Large aperture multi-band common optical path optical system

Abstract

This invention relates to a large-aperture multi-band common-path optical system, comprising a front-end common-aperture section, a planar beam splitter, a visible light channel subsystem, a short-wave infrared channel subsystem, and a mid-wave infrared channel subsystem. The front-end common-aperture section consists of a primary mirror, a secondary mirror, and a first planar mirror. Full-band light from the object side enters the first and second planar beam splitters after passing through the front-end common-aperture section. The light is split into three paths and then enters the visible light channel, short-wave infrared channel, and mid-wave infrared channel for imaging, respectively. Compared with traditional optical systems, this common-path optical system effectively increases the system focal length, reduces the system volume, and facilitates miniaturization while maintaining long focal length. It achieves a long focal length, miniaturized, and highly integrated design, reduces system volume and overall weight, and achieves the goals of multi-band composite imaging, long focal length, and lightweight design.

Description

Technical Field

[0001] This invention relates to the field of optical imaging systems, and more specifically to a large-aperture multi-band common optical path optical system. Background Technology

[0002] To improve the detection / identification capabilities of optoelectronic systems for distant targets, airborne 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. Therefore, modern airborne optoelectronic payload optical systems are developing towards longer focal lengths and larger apertures.

[0003] With the development of camouflage technology, the difficulty of detecting and identifying targets is constantly increasing. Traditional single-band systems using visible light or infrared light have defects and limitations, making it difficult to quickly and accurately intercept and track targets in complex battlefield environments and complete combat missions. Since the optical characteristics of targets vary significantly across different spectral bands, electro-optical reconnaissance systems 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 areas such as improving recognition probability, anti-stealth, camouflage identification, feature resolution, and biochemical detection.

[0004] In recent years, the increasing height and complexity of operating environments of optoelectronic platforms, coupled with the rapid advancements in image fusion technology, have created an urgent need to address the challenges of multi-band, long-range, imaging detection technologies. Furthermore, under the constraints of miniaturization, lightweighting, low power consumption, and low cost, optoelectronic payloads have evolved from single-band multi-aperture to multi-band multi-aperture systems. Visible light is an indispensable operating band for targeting systems from start to finish. Visible light is perceived by the human eye, displaying an image consistent with the visual perception, rich in detail, and facilitating the observation of target details. However, the use of visible light systems is limited under complex weather conditions or at night when the visible light reflected from the target is weak. Short-wave infrared has the ability to penetrate smoke, thus adapting to complex environments. Mid-wave infrared is passive, detecting the object's own radiation, therefore it does not rely on external lighting, offering strong concealment, strong fog penetration, and the ability to identify camouflage, enabling all-weather, long-range observation. Therefore, since the optical characteristics of a target vary greatly across different spectral bands, dual-band and multi-band optical systems, compared to single-band optical systems, fuse information collected from two or more bands to obtain more comprehensive and accurate target information.

[0005] Currently, most multi-band optical systems are designed separately for different bands and then assembled together to form a multi-band optical system. Specifically, existing visible, mid-wave and short-wave infrared optical systems are combinations of three separate systems: visible, mid-wave and short-wave infrared. This results in a relatively large system size, which is not conducive to miniaturization. Summary of the Invention

[0006] To address the technical challenges of large size and difficulty in achieving long focal lengths, miniaturization, and large apertures in traditional multi-band systems that require separate design and assembly, this invention provides a large-aperture multi-band common-path optical system. This system enables visible light, mid-wave infrared, and short-wave infrared bands to share a single front-end optical aperture. After beam splitting, the light enters the subsequent visible light, short-wave infrared, and mid-wave infrared channels for imaging, respectively. This achieves a long focal length, miniaturized, and highly integrated design, reducing system size and overall weight, and realizing the goals of multi-band composite imaging, long focal length, and lightweight design.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A large-aperture, multi-band common-path optical system is disclosed. The system comprises a front-end common-aperture section, a planar beam splitter, a visible light channel subsystem, a short-wave infrared channel subsystem, and a mid-wave infrared channel subsystem. The front-end common-aperture section consists of a primary mirror, a secondary mirror, and a first planar mirror. The normal of the first planar mirror forms a 45° angle with the optical axis. The planar beam splitter includes a first planar beam splitter and a second planar beam splitter. The first planar beam splitter is arranged parallel to the first planar mirror. Full-band light rays from the object side enter the optical path after passing through the front-end common-aperture section. The first planar beam splitter is divided into two parts. The mid-wave infrared light from the transmission part enters the mid-wave infrared channel subsystem, while the visible light and short-wave infrared light from the reflection part enter the second planar beam splitter. The normal of the second planar beam splitter is set at a 90° angle to the normal of the first planar beam splitter. The second planar beam splitter continues to split the light. The visible light from the reflection part enters the visible light channel subsystem, and the short-wave infrared light from the transmission part enters the short-wave infrared channel subsystem. Each subsystem images the light of the corresponding wavelength band onto its respective image plane.

