A common aperture optical system for visible light and short-wave infrared

Abstract

The present invention discloses a common-aperture optical system for visible light and short-wave infrared, which is used to solve technical problems such as the inability of existing multi-band common-aperture optical systems to simultaneously meet the requirements of large field of view, high resolution, and high sensitivity detection. The optical system includes a visible light optical system and a short-wave infrared optical system, wherein a primary reflector, a secondary reflector, a beam splitter, a visible light relay lens group, and a first imaging unit together form the visible light optical system; and a primary reflector, a secondary reflector, a beam splitter, a short-wave infrared image side telecentric relay lens group, a field of view divider, and N second imaging units together form the short-wave infrared optical system. The optical system of the present invention shares the primary reflector and the secondary reflector, which increases the focal length of the optical system and meets the requirements of high resolution. At the same time, the short-wave infrared optical system uses a field of view divider and N second imaging units, and through N-way field of view splicing, meets the optical system's requirements for large field of view and high sensitivity infrared detection of dim targets.

Description

Technical Field

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

[0002] With the advancement of aerospace technology, single visible or infrared spectral bands can no longer fully meet the application needs of environmental situational awareness, environmental pollution monitoring, and emergency disaster relief. Therefore, it is necessary to leverage the advantages of visible and infrared multi-bands for composite imaging to improve the detector capabilities and accuracy of space optical payloads, thereby enabling all-weather and all-day target detection, identification, and acquisition. In recent years, multi-spectral integrated imaging has gradually become a development trend in space optical payloads both domestically and internationally. Currently, most multi-spectral common-aperture integrated optical imaging systems utilize a catadioptric structure, which offers the advantage of ease of integration. However, the mutual constraints between a large field of view and high-resolution imaging exist. For example, high-resolution systems often have a small field of view, while large-field-of-view systems have a short focal length and low resolution, making it impossible for optical systems to simultaneously achieve both. Furthermore, the aperture of conventional catadioptric systems is generally above F-number 8, which cannot meet the requirements for large-field-of-view and high-sensitivity detection of dim targets at long distances in space.

[0003] To achieve high-resolution imaging with a wide field of view, stitching is currently the most common approach. For example, multiple imaging systems covering different fields of view are used for external multi-lens stitching. While this approach is simple, the system is large, heavy, and non-compact, failing to meet the requirements for miniaturization and lightweighting of space payloads. Another approach is to use internal stitching within a single lens to stitch the detector's field of view or optically stitch it. This approach is mostly used for visible light systems, but poses significant challenges for infrared systems, especially cooled infrared detectors. Due to manufacturing process limitations, the target size and number of pixels in a single infrared detector are relatively small, requiring the stitching of multiple infrared detectors to achieve a large field of view. In order to improve the detection sensitivity of the system, infrared systems widely use cooled infrared detectors. However, since a cold aperture is set at the front end of the focal plane of the cooled infrared detector, and the cold aperture is about 20 mm away from the focal plane, if multiple infrared detectors are spliced ​​internally in the Dewar, on the one hand, it is necessary to customize the cooled infrared detector, which greatly increases the system cost, and customized cooled infrared detectors are often unrealistic; on the other hand, it is bound to increase the incident angle of the off-axis field of view on its focal plane, thereby reducing the illumination of the off-axis field of view. At the same time, if the incident angle of the off-axis field of view increases, the aperture aberration of the optical system will be difficult to correct, thereby increasing the difficulty of designing the optical system.

[0004] To this end, Guo Yulin and others from Xi'an University of Technology published a master's thesis on CNKI in 2018, titled "Design of a Visible-Mid-Wave Infrared Dual-Band Co-Aperture Optical System." The system designed a dual-band optical system for visible light and mid-wave infrared, with a field of view of 0.38° × 0.43°. This visible and mid-wave infrared optical system shared a Cassegrain primary mirror and utilized a dichroic filter for light separation. Furthermore, Deng Chaolan and others from Beijing Institute of Technology published a master's thesis on CNKI in 2015, titled "Visible / Infrared Dual-Band Imaging System," which disclosed a co-path optical system for visible light and long-wave infrared, with a visible field of view of 0.96° and an infrared field of view of 1.75°. However, all of these systems suffer from a small field of view and a less compact structure, and cannot meet the requirements for large-field-of-view, high-resolution imaging, and high-sensitivity detection.

