Dual optical path common detector infrared optical system for airborne photo-optical payload

Abstract

The present application relates to a kind of airborne photoelectric load dual optical path co-detector infrared optical system, belong to airborne photoelectric load imaging field, the infrared optical system of the airborne photoelectric load includes long focus focusing sub-system and continuous zoom sub-system, two sub-systems have common image plane, by moving switching mirror to make it cut into optical path and cut out optical path to carry out long focus focusing and continuous zoom two imaging state switching, switching mirror cut into optical path when participating in optical imaging, optical system is in long focus focusing state, the switching mirror cut out optical path when not participating in optical imaging, optical system is in continuous zoom state, optical path design is compact, ingenious, and imaging performance is excellent, can realize long focus and large zoom ratio design, and two optical systems share a mid-wave refrigeration detector, can greatly reduce the system cost of airborne photoelectric load.

Description

Technical Field

[0001] This invention relates to the field of airborne optoelectronic payload imaging technology, and more specifically to a dual-path common detector infrared optical system for airborne optoelectronic payloads. Background Technology

[0002] Medium-altitude long-endurance (MALE) UAVs are a hot topic in UAV development. They fly at higher altitudes, have longer endurance, and can perform more complex missions, providing better support for tactical operations. Compared to traditional low-altitude tactical UAVs, MALE UAVs, carrying airborne electro-optical pods, can perform tasks such as night vision navigation, wide-area persistent intelligence gathering, surveillance, target acquisition and reconnaissance, maintaining real-time situational awareness, and reconnaissance and deterrence against adversaries. Therefore, they have broad development prospects.

[0003] With the rapid development of modern drones, helicopters, and other aircraft and airborne optoelectronic systems, airborne optical technology is playing an increasingly important role in military aircraft. Airborne optoelectronic payloads, as advanced devices integrating multiple optoelectronic technologies and mounted on aviation platforms, play a crucial role in various fields due to their advantages such as high mobility, high detection accuracy, rapid response, and high imaging resolution. In the military field, airborne optoelectronic payloads, in complex electromagnetic environments, can conduct covert reconnaissance of enemy targets and achieve precise targeting through infrared and visible light imaging capabilities, providing solid and reliable intelligence support for operational decisions, thus influencing modern warfare. The civilian sector also widely benefits from the application of airborne optoelectronic payloads. In emergency rescue, they can remotely lock onto targets and transmit on-site images, assisting in rescue decision-making. In security monitoring scenarios, they can patrol and collect evidence day and night to maintain social order, and also provide technical support in areas such as forest fire prevention and marine search and rescue.

[0004] Infrared optical systems exhibit superior performance due to their strong nighttime penetration capabilities, excellent camouflage detection abilities, passive infrared radiation reception, good concealment, and resistance to interference. Generally, short-focal-length optical systems have a wider field of view but lower spatial resolution, while long-focal-length optical systems have a narrower field of view but higher spatial resolution. In long-distance target observation and other mission requirements, both target searching and aiming are necessary, necessitating an optical system with both a wide field of view for searching and high spatial resolution for aiming. Therefore, a zoom system capable of freely switching between long and short focal lengths and varying field of view can simultaneously accomplish both target searching and aiming tasks.

[0005] Multi-field-of-view or continuous zoom systems have the advantage of being able to search for targets within a wide field of view as well as target targets within a narrow field of view, hence their widespread use. To enable a wider range of target tracking and search, thereby acquiring more detailed and useful information, it is necessary to increase the system's zoom ratio. Therefore, researching and designing high zoom ratio infrared optical systems that are compact, low in complexity, and lightweight is of great significance.

[0006] The advantage of continuous zoom optical systems is that the target image remains sharp throughout the zoom process, and they can achieve any field of view transformation within the zoom range. When applied to photoelectric tracking and aiming systems, the system will not lose track of the target during continuous zooming. However, continuous zoom systems are complex in structure and difficult to assemble and adjust, making it difficult to achieve a large zoom ratio. Furthermore, simple transmission-type high zoom ratio infrared optical systems are large and heavy.

[0007] Transmissive optical systems are easy to implement continuous zoom designs, while catadioptric optical systems are easy to implement ultra-long zoom designs. The two can work together to achieve a long zoom ratio design. If they are set separately, two mid-wave cooled infrared detectors are required. However, infrared detectors, especially high-resolution infrared detectors, are expensive, which makes the overall cost of airborne optoelectronic payloads expensive and difficult to promote and apply. Summary of the Invention

[0008] To address the challenges of traditional airborne optoelectronic payload infrared optical systems that struggle to balance long focal lengths and large zoom ratios, and the increased cost of using two-path optical systems requiring two infrared detectors, this invention provides a dual-path common-detector infrared optical system for airborne optoelectronic payloads.

