Satellite-borne telescope back scattering light measuring device and method based on gravitational wave detection

Abstract

The invention discloses a gravitational wave detection-based satellite-borne telescope back scattered light measuring device and method, and solves the problem that a traditional stray light measuring device cannot measure the back scattered light of a satellite-borne telescope in a gravitational wave detection system. The laser source, the collimating mirror, the semi-transparent and semi-reflective mirror, the detector and the phase-locked amplifier are arranged at the incident end of a telescope to be detected, and the extinction cavity is arranged at the emergent end of the telescope to be detected. The laser source emits measuring light; the collimating lens collimates the measuring light; the half-transparent and half-reflecting mirror divides the collimated measurement light into transmission light and first reflection light, wherein the transmission light enters the telescope to be measured and then generates emergent light and back scattering light; the semi-transparent and semi-reflective mirror is also used for reflecting the backward scattered light to form second reflected light; the detector detects the second reflected light; the input end of the phase-locked amplifier is connected with the output end of the detector so as to receive an electric signal to be detected; and the extinction cavity is used for carrying out extinction on emergent light passing through the telescope to be measured.

Description

Technical Field

[0001] The present invention relates to a device and method for measuring scattered light, and in particular to a device and method for measuring backscattered light of a space-borne telescope based on gravitational wave detection. Background Art

[0002] Since gravitational waves were directly observed, a series of major advances have been made in gravitational wave detection. To ensure the accuracy of space gravitational wave detection, a Michelson laser interferometer with an "equilateral triangle" arm length of hundreds of thousands or millions of kilometers will be established in space. The laser beams will interfere at the intersection. When space gravitational waves pass through, it will cause a slight deformation of the interferometer arm length, resulting in interference signals in the interferometer. By analyzing the intensity and frequency of the interference signal, the existence of gravitational waves and their frequency characteristics can be determined, thereby studying the characteristics of celestial bodies, such as black hole mergers and neutron star collisions.

[0003] The satellite telescope is a key component of the gravitational wave detection system. Its function is to send and receive signal beams. In order to achieve high-precision detection of gravitational waves, it is necessary to ensure that the received signal beam is not annihilated by the backscattered stray light of the satellite telescope itself when the signal beam passes through the interferometer arm. According to theoretical calculations, the background stray light of the satellite telescope must be less than 10 -10 Order of magnitude. Traditional stray light measurement devices mainly include two types: stray light index (VGI) measurement device and point source transmittance (PST) test device. The VGI measurement device mainly realizes the test of the overall stray light suppression capability of the optomechanical system; while the PST measurement device mainly realizes the test of the stray light suppression capability of the optomechanical system at various off-axis field angles. Unlike traditional stray light measurement devices, in gravitational wave detection systems, the main source of the system's stray light is the mirror backscattered light caused by the insufficient mirror roughness of the satellite-borne telescope and the low coating efficiency, while traditional stray light measurement devices are unable to measure the backscattered stray light in the gravitational wave telescope system. Summary of the invention

[0004] In order to solve the technical problem that traditional stray light measuring devices cannot measure the backscattered light of a satellite telescope in a gravitational wave detection system, the present invention provides a device and method for measuring backscattered light of a satellite telescope based on gravitational wave detection.

[0005] In order to achieve the above object, the present invention adopts the following technical solution:

[0006] A device for measuring backscattered light of a space-borne telescope based on gravitational wave detection is special in that it comprises a laser source, a collimator, a semi-transparent and semi-reflective mirror, a detector and a phase-locked amplifier arranged at the incident end of the telescope to be measured, and an extinction cavity arranged at the output end of the telescope to be measured;

[0007] The laser source is used to emit measurement light to the telescope to be measured;

[0008] The collimator is arranged on the optical path where the measuring light is located, and its size matches the entrance pupil size of the telescope to be measured, and is used to collimate the measuring light;

