Compact high-resolution medium-wave zoom imaging system

Abstract

The invention relates to a compact high-resolution medium-wave zoom imaging system. The system is composed of eight lenses, a detector window, detector protection glass, a cold diaphragm and an image plane, wherein the eight lenses are coaxially and sequentially arranged in the forward direction of an optical axis and are coaxially and sequentially arranged in the light propagation direction; wherein the lens L01 forms a front fixed group, the lens L02 forms a zoom group, the lens L03 forms a compensation group, and the lens L04 forms a focusing group; the lens L05, the lens L06, the lens L07 and the lens L08 form a rear fixed group; the focal length change is realized through the axial movement of the zooming group and the compensation group, and the defocus caused by the temperature change is compensated through the axial movement of the focusing group. According to the invention, under the condition of ensuring high-resolution imaging, continuous zooming from 48mm to 205mm in focal length is realized, the zoom ratio is 4.3 times, the application range of the zoom imaging system is greatly expanded, and the resolution capability of the system is greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging system technology and relates to a compact, high-resolution mid-wave zoom imaging system. Background Technology

[0002] Existing optical structures for mid-wave visible light cooled zoom lenses, such as Figure 1 As shown, it includes eight lenses: a first meniscus positive lens, a biconcave negative lens, a second meniscus positive lens, a third meniscus positive lens, a fourth meniscus positive lens, a first meniscus negative lens, a fifth meniscus positive lens, and a sixth meniscus positive lens. The materials of the eight lenses are monocrystalline silicon (SILICON), monocrystalline germanium (GERMMW), monocrystalline silicon (SILICON), zinc selenide (ZNSE), zinc selenide (ZNSE), monocrystalline germanium (GERMMW), monocrystalline silicon (SILICON), and monocrystalline germanium (GERMMW). The system consists of a first meniscus positive lens as the front fixed lens; a biconcave negative lens as the first zoom lens; a second meniscus positive lens as the second zoom lens; and the system's focal length is changed by the movement of the biconcave negative lens and the second meniscus positive lens along the optical axis. A third meniscus positive lens is a compensation lens, which compensates for image plane defocusing caused by the movement of the zoom lens by moving along the optical axis. A fourth meniscus positive lens, a first meniscus negative lens, a fifth meniscus positive lens, and a sixth meniscus positive lens form the rear fixed group. A primary image plane is positioned between the first meniscus negative lens and the fifth meniscus positive lens, and a field stop is located at the primary image plane. This structure employs a three-element continuous zoom and secondary imaging system design. The light-incident surfaces of the third meniscus positive lens, the first meniscus negative lens, and the fifth meniscus positive lens are all even-order aspherical surfaces. The light-outceasing surface of the sixth meniscus positive lens is a diffractive aspherical surface, with the aspherical surface and the diffractive surface acting on the same lens surface. The structure has the following problems: 1. The F number is relatively large, generally not less than 4; 2. The structure is complex, with more than or equal to 3 zoom and compensation telephoto elements; 3. The back intercept size is too small, which is not convenient for later assembly and debugging; 4. The environmental temperature adaptability is generally poor, and it cannot work normally in harsh environmental temperatures such as -40℃ to +65℃; 5. It contains 1 to 2 diffraction surfaces, which reduces the transmittance of the overall optical system. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a compact high-resolution mid-wave zoom imaging system with a small F-number, which can improve lens stability and reliability, reduce stability and reliability, and improve the overall transmittance of the system.

