Visible light / short wave infrared dual-band common-aperture optical system

Abstract

The invention relates to a visible light / short-wave infrared dual-band common-caliber optical system, which comprises a common-caliber part, a plane beam splitter, a visible light channel subsystem and a short-wave infrared channel subsystem, and is characterized in that the common-caliber part is positioned at the foremost end of the optical system and consists of a primary reflector and a secondary reflector which are coaxially arranged; the plane beam splitter is located on a light path behind the secondary reflector, full-wave-band light from an object side is reflected by the primary reflector and the secondary reflector in sequence, then reaches the plane beam splitter to be split, and then enters the visible light channel subsystem and the short-wave infrared channel subsystem to be imaged in different wave bands, and the optical system achieves dual-wave-band common caliber. According to the invention, the design of long focal length and large aperture of the dual-band system is realized, the target detection / identification capability of the system is improved, the system has the advantages of high spatial resolution, long operating distance and high identification probability, meanwhile, the system structure is effectively simplified, the system volume is reduced, the installation and adjustment difficulty is reduced, and a relatively low obscuration ratio and relatively high imaging quality are realized.

Description

Technical Field

[0001] The invention relates to the field of optical imaging systems, and in particular to a visible light / short-wave infrared dual-band common aperture optical system. Background Art

[0002] In order to improve the target detection / recognition capability, the optoelectronic payload is required to have the characteristics of high spatial resolution, long range, and high recognition probability. The focal length of the optical system determines the detail resolution capability of the acquired target; its relative aperture determines the exposure time of the detector. Therefore, the optical systems of optoelectronic payloads are developing in the direction of long focal length and large relative aperture.

[0003] With the development of camouflage technology, the difficulty of detecting and identifying targets is also increasing. The detection system using traditional single-band such as visible light and infrared has limitations in use, and it is difficult to quickly and accurately intercept and track targets under complex background conditions. Since the optical characteristics of targets in different spectral bands are quite different, therefore, in combination with the imaging characteristics of each band, the optoelectronic load working in multiple bands can obtain sufficient and useful information, and can effectively identify the target from a large number of images, which has irreplaceable advantages in improving recognition probability, camouflage recognition, feature resolution, etc.

[0004] Light in the short-wave infrared band (0.9-1.7 μm) cannot be directly observed by the human eye because it is beyond the visible light spectrum, but its interaction with objects is the same as that of visible light. Compared with thermal imagers that can only detect warm objects against a cold background, images formed using reflected light from short-wave infrared have shadows and contrast, and the resolution and details of the images are comparable to those of visible light.

[0005] In remote sensing, it is used to detect the earth's mineral resources, monitor the moisture content of soil and vegetation and changes in atmospheric composition, estimate crop yields and prevent and reduce disasters, etc. In commercial applications, it can be used as various short-wave infrared spectrometers, short-wave infrared flaw detection, short-wave infrared content determination, and online automatic chip detection in the semiconductor device manufacturing industry, etc. It has also begun to be used more and more in the biomedical field. Since green plants have a strong ability to reflect near-infrared and short-wave infrared, while artificial green paints are weak, they can be used to identify camouflage. In addition, short-wave infrared imagers can detect 1.06μm lasers for ranging or illumination indication and 1.57μm lasers that are safe for the human eye, so it is very necessary to design and develop short-wave infrared optical systems.

[0006] At present, in China's multi-band optical systems, different band systems are designed separately and then assembled together to form a multi-band optical system. Specifically, the existing visible light-short-wave infrared optical dual-band system is a combination of two separate systems: the visible light system and the short-wave infrared system. This results in a relatively large system size, which is not conducive to miniaturization and is difficult to assemble and adjust. Summary of the invention

[0007] In order to solve the problems existing in the prior art, the present invention provides a visible light / shortwave infrared dual-band common aperture optical system, which realizes that the dual bands share one front-end optical aperture, realizes the long focal length and large aperture design of the dual-band system, thereby improving the system's detection / recognition ability for the target, simplifying the system structure, and reducing the difficulty of installation and adjustment.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A visible light / short-wave infrared dual-band co-aperture optical system comprises a co-aperture part, a plane beam splitter, a visible light channel subsystem and a short-wave infrared channel subsystem. The co-aperture part is located at the front end of the optical system, and comprises a primary reflector and a secondary reflector arranged coaxially. The plane beam splitter is located on the optical path behind the secondary reflector. The normal of the plane beam splitter forms an angle of 45° with the optical axis. Full-band light from the object side is reflected by the primary reflector and the secondary reflector in sequence and then reaches the plane beam splitter. The plane beam splitter splits the light and then enters the visible light channel subsystem and the short-wave infrared channel subsystem respectively for imaging in different bands.

