Common reference interferometric measurement method for back-to-back aspheric mirrors

Abstract

The application discloses a kind of back-to-back aspheric mirror's common reference interferometric measurement method, this measurement method uses first CGH compensator to measure back-to-back first aspheric mirror, second CGH compensator measures back-to-back second aspheric mirror, both use same laser spherical wave interferometer, first CGH compensator contains from outside to inside auxiliary alignment hologram, test main hologram, attitude alignment hologram and hologram-free transmission area, auxiliary alignment hologram is used for first CGH compensator alignment interferometer, second CGH compensator contains from outside to inside test main hologram, hologram-free reflection area and auxiliary alignment hologram, auxiliary alignment hologram is used for second CGH compensator alignment interferometer and first CGH compensator.The measurement method of the application has the advantages of common reference measurement back-to-back aspheric mirror's surface error, the surface error of two mirrors and its relative position error can be obtained simultaneously.

Description

Technical Field

[0001] This invention relates to optical surface interferometry technology and measurement technology required for the assembly and adjustment of two mirrors, specifically to a common reference interferometry method for back-to-back aspherical mirrors. Background Technology

[0002] Aspherical mirrors, due to their greater design freedom, have been widely used in modern imaging optical systems, offering advantages such as more compact structure and better image quality compared to traditional spherical systems. Optical imaging systems have evolved from two-mirror structures like the Cassegrain and RC systems to three-mirror astigmatism correction (TMA) and even four-mirror systems, resulting in increasingly higher image quality. However, systems consisting of three or more aspherical mirrors are extremely difficult to assemble and adjust because any two of them cannot produce perfect images, and they cannot be assembled and adjusted separately in pairs. Assembling and adjusting all three mirrors together presents problems of numerous degrees of freedom and strong coupling between them.

[0003] Aspherical surfaces are curved surfaces that deviate from a sphere. Compensators are typically designed to compensate for this deviation, allowing for interferometric measurements of surface shape errors using a laser spherical wave interferometer. Common aspherical compensators include spherical lens groups or computational holographic compensators (CGH). However, regardless of the type of compensator, for two back-to-back aspherical mirrors, only the surface shape error of a single mirror can be measured; the relative positional error between the two mirrors cannot be determined. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a common reference interferometry method for back-to-back aspherical mirrors. It has the advantage of measuring the surface shape error of back-to-back aspherical mirrors with a common reference, and can simultaneously obtain the surface shape error and relative position error of the two mirrors. It can be used for the measurement and adjustment of back-to-back aspherical mirrors.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0006] A common-reference interferometry method for back-to-back aspherical mirrors, the method using two computational holographic compensators, namely a first CGH compensator and a second CGH compensator, the first CGH compensator being used to measure the first aspherical mirror in the back-to-back aspherical mirrors, and the second CGH compensator being used to measure the second aspherical mirror in the back-to-back aspherical mirrors, the first CGH compensator and the second CGH compensator using the same laser spherical wave interferometer;

[0007] The first CGH compensator comprises four annular regions, from the outside to the inside: an auxiliary alignment hologram of the first CGH compensator, a test master hologram of the first CGH compensator, an attitude alignment hologram of the first CGH compensator, and a non-holographic transmission region of the first CGH compensator. The auxiliary alignment hologram of the first CGH compensator is used to align the first CGH compensator with the laser spherical wave interferometer to obtain the auxiliary alignment holographic interference fringe pattern of the first CGH compensator. The test master hologram of the first CGH compensator is used to obtain the test master holographic interference fringe pattern of the first CGH compensator, which is then processed to obtain the surface shape error distribution of the first aspherical mirror. The attitude alignment hologram of the first CGH compensator is used to align the attitude of the second CGH compensator with the first CGH compensator. The non-holographic transmission region of the first CGH compensator is used to measure the second aspherical mirror and to align the second CGH compensator with the laser spherical wave interferometer.

