Visible light and short wave infrared common-caliber optical system

Abstract

The invention discloses a visible light and short wave infrared common-aperture optical system which is used for solving the technical problem that an existing multi-band common-aperture optical system cannot meet the detection requirements of large view field, high resolution and high sensitivity at the same time. The optical system comprises a visible light optical system and a short-wave infrared optical system, and a primary reflector, a secondary reflector, a beam splitter prism, a visible light relay lens group and a first imaging unit jointly form the visible light optical system; and the primary reflector, the secondary reflector, the beam splitter prism, the short-wave infrared image space telecentric relay lens group, the view field divider and the N second imaging units jointly form a short-wave infrared optical system. The optical system disclosed by the invention shares the primary reflector and the secondary reflector, so that the focal length of the optical system is increased, and the requirement of high resolution is met; and meanwhile, the short-wave infrared optical system adopts the view field divider and N second imaging units, and the large-view-field and high-sensitivity infrared detection requirements of the optical system on a dark and weak target are met through splicing of N paths of view fields.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic imaging, and particularly relates to a visible light and short-wave infrared dual-band common aperture optical system for splicing refrigerated infrared detectors with a large field of view, long focal length, high sensitivity. Background Art

[0002] With the development of aerospace technology, a single visible light or infrared spectral band can no longer fully meet the application requirements in fields such as environmental situation awareness, environmental pollution monitoring, and emergency disaster reduction. Therefore, it is necessary to utilize the advantages of multiple visible light and infrared bands for composite imaging to improve the detector capabilities and accuracy of space optical payloads, and then achieve the detection, identification, and acquisition of target information all-weather and all-day long. In recent years, multi-spectral integrated imaging has gradually become the development trend of space optical payloads at home and abroad. Currently, most multi-spectral common aperture integrated optical imaging systems adopt a catadioptric structure, which has the advantage of being easy to integrate. However, due to the mutual restriction between a large field of view and high-resolution imaging, for example, the field of view of a high-resolution system is often very small, while the focal length of a large-field-of-view system is very short and the resolution is not high, which makes it impossible for an optical system to achieve both a large field of view and high resolution imaging simultaneously. In addition, the aperture F number of a conventional catadioptric system is above 8, which cannot meet the requirements for detecting dim targets at long distances in space with a large field of view and high sensitivity.

[0003] In order to achieve large-field-of-view imaging while achieving high-resolution imaging, currently, the method of stitching imaging is mostly adopted. For example, multiple imaging systems covering different fields of view are used for external multi-lens stitching. Although this method is simple, the system has a large volume, heavy mass, and non-compact structure, and does not meet the requirements of miniaturization and lightweight of space payloads. Another example is the method of internal single-lens stitching, which performs field-of-view stitching or optical stitching on the detector. This method is mostly used in visible light systems, but there are great challenges for infrared systems, especially refrigerated infrared detectors. Due to manufacturing process limitations, the target surface size and the number of pixels of a single infrared detector are small. To achieve a large field of view, multiple infrared detectors need to be stitched. In order to improve the detection sensitivity of the system, refrigerated infrared detectors are widely used in infrared systems. However, since a cold stop is provided at the front end of the focal plane of the refrigerated infrared detector, and the distance between the cold stop and the focal plane is about 20 mm. If multiple infrared detectors are internally stitched in the dewar, on the one hand, it is necessary to customize refrigerated infrared detectors, which greatly increases the system cost, and it is often unrealistic to customize refrigerated infrared detectors. On the other hand, it will inevitably increase the incident angle of the off-axis field of view on its focal plane, thereby reducing the illuminance of the off-axis field of view. At the same time, if the incident angle of the off-axis field of view increases, it will be difficult to correct the diaphragm aberration of the optical system, which further increases the design difficulty of the optical system.

[0004] For this reason, the master's thesis "Design of Visible and Medium-Wave Infrared Dual-Band Common-Aperture Optical System" published by Guo Yulin et al. of Xi'an Technological University on CNKI in 2018 completed the optical system design for visible light and medium-wave infrared with a field of view of 0.38°×0.43°. This visible light and medium-wave infrared optical system shares a Cassegrain primary mirror and uses a dichroic filter for beam splitting. In addition, the master's thesis "Visible / Infrared Dual-Band Imaging System" published by Deng Chaolan et al. of Beijing Institute of Technology on CNKI in 2015 disclosed a visible light and long-wave infrared common optical path optical system, with a visible field of view of 0.96° and an infrared field of view of 1.75°. However, the above systems all have the defects of a small field of view and an insufficiently compact structure, and cannot meet the requirements of large field of view, high resolution imaging and high sensitivity detection.