[0009] To achieve the above objectives, the technical solution adopted by this invention is: a dual-path co-detector infrared optical system for an airborne optoelectronic payload, comprising a long-focus fixed-focus subsystem and a continuous zoom subsystem. The long-focus fixed-focus subsystem consists of a primary reflector, a secondary reflector, a first plane reflector, a first meniscus positive lens, a second plane reflector, a first meniscus negative lens, a second meniscus positive lens, a switching reflector, a third meniscus positive lens, and a second meniscus negative lens arranged sequentially along a first optical axis. The first and second plane reflectors are both at a 45° angle to the first optical axis and their reflecting surfaces are opposite each other. The switching reflector is at a 45° angle to the first optical axis and is perpendicular to the second plane reflector. The continuous zoom subsystem consists of a fourth meniscus negative lens arranged sequentially along a second optical axis. The system comprises a positive meniscus lens, a biconcave negative lens, a biconvex positive lens, a third meniscus negative lens, a fourth meniscus negative lens, a fifth meniscus positive lens, a third plane mirror, a third meniscus positive lens, and a second meniscus negative lens. The third plane mirror forms a 45° angle with the second optical axis, thereby folding the optical path of the continuous zoom subsystem by 90°. The telephoto fixed-focus subsystem and the continuous zoom subsystem share a single imaging detector, meaning they have a common image plane. The switching between telephoto fixed-focus and continuous zoom imaging states is achieved by moving a switching mirror to enter and exit the optical path. When the switching mirror enters the optical path, it participates in optical imaging, and the optical system is in telephoto fixed-focus state. When the switching mirror exits the optical path, it does not participate in optical imaging, and the optical system is in continuous zoom state.

[0010] Furthermore, the first and second meniscus positive lenses are both bent toward the second plane mirror; the third and second meniscus positive lenses are both bent toward the image plane; the fourth and fifth meniscus positive lenses are bent toward the third plane mirror; and the third and fourth meniscus negative lenses are positioned away from the third plane mirror.

[0011] Furthermore, the primary and secondary reflectors are both made of microcrystalline glass; the first, second, switching, and third plane reflectors are all made of quartz; the first and fourth meniscus positive lenses are both made of zinc selenide (ZNSE); the first, second, second, and third meniscus negative lenses, the biconcave negative lens, the third, and fifth meniscus positive lenses are all made of single-crystal germanium (Ge); and the third, fourth, and biconvex positive lenses are all made of single-crystal silicon (SILICON).

[0012] Furthermore, the continuous zoom subsystem achieves the change of focal length by axially moving the biconcave negative lens and the biconvex positive lens. When the focal length changes from short focal length to long focal length, the biconcave negative lens moves axially away from the fourth meniscus positive lens, and the biconvex positive lens moves axially towards the fourth meniscus positive lens.

[0013] Furthermore, when the distance between the biconcave negative lens and the fourth meniscus positive lens is the closest, and the distance between the biconvex positive lens and the third meniscus negative lens is the closest, it is a short focal length with a large field of view. At this time, the continuous zoom subsystem is in the shortest focal length state of 45mm. When the distance between the biconcave negative lens and the fourth meniscus positive lens is the farthest, and the distance between the biconvex positive lens and the third meniscus negative lens is the farthest, it is a long focal length with a small field of view. At this time, the continuous zoom subsystem is in the longest focal length state of 450mm.

[0014] Furthermore, when the switching mirror moves along the axis of the second meniscus positive lens, it cuts out the optical path when it moves away from the second meniscus positive lens. The switching mirror does not participate in optical imaging, and the light reflected from the third plane mirror directly reaches the third meniscus positive lens. After being converged by the third meniscus positive lens, it reaches the second meniscus negative lens. After being diverged by the second meniscus negative lens, it is imaged on the image plane. At this time, the system is in continuous zoom imaging state. When the switching mirror moves closer to the second meniscus positive lens, it cuts into the optical path. When the switching mirror cuts into the optical path and is coaxial with the third meniscus positive lens, the light emitted from the second meniscus positive lens is reflected by the switching mirror and reaches the third meniscus positive lens. After being converged by the third meniscus positive lens, it reaches the second meniscus negative lens. After being diverged by the second meniscus negative lens, it is imaged on the image plane. At this time, the system is in telephoto fixed-focus imaging state.

