A device and method for evaluating backscattering of laser gyroscope mirrors

Abstract

This invention belongs to the field of laser gyroscope technology and relates to a device and method for evaluating the backscattering of a laser gyroscope reflector. The device includes: a laser source, an aperture, an off-axis parabolic reflector with a hole, an aperture, a controller, a rotating stage, a light trap, a sample fixture, and a light trap. An aperture is installed in the direction of the laser beam emitted by the laser source to control the diameter of the output beam. An off-axis parabolic reflector with a hole is installed after the laser beam. The laser beam passes through its central hole and the aperture before being incident on the surface of the reflector sample to be tested. The reflector sample to be tested is held by the sample fixture and placed on the rotating stage.

Description

Technical Field

[0001] This invention belongs to the field of laser gyroscope technology and relates to a device and method for evaluating the backscattering of a laser gyroscope mirror. Background Technology

[0002] Scattering of optical components in high-precision optical systems is a crucial factor affecting their accuracy, particularly in gravitational wave detectors, EUV lithography machines, high-precision spectral measurement systems, and laser gyroscopes. High-precision laser gyroscopes, as core sensors in modern inertial guidance and navigation systems, are widely used in various aircraft, ships, missiles, and armored vehicles. Improving the accuracy of laser gyroscopes is essentially a struggle against the lock-in effect, and backscattering from the laser gyroscope mirror is a significant factor influencing the lock-in region. To further enhance gyroscope accuracy, engineering efforts primarily focus on improving the precision polishing and coating processes of mirrors to reduce backscattering. The prerequisite for iterative improvements in fabrication processes and reducing mirror backscattering is accurate and rapid evaluation of the magnitude of backscattering. However, the extremely low magnitude of backscattering from ultra-smooth laser gyroscope mirrors makes light intensity detection difficult, and the problem of detector obstruction of the incident light path during backscattering measurement is unavoidable, causing the actual measured scattering angle to deviate from the expected backscattering direction.

[0003] Currently, the methods for measuring and evaluating the scattering of laser gyroscope mirrors generally employ the total integrated scattering method, the angle-resolved scattering method, and the optical modulation method. However, the total integrated scattering method, limited by its principle, can only measure the total scattering of the mirror using an integrating sphere. The total scattering measurement differs significantly from the backscattering of the mirror. Furthermore, for current ultra-smooth surface mirrors, the total integrated scattering is already less than 5 ppm, making the test accuracy insufficient for differentiation requirements and resulting in poor distinguishability between different mirrors. The angle-resolved scattering method allows for the measurement of scattering values ​​at different scattering angles, but it cannot accurately measure backscattering due to the detector blocking the incident light path. The optical modulation method is complex in principle, requires precise optical path adjustment, and is time-consuming and complex to test, with insufficient repeatability, making it difficult to apply in engineering. Summary of the Invention

[0004] The purpose of this invention is to propose a rapid backscattering evaluation method for mirrors based on scattering imaging, which has accurate testing angles, high detection efficiency, and can meet the needs of batch backscattering evaluation.

[0005] The technical solution of this invention:

[0006] On one hand, the present invention provides a laser gyroscope backscattering evaluation device, the device comprising:

[0007] 1. Laser source, Aperture A; 2. Perforated off-axis parabolic mirror, Aperture B; 3. Controller A; 4. Rotary stage; 5. Light trap A; 6. Sample fixture; 7. Light trap B; 8.

[0008] An aperture A2 is installed in the direction of the laser beam emitted by the laser source 1 to control the diameter of the output beam. A perforated off-axis parabolic reflector 3 is installed after it. The laser beam passes through its central through hole and the aperture B4 and is incident on the surface of the reflector sample to be tested. The reflector sample to be tested is held by a special fixture 8 and placed on a rotating stage 6.

[0009] The transmitted light passing through the surface of the mirror sample under test is absorbed by the light trap A7, and the reflected light reflected by the surface of the mirror sample under test is absorbed by the light trap B9. The backscattered light of the mirror sample under test is filtered out by the aperture B4 and then incident on the perforated off-axis parabolic mirror 3. The perforated off-axis parabolic mirror 3 collects the direction of the backscattered light and refracts it to the low-light imaging system. The collected image is processed, and the magnitude of the backscattered light is determined based on the image gray value.

