A method for detecting lens errors of an X-ray focusing mirror

Abstract

The present invention relates to an alignment method for an X-ray focusing mirror, specifically to a method for detecting lens errors of an X-ray focusing mirror, which solves the technical problem in the prior art that the error type and error position of the lens during the alignment process of the X-ray focusing mirror cannot be distinguished. By analyzing the ring width data characteristics of the defocused spot image at different azimuth positions, the present invention determines the error type, and determines the position where the error occurs according to the defocused spot image. It can simply and effectively determine the attitude and the surface shape error position of the X-ray focusing mirror during the alignment process, which has never been adopted in previous X-ray optical systems, and is applicable to the alignment angle of an optical system with a large obscuration ratio and the determination of the intrinsic surface shape error.

Description

Technical Field

[0001] The present invention relates to a method for aligning an X-ray focusing mirror, and more particularly to a method for detecting lens errors of an X-ray focusing mirror. Background Art

[0002] An X-ray focusing mirror is a multi-layer nested system based on the principle of grazing incidence of X-rays. Its function is to focus X-ray photons. During the alignment process of the multi-layer nested structure, whether the multi-layer lenses are perpendicular, concentric, and free of defects are the main factors affecting the performance of the X-ray focusing mirror.

[0003] In recent years, with ultra-high angular resolution becoming one of the main development goals of next-generation X-ray focusing mirrors, how to improve the alignment accuracy of X-ray focusing mirrors has also become a technical problem that needs to be solved urgently. The main factors affecting the alignment accuracy of X-ray focusing mirrors include position errors and angular errors, and angular errors are the main factors affecting the angular resolution of X-ray focusing mirrors. Larger angular errors will affect the concentricity of the X-ray focusing mirror, thereby affecting the angular resolution of the X-ray focusing mirror. The surface profile error of the mirror surface of the X-ray focusing mirror is another important factor affecting the performance parameters of the X-ray focusing mirror. Detecting the surface profile error of the X-ray focusing mirror lens by optical means during the alignment process and screening the lenses are important means to improve the angular resolution of the X-ray focusing mirror.

[0004] In the currently disclosed technologies, there is no report on detecting the degree of lens errors of X-ray focusing mirrors and determining the types of lens errors of X-ray focusing mirrors. Therefore, it is necessary to provide a method for distinguishing the attitude error and surface profile error of the lenses during the alignment process of X-ray focusing mirrors, thereby improving the alignment accuracy of X-ray focusing mirrors. Summary of the Invention

[0005] The object of the present invention is to solve the technical problem of being unable to distinguish the types and positions of lens errors during the alignment process of X-ray focusing mirrors, and to provide a method for detecting lens errors of X-ray focusing mirrors.

[0006] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for detecting lens errors of an X-ray focusing mirror, characterized by comprising the following steps:

[0008] Step 1, measure the focal spot of the X-ray focusing mirror, determine the focal point position of the X-ray focusing mirror, and obtain the defocused spot image of the X-ray focusing mirror at the defocused position;

[0009] Step 2, if the defocused spot image of the measured X-ray focusing mirror is not in the form of a ring, the alignment error of the X-ray focusing mirror is large, and return to realign;

[0010] If the defocused spot image of the X-ray focusing mirror measured is in the form of a ring, proceed to Step 3;

[0011] Step 3: Process the defocused spot image to find the center point of the defocused spot image;

[0012] Step 4: Taking the center point of the defocused spot image as the reference point, divide the defocused spot image at different azimuth angles, and test and record the ring widths of the defocused spot image at different azimuth angle positions;

[0013] Step 5: Based on the ring width data at different azimuth angle positions, draw a curve graph showing the variation of the ring width of the defocused spot image with the azimuth angle position;

[0014] Step 6: According to the characteristics of the ring width data in the curve graph drawn in Step 5, determine the type of error that plays a dominant role in the lens of the X-ray focusing mirror;

[0015] Step 7: According to the type of error that plays a dominant role determined in Step 6, analyze and calculate the defocused spot image, and determine the position where the error appears in the lens of the X-ray focusing mirror based on the results.

