Laser gyroscope reflector backscattering evaluation device and method

Abstract

The invention belongs to the technical field of laser gyroscopes, and relates to a device and a method for evaluating backscattering of a laser gyroscope reflector. The device comprises a laser light source, a diaphragm, a perforated off-axis parabolic mirror, a diaphragm, a controller, a rotating table, a light trap, a special sample clamp and a light trap, a diaphragm is installed in the direction of a light beam emitted by the laser light source and used for controlling the diameter of the output light beam, an off-axis parabolic mirror with a hole is installed behind the laser light source, laser enters the surface of a reflector sample to be measured after passing through a central through hole of the off-axis parabolic mirror and the diaphragm, and the reflector sample to be measured is clamped by a special clamp and placed on a rotating table.

Description

Technical Field

[0001] The invention belongs to the technical field of laser gyroscopes and relates to a laser gyroscope reflector backscattering evaluation device and method. Background Art

[0002] The scattering of optical elements in high-precision optical systems is an important factor affecting their accuracy. The scattering of mirrors in gravitational wave detectors, EUV lithography machines, high-precision spectral measurement systems, and laser gyroscopes is particularly important. Among them, high-precision laser gyroscopes are the core sensors of modern inertial guidance and navigation systems and are widely used in various types of aircraft, ships, missiles, and tanks. The process of improving the accuracy of laser gyroscopes is a history of struggle with the locking effect of laser gyroscopes, and the backscattering of laser gyroscope mirrors is an important factor affecting the locking area of ​​laser gyroscopes. In order to further improve the accuracy of gyroscopes, the engineering mainly attempts to improve the preparation processes such as precision polishing and coating of mirrors in order to reduce the backscattering of mirrors. The premise of iteratively improving and reducing the backscattering of mirrors in the preparation process is to accurately and quickly evaluate the size of the backscattering. However, due to the extremely low backscattering level of the ultra-smooth mirror of the laser gyroscope, it is difficult to detect the light intensity, and it is difficult to avoid the problem of the incident light path being blocked by the detector in the backscattering measurement, resulting in the actual measurement angle of the scattering deviating from the expected back direction.

[0003] At present, the measurement and evaluation methods for laser gyro reflector scattering generally adopt total integral scattering measurement method, angle-resolved scattering measurement method and light modulation measurement method. However, the total integral scattering method is limited by principle and can only measure the total scattering of the reflector with the help of an integrating sphere. There is a big difference between the total scattering measurement and the backscattering of the reflector. At the same time, for the current ultra-smooth surface reflector, its total integral scattering is less than 5ppm, and the test accuracy is difficult to meet the differentiation requirements, and the differentiation of scattering of different reflectors is poor; the angle-resolved scattering measurement method realizes the measurement of scattering values ​​at different scattering angles, but for the backscattering, the detector blocks the incident light path and cannot be accurately measured; the light modulation measurement method has a complex principle, and has high requirements for light path adjustment. The test is complex and time-consuming, and the repeatability is insufficient, making it difficult to apply in engineering. Summary of the invention

[0004] The purpose of the present invention is to propose a reflector backscattering rapid evaluation method based on scattering imaging, which has accurate test angle, high detection efficiency and can meet the needs of batch backscattering evaluation.

[0005] The technical solution of the present invention:

[0006] In one aspect, the present invention provides a laser gyro reflector backscattering evaluation device, the device comprising:

[0007] Laser light source 1, aperture A2, off-axis parabolic reflector with hole 3, aperture B4, controller A5, rotating table 6, light trap A7, special fixture for sample 8, light trap B9;

[0008] An aperture A2 is installed in the direction of the light beam emitted by the laser light source 1 to control the diameter of the output light beam, and an off-axis parabolic reflector 3 with a hole is installed behind it. The laser passes through its central through hole and the aperture B4 and then is incident on the surface of the reflector sample to be tested. The reflector sample to be tested is clamped by a special fixture 8 and placed on a rotating table 6;

[0009] The transmitted light passing through the surface of the reflector sample to be tested is absorbed by the light trap A7, and the reflected light reflected by the surface of the reflector sample to be tested is absorbed by the light trap B9. The backscattered light of the reflector sample to be tested passes through the aperture B4 to filter out the stray light, and then is incident on the off-axis parabolic reflector 3 with a hole. The off-axis parabolic reflector 3 with a hole collects the direction of the backscattered light and deflects it to the low-illuminance imaging system, and processes the collected image, and determines the size of the backscattered light according to the grayscale value of the image.

[0010] Furthermore,

[0011] The low-light imaging system includes: an objective lens 10, an eyepiece 11, and a 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 imaging clarity. After receiving the backscattered light signal, the low-light imaging system performs denoising processing through the data processing computer 15, and finally reads and analyzes the image grayscale value.