[0010] Furthermore,

[0011] The low-light imaging system includes: objective lens 10, eyepiece 11, and low-light industrial camera 12;

[0012] The low-light imaging system is fixed on the precision stepper motor 13. The movement of the low-light imaging system is controlled by the controller B14 to ensure the image clarity. After receiving the backscattered light signal, the low-light imaging system performs noise reduction processing through the data processing computer 15, and finally reads and analyzes the image grayscale value.

[0013] Furthermore,

[0014] The bottom of the special fixture 8 is hollowed out and is connected to the rotary table 6 by a thin rod with a slot, ensuring that the mirror sample to be tested and the special fixture 8 will not slip during rotation.

[0015] Furthermore,

[0016] The interior of the rotating platform 6 is blackened.

[0017] The controller A5 controls the rotary table 6 to drive the special fixture 8 and the sample mirror to be tested to rotate, thereby realizing the automatic detection of backscattered light in nearly 360 degrees.

[0018] Furthermore,

[0019] The placement and angle of the perforated off-axis parabolic mirror 3 must ensure that the laser output from the laser can pass completely through its central aperture without being reflected from the inner sidewall of the aperture, thus affecting the detection accuracy. The mirror sample to be tested needs to be placed at the focal length of the perforated off-axis parabolic mirror 3 to ensure that the backscattered light of the mirror sample to be tested is completely received.

[0020] Furthermore,

[0021] The aperture B4 must be placed close to the sample of the mirror to be tested in order to avoid stray light being received by the perforated off-axis parabolic mirror 3.

[0022] Furthermore,

[0023] The aperture B4 can control the size of the solid angle of the backscattered light incident on the perforated off-axis parabolic mirror 3. The size of the aperture B4 can be adjusted according to specific needs to change the size of the solid angle of the backscattered light and achieve more accurate measurement.

[0024] Secondly, the present invention also provides a method for evaluating the backscattering of a laser gyroscope mirror, wherein the method is implemented using the aforementioned device, and the method steps are as follows:

[0025] Step 1: Place the mirror calibration component held by the special fixture on the rotary table, initialize the rotary table, and adjust the optical path so that the laser beam passes through the perforated off-axis parabolic mirror and is incident on the center of the mirror calibration component.

[0026] Step 2: Adjust the position and angle of light trap A and light trap B so that the reflected and transmitted light are completely absorbed by the light traps;

[0027] Step 3: Adjust the position of the low-light imaging system so that the backscattered light can be clearly imaged on the low-light industrial camera;

[0028] Step 4: Adjust the aperture of aperture B to control the solid angle of backscattered light according to the test requirements, and filter out stray light;

[0029] Step 5: After the reflector calibration components are calibrated, batch imaging detection and image storage are performed on the scattering of multiple reflector samples to be tested; the reflector samples to be tested are the same as the reflector calibration components.

[0030] Step 6: Use an image grayscale processing algorithm to denoise the imaging results of multiple mirror samples to obtain the corresponding image grayscale values ​​of multiple mirror samples. Compare the backscattered light based on the image grayscale values. The smaller the backscattered light, the better the performance of the mirror sample.

[0031] Furthermore, in step five, the scattering from multiple test mirror samples is subjected to batch imaging detection and image storage, specifically as follows:

[0032] Each mirror sample to be tested is placed on a special fixture. Controller A controls the rotary table to rotate the special fixture and the mirror sample to be tested, so as to realize the automatic detection of backscattered light of each mirror sample from nearly 360 degrees.

