X-ray optical system angular resolution calibration system and method

Abstract

The invention discloses an angular resolution calibration system for an X-ray optical system. The system comprises a multi-degree-of-freedom turntable, an X-ray imaging detector, a diaphragm, a filter disc, a monochromator, an X-ray light source, a test cavity and a computer. The invention also discloses an X-ray optical system angular resolution calibration method, which comprises the following steps of: adjusting the position and the posture of the detected optical system through the multi-degree-of-freedom turntable, so that the detected optical system is aligned with the X-ray light source; the test cavity is vacuumized; the position of the detected optical system is adjusted, so that X-rays emitted by the X-ray light source are respectively incident to each calibration position of the clear aperture of the optical system, the X-ray imaging detector images light spots focused at each calibration position, and the light spots are stored in the computer; and the computer carries out splicing processing on all the light spots, the angular resolution is obtained according to the spliced light spots, and calibration of the angular resolution is completed. The method has the advantages of being wide in application range, high in accuracy, easy to implement and the like, and difficulty and investment can be effectively reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of space optics and relates to an angular resolution calibration system and method for an X-ray optical system. Background Art

[0002] X-ray pulsar navigation is suitable for fully autonomous navigation of near-Earth space, deep space exploration and interstellar flight spacecraft. It can provide comprehensive navigation information such as position, speed, attitude and time for most space mission spacecraft, and realize fully autonomous navigation of spacecraft. It has the advantages of strong reliability, good stability, high accuracy and wide applicability. It is a new autonomous navigation technology with great development potential and has extremely important engineering practical value and strategic research significance.

[0003] The core of the X-ray pulsar navigation sensor is the X-ray optical system. As an X-ray optical system with high efficiency and strong environmental adaptability, the X-ray grazing incidence optical system is the main development trend in the future. Angular resolution is the core performance indicator of X-ray grazing incidence optics, which determines the focusing and resolving power of the optical system, and thus affects the signal-to-noise ratio and navigation accuracy of the X-ray pulsar navigation sensor. Due to its large optical aperture and strict requirements on the collimation of the incident X-rays, as well as the fact that X-rays are easily absorbed in the air, the calibration of angular resolution often requires a vacuum calibration beamline of hundreds of meters, which requires huge investment in space and funds. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned defects and provide an X-ray optical system angular resolution system and method, which solves the technical problem that the existing X-ray optical system angular resolution calibration method requires huge space and financial investment. The present invention has the advantages of wide application range, high accuracy, and easy implementation, and can effectively reduce the difficulty and investment.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] An X-ray optical system angular resolution calibration system, comprising: a multi-degree-of-freedom turntable, an X-ray imaging detector, an aperture, a filter, a monochromator, an X-ray light source, a test cavity and a computer;

[0007] The optical system under test and the X-ray imaging detector are installed on a multi-degree-of-freedom turntable; the X-ray light source is installed inside the test cavity; the multi-degree-of-freedom turntable is used to adjust the position of the optical system under test so that the X-rays emitted by the X-ray light source pass through the monochromator, the filter and the diaphragm in sequence and then are incident on the calibrated positions of the light aperture of the optical system under test; the X-ray imaging detector is used to obtain the light spots when the X-rays are incident on the calibrated positions of the light aperture of the optical system under test, and save them to the computer; the computer is used to splice all the light spots to obtain the spliced ​​light spots, and complete the angular resolution calibration based on the spliced ​​light spots.

[0008] Furthermore, the aperture, the filter and the monochromator are installed inside the test cavity; the centers of the aperture, the filter, the monochromator and the X-ray light source are located on a straight line;

[0009] The distance between the optical system under test and the X-ray light source is not less than 20m;

[0010] The optical system to be measured and the X-ray light source are located at the rear and front respectively, the diaphragm and the filter are arranged 20 mm ± 2 mm in front of the aperture of the optical system to be measured, and the monochromator is arranged 30 mm ± 2 mm behind the light outlet of the X-ray light source.