[0010] Furthermore, the visible light channel subsystem is located on the reflected light path of the plane beam splitter, and is composed of a first plane reflector, a first double convex positive lens, a first meniscus positive lens, a second meniscus positive lens, a first meniscus negative lens, and a first double concave negative lens, wherein the first plane reflector is placed at an angle of 45° to the optical axis and is parallel to the plane beam splitter.

[0011] Furthermore, the concave surface of the second meniscus positive lens is arranged toward the visible light image plane.

[0012] Furthermore, the first biconvex positive lens and the first meniscus positive lens form a first cemented lens I, and the first meniscus negative lens and the first biconcave negative lens form a second cemented lens II.

[0013] Furthermore, the short-wave infrared channel subsystem is located on the transmission light path of the plane beam splitter, and is composed of a second plane reflector, a second biconvex positive lens, a third biconvex positive lens, a second biconcave negative lens, a third biconcave negative lens, and a second meniscus negative lens. The second plane reflector is placed at 45° to the optical axis and is perpendicular to the plane beam splitter.

[0014] Furthermore, the third biconvex positive lens and the second biconcave negative lens form a third cemented lens III, and the third biconcave negative lens and the second meniscus negative lens form a fourth cemented lens IV.

[0015] Furthermore, the reflecting surface of the primary reflector is a parabola, and the reflecting surface of the secondary reflector is a hyperbolic surface.

[0016] Furthermore, the material of the primary reflector is microcrystalline glass, and the material of the secondary reflector is quartz. The optical material of the plane beam splitter is quartz, the optical material of the first plane reflector is quartz, the optical material of the first double convex positive lens is H-ZK11, the optical material of the first meniscus positive lens is H-ZF2, the optical material of the second meniscus positive lens is H-LAK10, the optical material of the first meniscus negative lens is H-ZF62, and the optical material of the first double concave negative lens is H-ZLAF89L. The optical material of the second plane reflector is quartz, the optical material of the second double convex positive lens is H-LAF54, the optical material of the third double convex positive lens is H-ZLAF3, the optical material of the second double concave negative lens is H-ZF62, the optical material of the third double concave negative lens is H-LAF54, and the optical material of the second meniscus negative lens is H-ZK9B.

[0017] Furthermore, the working band of the optical system includes the visible light band of 0.38μm to 0.76μm and the short-wave infrared band of 0.9μm to 1.7μm. In both bands, the focal length is 1200mm, and F # : 6.0, where F # The calculation formula is f / D, where f is the focal length of the optical system and D is the diameter of the entrance pupil.

[0018] Furthermore, the obstruction ratio of the optical system is ≤0.25.

[0019] Beneficial effects:

[0020] The dual-band common-aperture optical system provided by the present invention solves the problems of large volume, difficulty in achieving long focal length and large relative aperture caused by the combined assembly of traditional multi-band systems after separate design, and realizes that the visible light and short-wave infrared dual-bands share a front-end optical aperture, and then use a beam splitter to split the light and enter the subsequent visible light and short-wave infrared channels for imaging respectively, thereby simplifying the system structure and reducing the system volume. Compared with the traditional combined dual-band system, the parallelism adjustment of the optical axes of the two is omitted, the difficulty of system installation and adjustment is reduced, and the correction error that may be caused by the use of multiple optical systems is avoided.