[0033] The beneficial effects of this invention are as follows: This invention provides a rapid evaluation method for backscattering of mirrors based on scattering imaging, enabling direct, accurate, and rapid evaluation of scattered light within a certain backscattering solid angle of a laser gyroscope mirror. After calibration of the backscattering measurement device, mirror samples can be processed in batches, and the operation is simple and quick. Using this device and method, the backscattering of different mirrors can be evaluated and compared, guiding improvements in the polishing and coating processes of ultra-smooth mirrors. Furthermore, this device and method can pre-select mirrors with lower backscattering for laser gyroscope assembly, which is significant for reducing the laser gyroscope lock-in area. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of an embodiment of the present invention, which describes a rapid evaluation method and apparatus for backscattering of a mirror based on scattering imaging.

[0035] Among them, the laser light source (1), aperture A (2), perforated off-axis parabolic mirror (3), aperture B (4), controller A (5), rotary stage (6), light trap A (7), sample special fixture (8), light trap B (9), objective lens (10), eyepiece (11), low-light industrial camera (12), precision stepper motor (13), controller B (14), and data processing computer (15).

[0036] Figure 2 This is a schematic diagram of the sample fixture (8). Detailed Implementation

[0037] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings.

[0038] The technical solution of this invention: A laser gyroscope backscattering evaluation device. It includes a laser light source 1, a low-light imaging system (low-light industrial camera 12, eyepiece and objective lens groups 10 and 11), an off-axis parabolic mirror with a hole 3, an aperture A2, an aperture B4, a light trap A7, a light trap B9, a controller A5, a controller B14, a rotating stage 6, and a sample-specific fixture 8 (such as...). Figure 2(As shown), a precision stepper motor 13, and a data processing computer 15. The output beam of the laser source 1 passes sequentially through aperture A, the light-passing hole of the perforated off-axis parabolic mirror, and aperture B before being incident on the surface of the mirror 16 under test on the rotating stage. The mirror under test is held by a special fixture. The transmitted light from the mirror surface is absorbed by light trap A, and the reflected light from the mirror surface is absorbed by light trap B. Backscattered light at a certain solid angle passes through aperture B, is collected by the off-axis parabolic mirror, and refracted into the low-light imaging system.

[0039] The focal length of the perforated off-axis parabolic mirror is 101.6 mm;

[0040] The perforated off-axis parabolic mirror is used to collect scattered light within a certain solid angle and refract the light path direction. At the same time, it can separate the low-light imaging system from the incident light path, thereby achieving accurate detection of backscattering at a certain solid angle.

[0041] The aperture B can shield and absorb stray light by controlling its position and aperture size, and the size of the measured backscatter solid angle can be controlled according to the test requirements.

[0042] The movement of the rotating stage is controlled by a controller, which can rotate the fixture and sample reflector on it 360 degrees. With the help of a special fixture design, it can realize backscatter measurement of the reflector at a near 360-degree azimuth angle.

[0043] The low-light imaging system is controlled by a precision stepper motor, which can change the imaging focal plane and control the receiver position to ensure clear imaging of the sample surface backscatter.

[0044] The low-light imaging system is connected to a data processing computer and uses a dedicated image grayscale value processing algorithm to denoise and compare the brightness of the detected image.

[0045] A rapid evaluation method for backscattering of a mirror based on scattering imaging, comprising the following steps:

[0046] Step 1: Place the reflector calibration component held by the sample fixture on the rotating stage, initialize the rotating stage, and adjust the optical path so that the laser beam passes through the perforated off-axis parabolic reflector and is incident on the center of the reflector calibration component.

[0047] Step 2: Adjust the position and angle of light trap A and light trap B so that the reflected and transmitted light are completely absorbed by the light traps;

[0048] Step 3: Adjust the position of the low-light imaging system so that the backscattered light can be clearly imaged on the low-light industrial camera;

[0049] Step 4: Adjust the aperture to control the solid angle of the scattered light according to the test requirements and filter out stray light;

[0050] Step 5: After the reflector calibration components are calibrated, batch imaging detection and image storage are performed on the scattering of the reflector samples under test; the reflector samples under test are the same as the reflector calibration components.

[0051] Step 6: Use image grayscale processing algorithms to denoise and compare the imaging results.