[0009] The semi-transparent and semi-reflective mirror is arranged on the optical path between the collimating mirror and the telescope to be measured, and is used to divide the measuring light into the transmitted light and the first reflected light, wherein the transmitted light generates the outgoing light and the backscattered light after entering the telescope to be measured, the outgoing light is emitted from the outgoing end of the telescope to be measured, and the backscattered light is emitted from the incident end of the telescope to be measured; the semi-transparent and semi-reflective mirror is also used to reflect the backscattered light to form the second reflected light;

[0010] The detector is arranged on the optical path where the second reflected light is located, and is used to detect the second reflected light and convert the second reflected light into an electrical signal;

[0011] The input end of the phase-locked amplifier is connected to the output end of the detector, and is used to receive an electrical signal to extract the measurement result of the backscattered light of the telescope to be measured;

[0012] The extinction cavity is used to extinct the outgoing light after passing through the telescope to be tested.

[0013] Furthermore, it also includes a light trap arranged on the light path where the first reflected light is located;

[0014] The light trap includes a first high-reflection mirror and an absorption cavity;

[0015] The first high-reflection mirror is used to reflect the first reflected light to the absorption cavity;

[0016] The absorption cavity is used for absorbing the first reflected light.

[0017] Further, a chopper is included;

[0018] The chopper is arranged on the optical path between the collimating mirror and the semi-transparent and semi-reflective mirror, and is used to modulate the frequency of the collimated measuring light to improve the acquisition signal-to-noise ratio.

[0019] Further, it also includes a sunshade;

[0020] The light shield is arranged on the periphery of the second reflected light.

[0021] Furthermore, the extinction cavity comprises a first cylindrical segment, a second cylindrical segment, a third cylindrical segment, and a fourth cylindrical segment connected in sequence;

[0022] The central axes of the first cylindrical section and the second cylindrical section are perpendicular to each other; a second high-reflection mirror is provided on the inner wall of the connection between the first cylindrical section and the second cylindrical section;

[0023] The central axes of the second cylindrical segment and the third cylindrical segment are perpendicular to each other; a third high-reflection mirror is provided on the inner wall of the connection between the second cylindrical segment and the third cylindrical segment;

[0024] The central axes of the third cylindrical segment and the fourth cylindrical segment are perpendicular to each other; a fourth high-reflection mirror is arranged on the inner wall of the connection between the third cylindrical segment and the fourth cylindrical segment.

[0025] Furthermore, the inner surfaces of the first cylindrical section, the second cylindrical section, the third cylindrical section, and the fourth cylindrical section are all sprayed with aerospace matte black paint;

[0026] The second high-reflective mirror, the third high-reflective mirror and the fourth high-reflective mirror are all processed by ultra-smooth processing, and the roughness is less than or equal to 0.15nm.

[0027] Furthermore, it also includes a low-pressure cavity, the interior of which is a hundred-level low-pressure environment;

[0028] The laser source, the collimating mirror, the chopper, the semi-transparent and semi-reflective mirror, the detector, the light shield and the extinction cavity are all arranged in the low-pressure cavity.

[0029] Furthermore, the semi-transparent and semi-reflective mirror is processed by ultra-smooth processing, and the roughness is less than or equal to 0.1nm;

[0030] The laser source is a fiber continuous light laser with a power of 10W or more;

[0031] The detector is a photoelectric detector with a gain range of 10 3 ~10 8 , the limit detection capability is less than or equal to 10 -10 Magnitude.

[0032] A method for measuring backscattered light of a space-borne telescope based on gravitational wave detection, using the above-mentioned device for measuring backscattered light of a space-borne telescope based on gravitational wave detection, is special in that it comprises the following steps:

[0033] Step 1, placing the device for measuring backscattered light of a space-borne telescope based on gravitational wave detection as described in any one of claims 1 to 8 and the telescope to be tested in a low-pressure environment;

[0034] Step 2: The laser source emits measurement light, which is collimated by a collimator and then transmitted by a semi-transparent and semi-reflective mirror. After the transmitted light enters the telescope to be measured, it generates output light and backscattered light.