[0015] Furthermore, when the system is in telephoto fixed-focus imaging mode, the first optical axis of the telephoto fixed-focus subsystem after switching the reflector coincides with the second optical axis of the continuous zoom subsystem after the third plane reflector.

[0016] Furthermore, the focal lengths of each lens satisfy the following conditions: 0.33≤f1 / f≤0.36; -0.1≤f2 / f≤-0.08; 0.4≤f4 / f≤0.5; -0.5≤f6 / f≤-0.4; 0.25≤f7 / f≤0.35; 0.03≤f9 / f≤0.04; -0.07≤f 10 / f≤-0.06;0.24≤f 12 / f≤0.26;-0.07≤f 13 / f≤-0.06;0.1≤f 14 / f≤0.2; -0.25≤f 15 / f≤-0.20;-0.2≤f 16 / f≤-0.15;0.08≤f 17 / f≤0.12; Where: f is the effective focal length of the continuous zoom subsystem at long focal length; f1 is the effective focal length of the primary mirror (1); f2 is the effective focal length of the secondary mirror (2); f4 is the effective focal length of the first meniscus positive lens (4); f6 is the effective focal length of the first meniscus negative lens (6); f7 is the effective focal length of the second meniscus positive lens (7); f9 is the effective focal length of the third meniscus positive lens (9); f 10 f is the effective focal length of the second meniscus negative lens (10); 12 f is the effective focal length of the fourth meniscus positive lens (12); 13 f is the effective focal length of the biconcave negative lens (13); 14 f is the effective focal length of the biconvex positive lens (14); 15 The effective focal length of the third meniscus negative lens (15); f 16 The effective focal length of the fourth meniscus negative lens (16); f 17 The effective focal length of the fifth crescent-shaped positive lens (17) is given.

[0017] Furthermore, the incident surface of the first meniscus positive lens, the exit surface of the second meniscus negative lens, the incident surface of the biconcave negative lens, and the incident surface of the fifth meniscus positive lens are all aspherical surfaces; the exit surface of the third meniscus negative lens is a diffractive aspherical surface.

[0018] Furthermore, the optical system operates in the 3.7μm–4.8μm band and is compatible with a mid-wave cooled detector with a resolution of 1280x1024@15μm. The focal length of the long-focus fixed-focus subsystem is 990mm, and the focal length of the continuous zoom subsystem is 45mm–450mm. The F# is 4.0, where F# is calculated as f / D, f is the focal length of the optical system, and D is the diameter of the incident pupil. The obstruction ratio of the long-focus fixed-focus subsystem is ≤0.3.

[0019] Beneficial effects: This invention addresses the specific requirements and operating environment of airborne optoelectronic payloads by integrating a continuous zoom optical system and a catadioptric telephoto fixed-focus optical system. Through optimized optical path design, the continuous zoom optical system and the catadioptric telephoto fixed-focus optical system share a single mid-wave cooled infrared detector, meaning they share a common image plane. Switching between telephoto fixed-focus and continuous zoom imaging states is achieved by switching the reflector's entry and exit optical paths. When the reflector is in the optical path, it participates in optical imaging, and the optical system is in telephoto fixed-focus mode. When the reflector is out of the optical path, it does not participate in optical imaging, and the optical system is in continuous zoom mode. The compact and ingenious optical path design achieves both telephoto capability and a large zoom ratio. Furthermore, the shared mid-wave cooled detector significantly reduces the system cost of the airborne optoelectronic payload.

[0020] The catadioptric telephoto fixed-focus subsystem of the present invention achieves a system obstruction ratio of ≤0.3 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, making it easier to detect and identify distant targets; the continuous zoom optical system of the present invention can achieve continuous focal length changes between 45 and 450 mm and has good imaging quality. Attached Figure Description

[0021] Figure 1 Optical path diagram of the optical system of this invention.

[0022] Figure 2 The optical path diagram of the optical system of the present invention in the long focal length fixed focal length state (990mm).

[0023] Figure 3 The optical path diagram of the optical system of the present invention in the continuous zoom short focal length state (45mm).

[0024] Figure 4 The optical path diagram of the optical system of the present invention in continuous zoom telephoto mode (450mm).

[0025] Figure 5 The transfer function curve of the optical system of the present invention in the long focal length fixed focal length state (990mm).

[0026] Figure 6 The transfer function curve of the optical system of the present invention in continuous zoom short focal length mode (45mm).

