A folding off-axis three-mirror system alignment device and method

Abstract

The present application relates to the technical field of optical mechanical adjustment, and particularly relates to a folded optical path off-axis three-mirror system adjustment device and method; the folded optical path off-axis three-mirror system adjustment device comprises an interferometer, a theodolite and a compensator mounted on one side of a main mirror incident surface, a first straight edge and a second straight edge are arranged on a bottom plate of the compensator, and the first straight edge and the second straight edge adjacent to each other form a first included angle; a reference structure is connected by the theodolite and a main mirror optical path, and a main mirror optical axis is perpendicular to the first straight edge; three optical axis transmission structures are arranged based on the property of similar triangles; the first optical axis transmission structure makes the flat glass parallel to the first straight edge; the second optical axis transmission structure makes the normal direction of the flat glass coincide with the optical axis of the plane mirror; and the third optical axis transmission structure makes the folding mirror parallel to the second straight edge. The present application obtains the optical axis of the main mirror by using the compensator, and then calibrates the folding mirror through the bottom plate. Then, the adjustment of the misalignment amount is carried out, and the number of misalignment amounts used for adjustment is small.

Description

Technical Field

[0001] This invention relates to the field of optomechanics and optomechanics assembly and adjustment technology, specifically to an assembly and adjustment device and method for a folded optical path off-axis three-mirror system. Background Technology

[0002] Although off-axis three-mirror optical systems possess excellent characteristics such as no central obstruction, no chromatic aberration, and the ability to achieve a large field of view and high resolution, compared to coaxial three-mirror systems, off-axis three-mirror systems effectively eliminate the obstruction of the primary mirror by the secondary mirror and its supporting structure by using an off-axis optical path, thereby significantly improving the system's imaging quality and energy concentration.

[0003] However, the assembly and adjustment of existing off-axis three-mirror systems with folded optical paths presents many challenges. On the one hand, the off-axis layout results in strong coupling relationships between key parameters such as the surface accuracy, off-axis amount, and eccentricity of each mirror. Any misalignment of any mirror will be amplified through the optical path, directly affecting the image quality. On the other hand, the folded optical path causes the optical paths between mirrors to be blocked. Traditional assembly and adjustment methods based on coaxial references make it difficult to directly observe the direction of the optical path, thus failing to achieve precise positioning of the spatial attitude of each mirror.

[0004] Therefore, those skilled in the art urgently need to propose a precise, efficient, and stable assembly and adjustment method for the structural characteristics and assembly and adjustment difficulties of off-axis three-mirror systems with folded optical paths, in order to meet the key technical needs for promoting the engineering application and mass production of such optical systems. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defects existing in the prior art, thereby providing a folded optical path off-axis three-reflection system assembly and adjustment device and method.

[0006] A device for assembling and adjusting an off-axis three-reflector system with a folded optical path, comprising: an interferometer and a theodolite, characterized in that it further comprises: A compensator is installed on one side of the primary mirror incident surface. The compensator's base plate has a first straight edge and a second straight edge, and two adjacent straight edges form a first included angle. The reference structure consists of a theodolite and a primary mirror optical path connected together, with the primary mirror optical axis perpendicular to the edge of the first straight line; The first optical axis transmission structure consists of a theodolite aimed based on the property of similar triangles, a first straight edge, and a plate glass on the base plate, so that the plate glass and the first straight edge are parallel. The second optical axis transmission structure consists of a theodolite based on the property of similar triangles, a flat glass plate, and a plane mirror mounted on the side of the flat glass plate away from the main mirror, so that the normal direction of the flat glass plate and the optical axis of the plane mirror plate coincide. The third optical axis transmission structure consists of a theodolite and a folding mirror aimed based on the properties of similar triangles, and a second straight edge, so that the folding mirror and the second straight edge are parallel.

[0007] Preferably, the compensator consists of a base plate, a flat glass plate, a convex lens, and a concave lens arranged sequentially on the base plate in the direction of the light path incident on the primary mirror.

