A refrigeration type middle wave infrared continuous zoom lens

Abstract

The present application relates to the technical field of optical system, and particularly relates to a refrigeration type middle wave infrared continuous zoom lens, which comprises a front fixed group, a zoom group, a compensation group, a rear fixed group, a primary image plane, a relay lens group and a refrigeration detector; the lens adopts a positive compensation method, the zoom group has a negative optical power, the compensation group has a positive optical power, a single-surface aspheric lens is introduced into the compensation group and the rear fixed group, a primary imaging plane is introduced into the lens, and a relay lens group is added to further eliminate aberration, so that a zoom ratio greater than 20X is realized, a total optical length and a long focus focal length ratio TTL / fl is less than 0.6, a resolution is close to a diffraction limit, and distortion is less than 5%, thereby solving the problem that a traditional infrared zoom lens is limited by spherical aberration and the resolution is far lower than the diffraction limit.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and in particular to a cooled mid-wave infrared continuous zoom lens. Background Art

[0002] An infrared continuous zoom system has a continuously variable focal length, which can help observers achieve long-distance high-magnification observation and rough observation and identification of targets within a large field of view.

[0003] Zoom optical systems are used in increasingly wide application fields and are developing towards large zoom ratios, long focal lengths, high resolution and other directions. However, traditional infrared zoom lenses mostly adopt an all-spherical design, which is limited by spherical aberration, resulting in insufficient high-order aberration correction. The system resolution is far lower than the diffraction limit, cannot fully exert the imaging capability of high-pixel cooled detectors, and restricts the system detection range and identification accuracy. Summary of the Invention

[0004] The object of the present invention is to provide a cooled mid-wave infrared continuous zoom lens, aiming to solve the problem that traditional infrared zoom lenses are limited by spherical aberration and their resolution is far lower than the diffraction limit.

[0005] To achieve the above object, the present invention provides a cooled mid-wave infrared continuous zoom lens, comprising a front fixed group, a zooming group, a compensation group, a rear fixed group, a primary image plane, a relay lens group, and a cooled detector; the zooming group is arranged on one side of the front fixed group, the compensation group is arranged on a side of the zooming group away from the front fixed group, the rear fixed group is arranged on a side of the compensation group away from the zooming group, the relay lens group is arranged on a side of the rear fixed group away from the compensation group, the primary image plane is arranged between the rear fixed group and the relay lens group, and the cooled detector is arranged on a side of the relay lens group away from the primary image plane.

[0006] Wherein, the front fixed group consists of 3 spherical lenses, the overall optical power is positive, and the focal length range satisfies 200<f1<240, and the lenses are, sequentially from the object side to the image side, a first lens, a second lens, and a third lens; The first lens is a spherical lens, the curvature radii of the object-side surface and the image-side surface are both greater than 0, the first lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The second lens is a spherical lens, the curvature radii of the object-side surface and the image-side surface are both greater than 0, the second lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The third lens is a spherical lens, the curvature radii of the object-side surface and the image-side surface are both greater than 0, the third lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface.

[0007] wherein, the zoom group consists of 3 spherical lenses, the overall optical power is negative, and the focal length range satisfies -40<f2<-25, which are sequentially the fourth lens, the fifth lens and the sixth lens from the object side to the image side; the fourth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the surfaces are curved toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; the fifth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the surfaces are curved toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; the sixth lens is a spherical lens, the curvature radius of the object-side surface is less than 0, the surface is curved away from the detector, the object-side surface is a concave surface, the curvature radius of the image-side surface is greater than 0, the surface is curved toward the detector, and the image-side surface is a concave surface.

[0008] wherein, the compensation group consists of 1 single-sided aspheric lens, the optical power is positive, and the focal length range satisfies 30<f3<40, the single-sided aspheric lens is the seventh lens, the curvature radius of the object-side surface of the seventh lens is greater than 0, the surface is curved toward the detector, the object-side surface is a convex surface and is a convex aspheric surface, which satisfies the aspheric equation: ; wherein, z is the surface sag, r is the radial radius, c is the curvature, k is the conic coefficient, A, B, C, D, E, F, G, H are aspheric coefficients, the curvature radius of the image-side surface of the seventh lens is less than 0, the surface is curved away from the detector, and the image-side surface is a convex spherical surface.

[0009] wherein, the rear fixed group consists of 1 single-sided aspheric lens and 5 spherical lenses, the overall optical power is positive, and the focal length range satisfies 35<f4<45, which are sequentially the eighth lens, the ninth lens, the tenth lens, the eleventh lens, the twelfth lens and the thirteenth lens from the object side to the image side.

