Athermalization long-wave infrared continuous zooming optical system

Abstract

The utility model relates to the technical field of optical lenses, in particular to an athermalization long-wave infrared continuous zoom optical system, which comprises a front fixed group lens, a zoom group lens, a compensation group lens, a diaphragm, a rear fixed group lens and an imaging surface which are sequentially arranged along the same optical axis from an object space to an image space, the front fixed group lens is used for converging infrared radiation of scenery; the zoom group lens can move along the optical axis, and the focal length and focusing compensation are changed by adjusting the distance between the zoom group lens and the front fixed group lens; the compensation group lens and the rear fixed group lens can move along the optical axis and are used for compensating image plane drift caused by movement of the zoom group lens and compensating image plane thermal defocus at different working temperatures. According to the utility model, continuous and smooth zooming and clear imaging can be realized in a temperature range of-30 DEG C to + 60 DEG C and a focal length range of 30-240 mm; the optical total length is small, the structure is compact, and the infrared detector is adaptive to a 640 * 512 12 [mu] m domestic long-wave uncooled infrared detector.

Description

TECHNICAL FIELD

[0001] The utility model relates to optical lens technical field especially relates to a kind of athermal long-wave infrared continuous zoom optical system. BACKGROUND

[0002] Compared with traditional visible light imaging technology, infrared spectrum thermal imaging technology uses the heat radiation of object to obtain the image of target object, can penetrate jungle, thick fog etc. to find hidden target, and has unique advantage in target detection and tracking. Especially long-wave infrared band, for various weather, such as rain, snow, fog, haze etc. exist high transmittance, propagation distance increases substantially, and detection performance is stronger. But long-wave infrared zoom optical system relative to mid-wave infrared zoom optical system there are few materials available, system high temperature environment athermalization difficulty problem.

[0003] The focal length of traditional infrared thermal imager is fixed, only the target in a certain field of view or area can be observed, which is not conducive to search and observation. In this scenario, it is usually required that the target can be clearly imaged within the zoom range, and the problem of environmental temperature affecting image quality is solved.

[0004] Chinese patent application CN 211236425 U discloses a 5 times long-wave double-view two-grade zoom infrared optical system, wherein the focal length of lens is 15-75mm, so the zoom range is shorter; Chinese patent application CN 211180375 U discloses a compact three-element continuous zoom long-wave infrared optical system adopting secondary imaging structure, and the three-element zoom structure realizes 10X zoom, but the system cannot solve the problem of environmental temperature affecting imaging quality. That is to say, the infrared optical system in the prior art is difficult to have good performance in both zoom range and temperature range. UTILITY MODEL CONTENT

[0005] The utility model aims at providing a kind of athermal long-wave infrared continuous zoom optical system, can be continuously smoothly zoomed in-30~+60 ℃ temperature range and 30~240mm focal length range, and clearly imaged.

[0006] In order to achieve the above purpose, the utility model provides the following technical scheme:

[0007] An athermal long-wave infrared continuous zoom optical system includes, from the object side to the image side, a front fixed group of lenses, a variable magnification group of lenses, a compensation group of lenses, a diaphragm, a rear fixed group of lenses, and an imaging surface arranged in sequence along the optical axis.

[0008] The front fixed group lens is used for converging infrared radiation of a scene; the variable magnification group lens is movable along the optical axis, and the distance between the variable magnification group lens and the front fixed group lens is adjusted to change the focal length and focus compensation; one of the compensation group lens and the rear fixed group lens is movable along the optical axis, and is used for compensating for image plane drift caused by movement of the variable magnification group lens and compensating for image plane thermal defocus at different working temperatures.

[0009] In the above scheme, the distance between the variable magnification group lens and the front fixed group lens is adjusted to change the focal length, so as to obtain a larger focal length range; the compensation group lens and the rear fixed group lens are movable along the optical axis, so as to correct residual aberration and obtain a larger temperature range; therefore, the above scheme can realize continuous and smooth zooming in a larger temperature range and a focal length range, and clear imaging.

[0010] In the further optimized scheme, the front fixed group lens comprises a front fixed first lens and a front fixed second lens, both of which are meniscus positive lenses bending towards the image side; the variable magnification group lens comprises a variable magnification first lens and a variable magnification second lens, both of which are meniscus negative lenses bending towards the image side; the compensation group lens comprises a compensation lens, which is a meniscus positive lens bending towards the image side; the rear fixed group lens comprises a rear fixed first lens and a rear fixed second lens, the rear fixed first lens is a meniscus negative lens bending towards the image side, and the rear fixed second lens is a meniscus positive lens bending towards the image side; the variable magnification first lens, the variable magnification second lens, the compensation lens and the rear fixed first lens are movable along the optical axis.

