Star sensor automatic focusing test system and test method

Abstract

The present invention relates to optical parameter measurement, and in particular to a star sensor automatic focusing test system and test method. In order to solve the problem that the prior art is easily affected by image noise disturbance and the measurement accuracy cannot be guaranteed, the star sensor automatic focusing test system of the present invention includes a first target simulation subsystem, a control subsystem and a multi-dimensional turntable. The first target simulation subsystem includes a displacement table and a collimator, a star point target and a light source sequentially arranged along the radial direction of the multi-dimensional turntable. The method of performing a focusing test using the above-mentioned star sensor automatic focusing test system includes determining the initial position of the image acquisition, collecting star point images corresponding to the defocus amount of different star point targets in each field of view, fitting the overfocus curve of the corresponding field of view, fitting the best focal plane, calculating the focusing ring trimming amount and adjusting the focusing ring thickness, wherein the diameter corresponding to 80% energy concentration is used as the diffuse spot diameter to improve the test efficiency and ensure the test accuracy of the defocus amount.

Description

Technical Field

[0001] The invention relates to optical parameter measurement, and in particular to a star sensor automatic focusing test system and a test method. Background Art

[0002] Star sensors are widely used in the fields of space positioning and remote sensing mapping. Due to their characteristics of short focal length, large field of view, high precision, and strong detection capability, high focus adjustment accuracy is required during their installation. The high-precision focusing system of star sensors can realize imaging simulation of infinite and finite targets, and is used to complete high-precision defocus test of the lens of the star sensor and its detector image plane, thereby determining the thickness of the focus ring of the star sensor and guiding the processing and selection of the focus ring.

[0003] The detector image plane of the star sensor is defocused or tilted relative to the focal plane of the lens, causing the pixels in the detector image plane to not be on the focal plane of the lens, resulting in the detector image plane imaging being in a defocused state, affecting the detection capability of the star sensor. The high-precision focusing of the star sensor has the following difficulties: First, due to the small relative aperture of the star sensor, the focusing accuracy requirement is high (≤±0.005mm), but the error in manual assembly of the trimming pad is difficult to avoid, and it may be necessary to repeatedly test the defocus amount after multiple trial assembly of the trimming pad to ensure that the detector image plane is not defocused or tilted relative to the focal plane of the lens, resulting in a longer assembly cycle of the star sensor; secondly, if the tester is not familiar with the focusing process or has little engineering experience, the focusing efficiency is low, so higher requirements are placed on the tester. Figure 1 As shown, it is a schematic diagram of the principle of the high-precision focusing system of the star sensor. The current focusing system is realized by means of a light source 6, a star point target 7 and a collimator 8. The star point target 7 is installed on a displacement stage, and the displacement stage moves the star point target 7 to different positions along the light emitting direction of the collimator 8 in sequence, simulating a finite target 01 or an infinite target 02, and controls the star sensor 5 to image the star point target 7 at each position to obtain a star point image, and then analyzes the collected star point image, calculates the energy peak mean value, total energy mean value, star point image Gaussian radius and variance of the star point on the star point target 7 at each position, and adopts the difference fitting method to fit the star point energy peak over-focus curve and the star point radius over-focus curve to obtain the ideal focal plane 03 of the star sensor. In the process of testing by the above system, it is necessary to manually control the movement of the displacement stage and manually control the star sensor 5 to collect images, so the test efficiency is low. When the star sensor 5 is in a defocused state, the star image on the star image is a diffuse spot. When the defocus amount is large, the edge of the diffuse spot is difficult to distinguish from the background. The noise points in the star image will affect the star energy peak value and the total energy mean. Therefore, the energy concentration of the star point measured by this method during the test process is easily affected by the image noise disturbance. The unstable factors cause the data analysis result to be inaccurate and the measurement accuracy cannot be guaranteed. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the prior art is easily affected by image noise disturbance, resulting in the measurement accuracy not being guaranteed, and to provide a star sensor automatic focusing test system and test method.

[0005] To achieve the above objectives, the technical solutions provided by the present invention are as follows:

[0006] A star sensor automatic focusing test system is special in that it comprises a first target simulation subsystem, a control subsystem and a multidimensional turntable, wherein the star sensor is arranged at the center of the multidimensional turntable, and the multidimensional turntable is used to control the rotation of the star sensor in the azimuth direction and the pitch direction; the first target simulation subsystem comprises a translation platform, and collimators, star point targets and light sources arranged in sequence along the radial direction of the multidimensional turntable, wherein the collimators are located on a side close to an entrance pupil of the star sensor; the star point target is arranged on the translation platform, and the star point target is moved forward and backward along the optical axis direction of the collimators by controlling the movement of the translation platform; the control subsystem is connected to the star sensor, the multidimensional turntable and the translation platform, and is used to control the working state of the star sensor, receive and process the star point images of the star sensor, and control the rotation of the multidimensional turntable and the movement of the translation platform.