[0008] A method for assembling and adjusting a folded optical path off-axis three-mirror system, implemented using a folded optical path off-axis three-mirror system assembly and adjustment device, includes the following steps: Establish benchmark: After roughly installing the primary mirror, compensator and theodolite into the preset position on the platform, adjust the theodolite to align it with the optical axis of the primary mirror, and adjust the base plate of the compensator to make the optical axis of the primary mirror perpendicular to the edge of the first straight line; Obtain the optical axis of the primary mirror: Fix the theodolite and adjust the flat glass so that its two ends are on the extended lines of the theodolite and the first straight line edge; install the interferometer to the side of the compensator away from the primary mirror to detect the surface shape of the primary mirror. If the detected value is not up to design, adjust the primary mirror adjustment pad in the primary mirror mount until the surface shape meets the standard, thereby obtaining the optical axis of the primary mirror. Folding mirror installation and adjustment: After removing the interferometer, install the plane mirror in its original position and adjust it so that its two ends are on the extended aiming lines of the theodolite and the two ends of the flat glass; then roughly install the folding mirror to the preset position on the platform and adjust it so that its two ends are on the extended aiming lines of the theodolite and the two ends of the second straight line edge; then use the theodolite to measure the pointing angles of the plane mirror and the folding mirror, convert them into vectors, and calculate the amount of grinding required for the folding mirror adjustment pad in the folding mirror mount using the cosine theorem and perform grinding. The secondary and tertiary mirrors were assembled and adjusted using an interferometer and a sensitivity matrix.

[0009] Preferably, the pointing angles of the plane mirror and the folding mirror are measured using a theodolite and converted into vectors; specifically: The azimuth angle of the plane mirror was obtained based on theodolite measurements. The pitch angle of the plane mirror The orientation angle of the folding mirror The pitch angle of the folding mirror ; Substituting the above measurement results into the coordinate functions x=sinacosb; y=cosa; z=-sinasinb, a coordinate transformation is performed, resulting in two vectors: , ; In the formula, x, y, and z represent the three axes of the coordinate system; a represents the azimuth angle; and b represents the pitch angle. This is the optical axis transformation vector of the plane mirror; This is the optical axis transformation vector for the folding mirror.

[0010] Preferably, the secondary mirror is assembled and adjusted using an interferometer in conjunction with a sensitivity matrix; Among them, the secondary mirror is related to 6 misalignment quantities, namely the distance between the primary mirror and the secondary mirror, the azimuth eccentricity and pitch eccentricity of the secondary mirror, the pitch tilt and azimuth tilt of the secondary mirror, and the distance between the primary mirror and the secondary mirror.

[0011] Preferably, an interferometer is used in conjunction with a sensitivity matrix to assemble and adjust the three mirrors; Among them, the three mirrors are related to four misalignment quantities, namely the three mirrors and the azimuth and pitch eccentricity, and the three mirrors and the pitch and azimuth tilt.

[0012] The technical solution of this invention has the following advantages: This invention utilizes a compensator to obtain the optical axis of the primary mirror, and then calibrates the folding mirror using the compensator base plate. The offset is then adjusted based on the sensitivity matrix. Finally, the attitudes of the secondary and tertiary mirrors are adjusted to complete the system assembly and adjustment. This invention offers advantages such as high assembly and adjustment accuracy, high efficiency, and low cost. Furthermore, the folded optical path improves space utilization, which is of great significance for promoting the engineering application of high-performance off-axis three-mirror optical systems. Attached Figure Description

[0013] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0014] Figure 1 This is a schematic diagram showing the positional relationship between the primary mirror timing interferometer and the compensator of the present invention; Figure 2 This is a schematic diagram of the compensator structure; Figure 3 This is a schematic diagram of the secondary mirror structure; Figure 4 This is a schematic diagram of the secondary mirror structure explosion. Figure 5 This is a schematic diagram of the optical path of an off-axis three-mirror system.