[0011] Further, the X-ray imaging detector is located at the focal plane of the optical system under test;

[0012] The focus of the optical system under test is located at the center of the sensitive surface of the X-ray imaging detector. The deviation between the focus of the optical system and the center of the sensitive surface of the X-ray imaging detector in the direction perpendicular to the optical axis is less than 10 pixels. The deviation between the sensitive surface of the X-ray imaging detector and the focal plane of the optical system in the direction of the optical axis is less than 0.5 mm, and the parallelism between the normal of the sensitive surface and the optical axis is better than 5′.

[0013] Further, it also includes a visible laser source installed inside the test cavity;

[0014] The alignment between the optical system under test and the X-ray light source is achieved through a visible laser source and a reference mirror on the optical system under test;

[0015] When installing the visible laser source, ensure that the parallelism between its emitted light and the emitted light of the X-ray source is better than 3', and the relative position between the emitted light of the visible laser source and the emitted light of the X-ray source in the direction perpendicular to the optical axis is known; when gluing the reference mirror, ensure that the parallelism between the normal line of the reference mirror and the optical axis of the optical system is better than 2'.

[0016] A method for calibrating an angular resolution of an X-ray optical system is implemented by using the above-mentioned angular resolution calibration system of an X-ray optical system, comprising:

[0017] S1 adjusts the position and posture of the optical system under test through a multi-degree-of-freedom turntable to align the optical system under test with the X-ray light source;

[0018] S2 evacuates the test chamber;

[0019] S3 adjusts the position of the optical system under test through a multi-degree-of-freedom turntable so that the X-rays emitted by the X-ray light source are incident on the calibrated positions of the optical system aperture respectively. The X-ray imaging detector images the light spots focused at the calibrated positions and saves the light spots to the computer;

[0020] The S4 computer stitches all the light spots in the same coordinate system to obtain stitched light spots, and obtains the angular resolution based on the stitched light spots to complete the angular resolution calibration.

[0021] Furthermore, in step S1, the method for aligning the optical system to be measured with the X-ray light source includes:

[0022] The X-rays emitted by the X-ray light source are completely incident on the aperture of the optical system, and the incident direction of the X-rays is parallel to the optical axis of the optical system;

[0023] In steps S1 and S3, when the multi-degree-of-freedom turntable adjusts the position of the optical system to be measured, the relative position between the X-ray imaging detector and the optical system to be measured is fixed.

[0024] Furthermore, in step S1, the alignment between the optical system under test and the X-ray light source is achieved by a visible laser source installed inside the test cavity and a reference mirror on the optical system under test, the parallelism between the outgoing light of the visible laser source and the outgoing light of the X-ray light source is better than 3', and the relative position in the direction perpendicular to the optical axis is known, and the parallelism between the normal of the reference mirror and the optical axis of the optical system is better than 2'.

[0025] Furthermore, in step S2, the test chamber is evacuated to a vacuum degree of 10 -5 When it reaches Pa level, vacuum pumping is completed.

[0026] Furthermore, in step S3, assuming that the diameter of the circular hole of the aperture is d, the side length of the square inscribed in the circular hole is The diameter of the aperture of the optical system under test is d1, and the side length of the circumscribed square of the aperture is 2d1, so the total number of calibration positions is Ensure that n calibration positions cover the clear aperture of the entire optical system;

[0027] The incident light spots at the i-th calibration position and the i-1-th calibration position partially overlap; i=2, ..., n.

[0028] Furthermore, in step S4, the method of obtaining the angular resolution according to the spliced ​​light spots includes:

[0029] First, the centroid position of the spliced ​​light spot is determined by the centroid extraction algorithm, and then a circle is drawn with the centroid as the center so that the light spot energy contained in the circle is 1 / 2 of the total energy of the spliced ​​light spot. The angular resolution HPD is calculated by the diameter D of the circle and the focal length f of the optical system, that is,

[0030] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0031] (1) The angular resolution calibration method proposed in the present invention can realize the rapid and accurate calibration of the angular resolution of large-aperture optical systems, and provide feedback and guidance for the processing technology of reflectors and the assembly and integration of optical systems;

[0032] (2) The present invention realizes scanning multiple positions of the aperture of the optical system by a highly collimated narrow beam under vacuum state, without the need for a large beam that can only be achieved over a long distance, thus reducing the difficulty of calibration and greatly improving the calibration efficiency;