[0004] To solve the above-mentioned technical problems, the compact high-resolution mid-wave zoom imaging system of the present invention comprises lenses L01, L02, L03, L04, L05, L06, L07, and L08 arranged coaxially along the positive direction of the optical axis and coaxially arranged coaxially along the direction of light propagation, a detector window WIN, a detector protective glass FIL, a stop stop, and an image plane IMAGE; wherein lens L01 constitutes the front fixed group, lens L02 constitutes the zoom group, lens L03 constitutes the compensation group, and lens L04 constitutes the focusing group; lenses L05, L06, L07, and L08 constitute the rear fixed group; the focal length is changed by axial movement of the zoom group and the compensation group, and the defocusing caused by temperature changes is compensated by axial movement of the focusing group; the focal length f1 of the front fixed group, the focal length f2 of the zoom group, the focal length f3 of the compensation group, the focal length f4 of the focusing group, and the focal length f5 of the rear fixed group are fully satisfied. The following relationships are satisfied: 0.420≤f1 / f≤0.454; -0.08≤f2 / f≤-0.073; 0.106≤f3 / f≤0.108; -0.376≤f4 / f≤-0.32; 0.141≤f5 / f≤0.157, where f is the focal length of the imaging system at its telephoto end; lens L01 is a meniscus lens with its convex surface facing the object side, lens L02 is a biconcave lens, lens L03 is a biconvex lens, and lens L04... Lens L05 is a meniscus negative lens with its convex surface facing the image side; lens L06 is a biconvex positive lens; lens L07 is a negative lens; and lens L08 is a positive lens. Lens L01 is a spherical lens. The front surfaces of lenses L04, L07, and L08 are aspherical, while their rear surfaces are spherical. The front surfaces of lenses L03, L05, and L06 are spherical, while their rear surfaces are aspherical. The front and rear surfaces of lens L02 are both aspherical.

[0005] The radii of curvature of the front and rear surfaces of the lens L01 are 85.38 mm to 92.02 mm and 126.83 mm to 137.69 mm, respectively. The radii of curvature of the front and rear surfaces of lens L02 are -112.44 mm to -111.14 mm and 78.28 mm to 85.41 mm, respectively. The radii of curvature of the front and rear surfaces of lens L03 are 102.35mm~105.62mm and -106.25mm~-99.76mm, respectively. The radii of curvature of the front and rear surfaces of lens L05 are -33.69mm to -25.31mm and -44.88mm to -38.94mm, respectively. The radii of curvature of the front and rear surfaces of lens L06 are 99.77mm~219.52mm and -122.85mm~-77.44mm, respectively.

[0006] The thicknesses of lenses L01, L02, L03, L04, L05, L06, L07, and L08 are 14.63mm~15mm, 2.98mm~2.99mm, 6.97mm~7.14mm, 2.99mm~3mm, 4.4mm~7mm, 13.6mm~15.01mm, 4.99mm~5.00mm, and 10.2mm~10.6mm, respectively.

[0007] The air gap between lens L01 and lens L02 is 34.27mm to 51.03mm, the air gap between lens L02 and lens L03 is 4.96mm to 34.44mm, the air gap between lens L03 and L04 is 9.07mm to 31.12mm, the air gap between lens L04 and lens L05 is 64.92mm to 70.07mm, the air gap between lens L05 and lens L06 is 4.38mm to 14.3mm, the air gap between lens L06 and lens L07 is 1.18mm to 4.38mm, and the air gap between lens L07 and lens L08 is 4.43mm to 8.33mm.

[0008] The lens L04 is a meniscus negative lens with its concave surface facing the object side or a biconcave lens.

[0009] The lens L07 is a meniscus negative lens or a biconcave lens with its concave surface facing the object side.

[0010] The lens L08 is a meniscus positive lens or a biconvex lens with its convex surface facing the object side.

[0011] When the lens L04 is a meniscus negative lens, the radii of curvature of its front and rear surfaces are -44.05mm to -31.99mm and -95.35mm to -55.58mm, respectively; when it is a biconcave lens, the radii of curvature of its front and rear surfaces are -142.58mm to -138.91mm and 300.00mm to 300.09mm, respectively.

[0012] When the lens L07 is a meniscus negative lens, the radii of curvature of its front and rear surfaces are -73.44mm to -69.45mm and -500.00mm, respectively; when it is a biconcave lens, the radii of curvature of its front and rear surfaces are -163.04mm to -154.99mm and 161.99mm to 169.25mm, respectively.

[0013] When the lens L08 is a meniscus lens, the radii of curvature of its front and rear surfaces are 73.12mm ~ 73.77mm and 959.10mm ~ 2421.19mm, respectively; when it is a biconvex lens, the radii of curvature of its front and rear surfaces are 80.21mm ~ 91.89mm and -956.56mm ~ -369.42mm, respectively.

