Refraction-reflection telescope optical system with quasi-clear characteristic and adjustment method

Abstract

The invention discloses a catadioptric telescope optical system with a quasi-clarity characteristic and an adjustment method of the catadioptric telescope optical system. The system comprises a primary lens, a secondary lens, a correction lens group, a system focal plane and a conjugate image point, light rays sequentially pass through the primary lens, the secondary lens and the correction lens group to reach the system focal plane, the correction lens group at least comprises one correction lens, the correction lens is a correction lens D with a clarity characteristic, and when the correction lens group comprises two or more correction lenses, the conjugate image point reaches the system focal plane. The concave surface of the correction lens D is a conjugate image point reflecting surface; and a distance d is formed between the system focal plane and a conjugate image point. On the premise of keeping the original structural advantages of the refraction and reflection optical system, the system has a clear installation and adjustment reference point, and the installation and adjustment steps are simplified; extra aberration is not introduced due to the application of the similar-to-clear lens; when the interferometer axially moves by a distance of d, the focus is just the center of sphere of the concave surface of the lens, the interferometer can measure straight stripes, system imaging of auto-collimation reflection of the plane mirror is in an out-of-focus state, and characteristics are clear and convenient to compare.

Description

Technical Field

[0001] The invention belongs to the field of astronomical instruments, and in particular relates to a catadioptric telescope optical system with quasi-aluminum characteristics and an adjustment method thereof. Background Art

[0002] Most astronomical imaging optical systems that take into account large aperture, large field of view, and high imaging quality are of the catadioptric type. The field of view of a transmissive optical system can be made larger, but due to the limitation of material size, it is difficult to break through the aperture; the aperture of a reflecting telescope can usually be made very large, but due to the limitation of the reflecting telescope's ability to correct aberrations, the usable field of view of this type of telescope is generally very small. The main focus and Cassegrain focus of the classic Cassegrain system only eliminate spherical aberration. Although the commonly used RC system eliminates spherical aberration and coma, due to the existence of astigmatism and field curvature, the field of view with good image quality is still not very large. In order to improve the image quality and obtain a larger working field of view, it is necessary to add a transmission element in front of the focus to correct the aberration, which is a catadioptric optical system.

[0003] Most of the current mainstream large-aperture and large-field telescopes are catadioptric telescopes. The 4-meter VISTA telescope adopts an RC plus corrector mirror catadioptric design, with 4 correctors at the infrared end and a field of view of 1.65°, and 3 correctors and 2 atmospheric dispersion mirrors at the visible end, with a field of view of 2.1 degrees; the 2.6-meter JST telescope, the corrector group consists of 3 aspherical lenses, with a field of view of 3 degrees; the Sloan Survey Telescope, the corrector group consists of 2 lenses, with a field of view of 3 degrees. In terms of the prime focus catadioptric type, the 4-meter aperture Dark Energy Spectrometer DESI, with 4 correcting mirrors and 2 atmospheric dispersion correcting mirrors added in front of the prime focus, can achieve an ultra-large field of view of 5°; the 0.7-meter aperture MASTA large field of view telescope and 2.5-meter aperture WFST telescope under development in China are both prime focus telescopes; in terms of the Schmidt catadioptric type, the United States 0.95-meter aperture Kepler Mission telescope, the 1.2-meter China Xuyi Near-Earth Object Search Telescope, and the 0.5-meter China Antarctic Survey Telescope are all of this type.

[0004] For the optical system of a catadioptric telescope, the optical system design, optical component processing, system adjustment, etc. will directly affect the imaging quality of the optical system, among which system adjustment is particularly critical. In the traditional catadioptric system, it is necessary to repeatedly debug and correct the three-dimensional posture of the mirror group during adjustment. There are many uncertain factors, the source of error is difficult to determine, and the error size is difficult to quantify. It is particularly critical to consider the design of the adjustment reference during optical design. The existing satellite payload off-axis three-mirror system adopts the main three-mirror common reference design method, and the main mirror and the mother mirror of the three mirrors are designed coaxially to reduce the subsequent adjustment work and improve the adjustment efficiency; there are also double-sided co-body reflectors, and different optical surfaces are processed on the same mirror body to reduce the degree of freedom of adjustment. These methods can increase the stability of the system and improve the adjustment efficiency. However, this method is not applicable to the coaxial catadioptric telescope optical system. The Qiming characteristic of the optical system refers to the existence of a pair of conjugate image points on the axis that simultaneously eliminate spherical aberration and coma. This characteristic is widely used in small-aperture microscope systems, illumination systems, and optical measurement systems. Summary of the invention

