Aberration control method for reflective two-beam interference exposure system

Abstract

An aberration regulation method of a reflective double-beam interference exposure system, comprising: constructing a reflective double-beam interference exposure system, dividing a light beam output by a laser into two double beams with the same intensity, and forming an interference exposure field; constructing an aberration regulation system, testing and recording the aberration of the double-beam light path by using a spherical interferometer, and regulating the wavefront of any light beam in the double beam by using a deformable mirror, so that the aberration of the light beam matches the aberration of the other light beam, and the regulation of the aberration of the interference exposure field is completed. The present application solves the problems of precise assembly and adjustment, wavefront aberration control and the like of the reflective double-beam interference exposure system based on a large-aperture off-axis parabolic mirror, and provides a new solution for the preparation of a meter-level large-aperture, low-aberration diffraction grating.

Description

Technical Field

[0001] This invention relates to the field of large-aperture diffraction grating fabrication, specifically to the assembly and adjustment of a two-beam interference exposure system based on an off-axis parabolic mirror. Background Technology

[0002] Meter-scale large-aperture, high-quality diffraction gratings are core components of systems such as petawatt ultra-intense and ultrashort laser devices, high-energy spectral combined laser weapons, and high-precision displacement measurement gratings. Currently, the fabrication techniques for meter-scale large-aperture diffraction gratings mainly include two techniques: transmission-type dual-beam static interference single-exposure and fine-beam dynamic scanning interference exposure. In the transmission-type dual-beam static interference single-exposure technique, the ultraviolet laser beam emitted by the laser is split into two beams, which are collimated and expanded by lenses and then interfere within the photoresist on the grating substrate surface, forming a latent image of the photoresist grating. Subsequently, wet development and etching processes are used to fabricate the diffraction grating element. In the fine-beam dynamic scanning interference exposure technique, interference fringes formed by two fine beams with an aperture of only about 1 mm are used to scan and expose the photoresist on the grating substrate surface, stitching them together to create a large-area grating. Because the transmission-type collimating optical system has a good transmission wavefront and a large field of view, the diffraction grating fabricated using this method has a good diffraction wavefront, and the high-quality exposure optical path is relatively easy to assemble and adjust. However, limited by the high-quality lens materials and the size of the long-stroke, nanometer-level positioning precision stage, the maximum aperture of diffraction gratings manufactured using transmission interferometric exposure technology is only about 1 meter. In recent years, with the continuous increase in laser output power demands, the need for high-quality diffraction gratings with apertures larger than meters has become increasingly urgent. Since high-quality mirror materials are easier to use for large apertures, two-beam interferometric exposure technology based on off-axis parabolic mirrors has become the preferred solution for fabricating large-aperture diffraction gratings on the order of meters. However, the disadvantages of the reflective exposure system are the smaller field of view of the off-axis parabolic mirror, and the greater aberrations and greater difficulty in assembly compared to lenses under the same optical processing conditions. This results in poor wavefront quality of large-aperture gratings fabricated using the reflective two-beam interferometric exposure system, affecting their application in high-power laser systems.

[0003] Therefore, researching and solving the problems of aberration control and precision assembly in large-aperture reflective double-beam interferometric exposure systems is of great significance for promoting the application of reflective interferometric exposure technology in the manufacturing of large-aperture diffraction gratings at the meter level and above, and for breaking the passive situation in which my country is dependent on others for high-quality, large-aperture gratings. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of reflective exposure technology in terms of aberrations and assembly, and to provide an aberration control method for a reflective dual-beam interferometric exposure system based on a spherical interferometer, a deformable mirror, a standard plane mirror, and an autocollimation detection method, thereby improving the wavefront quality of large-aperture diffraction gratings manufactured based on reflective exposure technology.

[0005] The technical solution of the present invention is as follows:

[0006] A method for aberration control in a reflective two-beam interferometric exposure system includes:

[0007] A reflective dual-beam interferometric exposure system is constructed to split the laser beam into two beams of equal intensity, forming an interferometric exposure field.

[0008] An aberration control system was constructed. A spherical interferometer was used to test and record the aberrations of the two-beam optical paths. A deformable mirror was used to control the wavefront of one of the two beams so that it matched the aberration of the other beam, thus completing the control of the aberrations in the interferometric exposure field.