[0014] The half-apertures of the front and rear surfaces of lens L01 are 55.16mm~55.33mm and 51.55mm~51.84mm, respectively; those of lens L02 are 18.81mm~19.58mm and 18.31~19.47mm, respectively; those of lens L03 are 21.15mm~21.59mm and 21.13mm~21.53mm, respectively; those of lens L04 are 9.31mm~11.64mm and 9.45mm~11.32mm, respectively; those of lens L05 are 16.45mm~21.213mm and 19.48mm~25.42mm, respectively; and those of lens L06 are 33.83mm~36.01mm and 34.00mm, respectively. ~35.31mm; the half-apertures of the front and rear surfaces of lens L07 are 31.79mm~33.41mm and 32.29mm~33.31mm, respectively; the half-apertures of the front and rear surfaces of lens L08 are 34.68mm~35.54mm and 33.93mm~35.21mm, respectively.

[0015] The aspherical coefficients of the front surface of lens L02 are as follows: α2 is 5.74352E-06~6.59487E-06, α3 is -8.8832E-09~-5.8334E-09, α4 is 2.79946E-12~8.17305E-12, and α5 is -5.39834E-15~-1.4052E-15. The aspherical coefficients of the rear surface of lens L02 are as follows: α2 is 2.97467E-06 to 4.06627E-06, α3 is -6.05202E-09 to -2.781E-09, α4 is -1.546E-12 to 4.11114E-12, and α5 is -5.24756E-15 to -1.0119E-15. The aspherical coefficients of the rear surface of lens L03 are α2 (2.00314E-06~2.09001E-06), α3 (-1.1707E-09~-1.12499E-09), and α4 (9.58136E-13~1.05228E-12). The aspherical coefficients of the front surface of lens L04 are α2 (1.44273E-06~1.05775E-05), α3 (-2.32000E-08~-7.67573E-09), and α4 (1.51299E-11~5.29408E-11); The aspherical coefficients of the rear surface of lens L05 are α2 -3.8375E-06 to -1.47687E-06, α3 4.19317E-10 to 1.92248E-09, and α4 -2.94237E-12 to 1.35743E-12; The aspherical coefficients of the rear surface of lens L06 are α2 -1.2423E-06 to 1.1704E-06, α3 1.94971E-10 to 1.55536E-09, and α4 -4.09383E-13 to -1.2577E-13; The aspherical coefficients of the front surface of lens L07 are α2 -1.33646E-06~3.72673E-07, α3 6.99325E-10~2.70287E-09, and α4 -8.04544E-13~-2.636E-13; The aspherical coefficients of the front surface of lens L08 are α2 -1.77495E-06 to -1.4328E-06, α3 2.35046E-10 to 4.85534E-10, and α4 -1.86685E-13 to -7.49564E-14.

[0016] Lenses L01, L03, L05, L06, and L08 are all made of Si; lenses L02 and L07 are made of Ge; and lens L04 is made of zinc sulfide. Beneficial effects

[0017] 1. This invention achieves continuous zoom from 48mm to 205mm with a zoom ratio of 4.3x while ensuring high-resolution imaging, greatly improving the applicability of the zoom imaging system.

[0018] 2. The zoom imaging system of the present invention has an F-number of 2.0, which ensures that more energy is received by the detector compared with other lenses, thus greatly improving the resolution of the system.

[0019] 3. This invention optimizes the design of the imaging system by optimizing variables such as lens curvature radius, thickness, material, aspherical coefficient, and air gap between lenses, so that the transfer function of the zoom imaging system is better than 0.30@30lp / mm at +20℃, ensuring excellent image quality of the lens.

[0020] 4. During the design phase, the ratio of the back cutoff to the aperture of the last lens is controlled to ensure miniaturization while adapting to mainstream medium-wave cooled detectors.

[0021] 5. By selecting the optimal position of the moving lens, not only is the image quality of the imaging system excellent in harsh ambient temperatures ranging from -40℃ to +65℃, but the structural design space of the focusing cam is also guaranteed, providing an important reference for subsequent assembly and adjustment as well as lens miniaturization.

[0022] 6. The zoom imaging system does not use a diffraction surface, which improves the system's optical transmittance. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a miniaturized three-component continuous zoom mid-wave cooled infrared optical system based on existing technology.