[0013] Furthermore,

[0014] The bottom surface of the special fixture 8 is hollowed out, and is connected to the rotating platform 6 via a thin rod with a slot, so as to ensure that the reflector sample to be tested and the special fixture 8 will not slip off during the rotation process.

[0015] Furthermore,

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

[0017] The controller A5 controls the rotating table 6 to drive the special fixture 8 and the reflector sample to be measured to rotate, thereby realizing automatic detection of nearly 360-degree backscattered light.

[0018] Furthermore,

[0019] The placement position and angle of the off-axis parabolic reflector with hole 3 must ensure that the laser output laser can pass completely through its central hole without being reflected on the side wall inside the hole, thereby affecting the detection accuracy; the reflector sample to be tested needs to be placed at the focal length position of the off-axis parabolic reflector with hole 3 to ensure that the backscattered light of the reflector sample to be tested is completely received.

[0020] Furthermore,

[0021] The aperture B4 must be placed close to the reflector sample to be tested to prevent stray light from being received by the off-axis parabolic reflector 3 with a hole.

[0022] Furthermore,

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

[0024] In a second aspect, the present invention further provides a method for evaluating backscattering of a laser gyro reflector, the method is implemented using the device, and the method steps are as follows:

[0025] Step 1: Place the reflector calibration piece held by a special fixture on a rotating table, initialize the rotating table, and adjust the optical path so that the laser passes through the off-axis parabolic reflector with a hole and is incident on the center of the reflector calibration piece;

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

[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 diaphragm B, control the solid angle of backscattered light according to test requirements, and filter out stray light;

[0029] Step 5: After the calibration of the reflector calibration piece is completed, 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 piece;

[0030] Step 6: Use the image grayscale value processing algorithm to denoise the imaging results of multiple reflector samples to be tested, obtain the image grayscale values ​​corresponding to the multiple reflector samples to be tested, and compare the size of the backscattered light according to the image grayscale value. The smaller the backscattered light, the better the performance of the corresponding reflector sample to be tested.

[0031] Furthermore, in step 5, batch imaging detection and image storage are performed on the scattering of multiple reflector samples to be tested, specifically:

[0032] Each reflector sample to be tested is placed on a special fixture, and controller A controls the rotating table to drive the special fixture and the reflector sample to be tested to rotate, so as to realize automatic detection of nearly 360-degree backscattered light of each reflector sample to be tested.

[0033] Beneficial effects of the present invention: The reflector backscattering rapid evaluation method based on scattering imaging of the present invention realizes the direct, accurate and rapid evaluation of scattered light within a certain back-directed solid angle of the laser gyroscope reflector. After the backscattering measurement device is calibrated, the reflector samples can be processed in batches, and the operation is simple and fast. With the help of this device and method, the backscattering of different reflectors can be evaluated and compared, and the polishing and coating processes of ultra-smooth reflectors can be guided. At the same time, with the help of this device and method, reflectors with smaller backscattering can be screened in advance for the assembly of laser gyroscopes, which is of great significance for reducing the lock area of ​​the laser gyroscope. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of an implementation of a method and device for quickly evaluating backscattering of a reflector based on scattering imaging according to an embodiment of the present invention.

[0035] The invention comprises a laser light source (1), an aperture A (2), an off-axis parabolic reflector with a hole (3), an aperture B (4), a controller A (5), a rotating table (6), a light trap A (7), a special fixture for a sample (8), a light trap B (9), an objective lens (10), an eyepiece (11), a low-light industrial camera (12), a precision stepping motor (13), a controller B (14), and a data processing computer (15).

[0036] Figure 2 It is a schematic diagram of the structure of a special sample fixture (8). DETAILED DESCRIPTION

[0037] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0038] The technical solution of the present invention is a laser gyro reflector backscattering evaluation device. The device comprises a laser light source 1, a low-light imaging system (a low-light industrial camera 12, an eyepiece lens group 10 and 11), an off-axis parabolic reflector 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 table 6, a special sample fixture 8 (such as Figure 2As shown), precision stepper motor 13, data processing computer 15. Among them, the output light beam of the laser light source 1 passes through aperture A, the light hole of the off-axis parabolic reflector with holes, aperture B in sequence, and then is incident on the surface of the reflector to be measured 16 on the rotating table, and the reflector to be measured is clamped by a special fixture; the transmitted light on the reflector surface is absorbed by light trap A, and the reflected light on the reflector surface is absorbed by light trap B; the backscattered light of a certain solid angle passes through aperture B, is collected by the off-axis parabolic reflector and refracted into the low-illuminance imaging system.

