Continuous zooming long-wave infrared lens suitable for large-target-surface uncooled detector

Abstract

The invention discloses a continuous zooming long-wave infrared lens suitable for a large-target-surface uncooled detector, which is characterized in that seven lenses are arranged from an object side to an image side, and a structural form of primary imaging, negative group zooming and positive group compensation zooming is adopted; a front fixed group lens, a zoom lens, a first compensation group lens, a second compensation group lens, a first rear group lens, a second rear group lens and a third rear group lens are sequentially arranged from an object space to an image space along an optical axis; during continuous zooming, the zoom lens moves towards the object space, the first compensation group lens and the second compensation group lens move towards the image space, and conversion from a small view field to a large view field is achieved. And the zoom lens, the first compensation group lens and the second compensation group lens do nonlinear motion to obtain a full-focal-length clear image. According to the invention, the design of a continuous zooming infrared optical system with a large target surface and a large relative aperture is realized, the movement of the cam is smoother and more stable, and the imaging quality in a temperature range of-40 DEG C to 65 DEG C is good.

Description

Technical Field

[0001] The invention relates to the field of infrared thermal imagers, and in particular to a continuous zoom long-wave infrared lens suitable for a large-target non-cooling detector. Background Art

[0002] Infrared thermal imagers use the thermal radiation of an object to obtain an image of the object. They can penetrate obstacles such as jungles and thick fog to find hidden targets, and have unique advantages in target detection and tracking. The concealment and passivity of the infrared detection system, as well as its excellent anti-interference ability, high sensitivity and high resolution, have made it widely used in military fields such as warning, tracking, reconnaissance and search. In particular, long-wave infrared thermal imagers have high permeability to various weather conditions, such as rain, snow, fog, haze, etc., and their transmission distance has been greatly increased, and their detection performance has been enhanced.

[0003] Compared with cooled infrared thermal imagers, uncooled infrared thermal imagers do not need to cool the detector, which greatly reduces the device cost, greatly shortens the startup time, is easy to use, and has a wider range of applications. However, the temperature resolution of uncooled detectors is low. In order to improve the temperature resolution and detection capability of the system, the uncooled infrared optical system is required to have a large relative aperture. Due to the limitation of aberrations, the design of optical systems with large relative apertures is more difficult. Fixed-focus infrared thermal imagers have a fixed focal length and can only observe targets in a certain field of view, which is not conducive to search and observation. Continuous zoom infrared thermal imagers achieve seamless connection within the large and small fields of view and keep the image surface stable and clear by continuously changing the relationship between the field of view and magnification of the optical system, thereby achieving continuous tracking of the target.

[0004] A large target surface can provide a larger field of view, which is more conducive to the thermal imager's search for targets in a wide range. However, for uncooled detectors, a large relative aperture is required. Breaking through the infrared optical design of large target surface, large relative aperture, and continuous zoom is a prerequisite for uncooled infrared detectors to fully exert their advantages, and it is a problem that technicians in this field urgently need to solve. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a continuous zoom long-wave infrared lens suitable for large-target uncooled detectors in view of the defects in the prior art.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] The present invention provides a continuous zoom long-wave infrared lens suitable for a large-surface non-cooled detector, which has seven lenses from the object side to the image side, and adopts a structural form of one-shot imaging, negative group magnification, and positive group compensation zoom; wherein:

[0008] A front fixed lens group, a variator lens, a first compensation lens group, a second compensation lens group, a first rear lens group, a second rear lens group, and a third rear lens group are sequentially arranged along the optical axis from the object side to the image side; during continuous zooming, the variator lens moves toward the object side, and the first compensation lens group and the second compensation lens group move toward the image side, so as to realize the transformation from a small field of view to a large field of view; the variator lens and the first compensation lens group and the second compensation lens group all perform nonlinear motion to obtain a clear image at the full focal length.

[0009] Furthermore, the front fixed lens group of the present invention is a positive meniscus lens with a convex surface facing the object, the zoom lens is a double concave negative lens, the first compensation lens group is a plano-convex lens with a convex surface facing the object, the second compensation lens group is a positive meniscus lens with a convex surface facing the image, the first rear lens group is a positive meniscus lens with a convex surface facing the object, the second rear lens group is a negative meniscus lens, and the third rear lens group is a positive meniscus lens with a convex surface facing the object.

[0010] Furthermore, the lenses in the lens of the present invention are all made of germanium and IRG206.

[0011] Furthermore, the second rear lens group of the present invention is a focusing lens, which moves axially forward and backward to achieve clear imaging of the system in high and low temperature environments.