[0027] Figure 7 The transfer function curve of the optical system of the present invention in continuous zoom telephoto mode (450mm).

[0028] Among them, 1 is the primary reflector, 2 is the secondary reflector, 3 is the first plane reflector, 4 is the first meniscus positive lens, 5 is the second plane reflector, 6 is the first meniscus negative lens, 7 is the second meniscus positive lens, 8 is the switching reflector, 9 is the third meniscus positive lens, 10 is the second meniscus negative lens, 11 is the image plane, 12 is the fourth meniscus positive lens, 13 is the biconcave negative lens, 14 is the biconvex positive lens, 15 is the third meniscus negative lens, 16 is the fourth meniscus negative lens, 17 is the fifth meniscus positive lens, and 18 is the third plane reflector. Detailed Implementation

[0029] To make the above-mentioned 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. The purpose of disclosing the present invention is to protect all technical improvements within the scope of the present invention. In the description of the present invention, it should be understood that the terms "upper," "lower," "front," "rear," "left," "right," etc., indicating orientation or positional relationships, are only used to correspond to the accompanying drawings of this application for the convenience of describing the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation.

[0030] 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.

[0031] Throughout the manual, the same reference numerals refer to the same components. The accompanying drawings are for illustrative purposes only and are not drawn to scale.

[0032] like Figure 1 The infrared optical system of a dual-path co-detector for an airborne optoelectronic payload shown comprises a primary reflector 1, a secondary reflector 2, a first plane reflector 3, a first meniscus positive lens 4, a second plane reflector 5, a first meniscus negative lens 6, a second meniscus positive lens 7, a switching reflector 8, a third meniscus positive lens 9, a second meniscus negative lens 10, a fourth meniscus positive lens 12, a biconcave negative lens 13, a biconvex positive lens 14, a third meniscus negative lens 15, a fourth meniscus negative lens 16, a fifth meniscus positive lens 17, and a third plane reflector 18.

[0033] The dual-path co-detector infrared optical system of the airborne optoelectronic payload includes a long-focus fixed-focus subsystem and a continuous zoom subsystem. The long-focus fixed-focus subsystem is composed of a primary reflector 1, a secondary reflector 2, a first plane reflector 3, a first meniscus positive lens 4, a second plane reflector 5, a first meniscus negative lens 6, a second meniscus positive lens 7, a switching reflector 8, a third meniscus positive lens 9, and a second meniscus negative lens 10 arranged sequentially along the first optical axis. The first plane reflector 3 and the second plane reflector 5 are both at a 45° angle to the first optical axis and their reflecting surfaces are opposite each other. The switching reflector 8 is at a 45° angle to the first optical axis and is perpendicular to the second plane reflector 5.

[0034] The continuous zoom subsystem consists of a fourth meniscus positive lens 12, a biconcave negative lens 13, a biconvex positive lens 14, a third meniscus negative lens 15, a fourth meniscus negative lens 16, a fifth meniscus positive lens 17, a third plane mirror 18, a third meniscus positive lens 9, and a second meniscus negative lens 10; the third plane mirror 18 forms a 45° angle with the second optical axis, thereby folding the optical path of the continuous zoom subsystem by 90°.

[0035] The telephoto fixed-focus subsystem and the continuous zoom subsystem share a single imaging detector, meaning they share a common image plane 11. The switching mirror 8 is moved to enter and exit the optical path to switch between the telephoto fixed-focus and continuous zoom imaging states. When the switching mirror 8 enters the optical path, it participates in optical imaging, and the optical system is in the telephoto fixed-focus imaging state. When the switching mirror 8 exits the optical path, it does not participate in optical imaging, and the optical system is in the continuous zoom imaging state.

[0036] Specifically, the moving path of the switching mirror 8 is along the axis of the second meniscus positive lens 7. When the switching mirror 8 moves away from the second meniscus positive lens 7, it cuts out the optical path. The switching mirror 8 does not participate in optical imaging. The light reflected from the third plane mirror 18 directly reaches the third meniscus positive lens 9. After being converged by the third meniscus positive lens 9, it reaches the second meniscus negative lens 10. After being diverged by the second meniscus negative lens 10, it is imaged on the image plane 11. At this time, the system is in continuous zoom imaging state. When the switching mirror 8 moves closer to the second meniscus positive lens 7, it cuts into the optical path. When the switching mirror 8 cuts into the optical path and is coaxial with the third meniscus positive lens 9, the first optical axis of the telephoto zoom subsystem after the switching mirror 8 coincides with the second optical axis of the continuous zoom subsystem after the third plane mirror 18. The light rays emitted from the second meniscus positive lens 7 are reflected by the switching mirror 8 and 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 are imaged on the image plane 11. At this time, the system is in the long focal length fixed focus imaging state.