[0005] Chinese Patent with Publication No. CN 108152973A discloses a visible light and medium-wave infrared common-aperture composite optical system. This optical system is a transmissive beam splitting structure, with an infrared focal length of 15 mm and a visible light focal length of only 22 mm. Due to the short focal length, the resolution is low, and it is impossible to achieve large field of view and high resolution imaging simultaneously.

[0006] Chinese Patent with Publication No. CN 109060128A discloses a visible light and short-wave infrared common-aperture imaging spectrometer system. This system adopts a catadioptric common-aperture structure, and the infrared field of view is only 1.86°. However, the short-wave detector is an uncooled detector, not only with a small field of view, but also unable to achieve high sensitivity detection.

[0007] In summary, existing optical systems with high sensitivity detection requirements have a large relative aperture, while high resolution requires an optical system with a long focal length, and a large imaging width requires an optical system with a large field of view. At the same time, the splicing of infrared detectors may bring unacceptable costs and difficulties and challenges in the design of optical systems. In addition, the miniaturization and lightweight requirements of space optical payloads also need to be considered. This makes existing multi-band common-aperture optical systems unable to achieve large field of view, high resolution, high sensitivity detection simultaneously, and have the disadvantages of insufficiently compact structure and heavy mass, and ultimately cannot meet the actual mission requirements. Summary of the Invention

[0008] The purpose of the present invention is to solve the technical problems that existing multi-band common-aperture optical systems cannot meet the requirements of large field of view, high resolution, high sensitivity detection simultaneously, and have an insufficiently compact structure and heavy mass, and to provide a visible light and short-wave infrared common-aperture optical system.

[0009] To achieve the above purpose, the technical solution provided by the present invention is as follows: A visible light and short-wave infrared common-aperture optical system, characterized in that: It includes a primary mirror, a secondary mirror, and a beam splitter prism arranged in sequence along the incident optical path, as well as a visible light relay lens group, a first imaging unit, a short-wave infrared image-space telecentric relay lens group, a field splitter, and N second imaging units, where N≥2; The beam splitter prism is located at the primary image plane formed by the primary mirror and the secondary mirror. The incident light reaches the beam splitter prism after passing through the primary mirror and the secondary mirror. The beam splitter prism is used to transmit the visible light in the incident light and reflect the short-wave infrared light in the incident light; The visible light relay lens group is located on the transmission optical path of the beam splitter prism; the first imaging unit is located at the image plane at the exit end of the visible light relay lens group; the primary mirror, the secondary mirror, the beam splitter prism, the visible light relay lens group, and the first imaging unit together form a visible light optical system; The short-wave infrared image-space telecentric relay lens group is an image-space telecentric optical path structure and is located on the reflection optical path of the beam splitter prism; the field splitter is located at the image plane at the exit end of the short-wave infrared image-space telecentric relay lens group and is used to split and reflect the incident field of the short-wave infrared light into N parts, and there is an overlap in the field between adjacent two parts; N second imaging units are respectively located on the reflection optical paths of the field splitter and are evenly distributed in the circumferential direction of the field splitter and are used to perform relay stitching imaging on the short-wave infrared light; the primary mirror, the secondary mirror, the beam splitter prism, the short-wave infrared image-space telecentric relay lens group, the field splitter, and N second imaging units together form a short-wave infrared optical system.

[0010] Further, the visible light relay lens group is a quasi-Gaussian lens group and includes a first lens, a second lens, a third lens, a first cemented lens, a second cemented lens, a third cemented lens, a fourth lens, and a fourth cemented lens arranged in sequence along the optical path, as well as a diaphragm; The first lens is a biconvex positive lens; the second lens is a meniscus positive lens convex toward the object side; the third lens is a meniscus negative lens convex toward the object side; the first cemented lens is composed of a biconvex positive lens and a biconcave negative lens cemented together, and the biconvex positive lens is located on the object side; the second cemented lens is composed of a biconvex positive lens and a biconcave negative lens cemented together, and the biconvex positive lens is located on the object side; the third cemented lens is composed of a biconcave negative lens and a biconvex positive lens cemented together, and the biconcave negative lens is located on the object side; the fourth lens is a biconvex positive lens; the fourth cemented lens is composed of a meniscus positive lens convex toward the object side and a meniscus negative lens convex toward the object side cemented together, and the meniscus positive lens convex toward the object side is located on the object side; The diaphragm is located between the biconcave negative lens of the first cemented lens and the biconvex positive lens of the second cemented lens.

