A wide-field, high-resolution three-mirror imaging system for microdroplet enzyme observation

Abstract

This application discloses a large field-of-view, high-resolution three-mirror imaging system for microdroplet enzyme observation. The system includes three off-axis mirrors: a first mirror, a second mirror, and a third mirror. The first mirror is a concave extended polynomial freeform surface, the second mirror is a convex extended polynomial freeform surface, and the third mirror is a concave extended polynomial freeform surface. The conjugate distance between the object plane of the sample and the image plane of the detector is finite. This solves the problem in related three-mirror imaging systems where imaging resolution and field of view cannot be simultaneously satisfied.

Description

Technical Field

[0001] This application relates to the field of optical imaging, and more specifically, to a large field-of-view, high-resolution three-mirror imaging system for observing microdroplet enzymes. Background Technology

[0002] Breakthroughs and developments in industrial microbial enzyme preparations and strains—the "chips" of biomanufacturing—are central to achieving green biomanufacturing, and the extreme optimization of industrial strains and enzymes using directed evolution technology is a crucial means to achieve this goal. Given limited initial information, a larger mutant library increases the probability of obtaining superior mutants. Randomly introducing three mutation sites into a protein composed of 200 amino acids can generate 9 billion (9 × 10⁻⁶) mutants. 9 There are 10 different mutants. Conventional screening methods typically only screen libraries with a capacity of 10. 3 -10 5 These only represent a small fraction of the mutant library's capacity. Therefore, high-throughput screening to identify superior mutants from a massive pool is crucial for achieving breakthroughs in bio-manufacturing "chips."

[0003] However, screening using imaging methods requires not only micrometer-level resolution but also a field of view on the order of tens of centimeters. Therefore, to achieve 5×10... 6 To simultaneously observe multiple microdroplets of enzyme, achieving a resolution better than 1.5 μm is required for observing their morphology. Furthermore, assuming each microdroplet is 20 μm in size when laid flat on the slide, the slide size needs to be 45 mm × 10 mm to accommodate 5 × 10 microdroplets. 6 Each microdroplet enzyme has ample room for growth.

[0004] There is a wide-spectrum, large numerical aperture, ultra-high throughput microscope objective optical system in the prior art. Although the resolution is far better than 1.5μm, the field of view of a single imaging line is only 2.8mm, which is far less than the required field of view.

[0005] There is also an off-axis three-mirror imaging system based on a freeform surface. The focal length of this system is only 120mm, the field of view is only 2°×2°, and the system is based on the infinite conjugate distance of the incident light rays being parallel light. That is, it cannot directly image and requires a separate focusing imaging system, which does not meet the requirements of high-throughput screening technology.

[0006] There is currently no effective solution to the problem that three-mirror imaging systems in related technologies cannot simultaneously achieve both imaging resolution and field of view, making it difficult to meet the requirements at the same time. Summary of the Invention

[0007] The main objective of this application is to provide a large field-of-view, high-resolution three-mirror imaging system for microdroplet enzyme observation, in order to solve the problem that the imaging resolution and field of view of the three-mirror imaging system in the related technology cannot be simultaneously satisfied.

[0008] To achieve the above objectives, according to one aspect of this application, a large field-of-view, high-resolution three-mirror imaging system for microdroplet enzyme observation is provided, comprising: three off-axis mirrors, the three mirrors including a first mirror, a second mirror, and a third mirror; the first mirror reflects incident light from the sample surface to the second mirror, the second mirror reflects light reflected from the first mirror to the third mirror, and the third mirror reflects light reflected from the second mirror to a detector for imaging; the first mirror is a concave extended polynomial freeform surface, the second mirror is a convex extended polynomial freeform surface, and the third mirror is a concave extended polynomial freeform surface; the distance between the center of the sample surface and the center of the first mirror is a first preset value. Let distances be defined as follows: the distance between the center of the first reflector and the center of the second reflector is a second preset distance; wherein, the first preset distance is greater than the second preset distance; the distance between the center of the second reflector and the center of the third reflector is a third preset distance; the distance from the center of the third reflector to the center of the detector plane is a fourth preset distance; wherein, the fourth preset distance is greater than the third preset distance; the distance between the lowermost ray of the incident light on the sample surface and the upper edge of the second reflector is greater than a fifth preset distance; the distance between the uppermost ray of the reflected light from the third reflector and the lower edge of the second reflector is greater than a sixth preset distance; wherein, the fifth preset distance is less than the sixth preset distance; the conjugate distance between the object plane of the sample surface and the image plane of the detector is finite.

[0009] Optionally, the first preset distance is 421.733 mm with an error of ±1%; the second preset distance is 276.183 mm with an error of ±1%; the third preset distance is 141.046 mm with an error of ±1%; the fourth preset distance is 475.306 mm with an error of ±1%; the fifth preset distance is 15 mm with an error of ±1%; and the sixth preset distance is 35 mm with an error of ±1%.

[0010] Optionally, the first reflector has a radius of curvature of -442.400 mm with an error of ±1% and a quadratic surface coefficient of -0.0840 with an error of ±0.5%; the second reflector has a radius of curvature of -316.613 mm with an error of ±1% and a quadratic surface coefficient of -2.2702 with an error of ±0.5%; and the third reflector has a radius of curvature of -809.019 mm with an error of ±1% and a quadratic surface coefficient of 11.4828 with an error of ±0.5%.

[0011] Optionally, the minimum aperture size of the sample surface has an X half-width of 45 mm and a Y half-width of 10 mm; the minimum aperture size of the first reflector has an X half-width of 120 mm and a Y half-width of 100 mm; the minimum aperture size of the second reflector has an X half-width of 47 mm and a Y half-width of 47 mm; the minimum aperture size of the third reflector has an X half-width of 62 mm and a Y half-width of 62 mm; and the minimum aperture size of the detector has an X half-width of 90 mm and a Y half-width of 20 mm.

[0012] Optionally, the first reflector is tilted 22.803°±0.1° in the positive X direction and 107.365±0.05mm off-center in the negative Y direction, with the center of the sample surface as the reference; the second reflector is tilted 18.435°±0.1° in the positive X direction and -87.578±0.05mm off-center in the negative Y direction, with the center of the sample surface as the reference; and the third reflector is tilted 18.891°±0.1° in the positive X direction and 0±0.05mm off-center in the negative Y direction, with the center of the sample surface as the reference.

[0013] Optionally, the first, second, and third reflectors are all obtained by offsetting multi-row, multi-column reflective units based on a reference sphere or plane using an extended polynomial of a freeform surface; the reflective unit has N rows and N columns, totaling N... 2 indivual.