[0005] In view of the above-mentioned problems existing in the prior art, the present invention provides a catadioptric astronomical telescope optical system and an adjustment method thereof with a quasi-Qiming characteristic. The present invention applies the object-image conjugate relationship of the Qiming characteristic to the correction lens group of the catadioptric optical system, and designs a catadioptric astronomical telescope optical system with a quasi-Qiming characteristic by controlling the operands. When the system is adjusted, the position of the correction lens group can be quickly located by utilizing the coaxial and aberration-free characteristics of the two conjugate image points, thereby shortening the adjustment time. At the same time, the application of the conjugate image points does not introduce additional aberrations. In addition, by optimizing the conjugate distance, the reflected image of the optical element near the focal plane can be controlled to be exactly at the mid-aperture obstruction position of the catadioptric system, thereby avoiding the ghost interference formed by the two conjugate image points during measurement.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A catadioptric telescope optical system with a quasi-clear characteristic comprises a primary mirror, a secondary mirror, a correction mirror group, a system focal plane, and a conjugate image point. Light passes through the primary mirror, the secondary mirror, and the correction mirror group in sequence to reach the system focal plane. The correction mirror group comprises at least one correction mirror, which is a correction mirror D with a clear characteristic. When the correction mirror group comprises two or more correction mirrors, the correction mirror D is closest to the system focal plane. The side of the correction mirror D close to the system focal plane is a spherical concave surface, and its vertex curvature radius is R1. The side of the correction mirror D away from the system focal plane is a spherical convex surface, and its vertex curvature radius is R2. The center thickness of the correction mirror D is , the corrector D satisfies the condition ,in, is the refractive index of the correction mirror D, n is the refractive index of the medium, in the catadioptric telescope optical system, the concave surface of the correction mirror D is the conjugate image point reflection surface, the center of the concave surface is the location of the conjugate image point, and there is a distance d between the focal plane of the system and the conjugate image point.

[0008] Furthermore, the primary mirror and the secondary mirror are both aspherical reflectors, and the surface shape is a quadratic hyperbolic surface or a high-order aspherical surface.

[0009] Furthermore, the correcting lens D can be combined with other optical surfaces to correct off-axis aberrations without introducing additional aberrations.

[0010] Furthermore, the distance d ranges from 5 to 10 mm.

[0011] A method for assembling and adjusting a catadioptric telescope optical system with quasi-Qiming characteristics is provided. An interferometer point light source is placed at the focal plane of the system. A part of the spherical light beam emitted by the point light source passes through a correction mirror group, is reflected by a secondary mirror and a primary mirror in sequence, and finally is reflected by a self-collimating plane mirror and then returns to the original path to form system interference fringes. A part of the light beam is directly reflected back to the interferometer by the concave surface of the correction mirror D to form reference interference fringes. Since there is a distance d between the focal plane of the system and a conjugate image point, the existence of defocus makes the reference interference fringes present in a concentric ring shape. By adjusting the tilt and pitch posture of the correction mirror group, the reference interference fringes are located at the center of the interferometer field of view, that is, the secondary mirror blocking center position. At this time, the optical axis of the correction mirror group is coaxial with the optical axes of the primary mirror and the secondary mirror.

[0012] Furthermore, when the correcting lens group includes two or more correcting lenses, the correcting lens group is individually adjusted using a centering instrument and then integrated with the primary mirror and the secondary mirror system.

[0013] Furthermore, the installation and adjustment method comprises the following steps:

[0014] Step 1: The primary and secondary mirror reflection systems are tested and adjusted using an interferometer;

[0015] Step 2: After the installation and adjustment is completed, the interferometer remains in place, the interferometer point light source is placed at the focal plane of the system, and the correction lens group is preliminarily installed;

[0016] The spherical wave beam emitted by the interferometer point light source is directly reflected back to the interferometer by the concave surface of the correction mirror D to form reference interference fringes. If the optical axis of the correction mirror group coincides with the optical axis of the interferometer, the returned reference interference fringes are in the center of the interferometer field of view and are concentric rings. Otherwise, adjust the tilt and pitch attitude of the correction mirror group until the returned reference fringes are in the center of the interferometer field of view and are concentric rings.