[0011] In the above scheme, the front fixed group lens collects light and bears large optical power, and determines the physical aperture size of the system and the correction of initial optical distortion; two lenses can meet the requirements and make the structure compact; the variable magnification group lens bears the zoom function of the system, and two lenses can make zooming more accurate and control the path of light; the compensation group lens is used for adjusting the image plane position and compensating for image plane drift caused by movement of the variable magnification group; a single lens can complete the compensation, and no additional lens is needed to correct complex aberration, thereby reducing the use of lenses; the rear fixed group lens is used for temperature compensation and correction of residual aberration of the front group.

[0012] The concave surface of the front fixed first lens, the concave surface of the front fixed second lens, the concave surface of the variable magnification first lens, the convex surface of the variable magnification second lens and the convex surface of the compensation lens are all even aspheric structures, and the even aspheric structures satisfy the condition x represents the distance from the vertex of the aspheric surface to the height r position of the aspheric surface along the optical axis direction, c is the curvature, k represents the surface conic coefficient, A, B, C and D represent the even aspheric surface parameters respectively.

[0013] The convex surface of the front fixed first lens, the convex surface of the front fixed second lens, the convex surface of the variable first lens, the concave surface of the variable second lens, the concave surface of the compensation lens, the convex surface of the rear fixed first lens, the concave surface of the rear fixed first lens, the convex surface of the rear fixed second lens and the concave surface of the rear fixed second lens are all spherical surface structures.

[0014] In the above scheme, only the concave surface of the front fixed first lens, the concave surface of the front fixed second lens, the concave surface of the variable first lens, the convex surface of the variable second lens and the convex surface of the compensation lens are even aspheric surface structures, and the rest are all standard spherical surfaces, which reduces the implementation difficulty.

[0015] The parameters of each lens are shown in the following table:

[0016] Surface No. Radius of curvature (mm) Thickness (mm) Aperture (mm) 101 422.144 5.855 63.638 102 1100.310 2.877 63.274 103 367.480 7.244 61.969 104 1294.229 T1 61.401 201 51.805 8.162 35.281 202 62.596 8.877 33.021 203 1809.389 8.016 31.846 204 50.800 T2 26.894 301 45.369 8.133 28.060 302 110.584 T3 27.373 401 41.701 8.106 24.527 402 32.375 T4 20.788 403 27.760 8.059 13.279 404 62.303 9.491 11.208

[0017] Wherein, surface serial numbers 101, 102, 103, 104, 201, 202, 203, 204, 301, 302, 401, 402, 403, 404 respectively refer to the convex surface of the front fixed first lens, the concave surface of the front fixed first lens, the convex surface of the front fixed second lens, the concave surface of the front fixed second lens, the convex surface of the variable first lens, the concave surface of the variable first lens, the convex surface of the variable second lens, the concave surface of the variable second lens, the convex surface of the compensation lens, the concave surface of the compensation lens, the convex surface of the rear fixed first lens, the concave surface of the rear fixed first lens, the convex surface of the rear fixed second lens, and the concave surface of the rear fixed second lens; T1, T2 are the distances of lens change in the zoom process, and T3, T4 are the distances of lens change in the compensation image surface defocusing process.

[0018] The even aspheric surface parameters are shown in the following table:

[0019] Surface No. Conic constant 4th order 6th order 8th order 10th order 102 -497.580 2.833E-9 1.306E-11 -3.294E-15 5.050E-19 104 324.832 4.499E-8 -3.542E-11 5.331E-15 -8.813E-19 202 -2.023 2.1123E-7 -4.283E-10 2.239E-13 2.007E-16 203 -3.255+016 -1.009E-6 2.607E-9 -1.412E-12 2.615E-16 301 0.275 -5.955E-7 -3.312E-9 1.516E-12 -1.140E-16

[0020] Wherein, surface serial numbers 102, 104, 202, 203, 301 respectively refer to the concave surface of the front fixed first lens, the concave surface of the front fixed second lens, the concave surface of the variable first lens, the convex surface of the variable second lens, and the convex surface of the compensation lens.