[0011] Further, a reflector is also provided between the first lens and the second lens for turning the optical path.

[0012] Furthermore, the short-wave infrared image-space telecentric relay lens group includes a first relay lens, a second relay lens, a third relay lens, a fourth relay lens, a fifth relay lens, and a sixth relay lens arranged in sequence along the optical path; The first relay lens is a biconvex positive lens; the second relay lens is a meniscus negative lens convex toward the image side; the third relay lens is a meniscus positive lens convex toward the object side; the fourth relay lens is a meniscus negative lens convex toward the image side; the fifth relay lens is a meniscus positive lens convex toward the image side; the sixth relay lens is a biconvex positive lens.

[0013] Furthermore, each of the second imaging units includes an object-space telecentric relay lens group and a short-wave infrared detector; The object-space telecentric relay lens group includes a seventh relay lens, an eighth relay lens, a ninth relay lens, and a tenth relay lens arranged in sequence along the optical path; The seventh relay lens is a biconvex positive lens, which is arranged close to the field splitter; the eighth relay lens is a biconcave negative lens; the ninth relay lens is a meniscus negative lens convex toward the object side; the tenth relay lens is a biconvex positive lens; the short-wave infrared detector is arranged at the image plane corresponding to the light-emitting end of the tenth relay lens.

[0014] Furthermore, the field splitter is an N-sided reflector structure, and each reflecting surface is an inclined surface with an angle of 45° to the optical axis of the short-wave infrared light; N second imaging units are respectively arranged on the reflected optical paths of the N reflecting surfaces, and the seventh relay lens in each second imaging unit is arranged close to the corresponding reflecting surface in the field splitter.

[0015] Furthermore, the material of the field splitter is optical quartz glass JGS1; The short-wave infrared detector is a cooled infrared detector, and its F number ≤ 3; The first imaging unit is a visible light detector.

[0016] Furthermore, the beam splitter prism is a cube structure, which is glued by two identical 45° right-angled prisms, and a spectral beam splitting film is coated on the 45° beam splitting surface for transmitting visible light and reflecting short-wave infrared light.

[0017] Furthermore, the material of the beam splitter prism is CAF 2 。

[0018] Furthermore, the distance from the center of the beam splitter prism to the vertex of the field splitter is greater than the semi-aperture of the primary mirror; The distance from the center of the beam splitter prism to the primary mirror is greater than the semi-aperture of the short-wave infrared image-space telecentric relay lens group.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In a visible light and short-wave infrared common-aperture optical system provided by the present invention, the primary mirror, secondary mirror, beam splitter prism, visible light relay lens group and the first imaging unit together form a visible light optical system, and the primary mirror, secondary mirror, beam splitter prism, short-wave infrared image-space telecentric relay lens group, field splitter and N second imaging units together form a short-wave infrared optical system. The visible light optical system and the short-wave infrared optical system share the primary mirror and the secondary mirror, increasing the focal length of the optical system, thus meeting the requirements of high resolution. At the same time, the field splitter and N second imaging units are adopted in the short-wave infrared optical system, and through N-way field stitching, the infrared detection requirements of the optical system for large field of view and high sensitivity to dim targets are met.

[0020] 2. In a visible light and short-wave infrared common-aperture optical system provided by the present invention, the field splitter is an N-sided reflector structure, and each reflecting surface is an inclined surface at an angle of 45° with the optical axis of the short-wave infrared light. The field splitter is used for field splitting, splitting the large field of view into N small fields of view and imaging them into the corresponding short-wave infrared detectors respectively. This design on the one hand realizes the field stitching of the short-wave infrared detectors and meets the large field of view imaging requirements of the optical system; on the other hand, through the docking mode of the short-wave infrared image-space telecentric relay lens group and the object-space telecentric relay lens group, the effective connection of the front and rear optical path pupils and the matching of the cold stop are realized, thereby reducing the design difficulty of the optical system while ensuring the cold stop efficiency of the short-wave infrared detector.