[0016] Further, Step 6 is specifically as follows:

[0017] 6.1 If the ring width data in the curve graph drawn in Step 5 is continuously changing gradually, it is determined that the attitude error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data;

[0018] 6.2 If the ring width data in the curve graph drawn in Step 5 basically remains unchanged, it is determined that the intrinsic surface shape error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data;

[0019] In the present invention, the implementation of Step 6.1 and Step 6.2 has no sequence.

[0020] Further, Step 7 is specifically as follows:

[0021] 7.1 If it is determined in Step 6 that the attitude error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data, then analyze the off-axis direction of the lens of the X-ray focusing mirror during the alignment process according to the ring width data, and correspond the azimuth angle corresponding to the maximum ring width to the off-axis direction of the lens of the X-ray focusing mirror, and further determine the off-axis position of the lens of the X-ray focusing mirror;

[0022] 7.2 If it is determined in Step 6 that the intrinsic surface shape error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data, then determine the position of the change in the intrinsic surface shape of the lens of the X-ray focusing mirror according to the position of the sudden change in the radius in the defocused spot image;

[0023] In the present invention, the implementation of Step 7.1 and Step 7.2 has no sequence.

[0024] Further, in step 4, the number of different azimuth angles is not less than 6.

[0025] Further, in step 4, with the center point of the defocused spot image as the reference point, the defocused spot image is evenly divided at different azimuth angles.

[0026] Further, in step 1, a visible light system or an X-ray system is used to obtain a defocused spot image of the X-ray focusing mirror at the defocused position.

[0027] Further, in step 3, the defocused spot image is processed by using the Hough algorithm.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0029] 1. A method for detecting lens errors of an X-ray focusing mirror provided by the present invention is based on the continuity of defocused spot ring width data, and can simply and effectively determine the attitude and surface error of the X-ray focusing mirror during the alignment process, and determine the position where the attitude and surface error occur. This method has never been used in previous X-ray optical systems and is applicable to the alignment angle and the determination of the intrinsic surface error of a large obscuration ratio optical system.

[0030] 2. In a method for detecting lens errors of an X-ray focusing mirror provided by the present invention, a visible light system or an X-ray system is used to measure the defocused focal spot position of the X-ray focusing mirror, and the measurement result is more accurate; the defocused spot image is processed by using the Hough algorithm, and the center and radius of the defocused spot image can be directly and accurately determined, so that the detection of the lens is more accurate. Description of the Drawings

[0031] Figure 1 It is a defocused spot image of an X-ray focusing mirror detected by the present invention due to the lens attitude reason;

[0032] Figure 2 It is a defocused spot image of an X-ray focusing mirror detected by the present invention due to the lens surface error reason;

[0033] Figure 3 It is a statistical distribution diagram of the defocused spot ring width change of the X-ray focusing mirror in the embodiment of the present invention;

[0034] Explanation of the reference numerals in the drawings is as follows:

[0035] 11 - The 0° azimuth angle direction of the ring width change caused by the lens attitude reason, 12 - The 90° azimuth angle direction of the ring width change caused by the lens attitude reason, 13 - The ring width distribution curve on the transverse tangent of the defocused spot of the X-ray focusing mirror;

[0036] 21 - The 0° azimuth direction of the ring width change caused by the mirror surface shape, 22 - The 90° azimuth direction of the ring width change caused by the mirror surface shape, 23 - The ring width distribution curve on the transverse tangent of the defocused spot of the X-ray focusing mirror, 24 - The position where the ring radius has a sudden change due to the mirror surface shape;

[0037] 31 - The change curve of the defocused spot ring width from 0° to 360° due to the lens attitude, 32 - The change curve of the defocused spot ring width from 0° to 360° due to the mirror surface shape. Specific implementation mode

[0038] To make the objectives, advantages and features of the present invention clearer, the following further details a method for detecting lens errors of an X-ray focusing mirror proposed by the present invention in conjunction with the accompanying drawings and specific embodiments.