[0008] The second CGH compensator comprises three annular regions, from the outside to the inside: the test master hologram of the second CGH compensator, the non-holographic reflection region of the second CGH compensator, and the auxiliary alignment hologram of the second CGH compensator. The test master hologram of the second CGH compensator is used to obtain the test master holographic interference fringe pattern of the second CGH compensator, which is then processed to obtain the surface shape error distribution of the second aspherical mirror. The non-holographic reflection region of the second CGH compensator is used to align the attitude of the second CGH compensator with that of the first CGH compensator, resulting in the attitude alignment holographic interference fringe pattern of the second CGH compensator. The auxiliary alignment hologram of the second CGH compensator is used to align the second CGH compensator with the laser spherical wave interferometer and the first CGH compensator, resulting in the auxiliary alignment holographic interference fringe pattern of the second CGH compensator.

[0009] The auxiliary alignment holographic interference fringe pattern of the first CGH compensator, the test master holographic interference fringe pattern of the first CGH compensator, the test master holographic interference fringe pattern of the second CGH compensator, the attitude alignment holographic interference fringe pattern of the second CGH compensator, and the auxiliary alignment holographic interference fringe pattern of the second CGH compensator are all simultaneously obtained through the interferometer detector set in the laser spherical wave interferometer. During measurement, it is first ensured that the auxiliary alignment holographic interference fringe pattern of the first CGH compensator, the attitude alignment holographic interference fringe pattern of the second CGH compensator, and the auxiliary alignment holographic interference fringe pattern of the second CGH compensator are all in a zero-fringe state. The test master holographic interference fringe patterns of the first CGH compensator and the test master holographic interference fringe patterns of the second CGH compensator are processed to obtain the surface shape error of the first aspherical mirror and the second aspherical mirror and their relative position error.

[0010] In the aforementioned common reference interferometry method for back-to-back aspherical mirrors, preferably, the auxiliary alignment hologram of the first CGH compensator is a reflective hologram, used to reflect the test beam emitted by the laser spherical wave interferometer to the auxiliary alignment hologram of the first CGH compensator, so that it returns to the laser spherical wave interferometer along the original path, forming the auxiliary alignment holographic interference fringe pattern of the first CGH compensator. The first CGH compensator is then adjusted to a zero-fringe state to achieve alignment of the first CGH compensator with the laser spherical wave interferometer.

[0011] The test master hologram of the first CGH compensator is a transmission type hologram, which is used to transmit the test beam emitted by the laser spherical wave interferometer to the test master hologram of the first CGH compensator, transform it into a normal incident beam onto the first aspherical mirror, and after being reflected by the first aspherical mirror, it returns to the laser spherical wave interferometer along the original path to form the test master holographic interference fringe pattern of the first CGH compensator. The laser spherical wave interferometer obtains the surface shape error distribution of the first aspherical mirror by processing the test master holographic interference fringe pattern of the first CGH compensator.

[0012] The attitude alignment hologram of the first CGH compensator is a transmission type hologram, which is used to transform the test beam emitted by the laser spherical wave interferometer to the attitude alignment hologram of the first CGH compensator into a collimated beam and then incident on the second CGH compensator, so that the attitude of the second CGH compensator is aligned with the first CGH compensator.

[0013] The non-holographic transmission area of ​​the first CGH compensator does not contain a holographic pattern. The test beam emitted by the laser spherical wave interferometer into the non-holographic transmission area of ​​the first CGH compensator is transmitted through and then incident on the second CGH compensator. This is used to measure the second aspherical mirror and to align the second CGH compensator with the laser spherical wave interferometer.

[0014] In the aforementioned common reference interferometry method for back-to-back aspherical mirrors, preferably, the test master hologram of the second CGH compensator is a reflective hologram, used to transform the test beam emitted by the laser spherical wave interferometer through the non-holographic transmission area of ​​the first CGH compensator, then through the test master hologram of the second CGH compensator into a normal incident beam onto the second aspherical mirror, and after reflection by the second aspherical mirror, return to the laser spherical wave interferometer along the original path, forming the test master holographic interference fringe pattern of the second CGH compensator. The laser spherical wave interferometer obtains the surface shape error distribution of the second aspherical mirror by processing the test master holographic interference fringe pattern of the second CGH compensator.

[0015] The non-holographic reflection area of ​​the second CGH compensator does not contain a holographic pattern. It is used to align the test beam emitted by the laser spherical wave interferometer through the attitude alignment hologram of the first CGH compensator, and then reflect it through the non-holographic reflection area of ​​the second CGH compensator so that it returns to the laser spherical wave interferometer along the original path, forming the attitude alignment holographic interference fringe pattern of the second CGH compensator. The two-dimensional tilt of the second CGH compensator is adjusted to the zero-fringe state so that the attitude of the second CGH compensator is aligned with the first CGH compensator.