[0005] Chinese patent publication number CN 108152973A discloses a composite optical system with a common aperture for visible light and medium-wave infrared. This optical system is a transmissive spectroscopic structure with an infrared focal length of 15mm and a visible light focal length of only 22mm. Due to this short focal length and low resolution, it is impossible to achieve both large field of view and high-resolution imaging.

[0006] Chinese patent publication number CN 109060128A discloses a visible light and shortwave infrared co-aperture imaging spectroscopy system. The system uses a catadioptric co-aperture structure with an infrared field of view of only 1.86°. However, the shortwave detector is an uncooled detector, which not only has a small field of view but also cannot achieve high-sensitivity detection.

[0007] To sum up, existing high-sensitivity detection requires the optical system to have a large relative aperture, while high resolution requires the optical system to have a long focal length. Large imaging width requires the optical system to have a large field of view. At the same time, the splicing of infrared detectors may bring unacceptable costs and difficulties and challenges in optical system design. In addition, the miniaturization and lightweight requirements of space optical payloads must be taken into account. This makes the existing multi-band common-aperture optical system unable to achieve large field of view, high resolution, and high-sensitivity detection at the same time, and the structure is not compact enough and the weight is heavy, which 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 the existing multi-band common-aperture optical system cannot simultaneously meet the requirements of large field of view, high resolution, and high sensitivity detection, and the structure is not compact enough and the weight is heavy, and to provide a visible light and short-wave infrared common-aperture optical system.

[0009] To achieve the above objectives, the technical solutions provided by the present invention are:

[0010] A visible light and shortwave infrared co-aperture optical system, which is special in that:

[0011] It includes a primary reflector, a secondary reflector and a beam splitter prism arranged in sequence along the incident light path, as well as a visible light relay lens group, a first imaging unit, a short-wave infrared image side telecentric relay lens group, a field of view divider and N second imaging units, where N ≥ 2;

[0012] The beam splitter prism is located at the primary image plane formed by the primary reflector and the secondary reflector. The incident light reaches the beam splitter prism after passing through the primary reflector and the secondary reflector. 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.

[0013] The visible light relay lens group is located on the transmission light path of the beam splitter prism; the first imaging unit is located at the image plane of the light output end of the visible light relay lens group; the primary reflector, the secondary reflector, the beam splitter prism, the visible light relay lens group and the first imaging unit together form a visible light optical system;

[0014] The short-wave infrared image-side telecentric relay lens group is an image-side telecentric optical path structure, which is located on the reflection light path of the dichroic prism; the field of view divider is located at the image plane of the light-emitting end of the short-wave infrared image-side telecentric relay lens group, and is used to divide and reflect the incident field of view of the short-wave infrared light into N parts, and the fields of view between adjacent parts overlap; the N second imaging units are respectively located on the reflection light path of the field of view divider and are evenly distributed in the circumference of the field of view divider, and are used to relay and stitch the short-wave infrared light for imaging; the primary reflector, the secondary reflector, the dichroic prism, the short-wave infrared image-side telecentric relay lens group, the field of view divider and the N second imaging units together form a short-wave infrared optical system.

[0015] Furthermore, the visible light relay lens group is a Gaussian-like lens group, comprising a first lens, a second lens, a third lens, a first cemented lens, a second cemented lens, a third cemented lens, a fourth lens, a fourth cemented lens, and a stop, which are sequentially arranged along the optical path;

[0016] The first lens is a biconvex positive lens; the second lens is a meniscus positive lens convex toward the object; the third lens is a meniscus negative lens convex toward the object; the first cemented mirror 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 mirror 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 mirror 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 mirror is composed of a meniscus positive lens convex toward the object and a meniscus negative lens convex toward the object, and the meniscus positive lens convex toward the object is located on the object side;

[0017] The aperture is located between the double concave negative lens of the first cemented mirror and the double convex positive lens of the second cemented mirror.

[0018] Furthermore, a reflector is provided between the first lens and the second lens for redirecting the light path.

[0019] Furthermore, the short-wave infrared image side 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;

[0020] The first relay lens is a biconvex positive lens; the second relay lens is a negative meniscus lens convex toward the image side; the third relay lens is a positive meniscus lens convex toward the object side; the fourth relay lens is a negative meniscus lens convex toward the image side; the fifth relay lens is a positive meniscus lens convex toward the image side; and the sixth relay lens is a biconvex positive lens.

[0021] Furthermore, each of the second imaging units includes an object-side telecentric relay lens group and a short-wave infrared detector;

[0022] The object-side telecentric relay lens group includes a seventh relay lens, an eighth relay lens, a ninth relay lens, and a tenth relay lens sequentially arranged along the optical path;

[0023] The seventh relay lens is a biconvex positive lens, which is arranged close to the field of view divider; 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 output end of the tenth relay lens.