[0033] (3) The present invention provides a method for determining the calibration position. By splicing the incident light spots at each calibration position, the spliced ​​light spot can be accurately and efficiently obtained, which is beneficial to improving the calculation accuracy of the angular resolution;

[0034] (4) The present invention provides a method for aligning a calibration light source with an optical system to be measured, which can quickly achieve accurate alignment and improve calibration efficiency and accuracy;

[0035] (5) The present invention provides a specific method for obtaining angular resolution based on spliced ​​light spots, which has important theoretical guiding significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the angular resolution calibration system of the present invention;

[0037] Figure 2 This is a schematic diagram of the scanning sequence of the light incident aperture of the present invention;

[0038] Figure 3 A schematic diagram of a focused light spot of a small light beam incident on a single position of a clear aperture of the present invention;

[0039] Figure 4 It is a schematic diagram of obtaining angular resolution based on spot processing of the present invention;

[0040] Among them, 1-optical system to be tested, 2-optical system bracket, 3-multi-degree-of-freedom turntable, 4-X-ray imaging detector, 5-detector bracket, 6-monochromator, 7-X-ray light source, 8-filter; 9-aperture, 10-test cavity, 11-cabin connector, 12-cable, 13-computer, 14-visible laser light source. DETAILED DESCRIPTION

[0041] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0042] The word "exemplary" is used exclusively herein to mean "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise noted.

[0043] The present invention is based on a vacuum beam line and proposes a method for calibrating the angular resolution of an X-ray optical system. The method uses an X-ray tube as a calibration light source, obtains a monoenergetic collimated X-ray beam through a monochromator and an aperture, scans the aperture of the optical system through the X-ray beam, records the light spot after being focused by the optical system, and obtains the angular resolution of the optical system through relevant processing and calculation. The method has the advantages of wide application range, high accuracy, and easy implementation, and can effectively reduce the difficulty and investment.

[0044] The present invention provides an X-ray optical system angular resolution calibration system, comprising a multi-degree-of-freedom turntable 3, an X-ray imaging detector 4, an aperture 9, a filter 8, a monochromator 6, an X-ray light source 7, a test cavity 10 and a computer 13; in a specific embodiment, it also includes a visible laser source 14. The X-ray optical system angular resolution calibration system is installed according to the following steps:

[0045] Step 1: Mount the optical system 1 to be measured on the multi-degree-of-freedom turntable 3 through the optical bracket 2;

[0046] Step 2: Install the X-ray imaging detector 4 on the multi-degree-of-freedom turntable 3 through the detector bracket 5, so that the X-ray imaging detector 4 is located at the focal plane position of the optical system 1 to be measured, and keep the relative position between the two fixed during the calibration process;

[0047] Step 3: Install the X-ray light source 7 and the visible laser source 14 into the test cavity, and adjust the position and posture of the optical system 1 under test by the multi-degree-of-freedom turntable 3 so that it is aligned with the X-ray light source 7. The alignment includes two aspects: the X-rays emitted by the light source are completely incident within the aperture range of the optical system 1, and the incident direction of the X-rays is parallel to the optical axis of the optical system 1;

[0048] Step 4: Install the aperture 9, filter 8 and monochromator 6 on the optical path between the optical system 1 to be tested and the X-ray light source 7 in the test cavity 10; use the through-cabin connector 11 and cable 12 to connect the X-ray imaging detector 4 to the computer 13 located outside the test cavity 10.

[0049] The present invention also provides an X-ray optical system angular resolution calibration method implemented by using the above X-ray optical system angular resolution calibration system, comprising:

[0050] Step 1: Check the situation in the test chamber 10. After confirming that everything is correct, close the test chamber 10 and evacuate the chamber. When the vacuum degree reaches 10 -5 When the level reaches Pa, vacuuming is completed;

[0051] Step 2: adjusting the position of the optical system 1 to be measured by the multi-degree-of-freedom turntable 3 so that the X-ray is incident on the position 1 of the light aperture of the optical system 1;

[0052] Step 3: Use the X-ray imaging detector 4 to image the light spot focused at position 1 of the optical system 1 to be measured, and save the recorded light spot to the computer 13;

