Spaceborne telescope backscattered light measuring device and method based on gravitational wave detection

Abstract

The application discloses a kind of based on gravitational wave detection's satellite-borne telescope backscattering light measuring device and method, solve the problem that traditional stray light measuring device cannot measure satellite-borne telescope backscattering light in gravitational wave detection system, specifically includes the laser source being arranged in the incident end of the telescope to be measured, collimating mirror, half-transmission half-reflection mirror, detector and phase-locked amplifier, and extinction chamber being arranged in the exit end of the telescope to be measured;Laser source emits measuring light;Collimating mirror collimates measuring light;Half-transmission half-reflection mirror divides collimated measuring light into transmitted light and first reflected light, wherein transmitted light enters telescope to be measured and generates exit light and backscattering light;Half-transmission half-reflection mirror is also used to reflect backscattering light, form second reflected light;Detector detects second reflected light;Phase-locked amplifier input end is connected with detector output end to receive measured electrical signal;Extinction chamber is used to extinguish exit light after telescope to be measured.

Description

TECHNICAL FIELD

[0001] The present application relates to a scattering light measuring device and method, and in particular to a kind of based on gravitational wave detection satellite telescope backscattering light measuring device and method. BACKGROUND

[0002] Since gravitational waves are directly observed, gravitational wave detection has made a series of major progress. To ensure the detection accuracy of space gravitational waves, a Michelson laser interferometer with an arm length of several hundred or several million kilometers in the form of an equilateral triangle will be established in space. When the laser beam intersects, an interference signal will be generated in the interferometer when a space gravitational wave passes through, causing a slight deformation of the interferometer arm. By analyzing the intensity and frequency of the interference signal, the existence and frequency characteristics of the gravitational wave can be determined, thereby studying the characteristics of celestial bodies, such as black hole merging and neutron star collision.

[0003] The satellite telescope is a key component of the gravitational wave detection system, which functions to transmit and receive signal beams. To achieve high-precision detection of gravitational waves, it is necessary to ensure that the signal beam received by the satellite telescope is not obscured by the backscattering stray light of the satellite telescope itself when passing through the interferometer arm. According to theoretical calculations, the background stray light of the satellite telescope needs to be less than 10 -10 The traditional stray light measuring device mainly includes two types: a VGI (Vignetting and Intensity) measuring device and a PST (Point Source Transmittance) testing device. The VGI measuring device mainly tests the overall stray light suppression capability of the optical-mechanical system, while the PST measuring device mainly tests the stray light suppression capability of the optical-mechanical system at various off-axis field angles. Unlike traditional stray light measuring devices, the stray light in the gravitational wave detection system mainly comes from the backscattering light of the mirror surface caused by insufficient mirror surface roughness and low coating efficiency. Traditional stray light measuring devices cannot measure the backscattering stray light in the gravitational wave telescope system. SUMMARY

[0004] To solve the technical problem that traditional stray light measuring devices cannot measure the backscattering light of the satellite telescope in the gravitational wave detection system, the present application provides a kind of based on gravitational wave detection satellite telescope backscattering light measuring device and method.

[0005] To achieve the above purpose, the present application adopts the following technical solutions:

[0006] A kind of based on gravitational wave detection satellite telescope backscattering light measuring device, its speciality is: including the laser source, collimating mirror, half-mirror, detector and phase-locked amplifier arranged in the incident end of the telescope to be measured, and the extinction cavity arranged in the exit end of the telescope to be measured;

[0007] The laser source is used for emitting measuring light to the telescope to be measured;

[0008] The collimating mirror is arranged on an optical path of the measuring light, and has a size matched with an entrance pupil size of the telescope to be measured, and is used for collimating the measuring light;

[0009] The half-mirror is arranged on an optical path between the collimating mirror and the telescope to be measured, and is used for dividing the measuring light into transmitted light and first reflected light, wherein the transmitted light enters the telescope to be measured to generate outgoing light and backscattered light, the outgoing light is emitted from an exit end of the telescope to be measured, and the backscattered light is emitted from an entrance end of the telescope to be measured; and the half-mirror is also used for reflecting the backscattered light to form second reflected light;

[0010] The detector is arranged on an optical path of the second reflected light, and is used for detecting the second reflected light and converting the second reflected light into an electrical signal;

[0011] The lock-in amplifier is connected with an output end of the detector, and is used for receiving the electrical signal to extract a measurement result of the backscattered light of the telescope to be measured;

[0012] The light extinction cavity is used for extinguishing the outgoing light after the telescope to be measured.

