Backscattered Light Test System and Method for Telescope System

Abstract

The present invention relates to a backward scattering light test system and method for a telescope system, mainly solving the technical problem that the existing test methods can only measure the stray light outside the field of view and cannot meet the test requirements of backward scattering light. The test system includes a laser light source, a wave plate, a polarization beam splitter, a beam splitter, and an information acquisition and processing unit arranged in sequence along the light path of the laser light source; the wave plate is a half-wave plate; a first light trap is provided on the reflection light path of the polarization beam splitter; a second light trap is provided on the reflection light path of the beam splitter, and a third light trap is provided at the outlet end of the telescope system; the information acquisition and processing unit includes a camera and a signal processing module. The camera is located on the other reflection light path of the beam splitter and is used to collect the backward scattering light and transmit it to the signal processing module; the signal processing module is used to calculate and process the received backward scattering light and output the test result. Based on this, the present invention also provides a test method for the above test system.

Description

Technical Field

[0001] The present invention relates to a stray light test system and method, and particularly to a backward scattered light test system and method for a telescope system. Background Art

[0002] Transmitting and receiving integrated optical systems, such as gravitational wave telescope systems, laser communication telescope systems, laser gyroscopes, etc. The complexity of suppressing and evaluating stray light in such systems partly stems from the interaction between incident light and received light. The reason is that to ensure that such systems have sufficient energy for long-distance transmission or high-precision measurement, the incident light usually selects strong lasers. However, when this strong laser interacts with optical elements or the target surface, backward scattered light will be generated. Due to its intensity and spectral characteristics, this backward scattered light will cause significant interference to the received weak signal light. The interference of the backward scattered light not only affects the clarity of the signal but also may introduce additional noise, thereby reducing the signal-to-noise ratio of the optical system. Therefore, the importance of backward scattered light testing in transmitting and receiving integrated optical systems is self-evident, especially in application scenarios of high precision and long-distance transmission.

[0003] In transmitting and receiving integrated optical systems, the suppression and testing of backward scattered light face unique challenges because it involves light in the normal optical path, which makes traditional suppression methods such as occlusion and spraying with extinction black paint no longer applicable. Existing stray light test methods are mainly used to test stray light outside the field of view. Since the incident light and the backward scattered light are in the same optical path, the backward scattered light is blocked during testing and cannot be measured. Therefore, existing stray light test methods cannot meet the test requirements of backward scattered light. Summary of the Invention

[0004] The object of the present invention is to solve the technical problem that existing test methods can only measure stray light outside the field of view and cannot meet the test requirements of backward scattered light, and to provide a backward scattered light test system and method for a telescope system.

[0005] To achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A backward scattered light test system for a telescope system, characterized in that:

[0007] It includes a laser light source, a wave plate, a polarization beam splitter, a beam splitter sequentially arranged along the light path of the laser light source, and an information acquisition and processing unit;

[0008] The wave plate is a half-wave plate for rotating the polarization degree of the outgoing light;

[0009] A first optical trap is provided on the reflection optical path of the polarization beam splitter. The emitted light from the laser light source is divided into two paths after passing through the polarization beam splitter. Among them, the S light in the emitted light is absorbed by the first optical trap after being reflected by the polarization beam splitter; the P light in the emitted light passes through the polarization beam splitter and enters the beam splitter mirror.

[0010] A second optical trap is provided on the reflection optical path of the beam splitter mirror. The P light in the emitted light is divided into two paths after passing through the beam splitter mirror. One path is absorbed by the second optical trap after being reflected by the beam splitter mirror, and the other path passes through the beam splitter mirror and enters the telescope system.

[0011] A third optical trap is provided at the exit end of the telescope system. After the P light enters the telescope system, a part of it enters the third optical trap, and the other part generates backward scattered light in the telescope system, and then enters the information acquisition and processing unit after being reflected by the beam splitter mirror.

[0012] The information acquisition and processing unit includes a camera and a signal processing module connected to the camera; the camera is located on the backward reflection optical path of the beam splitter mirror for collecting the backward scattered light and transmitting it to the signal processing module; the camera is connected to the laser light source for receiving the start signal emitted by the laser light source; the signal processing module is used to calculate and process the received backward scattered light and output the test result.

