High-speed switching dual-band dual-field optical system based on infrared dual-color detector

Abstract

The present invention discloses a high-speed switching dual-band dual-field optical system based on an infrared two-color detector, comprising a front lens group and a rear lens group, wherein: along the optical axis direction from the object side to the image side, the front lens group sequentially comprises a front fixed lens group 1, a front fixed lens group 2, a focusing mirror, and a fixed lens group; the front lens group also comprises a magnification lens group, when the magnification lens group cuts into the optical axis between the front fixed lens group 2 and the focusing mirror, the optical system is in a short-focus position, and when the magnification lens group cuts out of the optical path, the optical system is in a long-focus position; when the optical system is in the short-focus position, an object-side imaging light beam sequentially passes through the front fixed lens group 1, the front fixed lens group 2, the magnification lens group, and the focusing mirror, forms an image after passing through the rear fixed lens group, and forms a second image on the detector after passing through the rear lens group.

Description

Technical Field

[0001] The present invention relates to an infrared optical system, in particular to a high-speed switching dual-band dual-field optical system based on an infrared dual-color detector. Background Art

[0002] Currently, infrared detectors are evolving toward new infrared focal plane cooled detectors, which expand the information obtained by adding spectral dimensions (dual / multi-band) and polarization dimensions. Infrared imaging optical systems offer strong nighttime penetration, good concealment, and resistance to interference. However, due to atmospheric transmission, medium-wave infrared and long-wave infrared (LWIR) exhibit different infrared radiation characteristics for the same target. In scenarios with stray radiation noise or near heat sources, LWIR offers stronger detection capabilities than MWIR. However, in hot and humid environments, the system receives clearer images from MWIR. Dual-field-of-view (FOV) switching zoom infrared systems enable target search, tracking, and aiming. Image stability and continuity are maintained during the switching process, preventing loss of the target image and ensuring clarity. This allows for both wide-field search and narrow-field resolution. Therefore, optical systems utilizing infrared dual-band, dual-field-of-view imaging can eliminate target camouflage and improve recognition capabilities. With the recent development of infrared cooled detectors, infrared imaging optical systems have been increasingly used in optoelectronic equipment for navigation, surveillance, and reconnaissance.

[0003] Furthermore, for dual-band infrared optical systems, the available optical materials are limited, making chromatic aberration difficult to correct. Furthermore, some materials exhibit significantly different characteristics in the two bands (e.g., germanium exhibits low dispersion in the long-wave infrared and high dispersion in the mid-wave infrared). Choosing the right optical material while simultaneously correcting for chromatic aberration in both bands presents significant design challenges for dual-band infrared optical systems. Considering a dual-band optical system as a wide-band optical system, the design challenge shifts to correcting the wide-band secondary spectrum. Secondary spectrum is a type of advanced chromatic aberration, representing the positional difference between the primary and secondary colors after chromatic aberration correction. While this value is relatively small for ordinary optical systems, it is a significant aberration that must be considered for wide-band, long-focal-length optical systems. Summary of the Invention

[0004] The purpose of the present invention is to provide a high-speed switching dual-band dual-field optical system based on an infrared two-color detector, which has the characteristics of wide imaging band range, long focal length, small size, light weight and high resolution, and the dual-band dual-field has good imaging quality.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] Provided is a high-speed switching dual-band dual-field optical system based on an infrared dual-color detector, characterized in that it includes

[0007] A front lens group and a rear lens group, wherein:

[0008] Along the optical axis from the object side to the image side, the front lens group includes, in sequence, a front fixed lens group 1, a front fixed lens group 2, a focusing lens, and a fixed lens group; the front lens group also includes a variator group. When the variator group cuts into the optical axis between the front fixed lens group 2 and the focusing lens, the optical system is in a short-focus position. When the variator group cuts out of the optical path, the optical system is in a long-focus position.

[0009] When the optical system is in the short-focus position, the object imaging beam passes through the front fixed lens group 1, the front fixed lens group 2, the magnification lens group, the focusing lens in sequence, and then passes through the rear fixed lens group to form a primary image, and finally passes through the rear lens group to form a secondary image on the detector.

[0010] Following the above technical solution, the zoom lens group includes zoom lens 1 and zoom lens 2; the rear lens group includes rear lens group 1 and rear lens group 2.