[0017] The spherical wave beam emitted by the interferometer point light source passes through the correction mirror group, is reflected by the secondary mirror and the primary mirror in turn, and finally is reflected by the self-collimating plane mirror and returns to the original path to form system interference fringes. The axial distance of the correction mirror group is adjusted to make the system interference fringes straight fringes, while keeping the reference interference fringes in the center of the interferometer field of view;

[0018] Step 3: Move the interferometer axially until the central reference stripes change from concentric circles to straight stripes. At this time, the interferometer focus should be exactly at the concave sphere center of the corrector D. Measure the distance the interferometer moves axially. If the deviation between this distance and the theoretical distance d between the system focal plane and the conjugate image point is less than the preset value, it means that the corrector assembly is adjusted in place.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention provides a catadioptric telescope optical system with quasi-QIM characteristics. The system is a catadioptric optical system with a large field of view and good imaging quality.

[0021] 2. The traditional catadioptric telescope optical system is improved and designed in combination with the characteristics of the Qiming lens. The Qiming lens is applied to the correction lens group of the catadioptric optical system. This makes the optical system have a clear adjustment reference point while maintaining the original structural advantages of the catadioptric optical system, simplifies the adjustment steps of the catadioptric optical system, and improves the adjustment accuracy.

[0022] 3. The application of the ZM-type lens of the present invention does not introduce additional aberrations and can cooperate with other optical elements to correct off-axis aberrations.

[0023] 4. The Zimmern-like lens of the present invention can make the interference reference fringes fall exactly into the central hole blocking area of ​​the refraction and reflection system by controlling d, without affecting the high-precision adjustment of the system.

[0024] 5. When the interferometer moves axially a distance of d, the focus is exactly the center of the sphere of the lens R1 surface. The interferometer can measure straight fringes, while the system imaging of the plane mirror self-collimation reflection is in a defocused state. The characteristics are clear and convenient for comparison. By comparing the measured distance d with the theoretically calculated distance d, the correctness of the system can be roughly judged. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the optical structure of the system of the present invention;

[0026] Figure 2 This is the principle diagram of the Qiming lens;

[0027] Figure 3 This is a schematic diagram of the Qiming-like lens of the present invention;

[0028] Figure 4 is a light path diagram of an embodiment of the present invention;

[0029] Figure 5 is a point diagram of an embodiment of the present invention;

[0030] Figure 6 This is a schematic diagram of the installation and adjustment principle of an embodiment of the present invention;

[0031] Figure 7 The interferometer is located at Figure 3 Interference fringe images at position S3 are shown; (a) the concentric rings in the image are not in the center, indicating that the correction lens group is misaligned, and (b) the concentric rings in the image are in the center, indicating that the correction lens group is aligned;

[0032] Markings in the figure: 1-primary mirror; 2-secondary mirror; 3-correction mirror A; 4-correction mirror B; 5-correction mirror C; 6-correction mirror D; 7-system focal plane; 8-conjugate image point; 9-plane reflecting mirror; 10-correction mirror group; 11-conjugate plane return light; 12-interferometer. DETAILED DESCRIPTION

[0033] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0034] The present invention discloses a catadioptric telescope optical system with quasi-Qiming characteristics, comprising: a primary mirror 1, a secondary mirror 2, a correcting mirror A3, a correcting mirror B4, a correcting mirror C5, a correcting mirror D6, a system focal plane 7, and a conjugate image point 8, wherein light sequentially passes through the primary mirror 1, the secondary mirror 2, the correcting mirror A3, the correcting mirror B4, the correcting mirror C5, and the correcting mirror D6 to reach the system focal plane 7, such as Figure 1 shown.

[0035] The concave surface of the correcting mirror D is a conjugate image point reflection surface, and the vertex curvature radius thereof is designed to be a specific value according to system parameters.

[0036] The concave spherical center of the correcting mirror D is the location of the conjugate image point 8 .

[0037] The distance d between the system focal plane 7 and the conjugate image point 8 is determined by the relative aperture of the system.

[0038] The primary mirror and the secondary mirror are both aspherical reflectors, made of glass or SIC, with a surface shape of a quadratic hyperboloid or a high-order aspherical surface, and the surface shape is determined by the following formula:

[0039]

[0040] In the formula, is the vertex curvature, K is the quadratic constant, d, e... are coefficients, It is the loss of height of the aspheric surface.