[0013] Further, the distance between the center point of the beam splitter mirror and the entrance of the telescope system is Δ 1 , and the distance from the second optical trap is Δ 2 , and (Δ 1 - Δ 2 ) > ;

[0014] The distance between the third optical trap and the exit of the telescope system is Δ 3 , and Δ 3 > ; where T is the time resolution of the camera.

[0015] Further, the laser light source is a picosecond pulsed laser, and an optical isolator is provided between the laser light source and the wave plate to improve the transmission efficiency of the emitted light.

[0016] Further, a lens is also provided between the polarization beam splitter and the beam splitter mirror, which is used to adjust the beam waist diameter of the P light transmitted through the polarization beam splitter.

[0017] Further, a polarizer is also provided at the entrance end of the camera for adjusting the polarization degree of the optical signal.

[0018] At the same time, the present invention also provides a method for testing the backward scattered light of a telescope system, including the following steps:

[0019] Step 1: Calibrate the incident light energy of the telescope system to obtain the initial incident light energy P 0 ;

[0020] Step 2: Assemble the backscattered light test system of the above telescope system;

[0021] Step 3: Turn on the laser light source to emit the outgoing light, and at the same time send a start signal to the camera to make the camera in a working state;

[0022] Step 4: The outgoing light is divided into two paths after passing through the wave plate and the polarization beam splitter. Among them, the S light in the outgoing light is absorbed by the first light trap after reflection; the P light in the outgoing light enters the beam splitter after transmission and is then divided into two paths. One path is absorbed by the second light trap after reflection, and the other path enters the telescope system after transmission;

[0023] Step 5: After the P light enters the telescope system, a part of it enters the third light trap, and the other part generates backscattered light in the telescope system and enters the camera after being reflected by the beam splitter;

[0024] Step 6: The camera transmits the backscattered light to the signal processing module, and the signal processing module obtains the incident light energy P corresponding to the backscattered light bs ;

[0025] Step 7: Based on the initial incident light energy P obtained in Step 1 0 and the incident light energy P obtained in Step 6 bs , calculate the backscattered light suppression ability of the telescope system, so as to realize the test of the backscattered light of the telescope system.

[0026] Further, in Step 1, the specific method of the calibration is as follows:

[0027] 1.1. Assemble the calibration system according to the backscattered light test system of the above telescope system. Among them, move the camera to the entrance pupil position of the telescope system; the distance between the center point of the beam splitter and the entrance pupil plane of the camera is Δ 4 , and the distance from the second light trap is Δ 2 , and (Δ 4 -Δ 2 )>[[]] ; Among them, c is the speed of light in vacuum, and T is the time resolution of the camera;

[0028] 1.2. Turn on the laser light source, and the emitted outgoing light is received by the camera after passing through the wave plate, the polarization beam splitter, and the beam splitter in sequence;

[0029] 1.3. The camera transmits the optical signal of the received outgoing light to the signal processing module, and the signal processing module calculates and outputs the energy of the optical signal, and this energy P0 This is the incident light energy of the telescope system, thus completing the calibration.

[0030] Further, in step 2, during assembly, the distance between the center point of the beam splitter and the entrance of the telescope system is Δ 1 , and the distance from the second light trap is Δ 2 , then the two need to satisfy: (Δ 1 - Δ 2 ) > , where T is the time resolution of the camera, c is the speed of light in vacuum; the distance between the third light trap and the exit of the telescope system is Δ 3 , then Δ 3 needs to satisfy Δ 3 > .

[0031] Further, in step 5, the backscattered light entering the camera also contains interfering scattered light, and the interfering scattered light includes scattered light from the beam splitter, backscattered light from the second light trap, and backscattered light from the third light trap.

[0032] Further, step 6 is specifically as follows: the camera transmits the backscattered light to the signal processing module, and the signal processing module calculates the time when the backscattered light from the telescope system and the interfering scattered light reach the camera respectively, classifies and outputs the arrival times of the scattered lights, and then extracts the scattered lights that arrive within a preset time period from the output results, so as to obtain the number of photons of the backscattered light required for testing, and further calculate the corresponding incident light energy P bs .

