A compact infrared laser common aperture optical system

Abstract

This invention discloses a compact infrared laser common-aperture optical system, relating to the field of optoelectronic system technology. The system comprises a laser receiving target, a secondary mirror, an infrared laser beam splitter, a primary three-mirror assembly, and an infrared imaging target arranged sequentially along the central optical axis. The primary three-mirror assembly has a first light-passing aperture, an annular third reflective surface, and an annular primary reflective surface radially. The secondary mirror has a second light-passing aperture at its center and a second reflective surface at its image-side end. Incident light is reflected three times by the primary, second, and third reflective surfaces before reaching the beam splitter. Laser light is transmitted through the beam splitter and received by the laser receiving target through the second light-passing aperture, enabling laser ranging functionality in conjunction with a laser emitting component. Infrared light is reflected by the beam splitter and received by the infrared imaging target through the first light-passing aperture, achieving infrared imaging. This invention simplifies the system structure, reduces manufacturing and assembly difficulty, achieves system lightweighting and miniaturization, and ensures optical axis consistency and optical performance through its multi-faceted, common-aperture design.

Description

Technical Field

[0001] This invention relates to the field of optoelectronic systems technology, and in particular to a compact infrared laser common aperture optical system. Background Technology

[0002] In applications such as military reconnaissance, security monitoring, industrial inspection, and space remote sensing, optoelectronic detection equipment with all-weather, all-time operation capabilities is a core supporting component. Integrating long-wave infrared imaging with laser ranging capabilities allows for simultaneous target imaging and precise distance measurement, significantly enhancing the system's overall detection and situational awareness capabilities, and has become a significant development trend in optoelectronic systems. As various platforms continue to iterate and upgrade towards lightweight, miniaturized, and low-power consumption, increasingly stringent requirements are being placed on the size, weight, environmental adaptability, and assembly efficiency of optoelectronic payloads. Traditional optoelectronic systems are no longer suitable for the application scenarios of new platforms such as microsatellites, portable detection terminals, and lightweight airborne pods.

[0003] Current mainstream infrared and laser composite detection systems primarily employ either discrete optical paths or conventional common-aperture structures, both of which have unavoidable technical shortcomings. Systems using discrete optical paths require two independent optical components, directly leading to a larger system size and weight. Furthermore, ensuring the optical axis consistency of the two paths is difficult, and optical axis misalignment can easily occur under complex conditions such as vibration, shock, and temperature changes, causing mismatch between imaging and ranging results. In addition, redundant optical components and mechanical structures increase manufacturing costs and assembly complexity. While conventional common-aperture systems reduce size and improve basic optical axis consistency by sharing the front-end optical path, most employ transmissive or catadioptric structures. Some solutions suffer from mismatched thermal properties of optical component materials, affecting optical energy transmission efficiency and prone to performance drift over a wide temperature range. They also involve more assembly and adjustment steps, higher processing or assembly difficulty, and increased production costs.

[0004] To meet the growing demand for miniaturized payloads, aluminum-based optical components, with their advantages of low density, excellent thermal stability, passive calorimetry, and short processing cycles, are gradually becoming the preferred solution for miniaturized optoelectronic systems. Multi-mirror integrated technology, by integrating multiple optical surfaces onto a single substrate, effectively reduces the number of optical components, simplifies assembly processes, and further improves system compactness and structural stability; this technology has become a research hotspot in the industry. Despite numerous technological explorations and improvements within the industry, existing composite optical systems still struggle to achieve a comprehensive balance in terms of functional integration, structural miniaturization, environmental adaptability, and ease of assembly and adjustment. They cannot fully meet the practical application requirements of next-generation miniaturized, high-reliability infrared laser composite optoelectronic payloads. Therefore, there is an urgent need to develop a novel composite optical system to address these issues. Summary of the Invention

[0005] The purpose of this invention is to provide a compact infrared laser common aperture optical system with multiple facets and common aperture design, which simplifies the system structure, reduces the difficulty of processing and assembly, achieves system lightweighting and miniaturization, and ensures optical axis consistency and optical performance.