[0014] Optionally, N=7, and the number of offset reflection units is 32; the 32 offset reflection units of the first reflector and their offset values ​​are as follows: X1Y0: -0.760930, X0Y1: 13.153348, X2Y0: 13.635789, X1Y1: 1.367431, X0Y2: -3.791197, X3Y0: 0.216658, X2Y1: 7.884740, X1Y2: -1.284617, 60, X1Y3: 0.422374, X0Y4: 5.331834, X5Y0: -0.007190, -1.091812, X6Y0: 2.242588, X5Y1: -0.006009, X4Y2: 5.936232, X3Y3: 0.230368, X2Y4: 6.044876, X1Y5: 0.183219, X0Y6: 2.725690, X7Y0: 0.353704, X6Y1: -0.457662, X5Y2: 0.420403, X4Y3: -0.291715, X3Y4: 0.717853; The 32 offset reflection elements of the second reflector and their offset values ​​are as follows: X1Y0: -0.39 4811, X0Y1: -2.651220, X2Y0: -3.058057, X1Y1: 1.041852, Y3: -1.874196, X4Y0: -1.580678, X3Y1: 0.111114, X2Y2: -2.754367, X1Y3: 0.081516, 4054, X3Y2: -0.164886, X2Y3: 0.350123, X1Y4: -0.070959, 3Y3: 0.111716, X2Y4: -0.133963, X1Y5: -0.010376, X0Y6: -0.043601, X7Y0: -0.094356,616155, X3Y4: -0.128676; The 32 offset reflection units of the third reflector and their offsets are as follows: X1Y0: -0.824707, X0Y1: 14.399089, X2Y0: -4.746276, X1Y1: 1.711498, X0Y2: 8.129082, X3Y0: -0.054 087, X2Y1: 7.672633, X1Y2: -0.142714, X0Y3: 2.8415552, 1: 1.070612, X2Y2: 4.186820, X1Y3: -0.720680, X0Y4: 0.441362, X5Y0: 0.179992 , X4Y1: 6.356381, X3Y2: -1.168841, X2Y3: -5.641012, X1Y4: 0.750136, .305958, X6Y0: -1.634471, X5Y1: -0.353238, X4Y2: -6.016485, X2Y4: 4.328049, X1Y5: -0.263217, X0Y6: 0.623647, X7Y0: 0.078872, X6Y1: 0.356265, X5Y2: 0.497625, X4Y3: 3.332386, X3Y4: -0.186826; the offset error of the reflective unit is ±1%.

[0015] To achieve the above objectives, according to another aspect of this application, a method for determining a large field-of-view, high-resolution three-mirror imaging system for microdroplet enzyme observation is provided, comprising: determining the imaging magnification and aberrations of the three-mirror imaging system for a sample surface of a preset size according to imaging requirements; determining the position information of a first initial mirror, a second initial mirror, and a third initial mirror of the three-mirror imaging system according to the imaging magnification, wherein the first initial mirror is a concave spherical surface used to reflect incident light rays from the sample surface into parallel light, the second initial mirror is a plane, and the third initial mirror is a plane; and iteratively determining the surface shapes of the first initial mirror, the second initial mirror, and the third initial mirror using a freeform surface extended polynomial based on the aberrations of the image formed by the outgoing light rays reflected by the third initial mirror, thereby obtaining the first mirror, the second mirror, and the third mirror, such that the aberrations of the outgoing light rays from the third mirror meet the imaging requirements.

[0016] Optionally, determining the position information of the first, second, and third initial mirrors of the three-mirror imaging system based on the imaging magnification includes: selecting an initial position, initial angle, and initial distance according to the off-axis principle, and setting the first, second, and third initial mirrors; adjusting the first initial mirror so that the light output from the first initial mirror is closest to parallel light, and the imaging magnification of the light emitted from the third initial mirror meets the imaging magnification requirement.

[0017] Optionally, based on the aberration of the image formed by the outgoing light reflected by the third initial mirror, the surface shapes of the first, second, and third initial mirrors are iteratively determined using a freeform surface extended polynomial to obtain the first, second, and third mirrors. This includes: determining the aberration of the image formed by the outgoing light reflected by the third initial mirror; and iteratively adjusting the surface units on the first, second, and third initial mirrors according to the surface shape elevation expression of the freeform surface extended polynomial until all aberrations meet the imaging requirements, thereby obtaining the first, second, and third mirrors.

[0018] This application utilizes three off-axis reflectors: a first reflector, a second reflector, and a third reflector. The first reflector reflects incident light from the sample surface to the second reflector; the second reflector reflects the reflected light from the first reflector to the third reflector; and the third reflector reflects the reflected light from the second reflector to a detector used for imaging. The first reflector is a concave extended polynomial freeform surface, the second reflector is a convex extended polynomial freeform surface, and the third reflector is a concave extended polynomial freeform surface. The distance between the center of the sample surface and the center of the first reflector is a first preset distance. The distance between the center of the first reflector and the center of the second reflector is... The distance between the centers is a second preset distance; wherein, the first preset distance is greater than the second preset distance; the distance between the center of the second reflector and the center of the third reflector is a third preset distance; the distance from the center of the third reflector to the center of the detector plane is a fourth preset distance; wherein, the fourth preset distance is greater than the third preset distance; the distance between the lowest incident ray of the sample surface and the upper edge of the second reflector is greater than the fifth preset distance; the distance between the highest reflected ray of the third reflector and the lower edge of the second reflector is greater than the sixth preset distance; wherein, the fifth preset distance is less than the sixth preset distance; the conjugate distance between the object plane of the sample surface and the image plane of the detector is finite.

[0019] An off-axis three-mirror imaging system based on a freeform surface with finite conjugate distance was developed. While ensuring a compact positional structure, it achieved imaging of an ultra-large field of view of tens of centimeters, and ensured imaging resolution at the micrometer level. This achieved the technical effect of high imaging resolution and a large object-side field of view, thus solving the problem in related three-mirror imaging systems where imaging resolution and field of view could not be simultaneously satisfied. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a schematic diagram of a large field-of-view, high-resolution three-mirror imaging system for microdroplet enzyme observation provided in an embodiment of this application;

[0022] Figure 2 This is a dot diagram of a three-view imaging system provided according to an embodiment of this application;

[0023] Figure 3 This is a full-field transfer function curve of the three-reflector imaging system provided according to the embodiments of this application at a cutoff frequency of 100 lp / mm;

[0024] Figure 4 This is a full-field transfer function curve of the three-reflector imaging system provided according to the embodiments of this application at a cutoff frequency of 330 lp / mm;

[0025] Figure 5 This is a field curvature distortion diagram of a three-reflection imaging system provided according to an embodiment of this application;

[0026] Figure 6 This is a flowchart of a method for determining a large field-of-view, high-resolution three-reflection imaging system for microdroplet enzyme observation, according to an embodiment of this application. Detailed Implementation

[0027] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

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

[0029] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate for the embodiments of this application described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0030] The present invention will now be described in conjunction with preferred embodiments. Figure 1 This is a schematic diagram of a large field-of-view, high-resolution three-mirror imaging system for microdroplet enzyme observation provided in an embodiment of this application, as shown below. Figure 1 As shown, the three-mirror imaging system includes three off-axis mirrors, namely a first mirror, a second mirror, and a third mirror.