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The present invention adopts polarization and beam splitting technologies to realize common path testing. This method allows the test light (i.e., the emitted light from the laser light source) and the backscattered light to propagate on the same optical path, effectively solving the problem of the backscattered light being blocked; at the same time, through the camera and the signal processing module, the collection and precise selection of the backscattered light can be realized, thereby improving the test accuracy of the backscattered light.

[0035] 2. The present invention improves the efficiency and accuracy of the signal in the subsequent processing process by reasonably setting the relative distances between the devices, thereby improving the test efficiency and test accuracy of the backscattered light.

[0036] 3. The present invention provides an efficient and accurate test platform for researching and analyzing the backscattering characteristics of the telescope system. This method is particularly suitable for fields that require precise testing and control of the backscattering light characteristics, such as materials science, space exploration, and lidar research. Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of an embodiment of the backscattered light test system for the telescope system of the present invention.

[0038] Figure 2 It is a schematic structural diagram of the initial incident light energy calibration system in the embodiment of the backscattered light test method for the telescope system of the present invention.

[0039] Figure 3 It is a schematic diagram of the pulsed laser of the laser light source and the optical signal received by the camera in the embodiment of the backscattered light test method for the telescope system of the present invention.

[0040] The description of the reference numerals is as follows:

[0041] 1 - Laser light source, 2 - Wave plate, 3 - Polarizing beam splitter, 4 - Beam splitter, 5 - Telescope system, 6 - First light trap, 7 - Second light trap, 8 - Third light trap, 9 - Camera, 10 - Signal processing module, 11 - Optical isolator, 12 - Lens, 13 - Polarizer. Detailed Embodiments

[0042] To make the objectives, advantages and features of the present invention clearer, the present invention will be described in detail below in conjunction with the drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention, and the purpose is not to limit the protection scope of the present invention.

[0043] As Figure 1 shown, this embodiment provides a backscattered light test system for a telescope system, including a laser light source 1, a wave plate 2, a polarizing beam splitter 3, a beam splitter 4 arranged in sequence along the output light path of the laser light source 1, and an information acquisition and processing unit.

[0044] The laser light source 1 is a picosecond pulsed laser, which is used to generate test light (i.e., output light) of a specified wavelength. To improve the transmission efficiency of the output light, an optical isolator 11 is also provided at the light output end of the laser light source 1 (i.e., between the laser light source 1 and the wave plate 2), so that the output light of the specified wavelength can be transmitted quickly.

[0045] The wave plate 2 is a half-wave plate, i.e., a λ / 2 wave plate, which is used to rotate the polarization degree of the output light. When the wave plate 2 is used in cooperation with the polarizing beam splitter 3, a beam splitter with a variable ratio can be formed. The polarization degree of the polarizing beam splitter 3 is determined according to the measurement requirements of the telescope system 5. Generally, the higher the polarization degree, the higher the measurement accuracy.

[0046] The splitting ratio of the polarization beam splitter 3 is 50:50. A first optical trap 6 is provided on its reflection optical path. The emitted light from the laser light source 1 is split into two paths after passing through the polarization beam splitter 3. Among them, the S light in the emitted light is reflected by the polarization beam splitter 3 and then absorbed by the first optical trap 6; the P light in the emitted light passes through the polarization beam splitter 3 and then enters the beam splitter 4. In this embodiment, a lens 12 is further provided between the polarization beam splitter 3 and the beam splitter 4 for adjusting the beam waist diameter of the P light transmitted through the polarization beam splitter 3.

[0047] The splitting ratio of the beam splitter 4 is 50:50. A second optical trap 7 is provided on its reflection optical path. The P light transmitted through the polarization beam splitter 3 is split into two paths after passing through the beam splitter 4. One path is reflected by the beam splitter 4 and then absorbed by the second optical trap 7, and the other path passes through the beam splitter 4 and enters the telescope system 5.

