A Visible / Shortwave Infrared Dual-Band Common Aperture Optical System

Abstract

This invention relates to a visible light / shortwave infrared dual-band common-aperture optical system, comprising a common-aperture section, a planar beam splitter, a visible light channel subsystem, and a shortwave infrared channel subsystem. The common-aperture section is located at the front end of the optical system and consists of a primary mirror and a secondary mirror arranged coaxially. The planar beam splitter is located in the optical path behind the secondary mirror. Full-band light from the object side is reflected sequentially by the primary and secondary mirrors before reaching the planar beam splitter, where it is split and then enters the visible light channel subsystem and the shortwave infrared channel subsystem for imaging in different bands. The optical system achieves dual-band common-aperture, realizing a long focal length and large aperture design for the dual-band system, improving the system's target detection / identification capability, and has the advantages of high spatial resolution, long operating distance, and high identification probability. At the same time, it effectively simplifies the system structure, reduces the system size, reduces assembly and adjustment difficulty, and achieves a low obstruction ratio and high imaging quality.

Description

Technical Field

[0001] This invention relates to the field of optical imaging systems, and more specifically to a dual-band common aperture optical system for visible light and short-wave infrared. Background Technology

[0002] To improve target detection / identification capabilities, optoelectronic payloads are required to possess characteristics such as high spatial resolution, long operating range, and high identification probability. The focal length of the optical system determines the ability to acquire detailed target resolution; its relative aperture determines the exposure time of the detector. Therefore, the optical systems of optoelectronic payloads are developing towards longer focal lengths and larger relative apertures.

[0003] With the development of camouflage technology, the difficulty of detecting and identifying targets is constantly increasing. Traditional detection systems using single-band wavelengths such as visible light and infrared have limitations and struggle to quickly and accurately intercept and track targets in complex background environments. Since the optical characteristics of targets vary significantly across different spectral bands, photoelectric payloads operating in multiple bands can acquire sufficient and useful information by combining the imaging characteristics of each band. This allows for the effective identification of targets from a large number of images, offering irreplaceable advantages in improving recognition probability, camouflage identification, and feature resolution.

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

[0005] In remote sensing, short-wave infrared (SWI) technology is used to detect Earth's mineral resources, monitor changes in soil and vegetation moisture content and atmospheric composition, estimate crop yields, and prevent and mitigate disasters. Commercially, it can be used in various short-wave infrared spectrometers, for short-wave infrared flaw detection, for short-wave infrared content determination, and for online automatic chip inspection in the semiconductor manufacturing industry. It is also increasingly being applied in the biomedical field. Because green plants strongly reflect near-infrared and short-wave infrared light, while artificial green paint reflects very little, it can be used to identify camouflage. Furthermore, 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; therefore, the design and development of short-wave infrared optical systems is essential.

[0006] Currently, in China, multi-band optical systems are designed separately for different bands and then assembled together to form a multi-band optical system. Specifically, the existing visible light-shortwave infrared dual-band optical system is a combination of two separate systems: a visible light system and a shortwave 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] To address the problems existing in the prior art, this invention provides a visible light / shortwave infrared dual-band common aperture optical system, which realizes the sharing of a single front-end optical aperture for both bands, and achieves a long focal length and large aperture design for the dual-band system, thereby improving the system's target detection / identification capability, simplifying the system structure, and reducing assembly and adjustment difficulty.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A visible light / short-wave infrared dual-band common-aperture optical system includes a common-aperture section, a planar beam splitter, a visible light channel subsystem, and a short-wave infrared channel subsystem. The common-aperture section is located at the front end of the optical system and includes a primary mirror and a secondary mirror arranged coaxially. The planar beam splitter is located in the optical path behind the secondary mirror, and the normal of the planar beam splitter forms a 45° angle with the optical axis. Full-band light rays from the object side are reflected sequentially by the primary mirror and the secondary mirror before reaching the planar beam splitter. The planar beam splitter splits the light rays and then sends them into the visible light channel subsystem and the short-wave infrared channel subsystem for imaging in different bands.

[0010] Furthermore, the visible light channel subsystem is located on the reflected light path of the planar beam splitter and consists of a first planar mirror, a first biconvex positive lens, a first meniscus positive lens, a second meniscus positive lens, a first meniscus negative lens, and a first biconcave negative lens. The first planar mirror is placed at a 45° angle to the optical axis and is parallel to the planar beam splitter.