[0021] The glass material used by the front fixed first lens is germanium, the front fixed second lens and the variable first lens all use glass material AMTIR2, the variable second lens, the compensation lens, the rear fixed first lens and the rear fixed second lens use materials GAAS, GAAS, zinc sulfide and KRS5 respectively.

[0022] The selection of the lens material has excellent environmental adaptability, and the combination of the materials can achieve good results in experiments of athermalization design (thermalization design is to compensate for the deterioration of image quality caused by temperature) without aspheric surface and with binary surface.

[0023] The front fixed group lens, the zoom group lens, the compensation group lens, the diaphragm, the rear fixed group lens and the imaging surface are arranged in the interior of the lens barrel, the material of the lens barrel is aluminum alloy, and the thermal expansion coefficient TCEx1E-6 of the aluminum alloy is 23.6.

[0024] The thermal expansion and contraction of the lens barrel material and the thermal expansion and contraction and the change of the refractive index of the lens material can jointly cause the deterioration of the image quality, and the material and the thermal expansion coefficient of the lens barrel in the scheme are matched with the materials of the front lenses to jointly guarantee the imaging quality.

[0025] When the focal length f of the optical system is in the range of 30-240mm, the distance between the front fixed group lens and the zoom group lens is in the range of L1, 6.3 < L1 < 28.7mm, and the distance between the zoom group lens and the compensation group lens is in the range of L2, 1.7 < L2 < 58.2mm.

[0026] The total optical length TTL is less than or equal to 200mm, the working F number is 2, and the working wavelength is 8-12um.

[0027] Compared with the prior art, the utility model has the following beneficial effects:

[0028] 1. Aiming at the problems of few available materials and difficulty in athermalization of a long-wave infrared zoom optical system relative to a medium-wave infrared zoom optical system, a long-wave infrared zoom optical system athermalization zoom design is carried out.

[0029] 2. An 8x zoom ratio is realized, continuous and smooth zooming is realized in the range of 30-240mm focal length, only the zoom group lens is used for zooming design, and the compensation group lens (one lens) and the one lens of the rear fixed group lens are used to realize athermalization design in the range of -30-+60 DEG C environmental temperature.

[0030] 3. The zooming mode adopts mechanical compensation technology, the process method is mature, and the stability is good.

[0031] 4. The total optical length is small, the structure is compact, the volume and the weight are small, the problems of short action distance, large volume and environmental temperature affecting the image quality of the existing continuous zoom optical system are solved, good practicability is achieved, and the utility model is suitable for 640x512 12um domestic long-wave uncooled infrared detectors. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a structure diagram of the athermalization long-wave infrared continuous zoom optical system.

[0033] Figure 2 The utility model discloses a two-dimensional structure diagram of long wave infrared continuous zoom optical system focus 30mm of eliminating the difference of heat.

[0034] Figure 3 The utility model discloses a two-dimensional structure diagram of long wave infrared continuous zoom optical system focus 135mm of eliminating the difference of heat.

[0035] Figure 4 The utility model discloses a two-dimensional structure diagram of long wave infrared continuous zoom optical system focus 240mm of eliminating the difference of heat.

[0036] Figure 5 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 30mm, temperature 20 DEG C of eliminating the difference of heat.

[0037] Figure 6 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 135mm, temperature 20 DEG C of eliminating the difference of heat.

[0038] Figure 7 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 240mm, temperature 20 DEG C of eliminating the difference of heat.

[0039] Figure 8 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 30mm, temperature -30 DEG C of eliminating the difference of heat.

[0040] Figure 9 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 135mm, temperature -30 DEG C of eliminating the difference of heat.

[0041] Figure 10 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 240mm, temperature -30 DEG C of eliminating the difference of heat.

[0042] Figure 11 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 30mm, temperature 60 DEG C of eliminating the difference of heat.

[0043] Figure 12 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 135mm, temperature 60 DEG C of eliminating the difference of heat.

[0044] Figure 13 The utility model discloses a MTF diagram of long wave infrared continuous zoom optical system focus 240mm, temperature 60 DEG C of eliminating the difference of heat.