[0016] The auxiliary alignment hologram of the second CGH compensator is a reflective hologram, which is used to reflect the test beam emitted by the laser spherical wave interferometer back to the laser spherical wave interferometer along the original path after passing through the non-holographic transmission area of ​​the first CGH compensator. This forms the auxiliary alignment holographic interference fringe pattern of the second CGH compensator. The three-dimensional translation of the second CGH compensator is adjusted to the zero-fringe state so that the second CGH compensator is aligned with the laser spherical wave interferometer.

[0017] Compared with the prior art, the advantages of the present invention are as follows:

[0018] The measurement method of the present invention can simultaneously obtain the surface shape error and the relative position error of the first aspherical mirror and the second aspherical mirror. During the measurement, all interference fringe patterns are simultaneously obtained on the interferometer detector. During the measurement, it is first ensured that the interference fringe patterns corresponding to the auxiliary alignment hologram and the attitude alignment hologram are in a zero-fringe state. By processing the interference fringe pattern corresponding to the test master hologram, the surface shape error and the relative position error of the two aspherical mirrors can be obtained simultaneously.

[0019] In this invention, the first CGH compensator and the second CGH compensator use the same laser spherical wave interferometer. The test light aligned with the second CGH compensator uses both spherical waves and plane waves, which can align the position and angle. Moreover, the main test hologram and the auxiliary alignment hologram of the second CGH compensator are both reflective holograms, and the wedge angles before and after do not affect the measurement results, making the measurement results more accurate. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the common reference interferometry method for back-to-back aspherical mirrors in Embodiment 1 of the present invention.

[0021] Figure 2 This is a schematic diagram of the holographic region of the first CGH compensator in Embodiment 1 of the present invention.

[0022] Figure 3 This is the measurement optical path diagram of the first aspherical mirror in Embodiment 1 of the present invention.

[0023] Figure 4This is a schematic diagram of the holographic region of the second CGH compensator in Embodiment 1 of the present invention.

[0024] Figure 5 This is the measurement optical path diagram of the second aspherical mirror in Embodiment 1 of the present invention.

[0025] Figure 6 This is the alignment optical path between the first CGH compensator and the second CGH compensator in Embodiment 1 of the present invention.

[0026] Figure 7 This is a schematic diagram of the region distribution of the interference fringe pattern obtained by the interferometer detector in Embodiment 1 of the present invention.

[0027] Legend:

[0028] 1. First CGH compensator; 11. Auxiliary alignment hologram of the first CGH compensator; 12. Test master hologram of the first CGH compensator; 13. Attitude alignment hologram of the first CGH compensator; 14. Non-holographic transmission area of ​​the first CGH compensator; 2. Second CGH compensator; 21. Test master hologram of the second CGH compensator; 22. Non-holographic reflection area of ​​the second CGH compensator; 23. Auxiliary alignment hologram of the second CGH compensator; 3. First aspherical mirror; 4. Second aspherical mirror; 5. Laser spherical wave interferometer; 6. Spherical wave test beam; 61. Test beam of the first CGH compensator aligned with the interferometer; 6 2. Test beam of the first aspherical mirror; 63. Test beam of the second CGH compensator aligned with the first CGH compensator; 64. Test beam of the second aspherical mirror; 65. Test beam of the second CGH compensator aligned with the interferometer; 7. Focal point of the spherical wave test beam; 81. Auxiliary alignment of the first CGH compensator with the holographic interference fringe region; 82. Test main holographic interference fringe region of the first CGH compensator; 83. Test main holographic interference fringe region of the first CGH compensator; 84. Test main holographic interference fringe region of the second CGH compensator; 85. Auxiliary alignment of the second CGH compensator with the holographic interference fringe region. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention. All materials and instruments used in the following embodiments are commercially available.