[0009] A method for aberration control in a reflective two-beam interferometric exposure system, specifically including:

[0010] Step 1) Left optical path adjustment and wavefront testing for reflective double-beam interferometry exposure:

[0011] Step 1.1) Based on the grating period Λ to be prepared and the laser wavelength λ, calculate the double beam angle 2θ using the formula sin(θ)=λ / 2 / Λ. Combined with the focal length, aperture and other parameters of the off-axis parabolic mirror, determine the approximate position of the left and right optical path off-axis parabolic mirrors and the interference overlap of the two optical paths, and complete the preliminary construction of the double beam interference exposure optical path.

[0012] Step 1.2) Place the plane mirror at the position where the two light interferences overlap, place the spherical interferometer in the left light path and adjust its distance from the off-axis parabolic mirror in the left light path so that it is located near the focal point of the off-axis parabolic mirror;

[0013] Step 1.3) Turn on the spherical interferometer, remove the focusing objective lens at its front end, and let the parallel thin beam emitted from the spherical interferometer be incident on the center of the off-axis parabolic mirror in the left optical path. After reflection, it is incident on the center of the standard plane mirror placed at the interference exposure position. Adjust the standard plane mirror so that the reflected light returns along the original path to enter the spherical interferometer, thus forming a self-collimating optical path.

[0014] Step 1.4) Reinstall the focusing objective lens at the front end of the spherical interferometer, and repeatedly adjust the spatial relative positions of the standard plane mirror, the left optical path off-axis parabolic mirror, and the spherical interferometer to minimize the wavefront aberration of the returned light measured by the spherical interferometer;

[0015] Step 1.5) Fix the spherical interferometer, the off-axis parabolic mirror for the left optical path, and the standard plane mirror. Install the spatial filter pinhole for the left optical path near the focal point of the spherical interferometer. Adjust the spatial position of the spatial filter pinhole to allow the point light source emitted by the spherical interferometer to pass through unobstructed. Then fix the position of the spatial filter pinhole for the left optical path and simultaneously record the wavefront distribution φ of the returned light measured by the spherical interferometer. l (x,y);

[0016] Step 1.6) Remove the spherical interferometer, turn on the ultraviolet laser for exposure, adjust each mirror in the left optical path so that the reflected light is incident on the center of the spatial filter pinhole in the left optical path, install the focusing objective lens in the left optical path, and continuously fine-tune the mirrors and focusing objective lens in the left optical path so that the focused beam passes completely through the spatial filter pinhole in the left optical path. This completes the adjustment of the left optical path.

[0017] Step 2) Right optical path adjustment and wavefront control in reflective double-beam interferometry exposure:

[0018] Step 2.1) Rotate the standard plane mirror counterclockwise by 2θ angles so that it faces the right optical path off-axis parabolic mirror, and then fix the position of the standard plane mirror in place;

[0019] Step 2.2) Install the deformable mirror and the spherical interferometer in sequence, and initialize the mirror position of the deformable mirror;

[0020] Step 2.3) Open the spherical interferometer, remove the focusing objective lens at its front end, and continuously adjust the spatial positions of the right optical path off-axis parabolic mirror, deformable mirror, and spherical interferometer so that the parallel thin laser beam emitted by the spherical interferometer returns to the spherical interferometer along the self-collimating optical path.

[0021] Step 2.4) Reinstall the focusing objective lens at the front end of the spherical interferometer, and repeatedly adjust the spatial relative positions of the right optical path off-axis parabolic mirror, deformable mirror, and spherical interferometer to minimize the wavefront aberration of the returned light measured by the spherical interferometer.

[0022] Step 2.5) Insert the right optical path spatial filter pinhole near the point light source emitted by the spherical interferometer, adjust the position of the right optical path spatial filter pinhole so that the point light source emitted by the interferometer can pass through without obstruction, and fix the position of the spatial filter pinhole unchanged.

[0023] Step 2.6) Adjust the mirror deformation function h(x,y) of the deformable mirror to make the wavefront distribution φ of the right-path return light measured by the spherical interferometer... r (x,y) and the wavefront distribution function φ of the left optical path l The distribution of (x,y) in space should be as uniform as possible, i.e., min(φ) r(x,y)-φ l Meanwhile, the mirror deformation function h(x,y) of the deformable mirror is recorded.

[0024] Step 2.7) Remove the spherical interferometer, adjust each reflector in the right optical path so that the reflected light is incident on the center of the right optical path spatial filter pinhole, install the right optical path focusing objective, and continuously fine-tune the right optical path reflector and the right optical path focusing objective until the focused beam passes completely through the right optical path spatial filter pinhole. This completes the adjustment of the right optical path.