[0048] In this embodiment, the distance between the center point of the beam splitter 4 and the entrance of the telescope system 5 is Δ 1 , and the distance from the second optical trap 7 is Δ 2 , then the two should satisfy: (Δ 1 - Δ 2 ) > , where, c is the propagation speed of light in vacuum, and T is the time resolution of the camera 9.

[0049] In order to improve the test accuracy, a third optical trap 8 is provided at the exit end of the telescope system 5. The distance between the third optical trap 8 and the exit of the telescope system 5 is Δ 3 , and Δ 3 > . After the P light enters the telescope system 5, a part of it enters the third optical trap 8, and the other part generates backward scattered light in the telescope system 5. The emitted scattered light is the signal light required for the test. The backward scattered light is then reflected by the beam splitter 4 and enters the information acquisition and processing unit.

[0050] The information acquisition and processing unit includes a camera 9 and a signal processing module 10 connected to the camera 9; the camera 9 is located on the backward reflection optical path of the beam splitter 4 (i.e., on the optical path opposite to the direction where the second optical trap 7 is located), and is used to collect the backward scattered light and transmit it to the signal processing module 10.

[0051] In this embodiment, the camera 9 is selected as an ultrafast camera. This type of camera has extremely high time resolution and can usually record the transient phenomenon of scattered light on the time scale of picoseconds (ps) and femtoseconds (fs). A polarizer 13 is also provided at the entrance end of the camera 9, which can adjust the polarization degree of the backward scattered light received by the camera 9 according to the polarization characteristics of the scattered light in the telescope system 5. The camera 9 is connected to the laser light source 1. When the laser light source 1 emits the emitted light, it also emits a reference signal to the camera 9 to make it start working synchronously.

[0052] The signal processing module 10 is used to calculate and process the received backscattered light and output the result.

[0053] The working principle of the test system of the present invention is as follows: The pulsed laser passes through the polarization beam splitter 3. The polarization beam splitter 3 transmits the P light and reflects the S light. The P light is split by the beam splitter 4 and then enters the telescope system 5. The backscattered light generated by the telescope system 5 is reflected by the beam splitter 4 and received by the camera 9.

[0054] During this process, the P light passing through the beam splitter 4 will generate scattered light (i.e., volume scattering), the telescope system 5 will generate backscattered light, and the second light trap 7 and the third light trap 8 will also generate corresponding backscattered light. Therefore, in the backscattered light received by the camera 9, in addition to the backscattered light of the telescope system 5, there is also the scattered light from the beam splitter 4 and the backscattered light generated by the second light trap 7 and the third light trap 8. However, only the backscattered light returned by the telescope system 5 is the signal light to be detected, and the other scattered lights are interference scattered lights at this time. Since the interference scattered lights are useless for the signal light, they are collectively referred to as light pollution.

[0055] The existence of the above light pollution will limit the test accuracy of the test system. Therefore, suppressing the above light pollution is the key technology of the stray light test system. In this embodiment, the camera 9 is used to identify the above different scattered light signals. As mentioned above, the distance between the center point of the beam splitter 4 and the entrance of the telescope system 5 is Δ 1 , and the distance between the beam splitter 4 and the second light trap 7 is Δ 2 , the distance between the third light trap 8 and the exit of the telescope system 5 is Δ 3 , from the entrance of the telescope system 5 to the exit of the telescope system 5, the longest optical path experienced by the light in the normal optical path is Δ opt . The specific settings of the positions between the devices make the different scattered lights reach the camera 9 at different times. Finally, the signal processing module 10 calculates and processes the received scattered light, so as to accurately extract the backscattered light information of the telescope system 5.

[0056] This embodiment also provides a method for testing the backscattered light of a telescope system, including the following steps:

[0057] Step 1, calibrate the incident light energy of the telescope system 5.

[0058] The purpose of calibration is to obtain the initial incident light energy, so as to obtain the reference value required for the backscattered light test. Referring to Figure 2 , the calibration method is as follows:

[0059] Assemble the components of the backscattered light test system for the telescope system according to this embodiment. When calibrating, the telescope system 5 is not required. Just place the camera 9 at the entrance pupil position of the telescope system 5 and connect it to the signal processing module 10. During the assembly of each component, the distance between the center point of the beam splitter 4 and the entrance pupil plane of the camera 9 is Δ 4 , and Δ 4 = Δ 1 , and the distance from the second light trap 7 is Δ 2 , and (Δ 1 - Δ 2 ) > .

