Multi-spectral imaging system with secondary mirror beam splitting

Abstract

The present invention relates to a multi-spectral imaging system with secondary mirror light splitting, comprising: a medium-wave infrared channel and a visible light channel, wherein the medium-wave infrared channel and the visible light channel share a Cassegrain structure at the front end of the optical path; the Cassegrain structure comprises, in order along the optical path, a primary mirror and a secondary mirror; the primary mirror reflects visible light and medium-wave infrared light, while the secondary mirror reflects visible light and transmits medium-wave infrared light; and the secondary mirror's first convex surface is used for light splitting. The multi-spectral imaging system with secondary mirror light splitting of the present invention achieves Cassegrain common-aperture imaging of visible light and medium-wave infrared light, and light splitting by the secondary mirror solves the problem of residual astigmatism caused by traditional light splitting plates, improves the imaging quality of the two channels, reduces the difficulty of assembly and adjustment, reduces costs, and improves space utilization.

Description

Technical Field

[0001] The present invention relates to the technical field of aviation imaging payloads, and in particular to a multi-spectral imaging system with secondary mirror light splitting. Background Art

[0002] In the field of aerial imaging payloads, multi-spectral imaging lenses have become a standard feature of aerial payloads. In pursuit of longer focal lengths, more compact structures, and higher information collection capabilities, Catherine reflective lenses have also been widely used in imaging lenses, and imaging solutions that share the Catherine main aperture for multiple spectra have gradually emerged. This requires multi-spectral splitting in the optical path. The traditional splitting solution uses a beam splitter plate to divide the light beam into two bands: reflection and transmission. This beam splitter plate needs to be placed in a quasi-parallel optical path to avoid introducing aberrations. In order to achieve a quasi-parallel optical path, it is necessary to design a multi-spectral co-collimated transmission or reflection structure. The transmission structure requires more lenses for spectral bands with a larger span, and the lens materials that can be used are very limited and expensive, and the collimation effect is not ideal. The reflective collimation structure requires the introduction of aspheric reflectors, which are extremely difficult to assemble and adjust. If the splitting is performed in a non-collimated optical path, as the thickness of the splitting plate increases, the astigmatism introduced into the transmitted light path will also increase, which is very unfavorable for the aberration correction of the transmitted light beam. In order to correct the astigmatism, it is even necessary to introduce an additional correction plate, which undoubtedly reduces the transmittance of the system and takes up more space. Summary of the Invention

[0003] The present invention aims to solve the problem that in conventional multi-spectral spectrometry in the prior art, a spectroscopic plate needs to be placed in a collimated light path, which leads to a complex collimated light path, low system transmittance, difficulty in assembly and adjustment, and high manufacturing cost. At the same time, in order to solve the technical problem that the spectroscopic plate is placed in a non-collimated light path, which causes large astigmatism in the transmission imaging channel and difficulty in correcting system aberrations, a multi-spectral imaging system with secondary mirror spectrometry is provided.

[0004] In order to solve the above technical problems, the technical solutions of the present invention are as follows:

[0005] A multi-spectral imaging system with secondary mirror light splitting, comprising: a medium-wave infrared channel and a visible light channel, wherein the medium-wave infrared channel and the visible light channel share a Catherine structure at the front end of the optical path;

[0006] The Cather Green structure comprises, in order in the direction of the optical path: a primary mirror and a secondary mirror;

[0007] The primary mirror reflects visible light and medium-wave infrared light, and the secondary mirror reflects visible light and transmits medium-wave infrared light; the first convex surface of the secondary mirror is used for light splitting;

[0008] The medium-wave infrared channel includes, in order along the optical path, a first lens, a first reflecting surface of a first reflecting mirror, a second lens, a third lens, a fourth lens, a second reflecting surface of a second reflecting mirror, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens, a window of an infrared detector, a cold stop surface of the infrared detector, and an image plane of the infrared detector;

[0009] The light transmitted through the Cassegrain structure secondary mirror passes through the first lens and the first reflector in sequence. The first reflector bends the light path to form a primary image point. The light is then collimated through the second lens, the third lens, and the fourth lens. The second reflector is located at the exit pupil position of the collimated light beam. The collimated light beam passes through the fifth lens and the sixth lens to converge to form a secondary image point. The light is then corrected for aberrations through the seventh lens, the eighth lens, and the ninth lens to complete a third imaging, and the image point falls on the image plane of the infrared detector.