[0011] Following the above technical solution, the optical system further includes a first folding reflector and a second folding reflector, and the fixed lens group is placed between the two folding reflectors;

[0012] The optical axis of the rear lens group is parallel to the optical axis of the focusing lens;

[0013] The light beam is folded and reflected on the folding reflector 1 and then forms an image after passing through the fixed lens group. It is then folded and reflected by the folding reflector 2. The reflected light then passes through the rear lens group and forms a second image on the detector.

[0014] Following the above technical solution, the first front fixed lens group is a meniscus germanium positive lens convex to the object side, the second front fixed lens group is a meniscus zinc selenide positive lens convex to the object side, the first magnification lens is a biconcave zinc selenide negative lens, the magnification lens is a two-dimensional meniscus germanium positive lens convex to the object side, the focusing lens is a meniscus germanium positive lens convex to the object side, the first rear fixed lens group is a biconcave zinc sulfide negative lens, the first rear lens group is a meniscus zinc selenide positive lens convex to the object side, and the second rear lens group is a meniscus germanium positive lens convex to the object side.

[0015] Following the above technical solution, the focal length range of the lens of the optical system is 100mm / 300mm, and the F number is 4.

[0016] Following the above technical solution, the two folding reflectors are both plane reflectors folded 45 degrees.

[0017] Following the above technical solution, the lens of the zoom lens group is a flip-up lens, which cuts the light path by flipping and switching.

[0018] The present invention provides the following beneficial effects: the zoom lens in the optical system employs a zoom lens that switches in and out, enabling high-speed zoom switching; the narrow-field optical lens is fixed, ensuring optical axis stability during field-of-view switching; and the lens utilizes a secondary imaging structure, achieving 100% cold stop efficiency while also reducing the aperture of the front lens group. Furthermore, the lens converges dual-band infrared radiation from the same scene onto a single focal plane detector without the need for refocusing, achieving sufficiently high image quality.

[0019] Furthermore, the optical system uses two folding reflective mirrors to perform a U-shaped folding of the light path, thereby compressing the lateral and longitudinal dimensions of the system, resulting in a small volume and a compact structure.

[0020] Furthermore, the optical system is established through a reasonable initial structure, appropriate optical material selection, selection of materials with smaller dispersion as positive lenses, materials with larger dispersion as negative lenses, reasonable optical focal length distribution, correction of chromatic aberration caused by the different dispersion of infrared optical materials in the medium-wave and long-wave bands, and good correction of dual-band and dual-field aberrations. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0022] Figure 1 A schematic diagram of the optical system of the present invention;

[0023] Figure 2 A short-focus two-dimensional diagram of the optical system of the present invention;

[0024] Figure 3 A two-dimensional diagram of the optical system of the present invention with a long focal length;

[0025] Figure 4 MTF diagram of the optical system of the present invention at the short focal length of 20lp / mm;

[0026] Figure 5 MTF diagram of the optical system of the present invention at the focal end wavelength of 20lp / mm;

[0027] Figure 6 MTF diagram of the optical system of the present invention at the long wavelength and short focal length of 20lp / mm;

[0028] Figure 7 MTF diagram of the optical system of the present invention at the long wavelength focal end of 20lp / mm;

[0029] Figure 8 A diagram of the short focal end points of the optical system of the present invention;

[0030] Figure 9 A diagram of wavelength focal end points in the optical system of the present invention;

[0031] Figure 10 The long-wavelength and short-focus endpoints of the optical system of the present invention;

[0032] Figure 11 Diagram of the long wavelength focal end points of the optical system of the present invention.

[0033] In the figure, 1-front fixed lens group 1, 2-front fixed lens group 2, 3-zoom lens 1, 4-zoom lens 2, 5-focusing lens, 6-reflecting mirror 1, 7-rear fixed lens group 1, 8-reflecting mirror 2, 9-rear lens group 1, 10-rear lens group 2. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0035] like Figure 1 As shown, an embodiment of the present invention, a high-speed switching dual-band, dual-field optical system based on an infrared dual-color detector, includes a front lens group and a rear lens group. Along the optical axis from the object side to the image side, the front lens group includes, in sequence, a front fixed lens group 1, a front fixed lens group 2, a focusing lens 5, and a fixed lens group 7. The front lens group also includes a zoom lens group. When the zoom lens group cuts into the optical axis between the front fixed lens group 2 and the focusing lens, the optical system is in a short-focus position. When the zoom lens group cuts out of the optical path, the optical system is in a long-focus position. The present invention converges dual-band infrared radiation from the same scene onto the same focal plane detector without the need for refocusing, and obtains sufficiently high image quality. The image quality of the dual-band optical system approaches the diffraction limit when switching between the two fields of view.