[0041] The correction lens group is composed of spherical or aspherical surfaces, and the element close to the focal plane must be a spherical surface.

[0042] The principle of the Qiming lens is as follows Figure 2 As shown, the vertex curvature radius of the first surface of the Qiming lens is R1, the vertex curvature radius of the second surface is R2, and point O2 is the center of the sphere of R1. The light emitted by O2 does not deflect when passing through the R1 surface, but refracts at point P on the R2 surface. The reverse extension line of the refracted light intersects at point O1. O1 and O2 are aligned points and must meet the following conditions:

[0043]

[0044] Where R1 is the radius of curvature of the first vertex, R2 is the radius of curvature of the second vertex, a is the center thickness of the lens, is the refractive index of the lens, and n is the refractive index of the medium.

[0045] The principle of the Qiming lens in the present invention is as follows Figure 3 As shown, the light is emitted from point S3, and after being refracted by the lens, the reverse extension line intersects at point S1, but S3 is not the center of the first sphere. The center of the first sphere is S2. When designing the refractive optical system, the focal plane position is reasonably optimized and controlled to be located at S3. At this time, the Zigzag lens does not introduce additional aberrations, and can be combined with other optical surfaces to correct off-axis aberrations.

[0046] The quasi-color characteristic, the distance d between S2 and S3, is determined by the number of fringes produced by defocusing. According to the aberration requirements, it should not be too large, otherwise the interferometer fringes will be too dense. According to the experience of interferometer use, d needs to be controlled at 5~10mm when the fringes are clearer.

[0047] In the catadioptric optical system with quasi-Qiming characteristics, when the correction mirror group and the primary and secondary mirror systems are self-collimated and adjusted, the interferometer point light source is placed at the focal plane S3 of the system, a part of the spherical light beam emitted by the point light source passes through the correction mirror group, is reflected by the secondary mirror and the primary mirror in sequence, and finally is reflected by the self-collimating plane mirror and then returns to the original path to form interference fringes, and a very small part of the light is directly reflected back to the interferometer by the lens R1 surface of the correction mirror group to form reference interference fringes. Since S3 is a certain distance d from the center of the sphere S2, the existence of defocus makes the reference interference fringes become concentric rings, and the posture of the correction mirror group is adjusted (the primary and secondary mirror systems and the interferometer have been aligned and adjusted) so that the concentric rings are located at the center of the interferometer field of view, that is, the secondary mirror blocking center position. At this time, it can be quickly determined that the optical axis of the correction mirror group is coaxial with the optical axes of the primary and secondary mirrors, thereby simplifying the adjustment steps.

[0048] When the quasi-QM-type catadioptric optical system is adjusted, the size of d can be controlled so that the area of ​​the reference interference fringe is smaller than the area formed by the central hole obstruction, thereby not affecting the test of the imaging quality of the system.

[0049] The structural schematic diagram of the 2.5-meter aperture catadioptric optical system of this embodiment is as follows: Figure 4 As shown, its point diagram is as follows Figure 5 As shown, the parameters of the system are as follows:

[0050] Effective caliber: 2.5 meters

[0051] Optical field of view: Full field of view 2.8°

[0052] Working band: 0.45um~0.75um

[0053] System focal length: 10000mm

[0054] Image quality: 80% of the energy is concentrated within a diameter of 18um

[0055] The concave surface of the correction mirror D is the conjugate image point reflection surface, and its vertex curvature radius R0 = 562.96mm. The focal plane is 571.32mm away from the center of the concave surface of the correction mirror D, and d = 8.36mm is calculated.

[0056] The parameters of the grid elements in this optical system are as follows:

[0057]

[0058] Image quality evaluation of the 2.5-meter catadioptric optical system: full field of view 2.8°, 80% of the energy in the 0.45um~0.75um band is concentrated within a diameter of 16um, there is little difference in on-axis and off-axis energy concentration, and the imaging is uniform.