[0010] The visible light channel includes, in order along the optical path, a cemented mirror, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens, and an image plane of a visible light detector;

[0011] The light reflected by the Cassegrain structure passes through the cemented mirror in sequence to correct chromatic aberration, and is perfected into visible light imaging by the tenth lens, the eleventh lens, the twelfth lens and the thirteenth lens, with the image plane falling on the image plane of the visible light detector.

[0012] In the above technical solution, the secondary mirror is a meniscus-shaped silicon lens, and the convex surface of the secondary mirror faces the primary mirror; the convex surface of the secondary mirror reflects visible light energy and transmits medium-wave infrared energy.

[0013] In the above technical solution, the secondary mirror satisfies the following conditions: 154<curvature radius of the first surface of the secondary mirror<155; 70<curvature radius of the second surface of the secondary mirror<73.

[0014] In the above technical solution, the primary mirror satisfies: 168<radius of curvature of the primary mirror reflecting surface<173.

[0015] In the above technical solution, the first lens satisfies: 169<the curvature radius of the first surface of the first lens<170; 122<the curvature radius of the second surface of the first lens<124;

[0016] The second lens satisfies the following conditions: 116<curvature radius of the first surface of the second lens<118; 50<curvature radius of the second surface of the second lens<51;

[0017] The third lens satisfies the following conditions: 54<curvature radius of the first surface of the third lens<56; 31<curvature radius of the second surface of the third lens<34;

[0018] The fourth lens satisfies the following conditions: 94<curvature radius of the first surface of the fourth lens<95; 430<curvature radius of the second surface of the fourth lens<434.

[0019] In the above technical solution, the fifth lens satisfies: 31<curvature radius of the first surface of the fifth lens<32; 72<curvature radius of the second surface of the fifth lens<74;

[0020] The sixth lens satisfies the following conditions: 49 < the curvature radius of the first surface of the sixth lens < 50; 26 < the curvature radius of the second surface of the sixth lens < 28;

[0021] The seventh lens satisfies the following conditions: 17 < the curvature radius of the first surface of the seventh lens < 18; 24 < the curvature radius of the second surface of the seventh lens < 26;

[0022] The eighth lens satisfies the following conditions: 55<curvature radius of the first surface of the eighth lens<57; 131<curvature radius of the second surface of the eighth lens<132;

[0023] The ninth lens satisfies the following conditions: 44<curvature radius of the first surface of the ninth lens<46; 41<curvature radius of the second surface of the ninth lens<43.

[0024] In the above technical solution, the composite mirror satisfies the following conditions: 55<radius of curvature of the first surface of the composite mirror<56; 45<radius of curvature of the second surface of the composite mirror<47; 276<radius of curvature of the third surface of the composite mirror<280;

[0025] The tenth lens satisfies the following conditions: 63 < the curvature radius of the first surface of the tenth lens < 64; 22 < the curvature radius of the second surface of the tenth lens < 23;

[0026] The eleventh lens satisfies the following conditions: 155<the curvature radius of the first surface of the eleventh lens<157; 38<the curvature radius of the second surface of the eleventh lens<40;

[0027] The twelfth lens satisfies the following conditions: 377<the curvature radius of the first surface of the twelfth lens<378; 105<the curvature radius of the second surface of the twelfth lens<107;

[0028] The thirteenth lens satisfies the following conditions: 62<curvature radius of the first surface of the thirteenth lens<65; 512<curvature radius of the second surface of the thirteenth lens<514.

[0029] In the above technical solution, the reflecting surface of the primary mirror, the first surface of the secondary mirror, the first surface of the first lens, the second surface of the second lens, the first surface of the fourth lens, the first surface of the fifth lens, the second surface of the sixth lens and the first surface of the ninth lens are aspherical surfaces respectively satisfying:

[0030] Aspheric coefficient formula

[0031] Among them, z is the distance vector height from the aspheric surface vertex when the aspheric surface is at a height r along the optical axis, c represents the vertex curvature of the surface, k is the cone coefficient, and a2, a3, and a4 are high-order aspheric coefficients respectively.