[0060] After assembly, turn on the laser light source 1. The emitted light it emits passes through the optical isolator 11, the wave plate 2, the polarization beam splitter 3, the lens 12, and the beam splitter 4 in sequence and is received by the camera 9. At this time, set the gain of the camera 9 and the cumulative number of frames of the received optical signal according to the signal strength of the emitted light. After the emitted light is stable, the camera 9 transmits the received optical signal to the signal processing module 10, and the signal processing module 10 calculates and outputs the number of photons of this optical signal M 0 , so as to obtain the initial incident light energy P 0 , that is:

[0061]

[0062] This incident light energy P 0 is the incident light energy of the calibrated telescope system 5.

[0063] Step 2. Assemble the backscattered light test system of the telescope system according to the structure shown in Figure 1 . Keep the distance between the center point of the beam splitter 4 and the entrance of the telescope system 5 as Δ 1 , and the distance from the second light trap 7 as Δ 2 , and (Δ 1 - Δ 2 ) > ; the distance between the third light trap 8 and the exit of the telescope system 5 is Δ 3 , and Δ 3 > .

[0064] Step 3. The laser light source 1 emits emitted light and simultaneously sends a start signal to the camera 9 to realize synchronous control of the laser light source 1 and the camera 9.

[0065] Step 4: The emitted light is successively divided into two paths after passing through the optical isolator 11, the wave plate 2, and the polarization beam splitter 3. Among them, the S light in the emitted light is reflected and then absorbed by the first optical trap 6, and the P light in the emitted light is transmitted and then enters the beam splitter 4 through the lens 12. The P light is divided into two paths again by the beam splitter 4. One path is reflected and then absorbed by the second optical trap 7, and the other path is transmitted and then enters the telescope system 5. Among the P light entering the telescope system 5, a part enters the third optical trap 8, and the other part generates backward scattered light in the telescope system 5, and then enters the camera 9 after being reflected by the beam splitter 4. At this time, according to the signal strength of the backward scattered light, the gain of the camera 9 is reset to , and at the same time, the cumulative number of frames for the camera 9 to receive the optical signal is set to AC bs . The camera 9 transmits the received backward scattered light to the signal processing module 10, and the signal processing module 10 outputs the number of photons of the backward scattered light.

[0066] Step 5: Since the backward scattered light received by the camera 9 also contains interfering scattered light, which includes the scattered light from the beam splitter 4, the backward scattered light from the second optical trap 7, and the backward scattered light from the third optical trap 8. Based on this, according to the intervals between the components in Step 2, the times for the camera 9 to receive the scattered lights are made different. Then, the scattered lights and the corresponding time information are synchronously transmitted to the signal processing module 10. Through the signal processing module 10, different scattered lights can be calculated and identified, and then the number of photons of the backward scattered light returned by the telescope system 5 is extracted M bs , and finally, the incident light energy P entering the telescope system 5 can be obtained through calculation bs , P bs is calculated by the following formula:

[0067] .

[0068] Step 6: Based on the incident light energy P calibrated in Step 1 0 and the incident light energy P calculated in Step 5 bs , the backward scattered light suppression ability of the telescope system 5 is further calculated S , that is:

[0069] .

[0070] In this embodiment, the process of the signal processing module 10 for processing the backward scattered light is realized by respectively calculating the times when the backward scattered light from the telescope system 5 and the interfering scattered light reach the camera 9. Specifically:

[0071] According to the intervals between the components inside the above test system, referring to Figure 3, the scattered light generated after the outgoing light reaches the beam splitter 4 is first received by the camera 9. Assuming the time it experiences is T 1 , then the time for the backward scattered light returned by the outgoing light through the second optical trap 7 to reach the camera 9 is T 2 , that is, T 2 = T 1 + ; the time experienced by the backward scattered light returned by the outgoing light through the telescope system 5 is between T 3 and T 4 , where, T 3 = T 1 + , T 4 = T 1 + . Since the outgoing light usually travels along the normal optical path after entering the telescope system 5, at this time, the outgoing light is incident on the surface of the optical element, generating a first-order backward scattered light, and the contribution of the second-order scattered light is too small to be ignored. Then, the longest optical path Δ opt of the first-order backward scattered light is approximately equal to the longest optical path experienced by the normal optical path in the telescope system 5 from the entrance to the exit of the telescope system 5. In addition, the time for the backward scattered light returned by the third optical trap 8 is T 5 , T 5 = T 1 + .