[0053] Step 4: adjust the position of the optical system 1 to be measured by the multi-degree-of-freedom turntable 3 so that the X-ray is incident on the position i of the optical system 1, where i=2, ..., n, and n is the total number of calibration positions covering the entire optical aperture of the optical system, which can be obtained based on the diameter of the incident X-ray beam and the diameter of the optical aperture of the optical system 1. The incident light spots at the position i and the position i-1 partially overlap;

[0054] Step 5: Use the X-ray imaging detector 4 to image the light spot focused at position i of the optical system 1 to be measured, and save the recorded light spot to the computer 13;

[0055] Step 6: Repeat steps 4 to 5 until all positions are calibrated;

[0056] Step 7: stitch all the recorded light spots in the same coordinate system to obtain a stitched light spot that is equivalent to the focused light spot of the optical system under test, perform image processing on the stitched light spot, and calculate the angular resolution according to the corresponding algorithm to complete the angular resolution calibration.

[0057] Furthermore, the focus of the optical system 1 under test is located at the center of the sensitive surface of the X-ray imaging detector 4, the deviation between the focus and the center of the sensitive surface in the direction perpendicular to the optical axis is less than 10 pixels, the deviation between the sensitive surface and the focal plane along the optical axis is less than 0.5 mm, and the parallelism between the normal of the sensitive surface and the optical axis is better than 5′.

[0058] Furthermore, the alignment between the measured optical system 1 and the X-ray light source 7 is achieved through the visible laser source 14 and the reference mirror on the measured optical system 1, the parallelism between the output light of the visible laser source 14 and the output light of the X-ray light source 7 is better than 3', and the relative position in the direction perpendicular to the optical axis is known, and the parallelism between the normal of the reference mirror and the optical axis of the optical system is better than 2'.

[0059] Furthermore, the centers of the aperture 9, the filter 8, the monochromator 6 and the X-ray light source 7 are located in a straight line, the distance between the optical system 1 to be measured and the X-ray light source 7 is not less than 20m, the aperture 9 and the filter 8 are arranged 20mm±2mm in front of the light aperture of the optical system 1 to be measured, and the monochromator 6 is arranged 30mm±2mm from the light outlet of the X-ray light source 7.

[0060] Furthermore, the union of the incident light spots at n positions needs to completely cover the clear aperture of the optical system under test.

[0061] Furthermore, the method of performing image processing on the spliced ​​light spot and calculating the angular resolution according to the corresponding algorithm includes: determining the center of mass position of the spliced ​​light spot by the center of mass extraction algorithm, and then drawing a circle with the center of mass as the center so that the light spot energy contained in the circle is 1 / 2 of the total energy of the spliced ​​light spot, and the angular resolution HPD is calculated by the diameter D of the circle and the focal length f of the optical system, that is,

[0062] In summary, the technical solution of the present invention includes the steps of installing the optical system to be measured, installing the X-ray imaging detector, installing the aperture and the filter, installing the monochromator and the X-ray light source, evacuating the vacuum, adjusting the optical system before calibration, turning on the X-ray source, recording the imaging spot of the optical system to the incident X-ray, adjusting the position of the optical system to be measured, recording the imaging spot of another area of ​​the optical system to the incident X-ray, repeating the position adjustment and spot recording for multiple times until the entire aperture of the optical system is calibrated, splicing all the spots into one spot through aperture splicing, and finally calculating the angular resolution using an algorithm. The present invention has high efficiency, a wide range of applications, and is easy to implement.

[0063] Example:

[0064] The angular resolution calibration method for the X-ray optical system mainly includes the following steps:

[0065] Step 1: First, prepare the Wolter-I type X-ray optical system to be calibrated; clean the optical system and related tooling equipment with alcohol;

[0066] Step 2: Figure 1 , install the optical system to be tested and related tooling equipment inside and outside the test chamber, where the distance L between the optical system to be tested and the X-ray light source is greater than 20m to ensure that the divergence angle of the X-ray beam is small (less than 2'), detect the relative relationship between the X-ray light source and the optical system to be tested through a visible laser source with a known relative relationship with the X-ray light source and a reference mirror of the optical system to be tested, and adjust the position and posture of the optical system through a multi-degree-of-freedom turntable to ensure that the parallelism between the X-ray optical axis emitted by the X-ray light source and the optical axis of the optical system is better than 5', and the position deviation between the center of the X-ray beam and the center of the optical system to be tested is less than 0.5mm. After the adjustment is completed and the status of each device is confirmed to be correct, close the test chamber and evacuate to the required vacuum degree.