[0059] like Figure 6 As shown, the mirror surface closest to the focal plane of the 2.5-meter catadioptric optical system has a quasi-clear characteristic. The correction mirror group is adjusted separately using a centering instrument and then integrated with the primary mirror and secondary mirror system. The correction mirror group and the optical axes of the primary and secondary mirrors need to be strictly aligned during system adjustment. Two interference fringes are generated during system adjustment. One is that a spherical wave beam is emitted from the focus of the interferometer, which passes through the correction mirror group, is reflected by the secondary mirror and the primary mirror, and then is reflected back to the interferometer by a standard plane reflector to form a system interference fringe area. The other is that a spherical wave beam is emitted from the focus of the interferometer, which is directly reflected back by the conjugate surface to form a conjugate surface return image. The return image of the correction mirror group and the return image of the optical system are simultaneously collected on the interferometer CCD (the interference fringe image of the interferometer at the focal plane of the system is shown as Figure 7 As shown in the figure), adjust the tilt and pitch of the correction mirror group so that the conjugate return image is located at the center of the secondary mirror obstruction, that is, Figure 7 The state shown in (a) is adjusted to Figure 7 The state shown in (b) indicates that the optical axis of the correction mirror group coincides with the optical axes of the primary and secondary mirrors, which simplifies the installation and adjustment steps and improves the installation and adjustment efficiency.

[0060] When the interferometer moves axially a distance of d, the focus is exactly the center of the concave surface of the correcting mirror D-6. The interferometer can measure straight fringes, while the system imaging of the plane mirror self-collimation reflection is in a defocused state. The characteristics are clear and convenient for comparison. By comparing the measured distance d with the theoretically calculated d=8.36mm, if there is a deviation in the distance, it means that the axial spacing of the correcting mirror group is incorrect. The correcting mirror can be adjusted axially according to the positive and negative deviation to accurately locate the position of the correcting mirror.

[0061] The specific installation steps of the system are as follows:

[0062] (1) After the primary and secondary mirror reflection systems are tested and adjusted using an interferometer, the interferometer remains in place. Figure 6 As shown, the corrective lens group is preliminarily installed;

[0063] (2) The spherical wave beam emitted by the interferometer point light source is directly reflected back to the interferometer by the concave surface of the correction mirror group D-6 to form reference interference fringes. If the correction mirror and the interferometer optical axis coincide, the returned reference fringes are in the center of the interferometer field of view and are concentric rings. Otherwise, adjust the tilt of the correction mirror group.

[0064] (3) The spherical light beam emitted by the interferometer point light source passes through the correction mirror group, is reflected by the secondary mirror and the primary mirror in turn, and finally is reflected by the self-collimating plane mirror and returns to the original path to form interference fringes. The axial distance of the correction mirror is adjusted to make the interferometer fringes straight fringes, while keeping the reference fringes in the center of the interferometer field of view.

[0065] (4) Adjust the interferometer axial distance d, and use the interferometer focus to be exactly at the center of the D-6 concave sphere. At this time, the central reference stripes change from concentric circles to straight stripes. Measure the adjusted distance d and compare it with the theoretical design value d=8.36mm. The small deviation indicates that the corrective mirror assembly is adjusted in place.

[0066] The present invention discloses a catadioptric telescope optical system with quasi-Qiming characteristics, which is a catadioptric optical system with a large field of view and good imaging quality. The present invention applies a Qiming lens to the correction lens group of the catadioptric optical system, so that the optical system has a clear adjustment reference point while maintaining the original structural advantages of the catadioptric optical system, simplifies the adjustment steps of the catadioptric optical system, and improves the adjustment accuracy. During the design, the reflection image point of the optical element near the focal plane is controlled to be close to the conjugate with the image point on the system axis. When the system is adjusted, the coaxial and aberration-free characteristics of the two conjugate image points are used to accurately position the correction lens group, thereby shortening the adjustment time. The application of the Qiming-like lens of the present invention does not introduce additional aberrations, and can cooperate with other optical elements to jointly correct off-axis aberrations. The Qiming-like lens of the present invention can make the interference reference fringes fall into the central aperture blocking area of ​​the catadioptric system by controlling d, without affecting the high-precision adjustment of the system. When the interferometer moves axially by a distance of d, the focus is exactly the center of the sphere of the lens R1 surface, and the interferometer can measure straight fringes, while the system imaging of the plane mirror self-collimation reflection is in a defocused state, with clear features and convenient comparison. By comparing the measured distance d with the theoretically calculated d, the correctness of the system can be roughly judged. By optimizing the conjugate distance, the reflected image of the optical element near the focal plane can be controlled to be exactly at the center hole blocking position of the refraction and reflection system, thereby avoiding the ghost interference formed by the two conjugate image points during measurement.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A catadioptric telescope optical system with quasi-Qiming characteristics, characterized in that: The invention comprises a primary mirror, a secondary mirror, a correction mirror group, a system focal plane, and a conjugate image point. Light sequentially passes through the primary mirror, the secondary mirror, and the correction mirror group to reach the system focal plane. The correction mirror group comprises at least one correction mirror, and the correction mirror is a correction mirror D with a uniform brightness characteristic. When the correction mirror group comprises two or more correction mirrors, the correction mirror D is closest to the system focal plane. The side of the correction mirror D close to the system focal plane is a spherical concave surface, and its vertex curvature radius is R1. The side of the correction mirror D away from the system focal plane is a spherical convex surface, and its vertex curvature radius is R2. The center thickness of the correction mirror D is , the corrector D satisfies the condition ,in, is the refractive index of the correction mirror D, n is the refractive index of the medium, in the catadioptric telescope optical system, the concave surface of the correction mirror D is the conjugate image point reflection surface, the center of the concave surface is the location of the conjugate image point, and there is a distance d between the focal plane of the system and the conjugate image point.