[0035] Step 3: The outgoing light is emitted from the telescope to be tested to the extinction cavity, and the extinction cavity extincts it; the backscattered light is then reflected by the semi-transparent and semi-reflective mirror to form the second reflected light that enters the detector;

[0036] Step 4: The detector receives the second reflected light, converts it into an electrical signal, and outputs it to a phase-locked amplifier to obtain a backscattered light measurement result of the telescope to be tested.

[0037] Furthermore, step 1 specifically includes placing the above-mentioned satellite telescope backscattered light measurement device based on gravitational wave detection and the telescope to be tested in a low-pressure cavity;

[0038] Step 2 is specifically as follows: the laser source emits measurement light, the measurement light is collimated by a collimator, and then frequency-modulated by a chopper, and then divided into transmitted light and first reflected light by a semi-transparent and semi-reflective mirror. After the transmitted light enters the telescope to be measured, an outgoing light and backscattered light are generated; the first reflected light is reflected by a first high-reflective mirror to an absorption cavity, and the absorption cavity absorbs the first reflected light;

[0039] Specifically, step 4 includes: the detector receives the second reflected light, converts it into an electrical signal and sends it to the phase-locked amplifier, which synchronizes the phase and frequency of the electrical signal with the modulation frequency of the chopper to extract the backscattered light measurement result of the telescope to be tested.

[0040] Beneficial effects of the present invention:

[0041] 1. The present invention provides a device and method for measuring backscattered light of a satellite telescope based on gravitational wave detection, wherein a semi-transparent and semi-reflective mirror and a detector are provided for the telescope to be measured; the semi-transparent and semi-reflective mirror can reflect the backscattered light to the detector for measurement, and the extinction cavity can absorb the large-aperture parallel light beam passing through the telescope to be measured, thereby ensuring that the output light from the telescope to be measured cannot be scattered to the detector through the inner wall of the box or the surface of the structure to form background stray light, thereby avoiding affecting the measurement result and greatly improving the measurement accuracy.

[0042] 2. The present invention arranges a light trap on the optical path of the first reflected light, and the light trap can absorb the first reflected light to avoid affecting the measurement accuracy of the backscattered light, thereby further improving the measurement accuracy of the backscattered light.

[0043] 3. The present invention also arranges a chopper between the collimating mirror and the semi-transparent and semi-reflective mirror. The chopper can modulate the received measuring laser into an incident light signal of a fixed frequency. Finally, the phase-locked amplifier searches for and extracts the fixed-frequency light signal from the detector output signal. This can greatly improve the signal-to-noise ratio, reduce environmental interference, and improve the measurement accuracy of backscattered light.

[0044] 4. The present invention sets a light shield around the second reflected light, which can prevent other external light from affecting the reflected light of the backscattered light, reduce environmental interference, and improve the measurement accuracy of the backscattered light.

[0045] 5. The extinction cavity provided by the present invention, the second high-reflection mirror, the third high-reflection mirror and the fourth high-reflection mirror are processed ultra-smoothly, with a roughness of less than or equal to 0.15nm, and the inner surfaces of the first cylindrical section, the second cylindrical section, the third cylindrical section and the fourth cylindrical section are sprayed with aerospace extinction black paint, and the absorption rate can reach 99%.

[0046] 6. The interior of the low-pressure cavity provided by the present invention is a hundred-level low-pressure environment, which can reduce environmental interference and improve the measurement accuracy of backscattered light.

[0047] 7. Since the intensity of backscattered light is extremely low, the laser source provided by the present invention is a 10W fiber continuous light laser, which can provide high-power measurement light without causing thermal effects, thereby ensuring measurement accuracy.

[0048] 8. The present invention provides a device and method for measuring backscattered light of a satellite telescope based on gravitational wave detection, which solves the problem of stray light testing caused by backscattered light of a satellite telescope in gravitational wave measurement. The present invention is different from traditional stray light coefficient testing devices and point source transmittance testing devices. Its core is to perform high-precision direct measurement of backscattered light of a satellite telescope. In essence, it is also a new type of stray light testing device. The extinction cavity is completed through strict simulation design and optimization of the structural form, material selection, and spatial size. It is an extinction cavity with extremely strong extinction ability in a limited space for large-aperture parallel outgoing light. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a structural schematic diagram of an embodiment of a device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to the present invention;

[0050] Figure 2 Schematic diagram of the structure of the extinction cavity in the embodiment of the present invention.