[0067] Step 3: Turn on the X-ray light source and adjust the position of the optical system to be measured by the multi-degree-of-freedom turntable. Figure 2The scanning sequence shown in the figure is that the circular light beam inscribes a small square (shown by the dotted line in the figure) to scan the circumscribed large square (shown by the dotted line in the figure) of the optical system aperture line by line, and the side lengths of the small squares at adjacent positions overlap, so that the X-ray beam is aligned with positions 1 to n of the optical system in sequence, ensuring that the n positions can completely cover the entire aperture of the optical system. After each alignment, the X-ray imaging detector is used to collect and record the focused light spot, and a total of n spots are obtained as shown in the figure. Figure 3 The light spot shown is two symmetrically distributed sectors, with more photons near the center and fewer photons near the edge;

[0068] Step 4: Splice all the recorded light spots in the same coordinate system to obtain the equivalent focused light spot of the optical system under test. The spliced ​​light spot is as follows: Figure 4 As shown in the figure, the image processing of the spliced ​​light spot is firstly carried out by using the centroid extraction algorithm to determine the centroid position of the spliced ​​light spot, and then a circle is drawn with the centroid as the center so that the light spot energy contained in the circle is 1 / 2 of the total energy of the spliced ​​light spot. The angular resolution HPD is calculated by the diameter D of the circle and the focal length f of the optical system, that is, The unit is arc seconds.

[0069] The present invention has been described in detail above in conjunction with specific implementations and exemplary examples, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements may be made to the technical solution of the present invention and its implementation methods, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0070] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. An angular resolution calibration system for an X-ray optical system, characterized in that: include: A multi-degree-of-freedom turntable (3), an X-ray imaging detector (4), an aperture (9), a filter (8), a monochromator (6), an X-ray light source (7), a test chamber (10) and a computer (13); The optical system to be tested (1) and the X-ray imaging detector (4) are mounted on a multi-degree-of-freedom turntable (3); the X-ray light source (7) is mounted inside a test cavity (10); the multi-degree-of-freedom turntable (3) is used to adjust the position of the optical system to be tested (1) so that the X-rays emitted by the X-ray light source (7) pass through a monochromator (6), a filter (8) and an aperture (9) in sequence and then are incident on each calibrated position of the light aperture of the optical system to be tested (1); The X-ray imaging detector (4) is used to obtain light spots when X-rays are incident on each calibrated position of the light aperture of the optical system (1) under test, and store the light spots in a computer (13); the computer (13) is used to perform splicing processing on all the light spots to obtain spliced ​​light spots, and complete angular resolution calibration based on the spliced ​​light spots.

2. The X-ray optical system angular resolution calibration system according to claim 1, characterized in that: The aperture (9), the filter (8) and the monochromator (6) are installed inside the test cavity (10); the centers of the aperture (9), the filter (8), the monochromator (6) and the X-ray light source (7) are located on a straight line; The distance between the optical system (1) to be measured and the X-ray light source (7) is not less than 20 m; The optical system (1) to be measured and the X-ray light source (7) are located at the rear and front, respectively, the aperture (9) and the filter (8) are arranged 20 mm±2 mm in front of the light aperture of the optical system (1) to be measured, and the monochromator (6) is arranged 30 mm±2 mm behind the light outlet of the X-ray light source (7).

3. The X-ray optical system angular resolution calibration system according to claim 1, characterized in that: The X-ray imaging detector (4) is located at the focal plane of the optical system (1) under test; The focus of the optical system (1) under test is located at the center of the sensitive surface of the X-ray imaging detector (4), the deviation between the focus of the optical system (1) and the center of the sensitive surface of the X-ray imaging detector (4) in the direction perpendicular to the optical axis is less than 10 pixels, the deviation between the sensitive surface of the X-ray imaging detector (4) and the focal plane of the optical system (1) in the direction of the optical axis is less than 0.5 mm, and the parallelism between the normal line of the sensitive surface and the optical axis is better than 5′.