[0032] In the above technical solution, the cone coefficient k and the high-order aspheric coefficients a2, a3, and a4 respectively satisfy:

[0033] The primary mirror reflection surface: k is -1, a2 is 0, a3 is 0, and a4 is 0;

[0034] For the first side of the secondary mirror: k is -3.13, a2 is 0, a3 is 0, and a4 is 0;

[0035] For the first surface of the first lens: k is 0, a2 is -1.0e-7, a3 is -8.65e-12, and a4 is 0;

[0036] For the second surface of the second lens, k is 0, a2 is -2.4e-6, a3 is 3.57e-9, and a4 is 0;

[0037] For the first surface of the fourth lens: k is 0, a2 is -2.2e-6, a3 is -1.94e-9, and a4 is 0;

[0038] For the first surface of the fifth lens: k is 0, a2 is 5.0e-7, a3 is 1.6e-8, and a4 is -1.11e-10;

[0039] On the second surface of the sixth lens: k is 0, a2 is 5.44e-6, a3 is 1.6e-7, and a4 is -2.27e-9;

[0040] On the first surface of the ninth lens, k is 0, a2 is 2.89e-5, a3 is -5.3e-8, and a4 is -7.3e-11.

[0041] In the above technical solution, the material of the secondary mirror is silicon material.

[0042] The present invention has the following beneficial effects:

[0043] The multi-spectral imaging system with secondary mirror spectrometry of the present invention realizes Cather Green common aperture imaging of visible light and medium-wave infrared. The spectrometry is performed by the secondary mirror, which solves the problem of residual astigmatism caused by traditional spectrometry with a spectrometer, improves the imaging quality of the two channels, reduces the difficulty of installation and adjustment, reduces costs and improves space utilization.

[0044] The secondary-mirror multispectral imaging system of the present invention is based on infrared and visible light imaging theory and is suitable for cooled infrared detectors with a 640×512 pixel size and a 15μm pixel size. It achieves a multispectral imaging system with a visible light channel focal length of 1100mm and an infrared channel focal length of 800mm.

[0045] The multi-spectral imaging system with secondary mirrors in this invention uses a silicon secondary mirror as the splitting surface for splitting visible light and mid-wave infrared light. The secondary mirror is a meniscus lens with a convex surface facing the primary mirror. This convex surface reflects visible light and transmits mid-wave infrared light, eliminating the introduction of new aberrations during the splitting process and achieving perfect imaging in both channels. The secondary mirror not only splits the light but also participates in imaging, simplifying the structure and assembly process. The two mirror deflections in the infrared light path also reduce the overall payload size.

[0046] As the aperture and size required by different engineering projects change, the multi-spectral imaging system with secondary mirror light splitting of the present invention can be scaled up or down and simply optimized to meet different design specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0048] Figure 1 The figure is a schematic diagram showing the position relationship of the lenses of the medium-wave infrared channel of the multi-spectral imaging system with secondary mirror light splitting according to the present invention.

[0049] Figure 2 The figure is a schematic diagram showing the position relationship of the lenses of the visible light channel of the multi-spectral imaging system with secondary mirror light splitting according to the present invention.

[0050] Figure 3 It is a schematic diagram of the surface position relationship of the medium-wave infrared channel of the multi-spectral imaging system of the secondary mirror splitting of the present invention.

[0051] Figure 4 It is a schematic diagram of the surface position relationship of the visible light channel of the multi-spectral imaging system of the secondary mirror splitting of the present invention.

[0052] The reference numerals in the figures indicate:

[0053] 1-primary mirror; 2-secondary mirror; 3-first lens; 4-first reflector; 5-second lens; 6-third lens; 7-fourth lens; 8-second reflector; 9-fifth lens; 10-sixth lens; 11-seventh lens; 12-eighth lens; 13-ninth lens; 14-infrared detector window; 17-cemented mirror; 18-tenth lens; 19-eleventh lens; 20-twelfth lens; 21-thirteenth lens;

[0054] S1 is the main mirror reflection surface;

[0055] S2-1 is the first side of the secondary mirror, and S2-2 is the second side of the secondary mirror;

[0056] S3-1 is the first surface of the first lens, and S3-2 is the second surface of the first lens;

[0057] S4 is the first reflecting surface;

