A large-target-area, high-resolution infrared zoom optical system

Abstract

This invention relates to a large-target-area, high-resolution infrared zoom optical system, comprising, sequentially from the object plane to the image plane along the optical axis, a front fixed lens group, a zoom lens group, a compensation lens group, and a rear fixed lens group. The system is simple in design, employing only seven infrared lenses to achieve a large target area of ​​at least 1280×1024×15μm, suitable for cooled infrared detectors. The front fixed lens group uses only one large-aperture lens, facilitating lens weight reduction. The system's temperature compensation mechanism is simple and efficient, utilizing existing zoom compensation motion lenses to achieve image quality compensation over a wide temperature range. It features a large target area, high spatial resolution, lightweight system, fewer lenses, high transmittance, 100% cold stop matching, strong resistance to cold reflection, and good image uniformity. It can improve dynamic range, capture more scene information, and enhance imaging quality, making it particularly suitable for applications requiring high-precision measurement, high-resolution monitoring, or long-distance detection.

Description

Technical Field

[0001] This invention belongs to the field of infrared thermal imaging and relates to a large target area high-resolution infrared zoom optical system. Background Technology

[0002] In the field of infrared imaging, with the continuous expansion of application scenarios, the performance requirements for infrared optical systems are also increasing. However, traditional infrared optical systems often suffer from problems such as small target size, low resolution, high system complexity, significant influence of temperature differences on image quality, and low transmittance, making it difficult to meet current demands for large target size, high resolution, stable zoom over a wide temperature range, high energy conversion efficiency, and lightweight systems. Large-target infrared detectors can receive more infrared radiation energy, improving the signal-to-noise ratio and resolution of the imaging system. Therefore, such detectors have significant application value in fields such as long-distance imaging and high-precision measurement.

[0003] On the other hand, cooled infrared systems occupy an important position in the field of infrared imaging due to their multiple advantages, such as high sensitivity, high performance, and wide temperature range adaptability. However, the design of infrared zoom optical systems that are matched with cooled detectors is subject to many limitations and difficulties, such as the limited types of infrared optical materials and the requirement that the exit pupil of the optical system be located at the cold stop of the detector when used with cooled infrared detectors.

[0004] For the reasons mentioned above, developing a cooled, large-target, high-resolution infrared zoom optical system has become an urgent problem to be solved in the field of infrared technology.

[0005] Existing cooled infrared zoom optical systems are generally compatible with target sizes of no more than 320×256×30μm or 640×512×15μm. The 320×256×30μm target size is more common in civilian applications, only meeting basic night vision and thermal imaging needs. With technological advancements, the 640×512×15μm target size is increasingly being used in high-end markets and specific applications. However, compared to visible light systems, the smaller target size and lower resolution of infrared imaging systems severely limit their applications.

[0006] First, large-area infrared zoom optical systems are prone to various aberrations, such as spherical aberration, coma, astigmatism, and distortion. These aberrations severely affect image quality and require precise correction. Second, infrared optical systems are highly sensitive to temperature changes, which alter the refractive index of infrared optical materials, thus affecting image quality. This effect is even more pronounced in large-area infrared zoom optical systems. Third, as the target size increases, the complexity of the infrared optical system, especially the zoom optical system, also increases significantly, requiring more lenses to balance the aberrations of the large target area. These issues greatly increase the design difficulty of large-area infrared zoom optical systems.

[0007] Currently, there are no publicly available documents in China that record an infrared zoom optical system with a large target surface size of 1280×1024×15μm.

[0008] Chinese invention patent CN113448067B discloses a thermally differential long-wave infrared zoom lens with switchable zoom. The system is adapted to a target surface of 640×512×15μm and uses 8 lenses. It is a switchable zoom system.

[0009] Chinese utility model patent with announcement number CN216310402U discloses a compact infrared zoom lens with a large zoom ratio. The optical system uses eight lenses, and two large-diameter lenses are used in the front fixed group. The large number of large-diameter lenses increases the weight of the lenses and increases the cost. In addition, the target size of 640×512×15μm can be calculated from the relationship between focal length and field of view parameters.

[0010] Chinese invention patent CN108020911B discloses a 30x mid-wave infrared zoom optical system with an ultra-long focal length. According to the parameters in the paper, it can be calculated that it is suitable for a target surface size of about 640×512×10μm and is uncooled, so it does not require cold stop matching. Furthermore, the optical system uses 10 lens sheets and includes 4 diffraction surfaces, resulting in high system complexity.