[0010] the eighth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the surfaces are curved toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; the ninth lens is a single-sided aspheric lens, the curvature radius of the object-side surface of the ninth lens is greater than 0, the surface is curved toward the detector, the object-side surface is a convex surface and is a convex aspheric surface, which satisfies the aspheric equation: ; wherein, z is the surface sag, r is the radial radius, c is the curvature, k is the conic coefficient, A, B, C, D, E, F, G, H are aspheric coefficients, the curvature radius of the image-side surface of the ninth lens is greater than 0, the surface is curved toward the detector, and the image-side surface is a concave spherical surface; the tenth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the surfaces are curved toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The eleventh lens is a spherical lens, the radius of curvature of the object-side surface can be greater than 0 or less than 0, and the surface curves toward the detector; the radius of curvature of the image-side surface is greater than 0, the surface curves toward the detector, and the image-side surface is a concave surface; The twelfth lens is a spherical lens, the radii of curvature of both the object-side surface and the image-side surface are greater than 0, both surfaces curve toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The thirteenth lens is a spherical lens, the radii of curvature of both the object-side surface and the image-side surface are less than 0, both surfaces curve away from the detector, the object-side surface is a concave surface, and the image-side surface is a convex surface.

[0011] Wherein, the relay lens group consists of 5 spherical lenses, has a positive overall optical power, and satisfies the focal length range of 5<f6<35, and sequentially comprises a fourteenth lens, a fifteenth lens, a sixteenth lens, a seventeenth lens and an eighteenth lens from the object side to the image side; The fourteenth lens is a spherical lens, the radii of curvature of both the object-side surface and the image-side surface are greater than 0, both surfaces curve toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The fifteenth lens is a spherical lens, the radius of curvature of the object-side surface is greater than 0, the surface curves toward the detector, and the object-side surface is a convex surface; the radius of curvature of the image-side surface is less than 0, the surface curves away from the detector, and the image-side surface is a convex surface; The sixteenth lens is a spherical lens, the radii of curvature of both the object-side surface and the image-side surface are greater than 0, both surfaces curve toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The seventeenth lens is a spherical lens, the radii of curvature of both the object-side surface and the image-side surface are greater than 0, both surfaces curve toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The eighteenth lens is a spherical lens, the radius of curvature of the object-side surface is less than 0, the surface curves away from the detector, and the object-side surface is a concave surface; the radius of curvature of the image-side surface can be greater than 0 or less than 0, and the surface curves away from the detector.

[0012] Beneficial effects: The lens adopts a positive group compensation method, wherein the zoom group has negative optical power and the compensation group has positive optical power. A single-sided aspheric lens is introduced into each of the compensation group and the rear fixed group, the primary image plane is introduced into the lens, and the relay lens group is added to further eliminate aberrations. This achieves a zoom ratio greater than 20X, a ratio of total optical length to long focal length TTL / fl<0.6, a resolution close to the diffraction limit, and a distortion less than 5%, thereby solving the problem that traditional infrared zoom lenses are limited by spherical aberration and have a resolution far lower than the diffraction limit. Description of Drawings

[0013] To more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings required for the description of the embodiments or the prior art will be briefly introduced below.

[0014] Figure 1 This is a schematic diagram of the lens structure in Embodiment 1 of the present invention.

[0015] Figure 2 This is a schematic diagram of the MTF resolution curve of Embodiment 1 of the present invention.

[0016] Figure 3 This is a schematic diagram of lens distortion in Embodiment 1 of the present invention.

[0017] Figure 4 This is a schematic diagram of the lens structure in Embodiment 2 of the present invention.

[0018] Figure 5 This is a schematic diagram of the MTF resolution curve of Embodiment 2 of the present invention.

[0019] Figure 6 This is a schematic diagram of lens distortion in Embodiment 2 of the present invention.

[0020] Figure 7 This is a schematic diagram of the lens structure in Embodiment 3 of the present invention.

[0021] Figure 8 This is a schematic diagram of the MTF resolution curve of Embodiment 3 of the present invention.

[0022] Figure 9 This is a schematic diagram of lens distortion in Embodiment 3 of the present invention.

[0023] Figure 10 This is a connection diagram of a cooled mid-wave infrared continuous zoom lens provided by the present invention.