[0045] The diagram is labeled as follows: Front fixed lens 1, zoom lens 2, compensation lens 3, aperture 4, rear fixed lens 5, imaging plane 6, front fixed first object side 101, front fixed first image side 102, front fixed second object side 103, front fixed second image side 104, zoom first object side 201, zoom first image side 202, zoom second object side 203, zoom second image side 204, compensation object side 301, compensation image side 302, rear fixed first object side 401, rear fixed first image side 402, rear fixed second object side 403, and rear fixed second image side 404. Detailed Implementation

[0046] The present invention will be further illustrated below with reference to embodiments and accompanying drawings. The purpose of this illustration is only to provide a better understanding of the present invention and not to limit the scope of the present invention.

[0047] like Figure 1 As shown, the thermally ablated long-wave infrared continuous zoom optical system provided in this embodiment, from the object side to the image side (with... Figure 1 The arrangement shown is for reference only (from left to right). Along the optical axis, the following lenses are arranged sequentially: a front fixed lens group 1, a zoom lens group 2, a compensation lens group 3, an aperture stop 4, a rear fixed lens group 5, and an image plane 6. The image plane 6 is the imaging plane. The front fixed lens group 1 includes a front fixed first lens and a front fixed second lens, both of which are meniscus positive lenses curved towards the image side. The zoom lens group 2 includes a zoom first lens and a zoom second lens, both of which are meniscus negative lenses curved towards the image side. The compensation lens group 3 includes a compensation lens, which is also a meniscus positive lens curved towards the image side. The rear fixed lens group 5 includes a rear fixed first lens and a rear fixed second lens. The rear fixed first lens is a meniscus negative lens curved towards the image side, and the rear fixed second lens is a meniscus positive lens curved towards the image side.

[0048] The front fixed lens group is used to converge the infrared radiation of the scene; the zoom lens group is used to change the focal length of the system and compensate for focus; the compensation lens group and the rear fixed first lens can both move along the optical axis to compensate for image plane drift caused by the movement of the zoom lens group, as well as to compensate for thermal defocusing of the image plane at different operating temperatures, and the image formed by the front zoom objective lens is imaged onto the imaging plane.

[0049] Specifically, in this embodiment, the zoom first lens, the compensation lens, and the rear fixed first lens can all move along the optical axis. That is, the positions of the zoom first lens, the compensation lens, and the rear fixed first lens are not fixed, but can move along the optical axis to achieve focal length changes and adapt to temperature changes.

[0050] Figure 2 This is a two-dimensional structural diagram of the aforementioned thermally ablated long-wave infrared continuous zoom optical system with a focal length of 30mm. Figure 3This is a two-dimensional structural diagram with a focal length of 135mm. Figure 4 This is a two-dimensional structural diagram with a focal length of 240mm. (Example) Figures 2-4 As shown, when the zoom lens 2 (zoom first lens) moves closer to the front fixed lens 1 (front fixed second lens) along the optical axis, the system focal length shortens; when the zoom lens 2 (zoom first lens) moves away from the front fixed lens 1 (front fixed second lens) along the optical axis, the system focal length length length increases. The image plane does not move during temperature compensation and zooming, achieving continuous zoom. Thermal defocusing of the image plane is compensated by moving the compensation lens and one lens in the rear fixed lens group (rear fixed first lens) along the optical axis, enhancing the system's temperature adaptability; the temperature range is -30 to +60℃. When the focal length f of the optical system is in the range of 30-240mm, the distance between the front fixed lens 1 (front fixed second lens) and the zoom lens 2 (zoom first lens) is L1, where 6.3 < L1 ≤ 28.7mm, and the distance between the zoom lens 2 (zoom second lens) and the compensation lens 3 (compensation lens) is L2, where 1.7 < L2 ≤ 58.2mm.

[0051] The front fixed lens group collects light and provides maximum optical power. It also determines the system's physical aperture size and corrects initial optical distortion. This is achieved by two lenses: the first and second front fixed lenses. The zoom lens group handles the system's zoom function, also achieved by two lenses: the first and second zoom lenses. This allows for more accurate zooming and controls the light path. The compensation lens group adjusts the image plane position, compensating for image plane drift caused by the movement of the zoom lens group. This can be accomplished with a single lens, eliminating the need for additional lenses to correct complex aberrations; therefore, only one compensation lens is used to reduce the number of lenses. A separate lens from the rear fixed lens group (the first rear fixed lens) is used for temperature compensation and, together with the second rear fixed lens, corrects residual aberrations from the front group.

[0052] In this embodiment, the front fixed first lens is made of germanium glass, the front fixed second lens and the zoom first lens are both made of AMTIR2 glass, and the zoom second lens, the compensation lens, the rear fixed first lens and the rear fixed second lens are made of GAAS, GAAS, zinc sulfide and KRS5 respectively.