[0007] Furthermore, it also includes a second target simulation subsystem, the structure of the second target simulation subsystem is the same as that of the first target simulation subsystem, the optical axis of the collimator of the second target simulation subsystem intersects with the optical axis of the collimator of the first target simulation subsystem at the center of the multi-dimensional turntable, and the focal length is less than 1000mm;

[0008] The second target simulation subsystem is used to provide different collimator focal lengths;

[0009] The focal length of the collimator of the first target simulation subsystem is greater than or equal to 1000 mm.

[0010] At the same time, the present invention also provides a star sensor automatic focusing test method, which is special in that it includes the following steps:

[0011] S1. Calculate the moving step and size of the star point target; select the focal length of the collimator according to the moving step;

[0012] S2. According to the star point size and collimator focal length in step S1, the star sensor automatic focusing test system is constructed, and the star sensor is set on a multidimensional turntable;

[0013] S3. Adjust the multi-dimensional turntable so that the centroid of the diffuse spot on the star point image corresponding to the focal plane of the collimator coincides with the image center;

[0014] S4. respectively collect star point images corresponding to the defocus values ​​of multiple star point targets in the field of view of the star sensor in the 0 field of view, the positive and negative directions of the azimuth X, and the positive and negative directions of the pitch Y, and use the star point target position corresponding to the minimum diffuse spot diameter of the star point image in the same field of view as the initial position of the image collection in the corresponding field of view;

[0015] The diffuse spot diameter is the diameter corresponding to the energy concentration of η; wherein the value range of η is 75%-85%;

[0016] S5. Based on the initial position of each field of view in step S4, the star point images corresponding to different star point target defocus amounts in each field of view are collected;

[0017] S6. fitting the overfocus curve of the corresponding field of view according to the star point images corresponding to the different star point target defocus amounts in each field of view, obtaining the star point target defocus amount corresponding to the minimum diffuse spot diameter, and thereby calculating the focal plane defocus amount of the star sensor in each field of view;

[0018] S7. According to the focal plane defocus amount of the star sensor in each field of view obtained in step S6, the detector imaging position coordinates of the star sensor in each field of view are calculated, and the optimal focal plane is fitted;

[0019] S8. Calculate the distances from each connecting flange between the lens and the detector of the star sensor to the optimal focal plane, that is, obtain the trimming amount of the focus ring set at the corresponding connecting flange, adjust the thickness of the focus ring according to the trimming amount of the focus ring, and complete the automatic focusing test of the star sensor.

[0020] Further, step S3 is specifically as follows: the control subsystem controls the translation stage to move the star point target to the focal plane of the collimator, collects the corresponding star point image, processes the star point image to obtain the centroid coordinates of the diffuse spot on the star point image, and calculates the number of pixels in the horizontal and vertical directions that the centroid coordinates deviate from the center of the image. , calculate the azimuth adjustment angle of the multi-dimensional turntable according to the following formula and pitch adjustment angle ,according to and Adjust the multi-dimensional turntable so that the centroid of the diffuse spot coincides with the center of the image;

[0021]

[0022]

[0023] Where: is the pixel size of the star sensor, is the focal length of the star sensor.

[0024] Furthermore, step S5 is specifically as follows: the control subsystem controls the translation stage to move the star point target to the focal plane of the collimator, collects the corresponding star point image, and then controls the star point target to move forward and backward multiple steps along the optical axis of the collimator at the focal plane of the collimator based on the moving step calculated in step S1, collects the corresponding star point image, and obtains the star point images corresponding to different star point target defocus amounts.

[0025] Further, in step S5, the star point target is controlled to move forward and backward 8 steps each according to the moving step calculated in step S1;

[0026] In step S4, the diffuse spot diameter is the diameter corresponding to the energy concentration η=80%.

[0027] The diffuse spot diameter can also be taken as the diameter corresponding to the energy concentration η=75% and 85%.

[0028] Further, step S6 is specifically as follows: the control subsystem calculates the diffuse spot diameter of the star point image corresponding to the star point target defocus amount of each field of view, fits the overfocus curve of the star point target defocus amount and the diffuse spot diameter, thereby obtaining the star point target defocus amount corresponding to the minimum diffuse spot diameter of the star sensor in each field of view, and then calculates the focal plane defocus amount of the star sensor in each field of view using the following formula;

[0029]

[0030] Where: is the star point target defocus amount corresponding to the minimum diffuse spot diameter in the field of view n, is the focal plane defocus of the star sensor in the field of view n; is the focal length of the collimator, and the field of view n is one of the fields of view of 0, +0.8 in the azimuth X direction, -0.8 in the azimuth X direction, +0.8 in the elevation Y direction, and -0.8 in the elevation Y direction.

