A high-precision compensator suitable for large-aperture high-steepness aspheric surfaces

Abstract

The application discloses a high-precision compensator suitable for large-aperture high-steepness aspheric surfaces, comprising: a compensating mirror and a field lens group arranged in sequence along the same optical axis, the compensating mirror is used for balancing the primary spherical aberration of the aspheric surface to be measured, and the field lens group is used for imaging the compensating mirror on the aspheric surface to be measured and balancing the high-order spherical aberration of the aspheric surface to be measured, and the field lens group comprises a first field lens and a second field lens arranged in sequence along the optical axis. The application can realize high-precision detection of aspheric surfaces and provides an effective initial structure for high-precision detection of aspheric surfaces with equal or lower difficulty.

Description

Technical Field

[0001] This invention relates to the field of aspherical optical wavefront detection technology, and more specifically to a high-precision compensator suitable for large-diameter, high-steep aspherical surfaces. Background Technology

[0002] Currently, the testing of large-diameter, high-steep aspherical surfaces is typically achieved using comparison with equivalent wavefronts. This method requires a standard surface of the same diameter, making it difficult to achieve high-precision testing. Zero-compensation testing of the aspherical surface normal enables testing of large wavefronts with small wavefronts, thus providing a possibility for high-precision testing of large-diameter aspherical surfaces.

[0003] One of the keys to achieving Offner compensation testing of aspherical surfaces is to design a set of compensation mirrors for the aspherical surface being tested. The initial structure of a reliable and correct compensation mirror set is the foundation for successfully optimizing the system's optical design software. For large-aperture, high-steep aspherical surfaces, the accuracy requirements of the initial structure are even higher due to the poor stability of the compensation system.

[0004] Therefore, how to provide a high-precision compensator suitable for large-diameter, steep aspherical surfaces is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the present invention provides a high-precision compensator suitable for large-diameter, high-steep aspherical surfaces, which can realize high-precision detection of aspherical surfaces.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A high-precision compensator suitable for large-diameter, high-steep aspherical surfaces includes: a compensating mirror and a field mirror group arranged sequentially along the same optical axis. The compensating mirror is used to balance the primary spherical aberration of the aspherical surface under test, and the field mirror group is used to image the compensating mirror onto the aspherical surface under test and balance the higher-order spherical aberration of the aspherical surface under test.

[0008] The focal length of the field lens group is

[0009] In the formula, f′ 场 h 补 R 非 D 非 and l′ 场 These represent the focal length of the field lens group, the half-aperture of the compensating lens, the radius of curvature of the vertex of the aspherical surface under test, the aperture of the aspherical surface under test, and the distance from the field lens group to the center of curvature of the vertex of the aspherical surface under test, respectively.

[0010] The focal length of the compensating lens is

[0011] f′ 补 K, m场 and m represent the focal length of the compensating lens, the quadratic coefficient of the aspherical surface under test, the transverse magnification of the field lens group, and the combined magnification of the compensating lens and the field lens group, respectively. P 场 P 补 These are the field lens group, the compensation lens, and the digital PW form.

[0012] Preferably, the field lens group includes a first field lens and a second field lens arranged sequentially along the optical axis.

[0013] Preferably, the compensation mirror, the first field mirror, and the second field mirror are all spherical single lenses, and all are made of K9 glass.

[0014] Preferably, the radii of curvature of the front and rear surfaces of the compensation mirror, according to the direction of light propagation, are as follows:

[0015] R 11 =2(n-1)f' 补

[0016] R 12 =-2(n-1)f' 补

[0017] The first field mirror and the second field mirror have the same radius of curvature on their front and rear surfaces, which is:

[0018] R 单场1 =2(n-1)f' 场

[0019] R 单场2 =2(n-1)f' 场

[0020] In the formula, R 11 R 12 R represents the radii of curvature of the front and back surfaces of the compensating mirror, respectively. 单场1 R represents the radius of curvature of the front surfaces of the first and second field mirrors. 单场2 The radius of curvature of the back surface of the first and second field mirrors is represented by n, where n is the refractive index of the K9 glass material.

[0021] Preferably, the light-transmitting half-aperture of the compensation mirror is 155mm.