[0025] Compared with the prior art, the present invention has the following beneficial technical effects:

[0026] 1. By employing a spherical interferometer in conjunction with a large-aperture standard plane mirror, the assembly and adjustment efficiency and accuracy of the dual-beam interferometric exposure system based on a large-aperture off-axis parabolic mirror are greatly improved.

[0027] 2. By using deformable mirrors to match the single-path reflected wavefront, aberration correction of the dual-beam interference exposure field was achieved, laying the foundation for the fabrication of large-aperture, low-aberration diffraction gratings.

[0028] 3. It is applicable to any technical solution that uses two-beam interference exposure technology to prepare low-aberration diffraction gratings, and has strong versatility. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of an embodiment of an aberration control device for a reflective dual-beam interferometric exposure system according to the present invention.

[0030] In the diagram: 1-Continuous ultraviolet laser, 2-First half-wave plate, 3-Polarizing beam splitter prism, 4-First reflecting mirror, 5-Second half-wave plate, 6-Spherical interferometer, 7-Computer, 8-Second reflecting mirror, 9-First focusing objective lens, 10-First spatial filter, 11-Deformable reflecting mirror, 12-Right optical path off-axis parabolic reflecting mirror, 13-Standard plane reflecting mirror, 14-Left optical path off-axis parabolic reflecting mirror, 15-Second spatial filter, 16-Second focusing objective lens, 17-Third reflecting mirror, 18-Fourth reflecting mirror, 19-Parallel beam, 20-Parallel beam

[0031] Figure 2 This is a schematic diagram of the self-collimating optical path for testing wavefront aberrations using a spherical interferometer in an embodiment of an aberration control device for a reflective dual-beam interferometric exposure system according to the present invention.

[0032] In the diagram: 21 - Spherical beam emitted by the spherical interferometer; 22 - Collimated parallel beam. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments and accompanying drawings, but this should not be construed as limiting the scope of protection of the present invention.

[0034] An aberration control device for a reflective two-beam interferometric exposure system includes: a spherical interferometer for assembling, adjusting, testing, and recording aberrations in the reflective interferometric exposure system; a spatial filter for locating the position of the ideal point light source generated by the spherical interferometer and spatially filtering it; a deformable mirror for controlling one wavefront aberration of the two-beam interferometric exposure system to match the wavefront aberration of the other light, thereby reducing the grating diffraction wavefront aberration formed after interference; and a standard plane mirror for reflecting the laser beam emitted from the interferometric exposure system back along its original path, and together with the spherical interferometer, forming a wavefront aberration self-collimation measurement optical path to realize the measurement of optical path aberrations.

[0035] Figure 1 This is a schematic diagram of an embodiment of an aberration control device for a reflective two-beam interferometric exposure system according to the present invention. As shown in the figure, the aberration control device for a reflective two-beam interferometric exposure system includes: a spherical interferometer for generating an ideal point light source to adjust and record aberrations in a reflective interferometric exposure system based on an off-axis parabolic mirror; a spatial filter for locating the position of the ideal point light source generated by the spherical interferometer and spatially filtering it; a deformable mirror for controlling one of the wavefront aberrations of the two-beam interferometric exposure system to make it as similar as possible to the wavefront aberration of the other light, thereby reducing the grating diffraction wavefront aberration formed after interference; and a standard plane mirror for reflecting the laser beam emitted from the interferometric exposure system back along its original path, and together with the spherical interferometer, forming a wavefront aberration self-collimation measurement optical path to realize the measurement of optical path aberrations. The reflective two-beam interferometric exposure system splits a laser beam from a continuous ultraviolet laser source into two beams with the same intensity distribution, and converges the two beams to form an interferometric exposure field.

[0036] A continuous ultraviolet laser source is used in this embodiment to output an ultraviolet laser beam from a continuous ultraviolet laser 1;

[0037] A reflective dual-beam interferometric exposure system splits a laser beam from a continuous ultraviolet laser into two beams 19 and 20 of equal intensity, forming an interference exposure field. In this embodiment, it includes: a first half-wave plate 2, a polarizing beam-splitting prism 3, a first reflecting mirror 4, a second half-wave plate 5, a second reflecting mirror 8, a first focusing objective lens 9, a first spatial filter 10, a right-path off-axis parabolic reflector 12, a left-path off-axis parabolic reflector 14, a second spatial filter 15, a second focusing objective lens 16, a third reflecting mirror 17, and a fourth reflecting mirror 18. The ultraviolet laser beam output from the continuous ultraviolet laser 1 is transmitted through the first half-wave plate 2, then split by the polarizing beam-splitting prism 3. By rotating and adjusting the first half-wave plate 2 and the second half-wave plate 5, the intensity of the two beams is made equal. After passing through the reflecting mirror, focusing objective lens, spatial filter, and off-axis parabolic reflector respectively, they form an interference exposure field.