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

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

[0013] Furthermore, the short-wave infrared channel subsystem is located on the transmission optical path of the planar beam splitter and consists of a second planar 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 planar reflector is placed at 45° to the optical axis and is perpendicular to the planar beam splitter.

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

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

[0016] Furthermore, the primary reflector is made of microcrystalline glass, and the secondary reflector is made of quartz. The optical material of the planar beam splitter is quartz. The optical material of the first planar reflector is quartz, the optical material of the first biconvex 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 biconcave negative lens is H-ZLAF89L. The optical material of the second planar reflector is quartz, the optical material of the second biconvex positive lens is H-LAF54, the optical material of the third biconvex positive lens is H-ZLAF3, the optical material of the second biconcave negative lens is H-ZF62, the optical material of the third biconcave negative lens is H-LAF54, and the optical material of the second meniscus negative lens is H-ZK9B.

[0017] Furthermore, the optical system operates in the visible light band (0.38μm–0.76μm) and the short-wave infrared band (0.9μm–1.7μm), with a focal length of 1200mm in both bands. # : 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 occlusion ratio of the optical system is ≤0.25.

[0019] Beneficial effects:

[0020] The dual-band common-aperture optical system provided by this invention solves the problems of large size and difficulty in achieving long focal lengths and large relative apertures caused by the combination and assembly of traditional multi-band systems after separate design. It realizes that visible light and short-wave infrared dual bands share a single front-end optical aperture, and then uses a beam splitter to split the light into subsequent visible light and short-wave infrared channels for imaging. This simplifies the system structure and reduces the system size. Compared with traditional combined dual-band systems, it eliminates the need for parallelism adjustment of the optical axes of the two systems, reduces the difficulty of system assembly and adjustment, and avoids the correction errors that may be caused by using multiple optical systems.

[0021] This invention achieves a system obstruction ratio of ≤0.25 by rationally allocating the optical power of the primary and secondary mirrors, effectively reducing the impact of central obstruction on the modulation transfer function (MTF) and energy equivalent F-number of the optical system, and ensuring that the system has high imaging quality. Attached Figure Description

[0022] Figure 1 Optical path diagram of the optical system of this invention;

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

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

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

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

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

[0028] Figure 7 The optical system of this invention provides field curvature and distortion diagrams in the short-wave infrared band.

[0029] In the diagram, 1 is the primary reflector, 2 is the secondary reflector, 3 is the planar beam splitter, 4 is the first planar 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 planar 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 Implementation

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

[0031] To make the above features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings, which are for illustrative purposes only and are not drawn to scale.

[0032] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right" and other terms indicating orientation or positional relationship are only used to correspond to the drawings of this application for the purpose of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation.

[0033] The terms “first,” “second,” and “third” are used for descriptive purposes only, referring to the order in which lenses of this type appear, and are used to distinguish them in the description, and should not be interpreted as indicating or implying relative importance.

[0034] The dual-band common-aperture optical system of this 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 section, a planar 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 common front-end optical aperture, and then the beam is split by the beam splitter, so that the light enters the subsequent visible light and short-wave infrared channels for imaging in different bands.

[0035] The common aperture section, i.e. the dual-band shared section, 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. The planar beam splitter 3 is located in the optical path behind the secondary reflector 2. The normal of the planar beam splitter 3 forms a 45° angle with the optical axis. The full-band light from the object side is reflected sequentially by the primary reflector 1 and the secondary reflector 2 before reaching the planar beam splitter 3. The planar 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 planar beam splitter 3 and consists of a first planar mirror 4, a first biconvex positive lens 5, a first meniscus positive lens 6, a second meniscus positive lens 7, a first meniscus negative lens 8, and a first biconcave negative lens 9. The normal of the first planar mirror 4 forms a 45° angle with the optical axis. The first planar mirror 4 is parallel to the planar beam splitter 3. The concave surface of the second meniscus positive lens 7 is set towards the visible light image plane 10.

[0037] The short-wave infrared channel subsystem is located on the transmission light path of the planar beam splitter 3. It consists of a second planar 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 planar reflector 11 is placed at a 45° angle to the optical axis (i.e., the normal of the second planar reflector 11 forms a 45° angle with the optical axis) and is perpendicular to the planar beam splitter 3. It can refract the transmitted light from the planar beam splitter 3 by 90° before entering the second biconvex positive lens 12.