[0072] In summary, the order in which the camera 9 receives the scattered lights is the scattered light generated by the beam splitter 4, the backward scattered light generated by the second optical trap 7, the backward scattered light of the telescope system 5, and the backward scattered light generated by the third optical trap 8. By using the camera 9 to identify the above four-way scattered lights, and then through the signal processing module 10, they can be classified and output according to the time when each scattered light reaches the camera 9. After that, the scattered light that arrives within the corresponding time period can be accurately extracted from the output results, so as to obtain the backward scattered light required for the test.

[0073] The present invention uses a beam splitting technology to achieve a common optical path test. This method allows the test light (i.e., the outgoing light emitted by the laser light source) and the backward scattered light to propagate on the same optical path, effectively solving the problem of the backward scattered light being blocked; at the same time, the ultrafast diagnostic technology formed by combining an ultrafast camera and a signal processing module can achieve precise selection of the signal light, improving the test accuracy of the backward scattered light.

[0074] The present invention provides an efficient and accurate test platform for researching and analyzing the backward scattering characteristics in an optical system. This method is particularly suitable for fields that require precise testing and control of the backward scattering light characteristics, such as materials science, space exploration, and lidar research.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A backscattered light testing system for a telescope system, characterized in that: It comprises a laser light source (1), a wave plate (2), a polarization beam splitter (3), a beam splitter (4) arranged in sequence along the outgoing light path of the laser light source (1), and an information acquisition and processing unit; The wave plate (2) is a half-wave plate, which is used to rotate the polarization degree of the outgoing light; A first light trap (6) is provided on the reflection light path of the polarization beam splitter (3), and the outgoing light of the laser light source (1) is divided into two paths after passing through the polarization beam splitter (3), wherein the S light in the outgoing light is reflected by the polarization beam splitter (3) and absorbed by the first light trap (6); and the P light in the outgoing light is transmitted through the polarization beam splitter (3) and enters the beam splitter (4); A second light trap (7) is provided on the reflection light path of the beam splitter (4); light P in the outgoing light is divided into two paths after passing through the beam splitter (4); one path is absorbed by the second light trap (7) after being reflected by the beam splitter (4), and the other path is transmitted through the beam splitter (4) into the telescope system (5); A third light trap (8) is provided at the exit end of the telescope system (5); after the P light enters the telescope system (5), a portion enters the third light trap (8), and the other portion generates backscattered light in the telescope system (5), which is then reflected by the beam splitter (4) and enters the information collection and processing unit; The distance between the center point of the beam splitter (4) and the entrance of the telescope system (5) is Δ1, and the distance between the center point of the beam splitter (4) and the second light trap (7) is Δ2, and The distance between the third light trap (8) and the exit of the telescope system (5) is Δ3, and Where c is the speed of light in a vacuum, T is the time resolution of the camera (9); The information acquisition and processing unit comprises a camera (9) and a signal processing module (10) connected to the camera (9); the camera (9) is located on the back reflection light path of the beam splitter (4) and is used to collect backscattered light and transmit it to the signal processing module (10); the camera (9) is connected to the laser light source (1) and is used to receive a start signal emitted by the laser light source (1); the signal processing module (10) is used to perform calculation processing on the received backscattered light and output a test result.

2. The backscattered light testing system of the telescope system according to claim 1, characterized in that: The laser light source (1) is a picosecond pulse laser, and an optical isolator (11) is provided between the laser light source (1) and the wave plate (2) to improve the transmission efficiency of the emitted light.

