Adjustment method of large field of view off-axis three-mirror expanding beam optical system

Abstract

The application discloses a kind of big field of view off-axis three-reflection beam expanding optical system's alignment method, when adjusting off-axis three-reflection beam expanding optical system using existing mode, it is solved that there is the problem of long alignment cycle and low alignment precision, the concave off-axis parabolic characteristics of off-axis primary mirror and off-axis three-mirror are used, and it is self-accurate detection using interferometer and self-accurate mirror;The relative position relationship of off-axis primary mirror and off-axis three-mirror can be determined using its focal point;Only need to adjust a specific optical element when adjusting system each time, without adjusting other optical elements simultaneously, greatly reduce the adjustment uncertainty;As can be seen, the alignment method of the application, the adjustment degree of freedom in the alignment process is reduced by half compared with existing experience method, realizes the controllability of off-axis type beam expanding optical system optical path alignment process, improves the alignment efficiency of optical system optical path.

Description

Technical Field

[0001] This invention relates to a method for assembling and adjusting an optical system, specifically to a method for assembling and adjusting a large field-of-view off-axis three-mirror beam expander optical system. Background Technology

[0002] With the widespread application and rapid development of optical technology, the spectral bands of optical systems are gradually evolving from single visible and infrared bands to multi-band combinations. Due to the limitations of transmission glass materials, it is necessary to design a common-aperture reflective beam expander optical system at the front end of the optical system (parallel light incident and parallel light exit) to meet the system's multi-band requirements, including visible light, short-wave infrared, mid-wave infrared, long-wave infrared, and laser. Then, a total internal reflection common-aperture spectral splitting system is designed at the back end to achieve the imaging requirements of different spectral bands.

[0003] Total internal reflection off-axis three-mirror beam expander systems offer advantages such as no central obstruction, high energy efficiency, easy stray light control, and the ability to achieve large field of view and large relative aperture, attracting widespread attention. However, their assembly and adjustment are challenging, relying heavily on the experience of the personnel. During assembly and adjustment, the individual off-axis aspherical mirrors depend primarily on experience. A single mirror requires adjustment of 5 degrees of freedom, and a three-mirror beam expander system requires at least 10 degrees of freedom, with inter-degree-of-freedom coupling relationships between them. Therefore, current adjustment methods result in significant randomness and uncertainty in the adjustment of each mirror's degree of freedom, leading to excessively long assembly and adjustment cycles and low accuracy. Summary of the Invention

[0004] The purpose of this invention is to provide a method for assembling and adjusting a large field-of-view off-axis three-mirror beam expander optical system, in order to solve the technical problems of excessively long assembly and adjustment cycles and low assembly and adjustment accuracy when adjusting an off-axis three-mirror beam expander optical system using existing methods.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for assembling and adjusting a large field-of-view off-axis three-mirror beam expander optical system, the off-axis three-mirror beam expander optical system comprising an off-axis primary mirror, an off-axis secondary mirror, an off-axis third mirror, and an aperture stop arranged sequentially along the optical path; the reflecting surfaces of the off-axis primary mirror and the off-axis third mirror are concave off-axis parabolic surfaces; the reflecting surface of the off-axis secondary mirror is a convex aspherical surface;

[0007] Its special feature is that it includes the following steps:

[0008] Step 1: Establish the system optical axis;

[0009] Set a preset coordinate system XYZ, set a linear guide rail parallel to the Z-axis, set an interferometer with a standard lens on the linear guide rail, and determine the focal motion trajectory of the interferometer as the optical axis of the system.

[0010] Step 2: Installation of the off-axis primary mirror;

[0011] An autocollimating plane mirror with a central hole is set on one side of the interferometer's working end, so that the normal of the autocollimating plane mirror is parallel to the direction of the linear guide rail; an off-axis primary mirror is pre-installed on the side of the autocollimating plane mirror away from the interferometer; the interferometer is translated so that the focal points of the interferometer and the off-axis primary mirror coincide and are located on the optical axis of the system; the off-axis primary mirror is adjusted based on the coordinate system XYZ so that the wavefront error accuracy of the primary mirror detected by the interferometer meets the requirements, and the installation of the off-axis primary mirror is completed.