[0011] As can be seen from the existing technologies described above, the design and manufacture of current infrared zoom optical systems face numerous challenges, such as small target size, low resolution, high system complexity, numerous lenses, heavy lens weight, low transmittance, and image quality being affected by ambient temperature. Solving these problems and developing a large-target-size, high-resolution infrared zoom optical system adapted to cooled detectors has extremely high value and application potential. Summary of the Invention

[0012] The purpose of this invention is to provide a large-target-area, high-resolution infrared zoom optical system that solves the problems of existing infrared zoom optical systems, such as small target size, low resolution, high system complexity, large number of lenses, heavy lens weight, low transmittance, and image quality being affected by ambient temperature.

[0013] To achieve the above objectives, the technical solution of the present invention is as follows:

[0014] A large target surface high-resolution infrared zoom optical system, wherein a front fixed lens group, a zoom lens group, a compensation lens group, a rear fixed lens group and a cooled infrared detector are sequentially arranged along the optical axis from the object side to the image side on the incident light path.

[0015] The front fixed lens group is a meniscus silicon lens with positive optical power that bends towards the image side; the zoom lens group is a plano-concave or meniscus germanium lens with negative optical power that bends towards the image side; and the compensation lens group is a meniscus silicon lens with positive optical power that bends towards the object side.

[0016] The aperture stop coincides with the cold aperture stop of the cooled infrared detector in terms of position and size.

[0017] The zoom lens group and the compensation lens group can be set up relatively independently along the optical axis between the front fixed lens group and the rear fixed lens group.

[0018] The focal length F1 of the front fixed lens group and the focal length F at the telephoto end L Satisfying the condition:

[0019] 0.15 <F1 / F L <0.5.

[0020] The zoom lens group and the compensation lens group do not have diffraction surfaces; the rear fixed lens group has aspherical and diffraction surfaces.

[0021] The rear fixed lens group includes the front group of the rear fixed lens and the relay imaging lens group.

[0022] Both the front group of the rear fixed lens and the relay imaging lens group are positive optical power.

[0023] The front group of the rear fixed lens is a meniscus germanium lens with positive optical power, curved towards the image side.

[0024] The relay imaging lens group consists of a fifth lens, a sixth lens, and a seventh lens. The fifth lens is a positive optical power biconvex silicon lens, the sixth lens is a negative optical power biconcave germanium lens, and the seventh lens is a positive optical power meniscus silicon lens that curves towards the object side.

[0025] The optical power of the front group of the rear fixed lens is The optical power of the relay lens group is

[0026] The optical power of the zoom lens group is The optical power of the compensating lens group is

[0027] The advantages of this invention are: 1. The system is simple in design, using only seven infrared lenses, which can achieve continuous zoom while adapting to a large target surface size of not less than 1280×1024×15μm and is compatible with cooled infrared detectors; 2. The fixed lens group at the front of the system uses only one large-aperture lens, which is beneficial for reducing lens weight; 3. The temperature compensation method is simple and efficient, without adding unnecessary moving parts, and only using existing zoom compensation moving lenses to achieve image quality compensation over a wide temperature range; 4. The entire system has advantages such as large target surface size, high spatial resolution, lightweight system, few lenses, high transmittance, 100% cold aperture matching, strong anti-cold reflection capability, and good image uniformity. It can improve dynamic range, capture more scene information, and improve imaging quality, and is particularly suitable for application scenarios that require high-precision measurement, high-resolution monitoring, or long-distance detection. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the optical path at the telephoto end of the present invention.

[0029] Figure 2 This is a schematic diagram of the optical path at the mid-focal end of the present invention.

[0030] Figure 3 This is a schematic diagram of the optical path at the short focal length end of the present invention.

[0031] Figure 4 This is the MTF curve of the present invention at the telephoto end @33lp / mm (room temperature 20℃).

[0032] Figure 5 This is the MTF curve of the present invention at the middle coke end @33lp / mm (room temperature 20℃).

[0033] Figure 6 This is the MTF curve of the present invention at the short focal length end @33lp / mm (room temperature 20℃).

[0034] Figure 7 This is the MTF curve of the present invention at the telephoto end @33lp / mm (high temperature 60℃).