[0008] Furthermore, the visible light channel subsystem comprises a first meniscus positive lens, a first meniscus negative lens, a second meniscus positive lens, a third meniscus positive lens, a second meniscus negative lens, and a third meniscus negative lens; the short-wave infrared channel subsystem comprises a fourth meniscus negative lens, a fifth meniscus negative lens, a first biconcave negative lens, a first biconvex positive lens, a second biconvex positive lens, a fourth meniscus positive lens, a third biconvex positive lens, a fifth meniscus positive lens, and a second biconcave negative lens; the mid-wave infrared channel subsystem comprises a sixth meniscus positive lens, a sixth meniscus negative lens, a second plane mirror, a seventh meniscus positive lens, an eighth meniscus positive lens, and a seventh meniscus negative lens, wherein the second plane mirror is located between the sixth meniscus negative lens and the seventh meniscus positive lens, and the normal of the second plane mirror is coaxial with the normal of the first plane mirror.

[0009] Furthermore, the first meniscus positive lens and the first meniscus negative lens form the first cemented lens, the third meniscus positive lens and the second meniscus negative lens form the second cemented lens, the fifth meniscus negative lens and the first biconcave negative lens form the third cemented lens, and the second biconvex positive lens and the fourth meniscus positive lens form the fourth cemented lens.

[0010] Furthermore, the image plane defocus compensation of the visible light subsystem within the temperature range of -40℃ to +60℃ and the system defocus compensation caused by changes in the distance of the observed object are achieved by axially moving the third meniscus negative lens; the image plane defocus compensation of the short-wave infrared subsystem within the temperature range of -40℃ to +60℃ and the system defocus compensation caused by changes in the distance of the observed object are achieved by axially moving the second biconcave negative lens; and the image plane defocus compensation of the mid-wave infrared subsystem within the temperature range of -40℃ to +60℃ and the system defocus compensation caused by changes in the distance of the observed object are achieved by axially moving the seventh meniscus positive lens.

[0011] Furthermore, the primary and secondary reflectors are made of microcrystalline glass, the first plane reflector, the second plane beam splitter, and the second plane reflector are all made of quartz, and the first plane beam splitter is made of zinc sulfide (ZNS).

[0012] Furthermore, the first meniscus positive lens is made of H-ZF52, the first, second, third, and third meniscus positive lenses and the third meniscus negative lens are made of H-ZK9A, the second meniscus negative lens is made of H-ZF13, the fourth meniscus negative lens is made of H-QF3, the fifth meniscus negative lens is made of H-ZLAF76, the first biconcave negative lens is made of H-QF8, and the first biconvex positive lens is made of H-LAF54. The second biconvex positive lens is made of H-ZLAF3, the fourth meniscus positive lens is made of H-ZF62, the third biconvex positive lens is made of H-ZLAF71, the fifth meniscus positive lens is made of H-LAF4, the second biconcave negative lens is made of H-ZF62, the sixth meniscus positive lens is made of ZNSE, the sixth, seventh, and seventh meniscus negative lenses are all made of Ge, and the eighth meniscus positive lens is made of SILICN.

[0013] Furthermore, the mid-wave infrared subsystem adopts a secondary imaging system, with the primary image plane located between the seventh and eighth meniscus lenses, and a field stop is set at the position of the primary image plane.

[0014] Furthermore, the front surface of the seventh meniscus positive lens and the rear surface of the seventh meniscus negative lens are both made of high-order aspherical surfaces.

[0015] Furthermore, the obstruction ratio of the optical system is: .

[0016] Furthermore, the operating wavelengths of this optical system are: 0.38μm–0.76μm visible light band, 0.9μm–1.7μm short-wave infrared band, and 3.7μm–4.8μm mid-wave infrared band; the focal length in all three bands is 800mm; F # All are 4.

[0017] Beneficial effects: This invention optimizes the layout of optical components to enable three bands—visible light, mid-wave infrared, and short-wave infrared—to share a single front-end optical aperture. After beam splitting using a beam splitter, the light enters the subsequent visible light, short-wave infrared, and mid-wave infrared channels for imaging. By integrating the three subsystems, a long focal length, miniaturized, and highly integrated design is achieved, reducing the system size and overall weight, thus achieving the goals of multi-band composite imaging, long focal length, and lightweight design.

[0018] 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.