[0022] Preferably, the front and rear surface radii of curvature of the compensation mirror are 4512.735 mm and -254.460 mm, respectively; the front and rear surface radii of curvature of the first field mirror are 1314.578 mm and -918.738 mm, respectively; the front and rear surface radii of curvature of the second field mirror are 205.778 mm and 197.298 mm, respectively; the distance between the laser point source and the compensation mirror is 1255.050 mm; the distance between the compensation mirror and the first field mirror is 462.994 mm; the distance between the first field mirror and the second field mirror is 71.037 mm; the distance between the second field mirror and the aspherical surface to be measured is 4601.359 mm; and the thicknesses of the compensation mirror, the first field mirror, and the second field mirror are 80 mm, 15 mm, and 32 mm, respectively.

[0023] As can be seen from the above technical solution, compared with the prior art, the present invention discloses a high-precision compensator suitable for large-diameter, high-steep aspherical surfaces, which can realize high-precision detection of aspherical surfaces and provides an effective initial structure for high-precision detection of aspherical surfaces of equal or lower difficulty. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 The attached figure is a schematic diagram of a high-precision compensator structure suitable for large-diameter, steep aspherical surfaces provided by the present invention.

[0026] Figure 2 The attached figure is a schematic diagram of the detection optical system provided by the present invention.

[0027] Among them, 1. Compensation mirror, 2. First field mirror, 3. Second field mirror, 4. Laser spherical interferometer, 5. Aspherical surface to be measured, and 6. Field mirror group. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] This invention discloses a high-precision compensator suitable for large-diameter, steep aspherical surfaces, such as... Figure 2As shown, the detection system includes a laser spherical interferometer 4, a compensating mirror 1, a field lens group 6, and the aspheric surface to be tested 5, arranged sequentially along the same optical axis. The laser spherical interferometer 4 provides the interference light source for the aspheric surface detection system and processes the interference image. The compensating mirror 1 is used to balance most of the primary spherical aberrations of the aspheric surface to be tested 5. The field lens group 6 images the compensating mirror onto the aspheric surface to be tested 5 and balances the higher-order spherical aberrations of the aspheric surface to be tested 5.

[0030] The focal length of the field lens group is

[0031] In the formula, f′ 场 h 补 R 非 D 非 and l′ 场 These represent the focal length of the field lens group, the half-aperture of the compensating lens, the radius of curvature of the vertex of the aspherical surface under test, the aperture of the aspherical surface under test, and the distance from the field lens group to the center of curvature of the vertex of the aspherical surface under test, respectively.

[0032] According to the Offner compensation principle, the aberrations generated by the compensator twice balance the normal aberration of the aspherical surface. That is:

[0033]

[0034] and These represent the primary spherical aberration coefficients of the compensating mirror, the field mirror group, and the aspherical mirror under test, respectively. Using the sum of lens focal length and aberrations in aberration theory and PW theory, the following can be derived:

[0035] The focal length of the compensating lens is

[0036] f′ 补 K, m 场 and m represent the focal length of the compensating lens, the quadratic coefficient of the aspherical surface under test, the transverse magnification of the field lens group, and the combined magnification of the compensating lens and the field lens group, respectively. P 场 P 补 These are the field lens group, the compensation lens, and the digital PW form.

[0037] Furthermore, such as Figure 1 As shown, the field lens group 6 includes a first field lens 2 and a second field lens 3 arranged sequentially along the optical axis. The first field lens 2 and the second field lens 3 are located near the image point of the compensating lens 1, and the air gap between them is as small as possible.

[0038] The radii of curvature of the front and rear surfaces of the compensating mirror, according to the direction of light propagation, are as follows:

[0039] R 11 =2(n-1)f' 补

[0040] R 12 =-2(n-1)f' 补

[0041] The radii of curvature of the front and rear surfaces of the first and second field mirrors are the same:

[0042] R 单场1 =2(n-1)f' 场

[0043] R 单场2 =2(n-1)f' 场

[0044] In the formula, R 11 R 12 R represents the radii of curvature of the front and back surfaces of the compensating mirror, respectively. 单场1 R represents the radius of curvature of the front surfaces of the first and second field mirrors. 单场2 The radius of curvature of the back surface of the first and second field mirrors is represented by n, where n is the refractive index of the K9 glass material.

[0045] Furthermore, the half-aperture of the compensating mirror is 155mm.

[0046] The point light source in the system is generated by a laser spherical interferometer with a wavelength of 632.8 nm. The spherical standard lens has an F-number of less than 4. The compensating mirror is set as an aperture stop, the object intercept from the point light source to the compensating mirror is 1255.05, the entrance pupil diameter is 310 mm, and the aperture of the aspherical surface under test exceeds 3 m.

[0047] The compensating lens, the first field lens, and the second field lens are all spherical single lenses made of K9 material. Their specific geometric parameters are shown in Table 1 below.