[0031] Further, step S7 is specifically as follows: a coordinate system is established with the center of the lens focal plane of the star sensor as the origin, the azimuth X direction of the star sensor as the x-axis, the pitch Y direction as the y-axis, and the lens optical axis as the z-axis, and the detector imaging position coordinates of the star sensor in each field of view are calculated according to the following formula, and the optimal focal plane is fitted;

[0032]

[0033]

[0034] in, is the field of view angle of the star sensor corresponding to the field of view n, is the coordinate value of the imaging position of the star sensor detector in the azimuth X direction in the field of view n, is the coordinate value of the imaging position of the star sensor detector in the pitch Y direction in the field of view n, M=0.8, indicating a field of view of 0.8.

[0035] Furthermore, in step S8, the thickness of the focus ring is adjusted according to the trimming amount of the focus ring, specifically: if the trimming amount of the focus ring is a negative value, replace the thick focus ring, and the increased thickness of the focus ring is the absolute value of the trimming amount; if the trimming amount of the focus ring is a positive value, replace the thin focus ring, and the reduced thickness of the focus ring is the value of the trimming amount.

[0036] Furthermore, step S1 is specifically as follows:

[0037] S1.1. Calculate the star point moving step S according to the following formula and round the result;

[0038]

[0039] In the formula, is the focal depth of the star sensor, is the F number of the star sensor, is the central wavelength of the star sensor;

[0040] S1.2. Determine and select the appropriate target simulation subsystem by the following methods;

[0041] Calculate S×N, where N is the total number of steps moving back and forth at the initial position of the image acquisition when acquiring the image, and define L as the total travel of the translation stage in the first target simulation subsystem;

[0042] If S×N>L, select the second target simulation subsystem, otherwise select the first target simulation subsystem;

[0043] S1.3. Calculate the star point size according to the following formula :

[0044]

[0045] In the formula, is the entrance pupil diameter of the star sensor.

[0046] Beneficial effects of the present invention:

[0047] 1. A control subsystem is provided in the star sensor automatic focusing test system of the present invention, and the control subsystem controls the working state of the star sensor, receives the star point image of the star sensor and processes the image, controls the rotation of the multi-dimensional turntable and the movement of the translation stage, so as to realize the automatic operation of the automatic focusing test system.

[0048] 2. The star sensor automatic focusing test system of the present invention comprises a first target simulation subsystem and a second target simulation subsystem with different focal lengths of collimators, so that the test system has a wider application range and is convenient and flexible to use.

[0049] 3. The star sensor automatic focusing test method of the present invention automatically collects star point images of star point targets at different defocus values, uses the diameter corresponding to 80% energy concentration of the diffuse spot as the diffuse spot diameter, calculates the focal plane defocus value of the star sensor, and ensures the test accuracy of the defocus value while improving the test efficiency. At the same time, by confirming the initial position of the image acquisition, it is possible to accurately fit the overfocus curve by acquiring only one round of images for each field of view, further improving the test efficiency, shortening the acquisition time, and ensuring the accuracy of the defocus value interpretation.

[0050] 4. In the automatic focusing test method for a star sensor of the present invention, the full field of view of the star sensor is tested, and finally each focusing ring between the lens and the detector of the star sensor is trimmed to improve the test accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the principle of the high-precision focusing system of the star sensor in the prior art;

[0052] Figure 2 Schematic diagram of a star sensor lens in an embodiment of a star sensor automatic focusing test system of the present invention;

[0053] Figure 3 It is a schematic diagram of the adjustment error of the star sensor lens and the detector and the imaging principle in the embodiment of the star sensor automatic focusing test system of the present invention;

[0054] Figure 4 A schematic structural diagram of an embodiment of a star sensor automatic focusing test system of the present invention;

[0055] Description of reference numerals:

[0056] 01- finite distance target, 02- infinite distance target, 03- ideal focal plane of star sensor;

[0057] 1- first target simulation subsystem, 2- second target simulation subsystem, 3- multi-dimensional turntable, 4- control subsystem, 5- star sensor, 51- lens, 6- light source, 7- star point target, 8- collimator, 9- translation stage. DETAILED DESCRIPTION

[0058] In view of the problems existing in the high-precision focusing of star sensors in the prior art, in order to improve the assembly efficiency of the star sensor 5, the present invention designs an automatic focusing test system and test method that can automatically collect and process image data and quickly obtain high-precision star sensor defocus value.

[0059] The automatic focusing test method of the star sensor of the present invention adopts highly automated processing methods such as automatic centering, automatic selection of initial position for image acquisition, automatic acquisition of multi-field images, automatic fitting of overfocus curves, and automatic fitting of optimal focal planes, thereby greatly shortening the installation period while ensuring the installation quality of the star sensor 5. When the detector image plane B of the star sensor 5 is at the focal plane position of the optical system, the star point image is required to meet the requirement of "the star point image is 3×3 pixel dispersion, and the energy concentration is ≥80%", so it can be used as a criterion for judging whether the detector image plane B of the star sensor 5 is defocused relative to the focal plane of the optical system. After the focusing ring trimming amount is obtained by the method introduced in the present invention, the focusing ring of the star sensor 5 is adjusted, and then the test result can be verified by the criterion. At the same time, the present invention uses the diameter corresponding to 80% energy concentration of the diffuse spot as the diffuse spot diameter, thereby improving the test efficiency.