[0039] Embodiment 1

[0040] A method for detecting lens errors of an X-ray focusing mirror includes the following steps:

[0041] Step 1, measure the focal spot of the X-ray focusing mirror, determine the focal point position of the X-ray focusing mirror, and use a visible light system or an X-ray system to obtain a circular defocused spot image of the X-ray focusing mirror as shown in Figure 1 at the defocused position.

[0042] If the measured defocused spot image of the X-ray focusing mirror is not in the form of a ring, such as there are breakpoints in the image, then the alignment error of the X-ray focusing mirror is large, and it is returned for re-alignment.

[0043] Step 2, use the Hough algorithm to process the defocused spot image and find the center point O of the defocused spot image.

[0044] Step 3, taking the center point of the defocused spot image as the reference point, evenly divide the defocused spot image at an azimuth angle interval of 45°, and test and record the ring width of the defocused spot image at different azimuth angle positions.

[0045] As shown in Figure 1 , determine that the parallel direction is the 0° azimuth direction 11 of the ring width change, and the counterclockwise rotation of 90° direction is the 90° azimuth direction 12 of the ring width change, and divide the defocused spot image in turn at an azimuth angle interval of 45°. From the ring width distribution curve 13 on the transverse tangent of the defocused spot of the X-ray focusing mirror, it is obtained that the 0° / 180° direction of the defocused spot image has a ring width only at the ring, and the ring width in the 0° direction is less than that in the 180° direction.

[0046] Step 4: Based on the ring width data at different azimuth positions, conduct data statistics on the ring width of the defocused spot of the X-ray focusing mirror, and plot a curve graph showing the variation of the ring width of the defocused spot image with the azimuth angle, as Figure 3 shown by curve 31 in

[0047] The variation curve of the ring width of the defocused spot from the 0° direction to the 360° direction due to the lens attitude is a continuous variation curve, showing a trend of first increasing and then decreasing.

[0048] Step 5: Obtained from the variation curve 31 of the ring width of the defocused spot from the 0° direction to the 360° direction caused by the lens attitude, the ring width data is continuously and gradually changing. Therefore, there is an attitude error in the lens of the X-ray focusing mirror and it plays a dominant role in the change of the ring width data.

[0049] Embodiment 2

[0050] A method for detecting lens errors of an X-ray focusing mirror includes the following steps:

[0051] Step 1: Measure the focal spot of the X-ray focusing mirror, determine the focal point position of the X-ray focusing mirror, and obtain a circular defocused spot image of the X-ray focusing mirror in the form of a ring as shown in Figure 2 at the defocused position using a visible light system or an X-ray system.

[0052] Step 2: Use the Hough algorithm to process the defocused spot image and find the center point O of the defocused spot image.

[0053] Step 3: Uniformly divide the defocused spot image along the center point O of the defocused spot image at an azimuth angle interval of 45°, and test and record the ring width at different azimuth positions of the defocused spot image.

[0054] As shown in Figure 2 , determine that the parallel direction is the 0° azimuth angle direction 21 of the ring width change, the counterclockwise rotation of 90° direction is the 90° azimuth angle direction 22 of the ring width change, divide the defocused spot image at an azimuth angle interval of 45° in sequence, and obtain the ring width distribution curve 23 on the transverse tangent of the defocused spot of the X-ray focusing mirror.

[0055] Step 4: Based on the ring width data at different azimuth angles, perform data statistics on the defocus spot ring width of the X-ray focusing mirror, and draw a curve graph showing the change of the defocus spot image ring width with the azimuth angle position. As shown by curve 32 in Figure 3 , the ring width of the defocus spot does not change significantly from the 0° direction to the 360° direction.

[0056] Step 5: It can be obtained from curve 32 in Figure 3 that the ring width data basically remains unchanged. Therefore, the lens of the X-ray focusing mirror has a surface shape error and plays a dominant role in the change of the ring width data.

[0057] Step 6: Analyze the ring width data. The ring width of the defocus spot does not change significantly in each azimuth angle direction. However, it can be found from Figure 2 that there is a sudden change in the radius of the defocus spot image in the circumferential direction. The position 24 where the radius of the ring has a sudden change due to the surface shape of the lens corresponds to the position of the intrinsic surface shape error of the lens. Calculate the angular resolution of the X-ray focusing mirror lens, and screen the lens according to the index requirements of the X-ray focusing mirror.