[0052] Example 1: See Figure 1 This is a schematic diagram of a preferred embodiment of the method of the present invention. The measuring device includes a laser light source 1, an aperture A2, a perforated off-axis parabolic mirror 3, an aperture B4, a controller A5, a rotary stage 6, a light trap A7, a sample fixture 8, a light trap B9, an objective lens 10, an eyepiece 11, a low-light industrial camera 12, a precision stepper motor 13, a controller B14, and a data processing computer 15.

[0053] An aperture A2 is installed along the beam direction emitted by the laser source 1 to control the diameter of the output beam. A perforated off-axis parabolic mirror 3 is then installed behind it. The laser beam passes through its central aperture and the aperture B4 before being incident on the surface of the high-reflectivity mirror sample. The high-reflectivity mirror sample is held in place on the rotating stage 6 by a special fixture 8. The special fixture 8 is as follows: Figure 2 As shown, the bottom surface is hollowed out and connected to the rotating stage via a thin rod with a slot, ensuring that the sample and fixture 8 will not slip during rotation. Transmitted light enters the light trap A7, thus avoiding transmitted scattered light. The interior of the rotating stage 6 is blackened, and the rotation of the reflector is controlled by the controller A5, thereby achieving automatic detection of near 360-degree backscattered light.

[0054] Transmitted light is absorbed by light trap A7, and reflected light is absorbed by light trap B9. The backscattered light from the mirror sample is filtered out by aperture B4 before being incident on the perforated off-axis parabolic mirror 3. The off-axis parabolic mirror 3 collects the direction of the backscattered light and refracts it to the low-light imaging system. The imaging system includes an objective lens 10, an eyepiece 11, and a low-light industrial camera 12. The imaging system is fixed on a precision stepper motor 13. The movement of the low-light imaging system is controlled by a controller B14 to ensure image clarity. After receiving the backscattered light signal, the imaging system performs noise reduction processing through a data processing computer 15, and finally reads and analyzes the image grayscale value. It is important to note that the placement and angle of the off-axis parabolic mirror 3 must ensure that the laser output from the laser can pass completely through its central aperture without being reflected from the inner sidewall of the aperture, thus affecting the detection accuracy. The high-reflectivity sample needs to be placed at the focal length of the off-axis parabolic mirror 3 to ensure that the backscattered light from the sample can be completely received. The placement of the aperture B4 must be as close as possible to avoid stray light being received by the apertured off-axis parabolic mirror 3, thus affecting the detection accuracy.

[0055] Example 2, see Figure 1The aperture B4 can control the size of the solid angle of the backscattered light incident on the off-axis parabolic mirror 3. According to specific needs, the size of the aperture B4 can also be adjusted to change the size of the solid angle and achieve more accurate measurement.

[0056] The device involved in this invention needs to be placed in an ultra-clean and dark environment.

[0057] This invention presents a rapid evaluation method for backscattering of mirrors based on scattering imaging. This method enables direct, accurate, and rapid evaluation of scattered light within a certain backscattering solid angle of a laser gyroscope mirror. After calibration of the backscattering measurement device, mirror samples can be processed in batches, and the operation is simple and quick. Using this device and method, the backscattering of different mirrors can be evaluated and compared, guiding improvements in the polishing and coating processes of ultra-smooth mirrors. Furthermore, this method allows for the early selection of mirrors with lower backscattering for laser gyroscope assembly, which is significant for reducing the laser gyroscope lock-in area.

Claims

1. A laser gyroscope backscattering evaluation device, characterized in that, The device includes: Laser source (1), aperture A (2), perforated off-axis parabolic mirror (3), aperture B (4), controller A (5), rotary table (6), light trap A (7), sample fixture (8), light trap B (9); An aperture A (2) is installed in the direction of the beam emitted by the laser source (1) to control the diameter of the output beam. A perforated off-axis parabolic reflector (3) is installed thereafter. The laser passes through its central through hole and the aperture B (4) and is incident on the surface of the reflector sample to be tested. The reflector sample to be tested is held by a special fixture (8) and placed on a rotating stage (6). The transmitted light passing through the surface of the mirror sample under test is absorbed by the light trap A (7), and the reflected light reflected by the surface of the mirror sample under test is absorbed by the light trap B (9). The backscattered light of the mirror sample under test is filtered out by the aperture B (4) and then incident on the perforated off-axis parabolic mirror (3). The perforated off-axis parabolic mirror (3) collects the direction of the backscattered light and refracts it to the low-light imaging system. The collected image is processed, and the magnitude of the backscattered light is determined according to the image gray value.