[0060] The automatic focusing test method of the star sensor of the present invention is based on Figure 1 The star sensor focusing system shown is improved, and parallel light is emitted by a high-precision collimator 8, and a star point target 7 is set at the focal plane of the collimator 8 to simulate an infinite target 02, and a star point target 7 is set before and after the focal plane of the collimator 8 to simulate a finite target 01. At the same time, the star sensor 5 images it and outputs a star point image. During the test, the star point target 7 is moved before and after the focal plane of the test system by controlling the displacement stage 9. If the detector image plane B of the star sensor 5 is defocused or tilted from its lens focal plane A, diffuse spots of different diameters will be formed on the star point image with different defocus amounts. After the star point image is processed and normalized, the diffuse spots on the star point image with different defocus amounts are extracted to obtain a diffuse spot diameter matrix. By interpreting the size of the diffuse spot diameter, the defocus amount of the collimator 8 is automatically calculated, and finally the defocus amount of the star sensor 5 and the detector image plane B is deduced.

[0061] When the detector image plane B of the star sensor 5 is out of focus or relatively tilted from the lens focal plane A, the imaging principle is as follows: Figure 2 and Figure 3As shown, the defocus distance between the detector image plane B and the lens focal plane A is L, and the included angle is α. The lens 51 of the star sensor 5 is connected to the detector through four connecting flanges, and a focusing ring is placed at each connecting flange. Due to the inclination of the detector image plane B, the focus ring at different field of view positions needs different thicknesses to achieve the overlap of the detector image plane B and the lens focal plane A. Therefore, according to the focusing test principle, the system collects images of the diffuse spots in the full field of view of the star sensor, fits the overfocus curve, calculates the positional relationship between the detector image plane B and the lens focal plane A, and then finally calculates the focusing ring trimming amounts at the four connecting flanges of the lens 51 of the star sensor 5 and the detector from the positional relationship. To improve the test efficiency, the present embodiment preferably performs the test at 0 field of view and 0.8 field of view, corresponding to 0 field of view and +0.8 field of view in the azimuth X direction, -0.8 field of view in the azimuth X direction, +0.8 field of view in the elevation Y direction, and -0.8 field of view in the elevation Y direction of the star sensor 5, and are recorded as 0, X+0.8, X-0.8, Y+0.8, and Y-0.8, respectively.

[0062] The star sensor automatic focusing test system of the present invention comprises a target simulation subsystem, a control subsystem 4 and a multi-dimensional turntable 3, and the layout is as follows: Figure 4 As shown, the star sensor 5 is arranged at the center of the multi-dimensional turntable 3, and the multi-dimensional turntable 3 can realize the rotation of the star sensor 5 in the azimuth direction and the pitch direction. In order to improve the focusing test efficiency of the star sensor 5 and effectively control the test cost, the focusing test system is based on the principle of "high-low matching", and two sets of target simulation subsystems are set to perform automatic focusing tests on star sensors 5 with different focal lengths respectively, which are respectively recorded as the first target simulation subsystem 1 and the second target simulation subsystem 2. The first target simulation subsystem 1 includes a displacement stage 9 and a collimator 8, a test target and a light source 6 arranged in sequence along the radial direction of the multi-dimensional turntable 3. The collimator 8 is located on the side close to the entrance pupil of the star sensor 5; the light source 6 is generated by a uniform light source simulation device, and the test target is a star point target 7. The star point target 7 is arranged on the displacement stage 9, and the movement of the star point target 7 is realized by controlling the displacement stage 9. In this embodiment, the displacement stage 9 is a one-dimensional displacement stage 9, and the collimator 8 uses a large-field apochromatic collimator 8. The structure of the second target simulation subsystem 2 is the same as that of the first target simulation subsystem 1. The optical axis of its collimator 8 intersects with the optical axis of the collimator 8 of the first target simulation subsystem 1 at the center of the multi-dimensional turntable 3. The star sensor 5 can be coaxial with the first target simulation subsystem 1 and the second target simulation subsystem 2 respectively by rotating the multi-dimensional turntable 3. In this embodiment, the two optical axes are arranged vertically. The focal length of the collimator 8 of the first target simulation subsystem 1 is greater than or equal to 1000mm, and the focal length of the collimator 8 of the second target simulation subsystem 2 is less than 1000mm. In this embodiment, the focal lengths of the two are designed to be 1000mm and 200mm respectively.

[0063] The control subsystem 4 is connected to the star sensor 5, the multidimensional turntable 3 and the translation stage 9, and is used to control the working state of the star sensor 5, receive the star point image of the star sensor 5 and process the image, control the rotation of the multidimensional turntable 3 and the movement of the translation stage 9, and control the translation stage 9 to move the star point target 7 forward and backward along the optical axis direction of the parallel light tube 8.