[0006] To achieve the above objectives, the present invention provides a compact infrared laser common aperture optical system, wherein a laser receiving target, a secondary mirror, an infrared laser beam splitter, a primary three-mirror integrated unit, and an infrared imaging target are arranged sequentially from the object side to the image side along the same central optical axis. The main three-mirror integrated component is made of aluminum alloy, and its radial arrangement from the inside out includes a first light-transmitting hole, an annular third reflective surface, and an annular main reflective surface. The third reflective surface and the main reflective surface face the object, and the first light-transmitting hole extends through the axis. The secondary mirror is made of aluminum alloy and has a second light-transmitting hole in its center that is coaxially aligned with the first light-transmitting hole. A second reflective surface is provided on the side of the secondary mirror facing the image side. The infrared laser beam splitter is made of ZnS material and is coaxially located between the secondary mirror and the main three mirrors integrated unit. Its side facing the object side is concave and its side facing the image side is convex. The incident light from the object side includes infrared light and laser light. The incident light is reflected for the first time by the primary reflector, for the second time by the secondary reflector, and for the third time by the third reflector before reaching the convex surface of the infrared laser beam splitter. The laser light is transmitted through the infrared laser beam splitter and enters the laser receiving target surface through the second light-passing aperture. The infrared light is reflected by the infrared laser beam splitter and enters the infrared imaging target surface through the first light-passing aperture.

[0007] Preferably, both the primary reflecting surface and the third reflecting surface are rotationally symmetric surfaces with the central optical axis as the axis of rotation, and both are aspherical surfaces with a quadratic coefficient of 0.

[0008] Preferably, the second reflecting surface of the secondary mirror is a rotationally symmetric convex surface with the central optical axis as the rotation axis, and it is an aspherical surface with a quadratic coefficient of 0.

[0009] Preferably, the concave and convex surfaces of the infrared laser beam splitter are both rotationally symmetric curved surfaces with the central optical axis as the rotation axis, and the convex surface is coated with a beam splitting film layer that reflects infrared light and transmits laser light.

[0010] Preferably, the photosensitive surface of the infrared imaging target is perpendicular to the central optical axis and covers the outgoing light path of the first light-transmitting hole; the photosensitive surface of the laser receiving target is perpendicular to the central optical axis and covers the outgoing light path of the second light-transmitting hole.

[0011] Preferably, the infrared light operates in the range of 8-12 μm and has an imaging focal length of 42 mm, while the laser light has a center wavelength of 905 nm.

[0012] Preferably, the aperture stop of the system is set on the main reflective surface of the main three-mirror integrated component.

[0013] Preferably, the absolute value of the optical power of the main three-mirror integrated component is between 0.03 and 0.06, the absolute value of the optical power of the secondary mirror is between 0.03 and 0.06, and the absolute value of the optical power of the infrared laser beam splitter is between 0.01 and 0.05.

[0014] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects: (1) The structure is extremely simple and the miniaturization effect is significant: Through the integrated design of the main three mirrors, the main reflective surface and the third reflective surface are integrated on the same aluminum alloy substrate, which greatly reduces the number of optical components and reduces the assembly freedom, simplifying the system structure from the root; combined with the common aperture optical path design, the axial dimension of the system and the volume of the whole machine are greatly reduced.

[0015] (2) The optical axis consistency and environmental reliability are greatly improved: the infrared imaging and laser ranging optical paths share the object-side main optical system, which eliminates the optical axis parallelism error of the aperture design in principle and achieves the precise matching of "what is measured is what is seen"; the all-aluminum-based main optical element realizes the passive calorimetric design and the material thermal expansion coefficient is highly matched. Under complex environments such as wide temperature range, vibration, and shock, it can still maintain the optical axis stability and optical performance, which greatly improves the system's environmental adaptability and long-term working reliability.