[0021] 3. A visible light and short-wave infrared common-aperture optical system provided by the present invention adopts a common mirror group formed by the primary mirror and the secondary mirror, and at the same time makes a clever optical path folding for the two optical systems, reasonably utilizing the layout space, making the structure of the overall optical system quite compact, and realizing the design requirements of miniaturization and light weight of the optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic structural diagram of an embodiment of the present invention; Figure 2 is a schematic structural diagram of the visible light optical system in an embodiment of the present invention; Figure 3 is a schematic optical structure diagram of the short-wave infrared image-space telecentric relay lens group in an embodiment of the present invention (showing the beam splitter prism); Figure 4 is a schematic optical structure diagram of the object-space telecentric relay lens group in an embodiment of the present invention; Figure 5 is a schematic structural diagram of the field splitter in an embodiment of the present invention; Figure 6It is the optical transfer function curve graph of the visible light channel in the embodiment of the present invention; Figure 7 It is the optical transfer function curve graph of one of the short-wave infrared channels in the embodiment of the present invention.

[0023] The reference signs are as follows: 1 - primary mirror, 2 - secondary mirror, 3 - beam splitter prism, 4 - visible light relay lens group, 41 - first lens, 42 - second lens, 43 - third lens, 44 - first cemented lens, 45 - second cemented lens, 46 - third cemented lens, 47 - fourth lens, 48 - fourth cemented lens, 49 - mirror, 5 - short-wave infrared image-space telecentric relay lens group, 51 - first relay lens, 52 - second relay lens, 53 - third relay lens, 54 - fourth relay lens, 55 - fifth relay lens, 56 - sixth relay lens, 6 - first imaging unit, 7 - field splitter, 71 - reflecting surface, 8 - object-space telecentric relay lens group, 81 - seventh relay lens, 82 - eighth relay lens, 83 - ninth relay lens, 84 - tenth relay lens, 9 - short-wave infrared detector. Detailed implementation manners

[0024] To make the objectives, advantages and features of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Those skilled in the art should understand that these implementation manners are only used to explain the technical principle of the present invention, rather than to limit the protection scope of the present invention.

[0025] As Figure 1 shown, this embodiment provides a visible light and short-wave infrared common-aperture optical system, which includes a primary mirror 1, a secondary mirror 2 and a beam splitter prism 3 arranged in sequence along the incident light path, as well as a visible light relay lens group 4, a first imaging unit 6, a short-wave infrared image-space telecentric relay lens group 5, a field splitter 7 and N second imaging units, where N≥2.

[0026] The beam splitter prism 3 is located at the primary image plane formed by the primary mirror 1 and the secondary mirror 2. The incident light from the target object reaches the beam splitter prism 3 after passing through the primary mirror 1 and the secondary mirror 2. The beam splitter prism 3 is used to transmit the visible light in the incident light and reflect the short-wave infrared light in the incident light. The beam splitter prism 3 in this embodiment has a cube structure, which is formed by gluing two identical 45° right-angle prisms, and a spectral beam-splitting film is coated on the 45° beam-splitting surface, so as to transmit visible light (spectral band is 0.45μm - 0.75μm) and reflect short-wave infrared light (spectral band is 2μm - 3μm). In addition, the beam splitter prism 3 should have a high transmittance for visible light and short-wave infrared light, and materials such as CAF 2 etc. can be selected.

[0027] The visible light relay lens group 4 is located on the transmission optical path of the beam splitter prism 3; the first imaging unit 6 is a visible light detector, which is located at the image plane of the light-emitting end of the visible light relay lens group 4. The primary mirror 1, the secondary mirror 2, the beam splitter prism 3, the visible light relay lens group 4 and the first imaging unit 6 jointly form a visible light optical system, and the F-number of the aperture stop of the visible light optical system is ≤ 2.2.

[0028] The short-wave infrared image-space telecentric relay lens group 5 has an image-space telecentric optical path structure, which is located on the reflected optical path of the beam splitter prism 3 and is used to relay image the primary image plane formed by the primary mirror 1 and the secondary mirror 2 to the secondary image plane. The field splitter 7 is located at the image plane of the light-emitting end of the short-wave infrared image-space telecentric relay lens group 5 and is used to split and reflect the incident field of the short-wave infrared light into N parts, and there is an overlap in the field between two adjacent parts. The N second imaging units are respectively located on the reflected optical paths of the field splitter 7 and are evenly distributed in the circumferential direction of the field splitter 7 and are used to perform relay stitching imaging on the short-wave infrared light; each second imaging unit includes an object-space telecentric relay lens group 8 and a short-wave infrared detector 9. The primary mirror 1, the secondary mirror 2, the beam splitter prism 3, the short-wave infrared image-space telecentric relay lens group 5, the field splitter 7 and the N second imaging units jointly form a short-wave infrared optical system.