[0064] The test method using the above-mentioned star sensor automatic focusing test system specifically includes the following steps:

[0065] 1) Determine the required focal length of the collimator 8: Calculate the star point moving step S according to the following formula, and the calculation result is usually rounded;

[0066] (1)

[0067] In the formula, is the focal depth of the star sensor 5, is the focal length of the star sensor 5, is the focal length of the collimator 8, is the F number of star sensor 5, is the central wavelength of the star sensor 5;

[0068] The appropriate target simulation subsystem is selected by:

[0069] If S×N>L, select the second target simulation subsystem 2, otherwise select the first target simulation subsystem 1.

[0070] Among them, N is the total number of steps moving back and forth at the initial position of the image acquisition when acquiring the image, and the value in this embodiment is 16. L is the total stroke of the translation stage 9 in the first target simulation subsystem 1, and the value in this embodiment is 600 mm.

[0071] 2) Select the star point size of the star point target 7 : Star point size of star point target 7 Calculate according to formula (2):

[0072] (2)

[0073] In the formula, is the entrance pupil diameter of the star sensor 5.

[0074] 3) Install the product under test: Install the above-mentioned star sensor automatic focusing test system, set the first target simulation subsystem 1 and the second target simulation subsystem 2 so that their optical axes are perpendicular to each other, and the multi-dimensional turntable 3 is located at the intersection of their optical axes; the product under test is the star sensor 5 under test, which is installed at the center of the table of the multi-dimensional turntable 3. In this embodiment, the first target simulation subsystem 1 is selected for testing, and the multi-dimensional turntable 3 is adjusted so that the entrance pupil of the star sensor 5 is directly opposite to the exit pupil of the collimator 8 of the first target simulation subsystem 1.

[0075] 4) Automatic centering: The control subsystem 4 controls the displacement stage 9 to move the star point target 7 to the focal plane of the collimator 8, collects the corresponding star point image, automatically interprets the centroid coordinates of the diffuse spot on the star point image, and calculates the number of pixels in the horizontal and vertical directions that the centroid deviates from the center of the image. , the azimuth adjustment angle of the multi-dimensional turntable 3 is calculated according to the following formula and pitch adjustment angle , adjust the angle according to the direction and pitch adjustment angle The multi-dimensional turntable 3 is adjusted so that the centroid of the diffuse spot coincides with the center of the image.

[0076] (3)

[0077] (4)

[0078] In the formula, is the pixel size of star sensor 5.

[0079] The method for automatically interpreting the centroid coordinates of the diffuse spot is as follows:

[0080] Since the centroid pixel value of the diffuse spot in the collected star point image is the maximum value in the entire star point image, the maximum value of the image matrix pixel of the star point image can be solved by the control subsystem 4 using the "max(max()) function" in "MATLAB Functions and Applications" (Tsinghua University Press, 2022), and then the pixel coordinates corresponding to the maximum value are found by the "find function", which is the centroid coordinate of the diffuse spot. This process is automatically completed by the control subsystem 4.

[0081] 5) Automatically select the initial position for image acquisition: control the star point target 7 to move to the focal plane of the collimator 8 through the control subsystem 4, collect the corresponding star point image, and then control the star point target 7 to move forward and backward 8 steps according to the moving step calculated in step 1) with the focal plane of the collimator 8 as the reference, collect the corresponding star point image, and obtain a group of 17 star point images corresponding to different star point target defocus amounts. The control subsystem 4 judges the size of the diffuse spot diameter in each star point image and compares it to ensure that the change trend of the diffuse spot diameter includes the process from large to small and then to large, that is, it includes the clear position after defocusing, and then determine the minimum value of the diffuse spot diameter in the group of images, and feed back the position information corresponding to the minimum value to the displacement stage 9 as the initial position for image acquisition, and then the displacement stage 9 automatically moves to this position. If the obtained diffuse spot diameter does not contain the above-mentioned change trend, then according to the diffuse spot diameter size in the collected star point image, the moving steps are increased before and after the focal plane of the collimator 8, the star point target 7 is moved, and multiple star point images corresponding to different positions of the star point target 7 are additionally collected to meet the above-mentioned change trend.

[0082] The initial position of image acquisition is usually selected as the focal plane position after calibration of the collimator 8. However, if the defocus of the star sensor is large, the star point image obtained during the entire acquisition process may not contain a clear star point target 7. In this case, the initial position must be reset manually or the number of acquired images must be increased. In order to avoid this problem, the present invention designs an automatic selection method for the initial position of image acquisition, so that the overfocus curve can be accurately fitted by acquiring only one round of images for each field of view, which not only shortens the acquisition time but also ensures the accuracy of the defocus judgment.

[0083] In the present invention, the diameter of the diffuse spot is determined according to the following method: Since the diameter of the diffuse spot reflects the energy concentration of the diffuse spot, the present invention uses the control subsystem 4 to calculate the diameter corresponding to 80% energy concentration of the diffuse spot using high-order polynomial fitting and least squares optimization algorithm, and uses this as the diameter of the diffuse spot. The high-order polynomial fitting can be implemented using the "polyfit function" and "lsqcurvefit function" in the book "MATLAB Functions and Applications".