2. A catadioptric telescope optical system with quasi-QMI characteristics according to claim 1, characterized in that: The primary mirror and the secondary mirror are both aspherical reflectors, and the surface shape is a quadratic hyperboloid or a high-order aspherical surface.

3. The catadioptric telescope optical system with quasi-aluminum characteristics according to claim 1, characterized in that: The correcting lens D can be combined with other optical surfaces to correct off-axis aberrations without introducing additional aberrations.

4. The catadioptric telescope optical system with quasi-aluminum characteristics according to claim 1, characterized in that: The distance d ranges from 5 to 10 mm.

5. The method for assembling an optical system according to any one of claims 1 to 4, characterized in that: The interferometer point light source is placed at the focal plane of the system. A part of the spherical light beam emitted by the point light source passes through the correction mirror group, is reflected by the secondary mirror and the primary mirror in sequence, and finally is reflected by the self-collimating plane mirror and returns to the original path to form system interference fringes. A part of the light beam is directly reflected back to the interferometer by the concave surface of the correction mirror D to form reference interference fringes. Since there is a distance d between the focal plane of the system and the conjugate image point, the existence of defocus makes the reference interference fringes present in the shape of concentric rings. By adjusting the tilt and pitch posture of the correction mirror group, the reference interference fringes are located at the center of the interferometer field of view, that is, the center position of the secondary mirror obstruction. At this time, the optical axis of the correction mirror group is coaxial with the optical axes of the primary mirror and the secondary mirror.

6. The adjustment method according to claim 5, characterized in that: When the correcting mirror group contains two or more correcting mirrors, the correcting mirror group is individually adjusted using a centering instrument and then integrated with the primary mirror and secondary mirror system for adjustment.

7. The adjustment method according to claim 5, characterized in that: The steps include: Step 1: The primary and secondary mirror reflection systems are tested and adjusted using an interferometer; Step 2: After the installation and adjustment is completed, the interferometer remains in place, the interferometer point light source is placed at the focal plane of the system, and the correction lens group is preliminarily installed; The spherical wave beam emitted by the interferometer point light source is directly reflected back to the interferometer by the concave surface of the correction mirror D to form reference interference fringes. If the optical axis of the correction mirror group coincides with the optical axis of the interferometer, the returned reference interference fringes are in the center of the interferometer field of view and are concentric rings. Otherwise, adjust the tilt and pitch attitude of the correction mirror group until the returned reference fringes are in the center of the interferometer field of view and are concentric rings. The spherical wave beam emitted by the interferometer point light source passes through the correction mirror group, is reflected by the secondary mirror and the primary mirror in turn, and finally is reflected by the self-collimating plane mirror and returns to the original path to form system interference fringes. The axial distance of the correction mirror group is adjusted to make the system interference fringes straight fringes, while keeping the reference interference fringes in the center of the interferometer field of view; Step 3: Move the interferometer axially until the central reference stripes change from concentric circles to straight stripes. At this time, the interferometer focus should be exactly at the concave sphere center of the corrector D. Measure the distance the interferometer moves axially. If the deviation between this distance and the theoretical distance d between the system focal plane and the conjugate image point is less than the preset value, it means that the corrector assembly is adjusted in place.

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