[0058] S5-1 is the first surface of the second lens, and S5-2 is the second surface of the second lens;

[0059] S6-1 is the first surface of the third lens, and S6-2 is the second surface of the third lens;

[0060] S7-1 is the first surface of the fourth lens, and S7-2 is the second surface of the fourth lens;

[0061] S8 is the second reflecting surface;

[0062] S9-1 is the first surface of the fifth lens, and S9-2 is the second surface of the fifth lens;

[0063] S10-1 is the first surface of the sixth lens, and S10-2 is the second surface of the sixth lens;

[0064] S11-1 is the first surface of the seventh lens, and S11-2 is the second surface of the seventh lens;

[0065] S12-1 is the first surface of the eighth lens, and S12-2 is the second surface of the eighth lens;

[0066] S13-1 is the first surface of the ninth lens, and S13-2 is the second surface of the ninth lens;

[0067] S15 is the cold stop surface of the infrared detector; S16 is the image surface of the infrared detector;

[0068] S17-1 is the first surface of the composite mirror, S17-2 is the second surface of the composite mirror, and S17-3 is the third surface of the composite mirror;

[0069] S18-1 is the first surface of the tenth lens, and S18-2 is the second surface of the tenth lens;

[0070] S19-1 is the first surface of the eleventh lens, and S19-2 is the second surface of the eleventh lens;

[0071] S20-1 is the first surface of the twelfth lens, and S20-2 is the second surface of the twelfth lens;

[0072] S21-1 is the first surface of the thirteenth lens, and S21-2 is the second surface of the thirteenth lens;

[0073] S22 is the visible light detector image plane. DETAILED DESCRIPTION

[0074] The inventive concept of the present invention is:

[0075] Based on the theory of visible light and mid-infrared imaging, this invention designs an imaging lens that uses a common Catherine Green primary aperture for both visible and mid-wave infrared. Visible light is reflected by the Catherine Green's primary and secondary mirrors, then passes through several lenses for aberration correction before being imaged directly. Mid-wave infrared energy, after being reflected by the Catherine Green's primary mirror, passes through the secondary mirror to achieve primary imaging. A collimating lens assembly then converts the primary image point into a perfectly collimated optical path, and then passes through the secondary imaging assembly to achieve perfect imaging, achieving 100% cold-stop matching.

[0076] Visible and medium-wave infrared (MWIR) light sources share a common Catherine primary aperture imaging lens, with a primary mirror of 200mm and a secondary mirror of 60mm. Visible light energy, after reflection from the primary and secondary Catherine mirrors, passes through several lenses for aberration correction before being imaged directly. The detector image plane is designed to be ±15mm circular, and the focal length of the visible channel is 1100mm. MWIR energy, after reflection from the primary Catherine mirror, passes through the secondary mirror, which is combined with a germanium lens to form a primary image. The secondary mirror is made of single-crystal silicon. Light emitted from the primary image point is converted into a perfectly collimated optical path by a collimating lens assembly, and then passes through a secondary imaging assembly to achieve a perfect image. The image is 100% cold-stop matched. The relative aperture of the MWIR channel is 1 / 4, and the detector image plane is designed to be ±6.25mm circular.

[0077] Visible light and medium-wave infrared are split on the surface of the single-crystal silicon secondary mirror. The reflected light is the visible light channel, and the transmitted light is the medium-wave infrared channel. At the same time, single-crystal silicon, as part of the infrared imaging channel, does not introduce aberrations, thus achieving perfect imaging of the two channels.

[0078] In the multi-spectral imaging system with secondary mirrors, the visible light channel, from the object side to the image side, first receives visible light through the full aperture of the Cassegrain primary mirror. This light is then reflected to the secondary mirror and further reflected by the silicon secondary mirror. The focal length of the primary and secondary mirror reflection system is 225.6 mm. Aberration correction is performed sequentially by five visible light lenses before the primary image point of the primary and secondary mirrors. Finally, the image is formed on the image plane of the visible light detector, with no intermediate image points.