[0051] Figure Number:

[0052] 1-laser source, 2-collimating mirror, 3-chopper, 4-semi-transparent and semi-reflective mirror, 5-detector, 6-light shield, 7-first high-reflective mirror, 8-absorption cavity, 9-extinction cavity, 91-first cylindrical section, 92-second cylindrical section, 93-third cylindrical section, 94-fourth cylindrical section, 95-second high-reflective mirror, 96-third high-reflective mirror, 97-fourth high-reflective mirror, 10-low-pressure cavity, 11-telescope to be tested. DETAILED DESCRIPTION

[0053] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] An embodiment of the present invention provides a device for measuring backscattered light of a space-borne telescope based on gravitational wave detection, such as Figure 1 As shown, the device mainly includes five parts: beam preparation module, extinction cavity 9, detection module and environmental protection module, etc. The onboard telescope is the telescope to be tested 11, which is an off-axis four-mirror telescope system composed of a primary mirror M1, a secondary mirror M2, a third mirror M3 and a fourth mirror M4.

[0055] The function of the beam preparation module is to provide a high-power collimated beam with high uniformity for the measurement of the backscattered light of the space-borne telescope, and mainly includes laser 1, collimator 2, chopper 3 and semi-transparent and semi-reflective mirror 4. Since the backscattered light intensity of the telescope 11 to be measured is extremely low, a high-power laser is used as the light source to achieve accurate measurement of the signal. However, excessive laser power will cause thermal effects and generate thermal noise during measurement, which will affect the results. Therefore, this embodiment uses a fiber continuous light laser with a power of 10W or more as the light source; the function of the collimator 2 is to collimate the laser beam. When designing, it is important to match the size of the entrance pupil of the telescope 11 to be tested to avoid excessive light energy from forming stray light; the function of the semi-transparent and semi-reflective mirror 4 is to allow the collimated laser beam to be incident on the telescope 11 to be tested, and at the same time, allow the backscattered light of the telescope 11 to be received by the detector 5 after being folded 90°. Since there is residual reflection on its anti-reflection surface, a light trap is set on the optical path where the first reflected light reflected by the anti-reflection surface is located. The light trap includes a first high-reflection mirror 7 and an absorption cavity 8 to reduce the influence of the anti-reflection surface reflected light on the detection accuracy of the system. In order to reduce the scattered light generated by the semi-transparent and semi-reflective mirror 4, the semi-transparent and semi-reflective mirror 4 is processed by ultra-smooth processing, and its roughness is less than or equal to 0.1nm.