[0036] When the optical system is in the short-focus position, the object-side imaging beam passes through front fixed lens group 1, front fixed lens group 2, the zoom lens group, and the focusing lens 5. It then passes through rear fixed lens group 7 for a primary image formation, and then through the rear lens group for a secondary image formation on the detector. This secondary imaging structure not only achieves 100% cold stop efficiency but also reduces the aperture of the front lens group.

[0037] In this embodiment, the zoom lens group includes zoom lens 1 3 and zoom lens 2 4; the rear lens group includes rear lens group 1 9 and rear lens group 2 10. The lenses of the zoom lens group are flip-up lenses that cut out the light path by flipping and switching. For example, zoom lens 1 3 and zoom lens 2 4 drive the zoom frame in and out of the system through gears to change the focal length of the system. The structural form of the switchable field of view conversion of the present invention does not require a large space to be reserved for optical elements, and with the appropriate driving method, it can achieve high-speed switching of large and small fields of view. At the same time, the narrow field of view optical lens is fixed, which ensures the stability of the optical axis when the field of view is switched, and the imaging quality is good when switching between long and short focal lengths within the dual-band range.

[0038] In another embodiment of the present invention, the optical system further includes a first deflecting mirror 6 and a second deflecting mirror 8, with the fixed lens group 7 positioned between the two deflecting mirrors. The optical axis of the rear lens group is parallel to the optical axis of the focusing lens 5. The light beam is deflected by the first deflecting mirror, passes through the rear fixed lens group, and forms a primary image. It is then deflected by the second deflecting mirror, and the reflected light passes through the rear lens group, forming a secondary image on the detector. The use of two deflecting mirrors to create a U-shaped deflection of the optical path reduces the system's lateral and longitudinal dimensions, resulting in a compact and compact structure.

[0039] In this embodiment, the high-speed switching dual-band dual-field optical system based on the infrared dual-color detector of the present invention has a focal length of 100 mm / 300 mm. Figure 2 This is a short-focus two-dimensional diagram of the optical system of the present invention, where the zoom lens 1 and the zoom lens 2 are located at Figure 1 On-axis position, focal length 100mm. Figure 3 The optical system of the present invention has a long focus two-dimensional diagram, where the zoom lens 1 3 and the zoom lens 2 2 cut out the light path and are located at Figure 1 In the flipped position, the focal length is 300mm. During zooming, the F-number remains constant at 4. When the optical system switches from short-focus 100mm to long-focus 300mm, the zoom lens 1 (3) and zoom lens 2 (4) drive the zoom frame in and out of the system via gears to change the focal length. When the zoom lens group enters the optical path, the system focal length shortens, assuming wide field of view mode. When the zoom lens group exits the optical path, the focal length lengthens, assuming narrow field of view mode, achieving clear dual-field imaging. The narrow field of view optical lens is fixed in place, ensuring optical axis stability during field of view switching.

[0040] The optical system of the present invention adopts a secondary imaging structure. The objective lens group provides the system's primary optical power, while the eyepiece group primarily corrects residual aberrations of the objective lens group and achieves pupil alignment, ensuring 100% cold stop efficiency. Materials with low dispersion are selected for the positive lens, while materials with high dispersion are used for the negative lens. Germanium lenses are used to assist in correcting spherical aberration and coma. A multi-layered structure is then optimized for aberrations in both the medium and long wavelength bands. By utilizing the varying chromatic aberration characteristics of optical materials and rationally allocating optical power and component spacing, the system achieves excellent correction of chromatic aberration in both fields of view within the required temperature range. To effectively correct chromatic aberration and balance aberrations across a wide wavelength range, the lens optical elements of the present invention utilize appropriate optical material selection and rational optical power allocation to simultaneously correct various aberrations. In the embodiments of the present invention, the optical lens materials are all made of germanium, zinc selenide, and zinc sulfide, which are commonly used materials in infrared optical systems. The front fixed lens group 1 is a positive meniscus germanium lens with a convex object surface, the front fixed lens group 2 is a positive meniscus zinc selenide lens with a convex object surface, the zoom lens 1 is a negative biconcave zinc selenide lens, the zoom lens 2 is a positive meniscus germanium lens with a convex object surface, the focusing lens 5 is a positive meniscus germanium lens with a convex object surface, the rear fixed lens group 1 is a negative biconcave zinc sulfide lens, the rear lens group 1 is a positive meniscus zinc selenide lens with a convex object surface, and the rear lens group 2 is a positive meniscus germanium lens with a convex object surface. The reflector 1 and the reflector 2 are both plane reflectors that are folded 45 degrees and are made of K9 glass.