[0058] In the above two embodiments, the defocus spot images of the X-ray focusing mirror obtained in Step 1 are all in the form of a ring. If the defocus spot image is not in the form of a ring, the X-ray focusing mirror needs to be reinstalled and adjusted.

[0059] The lens error detection method provided by the present invention is based on the characteristics of the defocus spot ring width data, and can simply and effectively distinguish the attitude and surface shape error of the X-ray focusing mirror during the installation and adjustment process, and determine the positions where the attitude and surface shape errors occur. It has never been used in previous X-ray optical systems, and is applicable to the determination of the installation angle and the intrinsic surface shape error of a large-obscuration-ratio optical system.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A method for detecting lens errors of an X-ray focusing mirror, characterized in that, it includes the following steps: Step 1, measure the focal spot of the X-ray focusing mirror, determine the focal point position of the X-ray focusing mirror, and obtain the defocused spot image of the X-ray focusing mirror at the defocused position; Step 2, if the defocused spot image of the measured X-ray focusing mirror is not in the form of a ring, the alignment error of the X-ray focusing mirror is large, and return to re-align; if the defocused spot image of the measured X-ray focusing mirror is in the form of a ring, proceed to Step 3; Step 3, process the defocused spot image to find the center point of the defocused spot image; Step 4, taking the center point of the defocused spot image as the reference point, divide the defocused spot image at different azimuth angles, and test and record the ring widths of the defocused spot image at different azimuth angle positions; Step 5, based on the ring width data at different azimuth angle positions, draw a curve graph of the ring width of the defocused spot image changing with the azimuth angle position; Step 6, according to the characteristics of the ring width data in the curve graph drawn in Step 5, determine the type of error that plays a dominant role in the lens of the X-ray focusing mirror; Step 7, according to the type of error that plays a dominant role determined in Step 6, analyze and calculate the defocused spot image, and determine the position where the error appears in the lens of the X-ray focusing mirror according to the result.

2. The method for detecting lens errors of an X-ray focusing mirror according to claim 1, characterized in that, the specific content of Step 6 is: 6.1 If the ring width data in the curve graph drawn in Step 5 is continuously changing, it is determined that the attitude error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data; 6.2 If the ring width data in the curve graph drawn in Step 5 remains basically unchanged, it is determined that the intrinsic surface error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data.

3. The method for detecting lens errors of an X-ray focusing mirror according to claim 2, characterized in that, the specific content of Step 7 is: 7.1 If it is determined in Step 6 that the attitude error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data, then analyze the off-axis direction of the lens of the X-ray focusing mirror during the alignment process according to the ring width data, and correspond to the off-axis direction of the lens of the X-ray focusing mirror by the azimuth angle corresponding to the maximum ring width, and then determine the off-axis position of the lens of the X-ray focusing mirror; 7.2 If it is determined in Step 6 that the intrinsic surface error of the lens of the X-ray focusing mirror plays a dominant role in the change of the ring width data, then determine the position of the change of the intrinsic surface of the lens of the X-ray focusing mirror according to the position of the sudden change of the radius in the defocused spot image.

4. The method for detecting lens errors of an X-ray focusing mirror according to claim 3, characterized in that: In Step 4, the number of different azimuth angles is not less than 6.

5. The method for detecting lens errors of an X-ray focusing mirror according to claim 4, characterized in that: In Step 4, taking the center point of the defocused spot image as the reference point, the defocused spot image is evenly divided at different azimuth angles.

6. The method for detecting lens errors of an X-ray focusing mirror according to claim 5, characterized in that: In the step 1, an out-of-focus spot image of the X-ray focusing mirror is obtained at an out-of-focus position by using a visible light system or an X-ray system.

7. The lens error detection method for an X-ray focusing mirror according to claim 6, characterized in that: in the step 3, the out-of-focus spot image is processed by using a Hough algorithm.

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