[0013] Further, the apparatus further comprises a light trap arranged on an optical path of the first reflected light;

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

[0015] The first high-reflectivity mirror is used for reflecting the first reflected light to the absorption cavity;

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

[0017] Further, the apparatus further comprises a chopper;

[0018] The chopper is arranged on an optical path between the collimating mirror and the half-mirror, and is used for frequency-modulating the collimated measuring light to improve a signal-to-noise ratio of the collected light.

[0019] Further, the apparatus further comprises a light shield;

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

[0021] Further, the light 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 first cylindrical segment and the second cylindrical segment are perpendicular to each other, and a second high-reflectivity mirror is arranged on an inner wall at a connection between the first cylindrical segment and the second cylindrical segment;

[0023] The central axes of the second cylinder segment and the third cylinder segment are perpendicular to each other; and a third high-reflectivity mirror is arranged on the inner wall at the joint of the second cylinder segment and the third cylinder segment.

[0024] The central axes of the third cylinder segment and the fourth cylinder segment are perpendicular to each other; and a fourth high-reflectivity mirror is arranged on the inner wall at the joint of the third cylinder segment and the fourth cylinder segment.

[0025] Further, the inner surfaces of the first cylinder segment, the second cylinder segment, the third cylinder segment and the fourth cylinder segment are all sprayed with space light-absorbing black paint.

[0026] The second high-reflectivity mirror, the third high-reflectivity mirror and the fourth high-reflectivity mirror are all super-smoothly machined, with a roughness less than or equal to 0.15 nm.

[0027] Further, a low-pressure cavity is further included, and the interior of the low-pressure cavity is a hundred-level low-pressure environment.

[0028] The laser source, the collimating mirror, the chopper, the half-transmitting half-reflecting mirror, the detector, the light shield and the light-absorbing cavity are all arranged in the low-pressure cavity.

[0029] Further, the half-transmitting half-reflecting mirror is super-smoothly machined, with a roughness less than or equal to 0.1 nm.

[0030] The laser source is a fiber continuous light laser with a power greater than or equal to 10 W.

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

[0032] A star-borne telescope backscattered light measurement method based on gravitational wave detection, which adopts the star-borne telescope backscattered light measurement device based on gravitational wave detection, and has the particularity that the method comprises the following steps:

[0033] Step 1, placing the star-borne telescope backscattered light measurement device based on gravitational wave detection and the to-be-measured telescope in a low-pressure environment.

[0034] Step 2, the laser source emits measurement light, the measurement light is collimated by the collimating mirror, and then transmitted by the half-transmitting half-reflecting mirror, and the transmitted light enters the to-be-measured telescope to generate outgoing light and backscattered light;

[0035] Step 3, the outgoing light is emitted from the to-be-measured telescope to the light-absorbing cavity, and the light-absorbing cavity absorbs the outgoing light; the backscattered light is reflected by the half-transmitting half-reflecting mirror again to form second reflected light which enters the detector.

[0036] Step 4, after the detector receives the second reflected light and converts it into an electrical signal, the electrical signal is output to the phase-locked amplifier to obtain the backscattering light measurement result of the telescope to be measured.

[0037] Further, step 1 is specifically placing the above-mentioned satellite-borne telescope backscattering light measurement device based on gravitational wave detection and the telescope to be measured in a low-pressure cavity.

[0038] Step 2 is specifically that the laser source emits measurement light, the measurement light is collimated by the collimating mirror, and then the frequency of the chopper is adjusted, and the measurement light is divided into transmitted light and first reflected light by the half-transmission half-reflection mirror; the transmitted light enters the telescope to be measured to generate outgoing light and backscattering light; the first reflected light is reflected by the first high-reflection mirror to the absorption cavity, and the absorption cavity absorbs the first reflected light.

[0039] Step 4 is specifically that the detector receives the second reflected light and converts it into an electrical signal, and the electrical signal is sent to the phase-locked amplifier; the phase-locked amplifier synchronizes the electrical signal with the modulation frequency of the chopper in phase and frequency to extract the backscattering light measurement result of the telescope to be measured.