[0019] The mid-wave infrared subsystem of this invention employs a secondary imaging system. A field stop is set at the primary image plane position, preventing stray light outside the system's field of view from passing through the field stop to reach the image plane. This effectively reduces the impact of stray light on the optical system's imaging and improves the signal-to-noise ratio. A cold stop is set at the exit pupil to minimize the stop aperture, and the system achieves 100% cold stop efficiency, preventing beam cutting, reducing energy loss, and improving system sensitivity. Attached Figure Description

[0020] Figure 1 Optical path diagram of the optical system of this invention.

[0021] Figure 2 The transfer function diagram of the visible light channel subsystem of the optical system of this invention.

[0022] Figure 3 A point diagram of the visible light channel subsystem of the optical system of this invention.

[0023] Figure 4 The field curvature and distortion diagram of the visible light channel subsystem of the optical system of this invention.

[0024] Figure 5 The transfer function diagram of the short-wave infrared channel subsystem of the optical system of this invention.

[0025] Figure 6 A point diagram of the short-wave infrared channel subsystem optical system of the optical system of this invention.

[0026] Figure 7 Field curvature and distortion diagram of the short-wave infrared channel subsystem of the optical system of this invention.

[0027] Figure 8 The transfer function diagram of the infrared channel subsystem optical system in the optical system of this invention.

[0028] Figure 9 A point diagram of the optical system of the infrared channel subsystem in the optical system of this invention.

[0029] Figure 10 The field curvature and distortion diagram of the infrared channel subsystem optical system in the optical system of this invention.

[0030] Among them, 1 is the primary reflecting mirror, 2 is the secondary reflecting mirror, 3 is the first plane reflecting mirror, 4 is the first plane beam splitter, 5 is the second plane beam splitter, 6 is the first meniscus positive lens, 7 is the first meniscus negative lens, 8 is the second meniscus positive lens, 9 is the third meniscus positive lens, 10 is the second meniscus negative lens, 11 is the third meniscus negative lens, 12 is the visible light image plane, 13 is the fourth meniscus negative lens, 14 is the fifth meniscus negative lens, and 15 is the first biconcave negative lens. 16 is the first biconvex positive lens, 17 is the second biconvex positive lens, 18 is the fourth meniscus positive lens, 19 is the third biconvex positive lens, 20 is the fifth meniscus positive lens, 21 is the second biconcave negative lens, 22 is the short-wave infrared image plane, 23 is the sixth meniscus positive lens, 24 is the sixth meniscus negative lens, 25 is the second plane mirror, 26 is the seventh meniscus positive lens, 27 is the eighth meniscus positive lens, 28 is the seventh meniscus negative lens, and 29 is the mid-wave infrared image plane. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. In the description of the present invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," and "right," etc., indicating orientation or positional relationships, are merely for the purpose of describing the present invention and do not indicate or imply that the device or element referred to must have a specific orientation.

[0032] In the specification, the same reference numerals refer to the same components. The accompanying drawings are for illustrative purposes only and are not drawn to scale.

[0033] Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only, referring to the order in which lenses of this type appear. They are used to distinguish between them in description and have no special meaning. They should not be interpreted as indicating or implying relative importance.

[0034] like Figure 1 As shown, a large-aperture multi-band common-path optical system consists of a front-end common-aperture section, a planar beam splitter, a visible light channel subsystem, a short-wave infrared channel subsystem, and a mid-wave infrared channel subsystem. In this optical system, the visible light, short-wave infrared, and mid-wave infrared bands share a single front-end optical aperture. The beams are then split by the beam splitter and enter the subsequent visible light, short-wave infrared, and mid-wave infrared channels respectively for imaging in different bands.

[0035] The front end common aperture section includes a primary reflector 1, a secondary reflector 2, and a first plane reflector 3. The first plane reflector 3 is disposed in the optical path behind the secondary reflector 2, and the normal of the first plane reflector 3 forms a 45° angle with the optical axis.

[0036] The planar beam splitter includes a first planar beam splitter 4 and a second planar beam splitter 5, which are used to split light into different subsystems. The first planar beam splitter 4 is arranged parallel to the first planar reflector 3. The full-band light from the object side enters the first planar beam splitter 4 after passing through the front common aperture section and is split into two parts. The transmitted part enters the mid-wave infrared channel subsystem, and the reflected part enters the second planar beam splitter 5. The normal of the second planar beam splitter 5 is set at a 90° angle with the normal of the first planar beam splitter 4. The second planar beam splitter 5 continues to split the light. The reflected part enters the visible light channel subsystem, and the transmitted part enters the short-wave infrared channel subsystem.