[0024] In the diagram: 1-Front fixed group, 2-Magnification group, 3-Compensation group, 4-Rear fixed group, 5-Primary image plane, 6-Relay mirror group, 7-Cooled detector. Detailed Implementation

[0025] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0026] Please see Figure 1-10 The present invention provides a cooled mid-wave infrared continuous zoom lens, comprising a front fixed group 1, a zoom group 2, a compensation group 3, a rear fixed group 4, a primary image plane 5, a relay lens group 6, and a cooled detector 7. The zoom group 2 is disposed on one side of the front fixed group 1, the compensation group 3 is disposed on the side of the zoom group 2 away from the front fixed group 1, the rear fixed group 4 is disposed on the side of the compensation group 3 away from the zoom group 2, the relay lens group 6 is disposed on the side of the rear fixed group 4 away from the compensation group 3, the primary image plane 5 is disposed between the rear fixed group 4 and the relay lens group 6, and the cooled detector 7 is disposed on the side of the relay lens group 6 away from the primary image plane 5.

[0027] Beneficial effects: This lens employs a positive compensation method, where the zoom group 2 has a negative optical power and the compensation group 3 has a positive optical power. A single-sided aspherical lens is introduced into each of the compensation group 3 and the rear fixed group 4, and the primary imaging plane is introduced into the lens. The relay lens group 6 is added to further eliminate aberrations, achieving a zoom ratio greater than 20X, an optical total length to telephoto focal length ratio (TTL / fl) < 0.6, a resolution close to the diffraction limit, and distortion less than 5%. This solves the problem that traditional infrared zoom lenses are limited by spherical aberration, resulting in a resolution far below the diffraction limit.

[0028] Example 1: This embodiment is designed as a cooled mid-wave infrared continuous zoom lens with a mid-wave wavelength range of 3-5µm, F / #=5.5, focal length range of 30mm-650mm, zoom ratio of 21.5X, detector pixel count of 640*512, pixel size of 15µm, optical total length to telephoto focal length ratio TTL / fl=0.46, and distortion of less than 5%.

[0029] Front fixed group 1 focal length: 219.79mm; zoom group 2 focal length: -37.4mm; compensation group 3 focal length: 39.31mm; rear fixed group 4 focal length: 41.7mm; repeater group 6 focal length: 34.92mm.

[0030] Detailed lens parameters for Example 1 are shown in Table 1: Table 1 ; ; ; Example 1 Lens structure as follows Figure 1 As shown, the MTF resolution curve of Example 1 is close to the diffraction limit, with distortion <5%.

[0031] Example 2: This embodiment is designed as a cooled mid-wave infrared continuous zoom lens with a mid-wave wavelength range of 3-5µm, F / #=5.5, focal length range of 25mm-600mm, zoom ratio of 24X, detector pixel count of 640*512, pixel size of 15µm, optical total length to telephoto focal length ratio TTL / fl=0.5, and distortion of less than 5%.

[0032] Front fixed group 1 focal length: 224mm; zoom group 2 focal length: -30.75mm; compensation group 3 focal length: 37.21mm; rear fixed group 4 focal length: 37.12mm; repeater group 6 focal length: 8.77mm.

[0033] Detailed lens parameters for Example 2 are shown in Table 2: Table 2 ; ; ; Example 2 Lens structure as follows Figure 4 As shown, the lens structure in Embodiment 2 is as follows Figure 4 As shown, the distortion is <5%.

[0034] Example 3: This embodiment is designed as a cooled mid-wave infrared continuous zoom lens with a mid-wave wavelength range of 3-5µm, F / #=5.5, focal length range of 30mm-550mm, zoom ratio of 27.5X, detector pixel count of 640*512, pixel size of 15µm, optical total length to telephoto focal length ratio TTL / fl=0.56, and distortion of less than 5%.

[0035] Front fixed group 1 focal length: 230.9mm; zoom group 2 focal length: -26mm; compensation group 3 focal length: 32.89mm; rear fixed group 4 focal length: 36.39mm; repeater group 6 focal length: 9.54mm.

[0036] Detailed lens parameters for Example 3 are shown in Table 3: Table 3 ; ; ; Example 3 Lens structure as follows Figure 7 As shown, the MTF resolution curve of Example 3 is close to the diffraction limit, with distortion <5%.

[0037] The above-disclosed embodiments are merely preferred embodiments of a cooled mid-wave infrared continuous zoom lens of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A cooled medium-wave infrared continuous zoom lens, characterized in that, comprising a front fixed group, a zooming group, a compensation group, a rear fixed group, a primary image plane, a relay lens group, and a cooled detector; the zooming group is arranged on one side of the front fixed group, the compensation group is arranged on a side of the zooming group away from the front fixed group, the rear fixed group is arranged on a side of the compensation group away from the zooming group, the relay lens group is arranged on a side of the rear fixed group away from the compensation group, the primary image plane is arranged between the rear fixed group and the relay lens group, and the cooled detector is arranged on a side of the relay lens group away from the primary image plane.