[0040] The beneficial effects of the present application are:

[0041] 1. The satellite-borne telescope backscattering light measurement device and method based on gravitational wave detection provided by the present application sets a half-transmission half-reflection mirror and a detector for the telescope to be measured; the half-transmission half-reflection mirror can reflect the backscattering light to the detector for measurement, the extinction cavity can absorb the large-diameter parallel light beam passing through the telescope to be measured, and it is ensured that the outgoing light from the telescope to be measured cannot be scattered to the detector through the inner wall or structure surface of the box to form background stray light, thereby avoiding affecting the measurement result and greatly improving the measurement precision.

[0042] 2. The present application sets an optical trap on the light path of the first reflected light, which can absorb the first reflected light to avoid affecting the backscattering light measurement precision, and further improve the backscattering light measurement precision.

[0043] 3. The present application further sets a chopper between the collimating mirror and the half-transmission half-reflection mirror, which can modulate the received measurement laser into a fixed-frequency incident light signal; finally, the phase-locked amplifier finds and extracts the fixed-frequency light signal in the output signal of the detector, which can greatly improve the signal-to-noise ratio, reduce environmental interference, and improve the measurement precision of the backscattering light.

[0044] 4. The present application sets a light shield around the second reflected light, which can avoid the influence of other external light on the reflected light of the backscattering light, reduce environmental interference, and improve the measurement precision of the backscattering light.

[0045] 5. The extinction cavity provided by the application, the second high-reflectivity mirror, the third high-reflectivity mirror and the fourth high-reflectivity mirror use super-smooth processing, and the roughness is less than or equal to 0.15 nm, the inner surfaces of the first cylinder segment, the second cylinder segment, the third cylinder segment and the fourth cylinder segment are sprayed with space extinction black paint, and the absorption rate can reach 99%.

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

[0047] 7. Since the light intensity of backscattered light is extremely low, the laser source provided by the application is a 10W fiber continuous light laser, which can provide high-power measurement light and will not cause thermal effects, thereby ensuring the measurement accuracy.

[0048] 8. The star-borne telescope backscattered light measurement device and method based on gravitational wave detection provided by the application solve the stray light test problem caused by the star-borne telescope backscattered light in gravitational wave measurement. The application is different from the traditional stray light coefficient test device and the point source transmittance test device, and the core is to directly measure the backscattered light of the star-borne telescope with high precision, which is essentially a new type of stray light test device. The extinction cavity is completed through strict simulation design and optimization of the structure form, material selection and spatial size, and is an extinction cavity with strong extinction ability in a limited space and for large-diameter parallel outgoing light. BRIEF DESCRIPTION OF DRAWINGS

[0049] Figure 1 is a structural schematic diagram of an embodiment of the star-borne telescope backscattered light measurement device based on gravitational wave detection provided by the application;

[0050] Figure 2 is a structural schematic diagram of the extinction cavity in the embodiment of the application.

[0051] REFERENCE NUMERALS:

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

[0053] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] This invention provides a spaceborne telescope backscattering light measurement device based on gravitational wave detection, such as... Figure 1 As shown, the device mainly consists of five parts: a beam preparation module, an extinction cavity 9, a detection module, and an environmental support module. The spaceborne telescope is the telescope under test 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 beam preparation module is designed to provide a highly uniform, high-power collimated beam for measuring backscattered light from the spaceborne telescope. It mainly consists of a laser 1, a collimating mirror 2, a chopper 3, and a semi-transparent mirror 4. Because the backscattered light from the telescope under test 11 has extremely low intensity, a high-power laser is used as the light source to achieve accurate signal measurement. However, excessively high laser power can lead to thermal effects and generate thermal noise during measurement, which can affect the results. Therefore, this embodiment uses a fiber continuous light laser of 10W or higher as the light source. The collimating lens 2 is used to collimate the laser beam. During design, it is important to match the entrance pupil size of the telescope under test 11 to avoid excessive light energy forming stray light. The semi-transparent mirror 4 is used to direct the collimated laser beam into the telescope under test 11, and simultaneously redirects the backscattered light from the telescope under test 11 by 90° to the detector 5. Since its anti-reflection surface also has residual reflections, an optical trap is set in the optical path of the first reflected light from the anti-reflection surface. The optical trap includes a first high-reflection mirror 7 and an absorption cavity 8 to reduce the impact of the reflected light from the anti-reflection surface on the system's detection accuracy. To reduce the scattered light generated by the semi-transparent mirror 4, it is manufactured with an ultra-smooth surface, with a roughness of less than or equal to 0.1 nm.