[0037] The visible light channel subsystem is set on the reflected light path of the second planar beam splitter 5, and is composed of a first meniscus positive lens 6, a first meniscus negative lens 7, a second meniscus positive lens 8, a third meniscus positive lens 9, a second meniscus negative lens 10, and a third meniscus negative lens 11. Among them, the first meniscus positive lens 6 and the first meniscus negative lens 7 form the first cemented lens I, and the third meniscus positive lens 9 and the second meniscus negative lens 10 form the second cemented lens II.

[0038] The shortwave infrared channel subsystem is set in the transmission light path of the second planar beam splitter 5, and is composed of a fourth meniscus negative lens 13, a fifth meniscus negative lens 14, a first biconcave negative lens 15, a first biconvex positive lens 16, a second biconvex positive lens 17, a fourth meniscus positive lens 18, a third biconvex positive lens 19, a fifth meniscus positive lens 20, and a second biconcave negative lens 21. The fifth meniscus negative lens 14 and the first biconcave negative lens 15 form the third cemented lens III, and the second biconvex positive lens 17 and the fourth meniscus positive lens 18 form the fourth cemented lens IV.

[0039] The mid-wave infrared channel subsystem is set in the transmission light path of the first planar beam splitter 4, and consists of a sixth meniscus positive lens 23, a sixth meniscus negative lens 24, a second planar reflector 25, a seventh meniscus positive lens 26, an eighth meniscus positive lens 27, and a seventh meniscus negative lens 28. The second planar reflector 25 is located between the sixth meniscus negative lens 24 and the seventh meniscus positive lens 26, and the normal of the second planar reflector 25 is coaxial with the normal of the first planar reflector 3.

[0040] The mid-wave infrared subsystem adopts a secondary imaging system. The primary image plane is located between the seventh meniscus positive lens 26 and the eighth meniscus positive lens 27, and a field stop is set at the position of the primary image plane.

[0041] The optical propagation direction of this multi-band common-path optical system is as follows: full-band light from the object side is reflected by the primary reflector 1 and reaches the secondary reflector 2, then reflected by the secondary reflector 2 and reaches the first plane reflector 3, then reflected by the first plane reflector 3 and reaches the first plane beam splitter 4. Mid-wave infrared light of 3.7μm to 4.8μm passes through the first plane beam splitter 4 and enters the mid-wave infrared channel subsystem; visible light of 0.38μm to 0.76μm and short-wave infrared light of 0.9μm to 1.7μm are reflected by the first plane beam splitter 4 and reach the second plane beam splitter 5. Then, visible light of 0.38μm to 0.76μm is reflected by the second plane beam splitter 5 and enters the visible light channel subsystem, and short-wave infrared light of 0.9μm to 1.7μm passes through the second plane beam splitter 5 and enters the short-wave infrared channel subsystem.

[0042] Specifically, mid-wave infrared light of 3.7μm to 4.8μm passes through the first planar beam splitter 4 and reaches the sixth meniscus positive lens 23. After being converged by the sixth meniscus positive lens 23, it reaches the sixth meniscus negative lens 24. After being diverged by the sixth meniscus negative lens 24, it reaches the second planar reflector 25. After being reflected by the second planar reflector 25, it reaches the seventh meniscus positive lens 26. After being converged by the seventh meniscus positive lens 26, it reaches the eighth meniscus positive lens 27. After being converged by the eighth meniscus positive lens 27, it reaches the seventh meniscus negative lens 28. After being diverged by the seventh meniscus negative lens 28, it is imaged on the mid-wave infrared image plane 29.

[0043] Visible light rays in the 0.38μm to 0.76μm band are reflected by the second planar beam splitter 5 and reach the first meniscus positive lens 6. After being converged by the first meniscus positive lens 6, they reach the first meniscus negative lens 7. After being diverged by the first meniscus negative lens 7, they reach the second meniscus positive lens 8. After being converged by the second meniscus positive lens 8, they reach the third meniscus positive lens 9. After being converged by the third meniscus positive lens 9, they reach the second meniscus negative lens 10. After being diverged by the second meniscus negative lens 10, they reach the third meniscus negative lens 11. After being diverged by the third meniscus negative lens 11, they are imaged on the visible light image plane 12.