[0012] Furthermore, the lens of the present invention adopts a mechanical compensation zooming method, the cam curve adopts a dual nonlinear design, and the zoom curve is smooth without inflection points within the full focal length range.

[0013] Furthermore, the double concave negative lens of the zoom lens of the present invention is concave toward the object, the plano-convex lens of the first compensation lens group is convex toward the object, the positive meniscus lens convex surface of the second compensation lens group, the negative meniscus lens convex surface of the second rear lens group, and the positive meniscus lens concave toward the image are all aspherical surfaces, and the aspherical surface equation is as follows:

[0014]

[0015] Among them, z is the vector height of the aspheric surface along the optical axis, c is the curvature, c=1 / R, R represents the radius of curvature of the lens, r is the radial coordinate, k is the quadratic curve constant, A is the fourth-order aspheric coefficient, B is the sixth-order aspheric coefficient, and D is the eighth-order aspheric coefficient.

[0016] Furthermore, the surface of the positive meniscus lens of the first rear lens group of the present invention facing the image side is an aspherical surface, and the diffraction surface formed by processing a continuous relief structure on the aspherical substrate satisfies the equation:

[0017]

[0018] Among them, HOR is the diffraction order, C1 and C2 are the diffraction surface coefficients, λ0 is the designed central wavelength, n is the lens refractive index, and n0 is the air refractive index.

[0019] The present invention provides a large-target-surface non-cooled continuous-zoom infrared optical system, which adopts the above-mentioned continuous-zoom long-wave infrared lens suitable for large-target-surface non-cooled detectors.

[0020] Furthermore, the focal length range of the lens of the optical system of the present invention is 30 mm to 150 mm, and the F number is 1.

[0021] Furthermore, the cam zoom curve of the optical system of the present invention is smooth without inflection points, and the lens is adapted to a high-resolution 1280×1024 long-wave uncooled detector to achieve a large observation range.

[0022] The beneficial effects produced by the present invention are:

[0023] 1. The present invention can realize the design of a large target surface, large relative aperture continuous zoom infrared optical system;

[0024] 2. The cam curve of the present invention adopts a double nonlinear design, which effectively reduces the pressure rise angle and makes the cam movement smoother and more stable;

[0025] 3. The present invention designs the focusing mirror to move to eliminate the thermal difference, so that the system has good imaging quality within the temperature range of -40°C to 65°C.

[0026] 4. The relative aperture of the lens is 1, and the large-surface long-wave uncooled detector with a resolution of 1280×1024 and a pixel size of 12um can achieve higher resolution, longer effective distance, and larger field of view, which is more conducive to the thermal imager's search for targets in a wide range.

[0027] 5. Infrared optical materials change greatly with temperature, which makes the infrared optical system sensitive to temperature. In order to compensate for the image plane movement caused by temperature changes, an axially movable positive meniscus second rear lens is used to compensate, to ensure that the system can have high image quality in the temperature range of -40℃ to 65℃. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0029] Figure 1 This is a schematic diagram of the uncooled continuous zoom infrared lens of the present invention;

[0030] In the figure, 1-front fixed lens group, 2-variable lens, 3-first compensation lens group, 4-second compensation lens group, 5-first rear lens group, 6-second rear lens group, 7-second rear lens group;

[0031] Figure 2 It is a two-dimensional schematic diagram of the uncooled continuous zoom infrared lens of the present invention in the telephoto state of 150mm;

[0032] Figure 3 It is a two-dimensional schematic diagram of the uncooled continuous zoom infrared lens of the present invention in the short-focus state of 30mm;

[0033] Figure 4 is the transfer function curve of the uncooled continuous zoom infrared lens of the present invention at a telephoto focal length of 42lp / mm;

[0034] Figure 5 The transfer function curve of the uncooled continuous zoom infrared lens of the present invention at a short focal length of 42lp / mm;

[0035] Figure 6 This is a point diagram of the uncooled continuous zoom infrared lens of the present invention at telephoto;

[0036] Figure 7 This is a point diagram of the uncooled continuous zoom infrared lens of the present invention at short focal length;

[0037] Figure 8 is the distortion curve of the uncooled continuous zoom infrared lens of the present invention at telephoto;

[0038] Fig. 9 is the distortion curve of the uncooled continuous zoom infrared lens of the present invention at short focal length;

[0039] Fig.10 This is the cam curve of the uncooled continuous zoom infrared lens of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0041] Example 1