[0012] Step 3: Installation of off-axis three mirrors;

[0013] Pre-install off-axis three mirrors on the side of the autocollimating plane mirror away from the interferometer. Translate the interferometer so that the distance between the focal point of the interferometer and the focal point of the off-axis primary mirror meets the preset value. Adjust the off-axis three mirrors based on the coordinate system XYZ so that the accuracy of the wavefront error of the three mirrors detected by the interferometer meets the requirements, and complete the installation of the off-axis three mirrors.

[0014] Step 4: Installation of the off-axis secondary mirror;

[0015] Replace the standard lens of the interferometer with a plane lens, move the autocollimating plane mirror upward along the Y-axis, and move the interferometer downward along the Y-axis so that its emitted parallel beam is incident on the off-axis three mirrors. Pre-install the off-axis secondary mirror, and adjust the off-axis secondary mirror based on the coordinate system XYZ so that the accuracy of the interferometer's detection result, i.e., the system wavefront error, meets the requirements.

[0016] Complete the assembly and adjustment of the off-axis three-mirror beam expander optical system.

[0017] Furthermore, step 1 specifically includes:

[0018] 1.1. Preset a straight line as the system optical axis, and establish a coordinate system XYZ with the preset system optical axis as the Z-axis;

[0019] 1.2. Install an interferometer with a standard lens on a linear guide rail, adjust the linear guide rail so that its track is parallel to the Z-axis, move the interferometer along the linear guide rail, and determine the focal motion trajectory of the interferometer as the optical axis of the system.

[0020] Furthermore, step 1.2 specifically includes:

[0021] An interferometer with a standard lens is installed on a linear guide rail. The linear guide rail is adjusted using a theodolite so that its track is parallel to the Z-axis. The interferometer is moved along the linear guide rail, and the trajectory of the interferometer's focal point is determined as the optical axis of the system.

[0022] Furthermore, step 2 specifically includes:

[0023] 2.1 Set a self-collimating plane mirror with a central hole on one side of the interferometer's working end, and make the focal point of the interferometer pass through the central hole. Adjust the normal of the self-collimating plane mirror to be parallel to the track direction of the linear guide rail.

[0024] 2.2. Pre-install an off-axis primary mirror on the side of the autocollimating plane mirror away from the interferometer. The off-axis primary mirror is located on the upper side of the system's optical axis. Translate the interferometer along the linear guide rail and adjust the off-axis primary mirror by translating along the Z-axis, X-axis, and Y-axis so that the focal point of the interferometer coincides with the focal point of the off-axis primary mirror.

[0025] 2.3 Adjust the off-axis primary mirror to rotate and tilt around the X and Y axes so that the outgoing light from the interferometer is reflected by the off-axis primary mirror and becomes parallel light that is perpendicularly incident on the autocollimating plane mirror and returns along the original path;

[0026] 2.4 Obtain the surface shape detection results of the off-axis primary mirror by the interferometer, i.e., the primary mirror wavefront error; if the accuracy of the primary mirror wavefront error does not meet the requirements, return to step 2.3 until the accuracy of the primary mirror wavefront error meets the requirements; the off-axis primary mirror installation is complete.

[0027] Furthermore, step 2.1 specifically includes:

[0028] An autocollimating plane mirror with a central hole is set on one side of the interferometer's working end, and the focal point of the interferometer is made to pass through the central hole. The normal of the autocollimating plane mirror is adjusted to be parallel to the linear guide rail using a theodolite.

[0029] Furthermore, step 3 specifically includes:

[0030] 3.1. Pre-install off-axis three mirrors on the side of the autocollimating plane mirror away from the interferometer. The off-axis three mirrors are located on the lower side of the optical axis of the system. Translate the interferometer along the linear guide rail so that the distance between the interferometer focus and the off-axis primary mirror focus is a preset value. Then, translate and adjust the off-axis three mirrors along the Z-axis, X-axis, and Y-axis so that the focus of the interferometer coincides with the focus of the off-axis three mirrors.

[0031] 3.2 Adjust the off-axis three mirrors to rotate and tilt around the X and Y axes so that the outgoing light of the interferometer becomes parallel light after being reflected by the off-axis three mirrors and is perpendicularly incident on the autocollimating plane mirror and returns along the original path;

[0032] 3.3 Obtain the surface shape detection results of the three off-axis mirrors by the interferometer, i.e., the wavefront error of the three mirrors; if the accuracy of the wavefront error of the three mirrors does not meet the requirements, return to step 3.2 until the accuracy of the wavefront error of the three mirrors meets the requirements; the installation of the three off-axis mirrors is completed.