[0030] Example 1

[0031] The following will use an example of interferometry measurement of back-to-back aspherical mirrors to further illustrate the common reference interferometry method for back-to-back aspherical mirrors of the present invention. The common reference interferometry method for back-to-back aspherical mirrors of the present invention involves a first aspherical mirror 3 being an ellipsoid with a vertex radius of curvature of 478.56 mm and a quadratic constant k = -0.26452; and a second aspherical mirror 4 being an ellipsoid with a vertex radius of curvature of 654.16 mm and a quadratic constant k = -0.02107. The vertex distance between the two mirrors is 22.5 mm, both have an aperture of φ324 mm, and the diameter of the central obstruction aperture is 114 mm. Figure 1 As shown, a laser spherical wave interferometer 5 with a spherical lens is used to emit a spherical wave test beam 6. Two CGHs are used for measurement: a first CGH compensator 1 is used to measure the first aspherical mirror 3, and a second CGH compensator 2 is used to measure the second aspherical mirror 4. The first CGH compensator 1 includes an auxiliary alignment hologram for aligning itself with the interferometer; the second CGH compensator 2 also includes an auxiliary alignment hologram for aligning itself with both the interferometer and the first CGH compensator 1. During measurement, the laser spherical wave interferometer 5 is positioned to the left of the first aspherical mirror 3, the first CGH compensator 1 is positioned between the laser spherical wave interferometer 5 and the first aspherical mirror 3, and the second CGH compensator 2 is positioned to the right of the second aspherical mirror 4.

[0032] like Figure 2 As shown, the first CGH compensator 1 comprises four annular regions, which, from the outside to the inside, are:

[0033] 1) The auxiliary alignment hologram 11 of the first CGH compensator is a reflective hologram. The test beam (test beam 61 of the first CGH compensator aligning with the interferometer) emitted by the laser spherical wave interferometer 5 to the auxiliary alignment hologram 11 of the first CGH compensator is reflected back to the interferometer along its original path, forming interference fringes. This yields the auxiliary alignment holographic interference fringe pattern of the first CGH compensator. The first CGH compensator 1 is then adjusted to a zero-fringe state to achieve alignment of the first CGH compensator 1 with the interferometer. In this embodiment, the distance between the light-facing surface of the first CGH compensator 1 and the focal point 7 of the spherical wave test beam is 150mm. The phase function Φ of the auxiliary alignment hologram is described as follows:

[0034]

[0035] Where M = 1 represents the +1st order diffraction, ρ is the normalized polar coordinate with a normalized radius of 60 mm, N = 4, and the corresponding coefficient A i The values ​​(in rad) are: A1 = -79433.191, A2 = 3175.5423, A3 = -249.24467, A4 = 19.492883.

[0036] 2) The test master hologram 12 of the first CGH compensator is a transmission hologram. The test beam (test beam 62 of the first aspherical mirror) emitted by the laser spherical interferometer 5 to the test master hologram 12 of the first CGH compensator is transformed into a normal incident beam onto the first aspherical mirror 3 under test. After being reflected by the first aspherical mirror 3, it returns to the interferometer along the original path, forming interference fringes. The test master holographic interference fringe pattern of the first CGH compensator is obtained. The interferometer obtains the surface shape error distribution of the first aspherical mirror 3 by processing the interference fringe pattern. Figure 3 As shown, in this embodiment, the first CGH compensator 1 is a quartz plate with a thickness of 6.4 mm. The distance from the back surface of the first CGH compensator 1 to the first aspherical mirror 3 is 346 mm. The phase function Φ of the tested master hologram is described as follows:

[0037]

[0038] Where M = 3 represents the +3rd order diffraction, ρ is the normalized polar coordinate with a normalized radius of 50 mm, N = 5, and the corresponding coefficient A i The values ​​(in rad) are: A1 = 14085.186, A2 = -5072.776, A3 = 1428.8308, A4 = -384.40865, A5 = 65.180426.

[0039] 3) The attitude alignment hologram 13 of the first CGH compensator is a transmission hologram. The test beam emitted by the laser spherical wave interferometer 5 towards the attitude alignment hologram 13 of the first CGH compensator (the test beam 63 for the attitude alignment of the second CGH compensator with the first CGH compensator) is transmitted through it and transformed into a collimated beam, which is then incident on the second CGH compensator 2 for attitude alignment of the second CGH compensator 2 with the first CGH compensator 1. In this embodiment, the phase function Φ of the attitude alignment hologram is described as follows:

[0040]

[0041] Where M = 1 represents the +1st order diffraction, ρ is the normalized polar coordinate with a normalized radius of 16 mm, N = 2, and the corresponding coefficient A i The values ​​(in rad) are: A1 = -8472.8192, A2 = 23.896693.