[0031] The first reflecting mirror M1 is used to reflect the light incident on the sample surface W1 to the second reflecting mirror M2. The second reflecting mirror M2 is used to reflect the light reflected by the first reflecting mirror M1 to the third reflecting mirror M3. The third reflecting mirror M3 is used to reflect the light reflected by the second reflecting mirror M2 to the detector D1 used for imaging.

[0032] The first mirror M1 is a concave extended polynomial freeform surface, the second mirror M2 is a convex extended polynomial freeform surface, and the third mirror M3 is a concave extended polynomial freeform surface.

[0033] The distance between the center of sample surface W1 and the center of the first reflecting mirror M1 is a first preset distance; the distance between the center of the first reflecting mirror M1 and the center of the second reflecting mirror M2 is a second preset distance; wherein, the first preset distance is greater than the second preset distance;

[0034] The distance between the center of the second reflector M2 and the center of the third reflector M3 is the third preset distance; the distance from the center of the third reflector M3 to the center of the detector D1 plane is the fourth preset distance; wherein, the fourth preset distance is greater than the third preset distance;

[0035] The distance between the lowest incident ray of the sample surface W1 and the upper edge of the second reflector M2 is greater than the fifth preset distance; the distance between the highest reflected ray of the third reflector M3 and the lower edge of the second reflector M2 is greater than the sixth preset distance, wherein the fifth preset distance is less than the sixth preset distance;

[0036] The conjugate distance between the object plane of the sample and the image plane of the detector is finite.

[0037] The above structure, using three freeform surface mirrors, forms an off-axis three-mirror imaging system with finite conjugate distances based on freeform surface shapes. While maintaining a compact structural configuration, it achieves high resolution for microdroplet enzyme observation, including systems with up to 10... 5 -10 7 Imaging of microdroplets of enzyme at a scale of tens of centimeters with an ultra-large field of view while maintaining imaging resolution at the micrometer level achieves both high imaging resolution and a large object-side field of view. This solves the problem in related technologies where three-view imaging systems cannot simultaneously meet the requirements for imaging resolution and field of view.

[0038] This embodiment aims to achieve 5×10 6 To simultaneously observe multiple microdroplets of enzyme, achieving a resolution better than 1.5 μm is required for observing their morphology. Furthermore, assuming each microdroplet is 20 μm in size when laid flat on the slide, the slide size needs to be 45 mm × 10 mm to accommodate 5 × 10 microdroplets. 6 Each microdroplet enzyme has ample growth space. The sample surface described above can include 5 × 10⁶ samples. 6 The slide containing the microdroplet enzyme, or a planar transparent slide used to transmit light from all the microdroplet enzymes on the slide into the three-reflection system.

[0039] like Figure 1 As shown, light rays from the object side of the sample surface must pass through the three-mirror system, which conforms to the first to sixth preset distances, to form an image according to the correct optical path. Although the first, second, and third mirrors are all freeform surfaces, they are also freeform surfaces obtained by adjusting a plane or a reference sphere. Specifically, the first and third mirrors are freeform surfaces obtained by adjusting a reference sphere, while the second mirror is a freeform surface obtained by adjusting a plane.

[0040] The first reflecting mirror is concave, which reflects and adjusts the divergent incident light rays from the sample surface, which have a large field of view, into near-parallel light, thus uniformly dispersing the light rays from the sample surface for subsequent refraction and higher resolution imaging. The second reflecting mirror is convex, which refracts the near-parallel light emitted from the first reflecting mirror as completely as possible to the third reflecting mirror, avoiding interference and crossing of light rays during refraction to ensure high imaging resolution. The third reflecting mirror is used to focus the light rays reflected from the second reflecting mirror, obtaining an image with a finite conjugate distance through the detector.

[0041] This allows the three-mirror imaging system to achieve imaging of an ultra-large field of view of tens of centimeters while maintaining a compact positional structure, and to ensure imaging resolution at the micrometer level. It achieves the technical effect of high imaging resolution and a large object-side field of view, thus solving the problem in related technologies where three-mirror imaging systems cannot simultaneously meet the requirements for imaging resolution and field of view.

[0042] Optionally, the first preset distance is 421.733mm with an error of ±1%; the second preset distance is 276.183mm with an error of ±1%; the third preset distance is 141.046mm with an error of ±1%; the fourth preset distance is 475.306mm with an error of ±1%; the fifth preset distance is 15mm with an error of ±1%; and the sixth preset distance is 35mm with an error of ±1%.

[0043] By using the first and sixth preset distances mentioned above, the compact structure of the three-mirror system is ensured on the one hand, and the large object-side field of view and high-resolution, robust imaging properties are ensured on the other hand.

[0044] Preferably, the first preset distance is 421.733mm; the second preset distance is 276.183mm; the third preset distance is 141.046mm; the fourth preset distance is 475.306mm; the fifth preset distance is 15mm; and the sixth preset distance is 35mm.

[0045] Optionally, the radius of curvature of the first reflector is -442.400 mm with an error of ±1%, and the quadratic surface coefficient is -0.0840 with an error of ±0.5%; the radius of curvature of the second reflector is -316.613 mm with an error of ±1%, and the quadratic surface coefficient is -2.2702 with an error of ±0.5%; the radius of curvature of the third reflector is -809.019 mm with an error of ±1%, and the quadratic surface coefficient is 11.4828 with an error of ±0.5%.

[0046] The first, second, and third reflecting mirrors mentioned above are all freeform surfaces. For a freeform surface, its radius of curvature can describe the degree of curvature of the surface as a whole. The larger the radius of curvature, the closer the surface is to a plane; the smaller the radius of curvature, the more curved the surface is.