[0053] The front fixed lens group 1, the zoom lens group 2, the compensation lens group 3, the aperture 4, the rear fixed lens group 5, and the imaging plane 6 are all located inside the lens barrel. The lens barrel is made of aluminum alloy, and the coefficient of thermal expansion of this material is TCEx1E-6=23.6.

[0054] In the embodiment, the total optical length TTL is less than or equal to 200 mm, the working F number is 2, and the working wavelength is 8-12 um, which can be adapted to a 640*512 12 um domestic long-wave uncooled infrared detector. The F number in the optical system is described as the ratio of the focal length to the entrance pupil diameter, also known as the aperture number. The smaller the F number, the larger the aperture, the greater the light flux, and the brighter the image.

[0055] The lens has two sides, which are referred to as the object side and the image side in the embodiment for convenience of description, that is, the side adjacent to the object side is referred to as the object side, and the side adjacent to the image side is referred to as the image side. Therefore, as shown in FIG. 1, the front fixed first lens has a front fixed first object side 101 and a front fixed first image side 102, and the front fixed second lens has a front fixed second object side 103 and a front fixed second image side 104; the zoom first lens has a zoom first object side 201 and a zoom first image side 202, and the zoom second lens has a zoom second object side 203 and a zoom second image side 204; the compensation lens has a compensation object side 301 and a compensation image side 302; the rear fixed first lens has a rear fixed first object side 401 and a rear fixed first image side 402, and the rear fixed second lens has a rear fixed second object side 403 and a rear fixed second image side 404. Since each lens is a meniscus lens bent toward the image side, the object side is a convex structure, and the image side is a concave structure. Figure 1 In the embodiment, the front fixed first image side 102, the front fixed second image side 104, the zoom first image side 202, the zoom second object side 203, and the compensation object side 301 are designed as even aspheric surfaces, and the remaining sides of the remaining lenses are designed as standard spherical surfaces. That is, the concave surface 102 of the front fixed first lens, the concave surface 104 of the front fixed second lens, the concave surface 202 of the zoom first lens, the convex surface 203 of the zoom second lens, and the convex surface 301 of the compensation lens are all designed as even aspheric surfaces, and the convex surface 101 of the front fixed first lens, the convex surface 103 of the front fixed second lens, the convex surface 201 of the zoom first lens, the concave surface 204 of the zoom second lens, the concave surface 302 of the compensation lens, the convex surface 401 of the rear fixed first lens, the concave surface 402 of the rear fixed first lens, the convex surface 403 of the rear fixed second lens, and the concave surface 404 of the rear fixed second lens are all designed as spherical surfaces.

[0056] The even aspheric surface in the optical system lens satisfies the following expression:

[0057]

[0058]

[0059] ​Wherein, x represents the distance vector height from the vertex of the aspheric surface when the aspheric surface is in the height r position along the optical axis direction, c is the curvature, which is the inverse of the curvature radius R, that is, c = 1 / R, k represents the surface conic coefficient, A, B, C and D respectively represent the even aspheric surface parameters.

[0060] The power distribution satisfies the total power, that is:

[0061]

[0062] Wherein, is the power of the i-th lens (from the object side to the image side direction), hi is the incidence height of the paraxial ray on the i-th lens, is the total power; j is the number of lenses; i is the lens serial number.

[0063] The system chromatic aberration satisfies:

[0064]

[0065] Wherein is the system chromatic aberration, hi is the incidence height of the paraxial ray on the i-th lens, for example, h1 is the incidence height of the paraxial ray on the first lens, wi is the chromatic aberration coefficient of the i-th lens.

[0066] The specific parameters of each lens in the embodiment are shown in Table 1:

[0067] Table 1: Lens parameters

[0068] Surface No. Surface type Radius of curvature (mm) Thickness (mm) Aperture (mm) 101 Standard surface 422.144 5.855 63.638 102 Even aspherical surface 1100.310 2.877 63.274 103 Standard surface 367.480 7.244 61.969 104 Even aspherical surface 1294.229 T1 61.401 201 Standard surface 51.805 8.162 35.281 202 Even aspherical surface 62.596 8.877 33.021 203 Even aspherical surface 1809.389 8.016 31.846 204 Standard surface 50.800 T2 26.894 301 Even aspherical surface 45.369 8.133 28.060 302 Standard surface 110.584 T3 27.373 STO Standard surface Infinite 4.737 6.091 401 Standard surface 41.701 8.106 24.527 402 Standard surface 32.375 T4 20.788 403 Standard surface 27.760 8.059 13.279 404 Standard surface 62.303 9.491 11.208 IMG Standard surface Infinite - 4.904