2. The laser gyroscope backscattering evaluation device according to claim 1, characterized in that, The low-light imaging system includes: an objective lens (10), an eyepiece (11), and a low-light industrial camera (12); The low-light imaging system is fixed on a precision stepper motor (13). The movement of the low-light imaging system is controlled by the controller B (14) to ensure the image clarity. After receiving the backscattered light signal, the low-light imaging system is denoised by the data processing computer (15) and finally the image gray value is read and analyzed.

3. The laser gyroscope backscattering evaluation device according to claim 1, characterized in that, The bottom of the special fixture (8) is hollowed out and connected to the rotating stage (6) by a thin rod with a slot, so as to ensure that the mirror sample to be tested and the special fixture (8) will not slip during rotation.

4. The laser gyroscope backscattering evaluation device according to claim 3, characterized in that, The interior of the rotating platform (6) is blackened; Controller A (5) controls the rotating stage (6) to drive the special fixture (8) and the sample of the reflector to be tested to rotate, thereby realizing the automatic detection of backscattered light in nearly 360 degrees.

5. The laser gyroscope backscattering evaluation device according to claim 1, characterized in that, The placement and angle of the off-axis parabolic mirror (3) with a hole must ensure that the laser output from the laser can pass completely through its central hole and will not be reflected on the inner sidewall of the hole, thus affecting the detection accuracy. The mirror sample to be tested needs to be placed at the focal length position of the off-axis parabolic mirror (3) with a hole to ensure that the backscattered light of the mirror sample to be tested is completely received.

6. The laser gyroscope backscattering evaluation device according to claim 1, characterized in that, The aperture B (4) must be placed close to the sample of the mirror to be tested in order to avoid stray light being received by the perforated off-axis parabolic mirror (3).

7. The laser gyroscope backscattering evaluation device according to claim 6, characterized in that, The aperture B (4) can control the size of the solid angle of the backscattered light incident on the perforated off-axis parabolic mirror (3). The size of the aperture B (4) can be adjusted according to specific needs to change the size of the solid angle of the backscattered light and achieve more accurate measurement.

8. A method for evaluating backscattering from a laser gyroscope mirror, characterized in that, The method is implemented using the apparatus described in any one of claims 1-7, and the method steps are as follows: Step 1: Place the mirror calibration component held by the special fixture on the rotary table, initialize the rotary table, and adjust the optical path so that the laser beam passes through the perforated off-axis parabolic mirror and is incident on the center of the mirror calibration component. Step 2: Adjust the position and angle of light trap A and light trap B so that the reflected and transmitted light are completely absorbed by the light traps; Step 3: Adjust the position of the low-light imaging system so that the backscattered light can be clearly imaged on the low-light industrial camera; Step 4: Adjust the aperture of aperture B to control the solid angle of backscattered light according to the test requirements, and filter out stray light; Step 5: After the reflector calibration components are calibrated, batch imaging detection and image storage are performed on the scattering of multiple reflector samples to be tested; the reflector samples to be tested are the same as the reflector calibration components. Step 6: Use an image grayscale processing algorithm to denoise the imaging results of multiple mirror samples to obtain the corresponding image grayscale values ​​of multiple mirror samples. Compare the backscattered light based on the image grayscale values. The smaller the backscattered light, the better the performance of the mirror sample.

9. The method for evaluating backscattering of a laser gyroscope mirror according to claim 8, characterized in that, In step five, the scattering from multiple test mirror samples is subjected to batch imaging detection and image storage, specifically as follows: Each mirror sample to be tested is placed on a special fixture. Controller A controls the rotary table to rotate the special fixture and the mirror sample to be tested, so as to realize the automatic detection of backscattered light of each mirror sample from nearly 360 degrees.

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