[0047] The quadratic surface coefficients are used when determining a freeform surface based on an extended freeform surface polynomial. For example, the first, second, and third reflectors are all designed using an extended freeform surface polynomial, and their corresponding surface profile elevation expressions are:

[0048]

[0049] In the formula The radius and height are along the optical axis; the first term on the right side of the equation is the equation of a conic section. Let be the curvature at the vertex of the curve. These are the coefficients for the conic surface, which are also the coefficients for the quadratic surface mentioned above; the second term on the right side of the equation is the surface portion described by a polynomial. The total number of polynomial coefficients in the series. For the first The coefficients of the extended polynomial, which is only in , A power series in a direction. The first term is... Then Next is , , And so on. There are 2 terms of degree 1, 3 terms of degree 2, 4 terms of degree 3, and so on. The highest degree is 20, which makes the maximum total number of aspherical coefficients of the polynomial 230. and The data values ​​at each position are divided by a normalized radius to obtain a dimensionless polynomial coefficient. It represents a coordinate function that includes X and y. It can be understood as a plane formed by x and y in a plane perpendicular to the sag direction, with x and y as coordinates.

[0050] The preferred first reflector has a radius of curvature of -442.400 mm and a quadratic surface coefficient of -0.0840; the second reflector has a radius of curvature of -316.613 mm and a quadratic surface coefficient of -2.2702; and the third reflector has a radius of curvature of -809.019 mm and a quadratic surface coefficient of 11.4828.

[0051] Optionally, the minimum aperture size of the sample surface has an X half-width of 45mm with an error of +5mm and a Y half-width of 10mm with an error of +5mm; the minimum aperture size of the first reflector has an X half-width of 120mm with an error of +10mm and a Y half-width of 100mm with an error of +10mm; the minimum aperture size of the second reflector has an X half-width of 47mm with an error of +5mm and a Y half-width of 47mm with an error of +5mm; the minimum aperture size of the third reflector has an X half-width of 62mm with an error of +7mm and a Y half-width of 62mm with an error of +7mm; and the minimum aperture size of the detector has an X half-width of 90mm with an error of +5mm and a Y half-width of 20mm with an error of +5mm.

[0052] The aperture size described above determines the effective range of light that the mirror can reflect, and is directly proportional to the actual size of the mirror; the larger the aperture size, the larger the actual size of the mirror needs to be. The aperture size of the sample surface and the aperture size of the detector are used to describe this. The sample surface can generate incident light within the aperture size, and the detector can receive light within the aperture size for imaging. A suitable aperture size allows the incident light from the object surface to fill the aperture size as much as possible during reflection, reducing interference between light rays and improving the final imaging resolution.

[0053] Preferably, the sample surface has an X half-width of 45 mm and a Y half-width of 10 mm; the first reflector has an X half-width of 120 mm and a Y half-width of 100 mm; the second reflector has an X half-width of 47 mm and a Y half-width of 47 mm; the third reflector has an X half-width of 62 mm and a Y half-width of 62 mm; and the detector has an X half-width of 90 mm and a Y half-width of 20 mm.

[0054] The X half-width mentioned above is half the width in the X direction, and the Y half-width is half the width in the Y direction. X and Y can be understood as XY coordinates on the curved surface. The X direction is usually horizontal, with the positive direction to the right, and the Y direction is usually vertical, with the positive direction upwards. This XY coordinate system can also serve as the basis for subsequent iterative freeform surface calculations. The XY coordinates can divide the first to third reflecting mirrors into multiple rows and columns of reflecting units, allowing for adjustments to the reflecting units to adjust the final image resolution, thereby obtaining the final higher-resolution surface shape of the three-mirror system.

[0055] Optionally, the first reflector is tilted 22.803°±0.1° in the positive X direction and 107.365±0.05mm off-center in the negative Y direction, with the center of the sample surface as the reference; the second reflector is tilted 18.435°±0.1° in the positive X direction and -87.578±0.05mm off-center in the negative Y direction, with the center of the sample surface as the reference; and the third reflector is tilted 18.891°±0.1° in the positive X direction and 0±0.05mm off-center in the negative Y direction, with the center of the sample surface as the reference.

[0056] By adjusting the tilt angle and eccentricity of the first to third reflecting mirrors, the first to third reflecting mirrors achieve a better effect in reflecting light, resulting in a final image that meets the required magnification while also having a high resolution level.

[0057] Preferably, the first reflecting mirror is tilted 22.803° in the positive X direction and 107.365 mm off-center in the negative Y direction, with the center of the sample surface as the reference; the second reflecting mirror is tilted 18.435° in the positive X direction and -87.578 mm off-center in the negative Y direction, with the center of the sample surface as the reference; and the third reflecting mirror is tilted 18.891° in the positive X direction and 0 mm off-center in the negative Y direction, with the center of the sample surface as the reference.

[0058] Optionally, the first, second, and third reflectors are all obtained by offsetting multi-row, multi-column reflective units based on a reference sphere or plane using an extended polynomial of a freeform surface; the reflective units are N rows and N columns, totaling N. 2 indivual.

[0059] In this embodiment, N=7, and the number of offset reflection units is 32; the 32 offset reflection units of the first reflector and their offset values ​​are as follows: X1Y0: -0.760930, X0Y1: 13.153348, X2Y0: 13.635789, X1Y1: 1.367431, X0Y2: -3.791197, X3Y0: 0.216658, X2Y1: 7.884740, X1Y2: -1.284617, , X1Y3: 0.422374, X0Y4: 5.331834, X5Y0: -0.007190, X4Y1: 1.894870, 091812, X6Y0: 2.242588, X5Y1: -0.006009, X4Y2: 5.936232, X3Y3: 0.230368, X2Y4: 6.044876, X1Y5: 0.183219, X0Y6: 2.725690, X7Y0: 0.353704, X6Y1: -0.457662, X5Y2: 0.420403, X4Y3: -0.291715, X3Y4: 0.717853; The 32 offset reflection units of the second reflector and their offset values ​​are as follows: X1Y0: -0.394811, X0Y... 1: -2.651220, X2Y0: -3.058057, X1Y1: 1.041852, X0Y2: 3.496239, X3Y0: 0.104874, 96, X4Y0: -1.580678, X3Y1: 0.111114, X2Y2: -2.754367, .164886, X2Y3: 0.350123, X1Y4: -0.070959, X0Y5: -0.222807, X2Y4: -0.133963, X1Y5: -0.010376, X0Y6: -0.043601, X7Y0: -0.094356, X6Y1: 0.310630,128676; The 32 offset reflection units of the third reflecting mirror and their offset values ​​are as follows: X1Y0: -0.824707, X0Y1: 14.399089, X2Y0: -4.746276, X1Y1: 1.711498, X0Y2: 8.129082, X3Y0: -0.054087, X2Y1: 7.6 72633, X1Y2: -0.142714, X0Y3: 2.8415552, X4Y0: -4.268298, , X2Y2: 4.186820, X1Y3: -0.720680, X0Y4: 0.441362, X5Y0: 0.179992, .356381, X3Y2: -1.168841, X2Y3: -5.641012, X1Y4: 0.750136, 58, X6Y0: -1.634471, X5Y1: -0.353238, X4Y2: -6.016485, Y4: 4.328049, X1Y5: -0.263217, X0Y6: 0.623647, X7Y0: 0.078872, X6Y1: 0.356265, X5Y2: 0.497625, X4Y3: 3.332386, X3Y4: -0.186826; the offset error of the reflection unit is ±1%.