[0037] When the optical system is in telephoto fixed-focus mode, such as Figure 2 As shown, the light propagation path of the telephoto fixed-focus subsystem is as follows: infrared radiation from the object side is reflected by the primary reflector 1 and then reaches the secondary reflector 2. After being reflected by the secondary reflector 2, it reaches the first plane reflector 3. After being reflected by the first plane reflector 3, it reaches the first meniscus positive lens 4. After being converged by the first meniscus positive lens 4, it reaches the second plane reflector 5. After being reflected by the second plane reflector 5, it reaches the first meniscus negative lens 6. After being diverged by the first meniscus negative lens 6, it reaches the second meniscus positive lens 7. After being converged by the second meniscus positive lens 7, it reaches the switching reflector 8. After being reflected by the switching reflector 8, it reaches the third meniscus positive lens 9. After being converged by the third meniscus positive lens 9, it reaches the second meniscus negative lens 10. After being diverged by the second meniscus negative lens 10, it is imaged on the image plane 11.

[0038] When the optical system is in continuous zoom mode, such as Figure 3-4 As shown, the light propagation path of the continuous zoom subsystem is as follows: infrared radiation from the object side is converged by the fourth meniscus positive lens 12 and reaches the biconcave negative lens 13. After being diverged by the biconcave negative lens 13, it reaches the biconvex positive lens 14. After being converged by the biconvex positive lens 14, it reaches the third meniscus negative lens 15. After being diverged by the third meniscus negative lens 15, it reaches the fourth meniscus negative lens 16. After being diverged by the fourth meniscus negative lens 16, it reaches the fifth meniscus positive lens 17. After being converged by the fifth meniscus positive lens 17, it reaches the third plane mirror 18. After being reflected by the third plane mirror 18, it reaches the third meniscus positive lens 9. After being converged by the third meniscus positive lens 9, it reaches the second meniscus negative lens 10. After being diverged by the second meniscus negative lens 10, it is imaged on the image plane 11.

[0039] In the dual-path co-detector infrared optical system, the first meniscus positive lens 4 and the second meniscus positive lens 7 are respectively bent toward the second plane mirror 5; the third meniscus positive lens 9 and the second meniscus negative lens 10 are respectively bent toward the image plane 11; the fourth meniscus positive lens 12 and the fifth meniscus positive lens 17 are respectively bent toward the third plane mirror 18; and the third meniscus negative lens 15 and the fourth meniscus negative lens 16 are respectively set away from the third plane mirror 18.

[0040] Preferably, the primary reflector 1 and secondary reflector 2 are both made of microcrystalline glass; the first plane reflector 3, the second plane reflector 5, the switching reflector 8, and the third plane reflector 18 are all made of quartz; the first meniscus positive lens 4 and the fourth meniscus negative lens 16 are both made of zinc selenide (ZNSE); the first meniscus negative lens 6, the second meniscus positive lens 7, the second meniscus negative lens 10, the biconcave negative lens 13, the third meniscus negative lens 15, and the fifth meniscus positive lens 17 are all made of single-crystal germanium (Ge); and the third meniscus positive lens 9, the fourth meniscus positive lens 12, and the biconvex positive lens 14 are all made of single-crystal silicon (SILICON).

[0041] In the continuous zoom subsystem, the focal length is changed by axially moving the biconcave negative lens 13 and the biconvex positive lens 14. When the focal length changes from short focal length to long focal length, the biconcave negative lens 13 moves axially away from the fourth meniscus positive lens 12, and the biconvex positive lens 14 moves axially towards the fourth meniscus positive lens 12. When the distance between the biconcave negative lens 13 and the fourth meniscus positive lens 12 is the closest, and the distance between the biconvex positive lens 14 and the third meniscus negative lens 15 is the closest, it is a short focal length with a large field of view, and the continuous zoom subsystem is at its shortest focal length of 45mm. When the distance between the biconcave negative lens 13 and the fourth meniscus positive lens 12 is the farthest, and the distance between the biconvex positive lens 14 and the third meniscus negative lens 15 is the farthest, it is a long focal length with a small field of view, and the continuous zoom subsystem is at its longest focal length of 450mm.