[0079] In the mid-wave infrared channel, from the object side to the image side, the Cassegrain primary mirror receives mid-infrared light energy at its full aperture. This light is then reflected to the secondary mirror, a meniscus silicon lens. The visible and mid-infrared light are separated on the convex surface. The silicon secondary mirror participates in the infrared imaging optical path and, in conjunction with another meniscus lens, forms the primary image. A reflector folds the optical path before the primary image point, minimizing system size. A three-lens collimator then perfectly collimates the system light. A reflector placed within the collimated optical path further folds the path. The collimated light enters the secondary imaging group, undergoes aberration correction by five lenses, and is finally imaged onto the infrared detector image plane, achieving 100% cold stop matching.

[0080] In the specific embodiments of the secondary mirror spectrophotometric multi-spectral imaging system of the present invention, the Cassegrain structure, also known as the Cassegrain configuration, refers to an optical structure identical or similar to the Cassegrain telescope. The Cassegrain telescope, invented by Cassegrain in 1672, is a reflecting telescope consisting of two mirrors. The larger of the two mirrors is called the primary mirror, while the smaller is called the secondary or secondary mirror. Typically, a central aperture is provided in the primary mirror, with the image formed behind it. Its focal point is called the Cassegrain focus. Sometimes, an additional inclined plane mirror is added to form an image to the side. This type of Cassegrain telescope is also known as a Nesmus telescope.

[0081] The present invention will be described in detail below with reference to the accompanying drawings.

[0082] like Figure 1-4 As shown, the multi-spectral imaging system with secondary mirror spectrometry described in the present invention has a common Cassegrain structure from the object plane to the image plane, consisting of a primary mirror 1 and a secondary mirror 2. The primary mirror 1 has a primary reflective surface S1, and the secondary mirror 2 is a meniscus-shaped silicon lens. The convex surface S2-1 of the secondary mirror 2 faces the primary mirror 1. The convex surface S2-1 of the secondary mirror 2 reflects visible light energy and transmits mid-wave infrared energy.

[0083] like Figure 1 and 3As shown, the surfaces of each lens are arranged from the object side to the image side in the following order: the first surface S2-1 of the secondary mirror of the secondary mirror 2, and the second surface S2-2 of the secondary mirror of the secondary mirror 2; the first surface S3-1 of the first lens of the first lens 3, and the second surface S3-2 of the first lens; the first reflecting surface S4 of the first reflecting mirror 4; the first surface S5-1 of the second lens of the second lens 5, and the second surface S5-2 of the second lens; the first surface S6-1 of the third lens of the third lens 6, and the second surface S6-2 of the third lens; the first surface S7-1 of the fourth lens of the fourth lens 7, and the second surface S7-2 of the fourth lens; the second reflecting surface S8 of the second reflecting mirror 8; The fifth lens first surface S9-1 and the fifth lens second surface S9-2 of the fifth lens 9; the sixth lens first surface S10-1 and the sixth lens second surface S10-2 of the sixth lens 10; the seventh lens first surface S11-1 and the seventh lens second surface S11-2 of the seventh lens 11; the eighth lens first surface S12-1 and the eighth lens second surface S12-2 of the eighth lens 12; the ninth lens first surface S13-1 and the ninth lens second surface S13-2 of the ninth lens 13; the window 14 of the infrared detector, the cold light stop surface S15 of the infrared detector and the image surface S16 of the infrared detector.

[0084] like Figure 2 and 4 As shown, the first surface S17-1 and the second surface S17-2 of the cemented mirror 17; the first surface S18-1 and the second surface S18-2 of the tenth lens 18; the first surface S19-1 and the second surface S19-2 of the eleventh lens 19; the first surface S20-1 and the second surface S20-2 of the twelfth lens 20; the first surface S21-1 and the second surface S21-2 of the thirteenth lens 21; and the image surface S22 of the visible light detector.

[0085] like Figure 1-4As shown, the mid-wave infrared channel and visible light channel of the multi-spectral imaging system with secondary mirror splitting of the present invention share a primary mirror 1 and secondary mirror 2 in a Cassegrain structure. Primary mirror 1 reflects visible light and mid-wave infrared light, while secondary mirror 2 reflects visible light and transmits mid-wave infrared light. The convex secondary mirror first surface S2-1 of secondary mirror 2 achieves two-band spectrum splitting. For the infrared channel, light transmitted by secondary mirror 2 passes through first lens 3 and first reflector 4. After the first reflector 4, a primary image point is formed. The beam is then shaped into a perfectly collimated beam by second lens 5, third lens 6, and fourth lens 7. Second reflector 8 is located at the exit pupil of the collimated beam. The fifth lens 9, sixth lens 10, seventh lens 11, eighth lens 12, and ninth lens 13 are combined to form a secondary imaging group. The collimated beam passes through the fifth and sixth lenses 9 and 10 of the secondary imaging group, converging to form a secondary image point. Aberrations are then corrected by the seventh, eighth, and ninth lenses 11, completing tertiary imaging. The image point lands on the infrared detector image plane S16.

