Adaptive laser radar system based on phase modulation unit

Abstract

The utility model discloses a self-adaptive laser radar system based on a phase modulation unit, and the key points of the technical scheme are that the self-adaptive laser radar system comprises a housing, and one end of the housing is connected with an optical fiber; the auxiliary lens is arranged at the position, close to the optical fiber, in the shell; the main lens is arranged at one end, far away from the optical fiber, in the shell and consists of at least one lens; the auxiliary lens comprises a phase modulation device, the phase modulation device is arranged in the shell, continuous zooming of the phase modulation device is achieved through an electric control system, and the phase modulation device is arranged at the auxiliary lens to serve as a lens forming the auxiliary lens; the electric control system can control the phase modulation device to carry out continuous zooming, errors are reduced, and convenience of focal length adjustment is improved.

Description

Technical Field

[0001] This utility model relates to the technical field of lidar, and more specifically, to an adaptive lidar system based on a phase modulation unit. Background Technology

[0002] Existing coherent wind lidar telescope systems, based on the coaxial transmitter-receiver principle, use a pulsed laser beam expanded by the telescope system to measure the backscattered waves of aerosol particles. Because the echo signal is very weak, the telescope design needs to minimize aberrations and maximize efficiency to improve the system's signal-to-noise ratio (SNR). During testing, we typically adjust the telescope's focal length to maximize the radar's measurement range and thus the system's SNR, measuring wind speed within this parameter. However, current wind lidar focusing relies on mechanical adjustment, changing the focal length by moving the lens, which introduces significant errors. Utility Model Content

[0003] In view of the shortcomings of the existing technology, the purpose of this utility model is to provide an adaptive lidar system based on a phase modulation unit, which can control the phase modulation device to perform continuous zoom through an electronic control system, thereby reducing errors and improving the convenience of focal length adjustment.

[0004] To achieve the above objectives, the present invention provides the following technical solution: an adaptive lidar system based on a phase modulation unit, comprising a housing, one end of which is connected to an optical fiber;

[0005] A secondary lens, wherein the secondary lens is disposed inside the housing near the optical fiber;

[0006] And a main lens, which is disposed inside the housing at the end away from the optical fiber and consists of at least one lens;

[0007] The secondary lens includes a phase modulation device, which is disposed within the housing. The phase modulation device achieves continuous zoom through an electronic control system. The phase modulation device is located at the secondary lens to serve as a lens that constitutes the secondary lens.

[0008] The present invention is further configured such that the phase modulation device is a spatial light modulator or a liquid crystal lens.

[0009] The present invention is further configured such that the phase modulation device is a liquid crystal lens;

[0010] The liquid crystal lens includes a first substrate;

[0011] Second substrate;

[0012] A liquid crystal molecule layer is disposed between a first substrate and a second substrate;

[0013] Electrodes are provided on the side of the first substrate and the second substrate closest to the liquid crystal molecular layer.

[0014] The present invention is further configured such that the electrode is a concentric ring electrode, a continuous gradient electrode, or a segmented electrode, so that the refractive index distribution of the liquid crystal lens simulates the optical characteristics of a concave mirror.

[0015] The present invention is further configured such that the electrodes are concentric ring electrodes, each ring is connected to an independent voltage source, and the voltage value gradually increases from the center to the edge.

[0016] The present invention is further configured such that: the motor is configured as a continuous gradient electrode, and the continuous gradient electrode causes the voltage to gradually increase from the center to the edge of the liquid crystal lens through resistive voltage division.

[0017] In summary, compared with the prior art, the present invention has the following advantages: the present invention can control the phase modulation device to perform continuous zoom through the electronic control system, which reduces errors and improves the convenience of focal length adjustment. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the embodiment;

[0019] Figure 2 This is a schematic diagram illustrating plano-convex and concave-convex lenses in an embodiment;

[0020] Figure 3 This is a schematic diagram illustrating the structure of a liquid crystal lens in an embodiment.

[0021] In the diagram: 1. Housing; 2. Optical fiber; 3. Main lens; 31. Plano-convex lens; 32. Concave-convex lens; 4. Secondary lens; 5. Phase modulation device; 51. First substrate; 52. Second substrate; 53. Electrode; 54. Spacer layer; 6. Electrical control system. Detailed Implementation

[0022] To enable those skilled in the art to better understand the technical solution of this utility model, the technical solution of this utility model will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments in this application, other similar embodiments obtained by those skilled in the art without creative effort should all fall within the scope of protection of this application. Furthermore, the directional terms mentioned in the following embodiments, such as "up," "down," "left," and "right," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for illustrative purposes and not for limiting the creation of this utility model.