[0035] Figure 8 This is the MTF curve of the present invention at the telephoto end @33lp / mm (low temperature -40℃).

[0036] Figure 9 This is the MTF curve of the present invention at the short focal length end @33lp / mm (high temperature 60°C).

[0037] Figure 10This is the MTF curve of the present invention at the short focal length end @33lp / mm (low temperature -40℃).

[0038] In the diagram: 100—Front fixed lens group; 200—Zoom lens group; 300—Compensation lens group; 400—Rear fixed lens group; 410—Front group of rear fixed lens; 420—Relay imaging lens group; 421—Fifth lens; 422—Sixth lens; 423—Seventh lens; 500—Cooled infrared detector; 600—Image plane. Detailed Implementation

[0039] To simplify the description of this embodiment, some components that are well-known to those skilled in the art but are not related to the main content of this invention may be omitted in the accompanying drawings or description. Additionally, for ease of description, some components in the drawings may be omitted, enlarged, or reduced, but these do not represent the actual product dimensions or the complete structure.

[0040] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0041] The present invention will be further described below with reference to the accompanying drawings. The drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent.

[0042] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0043] This invention relates to a large-target-area, high-resolution infrared zoom optical system, such as... Figure 1-3 As shown, the incident light rays are arranged sequentially along the optical axis from the object side to the image side as follows: a front fixed lens group 100, a zoom lens group 200, a compensation lens group 300, a rear fixed lens group 400, a cooled infrared detector 500, and an image plane 600. The rear fixed lens group 400 includes a front rear fixed lens group 410 and a relay imaging lens group 420.

[0044] This invention uses the cold aperture of a cooled infrared detector 500 as its aperture stop, with the aperture stop and the cold aperture of the cooled infrared detector 500 coinciding in position and size, forming an image on the image plane 600. The front group 410 of the rear fixed lens converges the light onto the primary image plane, and the relay imaging lens group 420 is used to re-image the image from the primary image plane onto the focal plane of the infrared detector 500, simultaneously achieving 100% cold aperture matching and improving the system's response sensitivity.

[0045] The focal length variation range of the following embodiments is from 68 mm to 275 mm, the working wavelength band is 3.7 - 4.8 μm; the F number of the infrared system is 4; it is equipped with a cooled infrared detector 500, with an array of 1280×1024 and a pixel size of 15 μm. The present invention adopts a refractive-diffractive hybrid transmissive secondary imaging structure type, with a 100% cold stop efficiency. During the entire zooming process, the overall optical length remains constant, meeting the parfocal condition. Figure 1 , Figure 2 , Figure 3 They are respectively schematic diagrams at the long focal length of 275 mm, the medium focal length of 137 mm, and the short focal length of 68 mm.

[0046] The front fixed lens group 100 is a meniscus lens with a positive optical power that bends towards the image side and is arranged along the optical axis. The front surface of this lens is a spherical surface, and the radius of curvature satisfies 60 mm < R1 < 70 mm; the rear surface profile is an even aspheric surface, and the radius of curvature satisfies 115 mm < R2 < 125 mm; the central thickness is 10.78 mm, and the material is silicon. Using this type of meniscus lens with positive optical power helps to correct off-axis aberrations while reducing the aperture of the rear lens group, obtaining a larger field of view and target surface size.

[0047] The front fixed lens group 100 consists of only one meniscus silicon lens with a positive optical power that bends towards the image side, which can compress the beam aperture, reduce the size of the subsequent lenses, reduce the lens weight, and can correct the system aberrations to a certain extent, improving the image quality within the entire zoom focal length range; and the front fixed lens group adopts a single-lens structure type, minimizing the number of large-aperture lenses, which helps to make the system lighter, smaller, and reduce weight; the focal length F1 of the front fixed lens group 100 and the focal length F of the long focal end of the system [[ID=?]] L satisfy the conditional formula: 0.15 < F1 / F [[ID=?]] L < 0.5.

[0048] The zoom lens group 200 is a plano-concave or meniscus lens with a negative optical power that bends towards the image side and is arranged along the optical axis, used to change the focal length. The optical power of the zoom lens group 200 is The front surface of this lens is an even aspheric surface, with a radius of curvature R3 > 3E5 mm; the rear surface profile is a spherical surface, and the radius of curvature satisfies 40 mm < R4 < 50 mm; the central thickness is 4.49 mm, and the material is germanium.