[0021] The present invention realizes a system obstruction ratio of ≤0.25 by reasonably distributing the optical power of the primary reflector and the secondary reflector, effectively reducing the influence of the central obstruction on the modulation transfer function (MTF) and the energy equivalent F number of the optical system, and ensuring that the system has high imaging quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Light path diagram of the optical system of the present invention;

[0023] Figure 2The transfer function diagram of the optical system of the present invention in the visible light band;

[0024] Figure 3 Point diagram of the optical system of the present invention in the visible light band;

[0025] Figure 4 Field curvature and distortion diagram of the optical system of the present invention in the visible light band;

[0026] Figure 5 The transfer function diagram of the optical system of the present invention in the short-wave infrared band;

[0027] Figure 6 The spot diagram of the optical system of the present invention in the short-wave infrared band;

[0028] Figure 7 Field curvature and distortion diagram of the optical system of the present invention in the short-wave infrared band.

[0029] In the figure, 1 is the main reflector, 2 is the secondary reflector, 3 is the plane beam splitter, 4 is the first plane reflector, 5 is the first biconvex positive lens, 6 is the first meniscus positive lens, 7 is the second meniscus positive lens, 8 is the first meniscus negative lens, 9 is the first biconcave negative lens, 10 is the image plane of the visible light subsystem, 11 is the second plane reflector, 12 is the second biconvex positive lens, 13 is the third biconvex positive lens, 14 is the second biconcave negative lens, 15 is the third biconcave negative lens, 16 is the second meniscus negative lens, and 17 is the image plane of the shortwave infrared subsystem. DETAILED DESCRIPTION

[0030] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] In order to make the above features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings, which are only examples and are not drawn strictly to scale.

[0032] In the description of the present invention, it is necessary to understand that if there are terms such as "upper", "lower", "front", "back", "left", "right", etc. to indicate directions or positional relationships, they only correspond to the drawings of the present application and are for the convenience of describing the present invention, rather than indicating or implying that the device or element referred to must have a specific direction.

[0033] The terms "first", "second" and "third" are used for descriptive purposes only and refer to the order in which lenses of this type appear. They are distinguished in the description and should not be understood as indicating or implying relative importance.

[0034] The dual-band common aperture optical system of the present invention is mainly used in optoelectronic pods, such as Figure 1As shown, a dual-band common-aperture optical system for an optoelectronic pod includes a common-aperture part, a plane beam splitter, a visible light channel subsystem, and a short-wave infrared channel subsystem; the visible light and short-wave infrared dual bands share a front-end optical aperture, which is then split using the beam splitter and enter subsequent visible light and short-wave infrared channels for imaging in different bands.

[0035] The common aperture part, i.e., the dual-band shared part, is located at the front end of the optical system, and includes a primary reflector 1 and a secondary reflector 2. The primary reflector 1 and the secondary reflector 2 are coaxially arranged, and a plane beam splitter 3 is located on the optical path behind the secondary reflector 2. The normal of the plane beam splitter 3 forms an angle of 45° with the optical axis. The full-band light from the object side is reflected by the primary reflector 1 and the secondary reflector 2 in sequence and then reaches the plane beam splitter 3. The plane beam splitter 3 splits the light and then enters the visible light channel subsystem and the short-wave infrared channel subsystem for imaging in different bands.

[0036] The visible light channel subsystem is located on the reflected light path of the plane beam splitter 3, and is composed of a first plane reflector 4, a first double convex positive lens 5, a first meniscus positive lens 6, a second meniscus positive lens 7, a first meniscus negative lens 8, and a first double concave negative lens 9. The normal of the first plane reflector 4 forms an angle of 45° with the optical axis, the first plane reflector 4 is parallel to the plane beam splitter 3, and the concave surface of the second meniscus positive lens 7 is arranged toward the visible light image plane 10.

[0037] The short-wave infrared channel subsystem is located on the transmission light path of the plane beam splitter 3, and is composed of a second plane reflector 11, a second biconvex positive lens 12, a third biconvex positive lens 13, a second biconcave negative lens 14, a third biconcave negative lens 15, and a second meniscus negative lens 16. The second plane reflector 11 is placed at an angle of 45° to the optical axis (i.e., the normal of the second plane reflector 11 forms an angle of 45° with the optical axis) and is perpendicular to the plane beam splitter 3, so that the transmitted light of the plane beam splitter 3 can be deflected by 90° and then enters the second biconvex positive lens 12.