[0024] Furthermore, the field of view divider is an N-face reflector structure, each of which is an inclined surface with an angle of 45° to the optical axis of the short-wave infrared light; the N second imaging units are respectively arranged on the reflected light 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 of view divider.

[0025] Furthermore, the material of the field of view divider is optical quartz glass JGS1;

[0026] The short-wave infrared detector is a refrigerated infrared detector with an F number ≤ 3;

[0027] The first imaging unit is a visible light detector.

[0028] Furthermore, the beam splitter prism is a cubic structure, which is formed by gluing two identical 45° right-angle prisms together, and a spectrum splitting film is coated on the 45° beam splitting surface for transmitting visible light and reflecting short-wave infrared light.

[0029] Furthermore, the material of the beam splitter prism is CAF2.

[0030] Furthermore, the distance from the center of the beam splitter to the vertex of the field divider is greater than the semi-aperture of the main reflector;

[0031] The distance from the center of the beam splitter prism to the main reflector is greater than the half-aperture of the short-wave infrared image side telecentric relay lens group.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. In a visible light and short-wave infrared co-aperture optical system provided by the present invention, a primary reflector, a secondary reflector, a beam splitter, a visible light relay lens group and a first imaging unit together form a visible light optical system, and a primary reflector, a secondary reflector, a beam splitter, a short-wave infrared image side telecentric relay lens group, a field of view divider 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 reflector and the secondary reflector, which increases the focal length of the optical system and thus meets the requirement of high resolution; at the same time, the short-wave infrared optical system adopts a field of view divider and N second imaging units, and through N-way field of view splicing, meets the optical system's requirement for large field of view and high sensitivity infrared detection of dim targets.

[0034] 2. In a visible light and short-wave infrared co-aperture optical system provided by the present invention, a field of view divider is an N-face reflector structure, and each reflective surface is an inclined surface with a 45° angle with the optical axis of the short-wave infrared light. The field of view divider is used to divide the field of view, dividing the large field of view into N small fields of view, and imaging them into corresponding short-wave infrared detectors respectively. On the one hand, this design realizes the field of view splicing of the short-wave infrared detector, meeting the large field of view imaging requirements of the optical system; on the other hand, by docking the short-wave infrared image-side telecentric relay lens group with the object-side 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 ensuring the efficiency of the short-wave infrared detector cold stop while reducing the difficulty of optical system design.

[0035] 3. The present invention provides a common-aperture optical system for visible light and short-wave infrared, which adopts a common mirror group formed by a primary reflector and a secondary reflector, and cleverly folds the light paths of the two optical systems at the same time, rationally utilizing the layout space, making the structure of the overall optical system quite compact, and realizing the design requirements of miniaturization and lightweight of the optical system. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a structural diagram of an embodiment of the present invention;

[0037] Figure 2 1 is a schematic structural diagram of a visible light optical system according to an embodiment of the present invention;

[0038] Figure 32. This is a schematic diagram of the optical structure of the short-wave infrared image-side telecentric relay lens assembly in an embodiment of the present invention (showing the beam splitter prism);

[0039] Figure 4 Schematic diagram of the optical structure of the object side telecentric relay lens group in an embodiment of the present invention;

[0040] Figure 5 Schematic diagram of the structure of the field of view divider in an embodiment of the present invention;

[0041] Figure 6 is an optical transfer function curve diagram of the visible light channel in an embodiment of the present invention;

[0042] Figure 7 FIG. 4 is an optical transfer function curve diagram of one short-wave infrared channel according to an embodiment of the present invention.

[0043] The reference numerals are as follows:

[0044] 1-primary reflector, 2-secondary reflector, 3-beam splitter, 4-visible light relay lens group, 41-first lens, 42-second lens, 43-third lens, 44-first cemented mirror, 45-second cemented mirror, 46-third cemented mirror, 47-fourth lens, 48-fourth cemented mirror, 49-reflector, 5-shortwave infrared image side 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 divider, 71-reflecting surface, 8-object side telecentric relay lens group, 81-seventh relay lens, 82-eighth relay lens, 83-ninth relay lens, 84-tenth relay lens, 9-shortwave infrared detector. DETAILED DESCRIPTION

[0045] In order to make the purpose, advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and specific examples. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention, and are not used to limit the scope of protection of the present invention.