[0060] The aforementioned curved surface shape is the optimal freeform surface shape for the first to third reflecting mirrors. It can achieve a resolution at the micrometer level, a single imaging field of view of 45mm×10mm, and has the characteristics of compact size and easy manufacturing.

[0061] It should be noted that this embodiment also provides an optional implementation method, which will be described in detail below.

[0062] To address the shortcomings of existing technologies, a three-reflection imaging system based on a freeform surface with finite conjugate distance axes is provided. This system can achieve micrometer-level resolution, a single imaging field of view of 45mm×10mm, and features compact size and ease of fabrication.

[0063] This embodiment of a finite conjugate distance axis three-mirror imaging system based on a freeform surface includes a first mirror, a second mirror, a third mirror, and a detector. Incident light rays pass through the sample surface and are reflected sequentially by the first mirror, the second mirror, and the third mirror before being imaged on the detector. The first mirror, the second mirror, and the third mirror all use freeform surface extended polynomials, and the entire three-mirror imaging system has a compact structure and is unobstructed.

[0064] The second mirror also serves as an aperture stop.

[0065] The aforementioned three-mirror imaging system operates in the wavelength range of 0.40μm to 1.00μm, with a maximum field of view of 7° in the meridional direction and 1.5° in the sagittal direction. The field of view ranges from -4.5° to +2.5° in the sagittal direction and from -0.75° to +0.75° in the meridional direction. The RMS wave aberration within the field of view is 0.02λ to 0.05λ, where λ is the wavelength. The focal length is 400mm, and the image space F-number is 3.

[0066] The field of view has a root mean square radius of 0.582 μm to 1.289 μm and a geometric radius of 1.319 μm to 3.994 μm. The transfer function at 330 lp / mm for the entire wavelength from 0.40 μm to 1.00 μm is better than 0.2, and the transfer function at 100 lp / mm for the entire wavelength from 0.40 μm to 1.00 μm is better than 0.7.

[0067] The aforementioned three-mirror imaging system has an aperture of 120-160 mm. Preferably, the sample surface has a radius of curvature of ∞, an X half-width of 45 mm, and a Y half-width of 10 mm. The first mirror has a radius of curvature of -442.400 mm, a quadratic surface coefficient of -0.0840, an X half-width of 120 mm, and a Y half-width of 100 mm. The first mirror is tilted 22.803° in the positive X direction and 107.365 mm off-center in the negative Y direction, with the center of the sample surface as the reference. The second mirror has a radius of curvature of -316.613 mm and a quadratic surface coefficient of -2.270. 2. The X half-width is 47mm, and the Y half-width is 47mm. The second reflector is tilted 18.435° in the positive X direction and -87.578mm off-center in the negative Y direction, with the center of the sample surface as the reference. The radius of curvature of the third reflector is -809.019mm, the quadratic surface coefficient is 11.4828, the X half-width is 62mm, and the Y half-width is 62mm. The third reflector is tilted 18.891° in the positive X direction and 0mm off-center in the negative Y direction, with the center of the sample surface as the reference. The radius of curvature of the detector is ∞, the X half-width is 90mm, and the Y half-width is 20mm.

[0068] Preferably, the distance between the center of the sample surface and the center of the first reflector is 421.733 mm; the distance between the center of the first reflector and the center of the second reflector is 276.183 mm; the distance between the center of the second reflector and the center of the third reflector is 141.046 mm; and the distance from the center of the third reflector to the center of the detector plane is 475.306 mm.

[0069] Furthermore, the distance between the lowest incident ray and the upper edge of the second reflecting mirror is greater than 15mm; the distance between the highest reflected ray and the lower edge of the second reflecting mirror is greater than 35mm.

[0070] This implementation uses a free-form surface and a finite conjugate distance, balancing the ultra-large field of view (tens of centimeters) and micron-level high resolution required in high-throughput screening. It also leverages the advantage of visible light wavelengths reflecting off the mirror surface without chromatic aberration, avoiding the complexity of a three-mirror imaging system required for wide-band chromatic aberration correction. From the design stage, the distance between the three mirrors is minimized as much as possible, while reducing the possibility of interference from external tooling during assembly, thus providing ease of fabrication and assembly for the system development.

[0071] like Figure 1 As shown, the three-mirror imaging system in this embodiment includes a sample surface W1, a first reflecting mirror M1, a second reflecting mirror M2, a third reflecting mirror M3, and a detector D4; the second reflecting mirror M2 is also the aperture stop in this invention. Light from the sample surface is reflected sequentially by the first reflecting mirror M1, the second reflecting mirror M2, and the third reflecting mirror M3 before being imaged on the detector D4; the entire three-mirror imaging system has a compact structure and is unobstructed.

[0072] The field of view of the above-mentioned three-mirror imaging system is 7° in the meridional direction and 1.5° in the sagittal direction, with a field of view range of (-4.5° to +2.5°) in the sagittal direction and (-0.75° to +0.75°) in the meridional direction. The focal length is 400mm, the magnification is -2×, the total length is 610mm, and the spectral range is 0.40μm to 1.00μm.

[0073] The distance between the center of the sample surface and the center of the first reflector is 421.733 mm; the radius of curvature of the first reflector is -442.400 mm; the distance between the center of the first reflector and the center of the second reflector is 276.183 mm; the radius of curvature of the second reflector is -316.613 mm; the distance between the center of the second reflector and the center of the third reflector is 141.046 mm; the radius of curvature of the third reflector is -809.019 mm; and the distance from the center of the third reflector to the center of the detector plane is 475.306 mm.

[0074] The first, second, and third reflecting mirrors are all designed using freeform surface extended polynomials, and their corresponding surface elevation expressions are as follows:

[0075]

[0076] In the formula, The radius and height are along the optical axis; the first term on the right side of the equation is the equation of a conic section. Let be the curvature at the vertex of the curve. These are the coefficients of the conic surface, as shown in Table 1, which lists the structural parameters of the three-mirror imaging system. The second term on the right-hand side of the equation is the surface portion described by a polynomial. The total number of polynomial coefficients in the series. For the first The coefficients of the extended polynomial, which is only in , A power series in a direction. The first term is... Then Next is , , And so on. There are 2 terms of degree 1, 3 terms of degree 2, 4 terms of degree 3, and so on. The highest degree is 20, which makes the maximum total number of aspherical coefficients of the polynomial 230. and The data values ​​at each position are divided by a normalized radius to obtain a dimensionless polynomial coefficient. It represents a coordinate function that includes X and y. It can be understood as a plane formed by x and y in a plane perpendicular to the sag direction, with x and y as coordinates.