4. The X-ray optical system angular resolution calibration system according to claim 1, characterized in that: Also included is a visible laser source (14) installed inside the test cavity (10); Alignment between the optical system (1) to be measured and the X-ray light source (7) is achieved through a visible laser source (14) and a reference mirror on the optical system (1) to be measured; When installing the visible laser source (14), ensure that the parallelism between its emitted light and the emitted light of the X-ray light source (7) is better than 3', and at the same time, the relative position between the emitted light of the visible laser source (14) and the emitted light of the X-ray light source (7) in the direction perpendicular to the optical axis is known; when bonding the reference mirror, ensure that the parallelism between the normal line of the reference mirror and the optical axis of the optical system is better than 2'.

5. A method for calibrating the angular resolution of an X-ray optical system, characterized in that: The method is implemented by using an X-ray optical system angular resolution calibration system as claimed in any one of claims 1 to 4, comprising: S1 adjusts the position and posture of the optical system (1) to be measured by means of a multi-degree-of-freedom turntable (3) so that the optical system (1) to be measured is aligned with the X-ray light source (7); S2 evacuates the test chamber (10); S3 adjusts the position of the optical system (1) to be measured by means of a multi-degree-of-freedom turntable (3), so that the X-rays emitted by the X-ray light source (7) are incident on the respective calibrated positions of the light aperture of the optical system (1), and the X-ray imaging detector (4) forms an image of the light spot focused at each calibrated position, and stores the light spot in a computer (13); S4 computer (13) performs splicing processing on all the light spots in the same coordinate system to obtain spliced ​​light spots, obtains angular resolution according to the spliced ​​light spots, and completes angular resolution calibration.

6. The method for calibrating the angular resolution of an X-ray optical system according to claim 5, characterized in that: In step S1, the method for aligning the optical system (1) to be measured with the X-ray light source (7) comprises: The X-rays emitted by the X-ray light source (7) are completely incident on the light aperture of the optical system (1), and the incident direction of the X-rays is parallel to the optical axis of the optical system (1); In steps S1 and S3, when the multi-degree-of-freedom turntable (3) adjusts the position of the optical system (1) to be measured, the relative position between the X-ray imaging detector (4) and the optical system (1) to be measured is fixed.

7. The method for calibrating the angular resolution of an X-ray optical system according to claim 5, characterized in that: In step S1, the alignment between the optical system (1) to be measured and the X-ray light source (7) is achieved by a visible laser source (14) installed inside the test cavity (10) and a reference mirror on the optical system (1) to be measured, the parallelism between the emitted light of the visible laser source (14) and the emitted light of the X-ray light source (7) is better than 3', and the relative position in the direction perpendicular to the optical axis is known, and the parallelism between the normal line of the reference mirror and the optical axis of the optical system is better than 2'.

8. The method for calibrating the angular resolution of an X-ray optical system according to claim 5, characterized in that: In step S2, the test chamber (10) is evacuated until the vacuum degree reaches 10 -5 When it reaches Pa level, vacuum pumping is completed.

9. The method for calibrating the angular resolution of an X-ray optical system according to claim 5, characterized in that: In step S3, assuming that the diameter of the circular hole of the aperture (9) is d, the side length of the square inscribed in the circular hole is The diameter of the aperture of the optical system (1) under test is d1, and the side length of the circumscribed square of the aperture is d1, so the total number of calibration positions is Ensuring that the n calibration positions cover the clear aperture of the entire optical system (1); There is a partial overlap between the incident light spots at the i-th calibration position and the i-1-th calibration position; i=2, ..., n.

10. The method for calibrating the angular resolution of an X-ray optical system according to claim 5, characterized in that: In step S4, the method of obtaining the angular resolution according to the spliced ​​light spots includes: First, the centroid position of the spliced ​​light spot is determined by the centroid extraction algorithm. Then a circle is drawn with the centroid as the center so that the light spot energy contained in the circle is 1 / 2 of the total energy of the spliced ​​light spot. The angular resolution HPD is calculated from the diameter D of the circle and the focal length f of the optical system (1), that is,

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