Visible light and long-wave infrared composite simulation optical system based on Cassegrain structure

Abstract

The utility model discloses a visible light and long-wave infrared composite simulation optical system based on a Cassegrain structure. The visible light and long-wave infrared composite simulation optical system comprises a light path synthesis unit, a plane mirror, a dichroscope, a visible light wave band simulation unit and a long-wave infrared wave band simulation unit which are sequentially arranged from left to right and from top to bottom along main light rays. According to the utility model, the visible light wave band simulation unit and the long-wave infrared wave band simulation unit are arranged, and a Cassegrain structure in the light path synthesis unit is combined to form the visible light and long-wave infrared dual-wave band imaging simulation optical system based on the Cassegrain object space coupling light path. The Cassegrain object space coupling optical path is adopted to carry out common aperture output, and the optical system has the advantages of being simple in structure and light in mass under the condition that the large view field and the long exit pupil distance can be met.

Description

Technical Field

[0001] The utility model belongs to the technical field of semi-physical simulation of guidance systems, and in particular relates to a visible light and long-wave infrared composite simulation optical system based on a Cassegrain structure. Background Art

[0002] With the development of science and technology, precision-guided weapons have become extremely important in modern warfare, and the seeker, as the "eyes" of precision-guided weapons, plays a vital role. At present, the seeker with single-mode guidance can no longer meet the requirements of precision guidance in complex battlefields. Composite guidance combines two or more guidance methods, gives full play to the advantages of two or more guidance methods, effectively counteracts various interferences in the battlefield environment, and improves the guidance accuracy. This is the trend of future technological development. Therefore, with the development of composite guidance systems, the corresponding simulators should also develop from single-mode to dual-mode or even multi-mode. However, most of the simulators in China are single-mode simulators. When facing multi-sensor optoelectronic equipment, they cannot provide targets of different bands at the same time. Therefore, facing the integrated optoelectronic test system with multi-spectral, multi-sensor, and multi-optical path fusion, a single simulator cannot meet the requirements. For dual-band simulators, most of the existing dual-band target simulator optical systems adopt a fully transmissive structure, in which the visible light and infrared dual-bands are coupled through a common aperture mirror group. One side of the dichroic mirror is coated with a visible light anti-reflection film, and the other side is coated with an infrared anti-reflection film. The common aperture group uses a long-wave crystal. Although this structure is relatively simple in design, it is more difficult in terms of process. First, if the infrared band exit pupil distance of the visible light and infrared dual-band simulator is 800mm and the exit pupil diameter is 80mm, in order to meet the requirement of 8° field of view, the effective diameter of the first mirror of the common aperture is 191.9mm. In addition, the infrared band needs to leave a minimum pressure edge of 5mm during optical cold processing and coating, so the first mirror of the common aperture is at least 196.9mm. And first, the mirror must transmit both visible light and infrared bands, so only ZnS material can be selected, and the large-aperture ZnS process is difficult; second, the common aperture group uses ZnS material, and the ZnS is not coated, which leads to extremely low transmittance of visible light and infrared bands, thereby affecting the irradiance of visible light and infrared bands and the simulated temperature of the infrared band; third, the inclined 45° dichroic mirror in the optical path has a large diameter, and the dichroic mirror needs to be coated. It is very difficult to coat such a large-aperture dichroic mirror, and the large-aperture ZnS and the inclined 45° dichroic mirror are both made of glass, which increases the volume and weight of the simulator. Utility Model Content

[0003] The technical problem to be solved by the utility model is to provide a visible light and long-wave infrared composite simulation optical system based on the Cassegrain structure in view of the deficiencies in the above-mentioned prior art. A visible light band simulation unit and a long-wave infrared band simulation unit are set, and the Cassegrain structure in the optical path synthesis unit is combined to form a visible light and long-wave infrared dual-band imaging simulation optical system based on the Cassegrain object-side coupling optical path. By adopting the Cassegrain object-side coupling optical path for common aperture output, the system can meet the conditions of a large field of view and a long exit pupil distance, and has the characteristics of simple structure and light weight.