[0084] 6) Automatically collect multi-field images: In order to fit the defocus and tilt of the detector image plane B of the star sensor 5 relative to its lens focal plane A, the star sensor 5 needs to image the star point target 7 simulating the finite distance target 01 in different fields of view, and also image the star point target 7 simulating the infinite distance target 02 in different fields of view. Figure 2 The imaging position of the star point in 0 field of view and ±0.8 field of view in the azimuth X direction and ±0.8 field of view in the elevation Y direction is shown in the figure; the azimuth and elevation angles of the star sensor 5 are adjusted by the multidimensional turntable 3 to convert the field of view, and the initial position of the map is selected according to step 5) at 0 field of view and ±0.8 field of view in the azimuth X direction and ±0.8 field of view in the elevation Y direction of the star sensor 5, and the star point target 7 is moved multiple times according to the moving step of the star point target 7 to obtain star point images corresponding to different star point target defocus amounts.

[0085] 7) Automatically fit the overfocus curve and judge the focal plane defocus amount: After processing and normalizing the star point image obtained in step 6), extract the diffuse spot diameter on the star point image under different star point target defocus amounts to obtain the diffuse spot diameter matrix. After the control subsystem 4 calculates the diffuse spot diameter matrix of each field of view, fit the relationship curve between the defocus amount of different star point targets and the diffuse spot diameter in each field of view, that is, the overfocus curve. The star point target defocus amount corresponding to the minimum diffuse spot diameter is obtained from the fitted overfocus curve, and then the focal plane defocus amount of the star sensor in each field of view is calculated using formula (5) according to the star point target defocus amount:

[0086] (5)

[0087] In the formula, is the star point target defocus amount corresponding to the minimum diffuse spot diameter in the field of view n; is the focal plane defocus of the star sensor in the field of view n; n takes the values ​​of 0, X+0.8, X-0.8, Y+0.8, and Y-0.8.

[0088] Among them, the overfocus curve is fitted by the control subsystem 4 using the least square curve fitting algorithm. The "polyfit function and polyval function" in the book "MATLAB Functions and Applications" can realize this function.

[0089] After step 7), the star point target defocus amount and the star sensor focal plane defocus amount corresponding to the minimum diffuse spot diameter of 0 field of view, +0.8 field of view in azimuth X direction, -0.8 field of view in azimuth X direction, +0.8 field of view in elevation Y direction, and -0.8 field of view in elevation Y direction are calculated in sequence.

[0090] 8) Automatically fit the best focal plane: Define, the defocus value of the zero field star point target calculated in step 7) is The defocus values ​​of the star point targets in the azimuth X direction +0.8 field of view, the azimuth X direction -0.8 field of view, the elevation Y direction +0.8 field of view, and the elevation Y direction -0.8 field of view are respectively , , the focal plane defocus of the star sensor with a field of view of 0 is L0, and the corresponding focal plane defocus of the star sensor is L X+0.8 , L X-0.8 , L Y+0.8 , L Y-0.8 ; The center coordinate of the focal plane A of the mark star sensor 5 is (0,0,0), with the center of the focal plane A of the lens as the origin, the azimuth X direction as the x-axis, the pitch Y direction as the y-axis, and the optical axis of the lens 51 as the z-axis, the z-axis coordinate value of the focal plane defocus of the star sensor of the different fields of view calculated in step 7) as the detector imaging position point coordinate of the star sensor 5, and then according to the following formula, the detector imaging position point x-axis and y-axis coordinate values ​​of the star sensor 5 in 0 field of view, azimuth X direction +0.8 field of view, azimuth X direction -0.8 field of view, pitch Y direction +0.8 field of view, pitch Y direction -0.8 field of view are calculated, and its coordinates are respectively recorded as (0,0,L), (X X+0.8 ,0,L X+0.8 ), (-X X+0.8 ,0,L X+0.8 ), (0, Y Y+0.8 , L Y+0.8 ), (0, -Y Y+0.8 , L Y+0.8 );

[0091]

[0092]

[0093] In the formula, is the field of view angle of star sensor 5 corresponding to field of view n, is the coordinate value of the detector imaging position of star sensor 5 in the field of view n in the azimuth X direction, is the coordinate value of the detector imaging position point of the star sensor 5 in the field of view n in the pitch Y direction, M=0.8, indicating a 0.8 field of view. In other embodiments of the present invention, different fields of view may be selected and corresponding values ​​may be taken.