[0038] The aberration control system employs a spherical interferometer to assemble and adjust the reflective two-beam interferometric exposure system, and to test and record its aberrations. A deformable mirror is used to modulate the wavefront of one beam to match the aberration of the other beam. This embodiment includes: a spherical interferometer 6, a computer 7, a deformable mirror 11, and a standard plane mirror 13. The spherical interferometer 6 and the deformable mirror 11 are connected to the computer 7. The computer 7 controls the deformation of the deformable mirror 11, thereby modulating the reflected wavefront to match the wavefront of the other beam in the two-beam interferometric exposure system, thus completing the control of aberrations in the interferometric exposure field.

[0039] A method for aberration control in a reflective two-beam interferometric exposure system includes two stages: left optical path adjustment and wavefront testing, and right optical path adjustment and wavefront manipulation.

[0040] The left optical path adjustment and wavefront testing stage of the dual-beam interferometry exposure system specifically includes the following steps:

[0041] ① Based on the grating period Λ to be prepared and the output wavelength λ of the continuous ultraviolet laser 1, the double beam angle 2θ is calculated using the formula sin(θ)=λ / 2 / Λ. Combined with the focal length, aperture and other parameters of the off-axis parabolic mirror, the approximate positions of the right optical path off-axis parabolic mirror 12, the left optical path off-axis parabolic mirror 14, the standard plane mirror 13 and other components are determined, and the preliminary construction of the reflective double beam interferometric exposure system is completed.

[0042] ② Place the spherical interferometer 6 into the left optical path, remove the second spatial filter 15 and the second focusing objective lens 16, and adjust the position of the spherical interferometer 6 so that it is near the focal point of the off-axis parabolic mirror 14;

[0043] ③ Open the spherical interferometer 6, remove the focusing objective lens at its front end, and let the parallel fine beam emitted from the spherical interferometer 6 be incident on the center of the off-axis parabolic reflector 14 in the left optical path. After reflection, it is incident on the center of the standard plane reflector 13 placed at the interference exposure position. Adjust the standard plane reflector 13 so that the reflected light returns along the original path to enter the spherical interferometer 6, thus forming a self-collimating optical path.

[0044] ④ Reinstall the focusing objective lens at the front end of the spherical interferometer 6, and repeatedly adjust the spatial relative positions of the standard plane mirror 13, the left optical path off-axis parabolic mirror 14, and the spherical interferometer 6 to minimize the wavefront aberration of the returned light measured by the spherical interferometer 6.

[0045] ⑤ Fix the spherical interferometer 6, the left optical path off-axis parabolic mirror 14, and the standard plane mirror 13. Install the second spatial filter 15 near the focal point of the spherical interferometer 6. Adjust the spatial position of the second spatial filter 15 so that the point light source emitted by the spherical interferometer 6 can pass through without obstruction. Then fix the position of the second spatial filter 15 and simultaneously record the wavefront distribution φ of the returned light measured by the spherical interferometer 6. l (x,y);

[0046] ⑥ Remove the spherical interferometer 6, turn on the continuous ultraviolet laser 1, adjust the third reflector 17 and the fourth reflector 18 of the left optical path so that the reflected light is transmitted through the second spatial filter 15, install the second focusing objective lens 16, and continuously fine-tune the spatial positions of the third reflector 17, the fourth reflector 18 and the second focusing objective lens 16 of the left optical path so that the focused beam completely passes through the second spatial filter 15. This completes the adjustment of the left optical path and the wavefront test of the left beam 19.

[0047] Step 2) Right optical path adjustment and wavefront control in reflective double-beam interferometry exposure:

[0048] ① Rotate the standard plane mirror 13 counterclockwise by 2θ angle so that it faces the right optical path off-axis parabolic mirror 12, and then fix the position of the standard plane mirror 13.