[0077] Table 1 Structural parameters of the three-mirror imaging system

[0078]

[0079] Table 2 Extended polynomial surface parameters of the first, second, and third reflecting mirrors

[0080]

[0081]

[0082] Figure 2 This is a dot diagram of a three-view imaging system provided according to an embodiment of this application, such as... Figure 2As shown, the RMS (root mean square) radii of each field of view are 1.289 μm, 0.677 μm, 1.218 μm, 0.985 μm, 0.710 μm, 1.091 μm, 1.141 μm, 0.603 μm, 0.938 μm, 1.094 μm, 0.582 μm, and 1.014 μm, respectively; the GEO (geometric) radii are 3.994 μm, 2.556 μm, 2.882 μm, 3.182 μm, 1.836 μm, 2.580 μm, 2.702 μm, 1.334 μm, 2.662 μm, 3.205 μm, 1.319 μm, and 2.561 μm, respectively; and the Airy disk radius is 1.793 μm. Because the reflective system has no chromatic aberration, the dot plots of different bands within the wavelength range of 0.40μm to 1.00μm are consistent. The Airy disk radius increases with the wavelength, so dot plots of other bands will not be listed.

[0083] Figure 3 This is a graph of the full field-of-view transfer function of the three-mirror imaging system provided according to the embodiments of this application at a cutoff frequency of 100 lp / mm, as shown below. Figure 3 As shown, Figure 3 The vertical axis represents the normalized OTF modulus, and the horizontal axis represents the spatial frequency, with units of lp / mm. The figure shows that both the on-axis and off-axis field-of-view transfer function curves are better than 0.7, indicating that the three-mirror imaging system has high imaging contrast across the entire field of view and distinct image detail.

[0084] Figure 4 This is a full-field transfer function curve of the three-mirror imaging system provided according to the embodiments of this application at a cutoff frequency of 330 lp / mm, as shown in the figure. Figure 4 As shown, Figure 4 The vertical axis represents the normalized OTF modulus, and the horizontal axis represents the spatial frequency, with units of lp / mm. The figure shows that both the on-axis and off-axis field-of-view transfer function curves are better than 0.2, indicating that the three-mirror imaging system has high imaging contrast across the entire field of view and distinct image detail.

[0085] Figure 5 This is a field curvature distortion map of a three-mirror imaging system provided according to an embodiment of this application, such as... Figure 5 As shown, Figure 5 The left-middle image is the field curvature diagram. The vertical axis represents the field of view, and the horizontal axis represents the field curvature, both in mm. Different wavelengths of light are represented by different gray levels. The field curvature values ​​for each wavelength and position within the field of view, from 0.40 μm to 1.00 μm, are all within ±4 μm. The axial difference between the optimal focusing point at the edge of the field of view and the optimal focusing point at the center of the field of view is less than 2λ / NA². Theoretically, this satisfies the requirement for sharpness across the entire field of view, meeting the requirements for a field-plan objective. The vertical axis in the image represents the normalized field of view; the horizontal axis represents the field curvature, with a maximum of 0.2 mm and a minimum of -0.2 mm. Figure 5 The right-hand image shows the distortion diagram. The vertical axis represents the field of view, and the horizontal axis represents the distortion (percentage). Different wavelengths of light are indicated by different gray levels. The distortion at each wavelength and position in the field of view from 0.40μm to 1.00μm is less than 5.26%. The vertical axis represents the normalized field of view; the horizontal axis represents the distortion, with a maximum of 10% and a minimum of -10%.

[0086] Of course, the three-mirror imaging system based on freeform surfaces with finite conjugate distance axes described in this embodiment can have various transformations and modifications, and is not limited to the specific structure of the embodiment described above. In short, the scope of protection of this embodiment should include those transformations, substitutions, and modifications that are obvious to those skilled in the art.

[0087] The present invention will now be described in conjunction with preferred implementation steps. Figure 6 This is a flowchart illustrating a method for determining a large field-of-view, high-resolution three-mirror imaging system for microdroplet enzyme observation, according to an embodiment of this application. Figure 6 As shown, the method includes the following steps:

[0088] Step S601: Determine the imaging magnification and aberration of the three-mirror imaging system for a sample surface of a preset size according to the imaging requirements.

[0089] Step S602: Determine the position information of the first, second, and third initial reflectors of the three-mirror imaging system based on the imaging magnification. The first initial reflector is a concave spherical surface used to reflect incident light from the sample surface into parallel light. The second and third initial reflectors are both planar surfaces. The distance between the center of the sample surface and the center of the first reflector is a first preset distance; the distance between the center of the first and second reflectors is a second preset distance; the first preset distance is greater than the second preset distance. The distance between the center of the second and third reflectors is a third preset distance; the distance from the center of the third reflector to the center of the detector plane is a fourth preset distance; the fourth preset distance is greater than the third preset distance. The distance between the lowest ray of the incident light from the sample surface and the upper edge of the second reflector is greater than a fifth preset distance; the distance between the highest ray reflected by the third reflector and the lower edge of the second reflector is greater than a sixth preset distance.

[0090] Step S603: Based on the aberration of the image formed by the outgoing light reflected by the third initial mirror, the surface shapes of the first, second, and third initial mirrors are iteratively determined by the freeform surface extended polynomial to obtain the first, second, and third mirrors, so that the aberration of the outgoing light from the third mirror meets the imaging requirements. The conjugate distance between the object plane of the sample surface and the image plane of the detector is finite.

[0091] The above steps determine the position information of the three initial mirrors in the three-mirror system through imaging magnification, and obtain the final freeform surfaces of the three mirrors in the three-mirror system by iterating through the freeform surface extended polynomial based on the final imaging aberration. The structure of the three-mirror system obtained by the above method forms an off-axis three-mirror imaging system with finite conjugate distance based on freeform surface shape. While ensuring a compact position structure, it achieves imaging of an ultra-large field of view of tens of centimeters, and ensures the imaging resolution at the micrometer level. It achieves the technical effect of high imaging resolution and large object-side field of view, thus solving the problem in related three-mirror imaging systems where imaging resolution and field of view cannot be simultaneously satisfied.

[0092] Optionally, determining the position information of the first, second, and third initial mirrors of the three-mirror imaging system based on the imaging magnification includes: selecting the initial position, initial angle, and initial distance according to the off-axis principle, and setting the first, second, and third initial mirrors; adjusting the first initial mirror so that the light output from the first initial mirror is closest to parallel light, and the imaging magnification of the light emitted from the third initial mirror meets the imaging magnification requirement.

