Space camera focusing method

Abstract

The present application relates to the technical field of optical detection, and particularly relates to a focusing method of a space camera, which comprises the following steps: S1, placing a focal plane detector at a designed installation position of the space camera; S2, placing an interferometer at a center position of an entrance of the space camera; S3, adjusting an adjusting table to determine a central field of view of the space camera; S4, calculating a central-aperture central field of view best focal plane distance; S5, calculating a central-aperture central field of view best focal plane distance of other aperture positions; S6, calculating an average central field of view best focal plane distance; S7, calculating an average first edge field of view best focal plane distance; S8, calculating an average second edge field of view best focal plane distance; S9, calculating a full field of view equivalent best focal plane position; S10, calculating a full field of view correction best focal plane distance; and S11, moving the focal plane detector to a specified position. The present application is suitable for space cameras of various optical forms and various apertures, and has the characteristics of simple operation, low cost and strong adaptability.

Description

Technical Field

[0001] This invention relates to the field of optical detection technology, and more particularly to a focusing method for a space camera. Background Technology

[0002] Determining the focal plane is an essential assembly and adjustment process in the development of space cameras. It involves accurately positioning the focal plane detector of the space camera. The current method simulates targets at infinity using a collimator, followed by imaging tests with the space camera. The optimal position of the focal plane detector is determined by assessing the image sharpness, and then the detector is installed. This method requires not only a collimator matched to the space camera system parameters but also precise calibration of the collimator's focal plane position. Therefore, this method is limited by laboratory conditions, and for large-aperture space cameras, a collimator with a similar aperture and a focal length 3-5 times that of the space camera is needed, increasing the development cost. Summary of the Invention

[0003] This invention addresses the limitations of existing fixed-focus methods in laboratory conditions and the high development cost of large-aperture space cameras, which require matching collimators with similar apertures and focal lengths 3-5 times that of the space camera. This invention provides a fixed-focus method for space cameras, applicable to various optical types and apertures, simple to operate, and low in cost. The specific steps include:

[0004] S1. Place the focal plane detector in the designed installation position of the space camera.

[0005] S2. Fix the interferometer on the adjustment table, adjust the interferometer to the center position of the light inlet of the space camera using the adjustment table, and install a standard plane mirror lens on the interferometer.

[0006] S3. Adjust the angle of the interferometer by adjusting the adjustment table, and adjust the focal point formed by the convergence of parallel light on the focal plane detector to the center position of the focal plane detector. The center position of the focal plane is the center field of view of the space camera.

[0007] S4. Move the focal plane detector along the optical axis of the space camera until the fringes displayed on the interferometer are in a straight line. The location of the focal plane detector is the optimal focal plane position of the center field of view of the center aperture. Obtain the distance d1 between the optimal focal plane position of the center field of view of the center aperture and the designed installation position.

[0008] S5. Adjust the position of the interferometer by adjusting the horizontal or vertical position of the stage so that the parallel light converges from the center position of the light inlet to the focal plane detector. Repeat step S4 to obtain the distance di between the other aperture positions and the designed installation position, except for the optimal focal plane position of the center field of view of the center aperture.

[0009] S6. Calculate the average optimal focal plane position distance dM of the center field of view of the space camera:

[0010] dM=(d1+…+di) / i (1);

[0011] Where i is the number of positions the interferometer moves at the entrance aperture in order to calculate the average optimal focal distance of the central field of view;

[0012] S7. Adjust the angle of the interferometer using the adjustment stage to move the focal point of the parallel light to the first edge position of the focal plane detector. The first edge position is the first edge field of view. Repeat steps S4-S6 to obtain the average optimal focal plane distance dE1 of the first edge field of view.

[0013] dE1=(d1`+…+ di`) / i` (2);

[0014] Where d1` is the distance between the optimal focal plane position of the first edge of the central aperture and the designed installation position, di` is the distance between the other aperture positions (excluding the optimal focal plane position of the first edge of the central aperture) and the designed installation position, and i` is the number of positions the interferometer moves at the entrance port in order to calculate the average optimal focal plane distance of the first edge field of view.

[0015] S8. Adjust the angle of the interferometer using the adjustment stage to move the focal point of the parallel light to the second edge position of the focal plane detector. The second edge position does not coincide with the first edge position. The second edge position is the second edge field of view. Repeat steps S4-S6 to obtain the average optimal focal plane distance dE2 of the second edge field of view.

[0016] dE2=(d1``+...+ di``) / i`` (3);

[0017] Where d1`` is the distance between the optimal focal plane position of the second edge of the center aperture and the designed installation position, di`` is the distance between the aperture position other than the optimal focal plane position of the second edge of the center aperture and the designed installation position, and i`` is the number of positions the interferometer moves at the entrance aperture in order to calculate the average optimal focal plane distance of the second edge field of view.