[0015] Explanation of reference numerals in the attached figures: 1-Primary lens; 2-Secondary lens; 21-Secondary lens element; 22-Secondary lens mount; 23-Secondary lens base A; 24-Adjustment pin; 25-Secondary lens base C; 26-Secondary lens adjustment pad A; 27-Secondary lens adjustment pad B; 28-Secondary lens adjustment pad C; 3-Folding mirror; 4-Three-lens; 5-Detector; 6-Compensator; 61-Base plate; 62-Flat glass; 63-Concave lens; 64-Convex lens; 611-First straight edge; 612-Second straight edge; 7-Interferometer; 8- Plane mirror. Detailed Implementation

[0016] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0017] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] Example 1 This embodiment is an assembly and adjustment device suitable for an off-axis three-reflector system with a folding mirror 3; like Figure 5 In this embodiment, the off-axis three-reflector system to be assembled and adjusted needs to be assembled and adjusted as follows: Figure 1 The positional relationship is shown; the light path is as follows: the incident light enters the primary mirror 1, is reflected and enters the secondary mirror 2, the secondary mirror 2 reflects the light into the folding mirror 3, the folding mirror 3 reflects the light into the third mirror 4, and finally the third mirror 4 reflects the light into the detector 5.

[0019] Specifically: This embodiment discloses a folded optical path off-axis three-reflection system assembly and adjustment device, including: an interferometer 7 and a theodolite, and also includes: a compensator 6 installed on one side of the incident surface of the primary mirror 1. The base plate 61 of the compensator 6 is provided with a first straight edge 611 and a second straight edge 612, and the two adjacent straight edges form a first included angle; the first included angle is 45 degrees.

[0020] The reference structure is formed by connecting the theodolite and the optical path of the primary mirror 1, and the optical axis of the primary mirror 1 is perpendicular to the edge 611 of the first straight line; The first optical axis transmission structure consists of a theodolite aimed based on the property of similar triangles, a first straight edge 611, and a flat glass 62 on the base plate 61, so that the flat glass 62 and the first straight edge 611 are parallel. The second optical axis transmission structure consists of a theodolite based on the property of similar triangles, a flat glass 62, and a plane mirror 8 mounted on the side of the flat glass 62 away from the main mirror 1, so that the normal direction of the flat glass 62 and the optical axis of the plane mirror 8 coincide. The third optical axis transmission structure consists of a theodolite aimed based on the properties of similar triangles, a folding mirror 3, and a second straight edge 612, so that the folding mirror 3 and the second straight edge 612 are parallel.

[0021] like Figure 2 As shown in this embodiment, the compensator 6 consists of a base plate 61, a flat glass plate 62, a convex lens 64, and a concave lens 63 arranged sequentially on the base plate 61 in the direction of the incident light to the primary mirror 1. The second straight edge 612 on the base plate 61 forms a fixed angle with the optical axes of the two lenses. The tolerance of this angle is extremely strict. Specifically, there are small protrusions on the mounting surface of the lenses that are suitable for precision machining. These protrusions are used to calibrate the optical axis of the folding mirror and determine that the angle between the optical axis of the folding mirror 3 and the optical axis of the primary mirror 1 is the first included angle.

[0022] It should be noted that the position of the theodolite is not specifically limited and can be adjusted adaptively according to actual application. It is only necessary to ensure that all components are within the theodolite's field of view; therefore, no example of the theodolite position is shown in the attached diagram. Furthermore, if the spacing between components in an off-axis three-reflector system is too large to exceed the field of view of a single theodolite, and one theodolite cannot meet the actual requirements, different theodolites can be used for different optical axis transmission structures. Regarding base plate 61, such as... Figure 2 As shown, the base plate 61 is a fixed structure. However, in practical applications, it is only necessary to satisfy that there are two straight edges that can form a first included angle with a preset angle as required. Therefore, the structure of the base plate 61 is not limited to a fixed structure, and it can also be a telescopic structure or a hinged structure.