[0029] The primary mirror 1 and the secondary mirror 2 in this embodiment are the common mirror groups of the visible light optical system and the short-wave infrared optical system, and both the primary mirror 1 and the secondary mirror 2 are hyperboloid structures (specific optical design parameters are shown in Table 1). The incident light from the target object passes through the primary mirror 1 and the secondary mirror 2, and then the beam splitter prism 3 splits the two imaging spectral bands (visible light and short-wave infrared light) into two paths, and the imaging light beams of different spectral bands after splitting enter their respective channels for imaging. The visible light optical system in this embodiment is a secondary imaging optical path structure, including a primary image plane and a visible light image plane. The visible light image plane is the final image plane of the visible light optical system, and this final image plane coincides with the target surface of the visible light detector. The short-wave infrared optical system is a three-time imaging optical path structure, including a primary image plane, a secondary image plane and a short-wave infrared image plane. The short-wave infrared image plane is the final image plane of the short-wave infrared optical system, and this final image plane coincides with the target surface of the short-wave infrared detector 9.

[0030] As Figure 2 shown, the visible light relay lens group 4 is a Gaussian-like lens group, including a first lens 41, a second lens 42, a third lens 43, a first cemented lens 44, a second cemented lens 45, a third cemented lens 46, a fourth lens 47 and a fourth cemented lens 48 arranged in sequence along the optical path, and an aperture stop. The optical structure of the Gaussian-like lens group is approximately symmetric, each lens should have a relatively large same aperture, and the aperture stop in the Gaussian-like lens group is located between the first cemented lens 44 and the second cemented lens 45 (not shown in the figure).

[0031] In this embodiment, the first lens 41 is a biconvex positive lens. The material of this biconvex positive lens is a high refractive index material, and its refractive index should be greater than 1.75, such as HZLAF4LA, etc. The second lens 42 is a meniscus positive lens convex toward the object side; the third lens 43 is a meniscus negative lens convex toward the object side; the first cemented lens 44 is composed of a biconvex positive lens and a biconcave negative lens cemented together, and the biconvex positive lens is located on the object side; the second cemented lens 45 is composed of a biconvex positive lens and a biconcave negative lens cemented together, and the biconvex positive lens is located on the object side; the third cemented lens 46 is composed of a biconcave negative lens and a biconvex positive lens cemented together, and the biconcave negative lens is located on the object side; the fourth lens 47 is a biconvex positive lens; the fourth cemented lens 48 is composed of a meniscus positive lens convex toward the object side and a meniscus negative lens convex toward the object side cemented together, and the meniscus positive lens convex toward the object side is located on the object side; the aperture stop is located between the biconcave negative lens of the first cemented lens 44 and the biconvex positive lens of the second cemented lens 45. The optical design parameters of each lens are shown in Table 1.

[0032] To improve the compactness of the system, a reflector 49 is also provided between the first lens 41 and the second lens 42. The reflector 49 is a plane reflector, mainly used to deflect the optical path. The material used is a low expansion coefficient material, such as optical quartz glass JGS1, and a dielectric broadband reflection film is coated on the surface.

[0033] As Figure 3 shown, the short-wave infrared image-space telecentric relay lens group 5 includes a first relay lens 51, a second relay lens 52, a third relay lens 53, a fourth relay lens 54, a fifth relay lens 55, and a sixth relay lens 56 arranged in sequence along the optical path.

[0034] In this embodiment, the first relay lens 51 is a biconvex positive lens; the second relay lens 52 is a meniscus negative lens convex toward the image side; the third relay lens 53 is a meniscus positive lens convex toward the object side; the fourth relay lens 54 is a meniscus negative lens convex toward the image side; the fifth relay lens 55 is a meniscus positive lens convex toward the image side; the sixth relay lens 56 is a biconvex positive lens. The optical design parameters of each lens are shown in Table 2.

[0035] The object-space telecentric relay lens group 8 has an object-space and image-space telecentric optical path structure, that is, the chief rays of each field of view and the secondary image plane ( Figure 1Vertical to the horizontal dotted line above the medium field splitter 7 to meet the pupil matching with the short-wave infrared image-space telecentric relay lens group 5. Each object-space telecentric relay lens group 8 corresponds to a different field of view, and images the incident light beam separately in combination with the corresponding short-wave infrared detector 9. There is a certain overlap rate between the fields of view of two adjacent object-space telecentric relay lens groups 8, and the overlap rate can be adjusted by the axial position of the field splitter 7. The object-space telecentric relay lens group 8 in this embodiment should not only ensure the pupil matching with the short-wave infrared image-space telecentric relay lens group 5, but also ensure that the exit pupil completely matches the cold stop of the short-wave infrared detector 9. In the design, CVD ZNS and CAF 2 materials can be used for aberration correction.