[0056] like Figure 2As shown, the extinction cavity 9 includes first, second, third and fourth cylindrical segments 91, 92, 93 and 94 connected in sequence; the central axes of the first and second cylindrical segments 91 and 92 are perpendicular to each other; the inner wall at the connection between the first and second cylindrical segments 91 and 92 is provided with a second high-reflectivity mirror 95; the angle between the second high-reflectivity mirror 95 and the central axis of the first and second cylindrical segments 91 and 92 is 45°; the central axes of the second and third cylindrical segments 92 and 93 are perpendicular to each other; the inner wall at the connection between the second and third cylindrical segments 92 and 93 is provided with a third high-reflectivity mirror 96; the angle between the third high-reflectivity mirror 96 and the central axis of the second and third cylindrical segments 92 and 93 is 45°; the central axes of the third and fourth cylindrical segments 93 and 94 are perpendicular to each other; the inner wall at the connection between the third and fourth cylindrical segments 93 and 94 is provided with a fourth high-reflectivity mirror 97. The angle between the fourth high-reflectivity mirror 97 and the central axis of the third and fourth cylindrical segments 93 and 94 is 45°. The function of the extinction cavity 9 is to absorb the large-diameter parallel light beam passing through the to-be-measured telescope 11, to ensure that the outgoing light from the to-be-measured telescope 11 cannot be scattered to the detector 5 through the inner wall or the structure surface of the box, thereby forming background stray light. The traditional extinction cavity uses extinction black paint to realize absorption of light, but due to the rough surface of the black paint, there is a large amount of scattering, resulting in a large amount of backscattered light returning to the telescope from the inner wall of the extinction cavity. When this scattered light reaches the detector, it forms stray light, which affects the measurement accuracy of the detection system. The traditional extinction cavity has a simple structure and weak extinction capability, and cannot be directly applied to the measurement of the backscattered light of the spaceborne telescope involved in the embodiment. The embodiment adopts a combination of "optics and mechanism", uses the advantages of optical super-smooth machining to reduce the backscattering of the surface, and combines the high absorption characteristics of the extinction black paint to simulate, design and optimize the structure form, material selection and spatial size of the extinction cavity. The extinction cavity is a large-diameter extinction cavity with strong extinction capability in a limited space. The second, third and fourth high-reflectivity mirrors 95, 96 and 97 are super-smoothly machined, with a roughness of 0.15 nm, and the remaining inner surfaces are sprayed with space extinction black paint, with an absorption rate of up to 99%.

[0057] The detection module mainly includes a detector 5 and a phase-locked amplifier and other electronic components, and its function is to realize high-precision measurement of the backscattered light of the to-be-measured telescope 11; the embodiment uses phase-locked detection to eliminate the influence of noise and stray light, and realizes high-sensitivity detection of extremely weak light signals. The photoelectric detector used in the embodiment has a very large dynamic range detection capability, with a gain range of 10 3 ~ 10 8 , and an ultimate detection capability less than or equal to 10 -10 orders of magnitude.

[0058] The environmental protection module mainly comprises a low-pressure cavity 10, a light shield 6, a light trap and a light shielding cloth, etc. The function of the environmental protection module is to reduce the influence of air flow and mirror surface scattering of the whole measuring device on the stray light measuring accuracy. The environmental protection module of the embodiment mainly comprises two parts: a low-pressure environment and a light shielding device in the measuring system. According to theoretical calculation, a hundred-level low-pressure cavity 10 is needed to meet the measuring requirements of the backscattered light of the measured telescope 11. In order to reduce the scattered stray light of the optical mirror in the light beam preparation system, a light trap comprising a first high-reflective mirror 7 and an absorption cavity 8 is arranged on the light path of the anti-reflection surface reflected light of the semi-transparent mirror 4, so as to reduce the influence of the anti-reflection surface reflected light of the semi-transparent mirror 4 on the system detection accuracy. The light shield 6 is added at the position of the semi-transparent mirror 4 and the detector 5 branch, so as to reduce the influence on the detection result. The light shielding black cloth is covered on the controller during the measurement, so as to avoid the background stray light generated by the controller.