[0023] Furthermore, the following is also disclosed in this embodiment: The main mirror 1 is mounted on the main mirror mount, which is fixed to the platform with three screws. The attitude of the main mirror 1 is adjusted between the platform and the main mirror 1 through the main mirror adjustment pad. There are a total of six adjustment points on both sides of the main mirror adjustment pad. The adjustment method is to grind the small boss A to form a dihedral angle to adjust the attitude.

[0024] The folding mirror 3 is mounted on the folding mirror base, which is fixed to the platform with three screws. The folding mirror 3 and the folding mirror base are adjusted in attitude by the folding mirror adjustment pad. There are six small protrusions B on both sides of the folding mirror adjustment pad. The adjustment method is to grind the small protrusions B to form dihedral angles to adjust the attitude.

[0025] For secondary mirror 2: like Figure 3-4 The secondary mirror lens 21 shown is mounted on the secondary mirror mount 22. The secondary mirror mount 22 has a flexible elastic device on its back. The secondary mirror mount 22 is mounted on one side of the secondary mirror base A23. Three adjustment pins 24 are installed on the other side of the secondary mirror base A23 to adjust the posture of the secondary mirror 2.

[0026] The secondary mirror base A23 is installed on the secondary mirror base C25 with two screws. The secondary mirror base C25 has a vertical elongated hole for adjusting the displacement of the secondary mirror 2 in the direction perpendicular to the platform.

[0027] The secondary mirror base C25 is mounted on the secondary mirror adjustment pad A26 by four screws; the secondary mirror base C25 has four circular slots to adjust the rotation of the secondary mirror 2 about a direction perpendicular to the platform.

[0028] Secondary mirror adjustment shim A26 is mounted to secondary mirror adjustment shim B27 by four screws. Secondary mirror adjustment shim A26 has elongated holes and elongated protrusions that fit into the grooves on secondary mirror adjustment shim B27 to adjust the displacement of secondary mirror 2 in the optical axis direction. Secondary mirror adjustment shim B27 is mounted to secondary mirror adjustment shim C28 by two screws. Secondary mirror adjustment shim B27 has elongated holes and elongated protrusions that fit into the grooves on secondary mirror adjustment shim C28 to adjust the radial displacement of secondary mirror 2, which is parallel to the platform. Secondary mirror adjustment shim C28 is mounted on the platform.

[0029] Example 2 Based on Embodiment 1, this embodiment further discloses a method for assembling and adjusting a folded optical path off-axis three-mirror system, which is implemented using a folded optical path off-axis three-mirror system assembly and adjustment device from Embodiment 1; Establishing benchmarks specifically includes: S101. Roughly install the main mirror 1, compensator 6 and the theodolite to the preset positions on the platform; S102. Adjust the theodolite to align with the optical axis of the primary mirror 1, and adjust the position of the compensator 6 base plate 61 until the optical axis of the primary mirror 1 is perpendicular to the edge 611 of the first straight line; Obtain the optical axis of primary mirror 1: S201. Fix the position of the theodolite; adjust the position of the flat glass 62 so that both ends of the flat glass 62 are on the extended aiming lines of the theodolite and the first straight edge 611. like Figure 1 S202. Install the interferometer 7 to the side of the compensator 6 away from the main mirror 1, and use the interferometer 7 to detect the surface shape of the main mirror 1. If the surface shape reaches the design value, the optical axis of the main mirror 1 has been acquired; if the surface shape does not reach the design value, make adaptive adjustments to the adjustment pad in the main mirror mount according to the detection results until the surface shape reaches the design value. Folding Mirror 3-piece Adjustment: S301. Remove interferometer 7 and install plane mirror 8 to the original installation position of interferometer 7; S302. Adjust the position of the plane mirror 8 so that both ends of the plane mirror 8 are on the aiming extension lines of the theodolite and the flat glass 62; S303. Roughly install the folding mirror 3 to the preset position on the platform: Adjust the position of the folding mirror 3 so that both ends of the folding mirror 3 are on the aiming extension line of the theodolite and the second straight line edge 612; S304. Measure the azimuth and elevation angles of the plane mirror 8 using a theodolite; measure the pointing angles of the plane mirror 8 of the folding mirror 3 using a theodolite; further convert the obtained angles into vectors, calculate the amount of shims to be ground in the folding seat according to the cosine theorem, and grind the shims in the folding seat; specifically: the pointing angle includes the azimuth and elevation angles; The azimuth angle of the plane mirror 8 was obtained based on the theodolite measurement. The pitch angle of plane mirror 8 The orientation angle of folding mirror 3 The pitch angle of folding mirror 3 ; Substituting the above measurement results into the coordinate functions x=sinacosb; y=cosa; z=-sinasinb, a coordinate transformation is performed, resulting in two vectors: , ; In the formula, x, y, and z represent the three axes of the coordinate system; a represents the azimuth angle; and b represents the pitch angle. The optical axis transformation vector for the 8-plane mirror; is the optical axis transformation vector for the folding mirror 3.