[0023] The present invention will be further described below with reference to the accompanying drawings and preferred embodiments.

[0024] Example: An adaptive lidar system based on a phase modulation unit, see appendix. Figure 1 - Appendix Figure 3 The system includes a housing 1, a secondary lens 4, and a primary lens 3. One end of the housing 1 is connected to an optical fiber 2. The secondary lens 4 is located inside the housing 1 near the optical fiber 2. The primary lens 3 is located inside the housing 1 at the end away from the optical fiber 2 and consists of at least one lens. The secondary lens 4 includes a phase modulation device 5, which is located inside the housing 1. The phase modulation device 5 achieves continuous zoom through an electronic control system 6. The phase modulation device 5 is located at the secondary lens 4 to serve as a lens that constitutes the secondary lens 4.

[0025] When focusing the lidar system, the phase modulation device 5 can be continuously zoomed by the electronic control system 6 to achieve focusing. Focusing by the electronic control system 6 improves the focusing accuracy and eliminates the need for mechanical operation, thus improving the convenience of operation.

[0026] Specifically, the phase modulation device 5 is configured as a spatial light modulator or a liquid crystal lens. A spatial light modulator manipulates the light field distribution by modulating the phase, amplitude, or polarization of light, and is typically composed of a pixel array, allowing precise control of the optical characteristics of each pixel. A liquid crystal lens, on the other hand, adjusts the focal length by changing the orientation of liquid crystal molecules and does not possess pixel-based modulation capabilities. A liquid crystal lens is essentially a lens, and the focusing process involves adjusting the focal length position in an axially symmetrical manner. Because a spatial light modulator is a pixel array, it can adjust the phase distribution of light by loading a hologram; the phase change can be non-uniform, thus allowing for more flexible alteration of the light distribution.

[0027] Specifically, the phase modulation device 5 is configured as a liquid crystal lens; the liquid crystal lens includes a first substrate 51, a second substrate 52, a liquid crystal molecule layer and an electrode 53; the liquid crystal molecule layer is disposed between the first substrate 51 and the second substrate 52; a motor is disposed on the side of the first substrate 51 and the second substrate 52 near the liquid crystal molecule layer.

[0028] Specifically, the first substrate 51 and the second substrate 52 are configured as high-transmittance glass layers.

[0029] Specifically, a spacer layer 54 for adjusting the thickness of the liquid crystal lens is provided between the first substrate 51 and the second substrate 52.

[0030] Specifically, the electrode 53 is configured as a concentric ring electrode 53, or a continuous gradient electrode 53, or a segmented electrode 53 so that the refractive index distribution of the liquid crystal lens simulates the optical characteristics of a concave mirror.

[0031] Specifically, in some embodiments, the electrode 53 is configured as a concentric ring electrode 53, with each ring connected to an independent voltage source, and the voltage value gradually increases from the center to the edge.

[0032] In some embodiments, the motor is configured as a continuous gradient electrode 53, which gradually increases the voltage from the center to the edge of the liquid crystal lens through resistive voltage division.

[0033] The electronic control system 6 modulates the incident light by changing the optical properties of the liquid crystal molecule layer by controlling the different voltages generated by the control electrode 53.

[0034] Specifically, the focal length of the liquid crystal lens is f, and the formula for calculating the focal length is as follows:

[0035]

[0036] Where f is the focal length of the lens in millimeters, n is the refractive index of the lens material, and R1 and R2 are the radii of curvature of the two surfaces of the lens in millimeters.

[0037] Specifically, the actual refractive index of the liquid crystal lens is set to n, and the formula for calculating the actual refractive index is as follows:

[0038] n=n0+Δ n ·E;

[0039] Where n0 is the initial refractive index of the liquid crystal in the absence of an electric field, and Δn is the change in refractive index. E is the applied electric field strength, measured in volts per meter (V / m).

[0040] Specifically, the phase change of light in the liquid crystal lens is expressed by the following formula:

[0041]

[0042] Where Δφ is the optical path difference in radians (rad), λ is the wavelength of light in meters (m), d is the thickness of the liquid crystal layer in meters (m), n is the actual refractive index of the liquid crystal, and n0 is the initial refractive index of the liquid crystal in the absence of an electric field.