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

[0039] This invention achieves a dual-band common aperture design through a primary reflector 1, a secondary reflector 2, and a planar beam splitter 3. By folding the light path through the reflectors, the system is miniaturized and suitable for use in optoelectronic pods. The planar beam splitter 3 is placed at a 45° angle to the optical axis, and the first planar reflector 4 is also placed at a 45° angle to the optical axis. The planar beam splitter 3 and the first planar reflector 4 are placed parallel to each other. The second planar reflector 11 is placed at a 90° angle to the planar beam splitter 3, and the light propagation direction changes by 90° after reflection by the second planar reflector 11.

[0040] In the visible light / shortwave infrared dual-band common aperture optical system, the light transmission path of the visible light portion is as follows: the full-band light from the object side is reflected by the primary reflector 1 and reaches the secondary reflector 2. After being reflected by the secondary reflector 2, it reaches the planar beam splitter 3. The visible light in the 0.38μm to 0.76μm band is reflected by the planar beam splitter 3 and reaches the first planar reflector 4. After being reflected by the first planar reflector 4, it reaches the first cemented lens I, which is composed of the first biconvex positive lens 5 and the first meniscus positive lens 6. After being converged by the first cemented lens I, it reaches the second meniscus positive lens 7. After being converged by the second meniscus positive lens 7, it reaches the second cemented lens II, which is composed of the first meniscus negative lens 8 and the first biconcave negative lens 9. After being diverged by the second cemented lens II, it is imaged on the visible light image plane 10.

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

[0042] The focal lengths of all lenses in the system must meet the following conditions:

[0043] The primary reflector 1 satisfies the following condition: 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 primary 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 Abbe constant of the d-line 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, where 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 of the material of the first meniscus positive lens 6, and Vd6 is the Abbe constant of the d-line 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, where 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 of the material of the second meniscus positive lens 7, and Vd7 is the Abbe constant of the d-line 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, where 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 of the material of the first meniscus negative lens 8, and Vd8 is the Abbe constant of the d-line 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, where 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 of the material of the first biconcave negative lens 9, and Vd9 is the Abbe constant of the d-line of the material of the first biconcave negative lens 9;

[0050] The second biconvex positive lens 12 satisfies the following condition: 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 The effective focal length of the second biconvex positive lens 12, Nd 12 The refractive index of the d-line of the material of the second biconvex positive lens 12, Vd 12 The Abbe constant for the d-line 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 The effective focal length of the third biconvex positive lens 13, Nd 13 The refractive index of the d-line of the material of the third biconvex positive lens 13, Vd 13 denoted as Abbe constant for the d-line 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 The effective focal length of the second biconcave negative lens 14, Nd 14 The refractive index of the d-line of the material of the second biconcave negative lens 14, Vd 14 The Abbe constant for the d-line 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 The effective focal length of the third biconcave negative lens 15, Nd 15 The refractive index of the d-line of the material of the third biconcave negative lens 15, Vd 15 The Abbe constant for the d-line 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 The effective focal length of the second meniscus negative lens 16, Nd 16 The refractive index of the d-line of the material for the second meniscus negative lens 16, Vd 16 Let be the Abbe constant for the d-line of the material of the second meniscus negative lens 16.

[0055] Preferably, the optical material of the planar beam splitter 3 is quartz; the optical material of the first planar mirror 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 planar mirror 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 specifications achieved by the optical system are as follows: wavelength: 0.38μm~0.76μm (visible light), 0.9μm~1.7μm (shortwave infrared); focal length: 1200mm (visible light), 1200mm (midwave infrared); F#: 6.0 (visible light), 6.0 (shortwave infrared); blocking ratio: ≤0.25.

[0057] Table 1 shows a set of specific parameters for the visible light subsystem of this embodiment, including the surface shape, radius of curvature, thickness, aperture, and material of each lens. The units for the radius of curvature and thickness of the lens are mm. The radius of curvature of spherical and aspherical surfaces 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. Its sign is determined by taking the intersection of the surface and the principal optical axis as the starting point and the center of the surface as the ending 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 planar, its radius of curvature is infinite. The "thickness" in Table 1 gives the distance between two adjacent surfaces on the optical axis. Its sign is determined by taking the vertex of the current surface as the starting point and the vertex of the next surface as the ending 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 the lens material, the thickness represents the lens thickness; 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 separation system in the embodiments of the present invention.

[0059]

[0060]

[0061] Table 2 shows a set of specific parameters for the shortwave infrared subsystem in this embodiment, in mm. These parameters include the surface shape, radius of curvature, thickness, aperture, and material of each lens. The units for the radius of curvature and thickness of the lens are mm. The radius of curvature for spherical and aspherical surfaces refers 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. Its sign is determined by taking the intersection of the surface and the principal optical axis as the starting point and the center of the surface as the ending 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 planar, its radius of curvature is infinite. The "thickness" in Table 2 gives the distance between two adjacent surfaces on the optical axis. Its sign is determined by taking the vertex of the current surface as the starting point and the vertex of the next surface as the ending 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; if there is no material between the two surfaces, it represents the air gap between the two lenses.