[0041] Specifically, in one embodiment of the present invention, the optical system includes 8 lenses. The front fixed lens group 1 is a positive meniscus germanium lens convex to the object side. The front fixed lens group 2 is a positive meniscus zinc selenide lens convex to the object side. The zoom lens 3 is a negative biconcave zinc selenide lens with an aspheric coefficient of A=2.75×10 -6 , B=-3.42×10 -9 , C=1.78×10 -12 The zoom lens 4 is a positive meniscus germanium lens convex to the object side, and the focusing lens 5 is a positive meniscus germanium lens convex to the object side, with an aspheric coefficient of A = 6.41×10 -7 , B=-2.59×10 -11 , Reflector 1-6 is a K9 plane glass folded 45 degrees, the rear fixed lens group 1-7 is a biconcave zinc sulfide negative lens, and Reflector 2-8 is a K9 plane glass folded 45 degrees. The rear lens group 1-9 is a meniscus zinc selenide positive lens convex to the object side, with an aspheric coefficient of A = 5.24×10 -6 , B=-7.18×10 -9 , C=5.33×10 -13 The rear lens group 2 10 is a meniscus germanium positive lens with a convex surface facing the object.

[0042] Along the optical axis, with a wide field of view, zoom lenses 1-3 and 2-4 intersect the optical path. The distance between the vertex of the first surface of zoom lens 1-3 and the vertex of the second surface of front fixed lens group 2-2 is 58mm, the distance between the vertex of the second surface of zoom lens 1-3 and the vertex of the first surface of zoom lens 2-4 is 70mm, and the distance between the vertex of the second surface of zoom lens 2-4 and the vertex of the first surface of focusing lens 5 is 23mm. With a narrow field of view, zoom lenses 1-3 and 2-4 exit the optical path, and the distance between the vertex of the second surface of front fixed lens group 2-2 and the vertex of the first surface of focusing lens 5 is 151mm. Furthermore, the distance between the vertex of the first surface of front fixed lens group 1-1 and reflector 1-6 along the optical path is 279mm, the distance between reflector 1-6 and reflector 2-8 along the optical path is 82mm, and reflector 2-8 is 91mm away from the image plane.

[0043] like Figure 4-6 As shown in the figure, the MTF diagram of the optical system of the present invention at the short focal length of 20lp / mm, the zoom lens 1 and the zoom lens 2 are located at Figure 1 Transfer function curves for various MF fields at on-axis positions and cut-out optical paths, with focal lengths of 100mm and 300mm, respectively.

[0044] Figure 8 The optical system of the present invention is a diagram of the short focal point of the wavelength, the zoom lens 1 and the zoom lens 2 are located at Figure 1 On-axis position, the size of the diffuse spot in each field of view at medium wave with a focal length of 100mm. Figure 9 The wavelength focal end point diagram of the optical system of the present invention, the zoom lens 1 and the zoom lens 2 cut out the light path, and are located at Figure 1 The size of the diffuse spot in each field of view of the medium wave when the focal length is 300mm and the flip position is reversed. Figure 10 This is a diagram of the long-wavelength and short-focus endpoints of the optical system of the present invention, where the zoom lens 1 and the zoom lens 2 are located at Figure 1 On-axis position, the diffuse spot size of each field of view at long wavelength with a focal length of 100mm. Figure 11 This is a diagram of the long wavelength focal point of the optical system of the present invention. The zoom lens 1 and the zoom lens 2 cut out the light path and are located at Figure 1 Flip position, focal length 300mm, and the size of the diffuse spot in each field of view at long wavelength.

[0045] Furthermore, the front fixed lens group 1 and the front fixed lens group 2 with the largest aperture both adopt a spherical design, avoiding the use of an aspherical design, simplifying the processing technology, reducing costs, and easily ensuring accuracy.