[0086] For the visible light channel, the light reflected by the Cassegreen structure first passes through the cemented mirror 17 to correct the chromatic aberration, and then passes through the tenth lens 18, the eleventh lens 19, the twelfth lens 20 and the thirteenth lens 21 to achieve perfect imaging of the visible light, and the image plane falls on the visible light detector image plane S22.

[0087] The following is a table of optical system parameters:

[0088] Table 1 System parameters of the infrared channel in the multi-spectral imaging system with secondary mirror splitting

[0089]

[0090]

[0091] Table 2 Visible light channel system parameters of the multi-spectral imaging system with secondary mirror splitting

[0092]

[0093] The system has a total of 8 aspheric surfaces, namely the primary mirror reflection surface S1, the secondary mirror first surface S2-1, the first lens first surface S3-1, the second lens second surface S5-2, the fourth lens first surface S7-1, the fifth lens first surface S9-1, the sixth lens second surface S10-2 and the ninth lens first surface S13-1.

[0094] Aspheric coefficient formula

[0095] Among them, z is the distance vector height from the aspheric surface vertex when the aspheric surface is at a height r along the optical axis, c represents the vertex curvature of the surface, k is the cone coefficient, a2, a3, a4, a5, a6 are the high-order aspheric coefficients, and Table 3 shows the aspheric coefficients of 8 surfaces.

[0096] If the high-order aspheric coefficients a5 and a6 are not considered, the aspheric coefficient formula is simplified to:

[0097]

[0098] Table 3 Aspheric coefficients of the multi-spectral imaging system with secondary mirror beam splitting

[0099] Surface serial number k <![CDATA[a2]]> <![CDATA[a3]]> <![CDATA[a4]]> S1 -1 0 0 0 S2-1 -3.13 0 0 0 S3-1 0 -1.0e-7 -8.65e-12 0 S5-2 0 -2.4e-6 3.57e-9 0 S7-1 0 -2.2e-6 -1.94e-9 0 S9-1 0 5.0e-7 1.6e-8 -1.11e-10 S10-2 0 5.44e-6 1.6e-7 -2.27e-9 S13-1 0 2.89e-5 -5.3e-8 -7.3e-11

[0100] The multi-spectral imaging system with secondary mirror spectrometry of the present invention realizes Cather Green common aperture imaging of visible light and medium-wave infrared. The spectrometry is performed by the secondary mirror, which solves the problem of residual astigmatism caused by traditional spectrometry with a spectrometer, improves the imaging quality of the two channels, reduces the difficulty of installation and adjustment, reduces costs and improves space utilization.

[0101] The secondary-mirror multispectral imaging system of the present invention is based on infrared and visible light imaging theory and is suitable for cooled infrared detectors with a 640×512 pixel size and a 15μm pixel size. It achieves a multispectral imaging system with a visible light channel focal length of 1100mm and an infrared channel focal length of 800mm.

[0102] The multi-spectral imaging system with secondary mirrors in this invention uses a silicon secondary mirror as the splitting surface for splitting visible light and mid-wave infrared light. The secondary mirror is a meniscus lens with a convex surface facing the primary mirror. This convex surface reflects visible light and transmits mid-wave infrared light, eliminating the introduction of new aberrations during the splitting process and achieving perfect imaging in both channels. The secondary mirror not only splits the light but also participates in imaging, simplifying the structure and assembly process. The two mirror deflections in the infrared light path also reduce the overall payload size.

[0103] As the aperture and size required by different engineering projects change, the multi-spectral imaging system with secondary mirror light splitting of the present invention can be scaled up or down and simply optimized to meet different design specifications.