[0024] Figure 2 This is a diagram of the short focal length 48mm optical structure of Embodiment 1 of the present invention.

[0025] Figure 3 This is a diagram of the 205mm telephoto optical structure of Embodiment 1 of the present invention.

[0026] Figure 4 This is the optical transfer function diagram of the short focal length 48mm of Embodiment 1 of the present invention at +20℃.

[0027] Figure 5 This is the optical transfer function diagram of the 205mm telephoto lens in Embodiment 1 of the present invention at +20℃.

[0028] Figure 6 This is a distortion image of the short focal length 48mm of Embodiment 1 of the present invention at +20℃.

[0029] Figure 7 This is a distortion image of a 205mm telephoto lens in Embodiment 1 of the present invention at +20℃.

[0030] Figure 8 This is the relative illumination diagram of the short focal length 48mm of Embodiment 1 of the present invention at +20℃.

[0031] Figure 9 This is the relative illumination diagram of the telephoto lens at 205mm in Embodiment 1 of the present invention at +20℃.

[0032] Figure 10 This is the optical transfer function diagram of the short focal length 48mm of Embodiment 1 of the present invention at -40℃.

[0033] Figure 11 This is the optical transfer function diagram of the 205mm telephoto lens in Embodiment 1 of the present invention at -40℃.

[0034] Figure 12This is the optical transfer function diagram of the short focal length 48mm of Embodiment 1 of the present invention at +65℃.

[0035] Figure 13 This is the optical transfer function diagram of the 205mm telephoto lens in Embodiment 1 of the present invention at +65℃.

[0036] Figure 14 This is a diagram of the short focal length 48mm optical structure of Embodiment 2 of the present invention.

[0037] Figure 15 This is a diagram of the 205mm telephoto optical structure of Embodiment 2 of the present invention.

[0038] Figure 16 This is a diagram of the short focal length 48mm optical structure of Embodiment 3 of the present invention.

[0039] Figure 17 This is a diagram of the 205mm telephoto optical structure of Embodiment 3 of the present invention.

[0040] Figure 18 This is a diagram of the short focal length 48mm optical structure of Embodiment 4 of the present invention.

[0041] Figure 19 This is a diagram of the 205mm telephoto optical structure of Embodiment 4 of the present invention. Detailed Implementation

[0042] 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 for explaining the present invention and are not intended to limit the present invention. Furthermore, it should be noted that, for ease of description, only the parts relevant to the present invention are shown in the drawings, not the entire structure.

[0043] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0044] In the description of this embodiment, the terms "upper," "lower," "left," and "right," etc., refer to the orientation or positional relationship shown in the accompanying drawings. They are used only for ease of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention. In addition, the terms "first" and "second" are used only for distinction in description and have no special meaning.

[0045] like Figure 2 As shown, the compact high-resolution mid-wave zoom imaging system of the present invention consists of lenses L01, L02, L03, L04, L05, L06, L07, and L08 arranged coaxially along the direction of light propagation, a detector window WIN, a detector protective glass FIL, a stop stop, and an image plane IMAGE. Lens L01 forms the front fixed group, lens L02 forms the zoom group, lens L03 forms the compensation group, lens L04 forms the focusing group, and lenses L05, L06, and L08 form the rear fixed group. The zoom imaging process achieves the change of focal length by axially moving the zoom group and the compensation group, while ensuring that the image plane position does not change. Axial movement of the focusing group within the lens barrel compensates for defocusing caused by temperature changes, ensuring clear imaging of the system at different temperatures.

[0046] The equations for aspherical surfaces are as follows:

[0047] In this embodiment, k is the conic coefficient, with a value of 0. The aspherical coefficients α1, α2, α3, α4, α5, α6, α7, and α8 are the 2nd, 4th, 6th, 8th, 10th, 12th, 14th, and 16th powers of the radial coordinates, respectively; z represents the lens sagitta; c represents the vertex curvature of the lens; and r represents the half-aperture value of the lens.