[0018] S9. Calculate the equivalent optimal focal plane position d across the entire field of view:

[0019] d=W1*dE1+W2*dM+W3*dE2 (4);

[0020] Among them, W1, W2, and W3 are all weighting factors, and W1 + W2 + W3 = 1;

[0021] S10. Calculate the corrected optimal focal distance d0 for the entire field of view using the equivalent optimal focal plane position for the entire field of view:

[0022] d0 = da (5);

[0023] Where a is the axial distance between the protective window of the focal plane detector and the photosensitive pixel;

[0024] S11. Move the focal plane detector to the designated position according to the optimal focal plane distance corrected for the entire field of view.

[0025] Preferably, the distances d1 between the optimal focal plane position of the center aperture and the designed installation position, di between other aperture positions (excluding the optimal focal plane position of the center aperture) and the designed installation position, dM between the average optimal focal plane position of the center field of view, d1' between the optimal focal plane position of the first edge of the center aperture and the designed installation position, di' between other aperture positions (excluding the optimal focal plane position of the first edge of the center aperture) and the designed installation position, dE1 between the average optimal focal plane position of the first edge of the first aperture, d1'' between the optimal focal plane position of the second edge of the center aperture and the designed installation position, di'' between other aperture positions (excluding the optimal focal plane position of the second edge of the center aperture) and the designed installation position, dE2 between the average optimal focal plane position of the second edge of the second aperture, d of the equivalent optimal focal plane position of the entire field of view, and d0 of the corrected optimal focal plane position of the entire field of view are positive when the focal plane detector is placed between the designed installation position and the interferometer, and negative otherwise.

[0026] Preferably, in step S11, if the optimal focal distance for full field-of-view correction is positive, the focal detector is moved from the designed installation position toward the direction of the interferometer; otherwise, the focal detector is moved from the designed installation position toward the opposite direction of the interferometer.

[0027] Preferably, the adjustment platform is a five-dimensional adjustment platform used to adjust the pitch angle, swing angle, horizontal position, and vertical position of the outgoing light from the interferometer. Compared with the prior art, the present invention can achieve the following beneficial effects:

[0028] The fixed-focus method for space cameras proposed in this invention does not rely on complex equipment and is applicable to space cameras of various optical forms and apertures. It features simple operation, low cost, and strong adaptability. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating the focusing method for a space camera according to an embodiment of the present invention;

[0030] Figure 2 This is a schematic diagram of the alignment of an interferometer and a space camera according to an embodiment of the present invention;

[0031] Figure 3This is a schematic diagram of five positions measured by an interferometer at the central field of view according to an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram showing the positions of the first edge field of view, the center field of view, and the second edge field of view according to an embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram showing the adjustment direction of the interferometer corresponding to each field of view position on the focal plane detector according to an embodiment of the present invention.

[0034] The attached figures are labeled as follows: interferometer 1, adjustment stage 2, space camera 3, focal plane detector 4. Detailed Implementation

[0035] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0037] Figure 1 The flowchart of a focusing method for a space camera provided according to an embodiment of the present invention is shown; Figure 2 The alignment of an interferometer and a space camera provided according to an embodiment of the present invention is shown.

[0038] like Figures 1-2 As shown, the focusing method for a space camera provided in this embodiment of the invention specifically includes the following steps:

[0039] S1. Place the focal plane detector 4 in the designed installation position of the space camera 3.

[0040] S2. Fix the interferometer 1 on the adjustment stage 2, adjust the interferometer 1 to the center position of the light inlet of the space camera 3 through the adjustment stage 2, and install a standard plane mirror lens on the interferometer 1.

[0041] S3. Adjust the angle of the interferometer 1 by adjusting the stage 2, and adjust the focus of the parallel light converged on the focal plane detector 4 to the center position of the focal plane of the focal plane detector 4. The center position of the focal plane is the center field of view of the space camera 3.

[0042] S4. Move the focal plane detector 4 along the optical axis of the space camera 3 until the fringes displayed on the interferometer 1 are in a straight line. The position of the focal plane detector 4 is the optimal focal plane position of the center field of view of the center aperture. Obtain the distance d1 between the optimal focal plane position of the center field of view of the center aperture and the designed installation position.

[0043] S5. Adjust the position of the interferometer 1 by adjusting the horizontal or vertical position of the stage 2 so that the parallel light converges from the center position of the light inlet to the focal plane detector 4. Repeat step S4 to obtain the distance di between the other aperture positions and the designed installation position, except for the optimal focal plane position of the center field of view of the center aperture.