[0104] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A multi-spectral imaging system with secondary mirror light splitting, characterized in that: include: A medium-wave infrared channel and a visible light channel, wherein the medium-wave infrared channel and the visible light channel share a Cassegrain structure at the front end of the optical path; The Cather Green structure comprises, in order in the direction of the optical path: a primary mirror (1) and a secondary mirror (2); The primary mirror (1) reflects visible light and medium-wave infrared light, and the secondary mirror (2) reflects visible light and transmits medium-wave infrared light; the convex surface of the secondary mirror first surface (S2-1) of the secondary mirror (2) is used for light splitting; The medium-wave infrared channel comprises, in order along the optical path, a first lens (3), a first reflection surface (S4) of a first reflection mirror (4), a second lens (5), a third lens (6), a fourth lens (7), a second reflection surface (S8) of a second reflection mirror (8), a fifth lens (9), a sixth lens (10), a seventh lens (11), an eighth lens (12), a ninth lens (13), a window (14) of an infrared detector, a cold stop surface (S15) of the infrared detector, and an image surface (S16) of the infrared detector; The light transmitted through the secondary mirror (2) of the Cather Green structure passes through the first lens (3) and the first reflector (4) in sequence, and the first reflector (4) turns the light path to form a primary image point; then passes through the second lens (5), the third lens (6), and the fourth lens (7) to collimate the light; the second reflector (8) is located at the exit pupil position of the collimated light beam; the collimated light beam passes through the fifth lens (9) and the sixth lens (10) to converge to form a secondary image point; then passes through the seventh lens (11), the eighth lens (12), and the ninth lens (13) to correct the aberration and complete the third imaging, and the image point falls on the image plane (S16) of the infrared detector; The visible light channel comprises, in order along the optical path direction, a cemented mirror (17), a tenth lens (18), an eleventh lens (19), a twelfth lens (20), a thirteenth lens (21) and a visible light detector image plane (S22); The light reflected by the Cassegrain structure passes through the cemented mirror (17) in sequence to correct chromatic aberration, and is then passed through the tenth lens (18), the eleventh lens (19), the twelfth lens (20) and the thirteenth lens (21) to achieve perfect imaging of visible light, with the image plane falling on the image plane (S22) of the visible light detector.

2. The multi-spectral imaging system with secondary mirror light splitting according to claim 1, characterized in that: The secondary mirror (2) is a meniscus-shaped silicon lens, and the convex surface of the secondary mirror first surface (S2-1) of the secondary mirror (2) faces the primary mirror (1); the convex surface of the secondary mirror first surface (S2-1) of the secondary mirror (2) reflects visible light energy and transmits medium-wave infrared energy.

3. The multi-spectral imaging system with secondary mirror light splitting according to claim 2, characterized in that: The secondary mirror (2) satisfies the following conditions: 154<the curvature radius of the first surface (S2-1) of the secondary mirror<155; 70<the curvature radius of the second surface (S2-2) of the secondary mirror<73.

4. The multi-spectral imaging system with secondary mirror light splitting according to claim 1, characterized in that: The primary mirror (1) satisfies the following conditions: 168<radius of curvature of primary mirror reflection surface (S1)<173.

5. The multi-spectral imaging system with secondary mirror light splitting according to claim 1, characterized in that: The first lens (3) satisfies the following conditions: 169<the curvature radius of the first surface (S3-1) of the first lens<170; 122<the curvature radius of the second surface (S3-2) of the first lens<124; The second lens (5) satisfies the following conditions: 116 < the curvature radius of the first surface (S5-1) of the second lens < 118; 50 < the curvature radius of the second surface (S5-2) of the second lens < 51; The third lens (6) satisfies the following conditions: 54<the curvature radius of the first surface (S6-1) of the third lens<56; 31<the curvature radius of the second surface (S6-2) of the third lens<34; The fourth lens (7) satisfies the following conditions: 94<the curvature radius of the first surface (S7-1) of the fourth lens<95; 430<the curvature radius of the second surface (S7-2) of the fourth lens<434.