[0062] Table 2. Detailed data on the optical system of the shortwave infrared subsystem in the embodiments of the present invention.

[0063]

[0064]

[0065] To verify the imaging quality of the aforementioned optical system, simulations were performed using optical design software, such as... Figure 2 The figure shows the transfer function of the visible light optical system. When a detector with a pixel size of 3.45 μm is used, corresponding to a spatial frequency of 145 lp / mm, the system transfer function is as low as 0.4, indicating excellent system imaging performance. Figure 3 The image shows a dot plot of an optical system in the visible light band. The dot diameter is smaller than the pixel size, indicating that the system has excellent imaging performance. Figure 4 The figure shows the field curvature and distortion diagram of the visible light optical system, with a system distortion of less than 2.0%.

[0066] like Figure 5 The figure shows the transfer function of the short-wave infrared optical system. When a detector with a pixel size of 15 μm is used, corresponding to a spatial frequency of 33 lp / mm, the system transfer function is as low as 0.5, indicating excellent system imaging performance. Figure 6 The image shows a dot plot of a short-wave infrared optical system. The dot diameter is smaller than the pixel size, indicating excellent system imaging performance. Figure 7 The figure shows the field curvature and distortion diagram of the short-wave infrared optical system. The system distortion is less than 2.5%.

[0067] Therefore, the dual-band common-aperture optical system of this invention achieves the sharing of a single front-end optical aperture for both visible and short-wave infrared bands. It utilizes a planar beam splitter for beam splitting, with the light then entering the subsequent visible and short-wave infrared channels for imaging. This enables a long focal length and large aperture design for the dual-band system, thereby improving the system's target detection / identification capabilities. It boasts advantages such as high spatial resolution, long operating distance, and high identification probability, while simultaneously reducing system size, simplifying system structure, and lowering assembly and adjustment difficulty. Through reasonable allocation of optical power between the primary and secondary mirrors, the system achieves an obstruction ratio ≤0.25, effectively reducing the impact of central obstruction on the optical system's modulation transfer function (MTF) and energy equivalent F-number.

[0068] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A visible light / shortwave infrared dual-band common aperture optical system, characterized in that, The system includes a common aperture section, a planar beam splitter (3), a visible light channel subsystem, and a short-wave infrared channel subsystem. The common aperture section is located at the front end of the optical system and includes a primary reflector (1) and a secondary reflector (2) arranged coaxially. The planar beam splitter (3) is located on the optical path behind the secondary reflector (2). The normal of the planar beam splitter (3) forms a 45° angle with the optical axis. The full-band light from the object side is reflected sequentially by the primary reflector (1) and the secondary reflector (2) and then reaches the planar beam splitter (3). The planar 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. The visible light channel subsystem is located on the reflected light path of the planar beam splitter (3) and consists of a first planar mirror (4), a first biconvex positive lens (5), a first meniscus positive lens (6), a second meniscus positive lens (7), a first meniscus negative lens (8), and a first biconcave negative lens (9). The first planar mirror (4) is placed at a 45° angle to the optical axis and is parallel to the planar beam splitter (3). The first biconvex 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 biconcave negative lens (9) form a second cemented lens II. The short-wave infrared channel subsystem is located on the transmission light path of the planar beam splitter (3) and consists of a second planar 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 planar reflector (11) is placed at 45° to the optical axis and is perpendicular to the planar beam splitter (3). The third biconvex positive lens (13) and the second biconcave negative lens (14) form the third cemented lens III, and the third biconcave negative lens (15) and the second meniscus negative lens (16) form the fourth cemented lens IV.

2. The visible light / shortwave infrared dual-band common aperture optical system according to claim 1, characterized in that, The concave surface of the second meniscus positive lens (7) is set facing the visible light image plane (10).

3. The visible light / shortwave infrared dual-band common aperture optical system according to claim 1, characterized in that, The primary reflector (1) has a parabolic reflector surface, and the secondary reflector (2) has a hyperboloid reflector surface.

4. The visible light / shortwave infrared dual-band common aperture optical system according to claim 3, characterized in that, The primary reflector (1) is made of microcrystalline glass, and the secondary reflector (2) is made of quartz.

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

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

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