[0044] S6. Calculate the average optimal focal plane position distance dM of the center field of view of space camera 3:

[0045] dM=(d1+…+di) / i (1);

[0046] Where i is the number of positions that interferometer 1 moves at the entrance port in order to calculate the average optimal focal distance of the central field of view.

[0047] Figure 3 Five positions measured at the central field of view by the interferometer 1 provided according to an embodiment of the present invention are shown.

[0048] like Figure 3 As shown, taking the five positions measured by interferometer 1 at the central field of view as an example, according to equation (1), the average optimal focal plane difference of the central field of view is: dM=(d1+…+d5) / 5.

[0049] Figure 4 The positions of the first edge field of view, the center field of view, and the second edge field of view provided according to an embodiment of the present invention are shown. Figure 5 A schematic diagram showing the adjustment direction of the interferometer corresponding to each field-of-view position on the focal plane detector provided according to an embodiment of the present invention is shown.

[0050] The embodiments of the present invention provide the positions of the first edge field of view, the central field of view, and the second edge field of view, as well as the orientation of the interferometer 1 adjusted according to each field of view, as follows: Figures 4-5 As shown.

[0051] S7. Adjust the angle of the interferometer 1 by adjusting the stage 2, so that the focal point of the interferometer 1 is moved to the first edge position of the focal plane detector 4. The first edge position is the first edge field of view. Repeat steps S4-S6 to obtain the average optimal focal plane distance dE1 of the first edge field of view.

[0052] dE1=(d1`+…+ di`) / i` (2);

[0053] Where d1` is the distance between the optimal focal plane position of the first edge of the central aperture and the designed installation position, di` is the distance between the other aperture positions (excluding the optimal focal plane position of the first edge of the central aperture) and the designed installation position, and i` is the number of positions that the interferometer 1 moves at the entrance port in order to calculate the average optimal focal plane distance of the first edge field of view.

[0054] S8. Adjust the angle of the interferometer 1 by adjusting the stage 2, so that the focal point of the parallel light moves to the second edge position of the focal plane detector 4. The second edge position does not coincide with the first edge position. The second edge position is the second edge field of view. Repeat steps S4-S6 to obtain the average optimal focal plane distance dE2 of the second edge field of view.

[0055] dE2=(d1``+...+di``) / i`` (3);

[0056] Where d1`` is the distance between the optimal focal plane position of the second edge of the center aperture and the designed installation position, di`` is the distance between the aperture position other than the optimal focal plane position of the second edge of the center aperture and the designed installation position, and i`` is the number of positions that the interferometer 1 moves at the entrance aperture in order to calculate the average optimal focal plane distance of the second edge field of view.

[0057] S9. Calculate the equivalent optimal focal plane position d across the entire field of view:

[0058] d=W1*dE1+W2*dM+W3*dE2 (4);

[0059] Among them, W1, W2, and W3 are all weighting factors, and W1 + W2 + W3 = 1.

[0060] S10. Calculate the corrected optimal focal distance d0 for the entire field of view using the equivalent optimal focal plane position for the entire field of view:

[0061] d0 = da (5);

[0062] Where a is the axial distance between the protective window of the focal plane detector 4 and the photosensitive pixel.

[0063] S11. Move the focal plane detector 4 to the designated position according to the optimal focal plane distance corrected for the entire field of view.

[0064] In step S11, if the optimal focal distance for full field of view correction is positive, the focal detector 4 is moved from the designed installation position toward the direction of the interferometer 1; if the optimal focal distance for full field of view correction is negative, the focal detector 4 is moved from the designed installation position toward the opposite direction of the interferometer 1.

[0065] The distances d1 between the optimal focal plane position of the center aperture and the designed installation position, di between other aperture positions (excluding the optimal focal plane position of the center aperture) and the designed installation position, dM between the average optimal focal plane position of the center field of view, d1` between the optimal focal plane position of the first edge of the center aperture and the designed installation position, di` between other aperture positions (excluding the optimal focal plane position of the first edge of the center aperture) and the designed installation position, dE1 between the average optimal focal plane position of the first edge of the first aperture and the designed installation position, d1`` between the optimal focal plane position of the second edge of the center aperture and the designed installation position, di`` between other aperture positions (excluding the optimal focal plane position of the second edge of the center aperture) and the designed installation position, dE2 between the average optimal focal plane position of the second edge of the second aperture, d1`` between the equivalent optimal focal plane position of the entire field of view and the designed installation position, and d0 between the corrected optimal focal plane position of the entire field of view and the designed installation position are positive when the focal plane detector 4 is placed between the designed installation position and the interferometer 1, and negative when the focal plane detector 4 is placed on one side of the designed installation position.

[0066] Adjustment stage 2 is a five-dimensional adjustment platform used to adjust the pitch angle, swing angle, horizontal position, and vertical position of the emitted light from interferometer 1.