[0044] Short-wave infrared light of 0.9μm to 1.7μm passes through the second planar beam splitter 5 and reaches the fourth meniscus negative lens 13. After being diverged by the fourth meniscus negative lens 13, it reaches the fifth meniscus negative lens 14. After being diverged by the fifth meniscus negative lens 14, it reaches the first biconcave negative lens 15. After being diverged by the first biconcave negative lens 15, it reaches the first biconvex positive lens 16. After being converged by the first biconvex positive lens 16, it reaches the second biconvex positive lens 17. After being converged by the second biconvex positive lens 17, it reaches the fourth meniscus positive lens 18. After being converged by the fourth meniscus positive lens 18, it reaches the third biconvex positive lens 19. After being converged by the third biconvex positive lens 19, it reaches the fifth meniscus positive lens 20. After being converged by the fifth meniscus positive lens 20, it reaches the second biconcave negative lens 21. After being diverged by the second biconcave negative lens 21, it is imaged on the short-wave infrared image plane 22.

[0045] The common-path optical system employs an axially moving third meniscus negative lens 11 to achieve image plane defocus compensation for the visible light subsystem within a temperature range of -40℃ to +60℃, as well as system defocus compensation caused by changes in the distance of the observed object, thereby ensuring clear imaging of objects at different distances by the visible light subsystem. It also employs an axially moving second biconcave negative lens 21 to achieve image plane defocus compensation for the short-wave infrared subsystem within the same temperature range, as well as system defocus compensation caused by changes in the distance of the observed object, thus ensuring clear imaging of objects at different distances by the short-wave infrared subsystem. Finally, it employs an axially moving seventh meniscus positive lens 26 to achieve image plane defocus compensation for the mid-wave infrared subsystem within the same temperature range, as well as system defocus compensation caused by changes in the distance of the observed object, thus ensuring clear imaging of objects at different distances by the mid-wave infrared subsystem.

[0046] Preferably, the primary reflector 1 and secondary reflector 2 are made of microcrystalline glass; the first plane reflector 3, the second plane beam splitter 5, and the second plane reflector 25 are all made of quartz; the first plane beam splitter 4 is made of zinc sulfide (ZNS); the first meniscus positive lens 6 is made of H-ZF52; the first meniscus negative lens 7, the second meniscus positive lens 8, the third meniscus positive lens 9, and the third meniscus negative lens 11 are made of H-ZK9A; the second meniscus negative lens 10 is made of H-ZF13; the fourth meniscus negative lens 13 is made of H-QF3; and the fifth meniscus negative lens 14 is made of H-ZLAF76. The concave negative lens 15 is made of H-QF8, the first biconvex positive lens 16 is made of H-LAF54, the second biconvex positive lens 17 is made of H-ZLAF3, the fourth meniscus positive lens 18 is made of H-ZF62, the third biconvex positive lens 19 is made of H-ZLAF71, the fifth meniscus positive lens 20 is made of H-LAF4, the second biconcave negative lens 21 is made of H-ZF62, the sixth meniscus positive lens 23 is made of ZNSE, the sixth meniscus negative lens 24, the seventh meniscus positive lens 26, and the seventh meniscus negative lens 28 are all made of Ge, and the eighth meniscus positive lens 27 is made of SILICN.

[0047] Preferably, the primary reflector 1 satisfies the following condition: 0.20≤f1 / f≤0.23, where f is the effective focal length of the optical system and f1 is the effective focal length of the primary reflector 1.

[0048] Preferably, the secondary reflector 2 satisfies the following condition: 0.05≤f2 / f≤0.06, where f is the effective focal length of the optical system and f2 is the effective focal length of the secondary reflector 2.

[0049] Preferably, the first meniscus positive lens 6 satisfies the following condition: 1.10≤f6 / f≤1.20, where f is the effective focal length of the optical system and f6 is the effective focal length of the first meniscus positive lens 6.

[0050] Preferably, the first meniscus negative lens 7 satisfies the following condition: -0.26≤f7 / f≤-0.24, where f is the effective focal length of the optical system and f7 is the effective focal length of the first meniscus negative lens 7.

[0051] Preferably, the second meniscus positive lens 8 satisfies the following condition: 0.12≤f8 / f≤0.14, where f is the effective focal length of the optical system and f8 is the effective focal length of the second meniscus positive lens 8.

[0052] Preferably, the third meniscus positive lens 9 satisfies the following condition: 0.20≤f9 / f≤0.22, where f is the effective focal length of the optical system and f9 is the effective focal length of the third meniscus positive lens 9.

[0053] Preferably, the second meniscus negative lens 10 satisfies the following condition: -0.28 ≤ f 10 / f≤-0.26, where f is the effective focal length of the optical system, f 10 This is the effective focal length of the second meniscus negative lens 10.

[0054] Preferably, the third meniscus negative lens 11 satisfies the following condition: -0.04 ≤ f 11 / f≤-0.03, where f is the effective focal length of the optical system, f 11 The effective focal length of the third meniscus negative lens 11.

