments and the accompanying drawings.

[0023] See also Figure 1 and Figure 2 , a laser radar using a liquid crystal device as a beam deflection device, comprising a first angle deflection system 50, wherein the first deflection system 50 comprises a first deflection unit and at least one second deflection unit;

[0024] The first deflection unit deflects the incident light to obtain deflected light;

[0025] The second deflection unit includes a second polarization grating 2 and at least one second liquid crystal phase retarder 1. The at least one second liquid crystal phase retarder 1 is used to delay the deflected light so that the total delay amount of the liquid crystal device reaches that of a half-wave plate. The second polarization grating 2 is used to deflect the deflected light again.

[0026] Therefore, the function of the first deflection unit is to convert incident linearly polarized light into circularly polarized light and deflect it. When the incident light is linearly polarized, it passes through the AR layer, the heating layer, and then the first liquid crystal phase retarder in A0. When the liquid crystal device operates in the quarter-wave plate mode, the linearly polarized light becomes left (right) circularly polarized light after passing through the liquid crystal device. After passing through the polarization grating, the left (right) circularly polarized light is deflected upward (downward) by an angle θ, and the left (right) circularly polarized light becomes right (left) circularly polarized light. When one or more liquid crystal devices in A1 operate in a coordinated manner with a total retardation of half a wave plate, right (left) circularly polarized light becomes left (right) circularly polarized light after passing through the two liquid crystal devices. After passing through the polarization grating, the left (right) circularly polarized light is deflected upward (downward) by an angle θ. When the liquid crystal devices of n subsystems Ai in deflection system A operate in a coordinated manner with a total retardation of half a wave plate, the angle deflection is n*θ.

[0027] Example 1

[0028] The first deflection unit includes a first liquid crystal phase retarder 1 and a first polarization grating 2. The first liquid crystal phase retarder is used to delay the incident light. Its phase delay amount is a quarter-wave plate, so that the incident linearly polarized light is converted into circularly polarized light or maintains linear polarization. The first polarization grating can deflect the incident light by an angle θ, where θ is greater than or equal to 0.

[0029] As a result, the first liquid crystal retarder 1 functions as a quarter-wave plate, converting linearly polarized light into circularly polarized light, while maintaining its polarization state when a high voltage is applied. The polarization grating 2 achieves the following functions: When the incident light is linearly polarized, the angle and polarization state of the light remain unchanged. When the incident light is circularly polarized, it is deflected to the right or left by an angle θ after passing through the polarization grating. Furthermore, when passing through the same grating, left-handed and right-handed circularly polarized light are deflected in opposite directions.

[0030] Example 2

[0031] There are multiple second deflection units, which are arranged in a row. Each deflection unit deflects or does not deflect the angle of the light.

[0032] Thus, the total retardation of one or two or more liquid crystal phase retarders 1 achieves the function of a half-wave plate, capable of converting left-handed (right-handed) circularly polarized light into right-handed (left-handed) circularly polarized light, or converting circularly (linearly) polarized light into linearly (circularly) polarized light when a high voltage is applied to one of them, or maintaining the polarization state of the light when voltages are applied simultaneously. A combination of i systems can achieve angular deflection from 0° to i*θ (i=1, 2, 3, ...).

[0033] Example 3

[0034] The second deflection system 60 is included. The second deflection system 60 is located at the rear end of the first deflection system 50. The second deflection system 60 is used to adjust the deflected light of the first deflection system 50 to a maximum deflection angle.

[0035] Thus, the second deflection system 60 can deflect the incident light by 2*i*θ (θ is the angle that a single deflection grating can deflect, with i = 0, 1, 2, etc., depending on the number of subsystems Bi). If the polarization state of the light before reaching the second deflection system 60 is circularly polarized, and when the liquid crystal device in B1 is operating at a high voltage, the polarization state of the light does not change after passing through the liquid crystal device and remains circularly polarized. After passing through the two polarization gratings, the light is deflected by 2*θ. If the liquid crystal devices of m subsystems in the second deflection system operate at a high voltage (without changing the polarization state of the incident light), the deflection angle is 2*m*θ.

[0036] The deflection angle capability of this system is n*θ+2*m*θ. The number of Ai systems in the first deflection system 50 and the number of Bi systems in the second deflection system 60 determine the maximum deflection angle and polarization accuracy of the entire system. By controlling the operating state of the liquid crystal device, angular deflection within the maximum deflection angle range can be achieved.

[0037] Example 4

[0038] The second deflection system 60 includes at least one third deflection unit, which includes at least one third liquid crystal phase retarder 1 and at least two third polarization gratings 2. The at least two third polarization gratings 2 can deflect the deflected light by 2*θ, where θ is greater than or equal to 0. The at least one third liquid crystal phase retarder 1 is used to delay the deflected light so that the total delay amount of the deflected light reaches that of a quarter wave plate.

[0039] This allows circularly polarized light to be converted into linearly polarized light, and the polarization state of the light does not change when a high voltage is applied. The polarization grating 2 serves to deflect the angle.

[0040] Example 5

[0041] There are multiple third deflection units, which are arranged in a row. Each deflection unit deflects or does not deflect the angle of the light.