[0038] The optical system is provided with a plurality of cemented lenses, wherein a first biconvex positive lens 5 and a first meniscus positive lens 6 form a first cemented lens I, a first meniscus negative lens 8 and a first biconcave negative lens 9 form a second cemented lens II, a third biconvex positive lens 13 and a second biconcave negative lens 14 form a third cemented lens III, and a third biconcave negative lens 15 and a second meniscus negative lens 16 form a fourth cemented lens IV.

[0039] The present invention realizes a dual-band common aperture design through a primary reflector 1, a secondary reflector 2 and a plane beam splitter 3, and folds the optical path through the reflector to realize system miniaturization, which is suitable for use in an optoelectronic pod; wherein the plane beam splitter 3 is placed at 45° to the optical axis, and the first plane reflector 4 is placed at 45° to the optical axis; the plane beam splitter 3 is placed parallel to the first plane reflector 4; the second plane reflector 11 is placed at an angle of 90° to the plane beam splitter 3, and after reflection by the second plane reflector 11, the propagation direction of the light changes by 90°.

[0040] In the visible light / short-wave infrared dual-band common-aperture optical system, the light transmission path of the visible light part is as follows: the full-band light from the object side is reflected by the main reflector 1 and reaches the secondary reflector 2, and then reaches the plane beam splitter 3 after being reflected by the secondary reflector 2. The visible light band light of 0.38μm to 0.76μm is reflected by the plane beam splitter 3 and reaches the first plane reflector 4, and then reaches the first cemented lens I composed of the first double convex positive lens 5 and the first meniscus positive lens 6 after being reflected by the first plane reflector 4, and then reaches the second meniscus positive lens 7 after being converged by the first cemented lens I, and then reaches the second meniscus positive lens 7 after being converged by the second meniscus positive lens 7, and then reaches the second cemented lens II composed of the first meniscus negative lens 8 and the first double concave negative lens 9, and is imaged on the visible light image plane 10 after being diverged by the second cemented lens II.

[0041] The light transmission path of the short-wave infrared part is as follows: the full-band light from the object side is reflected by the main reflector 1 and reaches the secondary reflector 2, and then reaches the plane beam splitter 3 after being reflected by the secondary reflector 2. The short-wave infrared light of 0.9μm to 1.7μm passes through the plane beam splitter 3 and reaches the second plane reflector 11, and then reaches the second biconvex positive lens 12 after being reflected by the second plane reflector 11. After being converged by the second biconvex positive lens 12, it reaches the third cemented lens III composed of the third biconvex positive lens 13 and the second biconcave negative lens 14, and then converged by the third cemented lens III and reaches the fourth cemented lens IV composed of the third biconcave negative lens 15 and the second meniscus negative lens 16, and then is imaged on the short-wave infrared image plane 17 after being diverged by the fourth cemented lens IV.

[0042] The focal length of each lens in the system needs to meet the following conditions:

[0043] The main reflector 1 meets the following conditions: 0.20≤f1 / f≤0.30, where f is the effective focal length of the optical system and f1 is the effective focal length of the main reflector 1;

[0044] The secondary reflector 2 satisfies the following condition: 0.04≤f2 / f≤0.05, where f is the effective focal length of the optical system and f2 is the effective focal length of the secondary reflector 2;

[0045] The first biconvex positive lens 5 satisfies the following conditions: 0.17≤f5 / f≤0.19, Nd5=1.6385, Vd5=55.45, where f is the effective focal length of the optical system, f5 is the effective focal length of the first biconvex positive lens 5, Nd5 is the refractive index of the d-line of the material of the first biconvex positive lens 5, and Vd5 is the d-line Abbe constant of the material of the first biconvex positive lens 5;

[0046] The first meniscus positive lens 6 satisfies the following conditions: 0.18≤f6 / f≤0.20, Nd6=1.6727, Vd6=32.17, wherein f is the effective focal length of the optical system, f6 is the effective focal length of the first meniscus positive lens 6, Nd6 is the refractive index of the d-line material of the first meniscus positive lens 6, and Vd6 is the d-line Abbe constant of the material of the first meniscus positive lens 6;

[0047] The second meniscus positive lens 7 satisfies the following conditions: 0.06≤f7 / f≤0.07, Nd7=1.6511, Vd7=55.89, wherein f is the effective focal length of the optical system, f7 is the effective focal length of the second meniscus positive lens 7, Nd7 is the refractive index of the d-line material of the second meniscus positive lens 7, and Vd7 is the d-line Abbe constant of the material of the second meniscus positive lens 7;