[0049] The compensation lens group 300 can move back and forth along the optical axis. Within the temperature range from -40 °C to +60 °C, it can achieve temperature compensation for the image quality and obtain a stable and clear image. This temperature compensation method can obtain image quality compensation within a wide temperature range of high and low temperatures without adding extra moving parts, only by using the existing zoom compensation moving lenses, and the compensation type is simple and efficient.

[0050] Furthermore, by constraining and controlling the product of the projection height Y, the incident angle I, and the refractive index N of the paraxial marginal rays on the lens surface, such that the product of Y·N·I is greater than or close to 1, the change value of the temperature drop at the axial point caused by cold reflection is minimized, obtaining good anti-cold reflection ability, ensuring good uniformity of image gray scale, and better meeting the requirements of application scenarios such as high-precision measurement.

[0051] The compensation lens group 300 is a meniscus lens with a positive optical power that is bent towards the object side and arranged along the optical axis direction, used to compensate for the offset of the image plane position during the zooming process. The optical power of the compensation lens group 300 is The front surface of this lens is a spherical surface, with the curvature radius -1400mm < R5 < -1250mm; the rear surface profile is a spherical surface, and the curvature radius satisfies -150mm < R6 < -100mm; the central thickness is 5.04mm, and the material is silicon.

[0052] The variable magnification lens group 200 and the compensation lens group 300 are arranged between the front fixed lens group 100 and the rear fixed lens group 400. The variable magnification lens group 200 and the compensation lens group 300 move along the optical axis to obtain changes in the system focal length and field of view, realizing zoom imaging; when the focal length of the infrared zoom optical system changes from the long focal length to the short focal length, the first variable magnification lens group 200 moves along the optical axis towards the object side to continuously change the optical system focal length, and the compensation lens group 300 moves along the optical axis towards the image side to compensate for the change in the image plane position during the zooming process.

[0053] Furthermore, in the variable magnification lens group 200 of the present invention, germanium materials with high dispersion and high refractive index are used to better correct off-axis aberrations within the entire zoom range; in the compensation lens group 3 and 0, silicon materials with low dispersion and high refractive index are used to effectively eliminate chromatic aberration and compensate for the aberrations generated during the zooming process of this system, correcting the primary aberrations brought by the variable magnification lens group 200, and while realizing continuous zooming, keeping the final image plane position unchanged.

[0054] Preferably, in order to reduce the sensitivity of the zoom optical system to processing and alignment, there is no diffractive surface in the variable magnification lens group 200 and the compensation lens group 300, and the diffractive surface of the system is located in the rear fixed lens group 400. Adding a diffractive surface in the rear fixed lens group 400 can effectively eliminate chromatic aberration, offset the residual aberrations of the previous lens group, and also partially compensate for the influence of temperature changes on image quality.

[0055] Due to the higher requirements for optical image quality for a large target surface size, lower residual aberrations are needed to ensure high-quality images can be obtained both at the center and edge regions of the target surface, matching a larger target surface size. Therefore, in the present invention, by applying aspherical and diffractive surfaces in the rear fixed lens group 400 and adopting a silicon-germanium-silicon three-lens combination design, chromatic aberration and various aberrations are further eliminated, the imaging quality is improved, and thus a larger target surface size is obtained; the present invention can be adapted to a large target surface size of not less than 1280×1024×15μm.

[0056] The front group 410 of the rear fixed lens in the rear fixed lens group 400 is a meniscus lens with a positive optical power that is bent towards the image side and arranged along the optical axis direction. The front surface of this lens is a spherical surface with a curvature radius of 20mm < R7 < 40mm; the rear surface profile is an even aspherical surface containing a binary diffractive surface, and the curvature radius satisfies 20mm < R8 < 30mm; the central thickness is 5.00mm, and the material is germanium.

[0057] Further, in order to obtain a larger target surface size and enhance the system advantages, the optical power of the front group 410 of the rear fixed lens is 0.005 < φ < 0.010, which is used to converge the object-side scene into the primary image plane of the imaging system and compress the total length of the optical system.

[0058] The relay imaging lens group 420 in the rear fixed lens group 400 is composed of a fifth lens 421, a sixth lens 422, and a seventh lens 423.