[0055] Preferably, the fourth meniscus negative lens 13 satisfies the following condition: -0.28 ≤ f 13 / f≤-0.25, where f is the effective focal length of the optical system, f 13 This is the effective focal length of the fourth meniscus negative lens 13.

[0056] Preferably, the fifth meniscus negative lens 14 satisfies the following condition: -0.15 ≤ f 14 / f≤-0.10, where f is the effective focal length of the optical system, f 14 This is the effective focal length of the fifth crescent-shaped negative lens 14.

[0057] Preferably, the first biconcave negative lens 15 satisfies the following condition: -0.20 ≤ f 15 / f≤-0.10, where f is the effective focal length of the optical system, f 15 The effective focal length of the first biconcave negative lens 15.

[0058] Preferably, the first biconvex positive lens 16 satisfies the following condition: 0.08 ≤ f 16 / f≤0.10, where f is the effective focal length of the optical system, f 16 This is the effective focal length of the first biconvex positive lens 16.

[0059] Preferably, the second biconvex positive lens 17 satisfies the following condition: 0.20 ≤ f 17 / f≤0.30, where f is the effective focal length of the optical system, f 17 This is the effective focal length of the second biconvex positive lens 17.

[0060] Preferably, the fourth meniscus positive lens 18 satisfies the following condition: 0.40 ≤ f 18 / f≤0.50, where f is the effective focal length of the optical system, f 18 This is the effective focal length of the fourth meniscus positive lens 18.

[0061] Preferably, the third biconvex positive lens 19 satisfies the following condition: 0.12 ≤ f 19 / f≤0.15, where f is the effective focal length of the optical system, f 19 This is the effective focal length of the third biconvex positive lens 19.

[0062] Preferably, the fifth meniscus positive lens 20 satisfies the following condition: 0.05 ≤ f 20 / f≤0.07, where f is the effective focal length of the optical system, f 20 This is the effective focal length of the fifth crescent-shaped positive lens 20.

[0063] Preferably, the second biconcave negative lens 21 satisfies the following condition: -0.02 ≤ f 21 / f≤-0.01, where f is the effective focal length of the optical system, f 21 This is the effective focal length of the second biconcave negative lens 21.

[0064] Preferably, the sixth crescent-shaped positive lens 23 satisfies the following condition: 0.06 ≤ f 23 / f≤0.08, where f is the effective focal length of the optical system, f 23 The effective focal length of the sixth crescent-shaped positive lens 23.

[0065] Preferably, the sixth crescent-shaped negative lens 24 satisfies the following condition: -0.07 ≤ f 24 / f≤-0.05, where f is the effective focal length of the optical system, f 24 This is the effective focal length of the sixth crescent-shaped negative lens 24.

[0066] Preferably, the seventh meniscus positive lens 26 satisfies the following condition: 2.80 ≤ f 26 / f≤2.90, where f is the effective focal length of the optical system, f 26 This is the effective focal length of the seventh crescent-shaped positive lens 26.

[0067] Preferably, the eighth meniscus positive lens 27 satisfies the following condition: 0.015 ≤ f 27 / f≤0.025, where f is the effective focal length of the optical system, f 27 This is the effective focal length of the eighth crescent-shaped positive lens 27.

[0068] Preferably, the seventh meniscus negative lens 28 satisfies the following condition: -0.05 ≤ f 28 / f≤-0.04, where f is the effective focal length of the optical system, f 28 The effective focal length of the seventh crescent-shaped negative lens 28.

[0069] Furthermore, the front surface of the seventh meniscus positive lens 26 and the rear surface of the seventh meniscus negative lens 28 are both made of high-order aspherical surfaces. The aspherical surfaces in this technical solution adopt the Asphere surface type, and the equation is: Where z is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis, c is the curvature, c=1 / R, R represents the radius of curvature of the lens surface, r is the radial coordinate perpendicular to the optical axis, k is the quadratic curve constant, A is the fourth-order aspherical coefficient, B is the sixth-order aspherical coefficient, and C is the eighth-order aspherical coefficient.

[0070] 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), 3.7μm~4.8μm (midwave infrared); Focal length: 800mm (visible light), 800mm (shortwave infrared), 800mm (midwave infrared); F # :4 (visible light), 4 (mid-wave infrared), 4 (short-wave infrared), blocking ratio: .

[0071] Table 1 shows a set of specific parameters for the common-aperture section at the front end of the optical system, 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 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 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 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.

[0072] Table 1 Detailed data on the common aperture portion of the optical system of this invention. Table 2 provides a set of specific parameters for this visible light subsystem, 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 are mm. The radius of curvature of a spherical surface 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 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 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.