[0004] In order to solve the above technical problems, the technical solution adopted by the utility model is: a visible light and long-wave infrared composite simulation optical system based on a Cassegrain structure, characterized in that it includes an optical path synthesis unit, a plane reflector, a dichroic mirror, a visible light band simulation unit, and a long-wave infrared band simulation unit arranged in sequence from left to right and from top to bottom along the main light;

[0005] The optical path synthesis unit includes a primary mirror and two secondary mirrors, the primary mirror and the secondary mirrors form a Cassegrain structure, the primary mirror is arranged on a side away from the plane reflector, the secondary mirror is arranged on a side close to the plane reflector, and the two secondary mirrors are symmetrically distributed on one side of the primary mirror;

[0006] The visible light band simulation unit comprises a visible light band simulation lens group, a prism, and a visible light image plane which are sequentially arranged from left to right along the main light direction;

[0007] The long-wave infrared band simulation unit comprises a long-wave infrared band simulation lens group and a long-wave infrared image plane which are arranged in sequence from left to right along the main light direction;

[0008] The plane reflector is obliquely arranged between the optical path synthesis unit and the visible light band simulation unit, and the dichroic mirror is obliquely arranged between the optical path synthesis unit and the long-wave infrared band simulation unit.

[0009] The above-mentioned visible light and long-wave infrared composite simulated optical system based on the Cassegrain structure is characterized in that: the visible light band simulation mirror group includes lens one, lens two, lens three, lens four, lens five, lens six, lens seven, lens eight, lens nine, and lens ten, which are arranged in sequence from left to right along the main light direction; lens one is a positive meniscus lens, lens two is a positive meniscus lens, lens three is a biconvex lens, lens four is a biconcave lens, lens five is a plano-convex lens, lens six is ​​a positive meniscus lens, lens seven is a positive meniscus lens, lens eight is a positive meniscus lens, lens nine is a biconvex lens, and lens ten is a negative meniscus lens.

[0010] The above-mentioned visible light and long-wave infrared composite simulation optical system based on the Cassegrain structure is characterized in that: the air gap between the plane reflector and lens one is 46 mm, the air gap between lens one and lens two is 2.56 mm, the air gap between lens two and lens three is 25.3 mm, the air gap between lens three and lens four is 1 mm, the air gap between lens four and lens five is 3.8 mm, the air gap between lens five and lens six is ​​1 mm, the air gap between lens six and lens seven is 1 mm, the air gap between lens seven and lens eight is 1.9 mm, the air gap between lens eight and lens nine is 53.5 mm, and the air gap between lens nine and lens ten is 19.5 mm.

[0011] The above-mentioned visible light and long-wave infrared composite simulated optical system based on the Cassegrain structure is characterized in that: the long-wave infrared band simulation lens group includes lens 11, lens 12, and lens 13 arranged in sequence from left to right along the direction of the main light; lens 11 is a positive meniscus lens, lens 12 is a positive meniscus lens, and lens 13 is a positive meniscus lens.

[0012] The above-mentioned visible light and long-wave infrared composite simulated optical system based on the Cassegrain structure is characterized in that the air gap between the dichroic mirror and lens 11 is 60 mm, the air gap between lens 11 and lens 12 is 96 mm, and the air gap between lens 12 and lens 13 is 7 mm.

[0013] The above-mentioned visible light and long-wave infrared composite simulated optical system based on the Cassegrain structure is characterized in that the air gap between the primary mirror and the secondary mirror is 260 mm.

[0014] The above-mentioned visible light and long-wave infrared composite simulated optical system based on the Cassegrain structure is characterized in that: the plane reflector and the dichroic mirror are both inclined upward along the direction of the main light, and the inclination angles of the plane reflector and the dichroic mirror are both 45°; the air gap between the plane reflector and the dichroic mirror is 175 mm.