[0042] In the dual-path common-detector infrared optical system of the present invention, the focal length of each lens satisfies the following condition: The primary reflector 1 satisfies the following condition: 0.33≤f1 / f≤0.36, where f1 is the effective focal length of the primary reflector 1 and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The secondary reflector 2 satisfies the following condition: -0.1≤f2 / f≤-0.08, where f2 is the effective focal length of the secondary reflector 2 and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The first meniscus positive lens 4 satisfies the following condition: 0.4≤f4 / f≤0.5, where f4 is the effective focal length of the first meniscus positive lens 4 and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The first meniscus negative lens 6 satisfies the following condition: -0.5≤f6 / f≤-0.4, where f6 is the effective focal length of the first meniscus negative lens 6 and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The second meniscus positive lens 7 satisfies the following condition: 0.25≤f7 / f≤0.35, where f7 is the effective focal length of the second meniscus positive lens 7 and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The third meniscus positive lens 9 satisfies the following condition: 0.03≤f9 / f≤0.04, where f9 is the effective focal length of the third meniscus positive lens 9 and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The second meniscus negative lens 10 satisfies the following condition: -0.07 ≤ f 10 / f≤-0.06, where f 10 The effective focal length of the second meniscus negative lens 10, and the effective focal length of the f-continuous zoom subsystem at long focal length; The fourth meniscus positive lens 12 satisfies the following condition: 0.24 ≤ f 12 / f≤0.26, where f 12 f is the effective focal length of the fourth meniscus positive lens 12, and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The biconcave negative lens 13 satisfies the following condition: -0.07 ≤ f 13 / f≤-0.06, where f 13 f is the effective focal length of the biconcave negative lens 13, and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The biconvex positive lens 14 satisfies the following condition: 0.1 ≤ f 14 / f≤0.2, where f 14 f is the effective focal length of the biconvex positive lens 14, and f is the effective focal length of the continuous zoom subsystem at the telephoto end. The third meniscus negative lens 15 satisfies the following condition: -0.25 ≤ f 15 / f≤-0.20, where f 15 f is the effective focal length of the third meniscus negative lens 15, and f is the effective focal length of the continuous zoom subsystem at telephoto. The fourth meniscus negative lens 16 satisfies the following condition: -0.2 ≤ f 16 / f≤-0.15, where f 16 f is the effective focal length of the fourth meniscus negative lens 16, and f is the effective focal length of the continuous zoom subsystem at telephoto. The fifth crescent-shaped positive lens 17 satisfies the following condition: 0.08 ≤ f 17 / f≤0.12, where f 17 f is the effective focal length of the fifth crescent-shaped positive lens 17, and f is the effective focal length of the continuous zoom subsystem at the telephoto end.

[0043] The technical parameters achieved by the dual-path co-detector infrared optical system of this invention are: operating wavelength: 3.7μm~4.8μm; F# :4; Telephoto fixed focal length: 990mm; Continuous zoom focal length: 45mm~450mm; Telephoto fixed focal length subsystem blockage ratio: ≤0.3. This optical system is compatible with a 1280×1024, 15μm mid-wave cooled infrared detector. Among them, 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. For specific technical specifications, please refer to Table 1.

[0044] Table 1 Technical Specifications of the Optical System of the Invention Further, as shown in Table 2, a set of specific parameters for the optical system in telephoto fixed-focus mode is given, 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 lenses 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 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.

[0045] Table 2. Detailed data of the optical system in telephoto fixed-focus state according to the embodiments of the present invention. Table 3 provides a set of specific parameters for the optical system in continuous zoom mode, 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 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.

[0046] Table 3. Detailed data of the optical system in the continuous zoom state of the embodiments of the present invention. In the dual-path co-detector infrared optical system, the incident surface of the first meniscus positive lens 4, the exit surface of the second meniscus negative lens 10, the incident surface of the biconcave negative lens 13, and the incident surface of the fifth meniscus positive lens 17 are all aspherical.

[0047] Furthermore, the surface equations of the above-mentioned aspherical surfaces are as follows: 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.

[0048] Table 4 lists the aspherical coefficients of the incident surface of the first meniscus positive lens 4, the exit surface of the second meniscus negative lens 10, the incident surface of the biconcave negative lens 13, and the incident surface of the fifth meniscus positive lens 17 according to the present invention. The table uses scientific notation; for example, 3.3625641e-008 represents 3.3625641 × 10⁻⁰. -8 .