[0033] Furthermore, step 4 specifically includes:

[0034] 4.1 Replace the standard lens of the interferometer with a plane lens, and the parallel light emitted from it will be parallel to the optical axis of the system. Move the interferometer downward along the Y-axis so that the parallel beam emitted from it is incident on the off-axis three mirrors.

[0035] 4.2. Pre-install an off-axis secondary mirror on the side of the autocollimating plane mirror away from the interferometer, and move the autocollimating plane mirror upward along the Y-axis so that the autocollimating plane mirror is located on the upper side of the system optical axis;

[0036] 4.3 Adjust the off-axis secondary mirror to translate along the Z-axis, X-axis, and Y-axis, and to rotate and tilt around the X-axis and Y-axis, so that the outgoing light of the interferometer is reflected by the off-axis three mirrors, the off-axis secondary mirror, and the off-axis primary mirror in sequence, and becomes parallel light that is perpendicularly incident on the autocollimating plane mirror and returns along the original path, forming the system autocollimation detection result;

[0037] 4.4 Obtain the system autocollimation test result of the interferometer, i.e. the system wavefront error. If the accuracy of the system wavefront error does not meet the requirements, return to step 4.3 until the accuracy of the system wavefront error detected by the interferometer meets the requirements.

[0038] Complete the assembly and adjustment of the off-axis three-mirror beam expander optical system.

[0039] Furthermore, the linear guide is a digital display linear guide.

[0040] The beneficial effects of this invention are:

[0041] The assembly and adjustment method for a large field-of-view off-axis three-mirror beam expander optical system provided by this invention utilizes the concave off-axis parabolic characteristics of the off-axis primary mirror and the three off-axis mirrors, and uses an interferometer and an autocollimating plane mirror for self-collimation detection. The relative positional relationship between the off-axis primary mirror and the three off-axis mirrors can be determined using their focal points. Each time the system is adjusted, only a specific optical element (five degrees of freedom) needs to be adjusted, without simultaneously adjusting other optical elements (five degrees of freedom), which greatly reduces the adjustment uncertainty. Therefore, compared with existing empirical methods, the assembly and adjustment method of this invention reduces the adjustment degrees of freedom in the assembly and adjustment process by half, realizes the controllability of the optical path assembly and adjustment process of the off-axis beam expander optical system, and improves the assembly and adjustment efficiency of the optical path of the optical system. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of a large field-of-view off-axis three-mirror beam expander optical system;

[0043] Figure 2 This is a schematic diagram of the structure corresponding to step 2 of the assembly and adjustment method of a large field-of-view off-axis three-mirror beam expander optical system of the present invention;

[0044] Figure 3 This is a schematic diagram of the structure corresponding to step 3 of the assembly and adjustment method of a large field-of-view off-axis three-mirror beam expander optical system of the present invention;

[0045] Figure 4 This is a schematic diagram of the structure corresponding to step 4 of the assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system of the present invention.

[0046] Icon labels:

[0047] 1-Off-axis primary mirror, 2-Off-axis secondary mirror, 3-Off-axis third mirror, 4-Aperture stop, 5-Interferometer, 6-Linear guide rail, 7-Autocollimating plane mirror. Detailed Implementation

[0048] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and embodiments. 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.

[0049] This invention provides a method for assembling and adjusting a large field-of-view off-axis three-mirror beam expander optical system. Utilizing the characteristic of parallel light incident and exit in an off-axis three-mirror beam expander optical system, and combining this with the design of the off-axis primary mirror and the three off-axis mirrors as concave off-axis parabolic surfaces, the relative positions of the off-axis primary mirror and the three off-axis mirrors can be accurately determined using the autocollimation principle. This reduces the need to simultaneously adjust two optical elements during the assembly and adjustment of the off-axis three-mirror beam expander system to adjusting only one element. This achieves controllability in the optical path assembly and adjustment process of the off-axis optical system and improves work efficiency.