[0056] like Figure 2As shown, the extinction cavity 9 includes a first cylindrical section 91, a second cylindrical section 92, a third cylindrical section 93, and a fourth cylindrical section 94 which are connected in sequence; the central axes of the first cylindrical section 91 and the second cylindrical section 92 are perpendicular to each other; a second high-reflection mirror 95 is provided on the inner wall at the connection point of the first cylindrical section 91 and the second cylindrical section 92; the included angles between the second high-reflection mirror 95 and the central axes of the first cylindrical section 91 and the second cylindrical section 92 are both 45°; the central axes of the second cylindrical section 92 and the third cylindrical section 93 are perpendicular to each other; a third high-reflection mirror 96 is provided on the inner wall at the connection point of the second cylindrical section 92 and the third cylindrical section 93; the included angles between the third high-reflection mirror 96 and the central axes of the second cylindrical section 92 and the third cylindrical section 93 are both 45°; the central axes of the third cylindrical section 93 and the fourth cylindrical section 94 are perpendicular to each other; a fourth high-reflection mirror 97 is provided on the inner wall at the connection point of the third cylindrical section 93 and the fourth cylindrical section 94. The fourth high-reflection mirror 97 and the central axis angles of the third cylindrical section 93 and the fourth cylindrical section 94 are all 45°. The function of the extinction cavity 9 is to absorb the large-aperture parallel light beam passing through the telescope 11 to be tested, ensuring that the outgoing light emitted from the telescope 11 to be tested cannot be scattered to the detector 5 through the inner wall of the box or the surface of the structure to form background stray light. The traditional extinction cavity uses extinction black paint to absorb light, but because the surface of the black paint is relatively rough, there is a lot of scattering, resulting in a large amount of backscattered light from the inner wall of the extinction cavity returning to the telescope. After these scattered lights reach the detector, they form stray light, affecting the measurement accuracy of the detection system. The traditional extinction cavity has a simple structure and weak extinction ability, and cannot be directly applied to the measurement of backscattered light of the satellite telescope involved in this embodiment. This embodiment adopts a combination of "optical and mechanical combination", using the advantages of optical ultra-smooth processing to reduce the backscattering of the surface, combined with the high absorption characteristics of the extinction black paint, the structural form, material selection and spatial size of the extinction cavity are simulated and optimized. This extinction cavity is a parallel transmission light extinction cavity with a large aperture and extremely strong extinction capability in a limited space. The second high-reflection mirror 95, the third high-reflection mirror 96 and the fourth high-reflection mirror 97 are processed super-smoothly with a roughness of 0.15nm, and the other inner surfaces are sprayed with aerospace extinction black paint with an absorption rate of up to 99%.

[0057] The detection module mainly includes a detector 5 and electronic components such as a phase-locked amplifier, and its function is to achieve high-precision measurement of the backscattered light of the telescope 11 to be tested; this embodiment uses phase-locked detection to eliminate the influence of noise and stray light, and achieves high-sensitivity detection of extremely weak light signals. This embodiment uses a photoelectric detector with a very large dynamic range detection capability, and its gain range is 10 3 ~10 8 , the limit detection capability is less than or equal to 10 -10 Magnitude.

[0058] The environmental protection module mainly includes a low-pressure cavity 10, a light shield 6, a light trap and a light shielding cloth; the function of the environmental protection module is to reduce the influence of the airflow and mirror scattering of the entire measuring device on the measurement accuracy of stray light. The environmental protection module of this embodiment mainly includes two parts: a low-pressure environment and a light shielding device in the measurement system. According to theoretical calculations, it is necessary to use a hundred-level low-pressure cavity 10 to meet the measurement requirements of the backscattered light of the telescope 11 to be measured. In order to reduce the scattered stray light of the optical mirror in the beam preparation system, a light trap including a first high-reflection mirror 7 and an absorption cavity 8 is set on the light path of the anti-reflection surface reflection light of the semi-transparent semi-reflective mirror 4 to reduce the influence of the anti-reflection surface reflection light (i.e., the first reflection light) of the semi-transparent semi-reflective mirror 4 on the detection accuracy of the system. A light shield 6 is added at the branch position between the semi-transparent semi-reflective mirror 4 and the detector 5 to reduce the influence on the detection result. During measurement, the control device is covered with a matte black cloth to prevent the control device from generating background stray light.

[0059] The working principle of the device is as follows: the laser 1 emits a measuring light which forms a parallel light beam after passing through the collimator 2, and the light frequency is modulated by the chopper 3. The collimated light beam is transmitted through the semi-transparent and semi-reflective mirror 4 and enters the telescope 11 to be tested, and the beam is expanded by the telescope 11 to form a large-caliber parallel light beam (i.e., the output light) which is absorbed by the extinction cavity 9. Due to the roughness scattering and film scattering of the surface of the telescope 11 to be tested, there are backscattered light rays on the mirror surface of the telescope 11 to be tested. These light rays return along the original path and are deflected 90° by the beam splitting reflection surface of the semi-transparent and semi-reflective mirror 4 to be received by the detector 5. Since there is still residual reflection on the anti-reflection surface of the semi-transparent and semi-reflective mirror 4, a light trap composed of a first high-reflective mirror 7 and an absorption cavity 8 is set on the optical path of the first reflected light thereof, and the light trap is used to absorb the mirror reflected light of the transmission surface to avoid errors. At the same time, when performing signal detection, a detector with a high dynamic range is used, and a phase-locked amplifier is used to extract the backscattered light of the telescope 11 to be measured. By synchronizing the phase and frequency of the electrical signal with the modulation frequency of the chopper 3, high-sensitivity extraction of the backscattered signal to be measured is achieved. The specific steps are as follows:

[0060] Step 1: placing the above-mentioned satellite telescope backscattered light measurement device based on gravitational wave detection and the telescope to be tested 11 in a low-pressure cavity 10;

[0061] Step 2, the laser source 1 emits a measuring light, which is collimated by the collimator 2, and then frequency modulated by the chopper 3, and then divided into a transmitted light and a first reflected light by the semi-transparent and semi-reflective mirror 4. After the transmitted light enters the telescope 11 to be measured, an outgoing light and a backscattered light are generated; the first reflected light is reflected by the first high-reflective mirror 7 to the absorption cavity 8, and the absorption cavity 8 absorbs the first reflected light;

[0062] Step 3, the outgoing light is emitted from the telescope 11 to be tested to the extinction cavity 9, and the extinction cavity 9 extincts it; the backscattered light is then reflected by the semi-transparent and semi-reflective mirror 4 to form a second reflected light that enters the detector 5;

[0063] Step 4: The detector 5 receives the second reflected light, converts it into an electrical signal and sends it to the phase-locked amplifier. The phase-locked amplifier synchronizes the phase and frequency of the electrical signal with the modulation frequency of the chopper 3 to extract the backscattered light measurement result of the telescope 11 to be measured.

[0064] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A device for measuring backscattered light of a space-borne telescope based on gravitational wave detection, characterized in that: It comprises a laser source (1), a collimator (2), a semi-transparent and semi-reflective mirror (4), a detector (5) and a phase-locked amplifier arranged at the incident end of the telescope (11) to be tested, and an extinction cavity (9) arranged at the output end of the telescope (11) to be tested; The laser source (1) is used to emit measurement light to the telescope (11) to be measured; The collimator (2) is arranged on the optical path where the measuring light is located, and its size matches the entrance pupil size of the telescope (11) to be measured, and is used to collimate the measuring light; The semi-transparent and semi-reflective mirror (4) is arranged on the optical path between the collimating mirror (2) and the incident end of the telescope to be measured (11), and is used to separate the measuring light into transmitted light and first reflected light, wherein the transmitted light generates outgoing light and backscattered light after entering the telescope to be measured (11), the outgoing light is emitted from the outgoing end of the telescope to be measured (11), and the backscattered light is emitted from the incident end of the telescope to be measured (11); the semi-transparent and semi-reflective mirror (4) is also used to reflect the backscattered light to form second reflected light; The detector (5) is arranged on the optical path where the second reflected light is located, and is used to detect the second reflected light and convert the second reflected light into an electrical signal; The input end of the phase-locked amplifier is connected to the output end of the detector (5) and is used to receive an electrical signal to extract the measurement result of the backscattered light of the telescope (11) to be measured; The extinction cavity (9) is used to extinct the outgoing light after passing through the telescope (11) to be measured.

2. The device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 1, characterized in that: Also included is a light trap disposed on the light path where the first reflected light is located; The light trap comprises a first high-reflection mirror (7) and an absorption cavity (8); The first high-reflection mirror (7) is used to reflect the first reflected light to the absorption cavity (8); The absorption cavity (8) is used for absorbing the first reflected light.

3. The device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 1 or 2, characterized in that: Also includes a chopper (3); The chopper (3) is arranged on the optical path between the collimating mirror (2) and the semi-transparent and semi-reflective mirror (4) and is used to modulate the frequency of the collimated measurement light to improve the acquisition signal-to-noise ratio.

4. The device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 3, characterized in that: Also includes a light shield (6); The light shield (6) is arranged on the periphery of the second reflected light.