[0069] T1, T2, T3, T4 in Table 1 represent the changing lens spacing during the continuous zooming process of the optical system moving the lens position, T1, T2 are the lens spacing changed during the zooming process, and T3, T4 are the lens spacing changed to compensate for the defocusing process of the image surface. It should be noted that the terms of lens glass thickness and air thickness in the description of the optical system are all thickness, and the air thickness is the lens distance.

[0070] It is easy to understand that the parameters shown in Table 1 are the preferred one of the embodiments, and other parameter settings can be used, and the curvature radius, thickness and aperture parameters also allow a certain fluctuation range, for example, the curvature radius can have a fluctuation range of ±0.05mm, and the thickness allows a fluctuation range of ±0.01mm.

[0071] The even aspheric surface parameters in the embodiment are shown in Table 2:

[0072] Table 2: Even aspheric surface parameters

[0073] Surface No. Conic constant 4th order 6th order 8th order 10th order 102 -497.580 2.833E-9 1.306E-11 -3.294E-15 5.050E-19 104 324.832 4.499E-8 -3.542E-11 5.331E-15 -8.813E-19 202 -2.023 2.1123E-7 -4.283E-10 2.239E-13 2.007E-16 203 -3.255+016 -1.009E-6 2.607E-9 -1.412E-12 2.615E-16 301 0.275 -5.955E-7 -3.312E-9 1.516E-12 -1.140E-16

[0074] Figures 5-13 The MTF diagram of three temperatures and three zoom ranges can be seen from the figure, and the short-focus, medium-focus and long-focus of the athermal long-wave infrared continuous zoom optical system have good imaging quality at normal temperature 20 DEG C, low temperature-30 DEG C and high temperature 60 DEG C; the MTF of the short-focus, medium-focus and long-focus at the Nyquist frequency 40 lp / mm is close to the limit diffraction, thereby indicating that the system can realize temperature adaptation of the full focus range in a wide temperature range and realize athermalization.

[0075] The design of the zoom infrared athermalization system is divided into three steps: ① by comparing and analyzing the design requirements, selecting an initial four-group structure, calculating the focal length and aperture of the four groups according to the zoom ratio ZR=8, the short-focus fa=30mm, the long-focus fc=240mm, the image height y'=9.8mm, the F#=2, finding the existing optical system parameters, and splicing into the initial structure; ② selecting mechanical positive compensation as the compensation mode of the system, distributing the optical power through the combination of infrared optical materials, controlling the barrel length, and minimizing the system size, and using optical design software to complete the optimization of the infrared zoom optical system; ③ performing thermal analysis on the optical system, setting the high-temperature and low-temperature states as thermal pickup, and finally realizing system athermalization through the movement of the temperature compensation element, and analyzing the thermal defocus amount and the modulation transfer function and other indicators to judge the athermalization effect in a wide temperature range.

[0076] In the description of the utility model, it is understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like is the orientation or positional relationship shown in the drawings, which is only for the convenience of describing the utility model and simplifying the description, and does not indicate or imply that the indicated device or element must have a particular orientation, a particular orientation structure and operation, and therefore cannot be understood as a limitation on the protection scope of the utility model.

[0077] The above-described embodiments are merely specific embodiments of the utility model, but the protection scope of the utility model is not limited thereto, and any person skilled in the art can easily think of various equivalent modifications, replacements and improvements within the technical range disclosed by the utility model, and these modifications, replacements and improvements should be covered within the protection scope of the utility model. Therefore, the protection scope of the utility model should be subject to the protection scope of the claims.

Claims

1. A thermally differential long-wave infrared continuous zoom optical system, characterized in that, It includes a front fixed lens group, a zoom lens group, a compensation lens group, an aperture, a rear fixed lens group, and an imaging plane arranged sequentially along the optical axis from the object side to the image side; The front fixed lens group is used to converge the infrared radiation of the scene; the zoom lens group can move along the optical axis, and the focal length and focus compensation can be changed by adjusting the distance between the zoom lens group and the front fixed lens group; one of the lenses in the compensation lens group and the rear fixed lens group can move along the optical axis to compensate for image plane drift caused by the movement of the zoom lens group, and to compensate for thermal defocusing of the image plane at different operating temperatures.