[0049] ② Install the deformable mirror 11 and the spherical interferometer 6 in sequence, and connect them to the computer 7. The computer 7 is used to initialize the mirror position of the deformable mirror.

[0050] ③ Open the spherical interferometer 6, remove the focusing objective lens at its front end, remove the second reflecting mirror 8, the first focusing objective lens 9, and the first spatial filter 10, and continuously adjust the spatial position of the right optical path off-axis parabolic reflecting mirror 12, deformable reflecting mirror 11, and spherical interferometer 6 so that the parallel thin laser beam emitted by the spherical interferometer 6 returns to the spherical interferometer 6 along the self-collimating optical path;

[0051] ④ Reinstall the focusing objective lens at the front end of the spherical interferometer 6, and repeatedly adjust the spatial relative positions of the right optical path off-axis parabolic mirror 12, deformable mirror 11 and spherical interferometer 6 to minimize the wavefront aberration of the returned light measured by the spherical interferometer 6.

[0052] ⑤ Insert the first spatial filter 10 near the point light source emitted by the spherical interferometer 6, adjust the position of the first spatial filter 10 so that the point light source emitted by the spherical interferometer 6 can pass through without obstruction, and fix the position of the first spatial filter 10 unchanged.

[0053] ⑥ Adjust the mirror deformation function h(x,y) of the deformable mirror 11 to make the wavefront distribution φ of the right optical path return light 20 measured by the spherical interferometer 6 more uniform. r (x,y) and the wavefront distribution function φ of the left optical path l The distribution of (x,y) in space should be as uniform as possible, i.e., min(φ) r (x,y)-φ l Meanwhile, the mirror deformation function h(x,y) of the deformable mirror is recorded.

[0054] ⑦ Remove the spherical interferometer 6, install the second reflecting mirror 8, and adjust the spatial position of the second reflecting mirror 8 so that the ultraviolet laser output from the continuous ultraviolet laser passes through the first spatial filter 10; install the first focusing objective lens 9, and continuously fine-tune the spatial positions of the second reflecting mirror 8 and the first focusing objective lens 9 so that the focused beam completely passes through the first spatial filter 10. This completes the adjustment of the right optical path and the control of the wavefront. After this part of the adjustment, the laser beam can be... Figure 2 The distorted beam 21 shown is adjusted to a more ideal beam 22.