[0015] The above-mentioned visible light and long-wave infrared composite simulated optical system based on the Cassegrain structure is characterized in that: the outer surface of the plane reflector is coated with an anti-reflection film; the outer surface of the dichroic mirror close to the optical path synthesis unit is coated with a visible light anti-reflection film, and the outer surface of the dichroic mirror away from the optical path synthesis unit is coated with a long-wave infrared anti-reflection film.

[0016] The above-mentioned visible light and long-wave infrared composite simulation optical system based on the Cassegrain structure is characterized in that the working bands of visible light and long-wave infrared in the visible light and long-wave infrared composite simulation optical system are 0.4μm~0.7μm and 8μm~12μm respectively, its field of view angle is 8°×6°, the exit pupil distance is 800mm, the exit pupil diameter Φ of the visible light band simulation unit is 25mm, and the exit pupil diameter Φ of the long-wave infrared band simulation unit is 100mm.

[0017] Compared with the prior art, the utility model has the following advantages:

[0018] 1. The utility model sets a visible light band simulation unit and a long-wave infrared band simulation unit, and combines the Cassegrain structure in the optical path synthesis unit to form a visible light and long-wave infrared dual-band imaging simulation optical system based on the Cassegrain object-side coupling optical path. By adopting the Cassegrain object-side coupling optical path for common aperture output, it can meet the conditions of a large field of view and a long exit pupil distance, and has the characteristics of simple structure and light weight.

[0019] 2. In the optical path synthesis unit of the utility model, the two reflectors are optimized in a non-spherical manner, and the obstruction ratio thereof can be reduced by adjusting the distance between the primary mirror and the secondary mirror.

[0020] In summary, the utility model sets a visible light band simulation unit and a long-wave infrared band simulation unit, and combines the Cassegrain structure in the optical path synthesis unit to form a visible light and long-wave infrared dual-band imaging simulation optical system based on the Cassegrain object-side coupled optical path. By adopting the Cassegrain object-side coupled optical path for common aperture output, the utility model can meet the conditions of a large field of view and a long exit pupil distance, and has the characteristics of simple structure and light weight.

[0021] The technical solution of the utility model is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the overall structure of the utility model.

[0023] Figure 2 It is a schematic diagram of the internal structure of the utility model.

[0024] Figure 3 This is a point diagram of the visible light band in the utility model.

[0025] Figure 4a It is a field curvature curve diagram of the visible light band in the utility model.

[0026] Figure 4b This is a distortion curve diagram of the visible light band in the utility model.

[0027] Figure 5 This is the MTF curve diagram of the visible light band in the utility model.

[0028] Figure 6 It is a color difference curve diagram of the visible light band in the utility model.

[0029] Figure 7 This is the point diagram of the utility model in the medium and long wave infrared bands.

[0030] Figure 8a This is the field curvature curve of the medium and long wave infrared band of the utility model.

[0031] Figure 8b This is the distortion curve diagram of the utility model in the medium and long wave infrared band.

[0032] Fig. 9 This is the MTF curve diagram of the utility model in the mid- and long-wave infrared bands.

[0033] Description of reference numerals:

[0034] 1—optical path synthesis unit; 2—visible light band simulation unit; 3—long-wave infrared band simulation unit;

[0035] 4—plane reflector; 5—dichroic mirror; 6—primary mirror;

[0036] 7—secondary mirror; 8—prism; 9—visible light image plane;

[0037] 10—Long-wave infrared image plane; 11—Lens 1; 12—Lens 2;

[0038] 13—lens three; 14—lens four; 15—lens five;

[0039] 16—lens six; 17—lens seven; 18—lens eight;

[0040] 19—lens nine; 20—lens ten; 21—lens eleven;

[0041] 22—Lens 12; 23—Lens 13; 24—Aperture. DETAILED DESCRIPTION

[0042] like Figures 1 to 9 As shown, the utility model includes an optical path synthesis unit 1, a plane reflector 4, a dichroic mirror 5, a visible light band simulation unit 2, and a long-wave infrared band simulation unit 3, which are arranged in sequence from left to right and from top to bottom along the main light;