[0050] like Figure 1 As shown, the off-axis three-mirror beam expander optical system to be assembled and adjusted by this method includes an off-axis primary mirror 1, an off-axis secondary mirror 2, an off-axis third mirror 3, and an aperture stop 4 arranged sequentially along the optical path direction; the reflecting surfaces of the off-axis primary mirror 1 and the off-axis third mirror 3 are concave off-axis parabolic surfaces (K is -1); the reflecting surface of the off-axis secondary mirror 2 is a convex aspherical surface (K is -30.989); the off-axis primary mirror 1, the off-axis secondary mirror 2, and the off-axis third mirror 3 are all aspherical mirrors. In this embodiment, the radii of the off-axis primary mirror 1, the off-axis secondary mirror 2, and the off-axis third mirror 3 are 678.91 mm, 263.61 mm, and 483.3 mm, respectively. The distance between the vertex of the off-axis primary mirror and the vertex of the off-axis secondary mirror is 299 mm; the distance between the vertex of the off-axis secondary mirror 2 and the vertex of the off-axis third mirror 3 is 300 mm; and the distance between the off-axis third mirror 3 and the aperture stop 4 is 465 mm. The center of the incident parallel light is shifted upward along the Y-axis relative to the system optical axis by 100 mm, and the center of the outgoing parallel light is shifted downward along the Y-axis relative to the system optical axis by 50 mm. During autocollimation testing, the focal positions of the off-axis primary mirror 1 and the off-axis third mirror 3 are 98.805 mm apart along the Z-axis.

[0051] The assembly and adjustment steps of this method are as follows:

[0052] Step 1: Establish the system optical axis;

[0053] A preset coordinate system XYZ is established, and a linear guide rail 6 parallel to its Z-axis is set. The linear guide rail 6 is a digitally displayed linear guide rail, and its movement is readable. An interferometer 5 with a standard lens is mounted on the linear guide rail 6, and the focal trajectory of the interferometer 5 is determined as the optical axis of the system. Specifically, this includes:

[0054] 1.1. Preset a straight line as the system optical axis, and establish a coordinate system XYZ with the preset system optical axis as the Z-axis. The X-axis and Y-axis are perpendicular to the Z-axis. Set up an interferometer 5 with a standard lens on the linear guide rail 6. Use a theodolite to adjust the linear guide rail 6 so that its track is parallel to the Z-axis. Move the interferometer 5 along the linear guide rail 6 and determine the focal motion trajectory of the interferometer 5 as the system optical axis.

[0055] Step 2: Installation of off-axis primary mirror 1;

[0056] like Figure 2 As shown, an autocollimating plane mirror 7 with a central hole is set on one side of the working end of the interferometer 5, so that the normal of the autocollimating plane mirror 7 is parallel to the linear guide rail 6; an off-axis primary mirror 1 is pre-installed on the side of the autocollimating plane mirror 7 away from the interferometer 5; the interferometer 5 is translated so that the focal points of the interferometer 5 and the off-axis primary mirror 1 coincide and are located on the optical axis of the system; the off-axis primary mirror 1 is adjusted based on the coordinate system XYZ so that the wavefront error accuracy of the primary mirror detected by the interferometer 5 meets the requirements, and the installation of the off-axis primary mirror 1 is completed; specifically including:

[0057] 2.1. Set an autocollimating plane mirror 7 with a central hole on one side of the working end of the interferometer 5, and make the focal point of the interferometer 5 pass through the central hole. Use a theodolite to adjust the normal of the autocollimating plane mirror 7 to be parallel to the linear guide rail 6.

[0058] 2.2. Pre-install an off-axis primary mirror 1 on the side of the autocollimating plane mirror 7 away from the interferometer 5. The off-axis primary mirror 1 is located on the upper side of the optical axis of the system. Translate the interferometer 5 along the linear guide rail 6, and adjust the off-axis primary mirror 1 by translating along the Z-axis, X-axis, and Y-axis so that the focal point of the interferometer 5 coincides with the focal point of the off-axis primary mirror 1.

[0059] 2.3 Adjust the off-axis primary mirror 1 to rotate and tilt around the X and Y axes so that the light emitted from the interferometer 5 is reflected by the off-axis primary mirror 1 and becomes parallel light that is perpendicularly incident on the autocollimating plane mirror 7 and returns along the original path.