[0046] like Figure 1 As shown, this embodiment provides a visible light and short-wave infrared co-aperture optical system, including a primary reflector 1, a secondary reflector 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-side telecentric relay lens group 5, a field of view divider 7 and N second imaging units, where N ≥ 2.

[0047] Beam splitter prism 3 is located at the primary image plane formed by primary reflector 1 and secondary reflector 2. Incident light from the target object passes through primary reflector 1 and secondary reflector 2 before reaching beam splitter prism 3. Beam splitter prism 3 is used to transmit visible light and reflect short-wave infrared light. In this embodiment, beam splitter prism 3 has a cubic structure, constructed from two identical 45° right-angle prisms glued together. A spectral beam splitting coating is applied to the 45° beam splitting surface, allowing it to transmit visible light (with a spectrum of 0.45μm to 0.75μm) and reflect short-wave infrared light (with a spectrum of 2μm to 3μm). Furthermore, beam splitter prism 3 should have high transmittance for both visible and short-wave infrared light, and materials such as CAF2 can be used.

[0048] Visible light relay lens assembly 4 is located in the transmission light path of beam splitter prism 3. First imaging unit 6 is a visible light detector located at the image plane of the light-emitting end of visible light relay lens assembly 4. The primary reflector 1, secondary reflector 2, beam splitter prism 3, visible light relay lens assembly 4, and first imaging unit 6 together form a visible light optical system with an aperture F-number ≤ 2.2.

[0049] The short-wave infrared image-side telecentric relay lens group 5 is an image-side telecentric optical path structure located on the reflected optical path of the beam splitter 3. It is used to relay the primary image plane formed by the primary reflector 1 and the secondary reflector 2 to the secondary image plane. The field of view splitter 7 is located on the image plane at the light output end of the short-wave infrared image-side telecentric relay lens group 5. It is used to split and reflect the incident field of view of the short-wave infrared light into N parts, with the fields of view between adjacent parts overlapping. The N second imaging units are respectively located on the reflected optical path of the field of view splitter 7 and are evenly distributed around the field of view splitter 7. They are used to relay and stitch the short-wave infrared light for imaging. Each second imaging unit includes an object-side telecentric relay lens group 8 and a short-wave infrared detector 9. The primary reflector 1, the secondary reflector 2, the beam splitter 3, the short-wave infrared image-side telecentric relay lens group 5, the field of view splitter 7, and the N second imaging units together form a short-wave infrared optical system.

[0050] The primary reflector 1 and secondary reflector 2 of this embodiment form a common mirror assembly for both the visible light optical system and the short-wave infrared optical system. Both mirrors 1 and 2 have a hyperbolic structure (see Table 1 for specific optical design parameters). After incident light from the target passes through the primary reflector 1 and secondary reflector 2, the beam splitter prism 3 separates the two imaging spectral bands (visible light and short-wave infrared light) into two paths. After the splitting, the imaging beams of the different spectral bands enter their respective channels for imaging. The visible light optical system of this embodiment has a secondary imaging optical path structure, comprising 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, which coincides with the target plane of the visible light detector. The short-wave infrared optical system has a tertiary imaging optical path structure, comprising 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, which coincides with the target plane of the short-wave infrared detector 9.

[0051] like Figure 2 As shown, the visible light relay lens assembly 4 is a Gaussian-like lens assembly, 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, arranged sequentially along the optical path, and an aperture. The optical structure of the Gaussian-like lens assembly is approximately symmetrical, with each lens having a relatively large, identical aperture. The aperture in the Gaussian-like lens assembly is located between the first cemented lens 44 and the second cemented lens 45 (not shown).

[0052] In this embodiment, the first lens 41 is a biconvex positive lens. The material of the biconvex positive lens is a high refractive index material, and its refractive index should be greater than 1.75, such as HZLAF4LA. The second lens 42 is a positive meniscus lens convex toward the object; the third lens 43 is a negative meniscus lens convex toward the object; the first cemented mirror 44 is composed of a double convex positive lens and a double concave negative lens cemented together, and the double convex positive lens is located on the object side; the second cemented mirror 45 is composed of a double convex positive lens and a double concave negative lens cemented together, and the double convex positive lens is located on the object side; the third cemented mirror 46 is composed of a double concave negative lens and a double convex positive lens cemented together, and the double concave negative lens is located on the object side; the fourth lens 47 is a double convex positive lens; the fourth cemented mirror 48 is composed of 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. The optical design parameters of each lens are shown in Table 1.