[0042] like Figure 1 As shown, the embodiment of the present invention provides a continuous zoom long-wave infrared lens suitable for a large-surface uncooled detector, which has seven lenses from the object side to the image side, and adopts a structure of one-shot imaging, negative group zooming, and positive group compensation zooming; wherein:

[0043] A front fixed lens group 1, a variator lens 2, a first compensation lens group 3, a second compensation lens group 4, a first rear lens group 5, a second rear lens group 6, and a third rear lens group 7 are sequentially arranged along the optical axis from the object side to the image side; during continuous zooming, the variator lens 2 moves toward the object side, and the first compensation lens group 3 and the second compensation lens group 4 move toward the image side, so as to realize the transformation from a small field of view to a large field of view; the variator lens 2 and the first compensation lens group 3 and the second compensation lens group 4 all perform nonlinear motion to obtain a clear image at the full focal length.

[0044] The front fixed lens group 1 is a positive meniscus lens convex to the object side, the zoom lens 2 is a double concave negative lens, the first compensation lens group 3 is a plano-convex lens convex to the object side, the second compensation lens group 4 is a positive meniscus lens convex to the image side, the first rear lens group 5 is a positive meniscus lens convex to the object side, the second rear lens group 6 is a negative meniscus lens, and the third rear lens group 7 is a positive meniscus lens convex to the object side. The lenses in this lens are all made of germanium and IRG206.

[0045] The second rear lens group 6 is a focusing lens, which moves axially forward and backward to achieve clear imaging of the system in high and low temperature environments.

[0046] Example 2

[0047] like Figure 1 As shown, an embodiment of the present invention provides a large relative aperture, large target surface non-cooled infrared continuous zoom optical system, the direction close to the object space is the object side, the direction close to the image space is the image side, from the object side to the image side, the two sides of the lens are the incident surface and the exit surface respectively, including a first positive meniscus lens (fixed lens group 1), a double concave negative lens (variable lens 2), a plano-convex positive lens (first compensation lens group 3), a second positive meniscus lens (second compensation lens group 4), a third positive meniscus lens (first rear lens group 5), a negative meniscus lens (second rear lens group 6), and a fourth positive meniscus lens (third rear lens group 7) which are arranged on the same optical axis in sequence from the object side to the image side.

[0048] The focal lengths of the first positive meniscus lens, the biconcave negative lens, the plano-convex positive lens, the second positive meniscus lens, the third positive meniscus lens, the negative meniscus lens, and the fourth positive meniscus lens at a wavelength of 10 μm meet the following conditions:

[0049] 5.8≤f1 / f≤6.0, -2.2≤f2 / f≤-1.1, 4.5≤f3 / f≤4.8, 5.4≤f4 / f≤5.6, 4.7≤f5 / f≤4.9, -1.6≤f6 / f≤-1.4, 0.8≤f7 / f≤1.0;

[0050] Where f is the focal length of the optical system at short focus.

[0051] The double concave negative lens concave to the object side S3, the plano-convex positive lens convex to the object side S5, the double positive meniscus lens convex surface S8, the negative meniscus lens convex surface S12, and the positive meniscus lens concave to the image side S14 are all aspherical surfaces. The aspherical surface equations are as follows:

[0052]

[0053] Wherein, z is the vector height of the aspheric surface along the optical axis, c is the curvature, c=1 / R, R represents the radius of curvature of the lens, r is the radial coordinate, k is the quadratic constant, A is the fourth-order aspheric coefficient, B is the sixth-order aspheric coefficient, and D is the eighth-order aspheric coefficient;

[0054] The surface S8 of the third positive meniscus lens facing the image side is aspherical, and a diffraction surface formed by a continuous relief structure is machined on the S8 substrate. The diffraction surface can be machined on the S8 substrate using a diamond turning tool, and satisfies the equation:

[0055]

[0056] Among them, HOR is the diffraction order, C1 and C2 are the diffraction surface coefficients, λ0 is the designed central wavelength, n is the lens refractive index, and n0 is the air refractive index.

[0057] like Figure 2 , 3 As shown in the figure, the double concave negative lens is the zoom lens, and the plano-convex positive lens and the second positive meniscus lens together form a compensation lens group. The zoom lens and the compensation lens group change the focal length of the lens by axial movement. Combined with the cam curve Fig.10 , in the telephoto 150mm state, the distance between the zoom lens and the compensating lens group is 12.63mm, the zoom lens moves 48.13mm toward the object side, and the compensating lens group moves 54.20mm toward the image side, reaching the short focal length of 30mm. As shown by the cam curve, the zoom lens zoom lens performs nonlinear motion with a moving stroke of 48.13mm, and the compensating lens group performs nonlinear motion with a moving stroke of 54.20mm. In the entire stroke, the zoom curve is smooth without any sudden drop point.