[0043] The optical path synthesis unit 1 includes a primary mirror 6 and two secondary mirrors 7, wherein the primary mirror 6 and the secondary mirrors 7 form a Cassegrain structure, wherein the primary mirror 6 is arranged on a side away from the plane reflector 4, and the secondary mirror 7 is arranged on a side close to the plane reflector 4, and the two secondary mirrors 7 are symmetrically distributed on one side of the primary mirror 6;

[0044] The visible light band simulation unit 2 comprises a visible light band simulation lens group, a prism 8, and a visible light image plane 9 which are sequentially arranged from left to right along the main light direction;

[0045] The long-wave infrared band simulation unit 3 comprises a long-wave infrared band simulation lens group and a long-wave infrared image plane 10 which are arranged in sequence from left to right along the main light direction;

[0046] The plane reflector 4 is obliquely arranged between the optical path synthesis unit 1 and the visible light band simulation unit 2 , and the dichroic mirror 5 is obliquely arranged between the optical path synthesis unit 1 and the long-wave infrared band simulation unit 3 .

[0047] In actual use, by setting the visible light band simulation unit 2 and the long-wave infrared band simulation unit 3, a visible light and long-wave infrared dual-band imaging simulation optical system based on the Cassegrain object-side coupling optical path is formed in combination with the Cassegrain structure in the optical path synthesis unit 1. By adopting the Cassegrain object-side coupling optical path for common aperture output, it can meet the conditions of a large field of view and a long exit pupil distance, and has the characteristics of simple structure and light weight.

[0048] Among them, the two reflectors in the optical path synthesis unit 1 are optimized in an aspherical manner, and the obstruction ratio thereof can be reduced by adjusting the distance between the primary mirror and the secondary mirror.

[0049] In addition, when the Cassegrain structure meets the requirement of long exit pupil distance, since the secondary mirror 7 has a smaller aperture, the 45° inclined dichroic mirror 5 has a smaller aperture, which can reduce the volume and weight. In addition, both the primary mirror 6 and the secondary mirror 7 are made of conventional reflective glass materials, and the process is simple.

[0050] It should be noted that the maximum diffuse spot of the visible light band simulation unit 2 is 5.5μm, the maximum distortion is 2.0%, the full field MTF is ≥0.6@66lp / mm, and the chromatic aberration is less than 2.0μm. The maximum diffuse spot of the long-wave infrared band simulation unit 3 is 11μm, the maximum distortion is -2.5%, and the full field MTF is ≥0.35@20lp / mm.

[0051] In particular, in the visible light band simulation unit 2, the material selected for lens 1 11 is HZK1, the material selected for lens 2 12 is ZF52, the material selected for lens 3 13 is HK11, the material selected for lens 4 14 is HZF13, the material selected for lens 5 15 is HK5, the material selected for lens 6 16 is HFK61, the material selected for lens 7 17 is ZF52, the material selected for lens 8 18 is HFK61, the material selected for lens 9 19 is ZF52, and the material selected for lens 9 19 is HFK61. In the long-wave infrared band simulation unit 3, the material selected for lens 11 21 is germanium, the material selected for lens 12 22 is germanium, and the material selected for lens 13 23 is zinc sulfide.

[0052] In actual use, the visible light image is converted into a visible light target and scene image through the image conversion device, and the image passes through the visible light band simulation unit 2 and enters the plane reflector 4. After the plane reflector 4 folds its optical path, the light passes through the dichroic mirror 5 and enters the Cassegrain structure in the optical path synthesis unit 1. The Cassegrain structure is composed of two reflectors, and its main function is to output the visible light and long-wave infrared light through a common aperture. Similarly, the long-wave infrared image is converted into a long-wave infrared target and scene image through the image conversion device, and the image passes through the long-wave infrared band simulation unit 3 and enters the dichroic mirror 5, and then enters the Cassegrain structure through the dichroic mirror 5, and finally outputs after reflection from the Cassegrain structure through a common aperture.