6. The multi-spectral imaging system with secondary mirror light splitting according to claim 1, characterized in that: The fifth lens (9) satisfies the following conditions: 31 < the curvature radius of the first surface (S9-1) of the fifth lens < 32; 72 < the curvature radius of the second surface (S9-2) of the fifth lens < 74; The sixth lens (10) satisfies the following conditions: 49<the curvature radius of the first surface (S10-1) of the sixth lens<50; 26<the curvature radius of the second surface (S10-2) of the sixth lens<28; The seventh lens (11) satisfies the following conditions: 17 < the curvature radius of the first surface (S11-1) of the seventh lens < 18; 24 < the curvature radius of the second surface (S11-2) of the seventh lens < 26; The eighth lens (12) satisfies the following conditions: 55<the curvature radius of the first surface (S12-1) of the eighth lens<57; 131<the curvature radius of the second surface (S12-2) of the eighth lens<132; The ninth lens (13) satisfies the following conditions: 44<the curvature radius of the first surface (S13-1) of the ninth lens<46; 41<the curvature radius of the second surface (S13-2) of the ninth lens<43.

7. The multi-spectral imaging system with secondary mirror light splitting according to claim 1, characterized in that: The composite mirror (17) satisfies the following conditions: 55<the curvature radius of the first surface (S17-1) of the composite mirror<56; 45<the curvature radius of the second surface (S17-2) of the composite mirror<47; 276<the curvature radius of the third surface (S17-3) of the composite mirror<280; The tenth lens (18) satisfies the following conditions: 63<the curvature radius of the first surface (S18-1) of the tenth lens<64; 22<the curvature radius of the second surface (S18-2) of the tenth lens<23; The eleventh lens (19) satisfies the following conditions: 155<the curvature radius of the first surface (S19-1) of the eleventh lens<157; 38<the curvature radius of the second surface (S19-2) of the eleventh lens<40; The twelfth lens (20) satisfies the following conditions: 377<the curvature radius of the first surface (S20-1) of the twelfth lens<378; 105<the curvature radius of the second surface (S20-2) of the twelfth lens<107; The thirteenth lens (21) satisfies the following conditions: 62<the curvature radius of the first surface (S21-1) of the thirteenth lens<65; 512<the curvature radius of the second surface (S21-2) of the thirteenth lens<514.

8. The multi-spectral imaging system with secondary mirror light splitting according to any one of claims 1 to 7, characterized in that: The primary mirror reflecting surface (S1), the secondary mirror first surface (S2-1), the first lens first surface (S3-1), the second lens second surface (S5-2), the fourth lens first surface (S7-1), the fifth lens first surface (S9-1), the sixth lens second surface (S10-2) and the ninth lens first surface (S13-1) are aspherical surfaces, respectively satisfying: Aspheric coefficient formula Among them, z is the distance vector height from the aspheric surface vertex when the aspheric surface is at a height r along the optical axis, c represents the vertex curvature of the surface, k is the cone coefficient, and a2, a3, and a4 are high-order aspheric coefficients respectively.

9. The multi-spectral imaging system with secondary mirror light splitting according to claim 8, characterized in that: The cone coefficient k and the higher-order aspheric coefficients a2, a3, and a4 satisfy the following requirements: The primary mirror reflection surface (S1): k is -1, a2 is 0, a3 is 0, and a4 is 0; The first surface of the secondary mirror (S2-1): k is -3.13, a2 is 0, a3 is 0, and a4 is 0; The first surface (S3-1) of the first lens: k is 0, a2 is -1.0e-7, a3 is -8.65e-12, and a4 is 0; The second surface (S5-2) of the second lens: k is 0, a2 is -2.4e-6, a3 is 3.57e-9, and a4 is 0; For the first surface (S7-1) of the fourth lens, k is 0, a2 is -2.2e-6, a3 is -1.94e-9, and a4 is 0; For the first surface (S9-1) of the fifth lens, k is 0, a2 is 5.0e-7, a3 is 1.6e-8, and a4 is -1.11e-10; For the second surface (S10-2) of the sixth lens, k is 0, a2 is 5.44e-6, a3 is 1.6e-7, and a4 is -2.27e-9; The first surface (S13-1) of the ninth lens has k of 0, a2 of 2.89e-5, a3 of -5.3e-8, and a4 of -7.3e-11.

10. The multi-spectral imaging system with secondary mirror light splitting according to any one of claims 1 to 7 and 9, characterized in that: The material of the secondary mirror (2) is silicon material.

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