[0030] The cosine theorem applied in this embodiment is: In the formula The angle between two vectors is used for coarse adjustment. Repair and grind the adjustment pad for the folding mirror.

[0031] Install the interferometer 7 onto the platform, and use the interferometer 7 in conjunction with the sensitivity matrix to adjust the secondary mirror 2 and the tertiary mirror 4; The secondary mirror 2 is roughly mounted on the platform, and the sensitivity matrix is ​​obtained through optical analysis. The sensitivity matrix contains the influence of each misalignment on the optical system. Among them, the secondary mirror 2 has the greatest impact on the optical performance of the entire system, so astigmatism, coma, and spherical aberration of the system are corrected by mounting and adjusting the secondary mirror 2. It should be noted that the sensitivity matrix is ​​obtained using existing technology in this embodiment, so the specific details of the acquisition will not be elaborated further. Among them, secondary mirror 2 is related to 6 misalignment quantities, namely the distance between primary mirror 1 and secondary mirror 2, the azimuth eccentricity and pitch eccentricity of secondary mirror 2, the pitch tilt and azimuth tilt of secondary mirror 2, and the distance between primary mirror 4 and secondary mirror 2.

[0032] Among them, the three mirrors 4 are related to four misalignment quantities, namely the three mirrors 4 and the azimuth eccentricity and pitch eccentricity, and the three mirrors 4 and the pitch tilt and azimuth tilt.

[0033] The offset is adjusted based on the sensitivity matrix, and aberration detection and correction are performed on the assembled system. After assembly and adjustment, wavelet aberrations are measured under different fields of view to bring them to the design value.

[0034] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A device for assembling and adjusting a folded optical path off-axis three-reflector system, comprising: The interferometer (7) and the theodolite are characterized in that they further include: The compensator (6) is installed on one side of the incident surface of the main mirror (1). The base plate (61) of the compensator (6) has a first straight edge (611) and a second straight edge (612), and the two adjacent straight edges form a first included angle. The reference structure is formed by the optical path connection between the theodolite and the main mirror (1), and the optical axis of the main mirror (1) is perpendicular to the edge (611) of the first straight line; The first optical axis transmission structure consists of a theodolite aimed based on the properties of similar triangles, a first straight edge (611), and a flat glass (62) on the base plate (61), so that the flat glass (62) and the first straight edge (611) are parallel; The second optical axis transmission structure consists of a theodolite based on the property of similar triangles, a flat glass (62), and a plane mirror (8) installed on the side of the flat glass (62) away from the main mirror (1) for aiming, so that the normal direction of the flat glass (62) and the optical axis of the plane mirror (8) coincide. The third optical axis transmission structure consists of a theodolite and a folding mirror (3) aimed based on the properties of similar triangles, and a second straight edge (612) to make the folding mirror (3) and the second straight edge (612) parallel.