[0016] (3) The processing and assembly difficulty and manufacturing cost are significantly reduced: All optical reflective surfaces and beam splitting surfaces are aspherical with a quadratic coefficient of 0. There is no need to process complex curved surfaces such as parabolic surfaces, ellipsoidal surfaces, and hyperboloids, nor are diffractive optical elements used, which greatly reduces the processing difficulty and production cycle of ultra-precision cutting; the multi-faceted design reduces the alignment steps of component assembly and adjustment, reduces assembly and adjustment errors and labor costs, and improves product yield.

[0017] (4) Excellent optical performance and high energy utilization: The infrared optical path adopts a total reflection structure, which reduces the infrared energy loss caused by the transmission element and improves the imaging sensitivity; the system optical transfer function is close to the diffraction limit, the distortion control of the entire field of view is excellent, the imaging contrast is high, and the energy receiving efficiency of laser ranging is guaranteed at the same time, taking into account both infrared imaging quality and laser ranging accuracy.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the overall structure of a lightweight aluminum-based multifaceted infrared laser ring-shaped common aperture optical system according to an embodiment of the present invention; Figure 2 This is a modulation transfer function diagram of the infrared imaging optical path of the optical system according to an embodiment of the present invention; Figure 3 The image shows the optical system distortion diagram according to an embodiment of the present invention, wherein (a) is a distortion grid diagram and (b) is a distortion curve diagram; Figure 4 This is a diagram showing the energy concentration of the laser receiving optical path in an optical system according to an embodiment of the present invention.

[0021] Figure Labels 1. Main three-mirror integrated unit; 2. Secondary mirror; 3. Beam splitter; 4. Infrared imaging target surface; 5. Laser receiving target surface; 6. First light-transmitting aperture; 7. Second light-transmitting aperture. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] To make the above-mentioned objects, 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 and specific embodiments.

[0024] Example This embodiment discloses a lightweight, compact aluminum-based multifaceted common infrared laser ring-shaped common aperture optical system, such as... Figure 1 As shown, an aluminum-based multifaceted ring with a common aperture, consisting of two aluminum reflectors and one beam splitter, achieves an optical lens design with a focal length of 42mm and a full field-of-view distortion of 0.3%. The optical transfer functions of each field of view of the system are close to the diffraction limit, enabling simultaneous long-wave infrared imaging and laser ranging.

[0025] This system has a central optical axis extending from the object side to the image side, and all optical components are coaxially arranged with reference to this central optical axis. Along the central optical axis, from the object side to the image side, the following components are coaxially arranged: laser receiving target surface 5, secondary mirror 2, infrared laser beam splitter 3, main three-mirror integrated unit 1, and infrared imaging target surface 4. The core composition and parameters of each component are as follows: The main three-mirror integrated component 1 is made of aluminum alloy and is formed by ultra-precision machining. It is the core optical component of the system and its absolute optical power is 0.0413 (meeting the design range of 0.03 < absolute optical power < 0.06). With the central optical axis as the center, the radial direction from the inside to the outside is provided with a first light-transmitting hole 6, an annular third reflecting surface, and an annular main reflecting surface. The third reflecting surface and the main reflecting surface are both facing the object side. The first light-transmitting hole 6 runs through the entire main three-mirror integrated component 1 along the axial direction of the central optical axis.

[0026] Secondary mirror 2: It is made of aluminum alloy and has an absolute optical power of 0.0497 (satisfying the design range of 0.03 < absolute optical power < 0.06). The center of the secondary mirror 2 has a second light-transmitting hole 7 that is coaxially aligned with the first light-transmitting hole 6. The side of the secondary mirror 2 facing the image side is provided with a second reflecting surface. This second reflecting surface and the main reflecting surface of the main three-mirror integrated component 1 are arranged at intervals along the central optical axis.

[0027] Infrared laser beam splitter 3: Made of zinc sulfide (ZnS) material, its absolute optical power is 0.034 (satisfying the design range of 0.01 < absolute optical power < 0.05); beam splitter 3 is coaxially arranged between secondary mirror 2 and main three-mirror integrated component 1, with its object-side side being concave and its image-side side being convex, and the convex side being coated with a beam splitting film layer for infrared reflection and laser transmission.