Claims

1. A method for aberration control in a reflective two-beam interferometric exposure system, characterized in that, include: A reflective double-beam interferometric exposure system is constructed to split the laser beam output by the laser into two beams of equal intensity, forming an interference exposure field. Specifically, this includes placing a first half-wave plate (2) and a polarizing beam splitter (3) along the transmission direction of the ultraviolet laser beam output by the continuous ultraviolet laser (1). After the ultraviolet laser beam is transmitted through the first half-wave plate (2), it is split into two beams, namely a transmitted beam and a reflected beam, by the polarizing beam splitter (3). A first reflecting mirror (4), a second half-wave plate (5), a second reflecting mirror (8), and a first focusing objective lens (9) are placed sequentially along the transmission direction of the transmitted beam. The first spatial filter (10) and the right optical path off-axis parabolic reflector (12) are arranged in sequence along the transmission direction of the reflected beam. The fourth reflector (18), the third reflector (17), the second focusing objective (16), the second spatial filter (15) and the left optical path off-axis parabolic reflector (14) are arranged in sequence. The first half-wave plate (2) and the second half-wave plate (5) are rotated and adjusted so that the intensity of the two beams is the same. After passing through their respective reflectors, focusing objective, spatial filter and off-axis parabolic reflector, they converge at the standard plane reflector (13) to form an interference exposure field. An aberration control system was constructed. A spherical interferometer was used to test and record the aberrations of the two-beam optical paths. A deformable mirror was used to control the wavefront of either beam in the two beams, matching its aberration with that of the other beam. This completed the control of aberrations in the interferometric exposure field. Specifically: Step 1) Left optical path adjustment and wavefront testing for reflective double-beam interferometry exposure: Step 1.1) Calculate the angle 2θ between the two incident beams and the convergence point of the standard plane mirror (13), using the following formula: sin(θ) = λ / 2 / Λ In the formula, Λ is the period of the grating to be prepared, and λ is the wavelength of the ultraviolet laser beam output by the continuous ultraviolet laser. Step 1.2) Place the standard plane mirror (13) at the position where the two beams overlap, and place the spherical interferometer (6) in the optical path of the reflected beam, and place it at the focal point of the off-axis parabolic mirror (14) in the left optical path. The spherical interferometer (6) is connected to the computer (7). Step 1.3) Remove the second focusing objective (16) and the second spatial filter (15), turn on the spherical interferometer (6), remove the focusing objective at its front end, so that the parallel fine beam emitted from the spherical interferometer is incident on the center of the left optical path off-axis parabolic mirror (14), and after being reflected by the left optical path off-axis parabolic mirror (14), it is incident on the center of the standard plane mirror (13) placed at the interference exposure position. Adjust the standard plane mirror (13) so that the reflected light returns along the original path and enters the spherical interferometer (6), thus forming a self-collimating optical path; Step 1.4) Install the focusing objective lens at the front end of the spherical interferometer (6), and repeatedly adjust the spatial relative positions of the standard plane mirror (13), the left optical path off-axis parabolic mirror (14), and the spherical interferometer (6) to minimize the wavefront aberration of the returned light measured by the spherical interferometer; Step 1.5) Fix the spherical interferometer (6), the left optical path off-axis parabolic mirror (14), and the standard plane mirror (13). Install the second spatial filter 15 at the focal point of the spherical interferometer (6). Adjust the spatial position of the second spatial filter (15) so that the point light source emitted by the spherical interferometer (6) can pass through the second spatial filter (15) without obstruction. Fix the second spatial filter (15) and use a computer to record the current wavefront distribution φ of the returned light measured by the spherical interferometer. l (x,y); Step 1.6) Remove the spherical interferometer (6), turn on the continuous ultraviolet laser, adjust the fourth mirror (18) and the third mirror (17) so that the reflected light is incident on the center position of the second spatial filter (15), install the second focusing objective (16), and continuously fine-tune the fourth mirror (18), the third mirror (17) and the second focusing objective (16) so that the focused beam passes completely through the second spatial filter (15). Thus, the adjustment of the left optical path and the wavefront aberration test of the left beam (19) are completed. Step 2) Right optical path adjustment and wavefront control in reflective double-beam interferometry exposure: Step 2.1) Rotate the standard plane mirror (13) counterclockwise by 2θ degrees so that it faces the right optical path off-axis parabolic mirror (12), and fix the standard plane mirror (13). Step 2.2) Remove the second mirror (8), the first focusing lens (9), and the first spatial filter (10), and install the deformable mirror (11) and the spherical interferometer (6). The deformable mirror (11) and the spherical interferometer (6) are connected to the computer (7) respectively, and the mirror position of the deformable mirror (11) is initialized by the computer (7). Step 2.3) Open the spherical interferometer (6), remove the focusing objective lens at its front end, and adjust the spatial positions of the right optical path off-axis parabolic reflector (12), deformable reflector (11) and spherical interferometer (6) so that the parallel thin laser beam emitted by the spherical interferometer (6) returns to the spherical interferometer (6) along the self-collimating optical path. Step 2.4) Reinstall the focusing objective lens at the front end of the spherical interferometer (6), and repeatedly adjust the spatial relative positions of the right optical path off-axis parabolic mirror (12), deformable mirror (11) and spherical interferometer (6) to minimize the wavefront aberration of the returned light measured by the spherical interferometer (6); Step 2.5) Insert the first spatial filter (10) near the point light source emitted by the spherical interferometer (6), adjust the position of the first spatial filter (10) so that the point light source emitted by the spherical interferometer (6) can pass through without obstruction, and fix the position of the right optical path spatial filter (10) unchanged. Step 2.6) Adjust the mirror deformation function h(x,y) of the deformable mirror (11) so that the wavefront distribution φ of the right optical path return beam (20) measured by the spherical interferometer (6) is equal to that of the right optical path return beam (20). r The wavefront distribution function φ of (x,y) and the left optical path beam (19) l The distribution of (x, y) in space should be as similar as possible, i.e., min(φ) r (x,y)-φ l (x,y)), and at the same time record the mirror deformation function h(x,y) of the deformable mirror (11); Step 2.7) Remove the spherical interferometer (6), install the second reflector (8), so that the reflected continuous ultraviolet laser beam is incident on the center position of the first spatial filter 10, install the first focusing objective (9), and finely adjust the spatial position of the second reflector (8) and the first focusing objective (9) so that the focused beam passes completely through the pinhole of the first spatial filter. The adjustment of the right optical path is thus completed.

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