[0048] The first meniscus negative lens 8 satisfies the following conditions: -0.40≤f8 / f≤-0.20, Nd8=1.92286, Vd8=20.88, wherein f is the effective focal length of the optical system, f8 is the effective focal length of the first meniscus negative lens 8, Nd8 is the refractive index of the d-line material of the first meniscus negative lens 8, and Vd8 is the d-line Abbe constant of the material of the first meniscus negative lens 8;

[0049] The first biconcave negative lens 9 satisfies the following conditions: -0.02≤f9 / f≤-0.01, Nd9=1.9537, Vd9=32.31, wherein f is the effective focal length of the optical system, f9 is the effective focal length of the first biconcave negative lens 9, Nd9 is the refractive index of the d-line material of the first biconcave negative lens 9, and Vd9 is the d-line Abbe constant of the material of the first biconcave negative lens 9;

[0050] The second biconvex positive lens 12 satisfies the following conditions: 0.07≤f 12 / f≤0.08,Nd 12 =1.7995, Vd 12 =42.24, where f is the effective focal length of the optical system, f 12 is the effective focal length of the second biconvex positive lens 12, Nd 12 is the refractive index of the material of the second biconvex positive lens 12 at line d, Vd 12 is the d-line Abbe constant of the material of the second biconvex positive lens 12;

[0051] The third biconvex positive lens 13 satisfies the following condition: 0.10≤f 13 / f≤0.20,Nd 13 =1.8554, Vd 13 =36.59, where f is the effective focal length of the optical system, f 13 is the effective focal length of the third biconvex positive lens 13, Nd 13 is the refractive index of the material of the third biconvex positive lens 13 at line d, Vd 13 is the d-line Abbe constant of the material of the third biconvex positive lens 13.

[0052] The second biconcave negative lens 14 satisfies the following condition: -0.06≤f 14 / f≤-0.05,Nd 14 =1.92286, Vd 14 =20.88, where f is the effective focal length of the optical system, f 14 is the effective focal length of the second biconcave negative lens 14, Nd 14 is the refractive index of the material of the second biconcave negative lens 14 at d line, Vd 14 is the d-line Abbe constant of the material of the second biconcave negative lens 14;

[0053] The third biconcave negative lens 15 satisfies the following condition: -0.30≤f 15 / f≤-0.20,Nd 15 =1.7995, Vd 15 =42.24, where f is the effective focal length of the optical system, f 15 is the effective focal length of the third biconcave negative lens 15, Nd 15 is the refractive index of the material of the third biconcave negative lens 15 at line d, Vd 15 is the d-line Abbe constant of the material of the third biconcave negative lens 15;

[0054] The second meniscus negative lens 16 satisfies the following condition: -0.03≤f 16 / f≤-0.02,Nd 16 =1.6204, Vd 16 =60.34, where f is the effective focal length of the optical system, f 16 is the effective focal length of the second meniscus negative lens 16, Nd 16 is the refractive index of the material of the second meniscus negative lens 16 at line d, Vd 16 is the d-line Abbe constant of the material of the second meniscus negative lens 16 .

[0055] Preferably, the optical material of the plane beam splitter 3 is quartz, the optical material of the first plane reflector 4 is quartz, the optical material of the first biconvex positive lens 5 is H-ZK11, the optical material of the first meniscus positive lens 6 is H-ZF2, the optical material of the second meniscus positive lens 7 is H-LAK10, the optical material of the first meniscus negative lens 8 is H-ZF62, and the optical material of the first biconcave negative lens 9 is H-ZLAF89L. The optical material of the second plane reflector 11 is quartz, the optical material of the second biconvex positive lens 12 is H-LAF54, the optical material of the third biconvex positive lens 13 is H-ZLAF3, the optical material of the second biconcave negative lens 14 is H-ZF62, the optical material of the third biconcave negative lens 15 is H-LAF54, and the optical material of the second meniscus negative lens 16 is H-ZK9B.