[0048] The focal lengths f1 of the front fixed group, f2 of the zoom group, f3 of the compensation group, f4 of the focusing group, and f5 of the rear fixed group satisfy the following relationships: 0.420≤f1 / f≤0.454; -0.08≤f2 / f≤0.073; 0.106≤f3 / f≤0.108; -0.376≤f4 / f≤-0.32; 0.141≤f5 / f≤0.157, where f is the focal length of the zoom imaging system at the telephoto end.

[0049] Furthermore, the ratio of the aperture L8S2D of the back focal length BFL and the lens L08 in the zoom imaging system satisfies: 1.3≤BFL / L8S2D≤1.4.

[0050] By calculating material combinations and adjusting the air gap between each lens, the imaging system achieves a transfer function better than 0.30@30lp / mm at +20℃, ensuring excellent image quality. With an aluminum alloy lens barrel, the L04 focusing lens axial motion compensation system compensates for defocusing at different temperatures, ensuring the image plane position remains constant. This ensures the entire system meets the required image quality within a temperature range of -40℃ to +65℃. Example

[0051] Lens L01 is a positive meniscus lens with its convex surface facing the object side; lens L02 is a biconcave lens; lens L03 is a biconvex lens; lens L04 is a negative meniscus lens with its convex surface facing the image side; lens L05 is a negative meniscus lens with its convex surface facing the image side; lens L06 is a biconvex lens; lens L07 is a biconcave lens; and lens L08 is a positive meniscus lens with its convex surface facing the object side. Lens L01 is a spherical lens; the front surfaces of lenses L04, L07, and L08 are aspherical, and their rear surfaces are spherical; the front surfaces of lenses L03, L05, and L06 are spherical, and their rear surfaces are aspherical; and the front and rear surfaces of lens L02 are aspherical. Lenses L01, L03, L05, L06, and L08 are made of Si; lenses L02 and L07 are made of Ge; and lens L04 is made of zinc sulfide.

[0052] In this embodiment, the parameters of each element, such as surface shape, radius of curvature, distance from the next optical surface, material, and half-aperture, are shown in Table 1, and the aspherical coefficient is shown in Table 2. The units for radius of curvature, thickness / spacing, and half-aperture are mm.

[0053] Table 1

[0054] Table 2

[0055] This invention can achieve the following indicators: a) Focal length: 48.0~205.0mm; b) F / #: 2.0; c) Band: 3700–4800 nm; d) Field of view: 11.42° × 9.15°~ 2.68° × 2.15°; e) Distortion: <3%; f) MTF: >0.30@30lp / mm; g) Operating temperature: -40℃~+65℃ Depend on Figure 4 , 5The modulation transfer function curve shows that at a detector frequency of 30 lp / mm and a temperature of +20°C, the MTF values ​​of all fields of view of the zoom imaging system, both short and long focal lengths, are better than 0.30, which meets the resolution requirements of the optical system.

[0056] Depend on Figure 10 , 11 The modulation transfer function curve shows that at a detector frequency of 30 lp / mm, the MTF values ​​of all fields of view of the zoom imaging system at -40℃ are better than 0.25 for both short and long focal lengths, which meets the resolution requirements of the optical system.

[0057] Depend on Figure 12 , 13 The modulation transfer function curve shows that at a detector frequency of 30 lp / mm and a temperature of +65°C, the MTF values ​​of all fields of view for both short and long focal lengths of the zoom imaging system are better than 0.2, which meets the resolution requirements of the optical system. Example

[0058] Lens L01 is a meniscus positive lens with its convex surface facing the object side; lens L02 is a biconcave lens; lens L03 is a biconvex lens; lens L04 is a biconcave lens; lens L05 is a meniscus negative lens with its convex surface facing the image side; lens L06 is a biconvex lens; lens L07 is a biconcave lens; and lens L08 is a meniscus positive lens with its convex surface facing the object side. Lens L01 is a spherical lens; the front surfaces of lenses L04, L07, and L08 are aspherical, and their rear surfaces are spherical; the front surfaces of lenses L03, L05, and L06 are spherical, and their rear surfaces are aspherical; and the front and rear surfaces of lens L02 are aspherical. Lenses L01, L03, L05, L06, and L08 are made of Si; lenses L02 and L07 are made of Ge; and lens L04 is made of zinc sulfide.