[0073] Table 2. Detailed data of the optical system of the visible light separation system in the embodiments of the present invention. Table 3 provides a set of specific parameters for this shortwave infrared subsystem, 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 are mm. The radius of curvature of a spherical surface refers to the radius of curvature at the intersection of the lens surface and the optical axis. The "radius" in Table 3 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 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 3 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 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.

[0074] Table 3. Detailed data on the optical system of the shortwave infrared subsystem in the embodiments of the present invention. Table 4 provides a set of specific parameters for this mid-wave infrared subsystem, 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 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 4 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 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 4 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 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.

[0075] Table 4. Detailed data on the optical system of the infrared subsystem in the embodiments of the present invention. As shown in Table 5, the aspherical coefficients of each lens in the embodiments are given.

[0076] Table 5 Aspheric coefficients of the optical system of this invention After simulation using optical design software, such as Figure 2 The figure shows the transfer function of the optical system when it is in the visible light channel subsystem. As can be seen from the figure, when the characteristic frequency corresponding to the selected detector with a pixel size of 5.5µm is 90lp / mm, the system transfer function is the lowest at 0.6, which indicates that the system has excellent imaging performance and meets the application requirements.

[0077] like Figure 3 The figure shows a dot plot of the visible light channel subsystem of the optical system of the present invention. As can be seen from the figure, the diameter of the dots is smaller than the pixel size, indicating that the system has excellent imaging performance and meets the application requirements.

[0078] like Figure 4 The figure shows the field curvature and distortion diagrams of the visible light channel subsystem of the optical system of the present invention. As can be seen from the figure, the system distortion is less than 4.5%, which meets the application requirements.

[0079] like Figure 5 The figure shows the transfer function of the short-wave infrared channel subsystem of the optical system of the present invention. When the selected detector with a pixel size of 15µm corresponds to a characteristic frequency of 30lp / mm, it can be seen from the figure that the system transfer function is as low as 0.3, indicating that the system has excellent imaging performance and meets the application requirements.

[0080] like Figure 6 The figure shows a dot plot of the short-wave infrared channel subsystem of the optical system of the present invention. As can be seen from the figure, the diameter of the dots is smaller than the pixel size, indicating that the system has excellent imaging performance and meets the application requirements.

[0081] like Figure 7 The figure shows the field curvature and distortion diagrams of the short-wave infrared channel subsystem of the optical system of the present invention. As can be seen from the figure, the system distortion is less than 1%, which meets the application requirements.

[0082] like Figure 8 The figure shows the transfer function of the optical system of the wave infrared channel subsystem in the optical system of the present invention. As can be seen from the figure, when the characteristic frequency corresponding to the selected detector with a pixel size of 15µm is 30lp / mm, the system transfer function is as low as 0.6, which indicates that the system has excellent imaging performance and meets the application requirements.

[0083] like Figure 9 The figure shows a dot plot of the optical system of the wave infrared channel subsystem in the optical system of the present invention. As can be seen from the figure, the diameter of the dots is comparable to the size of the detector pixel, indicating that the system has excellent imaging performance and meets the application requirements.

[0084] like Figure 10 The figure shows the field curvature and distortion diagrams of the infrared channel subsystem optical system in the optical system of this invention. As can be seen from the figure, the system distortion is less than 3.2%, which meets the application requirements.

[0085] 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.

[0086] The above description is merely a preferred embodiment of the present invention and is 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 large-aperture multi-band common-path optical system, characterized in that, The optical system consists of a front-end common aperture section, a planar beam splitter, a visible light channel subsystem, a short-wave infrared channel subsystem, and a mid-wave infrared channel subsystem. The front-end common aperture section consists of a primary reflector (1), a secondary reflector (2), and a first planar reflector (3). The normal of the first planar reflector (3) forms a 45° angle with the optical axis. The planar beam splitter includes a first planar beam splitter (4) and a second planar beam splitter (5). The first planar beam splitter (4) is arranged parallel to the first planar reflector (3). The full-band light from the object side enters the first planar beam splitter (4) after passing through the common aperture section at the front end and is split into two parts. The mid-wave infrared light of the transmission part enters the mid-wave infrared channel subsystem, and the visible light and short-wave infrared light of the reflection part enter the second planar beam splitter (5). The normal of the second planar beam splitter (5) is set at a 90° angle with the normal of the first planar beam splitter (4). The second planar beam splitter (5) continues to split the light. The visible light of the reflection part enters the visible light channel subsystem, and the short-wave infrared light of the transmission part enters the short-wave infrared channel subsystem. Each subsystem images the light of the corresponding band onto its respective image plane.