2. The cooled medium-wave infrared continuous zoom lens according to claim 1, characterized in that, the front fixed group consists of 3 spherical lenses, the overall optical power is positive, the focal length range satisfies 200<f1<240, and the lenses are a first lens, a second lens and a third lens in sequence from the object side to the image side; the first lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the first lens bends toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; the second lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the second lens bends toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; the third lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the third lens bends toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface.

3. The cooled medium-wave infrared continuous zoom lens according to claim 1, characterized in that, the zooming group consists of 3 spherical lenses, the overall optical power is negative, the focal length range satisfies -40<f2<-25, and the lenses are a fourth lens, a fifth lens and a sixth lens in sequence from the object side to the image side; the fourth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the fourth lens bends toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; the fifth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the fifth lens bends toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; the sixth lens is a spherical lens, the curvature radius of the object-side surface is less than 0, the sixth lens bends away from the detector, the object-side surface is a concave surface, the curvature radius of the image-side surface is greater than 0, the image-side bends toward the detector, and the image-side surface is a concave surface.

4. The cooled medium-wave infrared continuous zoom lens according to claim 1, characterized in that, the compensation group consists of 1 single-sided aspheric lens, the optical power is positive, the focal length range satisfies 30<f3<40, the single-sided aspheric lens is a seventh lens, the curvature radius of the object-side surface of the seventh lens is greater than 0, the seventh lens bends toward the detector, the object-side surface is a convex surface and is a convex aspheric surface, satisfying the aspheric equation: ； wherein, z is the surface sag, r is the radial radius, c is the curvature, k is the conic coefficient, A, B, C, D, E, F, G, H are aspheric coefficients, the curvature radius of the image-side surface of the seventh lens is less than 0, the seventh lens bends away from the detector, and the image-side surface is a convex spherical surface.

5. The cooled medium-wave infrared continuous zoom lens according to claim 1, characterized in that, The rear fixed group consists of 1 single-sided aspheric lens and 5 spherical lenses, has a positive overall optical power, and its focal length range satisfies 35<f4<45, and comprises an eighth lens, a ninth lens, a tenth lens, an eleventh lens, a twelfth lens and a thirteenth lens in sequence from the object side to the image side; The eighth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the eighth lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The ninth lens is a single-sided aspheric lens, the curvature radius of the object-side surface of the ninth lens is greater than 0, the object-side surface curves toward the detector, the object-side surface is a convex surface and is a convex aspheric surface, which satisfies the aspheric equation: ； wherein z is the surface sag, r is the radial radius, c is the curvature, k is the conic coefficient, and A, B, C, D, E, F, G, H are aspheric coefficients; the curvature radius of the image-side surface of the ninth lens is greater than 0, the image-side surface curves toward the detector, and the image-side surface is a concave spherical surface; The tenth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the tenth lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The eleventh lens is a spherical lens, the curvature radius of the object-side surface can be greater than 0 or less than 0, the object-side surface curves toward the detector, the curvature radius of the image-side surface is greater than 0, the image-side surface curves toward the detector, and the image-side surface is a concave surface; The twelfth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the twelfth lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The thirteenth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are less than 0, the thirteenth lens curves away from the detector, the object-side surface is a concave surface, and the image-side surface is a convex surface.

6. The cooled mid-wave infrared continuous zoom lens according to claim 1, characterized in that, The relay lens group consists of 5 spherical lenses, has a positive overall optical power, and its focal length range satisfies 5<f6<35, and comprises a fourteenth lens, a fifteenth lens, a sixteenth lens, a seventeenth lens and an eighteenth lens in sequence from the object side to the image side; The fourteenth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the fourteenth lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The fifteenth lens is a spherical lens, the curvature radius of the object-side surface is greater than 0, the object-side surface curves toward the detector, the object-side surface is a convex surface, the curvature radius of the image-side surface is less than 0, the image-side surface curves away from the detector, and the image-side surface is a convex surface; The sixteenth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the sixteenth lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The seventeenth lens is a spherical lens, the curvature radii of both the object-side surface and the image-side surface are greater than 0, the seventeenth lens curves toward the detector, the object-side surface is a convex surface, and the image-side surface is a concave surface; The eighteenth lens is a spherical lens, the curvature radius of the object-side surface is less than 0, the object-side surface curves away from the detector, the object-side surface is a concave surface, the curvature radius of the image-side surface can be greater than 0 or less than 0, and the image-side surface curves away from the detector.

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