[0053] The working principle of this system is mainly as follows: the visible light image is converted into a visible light target and scene image through the image conversion device, the image is illuminated by the light source, the light passes through the visible light band simulation mirror group and enters the plane reflector 4, after the plane reflector 4 folds its light path, it passes through the dichroic mirror 5 and enters the Cassegrain structure in the light path synthesis unit 1, and finally enters the aperture 24 after being reflected by the primary mirror 6 in the Cassegrain structure, thereby realizing the simulator's simulation of the visible light band. Similarly, the long-wave infrared image is converted into a long-wave infrared target and scene image through the image conversion device, and after the image is illuminated by the black body light source, the light passes through the long-wave infrared band simulation mirror group and enters the dichroic mirror 5, and enters the Cassegrain structure through the dichroic mirror 5, and finally enters the aperture 24 after being reflected by the primary mirror 6 in the Cassegrain structure, thereby completing the simulator's simulation of the long-wave infrared band.

[0054] In this embodiment, the visible light band simulation mirror group includes lens one 11, lens two 12, lens three 13, lens four 14, lens five 15, lens six 16, lens seven 17, lens eight 18, lens nine 19, and lens ten 20, which are arranged in sequence from left to right along the main light direction; lens one 11 is a positive meniscus lens, lens two 12 is a positive meniscus lens, lens three 13 is a double convex lens, lens four 14 is a double concave lens, lens five 15 is a plano-convex lens, lens six 16 is a positive meniscus lens, lens seven 17 is a positive meniscus lens, lens eight 18 is a positive meniscus lens, lens nine 19 is a double convex lens, and lens ten 20 is a negative meniscus lens.

[0055] In this embodiment, the air gap between the plane reflector 4 and the lens 11 is 46 mm, the air gap between the lens 11 and the lens 2 12 is 2.56 mm, the air gap between the lens 2 12 and the lens 3 13 is 25.3 mm, the air gap between the lens 3 13 and the lens 4 14 is 1 mm, the air gap between the lens 4 14 and the lens 5 15 is 3.8 mm, the air gap between the lens 5 15 and the lens 6 16 is 1 mm, the air gap between the lens 6 16 and the lens 7 17 is 1 mm, the air gap between the lens 7 17 and the lens 8 18 is 1.9 mm, the air gap between the lens 8 18 and the lens 9 19 is 53.5 mm, and the air gap between the lens 9 19 and the lens 10 20 is 19.5 mm.

[0056] In this embodiment, the long-wave infrared band simulation mirror group includes lens 11 21, lens 12 22, and lens 13 23 arranged from left to right along the main light direction; lens 11 21 is a positive meniscus lens, lens 12 22 is a positive meniscus lens, and lens 13 23 is a positive meniscus lens.

[0057] In this embodiment, the air gap between the dichroic mirror 5 and the lens 11 21 is 60 mm, the air gap between the lens 11 21 and the lens 12 22 is 96 mm, and the air gap between the lens 12 22 and the lens 13 23 is 7 mm.

[0058] In this embodiment, the air gap between the primary mirror 6 and the secondary mirror 7 is 260 mm.