[0049] Table 4 Aspheric coefficients of the present invention Furthermore, the exit surface of the third crescent-shaped negative lens 15 is aspherical. A continuous relief structure is machined on the aspherical substrate using diamond turning to form a diffraction surface, which satisfies the following equation: 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; HOR is the diffraction order, C1, C2, and C3 are diffraction surface coefficients, λ0 is the design center wavelength; n is the refractive index of the lens, and n0 is the refractive index of air. Table 5 lists the diffraction aspherical coefficients of the exit surface of the third meniscus negative lens (15) according to the present invention.

[0050] Table 5. Diffraction aspheric coefficients of the present invention After simulation using optical design software, such as Figure 5The figure shows the transfer function of the optical system of the present invention when it is in the telephoto fixed-focus state of 990mm. When the selected detector with a pixel size of 15µm corresponds to a characteristic frequency of 33lp / mm, the system transfer function is the lowest at 0.2, indicating that the system has excellent imaging performance.

[0051] like Figure 6 The figure shows the transfer function of the optical system of the present invention when the focal length is 45mm in continuous zoom mode. When the selected detector with a pixel size of 15µm corresponds to a characteristic frequency of 33lp / mm, the system transfer function is the lowest at 0.2, indicating that the system has excellent imaging performance. like Figure 7 The figure shows the transfer function of the optical system of the present invention when the focal length is 450mm in continuous zoom mode. When the selected detector with a pixel size of 15µm corresponds to a characteristic frequency of 33lp / mm, the system transfer function is the lowest at 0.2, indicating that the system has excellent imaging performance.

[0052] 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 dual-path common-detector infrared optical system for an airborne optoelectronic payload, comprising a long-focus fixed-focus subsystem and a continuous zoom subsystem, characterized in that, The telephoto fixed-focus subsystem consists of a primary mirror (1), a secondary mirror (2), a first plane mirror (3), a first meniscus positive lens (4), a second plane mirror (5), a first meniscus negative lens (6), a second meniscus positive lens (7), a switching mirror (8), a third meniscus positive lens (9), and a second meniscus negative lens (10) arranged sequentially along the first optical axis. The first plane mirror (3) and the second plane mirror (5) are both at a 45° angle to the first optical axis and their reflecting surfaces are opposite each other. The switching mirror (8) is at a 45° angle to the first optical axis and is perpendicular to the second plane mirror (5). The continuous zoom subsystem consists of a fourth meniscus positive lens (12), a biconcave negative lens (13), a biconvex positive lens (14), and a third meniscus negative lens (15) arranged sequentially along the second optical axis. The system consists of a fourth meniscus negative lens (16), a fifth meniscus positive lens (17), a third plane mirror (18), a third meniscus positive lens (9), and a second meniscus negative lens (10). The third plane mirror (18) is set at a 45° angle to the second optical axis, thereby turning the optical path of the continuous zoom subsystem by 90°. The long focal length fixed focal length subsystem and the continuous zoom subsystem share an imaging detector, that is, they have a common image plane (11). By moving the switching mirror (8) to cut into the optical path and cut out of the optical path, the two imaging states of long focal length fixed focal length and continuous zoom are switched. When the switching mirror (8) cuts into the optical path, it participates in optical imaging, and the optical system is in the long focal length fixed focal length imaging state. When the switching mirror (8) cuts out of the optical path, it does not participate in optical imaging, and the optical system is in the continuous zoom imaging state.

2. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 1, characterized in that, The first meniscus positive lens (4) and the second meniscus positive lens (7) are both bent toward the second plane mirror (5); the third meniscus positive lens (9) and the second meniscus negative lens (10) are both bent toward the image plane (11); the fourth meniscus positive lens (12) and the fifth meniscus positive lens (17) are bent toward the third plane mirror (18); the third meniscus negative lens (15) and the fourth meniscus negative lens (16) are set away from the third plane mirror (18).

3. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 1, characterized in that, The primary reflector (1) and secondary reflector (2) are both made of microcrystalline glass; the first plane reflector (3), the second plane reflector (5), the switching reflector (8), and the third plane reflector (18) are all made of quartz; the first meniscus positive lens (4) and the fourth meniscus negative lens (16) are both made of zinc selenide (ZNSE); the first meniscus negative lens (6), the second meniscus positive lens (7), the second meniscus negative lens (10), the biconcave negative lens (13), the third meniscus negative lens (15), and the fifth meniscus positive lens (17) are all made of single-crystal germanium (Ge); the third meniscus positive lens (9), the fourth meniscus positive lens (12), and the biconvex positive lens (14) are all made of single-crystal silicon (SILICON).

4. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 1, characterized in that, The continuous zoom subsystem achieves the change of focal length by moving the biconcave negative lens (13) and the biconvex positive lens (14) axially. When the focal length changes from short focal length to long focal length, the biconcave negative lens (13) moves axially away from the fourth meniscus positive lens (12), and the biconvex positive lens (14) moves axially towards the fourth meniscus positive lens (12).

5. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 4, characterized in that, When the distance between the biconcave negative lens (13) and the fourth meniscus positive lens (12) is the shortest and the distance between the biconvex positive lens (14) and the third meniscus negative lens (15) is the short focal length and large field of view state, the continuous zoom subsystem is in the shortest focal length state of 45mm; when the distance between the biconcave negative lens (13) and the fourth meniscus positive lens (12) is the farthest and the distance between the biconvex positive lens (14) and the third meniscus negative lens (15) is the long focal length and small field of view state, the continuous zoom subsystem is in the longest focal length state of 450mm.

6. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 1, characterized in that, The moving path of the switching mirror (8) is along the axis of the second meniscus positive lens (7). When the switching mirror (8) moves away from the second meniscus positive lens (7), it cuts out the light path. The switching mirror (8) does not participate in optical imaging. The light reflected from the third plane mirror (18) directly reaches the third meniscus positive lens (9). After being converged by the third meniscus positive lens (9), it reaches the second meniscus negative lens (10). After being diverged by the second meniscus negative lens (10), it is imaged on the image plane (11). At this time, the system is in continuous zoom mode. Imaging state: When the switching mirror (8) moves closer to the second meniscus positive lens (7), it enters the light path. When the switching mirror (8) enters the light path and is coaxial with the third meniscus positive lens (9), the light rays emitted from the second meniscus positive lens (7) are reflected by the switching mirror (8) and 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 are imaged on the image plane (11). At this time, the system is in the long focal length fixed focus imaging state.

7. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 6, characterized in that, When the system is in telephoto fixed-focus imaging state, the first optical axis of the telephoto fixed-focus subsystem after switching the reflector (8) coincides with the second optical axis of the continuous zoom subsystem after the third plane reflector (18).

8. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 1, characterized in that, The focal lengths of each lens satisfy the following conditions: 0.33≤f1 / f≤0.36;-0.1≤f2 / f≤-0.08;0.4≤f4 / f≤0.5;-0.5≤f6 / f≤-0.4;0.25≤f7 / f≤0.35;0.03≤f9 / f≤0.04;-0.07≤f 10 / f≤-0.06;0.24≤f 12 / f≤0.26;-0.07≤f 13 / f≤-0.06;0.1≤f 14 / f≤0.2; -0.25≤f 15 / f≤-0.20;-0.2≤f 16 / f≤-0.15;0.08≤f 17 / f≤0.12; Where: f is the effective focal length of the continuous zoom subsystem at long focal length; f1 is the effective focal length of the primary mirror (1); f2 is the effective focal length of the secondary mirror (2); f4 is the effective focal length of the first meniscus positive lens (4); f6 is the effective focal length of the first meniscus negative lens (6); f7 is the effective focal length of the second meniscus positive lens (7); f9 is the effective focal length of the third meniscus positive lens (9); f 10 f is the effective focal length of the second meniscus negative lens (10); 12 f is the effective focal length of the fourth meniscus positive lens (12); 13 f is the effective focal length of the biconcave negative lens (13); 14 f is the effective focal length of the biconvex positive lens (14); 15 The effective focal length of the third meniscus negative lens (15); f 16 The effective focal length of the fourth meniscus negative lens (16); f 17 The effective focal length of the fifth crescent-shaped positive lens (17) is given.

9. In the dual-path co-detector infrared optical system for an airborne optoelectronic payload according to claim 1, the incident surface of the first meniscus positive lens (4), the exit surface of the second meniscus negative lens (10), the incident surface of the biconcave negative lens (13), and the incident surface of the fifth meniscus positive lens (17) are all aspherical surfaces; the exit surface of the third meniscus negative lens (15) is a diffractive aspherical surface.

10. The dual-path common-detector infrared optical system for an airborne optoelectronic payload according to claim 1, characterized in that, This optical system operates in the 3.7μm–4.8μm wavelength band and is compatible with a mid-wave cooled detector with a resolution of 1280x1024@15μm. The long-focus fixed-focus subsystem has a focal length of 990mm, while the continuous zoom subsystem has a focal length of 45mm–450mm. # : 4.0, 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 incident pupil; the obstruction ratio of the telephoto fixed-focus subsystem is ≤0.3.

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