[0042] 4) The non-holographic transmission area 14 of the first CGH compensator does not contain a holographic pattern. The test beam (the test beam 64 of the second aspherical mirror and the test beam 65 of the second CGH compensator alignment interferometer) emitted by the laser spherical wave interferometer 5 to the non-holographic transmission area 14 of the first CGH compensator passes through and is incident on the second CGH compensator 2, which is used to measure the alignment of the second aspherical mirror 4 and the second CGH compensator 2 with the interferometer.

[0043] like Figure 4 As shown, the second CGH compensator 2 contains three annular regions, which, from the outside to the inside, are:

[0044] 1) The test master hologram 21 of the second CGH compensator is a reflective hologram. A portion of the test beam (test beam 64 of the second aspherical mirror) emitted from the laser spherical interferometer 5 passes through the non-holographic transmission area 14 of the first CGH compensator, is reflected by the test master hologram 21 of the second CGH compensator, and transformed into a normal incident beam onto the tested second aspherical mirror 4. After reflection by the second aspherical mirror 4, it returns to the interferometer along the original path, forming interference fringes, thus obtaining the test master holographic interference fringe pattern of the second CGH compensator. The interferometer obtains the surface shape error distribution of the second aspherical mirror 4 by processing the interference fringe pattern. For example... Figure 5 As shown, in this embodiment, the second CGH compensator 2 is a quartz plate with a thickness of 6.4 mm. The distance from the light-facing surface of the second CGH compensator 2 to the second aspherical reflector 4 is 410 mm. The phase function Φ of the tested master hologram is described as follows:

[0045]

[0046] Where M = 1 represents the +1st order diffraction, ρ is the normalized polar coordinate with a normalized radius of 60 mm, N = 4, and the corresponding coefficient A i The values ​​(in rad) are: A1 = 54041.643, A2 = -1147.6015, A3 = 38.89781, A4 = -1.4720799.

[0047] 2) The non-holographic reflection area 22 of the second CGH compensator does not contain a holographic pattern. A portion of the test beam emitted from the laser spherical wave interferometer 5 (the test beam 63 of the second CGH compensator aligned with the first CGH compensator) passes through the alignment hologram 13 of the first CGH compensator and is reflected back to the interferometer via the non-holographic reflection area 22 of the second CGH compensator, forming interference fringes. This yields the alignment holographic interference fringe pattern of the second CGH compensator. Adjusting the two-dimensional tilt of the second CGH compensator 2 to a zero-fringe state achieves alignment of the second CGH compensator 2 with the first CGH compensator 1, i.e., the two CGH planes are parallel. For example... Figure 6 As shown.

[0048] 3) The auxiliary alignment hologram 23 of the second CGH compensator is a reflective hologram. A portion of the test beam emitted from the laser spherical wave interferometer 5 (the test beam 65 of the second CGH compensator aligned with the interferometer) passes through the non-holographic transmission region 14 of the first CGH compensator 1, and is reflected by the auxiliary alignment hologram 23 of the second CGH compensator, returning to the interferometer along its original path, forming interference fringes. This yields the auxiliary alignment holographic interference fringe pattern of the second CGH compensator. The three-dimensional translation of the second CGH compensator 2 is adjusted to a zero-fringe state, achieving alignment of the second CGH compensator 2 with the interferometer. In this embodiment, the distance between the light-facing surface of the second CGH compensator 2 and the backlight surface of the first CGH compensator 1 is 778.5 mm. The phase function Φ of the auxiliary alignment hologram is described as follows:

[0049]

[0050] Where M = 1 represents the +1st order diffraction, ρ is the normalized polar coordinate with a normalized radius of 20 mm, N = 2, and the corresponding coefficient A i The values ​​(in rad) are: A1 = -4257.4174, A2 = 0.48772848.