[0036] As Figure 4 shown, each object-space telecentric relay lens group 8 includes a seventh relay lens 81, an eighth relay lens 82, a ninth relay lens 83, and a tenth relay lens 84 arranged in sequence along the optical path. Among them, the seventh relay lens 81 is a biconvex positive lens, which is arranged close to the field splitter 7; the eighth relay lens 82 is a biconcave negative lens; the ninth relay lens 83 is a meniscus negative lens convex toward the object side; the tenth relay lens 84 is a biconvex positive lens; the short-wave infrared detector 9 is arranged at the image plane at the light-emitting end of the corresponding tenth relay lens 84. The optical design parameters of each lens are shown in Table 2.

[0037] The field splitter 7 is an N-sided reflector structure, and each reflecting surface is an inclined surface at an angle of 45° with the optical axis of the short-wave infrared light; N second imaging units are respectively arranged on the reflection optical paths of the N reflecting surfaces, and the seventh relay lens 81 in each second imaging unit is arranged close to the corresponding reflecting surface in the field splitter 7.

[0038] As Figure 5 shown, the field splitter 7 in this embodiment is a four-sided reflector structure, that is, N = 4. Its top is a quadrangular pyramid structure, which is composed of 4 45° reflecting surfaces 71. The short-wave infrared light beam is reflected by the 45° reflecting surfaces 71, and the incident field of view is divided into 4 parts, and the light beams enter the 4-way object-space telecentric relay lens groups 8 behind respectively. The vertex of the quadrangular pyramid is located on the optical axis of the short-wave infrared light beam, and its bottom surface is perpendicular to the optical axis; the quadrangular pyramid structure uses a material with a low expansion coefficient, such as optical quartz glass JGS1, etc.

[0039] Combined Figure 1 and Figure 5As shown, the field splitter 7 of this embodiment divides the incident telecentric optical path into four imaging channels, and then images them onto the target surfaces of four short-wave infrared detectors 9 through four object-side telecentric relay lens groups 8 respectively. The imaging field angle of each optical path is 1.14°×0.91°, and a large field of view coverage of 2.26°×1.8° is achieved after field stitching. To ensure the integrity of the field of view after stitching, there is a certain degree of field overlap between adjacent two second imaging units (the overlap degree is about within 10%), and there is a vignetting phenomenon at the edge where two adjacent 45° reflecting surfaces 71 intersect. The size of the vignetting area of the light can be achieved by reasonably controlling the distance between the field splitter 7 and the secondary image plane and changing the height of the quadrangular pyramid structure. Under the requirement of meeting the field overlap rate, the vertex of the field splitter 7 can be located at the secondary image plane. The vignetting phenomenon at the stitching gap can be compensated by post-image vignetting correction. In this embodiment, the number of pixels occupied by adjacent two overlapping fields of view is at least greater than 11 pixels.

[0040] In this embodiment, the image plane of the short-wave infrared optical system coincides with the target surface of the short-wave infrared detector 9. The aperture stop of the short-wave infrared optical system is located in the short-wave infrared detector 9. The short-wave infrared detector 9 is a cooled infrared detector, and its aperture F number ≤ 3.

[0041] Table 1 and Table 2 respectively show the optical design parameters of each optical element in this embodiment.

[0042] Optical design parameters of the common aperture part and the visible light optical system in Table 1

[0043] Optical design parameters of the short-wave infrared optical system in Table 2

[0044] Note: The data in Table 1 and Table 2 have been rounded.

[0045] The aperture of the primary mirror 1 in this embodiment is mainly determined by the short-wave infrared optical system. At the same time, the visible light optical system should also select an appropriate aperture F number to ensure that the aperture of the primary mirror 1 is utilized as fully as possible. In order to reduce the demand for the aperture of the primary mirror 1, the visible light optical system and the short-wave infrared optical system should strictly control the optical system pupil aberration during design, so that the entrance pupil of the optical system is located near the primary mirror 1. The residual aberrations of the primary mirror 1 and the secondary mirror 2 are compensated and corrected by the corresponding relay lens groups in each channel.