[0043] Specifically, the liquid crystal lens is set as a liquid crystal biconcave lens. The main lens 3 includes a plano-convex lens 31 and a concave-convex lens 32. The concave-convex lens 32 is set on the side of the plano-convex lens 31 close to the liquid crystal biconcave lens. The distance between the concave-convex lens 32 and the plano-convex lens 31 is d1, and the distance between the concave-convex lens 32 and the liquid crystal biconcave lens is d2.

[0044] Where the focal length of the plano-convex lens 31 is f1, the focal length of the concave-convex lens 32 is f2, and the focal length of the liquid crystal biconcave lens is f3, then the magnification of the echo signal imaged onto the end face of fiber 2 by the telescope system is:

[0045]

[0046] in,

[0047] Specifically, when no voltage is applied, the signal light passes through the liquid crystal lens without changing its light path and its phase remains unchanged. When a voltage is applied, the liquid crystal molecules deflect. For negative liquid crystals, at the edge of the aperture, the liquid crystal molecules rotate perpendicular to the electric field direction, and the refractive index perceived by the light is ne. From the edge of the aperture to the center of the aperture, due to the non-uniform field line distribution, the refractive index perceived by the liquid crystal molecules is neff(θ). At the center of the aperture, because it is not affected by the electric field, the liquid crystal molecules still exhibit their original state, and the refractive index perceived is no.

[0048] Liquid crystal molecules rearrange themselves under the influence of an applied electric field, causing a change in their birefringence (Δn). The applied electric field V can adjust Δn, making Δn change with voltage:

[0049] Δn(V)=n e (V)-n o ;

[0050] Liquid crystal lenses achieve a phase retardation distribution similar to that of traditional lenses by adjusting the orientation of liquid crystal molecules. For radially symmetric liquid crystal lenses, the phase retardation distribution can be approximated as parabolic.

[0051]

[0052] Where r is the radial coordinate of the lens aperture, λ is the wavelength of the incident light, and d is the thickness of the liquid crystal layer. Since Δn varies with the applied voltage V, the focal length f also varies with the voltage. Assuming the range of Δn is from Δnmin to Δnmax, the range of the focal length is:

[0053]

[0054] The telescope is designed based on the technical specifications of the lidar, and the liquid crystal lens device is designed based on the focal length of the secondary mirror. When using the lidar, the liquid crystal lens can scan near the focal length to find the voltage value with the maximum detection distance and the best signal-to-noise ratio, and wind speed is measured under these parameters.

[0055] The above description is merely a preferred embodiment of this utility model. The protection scope of this utility model is not limited to the above embodiments. All technical solutions falling within the scope of this utility model's concept are protected. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of this utility model should also be considered within the protection scope of this utility model.

Claims

1. A phase-modulation-unit-based adaptive lidar system, characterized by: It includes a housing (1), one end of which is connected to an optical fiber (2); A secondary lens (4) is disposed inside the housing (1) near the optical fiber (2); and the main lens (3), which is disposed at one end of the housing (1) away from the optical fiber (2) and is composed of at least one lens; The secondary lens (4) includes a phase modulation device (5), which is disposed inside the housing (1). The phase modulation device (5) achieves continuous zoom through an electronic control system (6). The phase modulation device (5) is disposed at the secondary lens (4) as a lens constituting the secondary lens (4).

2. The phase-modulation-cell based adaptive lidar system of claim 1, wherein: The phase modulation device (5) is configured as a spatial light modulator or a liquid crystal lens.

3. The phase-modulation-cell based adaptive lidar system of claim 1, wherein: The phase modulation device (5) is configured as a liquid crystal lens; The liquid crystal lens includes a first substrate (51); Second substrate (52); A liquid crystal molecule layer is disposed between a first substrate (51) and a second substrate (52); Electrode (53), motors are provided on the side of the first substrate (51) and the second substrate (52) near the liquid crystal molecular layer.

4. The phase-modulation-cell based adaptive lidar system of claim 3, wherein: The electrode (53) is configured as a concentric ring electrode (53), a continuous gradient electrode (53), or a segmented electrode (53) so that the refractive index distribution of the liquid crystal lens simulates the optical characteristics of a concave mirror.

5. The phase-modulation-cell based adaptive lidar system of claim 4, wherein: The electrode (53) is configured as a concentric ring electrode (53), with each ring connected to an independent voltage source, and the voltage value gradually increases from the center to the edge.

6. The phase-modulation-cell based adaptive lidar system of claim 4, wherein: The motor is configured as a continuous gradient electrode (53), which gradually increases the voltage from the center to the edge of the liquid crystal lens through resistive voltage division.

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