2. The thermally ablated long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The front fixed lens group includes a front fixed first lens and a front fixed second lens, both of which are meniscus positive lenses curved towards the image side; the zoom lens group includes a zoom first lens and a zoom second lens, both of which are meniscus negative lenses curved towards the image side; the compensation lens group includes a compensation lens, which is a meniscus positive lens curved towards the image side; the rear fixed lens group includes a rear fixed first lens and a rear fixed second lens, the rear fixed first lens being a meniscus negative lens curved towards the image side, and the rear fixed second lens being a meniscus positive lens curved towards the image side; the zoom first lens, the compensation lens, and the rear fixed first lens can all move along the optical axis.

3. The thermally ablated long-wave infrared continuous zoom optical system according to claim 2, characterized in that, The concave surfaces of the first fixed lens, the second fixed lens, the first zoom lens, the second zoom lens, and the compensating lens are all even-order aspherical structures, and the even-order aspherical structures satisfy the following conditions. x represents the distance vector from the vertex of the aspherical surface at a height r along the optical axis, c is the curvature, k represents the surface conic coefficient, and A, B, C, and D represent even-order aspherical parameters.

4. The thermally ablated long-wave infrared continuous zoom optical system according to claim 3, characterized in that, The convex surface of the front fixed first lens, the convex surface of the front fixed second lens, the convex surface of the zoom first lens, the concave surface of the zoom second lens, the concave surface of the compensation lens, the convex surface of the rear fixed first lens, the concave surface of the rear fixed first lens, the convex surface of the rear fixed second lens, and the concave surface of the rear fixed second lens are all spherical structures.

5. The thermally ablated long-wave infrared continuous zoom optical system according to claim 3, characterized in that, The parameters of each lens are shown in the table below: Among them, surface numbers 101, 102, 103, 104, 201, 202, 203, 204, 301, 302, 401, 402, 403, and 404 refer to the convex surface of the first fixed lens, the concave surface of the first fixed lens, the convex surface of the second fixed lens, the concave surface of the second fixed lens, the convex surface of the zoom first lens, the concave surface of the zoom first lens, the convex surface of the zoom second lens, the concave surface of the zoom second lens, the convex surface of the compensation lens, the concave surface of the compensation lens, the convex surface of the first fixed lens, the concave surface of the first fixed lens, the convex surface of the second fixed lens, and the concave surface of the second fixed lens, respectively; T1 and T2 are the distances between the lens changes during zooming, and T3 and T4 are the distances between the lens changes during image plane defocusing compensation.

6. The thermally ablated long-wave infrared continuous zoom optical system according to claim 3, characterized in that, The parameters of the even-order aspherical surfaces are shown in the table below: Among them, surface serial numbers 102, 104, 202, 203, and 301 refer to the concave surface of the front fixed first lens, the concave surface of the front fixed second lens, the concave surface of the zoom first lens, the convex surface of the zoom second lens, and the convex surface of the compensation lens, respectively.

7. The thermally ablated long-wave infrared continuous zoom optical system according to claim 2, characterized in that, The front fixed first lens uses germanium glass, the front fixed second lens and the zoom first lens both use AMTIR2 glass, and the zoom second lens, the compensation lens, the rear fixed first lens and the rear fixed second lens use GAAS, GAAS, zinc sulfide and KRS5 respectively.

8. The thermally ablated long-wave infrared continuous zoom optical system according to claim 7, characterized in that, The front fixed lens group, the zoom lens group, the compensation lens group, the aperture stop, the rear fixed lens group, and the imaging plane are all located inside the lens barrel. The lens barrel is made of aluminum alloy, and the coefficient of thermal expansion of the aluminum alloy is TCEx1E-6 = 23.

6.

9. The thermally ablated long-wave infrared continuous zoom optical system according to claim 1, characterized in that, When the focal length f of the optical system is in the range of 30-240mm, the distance between the front fixed lens group and the zoom lens group is L1, 6.3<L1≤28.7mm, and the distance between the zoom lens group and the compensation lens group is L2, 1.7<L2≤58.2mm.

10. The thermally ablated long-wave infrared continuous zoom optical system according to claim 1, characterized in that, The total optical length (TTL) is ≤200mm, the operating F-number is 2, and the operating wavelength is 8~12um.

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