[0056] In this embodiment, the technical indicators achieved by the optical system are: band: 0.38μm~0.76μm (visible light), 0.9μm~1.7μm (short-wave infrared); focal length: 1200mm (visible light), 1200mm (medium-wave infrared); F#: 6.0 (visible light), 6.0 (short-wave infrared), obscuration ratio: ≤0.25.

[0057] As shown in Table 1, a set of specific parameters of the visible light subsystem of this embodiment is given, which includes the surface type, radius of curvature, thickness, caliber, and material of each lens. Among them, the units of the radius of curvature and thickness of the lens are both mm, and the radius of curvature of the spherical surface and the aspherical surface refers to the radius of curvature at the intersection of the lens surface and the optical axis. The "radius" in Table 1 represents the radius of curvature of the surface, and its positive and negative determination principle is: the intersection of the surface and the main optical axis is taken as the starting point, and the center of the curved surface of the surface is taken as the end point. If the direction of the connecting line is the same as the direction of light propagation, it is positive, otherwise it is negative. If the surface is a plane, the radius of curvature of the surface is infinite; the "thickness" in Table 1 gives the distance between two adjacent surfaces on the optical axis, and its positive and negative determination principle is: take the vertex of the current surface as the starting point, and the vertex of the next surface as the end point. If the direction of the connecting line is the same as the direction of light propagation, it is positive, otherwise it is negative. If the material between the two surfaces is lens material, then the thickness represents the lens thickness, and if there is no material between the two surfaces, it represents the air gap between the two lenses.

[0058] Table 1 Detailed data of the optical system of the visible light subsystem of the embodiment of the present invention

[0059] As shown in Table 2, a set of specific parameters of the short-wave infrared subsystem in this embodiment is given, in units of mm. It includes the surface type, radius of curvature, thickness, caliber, and material of each lens. Among them, the units of the radius of curvature and thickness of the lens are both mm, and the radius of curvature of the spherical and aspherical surfaces refer to the radius of curvature at the intersection of the lens surface and the optical axis. The "radius" in Table 2 represents the radius of curvature of the surface, and its positive and negative determination principle is: the intersection of the surface and the main optical axis is taken as the starting point, and the center of the curved surface of the surface is taken as the end point. If the direction of the connecting line is the same as the direction of light propagation, it is positive, otherwise it is negative. If the surface is a plane, the radius of curvature of the surface is infinite; the "thickness" in Table 2 gives the distance between two adjacent surfaces on the optical axis, and its positive and negative determination principle is: take the vertex of the current surface as the starting point, and the vertex of the next surface as the end point. If the direction of the connecting line is the same as the direction of light propagation, it is positive, otherwise it is negative. If the material between the two surfaces is infrared material, the thickness represents the lens thickness, and if there is no material between the two surfaces, it represents the air gap between the two lenses. Table 2 Detailed data of the optical system of the short-wave infrared subsystem of the embodiment of the present invention

[0060] To verify the imaging quality of the above optical system, optical design software simulation was performed, such as Figure 2 As shown in the figure, it is the transfer function diagram of the optical system in the visible light band. When the spatial frequency is 145lp / mm corresponding to the selected detector with a pixel size of 3.45μm, the system transfer function is as low as 0.4, indicating that the imaging performance of the system is excellent. Figure 3 As shown in the figure, it is a spot diagram of the optical system in the visible light band. The spot diameter is smaller than the pixel size, indicating that the imaging performance of the system is excellent. Figure 4 As shown, the field curvature and distortion diagram of the optical system in the visible light band, the system distortion is less than 2.0%.

[0061] like Figure 5 As shown in the figure, it is the transfer function diagram of the short-wave infrared band optical system. When the spatial frequency corresponding to the selected detector with a pixel size of 15μm is 33lp / mm, the system transfer function is as low as 0.5, indicating that the system has excellent imaging performance. Figure 6 As shown in the figure, it is a spot diagram of the optical system in the short-wave infrared band. The spot diameter is smaller than the pixel size, indicating that the imaging performance of the system is excellent. Figure 7 As shown, the field curvature and distortion diagram of the short-wave infrared optical system, the system distortion is less than 2.5%.