[0051] All the aforementioned interference fringe patterns were simultaneously obtained on the interferometer detector set in the laser spherical wave interferometer 5. Figure 7 The distribution of interference fringe patterns obtained by the interferometer detector is shown (specific interference fringe patterns are omitted). Each region represents: auxiliary alignment holographic interference fringe region 81 of the first CGH compensator, test master holographic interference fringe region 82 of the first CGH compensator, attitude alignment holographic interference fringe region 83 of the second CGH compensator, test master holographic interference fringe region 84 of the second CGH compensator, and auxiliary alignment holographic interference fringe region 85 of the second CGH compensator. During measurement, first ensure that the interference fringe patterns corresponding to the auxiliary alignment holography and attitude alignment holography (auxiliary alignment holographic interference fringe pattern of the first CGH, attitude alignment holographic interference fringe pattern of the second CGH, and auxiliary alignment holographic interference fringe pattern of the second CGH) are in a zero-fringe state. Processing the interference fringe patterns corresponding to the test master holography (test master holographic interference fringe pattern of the first CGH compensator and test master holographic interference fringe pattern of the second CGH compensator) simultaneously yields the surface shape error and relative position error of the first aspherical mirror 3 and the second aspherical mirror 4.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall still fall within the protection scope of the technical solutions of the present invention.

Claims

1. A common-reference interferometry method for back-to-back aspherical mirrors, characterized in that, The measurement method uses two computational holographic compensators, namely a first CGH compensator (1) and a second CGH compensator (2). The first CGH compensator (1) is used to measure the first aspherical mirror (3) in the back-to-back aspherical mirrors, and the second CGH compensator (2) is used to measure the second aspherical mirror (4) in the back-to-back aspherical mirrors. The first CGH compensator (1) and the second CGH compensator (2) use the same laser spherical wave interferometer (5). The first CGH compensator (1) comprises four annular regions, from the outside to the inside: the auxiliary alignment hologram (11) of the first CGH compensator, the test master hologram (12) of the first CGH compensator, the attitude alignment hologram (13) of the first CGH compensator, and the non-holographic transmission region (14) of the first CGH compensator. The auxiliary alignment hologram (11) of the first CGH compensator is used to align the first CGH compensator (1) with the laser spherical wave interferometer (5) to obtain the auxiliary alignment holographic interference fringe pattern of the first CGH compensator. The test master hologram (12) of the H compensator is used to obtain the test master hologram interference fringe pattern of the first CGH compensator. After processing, the surface shape error distribution of the first aspherical mirror (3) is obtained. The attitude alignment hologram (13) of the first CGH compensator is used to align the attitude of the second CGH compensator (2) with the first CGH compensator (1). The non-holographic transmission area (14) of the first CGH compensator is used to measure the second aspherical mirror (4) and align the second CGH compensator (2) with the laser spherical wave interferometer (5). The second CGH compensator (2) includes three annular regions, which, from the outside to the inside, are the test main hologram (21) of the second CGH compensator, the non-holographic reflection region (22) of the second CGH compensator, and the auxiliary alignment hologram (23) of the second CGH compensator. The test main hologram (21) of the second CGH compensator is used to obtain the test main holographic interference fringe pattern of the second CGH compensator. After processing, the surface shape error distribution of the second aspherical mirror (4) is obtained. The non-holographic reflection region (22) of the second CGH compensator is used to align the attitude of the second CGH compensator (2) with the first CGH compensator (1) to obtain the attitude alignment holographic interference fringe pattern of the second CGH compensator. The auxiliary alignment hologram (23) of the second CGH compensator is used to align the second CGH compensator (2) with the laser spherical wave interferometer (5) and the first CGH compensator (1) to obtain the auxiliary alignment holographic interference fringe pattern of the second CGH compensator. The auxiliary alignment holographic interference fringe pattern of the first CGH compensator, the test master holographic interference fringe pattern of the first CGH compensator, the test master holographic interference fringe pattern of the second CGH compensator, the attitude alignment holographic interference fringe pattern of the second CGH compensator, and the auxiliary alignment holographic interference fringe pattern of the second CGH compensator are all obtained simultaneously by the interferometer detector set in the laser spherical wave interferometer (5). During measurement, it is first ensured that the auxiliary alignment holographic interference fringe pattern of the first CGH compensator, the attitude alignment holographic interference fringe pattern of the second CGH compensator, and the auxiliary alignment holographic interference fringe pattern of the second CGH compensator are all in a zero-fringe state. The test master holographic interference fringe pattern of the first CGH compensator and the test master holographic interference fringe pattern of the second CGH compensator are processed to obtain the surface shape error of the first aspherical mirror (3) and the second aspherical mirror (4) and their relative position error.