[0093] Optionally, based on the aberration of the image formed by the outgoing rays reflected by the third initial mirror, the surface shapes of the first, second, and third initial mirrors are iteratively determined using a freeform surface extended polynomial to obtain the first, second, and third mirrors. This includes: determining the aberration of the image formed by the outgoing rays reflected by the third initial mirror; and iteratively adjusting the surface units on the first, second, and third initial mirrors according to the surface shape sag expression of the freeform surface extended polynomial until the aberrations all meet the imaging requirements, thus obtaining the first, second, and third mirrors.

[0094] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0095] The above are merely embodiments of this application and are not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A three-mirror imaging system for large field of view high resolution micro-droplet enzyme observation, characterized in that, Comprise: Three off-axis arranged mirrors, including a first mirror, a second mirror, and a third mirror; The first mirror is used for reflecting light incident on a sample plane to the second mirror, the second mirror is used for reflecting light reflected by the first mirror to the third mirror, and the third mirror is used for reflecting light reflected by the second mirror to a detector for imaging; The first mirror is a concave extended polynomial free-form surface, the second mirror is a convex extended polynomial free-form surface, and the third mirror is a concave extended polynomial free-form surface; The distance between the center of the sample plane and the center of the first mirror is a first preset distance, the distance between the center of the first mirror and the center of the second mirror is a second preset distance, and the first preset distance is greater than the second preset distance; The distance between the center of the second mirror and the center of the third mirror is a third preset distance, and the distance between the center of the third mirror and the center of the detector plane is a fourth preset distance, and the fourth preset distance is greater than the third preset distance; The distance between the lowermost light of the incident light on the sample plane and the upper edge of the second mirror is greater than a fifth preset distance, and the distance between the uppermost light reflected by the third mirror and the lower edge of the second mirror is greater than a sixth preset distance, and the fifth preset distance is less than the sixth preset distance; The conjugate distance between the object plane of the sample plane and the image plane of the detector is limited; The first mirror, the second mirror, and the third mirror are all based on a reference spherical surface or a reference plane, and are obtained by offsetting a plurality of rows and a plurality of columns of reflecting units using an extended polynomial of a free-form surface; the reflecting units are N rows and N columns in total, N 2 ​ N=7, the number of offset reflection units is 32; The 32 offset reflection units of the first mirror and their offsets are as follows: X1Y0: -0.760930, X0Y1: 13.153348, X2Y0: 13.635789, X1Y1: 1.367431, X0Y2: -3.791197, X3Y0: 0.216658, X2Y1: 7.884740, X1Y2: -1.284617, X0Y3: -4.258433, X4Y0: 4.345773, X3Y1: -0.073016, X2Y2: 6.626360, X1Y3: 0.422374, X0Y4: 5.331834, X5Y0: -0.007190, X4Y1: 1.894870, X3Y2: -0.234292, X2Y3: 1.078524, X1Y4: -0.318512, X0Y5: -1.091812, X6Y0: 2.242588, X5Y1: -0.006009, X4Y2: 5.936232, X3Y3: 0.230368, X2Y4: 6.044876, X1Y5: 0.183219, X0Y6: 2.725690, X7Y0: 0.353704, X6Y1: -0.457662, X5Y2: 0.420403, X4Y3: -0.291715, X3Y4: 0.717853; The 32 shifted reflective units of the third reflective mirror and their shift amounts are respectively: X1Y0:-0.824707, X0Y1:14.399089, X2Y0:-4.746276, X1Y1:1.711498, X0Y2:8.129082, X3Y0:-0.054087, X2Y1:7.672633, X1Y2:-0.142714, X0Y3:2.8415552, X4Y0:-4.268298, X3Y1:1.070612, X2Y2:4.186820, X1Y3:-0.720680, X0Y4:0.441362, X5Y0:0.179992, X4Y1:6.356381, X3Y2:-1.168841, X2Y3:-5.641012, X1Y4:0.750136, X0Y5:-0.305958, X6Y0:-1.634471, X5Y1:-0.353238, X4Y2:-6.016485, X3Y3:0.859503, X2Y4:4.328049, X1Y5:-0.263217, X0Y6:0.623647, X7Y0:0.078872, X6Y1:0.356265, X5Y2:0.497625, X4Y3:3.332386, X3Y4:-0.186826; The 32 shifted reflective units of the third reflective mirror and their shift amounts are respectively: X1Y0:-0.824707, X0Y1:14.399089, X2Y0:-4.746276, X1Y1:1.711498, X0Y2:8.129082, X3Y0:-0.054087, X2Y1:7.672633, X1Y2:-0.142714, X0Y3:2.8415552, X4Y0:-4.268298, X3Y1:1.070612, X2Y2:4.186820, X1Y3:-0.720680, X0Y4:0.441362, X5Y0:0.179992, X4Y1:6.356381, X3Y2:-1.168841, X2Y3:-5.641012, X1Y4:0.750136, X0Y5:-0.305958, X6Y0:-1.634471, X5Y1:-0.353238, X4Y2:-6.016485, X3Y3:0.859503, X2Y4:4.328049, X1Y5:-0.263217, X0Y6:0.623647, X7Y0:0.078872, X6Y1:0.356265, X5Y2:0.497625, X4Y3:3.332386, X3Y4:-0.186826; The error of the offset of the reflecting unit is ±1%.

2. The three-mirror imaging system of claim 1, wherein, the first preset distance is 421.733 mm with an error of ±1%; and the second preset distance is 276.183 mm with an error of ±1%; the third preset distance is 141.046 mm with an error of ±1%; and the fourth preset distance is 475.306 mm with an error of ±1%; the fifth preset distance is 15 mm with an error of ±1%; and the sixth preset distance is 35 mm with an error of ±1%.

3. The three-mirror imaging system of claim 2, wherein, the radius of curvature of the first mirror is -442.400 mm with an error of ±1%, and the quadratic surface coefficient is -0.0840 with an error of ±0.5%; the radius of curvature of the second mirror is -316.613 mm with an error of ±1%, and the quadratic surface coefficient is -2.2702 with an error of ±0.5%; the radius of curvature of the third mirror is -809.019 mm with an error of ±1%, and the quadratic surface coefficient is 11.4828 with an error of ±0.5%.

4. The three-mirror imaging system of claim 3, wherein, the X half-width of the minimum aperture size of the sample surface is 45 mm, and the Y half-width is 10 mm; the X half-width of the minimum aperture size of the first mirror is 120 mm, and the Y half-width is 100 mm; the X half-width of the minimum aperture size of the second mirror is 47 mm, and the Y half-width is 47 mm; the X half-width of the minimum aperture size of the third mirror is 62 mm, and the Y half-width is 62 mm; the X half-width of the minimum aperture size of the detector is 90 mm, and the Y half-width is 20 mm.