[0046] The present invention has a wide wavelength range, uses a combination of dual-band optical materials with different dispersion sizes, rationally distributes optical focal length, and establishes a suitable initial structure. This enables good imaging quality in both mid-wave and long-wave infrared, with transfer functions close to the diffraction limit. Because targets exhibit different characteristics in mid-wave infrared and long-wave infrared, dual-band infrared imaging can be used to obtain more target information, thereby increasing the probability of target detection, reducing false alarm rates, and enhancing camouflage recognition capabilities. The dual-field-of-view switching zoom infrared system can search, track, and aim at targets. During the switching process between large and small fields of view, image stability and continuity can be maintained, and the target image will not be lost and can remain clear, while taking into account both large-field-of-view search and small-field-of-view resolution.

[0047] This invention differs from common-aperture dual-band infrared systems, which use a common front lens group and a rear lens group for beam separation, requiring separate medium-wave and long-wave detectors. This invention, however, is suitable for medium- and long-wave infrared dual-color detectors, eliminating the need for beam splitting and resulting in a simpler structure and smaller size. Furthermore, the zoom mechanism uses a zoom lens that switches in and out, ensuring that the optical lens remains stationary in long-focus, narrow-field-of-view conditions. This ensures optical axis stability, eliminates the need for significant space for optical components, and, when combined with an appropriate drive mechanism, enables high-speed switching between large and small fields of view.

[0048] In summary, the present invention's high-speed switchable dual-band, dual-field-of-view optical system based on an infrared dual-color detector establishes a suitable initial structure, utilizes a combination of dual-band optical materials with varying dispersion, and rationally distributes optical power, effectively correcting aberrations across a wide band. The system utilizes a secondary imaging and zoom lens flip-switch structure, enabling the secondary imaging component to compress the front lens group's aperture to achieve 100% cold stop efficiency. The switchable field-of-view structure eliminates the need for significant space for optical components and, when combined with an appropriate drive mechanism, enables high-speed switching between large and small fields of view. The lens of the present invention is suitable for high-resolution 640×512 medium- and long-wavelength dual-color cooled detectors. It features a wide band, compact size, light weight, and high resolution, while delivering excellent imaging quality across both the dual-band and dual-field-of-view.

[0049] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A high-speed switching dual-band dual-field optical system based on an infrared dual-color detector, characterized in that: It includes a front lens group and a rear lens group, wherein: Along the optical axis from the object side to the image side, the front lens group includes, in sequence, a front fixed lens group 1, a front fixed lens group 2, a focusing lens, and a fixed lens group; the front lens group also includes a variator group. When the variator group cuts into the optical axis between the front fixed lens group 2 and the focusing lens, the optical system is in a short-focus position. When the variator group cuts out of the optical path, the optical system is in a long-focus position. When the optical system is in the short-focus position, the object-side imaging beam passes through the front fixed lens group 1, the front fixed lens group 2, the zoom lens group, the focusing lens in sequence, and then passes through the rear fixed lens group to form a primary image, and finally passes through the rear lens group to form a secondary image on the detector; The zoom lens group includes a zoom lens 1 and a zoom lens 2; the rear lens group includes a rear lens group 1 and a rear lens group 2; The first front fixed lens group is a positive meniscus germanium lens with a convex surface facing the object, the second front fixed lens group is a positive meniscus zinc selenide lens with a convex surface facing the object, the first zoom lens is a negative biconcave zinc selenide lens, the second zoom lens is a positive meniscus germanium lens with a convex surface facing the object, the focusing lens is a positive meniscus germanium lens with a convex surface facing the object, the first rear fixed lens group is a negative biconcave zinc sulfide lens, the first rear lens group is a positive meniscus zinc selenide lens with a convex surface facing the object, and the second rear lens group is a positive meniscus germanium lens with a convex surface facing the object; The lens of the zoom lens group is a flip-up lens, which cuts the light path by flipping and switching.

2. The high-speed switching dual-band dual-field optical system based on an infrared dual-color detector according to claim 1 is characterized in that: The optical system further comprises a first folding reflector and a second folding reflector, wherein the fixed lens group is placed between the two folding reflectors; The optical axis of the rear lens group is parallel to the optical axis of the focusing lens; The light beam is folded and reflected on the folding reflector 1 and then forms an image after passing through the fixed lens group. It is then folded and reflected by the folding reflector 2. The reflected light then passes through the rear lens group and forms a second image on the detector.

3. The high-speed switching dual-band dual-field optical system based on infrared dual-color detectors according to claim 1 is characterized in that: The lens focal length range of this optical system is 100mm / 300mm and the F number is 4.

4. The high-speed switching dual-band dual-field optical system based on infrared dual-color detectors according to claim 2 is characterized in that: The two folding reflectors are both plane reflectors folded 45 degrees.

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