[0059] In this embodiment, the parameters of each element, such as surface shape, radius of curvature, distance from the next optical surface, material, and half-aperture, are shown in Table 3, and the aspherical coefficient is shown in Table 4. The units for radius of curvature, thickness / spacing, and half-aperture are mm.

[0060] Table 3

[0061] Table 4

[0062] This invention can achieve the following indicators: a) Focal length: 48.0~205.0mm; b) F / #: 2.0; c) Band: 3700–4800 nm; d) Field of view: 11.42° × 9.15°~ 2.68° × 2.15°; e) Distortion: <3%; f) MTF: >0.30@30lp / mm; g) Operating temperature: -40℃~+65℃ Example

[0063] Lens L01 is a positive meniscus lens with its convex surface facing the object side; lens L02 is a biconcave lens; lens L03 is a biconvex lens; lens L04 is a negative meniscus lens with its convex surface facing the image side; lens L05 is a negative meniscus lens with its convex surface facing the image side; lens L06 is a biconvex lens; lens L07 is a negative meniscus lens with its concave surface facing the object side; and lens L08 is a biconvex lens. Lens L01 is a spherical lens; the front surfaces of lenses L04, L07, and L08 are aspherical, and their rear surfaces are spherical; the front surfaces of lenses L03, L05, and L06 are spherical, and their rear surfaces are aspherical; the front and rear surfaces of lens L02 are aspherical. Lenses L01, L03, L05, L06, and L08 are made of Si; lenses L02 and L07 are made of Ge; and lens L04 is made of zinc sulfide.

[0064] In this embodiment, the parameters of each element, such as surface shape, radius of curvature, distance from the next optical surface, material, and half-aperture, are shown in Table 5, and the aspherical coefficient is shown in Table 6. The units for radius of curvature, thickness / spacing, and half-aperture are mm.

[0065] Table 5

[0066] Table 6

[0067] This invention can achieve the following indicators: a) Focal length: 48.0~205.0mm; b) F / #: 2.0; c) Band: 3700–4800 nm; d) Field of view: 11.42° × 9.15°~ 2.68° × 2.15°; e) Distortion: <3%; f) MTF: >0.30@30lp / mm; g) Operating temperature: -40℃~+65℃ Example

[0068] Lens L01 is a positive meniscus lens with its convex surface facing the object side; lens L02 is a biconcave lens; lens L03 is a biconvex lens; lens L04 is a biconcave lens; lens L05 is a negative meniscus lens with its convex surface facing the image side; lens L06 is a biconvex lens; lens L07 is a negative meniscus lens with its concave surface facing the object side; and lens L08 is a biconvex lens. Lens L01 is a spherical lens; the front surfaces of lenses L04, L07, and L08 are aspherical, and their rear surfaces are spherical; the front surfaces of lenses L03, L05, and L06 are spherical, and their rear surfaces are aspherical; the front and rear surfaces of lens L02 are both aspherical. Lenses L01, L03, L05, L06, and L08 are made of Si; lenses L02 and L07 are made of Ge; and lens L04 is made of zinc sulfide.

[0069] In this embodiment, the parameters of each element, such as surface shape, radius of curvature, distance from the next optical surface, material, and half-aperture, are shown in Table 7, and the aspherical coefficient is shown in Table 8. The units for radius of curvature, thickness / spacing, and half-aperture are mm.

[0070] Table 7

[0071] Table 8

[0072] This invention can achieve the following indicators: a) Focal length: 48.0~205.0mm; b) F / #: 2.0; c) Band: 3700–4800 nm; d) Field of view: 11.42° × 9.15°~ 2.68° × 2.15°; e) Distortion: <3%; f) MTF: >0.30@30lp / mm; g) Operating temperature: -40℃~+65℃

[0073] This invention reduces the F-number of the lens focal length, thereby improving the lens resolution; the F-number is 2.0.

[0074] 2. The present invention adopts a zoom method consisting of two moving elements, a zoom group (lens L02) and a compensation group (lens L03), and selects the smallest lens as the focusing lens, which provides stable support for structural design, assembly space and reliability of lens group movement, while also reducing the complexity of the lens structure.

[0075] 3. In the design phase, this invention increases the lens back focal length by controlling the ratio of the back focal length to the final lens aperture, which can meet most assembly and usage requirements and is compatible with mainstream medium-wave cooled detectors.