[0042] Therefore, the number of third deflection units can be increased or decreased based on actual requirements. The liquid crystal device is electrically controlled. When powered, the liquid crystal molecules deflect. When the liquid crystal molecules are perpendicular to the substrate, the retardation of the liquid crystal device approaches zero, meaning there is no phase delay on the incident light, and the polarization direction of the incident light remains unchanged. When powered off, the retardation of the liquid crystal device is that of a half-wave plate, causing a phase delay on the incident light. For example, incident left-circularly polarized light passes through the liquid crystal device as right-circularly polarized light.

[0043] Example 6

[0044] The optical fiber optic cable further includes a first anti-reflection layer 10 and a second anti-reflection layer 40 . The first anti-reflection layer 10 is located at the front end of the first deflection yoke 50 , and the second anti-reflection layer 40 is located at the rear end of the second deflection yoke 60 .

[0045] Therefore, the anti-reflection layer (AR) is used to reduce the reflection of light and increase the transmittance of the entire system.

[0046] Example 7

[0047] The optical fiber optical fiber system further includes a first heating layer 20 and a second heating layer 30. The first heating layer 20 is located between the first anti-reflection layer 10 and the first deflection system 50, and the second heating layer 30 is located between the second anti-reflection layer 40 and the second deflection system 60. The optical fiber system further includes at least one third heating layer, which is located between the first deflection unit and the second deflection unit, or between the second deflection unit and the third deflection unit.

[0048] This allows the heating layer to operate even when the ambient temperature is low, allowing the entire LiDAR system, which uses liquid crystal devices as beam deflectors, to function properly even in low-temperature conditions. The location and number of the heating layers can be adjusted based on actual needs.

[0049] Example 8

[0050] The first deflection system 50 and the second deflection system 60 operate in the infrared band of 800-1100 nm.

[0051] Thus, the first deflection system 50 and the second deflection system 60 can be used in combination to achieve continuous scanning of angles. The first deflection system 50 and the second deflection system 60 operate in this infrared band and are not easily interfered by visible light in outdoor environments.

[0052] Here, first, second... only represent the distinction in their names, and do not represent any difference in their importance and position.

[0053] Here, up, down, left, right, front, and back only represent their relative positions and do not represent their absolute positions.

[0054] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention's description and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A laser radar using a liquid crystal device as a beam deflection device, characterized in that: The invention comprises a first deflection system and a second deflection system, wherein the first deflection system comprises a first deflection unit and at least one second deflection unit, and the second deflection system is located at the rear end of the first deflection system, and is used to adjust the deflected light of the first deflection system to a maximum deflection angle; The first deflection unit deflects the incident light to obtain deflected light; The second deflection unit includes a second polarization grating and at least one second liquid crystal phase retarder, the at least one second liquid crystal phase retarder is used to delay the deflected light so that the total delay of the liquid crystal device reaches that of a half-wave plate, and the second polarization grating is used to deflect the deflected light again; The second deflection system includes at least one third deflection unit, which includes at least one third liquid crystal phase retarder and at least two third polarization gratings. The at least two third polarization gratings can deflect the deflected light by 2*θ, where θ is greater than or equal to 0. The at least one third liquid crystal phase retarder is used to delay the deflected light so that the total delay amount of the deflected light reaches that of a quarter wave plate.

2. The laser radar using a liquid crystal device as a beam deflection device as claimed in claim 1, characterized in that: The first deflection unit includes a first liquid crystal phase retarder and a first polarization grating. The first liquid crystal phase retarder is used to delay the incident light. Its phase delay amount is a quarter-wave plate, so that the incident linearly polarized light is converted into circularly polarized light or maintains linear polarization. The first polarization grating can deflect the incident light by an angle θ, where θ is greater than or equal to 0.

3. The laser radar using a liquid crystal device as a beam deflection device as claimed in claim 1, characterized in that: There are multiple second deflection units, which are arranged in a row. Each deflection unit deflects or does not deflect the angle of the light.

4. The laser radar using a liquid crystal device as a beam deflection device as claimed in claim 1, characterized in that: There are multiple third deflection units, which are arranged in a row. Each deflection unit deflects or does not deflect the angle of the light.

5. The laser radar using a liquid crystal device as a beam deflection device as claimed in claim 1, characterized in that: The invention also includes a first anti-reflection layer and a second anti-reflection layer. The first anti-reflection layer is located at the front end of the first deflection system, and the second anti-reflection layer is located at the rear end of the second deflection system.

6. The laser radar using a liquid crystal device as a beam deflection device as claimed in claim 5, characterized in that: It also includes a first heating layer and a second heating layer, wherein the first heating layer is located between the first anti-reflection layer and the first deflection system, and the second heating layer is located between the second anti-reflection layer and the second deflection system.

7. The laser radar using a liquid crystal device as a beam deflection device as claimed in claim 1, characterized in that: The invention further comprises at least a third heating layer, wherein the third heating layer is located between the first deflection unit and the second deflection unit, or between the second deflection unit and the third deflection unit.

8. The laser radar using a liquid crystal device as a beam deflection device as claimed in claim 1, characterized in that: The first deflection system and the second deflection system operate in the infrared band of 800-1100 nm.

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