5. The three-mirror imaging system of claim 4, wherein, the first mirror is positively inclined to the X direction by 22.803°±0.1° and is negatively inclined to the Y direction by 107.365±0.05 mm with the center of the sample surface as a reference; the second mirror is positively inclined to the X direction by 18.435°±0.1° and is negatively inclined to the Y direction by -87.578±0.05 mm with the center of the sample surface as a reference; the third mirror is positively inclined to the X direction by 18.891°±0.1° and is negatively inclined to the Y direction by 0±0.05 mm with the center of the sample surface as a reference.

6. A method for determining a large field of view high resolution three- mirror imaging system for micro-droplet enzyme observation, characterized in that, comprising: determining the imaging magnification and aberration of the three-mirror imaging system for a preset size sample surface according to imaging requirements; and According to the imaging magnification, position information of a first initial mirror, a second initial mirror and a third initial mirror of a three-mirror imaging system is determined, wherein the first initial mirror is a concave spherical surface for reflecting incident light rays of a sample plane into parallel light rays, the second initial mirror is a plane, the third initial mirror is a plane, a distance between the center of the sample plane and the center of the first mirror is a first preset distance, a distance between the center of the first mirror and the center of the second mirror is a second preset distance, the first preset distance is greater than the second preset distance, a distance between the center of the second mirror and the center of the third mirror is a third preset distance, a distance between the center of the third mirror and the center of a detector plane is a fourth preset distance, the fourth preset distance is greater than the third preset distance, a distance between the lowest light ray of the incident light rays of the sample plane and the upper edge of the second mirror is greater than a fifth preset distance, a distance between the uppermost light ray of the reflected light rays of the third mirror and the lower edge of the second mirror is greater than a sixth preset distance; According to an aberration of an image formed by the reflected light rays of the third initial mirror, surface types of the first initial mirror, the second initial mirror and the third initial mirror are determined iteratively by using an extended polynomial of a free-form surface, so that the first mirror, the second mirror and the third mirror are obtained, and an aberration of the reflected light rays of the third mirror satisfies the imaging requirement, wherein a conjugate distance between an object plane of the sample plane and an image plane of the detector is limited; The first mirror, the second mirror and the third mirror are all obtained by using an extended polynomial of a free-form surface to offset a plurality of rows and columns of mirror units based on a reference spherical surface or a reference plane; The reflection unit is N rows and N columns, a total of N 2 individuals; N=7, and the number of the offset mirror units is 32. The 32 shifted reflective units of the first reflective mirror and their shift amounts are respectively: X1Y0:-0.760930, X0Y1:13.153348, X2Y0:13.635789, X1Y1:1.367431, X0Y2:-3.791197, X3Y0:0.216658, X2Y1:7.884740, X1Y2:-1.284617, X0Y3:-4.258433, X4Y0:4.345773, X3Y1:-0.073016, X2Y2:6.626360, X1Y3:0.422374, X0Y4:5.331834, X5Y0:-0.007190, X4Y1:1.894870, X3Y2:-0.234292, X2Y3:1.078524, X1Y4:-0.318512, X0Y5:-1.091812, X6Y0:2.242588, X5Y1:-0.006009, X4Y2:5.936232, X3Y3:0.230368, X2Y4:6.044876, X1Y5:0.183219, X0Y6:2.725690, X7Y0:0.353704, X6Y1:-0.457662, X5Y2:0.420403, X4Y3:-0.291715, X3Y4:0.717853; The 32 shifted reflective units of the second reflective mirror and their shift amounts are respectively: X1Y0:-0.394811, X0Y1:-2.651220, X2Y0:-3.058057, X1Y1:1.041852, X0Y2:3.496239, X3Y0:0.104874, X2Y1:4.542191, X1Y2:-0.617359, X0Y3:-1.874196, X4Y0:-1.580678, X3Y1:0.111114, X2Y2:-2.754367, X1Y3:0.081516, X0Y4:-1.193266, X5Y0:0.025889, X4Y1:0.954054, X3Y2:-0.164886, X2Y3:0.350123, X1Y4:-0.070959, X0Y5:-0.222807, X6Y0:-0.061222, X5Y1:0.042719, X4Y2:-0.509731, X3Y3:0.111716, X2Y4:-0.133963, X1Y5:-0.010376, X0Y6:-0.043601, X7Y0:-0.094356, X6Y1:0.310630, X5Y2:-0.044908, X4Y3:0.616155, X3Y4:-0.128676; The offset amounts of the 32 offset reflective units of the third mirror are as follows: X1Y0:-0.824707, X0Y1:14.399089, X2Y0:-4.746276, X1Y1:1.711498, X0Y2:8.129082, X3Y0:-0.054087, X2Y1:7.672633, X1Y2:-0.142714, X0Y3:2.8415552, X4Y0:-4.268298, X3Y1:1.070612, X2Y2:4.186820, X1Y3:-0.720680, X0Y4:0.441362, X5Y0:0.179992, X4Y1:6.356381, X3Y2:-1.168841, X2Y3:-5.641012, X1Y4:0.750136, X0Y5:-0.305958, X6Y0:-1.634471, X5Y1:-0.353238, X4Y2:-6.016485, X3Y3:0.859503, X2Y4:4.328049, X1Y5:-0.263217, X0Y6:0.623647, X7Y0:0.078872, X6Y1:0.356265, X5Y2:0.497625, X4Y3:3.332386, X3Y4:-0.186826; The error of the offset amount of the reflective unit is ±1%.

7. The method of claim 6, wherein, The position information of the first initial mirror, the second initial mirror and the third initial mirror of the three-mirror imaging system is determined according to the imaging magnification, and the position information of the first initial mirror, the second initial mirror and the third initial mirror is determined according to the imaging magnification. According to the principle of off-axis, the initial position, the initial angle and the initial distance are selected, and the first initial mirror, the second initial mirror and the third initial mirror are set; The first initial mirror is adjusted so that the light output by the first initial mirror is closest to parallel light, and the imaging magnification of the image formed by the light emitted by the third initial mirror satisfies the imaging requirement.

8. The method of claim 7, wherein, According to the aberration of the image formed by the light emitted by the third initial mirror, the surface type of the first initial mirror, the second initial mirror and the third initial mirror is determined by iteration according to the free surface extension polynomial, and the first mirror, the second mirror and the third mirror are obtained. The aberration of the image formed by the light emitted by the third initial mirror is determined. According to the surface type of the free surface extension polynomial, the surface units on the first initial mirror, the second initial mirror and the third initial mirror are adjusted by iteration until the aberration satisfies the imaging requirement, and the first mirror, the second mirror and the third mirror are obtained.

Images