[0059] In the process of material selection, since the visible light and infrared dual-band simulator has independent designs for the visible light and infrared band and the infrared band, and shares the Cassegrain structure, the Cassegrain structure uses conventional glass materials, and conventional glass materials can guarantee its surface shape and processing accuracy in large-caliber processing technology. In addition, since the field of view and exit pupil diameter of the visible light and infrared band are small, in order to avoid the secondary mirror 7 blocking the optical path of the visible light and infrared band, so that the energy of the visible light and infrared band is reduced, the secondary mirror 7 uses conventional K9 glass, and a visible light and infrared band anti-reflection film is plated on one side of the K9 glass, so that the visible light and infrared band can directly pass through the secondary mirror 7 of the Cassegrain structure, and the other side is plated with an infrared band anti-reflection film, so that the infrared band light passes through the secondary mirror 7 and is reflected to the primary mirror 6, and then enters the test object through the primary mirror 6. In the entire optical path, the visible light and infrared band are not affected by the obstruction of the Cassegrain structure. And the infrared lens group after the Cassegrain structure can correct its aberration and ensure the transmission function of its optical system. Moreover, the Seglin system is a reflective system. In the case of coating, it has a high reflectivity for the entire spectrum, which can ensure a higher energy output at the receiving end.

[0060] In this embodiment, the plane reflector 4 and the dichroic mirror 5 are both tilted upward along the main light direction, and the tilt angles of the plane reflector 4 and the dichroic mirror 5 are both 45°; the air gap between the plane reflector 4 and the dichroic mirror 5 is 175 mm.

[0061] In this embodiment, the outer surface of the plane reflector 4 is coated with an anti-reflection film; the outer surface of the dichroic mirror 5 close to the light path synthesis unit 1 is coated with a visible light anti-reflection film, and the outer surface of the dichroic mirror 5 away from the light path synthesis unit 1 is coated with a long-wave infrared anti-reflection film.

[0062] In actual use, the plane reflector 4 is coated with an anti-reflection film, and the reflectivity reaches more than 99%.

[0063] In this embodiment, the working bands of visible light and long-wave infrared in the visible light and long-wave infrared composite simulation optical system are 0.4μm~0.7μm and 8μm~12μm respectively, the field of view angle is 8°×6°, the exit pupil distance is 800mm, the exit pupil diameter Φ of the visible light band simulation unit 2 is 25mm, and the exit pupil diameter Φ of the long-wave infrared band simulation unit 3 is 100mm.

[0064] In actual use, the exit pupil distance is set to 800mm, and the Cassegrain structure is adopted in the common aperture part, so the imaging requirements of the simulator can be met by one-time imaging for both the visible light and long-wave infrared parts, and one-time imaging can greatly shorten the size of the simulator.

[0065] The above is only a preferred embodiment of the present invention and does not constitute any limitation to the present invention. Any simple modification, change and equivalent structural change made to the above embodiments according to the technical essence of the present invention shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A composite optical system of visible light and long-wave infrared simulation based on Cassegrain structure, characterized by: It comprises an optical path synthesis unit (1), a plane reflector (4), a dichroic mirror (5), a visible light band simulation unit (2), and a long-wave infrared band simulation unit (3) which are arranged in sequence from left to right and from top to bottom along the main light beam; The optical path synthesis unit (1) comprises a primary mirror (6) and two secondary mirrors (7), wherein the primary mirror (6) and the secondary mirrors (7) form a Cassegrain structure, wherein the primary mirror (6) is arranged on a side away from the plane reflector (4), and the secondary mirror (7) is arranged on a side close to the plane reflector (4), and the two secondary mirrors (7) are symmetrically distributed on one side of the primary mirror (6); The visible light band simulation unit (2) comprises a visible light band simulation lens group, a prism (8), and a visible light image plane (9) which are arranged in sequence from left to right along the main light direction; The long-wave infrared band simulation unit (3) comprises a long-wave infrared band simulation lens group and a long-wave infrared image plane (10) which are arranged in sequence from left to right along the main light direction; The plane reflector (4) is arranged obliquely between the light path synthesis unit (1) and the visible light band simulation unit (2), and the dichroic mirror (5) is arranged obliquely between the light path synthesis unit (1) and the long-wave infrared band simulation unit (3).