[0059] The fifth lens 421 is a biconvex lens with a positive optical power that is arranged along the optical axis direction. The front surface of this lens is an even aspherical surface with a curvature radius of 50mm < R9 < 65mm; the rear surface profile is a spherical surface, and the curvature radius satisfies -90mm < R 10 < -75mm; the central thickness is 12.00mm, and the material is silicon.

[0060] The sixth lens 422 is a biconcave lens with a negative optical power that is arranged along the optical axis direction. The front surface of this lens is an even aspherical surface with a curvature radius of -90mm < R 11 < -70mm; the rear surface profile is a spherical surface, and the curvature radius satisfies 30mm < R 12 < 50mm; the central thickness is 9.62mm, and the material is germanium.

[0061] The seventh lens 423 is a meniscus lens with a positive optical power that is bent towards the object side and arranged along the optical axis direction. The front surface of this lens is an even aspherical surface with a curvature radius of 250mm < R 13 < 270mm; the rear surface profile is a spherical surface, and the curvature radius satisfies -35mm < R 14 < -20mm; the central thickness is 6.11mm, and the material is silicon.

[0062] The optical power of the relay imaging lens group 420 is By employing aberration complementation in the relay imaging lens group 420, and using a semi-close combination of three lenses—a silicon lens with positive optical power, a germanium lens with negative optical power, and a silicon lens with positive optical power—wideband incident light is focused at the same focal point, balancing the optical path difference between different wavelengths and materials in the system. The relay imaging lens group 420 is used to eliminate residual aberrations of the preceding lens group and to re-image the scene from the primary image plane onto the large target area focal plane image plane, while simultaneously controlling 100% cold stop matching.

[0063] At the telephoto 275mm position, the vertex of the zoom lens group 200 near the object side is approximately 25.09mm from the vertex of the front fixed lens group 100 near the image side; the vertex of the zoom lens group 200 near the image side is approximately 17.16mm from the vertex of the compensation lens group 300 near the object side; and the vertex of the compensation lens group 300 near the image side is approximately 73.86mm from the vertex of the rear fixed lens group 400 near the object side.

[0064] At the 137mm mid-focal position, the vertex of the zoom lens group 200 near the object side is approximately 23.17mm from the vertex of the front fixed lens group 100 near the image side; the vertex of the zoom lens group 200 near the image side is approximately 47.59mm from the vertex of the compensation lens group 300 near the object side; and the vertex of the compensation lens group 300 near the image side is approximately 45.36mm from the vertex of the rear fixed lens group 400 near the object side.

[0065] At the short focal length of 68 mm, the vertex of the zoom lens group 200 near the object side is approximately 20.88 mm from the vertex of the front fixed lens group 100 near the image side; the vertex of the zoom lens group 200 near the image side is approximately 80.36 mm from the vertex of the compensation lens group 300 near the object side; and the vertex of the compensation lens group 300 near the image side is approximately 14.88 mm from the vertex of the rear fixed lens group 400 near the object side.

[0066] The vertex of the front group 410 of the rear fixed lens, near the image side, is approximately 74.54 mm from the vertex of the lens 421 of the relay imaging lens group 420, near the object side; the vertex of the lens 421 of the relay imaging lens group 420, near the image side, is approximately 2.98 mm from the vertex of the lens 422 of the relay imaging lens group 420, near the object side; and the vertex of the lens 422, near the image side, is approximately 3.11 mm from the vertex of the lens 423 of the relay imaging lens group 420, near the object side.

[0067] To correct chromatic aberration and large field-of-view aberration, this invention employs aspherical surfaces or aspherical surfaces combined with diffraction surfaces on some lens surfaces to improve image quality and reduce the number of lenses and lens size.

[0068] To reduce the sensitivity of the zoom optical system to processing and calibration, no diffraction surface is added to the zoom lens group 200 and the compensation lens group 300; instead, the system diffraction surface is located in the rear fixed lens group 400. Adding a diffraction surface to the rear fixed lens group 400 can effectively eliminate chromatic aberration, counteract residual aberrations of the preceding lens groups, and partially compensate for the effects of temperature changes on image quality.

[0069] Furthermore, in order to improve energy utilization efficiency, the present invention coats the front and rear surfaces of all lenses with a high-quality anti-reflection coating to improve system response sensitivity and detection range.

[0070] Based on the parameters mentioned above, Table 1 provides the data for the aspherical and diffractive surfaces used in the system.

[0071] Table 1. Data on aspherical and diffractive surfaces used in the system.