[0094] The singular value decomposition (SVD) plane fitting algorithm is used to fit the best focal plane that passes through the coordinates of the above five imaging positions at the same time;

[0095] 9) Automatically calculate the amount of trimming of the focus ring: The four connecting flanges of the lens 51 of the star sensor 5 and the detector are respectively denoted as X1, X2, Y1, and Y2. Figure 2 As shown, the distances from the four connecting flanges to the optimal focal plane are calculated, that is, the trimming amount of the focus ring set at the corresponding connecting flange is obtained. If the trimming amount of the focus ring is a negative value, it means that the thickness of the focus ring is too small. A thick focus ring should be replaced, and the increased thickness of the focus ring is the absolute value of the trimming amount. If the trimming amount of the focus ring is a positive value, it means that the thickness of the focus ring is too large. A thin focus ring should be replaced, and the reduced thickness of the focus ring is the value of the trimming amount.

[0096] At this point, the entire test process of the star sensor automatic focusing test system is completed.

[0097] During the test, the movement of the displacement stage 9 and the multi-dimensional turntable 3 and the image acquisition of the star sensor 5 are all controlled by the control subsystem 4. In this embodiment, the computer is used as a comprehensive controller and is equipped with the control subsystem 4. The displacement stage 9 and the multi-dimensional turntable 3 communicate with the computer through a serial port. The serial port instructions are specified and provided by the suppliers of the displacement stage 9 and the multi-dimensional turntable 3. After connecting the serial port, the displacement stage 9 and the multi-dimensional turntable 3 can be controlled to move by sending corresponding serial port instructions through the computer. The multi-dimensional turntable 3 adopts a two-dimensional turntable. The star sensor 5 communicates with the computer through the acquisition card equipped therewith. After connecting the acquisition card, the image acquisition instruction can be sent through the computer to control the star sensor 5 to acquire images.

Claims

1. A star sensor automatic focusing test method, characterized in that: The following steps are involved: S1. Calculate the moving step and star size of the star target (7); select the focal length of the collimator according to the moving step; S2. According to the star point size and collimator focal length in step S1, a star sensor automatic focusing test system is constructed, and the star sensor (5) is set on a multidimensional turntable (3); The star sensor automatic focusing test system comprises a first target simulation subsystem (1), a control subsystem (4) and a multidimensional turntable (3); a star sensor (5) is arranged at the center of the multidimensional turntable (3); and the multidimensional turntable (3) is used to control the rotation of the star sensor (5) in an azimuth direction and a pitch direction; The first target simulation subsystem (1) comprises a translation stage (9) and a collimator (8), a star point target (7) and a light source (6) arranged in sequence along the radial direction of the multi-dimensional rotating stage (3), wherein the collimator (8) is located on a side close to an entrance pupil of the star sensor (5); The star point target (7) is arranged on a displacement platform (9), and the star point target (7) is moved forward and backward along the optical axis direction of the parallel light tube (8) by controlling the displacement platform (9). The control subsystem (4) is connected to the star sensor (5), the multidimensional turntable (3) and the displacement stage (9), and is used to control the working state of the star sensor (5), receive the star point image of the star sensor (5) and process the image, and control the rotation of the multidimensional turntable (3) and the movement of the displacement stage (9); S3. Adjust the multi-dimensional turntable (3) so that the centroid of the diffuse spot on the star point image corresponding to the focal plane of the collimator coincides with the image center; S4. respectively collect star point images corresponding to the defocus values ​​of multiple star point targets in the field of view of the star sensor (5) in the 0 field of view, the positive and negative directions of the azimuth X direction, and the positive and negative directions of the pitch Y direction, and use the position of the star point target (7) corresponding to the minimum value of the diffuse spot diameter of the star point image in the same field of view as the initial position of the image collection in the corresponding field of view; The diffuse spot diameter is the diameter corresponding to the energy concentration being η; The value range of η is 75%-85%; S5. Taking the initial position of each field of view in step S4 as a reference, collecting star point images corresponding to different star point target defocus amounts in each field of view; S6. fitting the overfocus curve of the corresponding field of view according to the star point images corresponding to the different star point target defocus amounts in each field of view, obtaining the star point target defocus amount corresponding to the minimum diffuse spot diameter, and thereby calculating the focal plane defocus amount of the star sensor in each field of view; S7. According to the focal plane defocus amount of the star sensor in each field of view obtained in step S6, the detector imaging position coordinates of the star sensor (5) in each field of view are calculated, and the optimal focal plane is fitted; S8. Calculate the distances from each connection flange between the lens (51) of the star sensor (5) and the detector to the optimal focal plane, that is, obtain the trimming amount of the focus ring set at the corresponding connection flange, adjust the thickness of the focus ring according to the trimming amount of the focus ring, and complete the automatic focusing test of the star sensor (5).

2. The star sensor automatic focusing test method according to claim 1, characterized in that: The star sensor automatic focusing test system further comprises a second target simulation subsystem (2), the structure of the second target simulation subsystem (2) being the same as that of the first target simulation subsystem (1), the optical axis of the collimator (8) of the second target simulation subsystem (2) intersecting with the optical axis of the collimator (8) of the first target simulation subsystem (1) at the center of the multi-dimensional turntable (3), and the focal length being less than 1000 mm; The second target simulation subsystem (2) is used to provide different collimator focal lengths; The focal length of the collimator of the first target simulation subsystem (1) is greater than or equal to 1000 mm.