[0053] In order to improve the compactness of the system, a reflector 49 is further provided between the first lens 41 and the second lens 42. The reflector 49 is a plane reflector, which mainly realizes the light path deflection. The material used is a low expansion coefficient material, such as optical quartz glass JGS1, and is coated with a full-dielectric broadband reflective film on the surface.

[0054] like Figure 3 As shown, the shortwave infrared image side 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, which are sequentially arranged along the optical path.

[0055] In this embodiment, 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; and the sixth relay lens 56 is a biconvex positive lens. The optical design parameters of each lens are shown in Table 2.

[0056] The object side telecentric relay lens group 8 is an object side image side telecentric optical path structure, that is, the main light of each field of view and the secondary image plane ( Figure 1 The object-side telescopic relay lens group 8 is perpendicular to the horizontal dashed line above the mid-field-of-view divider 7 to ensure pupil matching with the short-wave infrared image-side telescopic relay lens group 5. Each object-side telescopic relay lens group 8 corresponds to a different field of view and, in conjunction with a corresponding short-wave infrared detector 9, independently images the incident light beam. The fields of view of two adjacent object-side telescopic relay lens groups 8 have a certain overlap ratio, which can be adjusted by the axial position of the field of view divider 7. The object-side telescopic relay lens group 8 of this embodiment must ensure both pupil matching with the short-wave infrared image-side telescopic relay lens group 5 and complete matching of the exit pupil with the cold stop of the short-wave infrared detector 9. CVD ZNS and CAF2 materials can be used in the design for aberration correction.

[0057] like Figure 4 As shown, each object-side 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, which are arranged in sequence along the optical path. The seventh relay lens 81 is a biconvex positive lens located near the field divider 7; the eighth relay lens 82 is a biconcave negative lens; the ninth relay lens 83 is a negative meniscus lens convex toward the object; and the tenth relay lens 84 is a biconvex positive lens. The short-wave infrared detector 9 is located at the image plane corresponding to the light-emitting end of the tenth relay lens 84. The optical design parameters of each lens are shown in Table 2.

[0058] The field of view divider 7 is an N-face reflector structure, each of which is an inclined surface with an angle of 45° to the optical axis of the short-wave infrared light; the N second imaging units are respectively arranged on the reflected light 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 of view divider 7.

[0059] like Figure 5As shown, the field of view splitter 7 of this embodiment is a four-sided reflector structure, i.e., N=4. Its top is a quadrangular pyramid structure composed of four 45-degree reflective surfaces 71. These 45-degree reflective surfaces 71 reflect the shortwave infrared beam and split the incident field of view into four portions. The beams then enter the four-way object-side telecentric relay lens assembly 8 at the rear. The pyramid's apex is located on the optical axis of the shortwave infrared beam, and its base is perpendicular to the optical axis. The pyramid structure is made of a low-thermal expansion coefficient material, such as optical quartz glass JGS1.

[0060] Combine Figure 1 and Figure 5 As shown, the field of view splitter 7 of this embodiment splits the incoming telecentric optical path into four imaging channels, which are then imaged onto the target surfaces of four shortwave infrared detectors 9 via four object-side telecentric relay lens groups 8. Each optical path has an imaging field of view of 1.14° × 0.91°, resulting in a large field of view coverage of 2.26° × 1.8° after stitching. To ensure the integrity of the stitched field of view, there is a certain degree of overlap between two adjacent second imaging units (the overlap is within approximately 10%). However, light vignetting occurs at the intersection of two adjacent 45° reflective surfaces 71. The size of the vignetting area can be adjusted by properly controlling the distance between the field of view splitter 7 and the secondary image plane and varying the height of the pyramid structure. To meet the required field of view overlap ratio, the vertex of the field of view splitter 7 can be located at the secondary image plane. Light vignetting at the stitching gap can be compensated through post-processing image vignetting correction. In this embodiment, the number of pixels occupied by the two adjacent overlapping fields of view is at least 11.

[0061] In this embodiment, the image plane of the shortwave infrared optical system coincides with the target plane of the shortwave infrared detector 9. The aperture of the shortwave infrared optical system is located in the shortwave infrared detector 9. The shortwave infrared detector 9 is a refrigerated infrared detector with an aperture F number ≤3.

[0062] Table 1 and Table 2 respectively show the optical design parameters of each optical element in this embodiment.

[0063] Table 1 Optical design parameters of the common aperture part and visible light optical system

[0064]

[0065] Table 2 Optical design parameters of short-wave infrared optical system

[0066]

[0067] Note: The data in Table 1 and Table 2 are rounded off.