[0046] Specifically, in the short-wave infrared optical system, the distance from the center of the beam-splitting prism 3 to the vertex of the field splitter 7 should be greater than the semi-aperture of the primary mirror 1, with an appropriate margin, so as to ensure that there is no structural interference between the object-space telecentric relay lens group 8 and the edge of the primary mirror 1 after beam splitting. In addition, in the short-wave infrared optical system, the distance from the center of the beam-splitting prism 3 to the primary mirror 1 should be greater than the semi-aperture of the short-wave infrared image-space telecentric relay lens group 5, with an appropriate margin, to ensure that there is no structural interference between the short-wave infrared image-space telecentric relay lens group 5 and the back of the primary mirror 1.

[0047] In this embodiment, the visible light band is 0.45μm - 0.75μm, and the short-wave infrared band is 2μm - 3μm; the focal length of the visible light optical system is 275mm, and the aperture is 130mm. The focal length of the short-wave infrared optical system is 480mm, and the aperture is 160mm; the effective pixel number of the visible light detector is 2048×2048, and the pixel size is 5.5μm×5.5μm; the effective pixel number of the short-wave infrared cooled detector is 640×512, and the pixel size is 15μm×15μm; the F number of the visible light optical system is 2.17, and the F number of the short-wave infrared optical system is 3; the field of view of the visible light optical system is 2.3°×2.3°, and the total field of view of the short-wave infrared optical system is 2.26°×1.8°; the magnification of the visible light relay lens group 4 in the visible light optical system should be between 0.3 and 0.5, preferably 0.42; the total magnification of the short-wave infrared image-space telecentric relay lens group 5 and the object-space telecentric relay lens group 8 in the short-wave infrared optical system should be between 0.6 and 0.8, preferably 0.72.

[0048] The visible light optical system of this embodiment adopts a large target surface detector and a large relative aperture design, which is beneficial to increasing the imaging field of view and further improving the detection ability of the visible light optical system for dim targets; at the same time, the short-wave infrared optical system adopts a large relative aperture design combined with the field of view stitching of 4 short-wave infrared detectors, thus meeting the infrared detection requirements of large field of view and high sensitivity for dim targets.

[0049] Figure 6 and Figure 7 are the optical transfer function curves of the visible light optical system and the short-wave infrared optical system respectively. It can be seen from the figure that the imaging quality of the optical system based on this embodiment is better, further verifying the feasibility of the scheme.

[0050] In summary, this embodiment adopts a visible light and short-wave infrared common-aperture optical system with cooled infrared detector stitching, which solves the problem that traditional multi-band common-aperture systems cannot balance large field of view, high resolution, and high-sensitivity imaging and detection, and has the characteristics of excellent imaging quality and compact structure.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A visible light and short-wave infrared co-aperture optical system, characterized in that: It comprises a primary reflector (1), a secondary reflector (2) and a beam splitter prism (3) which are arranged in sequence along an incident light path, as well as a visible light relay lens group (4), a first imaging unit (6), a short-wave infrared image-side telecentric relay lens group (5), a field of view divider (7) and N second imaging units, wherein N≥2; The beam splitter prism (3) is located at a primary image plane formed by the primary reflector (1) and the secondary reflector (2); the incident light reaches the beam splitter prism (3) after passing through the primary reflector (1) and the secondary reflector (2); the beam splitter prism (3) is used to transmit visible light in the incident light and reflect short-wave infrared light in the incident light; The visible light relay lens group (4) is located on the transmission light path of the beam splitter prism (3); the first imaging unit (6) is located at the image plane of the light output end of the visible light relay lens group (4); the primary reflector (1), the secondary reflector (2), the beam splitter prism (3), the visible light relay lens group (4) and the first imaging unit (6) together form a visible light optical system; The short-wave infrared image-side telecentric relay lens group (5) is an image-side telecentric optical path structure, which is located on the reflection optical path of the beam splitter prism (3); the field of view splitter (7) is located at the image plane of the light output end of the short-wave infrared image-side telecentric relay lens group (5), and is used to split and reflect the incident field of view of the short-wave infrared light into N parts, and the fields of view of two adjacent parts overlap; The N second imaging units are respectively located on the reflection light path of the field of view divider (7) and are evenly distributed in the circumference of the field of view divider (7) for relaying and splicing short-wave infrared light for imaging; the primary reflector (1), the secondary reflector (2), the beam splitter prism (3), the short-wave infrared image telecentric relay lens group (5), the field of view divider (7) and the N second imaging units together form a short-wave infrared optical system.