[0059] The working principle of the device is as follows: the laser 1 emits measuring light which forms a parallel light beam after collimating by the collimating mirror 2. The light frequency is modulated by the chopper 3. The collimated light beam transmits through the semi-transparent mirror 4 and enters the measured telescope 11. The light beam is expanded by the measured telescope 11 to form a large-aperture parallel light beam (i.e. the outgoing light) which is absorbed by the light absorption cavity 9. Due to the roughness scattering and film layer scattering of the surface of the measured telescope 11, the backscattered light exists on the surface of the measured telescope 11. These light rays return along the original path, are folded by 90° by the light splitting reflection surface of the semi-transparent mirror 4, and are received by the detector 5. Since the anti-reflection surface of the semi-transparent mirror 4 still has residual reflection, a light trap composed of a first high-reflective mirror 7 and an absorption cavity 8 is arranged on the light path of the first reflected light, so as to absorb the mirror reflected light of the transmission surface and avoid causing errors. At the same time, a high dynamic range detector is used for signal detection, and a lock-in amplifier is used to extract the backscattered light of the measured telescope 11. The phase and frequency of the electrical signal are synchronized with the modulation frequency of the chopper 3, so as to realize high-sensitivity extraction of the measured backscattered signal. The specific steps are as follows:

[0060] Step 1: Place the above-described star-borne telescope backscattered light measuring device based on gravitational wave detection and the measured telescope 11 in the low-pressure cavity 10.

[0061] Step 2: The laser source 1 emits measuring light. The measuring light is collimated by the collimating mirror 2, and then the frequency is modulated by the chopper 3. The measuring light is divided into transmitted light and first reflected light by the semi-transparent mirror 4. The transmitted light enters the measured telescope 11 to generate outgoing light and backscattered light. 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 from the telescope 11 to be measured exits to the light extinction cavity 9, which performs light extinction on it; the backscattered light is reflected by the half-transmission half-reflection mirror 4 again to form second reflected light into the detector 5;

[0063] Step 4, the detector 5 receives the second reflected light and converts it into an electrical signal to send to the lock-in amplifier, which synchronizes the electrical signal with the modulation frequency of the chopper 3 in phase and frequency 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 application, but the protection scope of the present application is not limited to this, any change or replacement within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A space-borne telescope backscattered light measuring device based on gravitational wave detection, characterized by: The application relates to a laser source (1), a collimating mirror (2), a half-transmitting and half-reflecting mirror (4), a detector (5) and a lock-in amplifier arranged at the incident end of a to-be-tested telescope (11), and a light extinction cavity (9) arranged at the outgoing end of the to-be-tested telescope (11). The laser source (1) is used for emitting measuring light to the to-be-tested telescope (11). The collimating mirror (2) is arranged on an optical path of the measuring light, and the size of the collimating mirror (2) matches the size of the entrance pupil of the to-be-tested telescope (11), so that the collimating mirror (2) is used for collimating the measuring light. The half-transmitting and half-reflecting mirror (4) is arranged on an optical path between the collimating mirror (2) and the incident end of the to-be-tested telescope (11), and is used for dividing the measuring light into transmitted light and first reflected light, wherein the transmitted light enters the to-be-tested telescope (11) to generate outgoing light and backscattered light, the outgoing light is emitted from the outgoing end of the to-be-tested telescope (11), and the backscattered light is emitted from the incident end of the to-be-tested telescope (11); the half-transmitting and half-reflecting mirror (4) is also used for reflecting the backscattered light to form second reflected light. The detector (5) is arranged on an optical path of the second reflected light, and is used for detecting the second reflected light and converting the second reflected light into an electric signal. The lock-in amplifier is connected with the output end of the detector (5), and is used for receiving the electric signal to extract a measurement result of the backscattered light of the to-be-tested telescope (11). The light extinction cavity (9) is used for extinguishing the outgoing light after passing through the to-be-tested telescope (11); the light extinction cavity (9) comprises first, second, third and fourth cylinder segments (91, 92, 93, 94) which are sequentially connected; the central axes of the first and second cylinder segments (91, 92) are perpendicular to each other; a second high-reflecting mirror (95) is arranged on the inner wall of the connecting position of the first and second cylinder segments (91, 92); the central axes of the second and third cylinder segments (92, 93) are perpendicular to each other; a third high-reflecting mirror (96) is arranged on the inner wall of the connecting position of the second and third cylinder segments (92, 93); the central axes of the third and fourth cylinder segments (93, 94) are perpendicular to each other; a fourth high-reflecting mirror (97) is arranged on the inner wall of the connecting position of the third and fourth cylinder segments (93, 94); the inner surfaces of the first, second, third and fourth cylinder segments (91, 92, 93, 94) are sprayed with space light extinction black paint; the second, third and fourth high-reflecting mirrors (95, 96, 97) are processed by super-smooth machining, and the roughness is less than or equal to 0.15 nm.