[0068] In this embodiment, the aperture of primary reflector 1 is primarily determined by the shortwave infrared optical system. Meanwhile, the visible light optical system should also select an appropriate aperture F-number to ensure full utilization of the aperture of primary reflector 1. To minimize the required aperture of primary reflector 1, the visible light and shortwave infrared optical systems should strictly control pupil aberrations during design, ensuring that the entrance pupil of the optical system is located near primary reflector 1. Residual aberrations of primary reflector 1 and secondary reflector 2 are compensated for by the corresponding relay lens groups in each channel.

[0069] Specifically, in the short-wave infrared optical system, the distance from the center of the beam splitter 3 to the vertex of the field divider 7 should be greater than the semi-aperture of the primary reflector 1, with an appropriate margin left to ensure that after the beam splitting, there is no structural interference between the object-side telescopic relay lens group 8 and the edge of the primary reflector 1. Furthermore, in the short-wave infrared optical system, the distance from the center of the beam splitter 3 to the primary reflector 1 should be greater than the semi-aperture of the short-wave infrared image-side telescopic relay lens group 5, with an appropriate margin left to ensure that there is no structural interference between the short-wave infrared image-side telescopic relay lens group 5 and the back of the primary reflector 1.

[0070] 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, and 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 cooling 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 side telecentric relay lens group 5 and the object side telecentric relay lens group 8 in the short-wave infrared optical system should be between 0.6 and 0.8, preferably 0.72.

[0071] The visible light optical system of this embodiment adopts a large target area detector and a large relative aperture design, which is conducive to increasing the imaging field of view, thereby improving the visible light optical system's detection capability of dim targets; at the same time, the short-wave infrared optical system adopts a large relative aperture design combined with a four-way short-wave infrared detector field of view splicing, thereby meeting the infrared detection requirements of dim targets with a large field of view and high sensitivity.

[0072] Figure 6 and Figure 7The optical transfer function curves of the visible light optical system and the short-wave infrared optical system are shown respectively. It can be seen from the figures that the imaging quality of the optical system in this embodiment is better, which further verifies the feasibility of the solution.

[0073] In summary, this embodiment adopts a visible light and shortwave infrared co-aperture optical system spliced ​​with cooled infrared detectors, which solves the problem that traditional multi-band co-aperture systems cannot take into account large field of view, high resolution and high sensitivity imaging and detection, and has the characteristics of excellent imaging quality and compact structure.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, 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 shortwave infrared co-aperture optical system, characterized by: The invention comprises a primary reflector (1), a secondary reflector (2) and a beam splitter prism (3) arranged in sequence along an incident light path, 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 is greater than or equal to 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 (3); the field of view splitter (7) is located at the image plane of the light-emitting 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 between adjacent parts overlap; The N second imaging units are respectively located on the reflected light path of the field of view divider (7) and are evenly distributed in the circumference of the field of view divider (7), and are used for relay splicing imaging of short-wave infrared light; the primary reflector (1), the secondary reflector (2), the beam splitter prism (3), the short-wave infrared image side 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 shortwave infrared co-aperture optical system according to claim 1, characterized in that: The visible light relay lens group (4) is a Gaussian-like 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 optical 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 side and a negative meniscus lens convex toward the object side, and the positive meniscus lens convex toward the object side 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 shortwave 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 redirecting the light path.

4. The visible light and shortwave 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 sequentially arranged 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 shortwave infrared co-aperture optical system according to any one of claims 1 to 4, characterized in that: Each of the second imaging units includes 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) arranged in sequence along the optical path; The seventh relay lens (81) is a biconvex positive lens, which is arranged close to the field divider (7); The eighth relay lens (82) is a biconcave 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-emitting end of the tenth relay lens (84).

6. The visible light and shortwave 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 which is an inclined surface with 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 reflecting surfaces, and the seventh relay lens (81) in each second imaging unit is arranged close to the corresponding reflecting surface in the field of view divider (7).

7. The visible light and shortwave 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 with an F number ≤ 3; The first imaging unit (6) is a visible light detector.

8. The visible light and shortwave 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 spectrum beam splitting film is plated on the 45° beam splitting surface, which is used to transmit visible light and reflect short-wave infrared light.

9. The visible light and shortwave 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 shortwave infrared co-aperture optical system according to claim 1, characterized in that: The distance between the center of the beam splitter (3) and the vertex of the field divider (7) is greater than the semi-aperture of the main reflector (1); The distance between the center of the beam splitter prism (3) and 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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