2. The common reference interferometry method for back-to-back aspherical mirrors according to claim 1, characterized in that, The auxiliary alignment hologram (11) of the first CGH compensator is a reflective hologram, which is used to reflect the test beam emitted by the laser spherical wave interferometer (5) to the auxiliary alignment hologram (11) of the first CGH compensator, so that it returns to the laser spherical wave interferometer (5) along the original path, forming the auxiliary alignment holographic interference fringe pattern of the first CGH compensator. The first CGH compensator (1) is adjusted to the zero fringe state to realize the alignment of the first CGH compensator (1) with the laser spherical wave interferometer (5); The test master hologram (12) of the first CGH compensator is a transmission type hologram, which is used to transmit the test beam emitted by the laser spherical wave interferometer (5) to the test master hologram (12) of the first CGH compensator and transform it into a normal incident beam onto the first aspherical mirror (3). After being reflected by the first aspherical mirror (3), the beam returns to the laser spherical wave interferometer (5) along the original path to form the test master holographic interference fringe pattern of the first CGH compensator. The laser spherical wave interferometer (5) obtains the surface shape error distribution of the first aspherical mirror (3) by processing the test master holographic interference fringe pattern of the first CGH compensator. The first CGH compensator attitude alignment hologram (13) is a transmission type hologram, which is used to transform the test beam emitted by the laser spherical wave interferometer (5) to the first CGH compensator attitude alignment hologram (13) into a collimated beam and incident on the second CGH compensator (2) so that the attitude of the second CGH compensator (2) is aligned with the first CGH compensator (1). The non-holographic transmission area (14) of the first CGH compensator does not contain a holographic pattern. The test beam emitted by the laser spherical wave interferometer (5) to the non-holographic transmission area (14) of the first CGH compensator is transmitted through and then incident on the second CGH compensator (2) for measuring the second aspherical mirror (4) and aligning the second CGH compensator (2) with the laser spherical wave interferometer (5).

3. The common reference interferometry method for back-to-back aspherical mirrors according to claim 2, characterized in that, The test master hologram (21) of the second CGH compensator is a reflective hologram, used to transform the test beam emitted by the laser spherical wave interferometer (5) through the non-holographic transmission area (14) of the first CGH compensator, and after being reflected by the test master hologram (21) of the second CGH compensator, into a normal incident on the second aspherical mirror (4), and after being reflected by the second aspherical mirror (4), it returns to the laser spherical wave interferometer (5) along the original path to form the test master holographic interference fringe pattern of the second CGH compensator. The laser spherical wave interferometer (5) obtains the surface shape error distribution of the second aspherical mirror (4) by processing the test master holographic interference fringe pattern of the second CGH compensator. The non-holographic reflection area (22) of the second CGH compensator does not contain a holographic pattern. It is used to reflect the test beam emitted by the laser spherical wave interferometer (5) through the attitude alignment hologram (13) of the first CGH compensator and then reflect it back to the laser spherical wave interferometer (5) along the original path after passing through the non-holographic reflection area (22) of the second CGH compensator, forming the attitude alignment holographic interference fringe pattern of the second CGH compensator. The two-dimensional tilt of the second CGH compensator (2) is adjusted to the zero fringe state so that the attitude of the second CGH compensator (2) is aligned with the first CGH compensator (1). The auxiliary alignment hologram (23) of the second CGH compensator is a reflective hologram, which is used to reflect the test beam emitted by the laser spherical wave interferometer (5) through the non-holographic transmission area (14) of the first CGH compensator and back to the laser spherical wave interferometer (5) along the original path after being reflected by the auxiliary alignment hologram (23) of the second CGH compensator, forming the auxiliary alignment holographic interference fringe pattern of the second CGH compensator. The three-dimensional translation of the second CGH compensator (2) is adjusted to the zero fringe state so that the second CGH compensator (2) is aligned with the laser spherical wave interferometer (5).

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