[0028] Infrared imaging target 4: It adopts a long-wave infrared focal plane detector with a focal plane diagonal of 2.55mm. The photosensitive surface is set perpendicular to the central optical axis and completely covers the output light path of the first light-passing hole 6.

[0029] Laser receiving target 5: It adopts a laser receiving detector with a focal plane size of 1mm. The photosensitive surface is set perpendicular to the central optical axis and completely covers the output light path of the second light-passing hole 7.

[0030] The dimensional parameters of each component are shown in the table below:

[0031] The system works as follows: After the incident light from the object side enters the system along the central optical axis, it propagates and is detected by beam splitting according to the following path: The incident light first enters the main reflecting surface of the main three-mirror integrated component 1, undergoes the first reflection by the main reflecting surface, and is then refracted towards the object side and entered the second reflecting surface of the secondary mirror 2. The light rays undergo a second reflection at the second reflecting surface of the secondary mirror 2, and are then refracted towards the image side and incident on the third reflecting surface of the main three-mirror integrated component 1; The light beam undergoes a third reflection via the third reflecting surface, and is then deflected toward the object side and incident on the convex surface of the infrared laser beam splitter 3; After the light reaches the infrared laser beam splitter 3, it is split: the laser band light passes through the infrared laser beam splitter 3, passes through the second light-transmitting hole 7 of the secondary mirror 2 along the central optical axis, and finally enters the laser receiving target surface 5 to realize the laser ranging function; the infrared band light is reflected by the convex surface of the infrared laser beam splitter 3, passes through the first light-transmitting hole 6 of the main three-mirror integrated component 1 along the central optical axis, and finally enters the infrared imaging target surface 4 to realize the infrared imaging function.

[0032] In this embodiment, the main reflective surface and the third reflective surface of the main three-mirror integrated component 1, the second reflective surface of the secondary mirror 2, and the beam splitting surface of the infrared laser beam splitter 3 are all aspherical with a quadratic coefficient of 0. The system does not contain complex curved surface elements such as parabolic surfaces, ellipsoidal surfaces, hyperboloids, or diffractive optical elements, which greatly reduces the difficulty of processing and assembly.

[0033] The system aperture stop is set on the main reflective surface of the main three-mirror integrated component 1. The infrared imaging optical path operates in the 8~12μm band, the laser receiving optical path operates at the center wavelength of 905nm, the system has a light-transmitting aperture of 40mm and a total length of 23.6mm. The system achieves lightweight, miniaturization and passive calorimetry through the aluminum-based integrated design, and can maintain stable optical performance and optical axis consistency in a wide temperature range environment.

[0034] To verify the effectiveness of the optical performance of this technical solution, a comprehensive performance analysis is conducted in conjunction with the attached figures: Figure 2 The modulation transfer function (MTF) diagram of the infrared imaging optical path shows that the MTF curves of each field of view of the system's infrared imaging optical path are close to the diffraction limit, and the curves are smooth without obvious drops. The on-axis and off-axis field of view imaging resolution and contrast performance are excellent, and the infrared thermal imaging details of the target can be clearly restored. This fully demonstrates that the total reflection annular optical path and the aspherical design with a quadratic coefficient of 0 can guarantee high-quality output of long-wave infrared imaging.

[0035] Figure 3 The image shows the optical path distortion of infrared imaging, where (a) is the distortion grid diagram and (b) is the distortion curve diagram. The distortion of the entire field of view of the system is controlled within 0.3%, the distortion grid is regular and there is no obvious twisting, the distortion curve is stable and there are no violent fluctuations, the imaging geometric distortion is extremely low, which can ensure the shape restoration accuracy of the target infrared imaging and meet the requirements of high-precision imaging detection.

[0036] Figure 4 The diagram shows the energy concentration of the laser receiving optical path. The laser optical path has an excellent energy focusing effect on the point source, with a regular spot and high energy concentration. The laser signal transmission loss is small and the receiving efficiency is high, which can ensure the response sensitivity and measurement accuracy of laser ranging. This verifies the rationality of the beam splitting design of infrared reflection and laser transmission and the coaxial optical path layout.