2. The gravitational wave probe based space-borne telescope backscattered light measuring apparatus according to claim 1, characterized in that: The application further comprises a light trap arranged on an optical path of the first reflected light. The light trap comprises a first high-reflecting mirror (7) and an absorbing cavity (8). The first high-reflecting mirror (7) is used for reflecting the first reflected light to the absorbing cavity (8). The absorbing cavity (8) is used for absorbing the first reflected light.

3. The gravitational wave probe based space-borne telescope backscattered light measuring apparatus according to claim 1 or 2, characterized in that: The application further comprises a chopper (3). The chopper (3) is arranged on an optical path between the collimating mirror (2) and the half-transmitting and half-reflecting mirror (4), and is used for frequency-modulating the collimated measuring light to improve the signal-to-noise ratio of collection.

4. The gravitational wave probe based space-borne telescope backscattered light measuring apparatus according to claim 3, characterized in that: The application further comprises a light shield (6). The light shield (6) is arranged at the periphery of the second reflected light.

5. The gravitational wave probe based space-borne telescope backscattered light measuring apparatus according to claim 4, characterized in that: Further comprising a low pressure cavity (10) with a hundred-level low pressure environment inside; The laser source (1), the collimating mirror (2), the chopper (3), the half-mirror (4), the detector (5), the light shield (6) and the extinction cavity (9) are all arranged in the low pressure cavity (10).

6. The gravitational wave probe based space-borne telescope backscattered light measuring apparatus according to claim 5, characterized in that: The half-mirror (4) is super-smoothly machined with a roughness less than or equal to 0.1 nm; The laser source (1) is a fiber continuous light laser with a power greater than or equal to 10 W; The detector (5) is a photodetector with a gain range of 10 3 10 8 orders of magnitude and a limit of detection less than or equal to 10 -10 orders of magnitude.

7. 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 1-6, characterized in that, The method comprises the following steps: Step 1: placing the space telescope backscattering light measurement device based on gravitational wave detection according to any one of claims 1-6 and the telescope to be measured (11) in a low pressure environment; Step 2: the laser source (1) emits measurement light, the measurement light is collimated by the collimating mirror (2), then transmitted by the half-mirror (4), and the transmitted light enters the telescope to be measured (11) to generate outgoing light and backscattering light; Step 3: the outgoing light is emitted from the telescope to be measured (11) to the extinction cavity (9), and the extinction cavity (9) performs extinction on the outgoing light; The backscattering light is reflected by the half-mirror (4) again to form the second reflected light entering the detector (5); Step 4: the detector (5) receives the second reflected light, converts it into an electrical signal, and outputs it to the lock-in amplifier to obtain the backscattering light measurement result of the telescope to be measured (11).

8. The space telescope backscattering light measurement method based on gravitational wave detection according to claim 7, characterized in that: Step 1 specifically places the space telescope backscattering light measurement device based on gravitational wave detection according to any one of claims 1-6 and the telescope to be measured (11) in the low pressure cavity (10); Step 2 specifically that the laser source (1) emits measurement light, the measurement light is collimated by the collimating mirror (2), then is frequency-modulated by the chopper (3), and is divided by the half-mirror (4) into transmitted light and first reflected light, the transmitted light enters the telescope to be measured (11) to generate outgoing light and backscattering light; the first reflected light is reflected by the first high reflector (7) to the absorption cavity (8), and the absorption cavity (8) absorbs the first reflected light; Step 4 specifically that the detector (5) receives the second reflected light, converts it into an electrical signal, and sends it to the lock-in amplifier, and the lock-in amplifier synchronizes the electrical signal with the modulation frequency of the chopper (3) in phase and frequency to extract the backscattering light measurement result of the telescope to be measured (11).

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