[0048] Table 1 Geometric Parameters

[0049] <![CDATA[R 11 ]]> <![CDATA[R 12 ]]> <![CDATA[R 21 ]]> <![CDATA[R 22 ]]> <![CDATA[R 31 ]]> <![CDATA[R 32 ]]> <![CDATA[d0]]> 4512.735 -254.460 1314.578 -918.738 205.778 197.298 1255.050 <![CDATA[d1]]> <![CDATA[d2]]> <![CDATA[d3]]> <![CDATA[t1]]> <![CDATA[t2]]> <![CDATA[t3]]> 462.994 71.037 4601.359 80 15 32

[0050] R 11 and R 12 R is the radius of curvature of the front and rear surfaces of the compensating mirror. 21 and R 22 R is the radius of curvature of the front and rear surfaces of the first field mirror. 31 and R 32 Let d0 be the radius of curvature of the front and rear surfaces of the second field mirror. d0, d1, d2, and d3 be the distances between the laser point source and the compensating mirror, the compensating mirror and the first field mirror, the first field mirror and the second field mirror, and the second field mirror and the aspherical surface under test, respectively. t1, t2, and t3 be the thicknesses of the compensating mirror, the first field mirror, and the second field mirror, respectively.

[0051] The technical effects of the present invention were verified through experiments:

[0052] Taking the high-precision detection of a parabolic reflector laser interferometer with a diameter of 3m and a focal length of 2250mm as an example, the parameters of the compensator of this invention are imported into the optical design software as the initial structure and set as variables. The aspherical light-passing aperture is used as a special constraint to start optimization, and the final residual wave aberration PV value λ / 60 and RMS value λ / 500 are achieved.

[0053] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to the method section.

[0054] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A high-precision compensator suitable for large-diameter, steeply spherical surfaces, characterized in that, include: A compensating mirror and a field lens group are arranged sequentially along the same optical axis. The compensating mirror is used to balance the primary spherical aberration of the aspheric surface under test, and the field lens group is used to image the compensating mirror onto the aspheric surface under test and balance the higher-order spherical aberration of the aspheric surface under test. The focal length of the field lens group is , In the formula, , , and These represent the focal length of the field lens group, the half-aperture of the compensating lens, the radius of curvature of the vertex of the aspherical surface under test, the aperture of the aspherical surface under test, and the distance from the field lens group to the center of curvature of the vertex of the aspherical surface under test, respectively. The focal length of the compensating lens is , , , and These represent the focal length of the compensating lens, the quadratic coefficient of the aspherical surface under test, the transverse magnification of the field lens group, and the combined magnification of the compensating lens and the field lens group, respectively. , These are the field lens group, the compensation lens, and the digital PW form introduced by the lens; The field lens group includes a first field lens and a second field lens arranged sequentially along the optical axis. The radii of curvature of the front and rear surfaces of the compensating mirror, according to the direction of light propagation, are as follows: ； ； The first field mirror and the second field mirror have the same radius of curvature on their front and rear surfaces, which is: ； ； In the formula, These represent the radii of curvature of the front and rear surfaces of the compensating mirror, respectively. Represents the radius of curvature of the front surface of the first and second field mirrors. n represents the radius of curvature of the back surfaces of the first and second field mirrors. 11 n 12 n1 represents the refractive index of the front and rear surfaces of the compensating mirror, n2 represents the refractive index of the front surface of the first and second field mirrors, and n2 represents the refractive index of the rear surface of the first and second field mirrors. The compensating mirror has a half-aperture of 155 mm; the front and rear surface radii of curvature of the compensating mirror are 4512.735 mm and -254.460 mm, respectively; the front and rear surface radii of curvature of the first field mirror are 1314.578 mm and -918.738 mm, respectively; the front and rear surface radii of curvature of the second field mirror are 205.778 mm and 197.298 mm, respectively; the distance between the laser point source and the compensating mirror is 1255.050 mm; the distance between the compensating mirror and the first field mirror is 462.994 mm; the distance between the first field mirror and the second field mirror is 71.037 mm; the distance between the second field mirror and the aspherical surface to be measured is 4601.359 mm; and the thicknesses of the compensating mirror, the first field mirror, and the second field mirror are 80 mm, 15 mm, and 32 mm, respectively.

2. A high-precision compensator suitable for large-diameter, high-steep aspherical surfaces according to claim 1, characterized in that, The compensation mirror, the first field mirror, and the second field mirror are all spherical single lenses, and all are made of K9 glass.

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