[0039] The focal length of the off-axis parabolic reflector with hole is 101.6 mm;

[0040] The off-axis parabolic reflector with holes is used to collect scattered light within a certain solid angle and fold the direction of the light path. At the same time, the low-illumination imaging system can be separated from the incident light path, thereby realizing accurate detection of backscattering within a certain solid angle.

[0041] The aperture B shields and absorbs stray light by controlling the position and the size of the aperture, and can control the size of the backscattering solid angle to be measured according to test requirements.

[0042] The movement of the rotating stage is controlled by a controller, and the fixture and sample reflector thereon can be rotated 360 degrees. With the special fixture design, the backscattering measurement of the reflector at an azimuth angle of nearly 360 degrees can be achieved.

[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 backscattered sample surface.

[0044] The low-illuminance imaging system is connected to a data processing computer and uses a dedicated image grayscale value processing algorithm to perform denoising and comparison on the brightness of the detected image.

[0045] A method for quickly evaluating backscattering of a reflector based on scattering imaging, the steps of which are as follows:

[0046] Step 1: Place the reflector calibration piece held by the sample-specific fixture on the rotating stage, initialize the rotating stage, and adjust the optical path so that the laser passes through the off-axis parabolic reflector with a hole and is incident on the center of the reflector calibration piece;

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

[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 of the diaphragm, control the scattered light solid angle according to the test requirements, and filter out stray light;

[0050] Step 5: After the calibration of the reflector calibration piece is completed, batch imaging detection and image storage are performed on the scattering of the reflector sample to be tested; the reflector sample to be tested is the same as the reflector calibration piece;

[0051] Step 6: Use the image gray value processing algorithm to denoise and compare the imaging results.

[0052] Example 1: See Figure 1 , which is a schematic diagram of the principle of a preferred implementation scheme of the method of the present invention. The measuring device comprises a laser light source 1, an aperture A2, an off-axis parabolic reflector with a hole 3, an aperture B4, a controller A5, a rotating table 6, a light trap A7, a special fixture for a sample 8, a light trap B9, an objective lens 10, an eyepiece 11, a low-light industrial camera 12, a precision stepping motor 13, a controller B14, and a data processing computer 15.

[0053] An aperture A2 is installed in the direction of the beam emitted by the laser light source 1 to control the diameter of the output beam. An off-axis parabolic reflector 3 with a hole is installed behind it. The laser passes through its central through hole and the aperture B4 and then enters the surface of the high-reflection mirror sample. The high-reflection mirror sample is clamped by a special fixture 8 and placed on a rotating table 6. The special fixture 8 is as shown in FIG. Figure 2 As shown, the bottom surface is hollowed out and connected to the rotating table by a thin rod with a slot to ensure that the sample and the fixture 8 will not slip during the rotation. The transmitted light enters the light trap A7 to avoid the transmission of scattered light. The interior of the rotating table 6 is blackened, and the controller A5 controls the rotation of the reflector to achieve automatic detection of nearly 360-degree backscattered light.

[0054] The transmitted light is absorbed by the light trap A7, and the reflected light is absorbed by the light trap B9. The backscattered light of the reflector sample is filtered out by the aperture B4 and then incident on the off-axis parabolic reflector 3 with a hole. The off-axis parabolic mirror 3 collects the direction of the backscattered light and deflects 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 imaging clarity. After receiving the backscattered light signal, the imaging system performs denoising through a data processing computer 15, and finally reads and analyzes the image grayscale value. It should be noted that the placement position and angle of the off-axis parabolic reflector 3 must ensure that the laser output can pass completely through its central hole and will not be reflected on the side wall inside the hole, thereby affecting the detection accuracy; the high-reflectivity mirror sample needs to be placed at the focal length position of the off-axis parabolic mirror 3 to ensure that the sample backscattered light can be completely received; the placement position of the aperture B4 must avoid as much as possible the stray light being received by the off-axis parabolic reflector 3 with a hole, thereby 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 small hole of the aperture B4 can also be adjusted to change the size of the solid angle to achieve more accurate measurement.

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

[0057] The reflector backscattering rapid evaluation method based on scattering imaging of the present invention realizes the direct, accurate and rapid evaluation of scattered light within a certain back-directed solid angle of the laser gyroscope reflector. After the backscattering measurement device is calibrated, the reflector samples can be processed in batches, and the operation is simple and fast. With the help of this device and method, the backscattering of different reflectors can be evaluated and compared, and the polishing and coating processes of ultra-smooth reflectors can be guided. At the same time, with the help of this device and method, reflectors with smaller backscattering can be screened in advance for the assembly of laser gyroscopes, which is of great significance for reducing the lock area of ​​the laser gyroscope.