3. The backscattered light testing system of the telescope system according to claim 2, characterized in that: It also includes a lens (12) arranged between the polarization beam splitter (3) and the beam splitter (4), which is used to adjust the beam waist aperture of the P light transmitted through the polarization beam splitter (3).

4. The backscattered light testing system of the telescope system according to claim 3, characterized in that: The entrance end of the camera (9) is also provided with a polarizing plate (13) for adjusting the polarization degree of the optical signal.

5. A method for testing backscattered light of a telescope system, characterized in that: The following steps are involved: Step 1, calibrating the incident light energy of the telescope system (5) to obtain the initial incident light energy P0; Step 2, assembling the backscattered light testing system of the telescope system according to any one of claims 1 to 4; Step 3, turning on the laser light source (1) to emit output light, and at the same time transmitting a start signal to the camera (9), so that the camera (9) is in a working state; Step 4, the outgoing light is sequentially passed through the wave plate (2) and the polarization beam splitter (3) and then split into two paths, wherein the S light in the outgoing light is absorbed by the first light trap (6) after being reflected; the P light in the outgoing light enters the beam splitter (4) after being transmitted, and then is split into two paths again, wherein one path is absorbed by the second light trap (7) after being reflected, and the other path enters the telescope system (5) after being transmitted; Step 5, after the P light enters the telescope system (5), a part of it enters the third light trap (8), and the other part generates backscattered light in the telescope system (5), and then enters the camera (9) after being reflected by the beam splitter (4); Step 6: The camera (9) transmits the backscattered light to the signal processing module (10), and the signal processing module (10) obtains the incident light energy P corresponding to the backscattered light. bs ; Step 7: Based on the initial incident light energy P0 obtained in step 1 and the incident light energy P obtained in step 6 bs , the backscattered light suppression capability of the telescope system (5) is calculated, thereby realizing the test of the backscattered light of the telescope system.

6. The backscattered light testing method of a telescope system according to claim 5, characterized in that: In step 1, the calibration method is specifically as follows: 1.

1. A system for assembling and calibrating a backscattered light test system for a telescope system according to any one of claims 1 to 4, wherein the camera (9) is moved to the entrance pupil position of the telescope system (5); the distance between the center point of the beam splitter (4) and the entrance pupil plane of the camera (9) is Δ4, and the distance between the center point of the beam splitter (4) and the second light trap (7) is Δ2, and Where c is the speed of light in a vacuum, T is the time resolution of the camera (9); 1.

2. Turn on the laser light source (1), and the emitted light passes through the wave plate (2), the polarization beam splitter (3), and the beam splitter (4) in sequence and is then received by the camera (9); 1.

3. The camera (9) transmits the received optical signal of the outgoing light to the signal processing module (10), and the signal processing module (10) calculates and outputs the energy of the optical signal. The energy P0 is the incident light energy of the telescope system (5), thereby completing the calibration.

7. The backscattered light testing method of a telescope system according to claim 5, characterized in that: In step 2, during assembly, the distance between the center point of the beam splitter (4) and the entrance of the telescope system (5) is Δ1, and the distance between the center point of the beam splitter (4) and the entrance of the telescope system (5) is Δ2, and the two must satisfy: Where T is the time resolution of the camera, c is the propagation speed of light in a vacuum; the distance between the third light trap (8) and the exit of the telescope system (5) is Δ3, then Δ3 must satisfy 8. The backscattered light testing method of a telescope system according to claim 7, characterized in that: In step 5, the backscattered light entering the camera (9) also contains interference scattered light, and the interference scattered light includes scattered light from the beam splitter (4), backscattered light from the second light trap (7) and backscattered light from the third light trap (8).

9. The backscattered light testing method of a telescope system according to claim 8, characterized in that: Step 6 is specifically, the camera (9) transmits the backscattered light to the signal processing module (10), and the signal processing module (10) calculates the time when the backscattered light and the interference scattered light from the telescope system (5) reach the camera, classifies and outputs the arrival time of each scattered light, and then extracts the scattered light that arrives within a preset time period from the output result, thereby obtaining the number of photons of the backscattered light required for the test, and then calculating the corresponding incident light energy P bs .

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