[0060] 2.4 Obtain the surface shape detection result of the interferometer 5 on the off-axis primary mirror 1, i.e., the primary mirror wavefront error RMS; if the accuracy of the primary mirror wavefront error RMS does not meet the requirements, return to step 2.3 until the accuracy of the primary mirror wavefront error RMS meets the requirements, i.e., the accuracy of the primary mirror wavefront error RMS is less than 0.025λ (λ=632.8nm is the wavelength of the interferometer 5); the off-axis primary mirror 1 is installed.

[0061] Step 3: Installation of off-axis three mirrors 3;

[0062] like Figure 3 As shown, an off-axis three-mirror system 3 is pre-installed on the side of the autocollimating plane mirror 7 away from the interferometer 5. The interferometer 5 is translated so that the distance between the focal point of the interferometer 5 and the focal point of the off-axis primary mirror 1 meets a preset value. The off-axis three-mirror system 3 is adjusted based on the XYZ coordinate system so that the accuracy of the wavefront error of the three mirrors detected by the interferometer 5 meets the requirements, thus completing the installation of the off-axis three-mirror system 3; specifically including:

[0063] 3.1. Pre-install off-axis three-mirror 3 on the side of the autocollimating plane mirror 7 away from the interferometer 5. The off-axis three-mirror 3 is located on the lower side of the optical axis of the system. Translate the interferometer 5 along the linear guide rail 6 so that the distance between the focal point of the interferometer 5 and the focal point of the off-axis primary mirror 1 is 98.805mm. Then, translate and adjust the off-axis three-mirror 3 along the Z-axis, X-axis, and Y-axis so that the focal point of the interferometer 5 coincides with the focal point of the off-axis three-mirror 3.

[0064] 3.2 Adjust the off-axis three mirrors 3 to rotate and tilt around the X and Y axes so that the light emitted from the interferometer 5 becomes parallel light after being reflected by the off-axis three mirrors 3 and is perpendicularly incident on the autocollimating plane mirror 7 and returns along the original path.

[0065] 3.3 Obtain the surface shape detection results of the interferometer 5 on the off-axis three mirrors 3, i.e., the wavefront error of the three mirrors; if the accuracy of the wavefront error of the three mirrors does not meet the requirements, return to step 3.2 until the accuracy of the wavefront error of the three mirrors meets the requirements, i.e., the accuracy of the wavefront error of the three mirrors is less than 0.025λ; at this time, the relative position relationship between the off-axis primary mirror 1 and the off-axis three mirrors 3 is adjusted.

[0066] Step 4: Installation of off-axis secondary mirror 2;

[0067] like Figure 4 As shown, the standard lens of interferometer 5 is replaced with a plane lens, the autocollimating plane mirror 7 is moved upward along the Y-axis, and the interferometer 5 is moved downward along the Y-axis so that its emitted parallel beam is incident on the off-axis three-mirror 3. The off-axis secondary mirror 2 is pre-installed, and the off-axis secondary mirror 2 is adjusted based on the coordinate system XYZ so that the accuracy of the detection result of interferometer 5 at this time, i.e., the wavefront error of the system, meets the requirements; specifically including:

[0068] 4.1 Replace the standard lens of interferometer 5 with a plane lens, and the parallel light emitted from it will be parallel to the optical axis of the system. Move interferometer 5 downward along the Y-axis by 50mm so that the parallel beam emitted from it is incident on the off-axis three mirrors 3.

[0069] 4.2. Pre-install the off-axis secondary mirror 2 on the side of the autocollimating plane mirror 7 away from the interferometer 5, and move the autocollimating plane mirror 7 upward along the Y-axis so that the autocollimating plane mirror 7 is located on the upper side of the system optical axis.

[0070] 4.3 Adjust the off-axis secondary mirror 2 to translate along the Z-axis, X-axis, and Y-axis and rotate and tilt around the X-axis and Y-axis so that the outgoing light from the interferometer 5 is reflected sequentially by the off-axis three mirrors 3, the off-axis secondary mirror 2, and the off-axis primary mirror 1, and becomes parallel light that is perpendicularly incident on the autocollimating plane mirror 7 and returns along the original path, forming the system autocollimation detection result;

[0071] 4.4 Obtain the system autocollimation test result of interferometer 5, i.e., the system wavefront error. If the accuracy of the system wavefront error does not meet the requirements, return to step 4.3 until the accuracy of the system wavefront error detected by interferometer 5 meets the requirements, i.e., the accuracy of the system wavefront error is less than 0.08λ.