2. The visible light and short-wave infrared co-aperture optical system according to claim 1, characterized in that: The visible light relay lens group (4) is a Gaussian lens group, comprising a first lens (41), a second lens (42), a third lens (43), a first cemented lens (44), a second cemented lens (45), a third cemented lens (46), a fourth lens (47), and a fourth cemented lens (48), which are sequentially arranged along the light path, and a stop; The first lens (41) is a biconvex positive lens; The second lens (42) is a positive meniscus lens convex toward the object side; The third lens (43) is a negative meniscus lens convex toward the object side; The first cemented lens (44) is formed by cementing a biconvex positive lens and a biconcave negative lens, and the biconvex positive lens is located on the object side; The second cemented lens (45) is formed by cementing a biconvex positive lens and a biconcave negative lens, and the biconvex positive lens is located on the object side; The third cemented lens (46) is formed by cementing a double concave negative lens and a double convex positive lens, and the double concave negative lens is located on the object side; The fourth lens (47) is a biconvex positive lens; The fourth cemented lens (48) is cemented by a positive meniscus lens convex toward the object and a negative meniscus lens convex toward the object, and the positive meniscus lens convex toward the object is located on the object side; The aperture is located between the double concave negative lens of the first cemented mirror (44) and the double convex positive lens of the second cemented mirror (45).

3. The visible light and short-wave infrared co-aperture optical system according to claim 2, characterized in that: A reflector (49) is also provided between the first lens (41) and the second lens (42) for deflecting the light path.

4. The visible light and short-wave infrared co-aperture optical system according to claim 1, characterized in that: The short-wave infrared image-side telecentric relay lens group (5) comprises a first relay lens (51), a second relay lens (52), a third relay lens (53), a fourth relay lens (54), a fifth relay lens (55), and a sixth relay lens (56) which are arranged in sequence along the optical path; The first relay lens (51) is a biconvex positive lens; The second relay lens (52) is a negative meniscus lens convex toward the image side; The third relay lens (53) is a positive meniscus lens convex toward the object side; The fourth relay lens (54) is a negative meniscus lens convex toward the image side; The fifth relay lens (55) is a positive meniscus lens convex toward the image side; The sixth relay lens (56) is a double convex positive lens.

5. The visible light and short-wave infrared co-aperture optical system according to any one of claims 1 to 4, characterized in that: Each of the second imaging units comprises an object-side telecentric relay lens group (8) and a short-wave infrared detector (9); The object-side telecentric relay lens group (8) comprises a seventh relay lens (81), an eighth relay lens (82), a ninth relay lens (83), and a tenth relay lens (84) which are arranged in sequence along the optical path; The seventh relay lens (81) is a double convex positive lens, which is arranged close to the field of view divider (7); The eighth relay lens (82) is a double concave negative lens; The ninth relay lens (83) is a negative meniscus lens convex toward the object side; The tenth relay lens (84) is a biconvex positive lens; The short-wave infrared detector (9) is arranged at the image plane corresponding to the light output end of the tenth relay lens (84).

6. The visible light and short-wave infrared co-aperture optical system according to claim 5, characterized in that: The field of view divider (7) is an N-face reflector structure, each of whose reflective surfaces is an inclined surface that forms an angle of 45° with the optical axis of the short-wave infrared light; the N second imaging units are respectively arranged on the reflection light paths of the N reflective surfaces, and the seventh relay lens (81) in each second imaging unit is arranged close to the corresponding reflective surface in the field of view divider (7).

7. The visible light and short-wave infrared co-aperture optical system according to claim 6, characterized in that: The material of the field of view divider (7) is optical quartz glass JGS1; The short-wave infrared detector (9) is a refrigerated infrared detector, and its F number is ≤3; The first imaging unit (6) is a visible light detector.

8. The visible light and short-wave infrared co-aperture optical system according to claim 1, characterized in that: The beam splitter prism (3) is a cubic structure, formed by gluing two identical 45° right-angle prisms together, and a spectral beam splitter film is coated on the 45° beam splitting surface, for transmitting visible light and reflecting short-wave infrared light.

9. The visible light and short-wave infrared co-aperture optical system according to claim 8, characterized in that: The material of the beam splitter prism (3) is CAF2.

10. The visible light and short-wave infrared co-aperture optical system according to claim 1, characterized in that: The distance from the center of the beam splitter prism (3) to the vertex of the field divider (7) is greater than the semi-aperture of the main reflector (1); The distance from the center of the beam splitter prism (3) to the main reflector (1) is greater than the half-aperture of the short-wave infrared image-side telecentric relay lens group (5).

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