2. The folding optical path off-axis three-reflector system assembly and adjustment device according to claim 1, characterized in that, The compensator (6) consists of a base plate (61), a flat glass plate (62), a convex lens (64), and a concave lens (63) arranged sequentially on the base plate (61) in the direction of the light path incident on the main mirror (1).

3. A method for assembling and adjusting a folded optical path off-axis three-reflector system, characterized in that, The assembly and adjustment device for the off-axis three-reflector system with a folded optical path as described in claim 2 includes the following steps: Establish benchmark: After roughly installing the main mirror (1), compensator (6) and the theodolite into the preset position on the platform, adjust the theodolite to align with the optical axis of the main mirror (1), and adjust the base plate (61) of the compensator (6) to make the optical axis of the main mirror (1) perpendicular to the edge of the first straight line (611). Obtain the optical axis of the primary mirror (1): Fix the theodolite and adjust the flat glass (62) so that its two ends are on the aiming extension line of the theodolite and the first straight edge (611); install the interferometer (7) to the side of the compensator (6) away from the primary mirror (1) to detect the surface shape of the primary mirror (1). If the detection shows that the design value is not met, adjust the primary mirror adjustment pad in the primary mirror mount until the surface shape meets the standard, thereby obtaining the optical axis of the primary mirror (1); Folding mirror (3) installation and adjustment: After removing the interferometer (7), install the plane mirror (8) in its original position and adjust it so that its two ends are on the aiming extension lines of the theodolite and the flat glass (62); then roughly install the folding mirror (3) to the preset position on the platform and adjust it so that its two ends are on the aiming extension lines of the theodolite and the second straight edge (612); then use the theodolite to measure the pointing angle of the plane mirror (8) and the folding mirror (3), convert it into a vector, and calculate the amount of grinding required for the folding mirror adjustment pad in the folding mirror mount using the cosine theorem and grind it. The secondary mirror (2) and the tertiary mirror (4) are assembled and adjusted using an interferometer (7) in conjunction with a sensitivity matrix.

4. The method for assembling and adjusting a folded optical path off-axis three-reflector system according to claim 1, characterized in that, The pointing angles of the plane mirror (8) and the folding mirror (3) are measured using a theodolite and converted into vectors; specifically: The azimuth angle of the plane mirror (8) was obtained based on the theodolite measurement. The pitch angle of the plane mirror (8) The azimuth angle of the folding mirror (3) The pitch angle of the folding mirror (3) ; Substituting the above measurement results into the coordinate functions x=sinacosb; y=cosa; z=-sinasinb, a coordinate transformation is performed, resulting in two vectors: , ; In the formula, x, y, and z represent the three axes of the coordinate system; a represents the azimuth angle; and b represents the pitch angle. The optical axis transformation vector of the plane mirror (8); The optical axis transformation vector of the folding mirror (3) is given.

5. The method for assembling and adjusting a folded optical path off-axis three-reflector system according to claim 1, characterized in that, The secondary mirror (2) is assembled and adjusted using an interferometer (7) in conjunction with a sensitivity matrix; Among them, the secondary mirror (2) is related to 6 misalignment quantities, namely the distance between the primary mirror (1) and the secondary mirror (2), the azimuth eccentricity and pitch eccentricity of the secondary mirror (2), the pitch tilt and azimuth tilt of the secondary mirror (2), and the distance between the third mirror (4) and the secondary mirror (2).

6. The method for assembling and adjusting a folded optical path off-axis three-reflector system according to claim 1, characterized in that, The three mirrors (4) are assembled and adjusted using an interferometer (7) and a sensitivity matrix; Among them, the three mirrors (4) are related to four misalignment quantities, namely the three mirrors (4) and the azimuth eccentricity and pitch eccentricity, the pitch tilt and azimuth tilt of the three mirrors (4).

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