[0072] The off-axis three-mirror beam expander optical system has been assembled and adjusted.

[0073] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed in the present invention should be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for assembling and adjusting a large field-of-view off-axis three-mirror beam expander optical system, wherein the off-axis three-mirror beam expander optical system comprises an off-axis primary mirror (1), an off-axis secondary mirror (2), an off-axis third mirror (3), and an aperture stop (4) arranged sequentially along the optical path; the reflecting surfaces of the off-axis primary mirror (1) and the off-axis third mirror (3) are concave off-axis parabolic surfaces; the reflecting surface of the off-axis secondary mirror (2) is a convex aspherical surface; Its features are, Includes the following steps: Step 1: Establish the system optical axis; The coordinate system is XYZ. A linear guide rail (6) parallel to the Z-axis is set. An interferometer (5) with a standard lens is installed on the linear guide rail (6). The focal motion trajectory of the interferometer (5) is determined to be the optical axis of the system. Step 2, Installation of the off-axis primary mirror (1); An autocollimating plane mirror (7) with a central hole is set on one side of the working end of the interferometer (5), so that the normal of the autocollimating plane mirror (7) is parallel to the direction of the linear guide rail (6); an off-axis primary mirror (1) is pre-installed on the side of the autocollimating plane mirror (7) away from the interferometer (5), the interferometer (5) is translated so that the focal points of the interferometer (5) and the off-axis primary mirror (1) coincide and are located on the optical axis of the system, and the off-axis primary mirror (1) is adjusted based on the coordinate system XYZ so that the wavefront error accuracy of the primary mirror detected by the interferometer (5) meets the requirements, and the installation of the off-axis primary mirror (1) is completed; Step 3: Installation of off-axis three mirrors (3); Off-axis three mirrors (3) are pre-installed on the side of the autocollimating plane mirror (7) away from the interferometer (5). The interferometer (5) is translated so that the distance between the focal point of the interferometer (5) and the focal point of the off-axis primary mirror (1) meets the preset value. The off-axis three mirrors (3) are adjusted based on the coordinate system XYZ so that the accuracy of the wavefront error of the three mirrors detected by the interferometer (5) meets the requirements. The installation of the off-axis three mirrors (3) is completed. Step 4: Installation of the off-axis secondary mirror (2); Replace the standard lens of the interferometer (5) with a plane lens, move the autocollimating plane mirror (7) upward along the Y-axis, and move the interferometer (5) downward along the Y-axis so that the parallel beam emitted from it is incident on the off-axis three mirrors (3), pre-install the off-axis secondary mirror (2), and adjust the off-axis secondary mirror (2) based on the coordinate system XYZ so that the detection result of the interferometer (5) at this time, i.e. the accuracy of the system wavefront error, meets the requirements; Complete the assembly and adjustment of the off-axis three-mirror beam expander optical system.

2. The assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system according to claim 1, characterized in that, Step 1 specifically includes: 1.

1. Preset a straight line as the system optical axis, and establish a coordinate system XYZ with the preset system optical axis as the Z-axis; 1.

2. Install an interferometer (5) with a standard lens on a linear guide rail (6), adjust the linear guide rail (6) so that its track is parallel to the Z-axis, move the interferometer (5) along the linear guide rail (6), and determine the focal motion trajectory of the interferometer (5) as the optical axis of the system.

3. The assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system according to claim 2, characterized in that, Step 1.2 specifically involves: An interferometer (5) with a standard lens is installed on a linear guide rail (6). The linear guide rail (6) is adjusted using a theodolite so that its track is parallel to the Z-axis. The interferometer (5) is moved along the linear guide rail (6) to determine the focal motion trajectory of the interferometer (5) as the optical axis of the system.

4. The assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system according to claim 1, 2, or 3, characterized in that, Step 2 specifically includes: 2.1 Set a self-collimating plane mirror (7) with a central hole on one side of the working end of the interferometer (5), and make the focal point of the interferometer (5) pass through the central hole. Adjust the normal of the self-collimating plane mirror (7) to be parallel to the track direction of the linear guide rail (6). 2.