2. The multi-band common-path optical system of claim 1, wherein, The visible light channel subsystem consists of a first meniscus positive lens (6), a first meniscus negative lens (7), a second meniscus positive lens (8), a third meniscus positive lens (9), a second meniscus negative lens (10), and a third meniscus negative lens (11); the short-wave infrared channel subsystem consists of a fourth meniscus negative lens (13), a fifth meniscus negative lens (14), a first biconcave negative lens (15), a first biconvex positive lens (16), a second biconvex positive lens (17), a fourth meniscus positive lens (18), a third biconvex positive lens (19), and a fifth meniscus negative lens (11). The system consists of a crescent-shaped positive lens (20) and a second biconcave negative lens (21); the mid-wave infrared channel subsystem consists of a sixth crescent-shaped positive lens (23), a sixth crescent-shaped negative lens (24), a second plane mirror (25), a seventh crescent-shaped positive lens (26), an eighth crescent-shaped positive lens (27), and a seventh crescent-shaped negative lens (28). The second plane mirror (25) is located between the sixth crescent-shaped negative lens (24) and the seventh crescent-shaped positive lens (26). The normal of the second plane mirror (25) is coaxial with the normal of the first plane mirror (3).

3. The multi-band common-path optical system of claim 2, wherein, The first meniscus positive lens (6) and the first meniscus negative lens (7) form the first cemented lens; the third meniscus positive lens (9) and the second meniscus negative lens (10) form the second cemented lens; the fifth meniscus negative lens (14) and the first biconcave negative lens (15) form the third cemented lens; and the second biconvex positive lens (17) and the fourth meniscus positive lens (18) form the fourth cemented lens.

4. The multi-band common-path optical system of claim 2, wherein, The image plane defocus compensation of the visible light subsystem within the temperature range of -40℃ to +60℃ and the system defocus compensation caused by the change in distance of the observed scene are achieved by axially moving the third meniscus negative lens (11); the image plane defocus compensation of the short-wave infrared subsystem within the temperature range of -40℃ to +60℃ and the system defocus compensation caused by the change in distance of the observed scene are achieved by axially moving the second biconcave negative lens (21); and the image plane defocus compensation of the mid-wave infrared subsystem within the temperature range of -40℃ to +60℃ and the system defocus compensation caused by the change in distance of the observed scene are achieved by axially moving the seventh meniscus positive lens (26).

5. The multi-band common-path optical system of claim 2, wherein, The primary reflector (1) and secondary reflector (2) are made of microcrystalline glass, the first plane reflector (3), the second plane beam splitter (5) and the second plane reflector (25) are all made of quartz, and the first plane beam splitter (4) is made of zinc sulfide (ZNS).

6. The multi-band common-path optical system of claim 2, wherein, The first meniscus positive lens (6) is made of H-ZF52, the first meniscus negative lens (7), the second meniscus positive lens (8), the third meniscus positive lens (9), and the third meniscus negative lens (11) are made of H-ZK9A, the second meniscus negative lens (10) is made of H-ZF13, the fourth meniscus negative lens (13) is made of H-QF3, the fifth meniscus negative lens (14) is made of H-ZLAF76, the first biconcave negative lens (15) is made of H-QF8, the first biconvex positive lens (16) is made of H-LAF54, and the second biconvex positive lens (17) is made of H-ZK9A. Lens (17) is made of H-ZLAF3, the fourth meniscus positive lens (18) is made of H-ZF62, the third biconvex positive lens (19) is made of H-ZLAF71, the fifth meniscus positive lens (20) is made of H-LAF4, the second biconcave negative lens (21) is made of H-ZF62, the sixth meniscus positive lens (23) is made of ZNSE, the sixth meniscus negative lens (24), the seventh meniscus positive lens (26), and the seventh meniscus negative lens (28) are all made of Ge, and the eighth meniscus positive lens (27) is made of SILICN.

7. The multi-band common-path optical system of claim 2, wherein, The mid-wave infrared subsystem adopts a secondary imaging system. The primary image plane is located between the seventh meniscus positive lens (26) and the eighth meniscus positive lens (27). A field stop is set at the position of the primary image plane.

8. The multi-band common-path optical system of claim 2, wherein, The front surface of the seventh meniscus positive lens (26) and the rear surface of the seventh meniscus negative lens (28) are both made of high-order aspherical surfaces.

9. The multi-band common-path optical system of claim 1, wherein, The obscuration ratio of the optical system: .

10. The multi-band common-path optical system of claim 1, wherein, The optical system operates in the following wavelengths: 0.38μm–0.76μm visible light, 0.9μm–1.7μm short-wave infrared, and 3.7μm–4.8μm mid-wave infrared; the focal length is 800mm in all three wavelengths. # All are 4.

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