3. The star sensor automatic focusing test method according to claim 2, characterized in that: Step S3 is specifically as follows: The control subsystem (4) controls the displacement stage (9) to move the star point target (7) to the focal plane of the collimator, collects the corresponding star point image, processes the star point image to obtain the centroid coordinates of the diffuse spot on the star point image, calculates the number of pixels N1 and N2 of the centroid coordinates deviating from the image center in the horizontal and vertical directions, and calculates the azimuth adjustment angle θ of the multi-dimensional turntable (3) according to the following formula: 方位 and pitch adjustment angle θ 俯仰 , according to θ 方位 and θ 俯仰 Adjust the multi-dimensional turntable (3) so that the centroid of the diffuse spot coincides with the center of the image; θ 方位 =arctan(ss*N1 / f 星敏感器 ) θ 俯仰 =arctan(ss*N2 / f 星敏感器 ) Where: ss is the pixel size of the star sensor (5), f 星敏感器 is the focal length of the star sensor (5).

4. The star sensor automatic focusing test method according to claim 3, characterized in that: Step S5 is specifically as follows: The control subsystem (4) controls the displacement stage (9) to move the star point target (7) to the focal plane of the collimator, collects the corresponding star point image, and then controls the star point target (7) to move forward and backward a plurality of steps along the optical axis of the collimator (8) at the focal plane of the collimator according to the moving step calculated in step S1, collects the corresponding star point image, and obtains the star point images corresponding to different star point target defocus amounts.

5. The star sensor automatic focusing test method according to claim 4, characterized in that: In step S5, the star point target (7) is controlled to move forward and backward 8 steps each according to the moving step calculated in step S1; In step S4, the diffuse spot diameter is the diameter corresponding to the energy concentration η=80%.

6. The star sensor automatic focusing test method according to claim 5, characterized in that: Step S6 is specifically as follows: The control subsystem (4) calculates the diffuse spot diameter of the star point image corresponding to the defocus amount of the star point target in each field of view, and fits the overfocus curve of the star point target defocus amount and the diffuse spot diameter, thereby obtaining the star point target defocus amount corresponding to the minimum diffuse spot diameter of the star sensor (5) in each field of view, and then calculates the focal plane defocus amount of the star sensor in each field of view using the following formula; Where: L ′ n is the star point target defocus amount corresponding to the minimum diffuse spot diameter in the field of view n, L n is the focal plane defocus of the star sensor in the field of view n; f 平行光管 is the focal length of the collimator (8), and the field of view n is one of the fields of view of 0, +0.8 in the azimuth X direction, -0.8 in the azimuth X direction, +0.8 in the elevation Y direction, and -0.8 in the elevation Y direction.

7. The star sensor automatic focusing test method according to claim 6, characterized in that: Step S7 is specifically as follows: A coordinate system is established with the focal plane center of the lens (51) of the star sensor (5) as the origin, the azimuth X direction of the star sensor (5) as the x-axis, the elevation Y direction as the y-axis, and the optical axis of the lens (51) as the z-axis, and the coordinates of the detector imaging position point of the star sensor (5) in each field of view are calculated according to the following formula, and an optimal focal plane is fitted; X n =f 星敏感器 *tan(M*θ / 2) Y n =f 星敏感器 *tan(M*θ / 2) Where θ is the field of view of the star sensor (5) corresponding to the field of view n, X n is the coordinate value of the detector imaging position of the star sensor (5) in the field of view n in the azimuth X direction, Y n is the coordinate value of the detector imaging position point of the star sensor (5) in the pitch Y direction in the field of view n, M=0.8, indicating a field of view of 0.

8.

8. The star sensor automatic focusing test method according to claim 7, characterized in that: In step S8, the thickness of the focus ring is adjusted according to the trimming amount of the focus ring, specifically: If the trimming amount of the focus ring is a negative value, replace it with a thick focus ring, and the increased thickness of the focus ring is the absolute value of the trimming amount; if the trimming amount of the focus ring is a positive value, replace it with a thin focus ring, and the reduced thickness of the focus ring is the value of the trimming amount.

9. The star sensor automatic focusing test method according to claim 2, characterized in that: Step S1 is specifically as follows: S1.

1. Calculate the star point moving step S according to the following formula and round the result; Wherein, DOF is the focal depth of the star sensor (5), F / # is the F number of the star sensor (5), and λ is the central wavelength of the star sensor (5); S1.

2. Determine and select the appropriate target simulation subsystem by the following methods; Calculate S×N, where N is the total number of steps moved back and forth at the initial position of the image acquisition when acquiring the image, and define L as the total stroke of the translation stage (9) in the first target simulation subsystem (1); If S×N>L, select the second target simulation subsystem (2), otherwise select the first target simulation subsystem (1); S1.

3. Calculate the star point size d according to the following formula 星点 : Where D is the entrance pupil diameter of the star sensor (5).

Images