5. The device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 4, characterized in that: The extinction cavity (9) comprises a first cylindrical segment (91), a second cylindrical segment (92), a third cylindrical segment (93), and a fourth cylindrical segment (94) which are connected in sequence; The central axes of the first cylindrical section (91) and the second cylindrical section (92) are perpendicular to each other; a second high-reflection mirror (95) is provided on the inner wall of the connection between the first cylindrical section (91) and the second cylindrical section (92); The central axes of the second cylindrical section (92) and the third cylindrical section (93) are perpendicular to each other; a third high-reflection mirror (96) is provided on the inner wall of the connection between the second cylindrical section (92) and the third cylindrical section (93); The central axes of the third cylindrical section (93) and the fourth cylindrical section (94) are perpendicular to each other; a fourth high-reflection mirror (97) is provided on the inner wall of the connection between the third cylindrical section (93) and the fourth cylindrical section (94).

6. The device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 5, characterized in that: The inner surfaces of the first cylindrical section (91), the second cylindrical section (92), the third cylindrical section (93), and the fourth cylindrical section (94) are all sprayed with aerospace matte black paint; The second high-reflection mirror (95), the third high-reflection mirror (96) and the fourth high-reflection mirror (97) are all processed by ultra-smooth processing, and the roughness is less than or equal to 0.15nm.

7. The device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 6, characterized in that: It also includes a low-pressure cavity (10), the interior of which is a 100-level low-pressure environment; The laser source (1), the collimating mirror (2), the chopper (3), the semi-transparent and semi-reflective mirror (4), the detector (5), the light shield (6) and the extinction cavity (9) are all arranged in a low-pressure cavity (10).

8. The device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 7, characterized in that: The semi-transparent and semi-reflective mirror (4) is processed by ultra-smooth processing, and the roughness is less than or equal to 0.1nm; The laser source (1) is a fiber continuous light laser with a power of 10W or more; The detector (5) is a photoelectric detector with a gain range of 10 3 ~10 8 , the limit detection capability is less than or equal to 10 -10 Magnitude.

9. A method for measuring backscattered light of a space-borne telescope based on gravitational wave detection, using the device for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1, placing the device for measuring backscattered light of a space-borne telescope based on gravitational wave detection as described in any one of claims 1 to 8 and the telescope to be measured (11) in a low-pressure environment; Step 2, the laser source (1) emits measuring light, the measuring light is collimated by the collimator (2), and then transmitted by the semi-transparent and semi-reflective mirror (4), and the transmitted light enters the telescope to be measured (11) to generate output light and backscattered light; Step 3, the outgoing light is emitted from the telescope to be tested (11) to the extinction cavity (9), and the extinction cavity (9) extincts the outgoing light; The backscattered light is then reflected by a semi-transparent and semi-reflective mirror (4) to form second reflected light that enters a detector (5); Step 4: The detector (5) receives the second reflected light, converts it into an electrical signal, and outputs it to a phase-locked amplifier to obtain a backscattered light measurement result of the telescope (11) to be tested.

10. The method for measuring backscattered light of a space-borne telescope based on gravitational wave detection according to claim 9, characterized in that: Step 1 specifically comprises placing the device for measuring backscattered light of a space-borne telescope based on gravitational wave detection as described in any one of claims 1 to 8 and the telescope to be measured (11) in a low-pressure cavity (10); Specifically, step 2 comprises the following steps: a laser source (1) emits measuring light, the measuring light is collimated by a collimator (2), and then frequency modulated by a chopper (3), and then divided into transmitted light and first reflected light by a semi-transparent and semi-reflective mirror (4); the transmitted light enters the telescope to be measured (11) to generate output light and backscattered light; the first reflected light is reflected by a first high-reflective mirror (7) to an absorption cavity (8), and the absorption cavity (8) absorbs the first reflected light; Step 4 specifically includes that the detector (5) receives the second reflected light, converts it into an electrical signal and sends it to a phase-locked amplifier, and the phase-locked amplifier synchronizes the phase and frequency of the electrical signal with the modulation frequency of the chopper (3) to extract the backscattered light measurement result of the telescope (11) to be tested.

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