[0076] 4. The optical system of this invention does not use a diffraction surface, which greatly improves the overall transmittance of the system, and the choice of an aspherical surface is also significant.

Claims

1. A compact, high-resolution mid-wave zoom imaging system, characterized in that: The system consists of lenses L01, L02, L03, L04, L05, L06, L07, and L08, arranged coaxially along the positive optical axis and in the direction of light propagation, along with a detector window, detector protective glass, a cold stop, and an image plane. Lens L01 forms the front fixed group, lens L02 forms the zoom group, lens L03 forms the compensation group, and lens L04 forms the focusing group. Lenses L05, L06, L07, and L08 form the rear fixed group. The focal length is changed by axial movement of the zoom and compensation groups, and defocusing caused by temperature changes is compensated by axial movement of the focusing group. The focal lengths f1 of the front fixed group, f2 of the zoom group, f3 of the compensation group, f4 of the focusing group, and f5 of the rear fixed group satisfy the following relationship: 0.420 ≤ f1 / f ≤ 0.45 4; -0.08≤f2 / f≤-0.073; 0.106≤f3 / f≤0.108; -0.376≤f4 / f≤-0.32; 0.141≤f5 / f≤0.157, where f is the focal length of the imaging system at telephoto; lens L01 is a meniscus positive lens with its convex surface facing the object side, lens L02 is a biconcave lens, lens L03 is a biconvex lens, lens L04 is a negative lens, and lens L05... Lens L06 is a biconvex positive lens, lens L07 is a negative lens, and lens L08 is a positive lens. Lens L01 is a spherical lens. The front surfaces of lenses L04, L07, and L08 are aspherical, and the rear surfaces are spherical. The front surfaces of lenses L03, L05, and L06 are spherical, and the rear surfaces are aspherical. The front and rear surfaces of lens L02 are both aspherical.

2. The compact high-resolution mid-wave zoom imaging system according to claim 1, characterized in that: The radii of curvature of the front and rear surfaces of the lens L01 are 85.38 mm to 92.02 mm and 126.83 mm to 137.69 mm, respectively. The radii of curvature of the front and rear surfaces of lens L02 are -112.44 mm to -111.14 mm and 78.28 mm to 85.41 mm, respectively. The radii of curvature of the front and rear surfaces of lens L03 are 102.35mm~105.62mm and -106.25mm~ -99.76mm, respectively. The radii of curvature of the front and rear surfaces of lens L05 are -33.69mm to -25.31mm and -44.88mm to -38.94mm, respectively. The radii of curvature of the front and rear surfaces of lens L06 are 99.77mm~219.52mm and -122.85mm~-77.44mm, respectively.

3. The compact high-resolution mid-wave zoom imaging system according to claim 2, characterized in that: The thicknesses of lenses L01, L02, L03, L04, L05, L06, L07, and L08 are 14.63mm~15mm, 2.98mm~2.99mm, 6.97mm~7.14mm, 2.99mm~3mm, 4.4mm~7mm, 13.6mm~15.01mm, 4.99mm~5.00mm, and 10.2mm~10.6mm, respectively.

4. The compact high-resolution mid-wave zoom imaging system according to claim 3, characterized in that: The air gap between lens L01 and lens L02 is 34.27mm to 51.03mm, the air gap between lens L02 and lens L03 is 4.96mm to 34.44mm, the air gap between lens L03 and L04 is 9.07mm to 31.12mm, the air gap between lens L04 and lens L05 is 64.92mm to 70.07mm, the air gap between lens L05 and lens L06 is 4.38mm to 14.3mm, the air gap between lens L06 and lens L07 is 1.18mm to 4.38mm, and the air gap between lens L07 and lens L08 is 4.43mm to 8.33mm.

5. The compact high-resolution mid-wave zoom imaging system according to claim 1, characterized in that: Lens L04 is a meniscus negative lens with its concave surface facing the object or a biconcave lens; lens L07 is a meniscus negative lens with its concave surface facing the object or a biconcave lens; lens L08 is a meniscus positive lens with its convex surface facing the object or a biconvex lens.