[0062] Therefore, the dual-band common aperture optical system of the present invention realizes that the visible light and short-wave infrared dual bands share a front optical aperture, and uses a plane beam splitter to split the light, which enters the subsequent visible light and short-wave infrared channels for imaging respectively, realizing a long focal length and large aperture design of the dual-band system, thereby improving the system's detection / recognition capability for targets. It has the advantages of high spatial resolution, long action distance, and high recognition probability, while reducing the system volume, simplifying the system structure, and reducing the difficulty of system installation and adjustment. Through the reasonable distribution of the focal length of the primary reflector and the secondary reflector, the system obstruction ratio is achieved to be ≤0.25, which effectively reduces the influence of the central obstruction on the modulation transfer function (MTF) and energy equivalent F number of the optical system.

[0063] The above are only preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed as above in preferred embodiments, it is not intended to limit the present invention. Any technician familiar with the profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A visible light / shortwave infrared dual-band common aperture optical system, characterized in that: The optical system is composed of a common aperture part, a plane beam splitter (3), a visible light channel subsystem and a short-wave infrared channel subsystem. The common aperture part is located at the front end of the optical system and is composed of a coaxially arranged primary reflector (1) and a secondary reflector (2). The plane beam splitter (3) is located on the optical path behind the secondary reflector (2). The normal of the plane beam splitter (3) forms an angle of 45° with the optical axis. Full-band light from the object side is reflected by the primary reflector (1) and the secondary reflector (2) in sequence and then reaches the plane beam splitter (3). The plane beam splitter (3) splits the light and then enters the visible light channel subsystem and the short-wave infrared channel subsystem respectively to perform imaging of different bands.

2. A visible light / shortwave infrared dual-band common aperture optical system according to claim 1, characterized in that: The visible light channel subsystem is located on the reflection light path of the plane beam splitter (3), and is composed of a first plane reflector (4), a first double convex positive lens (5), a first meniscus positive lens (6), a second meniscus positive lens (7), a first meniscus negative lens (8), and a first double concave negative lens (9), wherein the first plane reflector (4) is placed at an angle of 45° to the optical axis and is parallel to the plane beam splitter (3).

3. A visible light / shortwave infrared dual-band common aperture optical system according to claim 2, characterized in that: The concave surface of the second meniscus positive lens (7) is arranged toward the visible light image plane (10).

4. The visible light / shortwave infrared dual-band common aperture optical system according to claim 2, characterized in that: The first double convex positive lens (5) and the first meniscus positive lens (6) form a first cemented lens I, and the first meniscus negative lens (8) and the first double concave negative lens (9) form a second cemented lens II.

5. The visible light / shortwave infrared dual-band common aperture optical system according to claim 1, characterized in that: The short-wave infrared channel subsystem is located on the transmission light path of the plane beam splitter (3), and is composed of a second plane reflector (11), a second biconvex positive lens (12), a third biconvex positive lens (13), a second biconcave negative lens (14), a third biconcave negative lens (15), and a second meniscus negative lens (16). The second plane reflector (11) is placed at 45 degrees to the optical axis and is perpendicular to the plane beam splitter (3).

6. The visible light / shortwave infrared dual-band common aperture optical system according to claim 5, characterized in that: The third biconvex positive lens (13) and the second biconcave negative lens (14) form a third cemented lens III, and the third biconcave negative lens (15) and the second meniscus negative lens (16) form a fourth cemented lens IV.

7. The visible light / shortwave infrared dual-band common aperture optical system according to claim 1, characterized in that: The reflecting surface of the primary reflector (1) is a parabola, and the reflecting surface of the secondary reflector (2) is a hyperbolic surface.

8. The visible light / shortwave infrared dual-band common aperture optical system according to claim 7, characterized in that: The material of the primary reflector (1) is microcrystalline glass, and the material of the secondary reflector (2) is quartz.

9. The visible light / shortwave infrared dual-band common aperture optical system according to claim 1, characterized in that: The working band of this optical system is the visible light band of 0.38μm to 0.76μm and the short-wave infrared band of 0.9μm to 1.7μm. In both bands, the focal length is 1200mm. F # : 6.0, of which, F # The calculation formula is f / D , f is the focal length of the optical system, D is the entrance pupil diameter.

10. The visible light / shortwave infrared dual-band common aperture optical system according to claim 1, characterized in that: The obstruction ratio of the optical system is ≤0.25.

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