2. Pre-install an off-axis primary mirror (1) on the side of the autocollimating plane mirror (7) away from the interferometer (5). The off-axis primary mirror (1) is located on the upper side of the optical axis of the system. Translate the interferometer (5) along the linear guide rail (6) and adjust the off-axis primary mirror (1) along the Z-axis, X-axis and Y-axis so that the focal point of the interferometer (5) coincides with the focal point of the off-axis primary mirror (1). 2.3 Adjust the off-axis primary mirror (1) to rotate and tilt around the X-axis and Y-axis so that the outgoing light of the interferometer (5) becomes parallel light after being reflected by the off-axis primary mirror (1) and is perpendicularly incident on the autocollimating plane mirror (7) and returns along the original path; 2.4 Obtain the surface shape detection result of the interferometer (5) on the off-axis primary mirror (1), i.e., the primary mirror wavefront error; if the accuracy of the primary mirror wavefront error does not meet the requirements, return to step 2.3 until the accuracy of the primary mirror wavefront error meets the requirements; the off-axis primary mirror (1) is installed.

5. The assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system according to claim 4, characterized in that, Step 2.1 specifically involves: An autocollimating plane mirror (7) with a central hole is set on one side of the working end of the interferometer (5), and the focal point of the interferometer (5) is made to pass through the central hole. The normal of the autocollimating plane mirror (7) is adjusted to be parallel to the linear guide rail (6) using a theodolite.

6. The assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system according to claim 5, characterized in that, Step 3 specifically includes: 3.

1. Pre-install an off-axis three-mirror (3) on the side of the autocollimating plane mirror (7) away from the interferometer (5). The off-axis three-mirror (3) is located on the lower side of the optical axis of the system. Translate the interferometer (5) along the linear guide rail (6) so that the distance between the focal point of the interferometer (5) and the focal point of the off-axis primary mirror (1) is a preset value. Then, translate and adjust the off-axis three-mirror (3) along the Z-axis, X-axis, and Y-axis so that the focal point of the interferometer (5) coincides with the focal point of the off-axis three-mirror (3). 3.2 Adjust the off-axis three mirrors (3) to rotate and tilt around the X-axis and Y-axis so that the outgoing light of the interferometer (5) becomes parallel light after being reflected by the off-axis three mirrors (3) and is perpendicularly incident on the autocollimating plane mirror (7) and returns along the original path; 3.3 Obtain the surface shape detection results of the interferometer (5) on the off-axis three mirrors (3), i.e., the wavefront error of the three mirrors; if the accuracy of the wavefront error of the three mirrors does not meet the requirements, return to step 3.2 until the accuracy of the wavefront error of the three mirrors meets the requirements; the off-axis three mirrors (3) are installed.

7. The assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system according to claim 6, characterized in that, Step 4 specifically includes: 4.1 Replace the standard lens of the interferometer (5) with a plane lens, and the parallel light emitted from it will be parallel to the optical axis of the system. Move the interferometer (5) downward along the Y axis so that the parallel beam emitted from it is incident on the off-axis three mirrors (3). 4.

2. Pre-install an off-axis secondary mirror (2) on the side of the autocollimating plane mirror (7) away from the interferometer (5), and move the autocollimating plane mirror (7) upward along the Y-axis so that the autocollimating plane mirror (7) is located on the upper side of the optical axis of the system. 4.3 Adjust the off-axis secondary mirror (2) to translate along the Z-axis, X-axis, and Y-axis and rotate and tilt around the X-axis and Y-axis so that the outgoing light of the interferometer (5) is reflected by the off-axis three mirrors (3), the off-axis secondary mirror (2), and the off-axis primary mirror (1) in sequence, and becomes parallel light that is perpendicularly incident on the autocollimating plane mirror (7) and returns along the original path to form the system autocollimation detection result; 4.4 Obtain the system autocollimation detection result of the interferometer (5), i.e. the system wavefront error. If the accuracy of the system wavefront error does not meet the requirements, return to step 4.3 until the accuracy of the system wavefront error detected by the interferometer (5) meets the requirements. Complete the assembly and adjustment of the off-axis three-mirror beam expander optical system.

8. The assembly and adjustment method of the large field-of-view off-axis three-mirror beam expander optical system according to claim 7, characterized in that: The linear guide (6) is a digital display linear guide.

Images