[0067] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0068] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for fixing the focus of a space camera, characterized in that, Specifically, the steps include the following: S1. Place the focal plane detector at the designed installation position of the space camera; S2. Fix the interferometer on the adjustment table, adjust the interferometer to the center position of the light inlet of the space camera using the adjustment table, and install a standard plane mirror lens on the interferometer; S3. Adjust the angle of the interferometer through the adjustment table to adjust the focal point of the parallel light converged on the focal plane detector to the center position of the focal plane detector. The center position of the focal plane is the center field of view of the space camera. S4. Move the focal plane detector along the optical axis of the space camera until the fringes displayed on the interferometer are in a straight line. The location of the focal plane detector is the optimal focal plane position of the center field of view of the center aperture. Obtain the distance d1 between the optimal focal plane position of the center field of view of the center aperture and the designed installation position. S5. Adjust the position of the interferometer horizontally or vertically using the adjustment platform so that the parallel light converges from the center position of the light inlet to the focal plane detector. Repeat step S4 to obtain the distance di between the other aperture positions (excluding the optimal focal plane position of the center field of view of the center aperture) and the designed installation position. S6. Calculate the average optimal focal plane position distance dM of the center field of view of the space camera: dM=(d1+…+di) / i(1); Where i is the number of positions the interferometer moves at the entrance port in order to calculate the average optimal focal distance of the central field of view; S7. Adjust the angle of the interferometer using the adjustment stage to move the focal point of the parallel light to the first edge position of the focal plane detector. The first edge position is the first edge field of view. Repeat steps S4-S6 to obtain the average optimal focal plane distance dE1 of the first edge field of view. dE1=(d1`+…+ di`) / i`(2); Wherein, d1` is the distance between the optimal focal plane position of the first edge of the central aperture and the designed installation position, di` is the distance between the other aperture positions besides the optimal focal plane position of the first edge of the central aperture and the designed installation position, and i` is the number of positions the interferometer moves at the entrance port in order to calculate the average optimal focal plane distance of the first edge field of view. S8. Adjust the angle of the interferometer using the adjustment stage to move the focal point of the parallel light to the second edge position of the focal plane detector. The second edge position does not coincide with the first edge position. The second edge position is the second edge field of view. Repeat steps S4-S6 to obtain the average optimal focal plane distance dE2 of the second edge field of view. dE2=(d1``+…+ di``) / i``(3); Wherein, d1`` is the distance between the optimal focal plane position of the second edge of the center aperture and the designed installation position, di`` is the distance between the other aperture positions besides the optimal focal plane position of the second edge of the center aperture and the designed installation position, and i`` is the number of positions the interferometer moves at the entrance port in order to calculate the average optimal focal plane distance of the second edge field of view. S9. Calculate the equivalent optimal focal plane position d across the entire field of view: d=W1 dE1+W2 dM+W3 dE2(4); Among them, W1, W2, and W3 are all weighting factors, and W1 + W2 + W3 = 1; S10. Calculate the corrected optimal focal distance d0 for the entire field of view using the equivalent optimal focal plane position for the entire field of view: d0=da(5; Where a is the axial distance between the protective window of the focal plane detector and the photosensitive pixel; S11. Move the focal plane detector to the designated position according to the full field-of-view correction optimal focal plane distance; The distances d1 between the optimal focal plane position of the center aperture and the designed installation position, di between other aperture positions (excluding the optimal focal plane position of the center aperture) and the designed installation position, dM between the average optimal focal plane position of the center field of view, d1` between the first edge optimal focal plane position of the center aperture and the designed installation position, di` between other aperture positions (excluding the first edge optimal focal plane position of the center aperture) and the designed installation position, dE1 between the first edge field of view, d1`` between the second edge optimal focal plane position of the center aperture and the designed installation position, di`` between other aperture positions (excluding the second edge optimal focal plane position of the center aperture) and the designed installation position, dE2 between the second edge field of view, d1`` between the equivalent optimal focal plane position d of the entire field of view, and d0 between the corrected optimal focal plane position d of the entire field of view and the interferometer are positive when the focal plane detector is placed between the designed installation position and the interferometer, and negative otherwise.

2. The focusing method for a space camera according to claim 1, characterized in that, In step S11, if the full field-of-view correction optimal focal plane distance is positive, the focal plane detector is moved from the designed installation position toward the direction of the interferometer; otherwise, the focal plane detector is moved from the designed installation position toward the opposite direction of the interferometer.

3. The focusing method for a space camera according to claim 1, characterized in that, The adjustment platform is a five-dimensional adjustment platform used to adjust the pitch angle, swing angle, horizontal position, and vertical position of the emitted light from the interferometer.

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