6. The compact high-resolution mid-wave zoom imaging system according to claim 1, characterized in that: When lens L04 is a meniscus negative lens, the radii of curvature of its front and rear surfaces are -44.05mm to -31.99mm and -95.35mm to -55.58mm, respectively; when it is a biconcave lens, the radii of curvature of its front and rear surfaces are -142.58mm to -138.91mm and 300.00mm to 300.09mm, respectively. When lens L07 is a meniscus negative lens, the radii of curvature of its front and rear surfaces are -73.44mm to -69.45mm and -500.00mm, respectively; when it is a biconcave lens, the radii of curvature of its front and rear surfaces are -163.04mm to -154.99mm and 161.99mm to 169.25mm, respectively. When lens L08 is a meniscus positive lens, the radii of curvature of its front and rear surfaces are 73.12mm. ~73.77mm and 959.10mm~2421.19mm; when it is a biconvex lens, the radii of curvature of its front and rear surfaces are 80.21mm~91.89mm and -956.56mm~-369.42mm, respectively.

7. The compact high-resolution mid-wave zoom imaging system according to claim 1, characterized in that: The half-apertures of the front and rear surfaces of lens L01 are 55.16mm~55.33mm and 51.55mm~51.84mm, respectively; those of lens L02 are 18.81mm~19.58mm and 18.31~19.47mm, respectively; those of lens L03 are 21.15mm~21.59mm and 21.13mm~21.53mm, respectively; those of lens L04 are 9.31mm~11.64mm and 9.45mm~11.32mm, respectively; those of lens L05 are 16.45mm~21.213mm and 19.48mm~25.42mm, respectively; and those of lens L06 are 33.83mm~36.01mm and 34.00mm, respectively. ~35.31mm; the half-apertures of the front and rear surfaces of lens L07 are 31.79mm~33.41mm and 32.29mm~33.31mm, respectively; the half-apertures of the front and rear surfaces of lens L08 are 34.68mm~35.54mm and 33.93mm~35.21mm, respectively.

8. The compact high-resolution mid-wave zoom imaging system according to claim 1, characterized in that: The aspherical coefficients of the front surface of lens L02 are as follows: α2 is 5.74352E-06~6.59487E-06, α3 is -8.8832E-09~-5.8334E-09, α4 is 2.79946E-12~8.17305E-12, and α5 is -5.39834E-15~-1.4052E-15. The aspherical coefficients of the rear surface of lens L02 are as follows: α2 is 2.97467E-06 to 4.06627E-06, α3 is -6.05202E-09 to -2.781E-09, α4 is -1.546E-12 to 4.11114E-12, and α5 is -5.24756E-15 to -1.0119E-15. The aspherical coefficients of the rear surface of lens L03 are α2 (2.00314E-06~2.09001E-06), α3 (-1.1707E-09~-1.12499E-09), and α4 (9.58136E-13~1.05228E-12). The aspherical coefficients of the front surface of lens L04 are α2 (1.44273E-06~1.05775E-05), α3 (-2.32000E-08~-7.67573E-09), and α4 (1.51299E-11~5.29408E-11); The aspherical coefficients of the rear surface of lens L05 are α2 -3.8375E-06 to -1.47687E-06, α3 4.19317E-10 to 1.92248E-09, and α4 -2.94237E-12 to 1.35743E-12; The aspherical coefficients of the rear surface of lens L06 are α2 -1.2423E-06 to 1.1704E-06, α3 1.94971E-10 to 1.55536E-09, and α4 -4.09383E-13 to -1.2577E-13; The aspherical coefficients of the front surface of lens L07 are α2 -1.33646E-06~3.72673E-07, α3 6.99325E-10~2.70287E-09, and α4 -8.04544E-13~-2.636E-13; The aspherical coefficients of the front surface of lens L08 are α2 -1.77495E-06 to -1.4328E-06, α3 2.35046E-10 to 4.85534E-10, and α4 -1.86685E-13 to -7.49564E-14.

9. The compact high-resolution mid-wave zoom imaging system according to claim 1, characterized in that: Lenses L01, L03, L05, L06, and L08 are all made of Si; lenses L02 and L07 are made of Ge; and lens L04 is made of zinc sulfide.

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