Claims

1. A laser gyro reflector backscattering evaluation device, characterized in that: The device comprises: Laser light source (1), aperture A (2), off-axis parabolic reflector with hole (3), aperture B (4), controller A (5), rotating stage (6), light trap A (7), special fixture for sample (8), light trap B (9); An aperture A (2) is installed in the direction of the light beam emitted by the laser light source (1) to control the diameter of the output light beam, and an off-axis parabolic reflector (3) with a hole is installed behind it. The laser passes through its central through hole and the aperture B (4) and then is incident on the surface of the reflector sample to be tested. The reflector sample to be tested is clamped by a special fixture (8) and placed on a rotating table (6); The transmitted light passing through the surface of the reflector sample to be tested is absorbed by the light trap A (7), and the reflected light reflected by the surface of the reflector sample to be tested is absorbed by the light trap B (9). The backscattered light of the reflector sample to be tested is filtered out by the aperture B (4) to remove stray light, and then incident on the off-axis parabolic reflector with a hole (3). The off-axis parabolic reflector with a hole (3) collects the direction of the backscattered light and deflects it to the low-illuminance imaging system, processes the collected image, and determines the size of the backscattered light according to the gray value of the image.

2. The laser gyro reflector backscattering evaluation device according to claim 1, characterized in that: The low-light imaging system comprises: an objective lens (10), an eyepiece (11), and a low-light industrial camera (12); The low-light imaging system is fixed on a precision stepping motor (13). The movement of the low-light imaging system is controlled by a controller B (14) to ensure imaging clarity. After receiving the backscattered light signal, the low-light imaging system performs denoising processing through a data processing computer (15), and finally reads and analyzes the image grayscale value.

3. The laser gyro reflector backscattering evaluation device according to claim 1, characterized in that: The bottom surface of the special fixture (8) is hollowed out, and is connected to the rotating platform (6) via a thin rod with a slot, thereby ensuring that the reflector sample to be tested and the special fixture (8) will not slip off during the rotation process.

4. The laser gyro reflector backscattering evaluation device according to claim 3, characterized in that: The interior of the rotating table (6) is subjected to blackening treatment; The controller A (5) controls the rotating platform (6) to drive the special fixture (8) and the reflector sample to be measured to rotate, thereby realizing automatic detection of nearly 360-degree backscattered light.

5. The laser gyro reflector backscattering evaluation device according to claim 1, characterized in that: The placement position and angle of the off-axis parabolic reflector with a hole (3) must ensure that the laser output laser can completely pass through its central hole without being reflected on the inner side wall of the hole, thereby affecting the detection accuracy; the reflector sample to be tested needs to be placed at the focal length position of the off-axis parabolic reflector with a hole (3) to ensure that the backscattered light of the reflector sample to be tested is completely received.

6. The laser gyro reflector backscattering evaluation device according to claim 1, characterized in that: The aperture B (4) must be placed close to the reflector sample to be tested to prevent stray light from being received by the off-axis parabolic reflector with hole (3).

7. A laser gyro reflector 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 off-axis parabolic reflector with a hole (3). The size of the small hole of the aperture B (4) can be adjusted according to specific needs to change the size of the solid angle of the backscattered light to achieve more accurate measurement.

8. A laser gyro reflector backscattering evaluation method, characterized in that: The method is implemented by using the device according to any one of claims 1 to 7, and the method steps are as follows: Step 1: Place the reflector calibration piece held by a special fixture on a rotating table, initialize the rotating table, and adjust the optical path so that the laser passes through the off-axis parabolic reflector with a hole and is incident on the center of the reflector calibration piece; Step 2: Adjust the position and angle of light trap A and light trap B so that the reflected light and the transmitted light are completely absorbed by the light trap; 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 diaphragm B, control the solid angle of backscattered light according to test requirements, and filter out stray light; Step 5: After the calibration of the reflector calibration piece is completed, 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 piece; Step 6: Use the image grayscale value processing algorithm to denoise the imaging results of multiple reflector samples to be tested, obtain the image grayscale values ​​corresponding to the multiple reflector samples to be tested, and compare the size of the backscattered light according to the image grayscale value. The smaller the backscattered light, the better the performance of the corresponding reflector sample to be tested.

9. A laser gyro reflector backscattering evaluation method according to claim 8, characterized in that: In step 5, batch imaging detection and image storage are performed on the scattering of multiple reflector samples to be tested, specifically: Each reflector sample to be tested is placed on a special fixture, and controller A controls the rotating table to drive the special fixture and the reflector sample to be tested to rotate, so as to realize automatic detection of nearly 360-degree backscattered light of each reflector sample to be tested.

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