[0037] The above performance results show that the optical system of this embodiment achieves high-resolution, low-distortion imaging at the infrared imaging end and high energy receiving efficiency at the laser ranging end. The performance of both optical paths meets the design expectations. The system design is reasonable and the scheme is effective, which can meet the engineering application requirements of lightweight optoelectronic payloads.

[0038] The remaining technical features in the above embodiments can be flexibly selected by those skilled in the art to meet different specific practical needs according to actual circumstances. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims. In the above description, numerous specific details have been set forth to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that these specific details are not necessary to implement the present invention. In other instances, to avoid obscuring the present invention, well-known techniques, such as specific construction details, operating conditions, and other technical conditions, have not been specifically described.

[0039] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A compact infrared laser common aperture optical system, characterized in that, Along the same central optical axis, from the object side to the image side, a laser receiving target, a secondary mirror, an infrared laser beam splitter, a main three-mirror assembly, and an infrared imaging target are arranged sequentially. The main three-mirror integrated component is made of aluminum alloy, and its radial arrangement from the inside out includes a first light-transmitting hole, an annular third reflective surface, and an annular main reflective surface. The third reflective surface and the main reflective surface face the object, and the first light-transmitting hole extends through the axis. The secondary mirror is made of aluminum alloy and has a second light-transmitting hole in its center that is coaxially aligned with the first light-transmitting hole. A second reflective surface is provided on the side of the secondary mirror facing the image side. The infrared laser beam splitter is made of ZnS material and is coaxially located between the secondary mirror and the main three mirrors integrated unit. Its side facing the object side is concave and its side facing the image side is convex. The incident light from the object side includes infrared light and laser light. The incident light is reflected for the first time by the primary reflector, for the second time by the secondary reflector, and for the third time by the third reflector before reaching the convex surface of the infrared laser beam splitter. The laser light is transmitted through the infrared laser beam splitter and enters the laser receiving target surface through the second light-passing aperture. The infrared light is reflected by the infrared laser beam splitter and enters the infrared imaging target surface through the first light-passing aperture.

2. The compact infrared laser common aperture optical system according to claim 1, characterized in that: Both the primary reflecting surface and the third reflecting surface are rotationally symmetric surfaces with the central optical axis as the axis of rotation, and both are aspherical surfaces with a quadratic coefficient of 0.

3. The compact infrared laser common aperture optical system according to claim 1, characterized in that: The second reflecting surface of the secondary mirror is a rotationally symmetric convex surface with the central optical axis as the rotation axis, and it is an aspherical surface with a quadratic coefficient of 0.

4. A compact infrared laser common aperture optical system according to claim 1, characterized in that: The concave and convex surfaces of the infrared laser beam splitter are both rotationally symmetric curved surfaces with the central optical axis as the axis of rotation, and the convex surface is coated with a beam splitting film layer that reflects infrared light and transmits laser light.

5. A compact infrared laser common aperture optical system according to claim 1, characterized in that: The photosensitive surface of the infrared imaging target is perpendicular to the central optical axis and covers the output light path of the first light-transmitting aperture; the photosensitive surface of the laser receiving target is perpendicular to the central optical axis and covers the output light path of the second light-transmitting aperture.

6. A compact infrared laser common aperture optical system according to claim 1, characterized in that: The infrared light operates in the 8-12 μm band and has an imaging focal length of 42 mm. The laser light has a center wavelength of 905 nm.

7. A compact infrared laser common aperture optical system according to claim 1, characterized in that: The system's aperture stop is positioned on the main reflecting surface of the main three-mirror assembly.

8. A compact infrared laser common aperture optical system according to claim 1, characterized in that: The absolute value of the optical power of the main three-mirror integrated component is between 0.03 and 0.06, the absolute value of the optical power of the secondary mirror is between 0.03 and 0.06, and the absolute value of the optical power of the infrared laser beam splitter is between 0.01 and 0.05.

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