2. The visible light and long-wave infrared composite simulation optical system based on the Cassegrain structure according to claim 1, characterized in that: The visible light band simulation lens group comprises a lens 1 (11), a lens 2 (12), a lens 3 (13), a lens 4 (14), a lens 5 (15), a lens 6 (16), a lens 7 (17), a lens 8 (18), a lens 9 (19), and a lens 10 (20) which are arranged in sequence from left to right along the main light direction; the lens 1 (11) is a positive meniscus lens, the lens 2 (12) is a positive meniscus lens, the lens 3 (13) is a biconvex lens, the lens 4 (14) is a biconcave lens, the lens 5 (15) is a plano-convex lens, the lens 6 (16) is a positive meniscus lens, the lens 7 (17) is a positive meniscus lens, the lens 8 (18) is a positive meniscus lens, the lens 9 (19) is a biconvex lens, and the lens 10 (20) is a negative meniscus lens.

3. The visible light and long-wave infrared composite simulation optical system based on the Cassegrain structure according to claim 2, characterized in that: The air gap between the plane reflector (4) and the lens 1 (11) is 46 mm, the air gap between the lens 1 (11) and the lens 2 (12) is 2.56 mm, the air gap between the lens 2 (12) and the lens 3 (13) is 25.3 mm, the air gap between the lens 3 (13) and the lens 4 (14) is 1 mm, the air gap between the lens 4 (14) and the lens 5 (15) is 3.8 mm, the air gap between the lens 5 (15) and the lens 6 (16) is 1 mm, the air gap between the lens 6 (16) and the lens 7 (17) is 1 mm, the air gap between the lens 7 (17) and the lens 8 (18) is 1.9 mm, the air gap between the lens 8 (18) and the lens 9 (19) is 53.5 mm, and the air gap between the lens 9 (19) and the lens 10 (20) is 19.5 mm.

4. The visible light and long-wave infrared composite simulation optical system based on the Cassegrain structure according to claim 3, characterized in that: The long-wave infrared band simulation lens group comprises a lens eleven (21), a lens twelve (22), and a lens thirteen (23) which are arranged in sequence from left to right along the main light direction; the lens eleven (21) is a positive meniscus lens, the lens twelve (22) is a positive meniscus lens, and the lens thirteen (23) is a positive meniscus lens.

5. The visible light and long-wave infrared composite simulation optical system based on the Cassegrain structure according to claim 4, characterized in that: The air gap between the dichroic mirror (5) and the lens eleven (21) is 60 mm, the air gap between the lens eleven (21) and the lens twelve (22) is 96 mm, and the air gap between the lens twelve (22) and the lens thirteen (23) is 7 mm.

6. The visible light and long-wave infrared composite simulation optical system based on Cassegrain structure according to claim 1, characterized in that: The air gap between the primary mirror (6) and the secondary mirror (7) is 260 mm.

7. The visible light and long-wave infrared composite simulation optical system based on Cassegrain structure according to claim 1, characterized in that: The plane reflector (4) and the dichroic mirror (5) are both inclined upward along the direction of the main light, and the inclination angles of the plane reflector (4) and the dichroic mirror (5) are both 45°; and the air gap between the plane reflector (4) and the dichroic mirror (5) is 175 mm.

8. The visible light and long-wave infrared composite simulation optical system based on Cassegrain structure according to claim 1, characterized in that: The outer surface of the plane reflector (4) is coated with an anti-reflection film; the outer surface of the dichroic mirror (5) close to the light path synthesis unit (1) is coated with a visible light anti-reflection film, and the outer surface of the dichroic mirror (5) away from the light path synthesis unit (1) is coated with a long-wave infrared anti-reflection film.

9. The visible light and long-wave infrared composite simulation optical system based on Cassegrain structure according to claim 1, characterized in that: The working bands of visible light and long-wave infrared in the visible light and long-wave infrared composite simulation optical system are 0.4 μm~0.7 μm and 8 μm~12 μm respectively, the field of view angle is 8°×6°, the exit pupil distance is 800 mm, the exit pupil diameter Φ of the visible light band simulation unit (2) is 25 mm, and the exit pupil diameter Φ of the long-wave infrared band simulation unit (3) is 100 mm.

Images