[0072]

[0073] from Figure 4 , Figure 5 , Figure 6 As can be seen, the MTF curve values ​​at a spatial frequency of 33 lp / mm show that the system has good image quality in telephoto, medium telephoto, and short telephoto conditions, proving that the image quality of the system meets the usage requirements throughout the entire focal length range.

[0074] from Figure 7 , Figure 8 , Figure 9 , Figure 10 It can be seen that the system has good imaging quality, with MTF close to the diffraction limit at a spatial frequency of 33 lp / mm, across a wide temperature range from -40℃ to 60℃. This proves that the image quality of the system meets the usage requirements over a wide temperature range.

[0075] Technical features not described in this invention can be implemented using existing technologies and will not be elaborated upon here. The above description is merely a preferred embodiment of this invention and is not intended to limit the invention. This invention is not limited to the above examples. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of this invention, such as replacing the lens material or increasing or decreasing the number of lenses in the same lens group, should also fall within the protection scope of this invention.

Claims

1. A large-target-area, high-resolution infrared zoom optical system, characterized in that: The F number of the system is 4, the focal length variation range is from 68 mm to 275 mm, and the working wavelength band is 3.7 - 4.8 μm; it is equipped with a cooled infrared detector (500), with an array of 1280×1024 and a pixel size of 15 μm; On the incident light path, along the optical axis direction from the object side to the image side, a front fixed lens group (100), a zoom lens group (200), a compensating lens group (300), a rear fixed lens group (400) and a cooled infrared detector (500) are sequentially arranged; The front fixed lens group (100) is a meniscus-shaped silicon lens with a positive optical power that is curved towards the image side. The front surface of the lens is spherical, and the radius of curvature satisfies 60 mm < R1 < 70 mm; the rear surface profile is an even aspheric surface, and the radius of curvature satisfies 115 mm < R2 < 125 mm; the central thickness is 10.78 mm; the focal length F1 of the front fixed lens group (100) and the focal length F at the long focal end L satisfy the conditional equation: 0.15 < F1 / F L < 0.5; The zoom lens group (200) is a plano-concave or meniscus-shaped germanium lens with a negative optical power bending towards the image side, and the optical power of the zoom lens group (200) is -0.07 < φ < -0.05; the front surface of the lens is an even aspheric surface with a radius of curvature R3 > 3E5 mm; the rear surface is a spherical surface with a radius of curvature satisfying 40 mm < R4 < 50 mm; the central thickness is 4.49 mm; The compensating lens group (300) is a meniscus-shaped silicon lens with a positive optical power bending towards the object side, and the optical power of the compensating lens group (300) is 0.01 < φ < 0.03; the front surface of the lens is a spherical surface with a radius of curvature -1400 mm < R5 < -1250 mm; the rear surface is a spherical surface with a radius of curvature satisfying -150 mm < R6 < -100 mm; the central thickness is 5.04 mm; The rear fixed lens group (400) includes a front rear fixed lens group (410) and a relay imaging lens group (420); both the front rear fixed lens group (410) and the relay imaging lens group (420) have positive optical powers, the optical power of the front rear fixed lens group (410) is 0.005 < φ < 0.010, and the optical power of the relay imaging lens group (420) is 0.03 < φ < 0.08; The relay imaging lens group (420) is composed of a fifth lens (421), a sixth lens (422) and a seventh lens (423). Among them, the fifth lens (421) is a biconvex silicon lens with a positive optical power, the sixth lens (422) is a biconcave germanium lens with a negative optical power, and the seventh lens (423) is a meniscus-shaped silicon lens with a positive optical power bending towards the object side; The aperture stop coincides with the position and size of the cold stop of the cooled infrared detector (500).

2. The large target area high-resolution infrared zoom optical system according to claim 1, characterized in that: The zoom lens group (200) and the compensating lens group (300) can be arranged between the front fixed lens group (100) and the rear fixed lens group (400) to move relatively independently back and forth along the optical axis.

3. The large target area high-resolution infrared zoom optical system according to claim 1, characterized in that: The zoom lens group (200) and the compensating lens group (300) do not have diffractive surfaces; the rear fixed lens group (400) has aspheric surfaces and diffractive surfaces.

4. The large target area high-resolution infrared zoom optical system according to claim 3, characterized in that: The front rear fixed lens group (410) is a meniscus-shaped germanium lens with a positive optical power bending towards the image side.

Images