[0058] Infrared optical materials change greatly with temperature, which makes the infrared optical system sensitive to temperature. In order to compensate for the image plane movement caused by temperature changes, an axially moving third positive meniscus lens is used to compensate, ensuring that the system can have high image quality within the temperature range of -40℃ to 65℃.

[0059] Example 3

[0060] The specific technical indicators of the zoom lens of the present invention are shown in Table 1.

[0061] Table 1 Lens technical indicators

[0062] focal length 30~150mm F-number 1 Detector resolution 1280×1024 Pixel size 12um Band 8~14um Operating temperature -40～60℃

[0063] Table 2 Optical parameters of the lens

[0064]

[0065] As shown in Table 2, detailed data of each lens when the focal length of the optical system of the present invention is 30 mm to 150 mm.

[0066] Table 3 Aspheric coefficients

[0067] Surface number k A B C S3 0 9.17676006e-08 -6.29469555e-13 -1.70303343e-15 S5 0 -9.16989501e-08 -2.22920171e-11 -7.09451431e-15 S8 0 -6.03083673e-08 -2.83770563e-11 -1.01462473e-14 S12 0 -1.12293832e-06 3.05905130e-10 -7.82536334e-14 S14 0 1.29328789e-06 -4.39200357e-10 1.78534707e-13

[0068] As shown in Table 3, the aspheric coefficients of the optical system of the present invention are: the double concave negative lens 2 has a concave surface S3 on the object side, the plano-convex positive lens 3 has a convex surface S5 on the object side, the second positive meniscus lens 4 has a convex surface S8, the negative meniscus lens 6 has a convex surface S12, and the positive meniscus lens 7 has a concave surface S14 on the image side.

[0069] Table 4 Diffraction aspheric coefficients

[0070] Surface number Diffraction order Structural wavelength C1 C2 S8 1 10000nm -5.9903248e-05 -5.1442307e-09

[0071] As shown in Table 4, the diffraction aspheric coefficient of the convex surface S8 of the second positive meniscus lens 4 of the optical system of the present invention;

[0072] After design simulation, Figure 4 , 5 The detector pixel size matched by the system is 12um, and the corresponding spatial cutoff frequency is 42lp / mm. At the cutoff frequency, the system transfer function is greater than 0.3 on the axis and greater than 0.15 off the axis. Figure 6 , 7 It can reflect the diffusion of the imaging light of the optical system. The smaller the RMS of the diffuse spot, the better the imaging quality. The RMS of the entire system in each field of view is within two pixels. Figure 8 , 9 The maximum distortion of long and short focal lengths is within 3%, which meets the design and use requirements.

[0073] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0074] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A continuous zoom long-wave infrared lens suitable for large-surface uncooled detectors, characterized in that: There are seven lenses from the object side to the image side, adopting a one-shot imaging and negative group zooming and positive group compensation zooming structure; among them: A front fixed lens group (1), a variable power lens (2), a first compensation lens group (3), a second compensation lens group (4), a first rear lens group (5), a second rear lens group (6), and a third rear lens group (7) are sequentially arranged along the optical axis from the object side to the image side; during continuous zooming, the variable power lens (2) moves toward the object side, and the first compensation lens group (3) and the second compensation lens group (4) move toward the image side, thereby realizing a transition from a small field of view to a large field of view; the variable power lens (2) and the first compensation lens group (3) and the second compensation lens group (4) all perform nonlinear motion, thereby obtaining a clear image at the full focal length.

2. The continuous zoom long-wave infrared lens suitable for large-target uncooled detectors according to claim 1, characterized in that: The front fixed lens group (1) is a positive meniscus lens with a convex surface facing the object, the variable power lens (2) is a double concave negative lens, the first compensation lens group (3) is a plano-convex lens with a convex surface facing the object, the second compensation lens group (4) is a positive meniscus lens with a convex surface facing the image, the first rear lens group (5) is a positive meniscus lens with a convex surface facing the object, the second rear lens group (6) is a negative meniscus lens, and the third rear lens group (7) is a positive meniscus lens with a convex surface facing the object.

3. The continuous zoom long-wave infrared lens suitable for large-target uncooled detectors according to claim 1, characterized in that: The lenses in this lens are made of materials Germanium and IRG206.

4. The continuous zoom long-wave infrared lens suitable for large-target uncooled detectors according to claim 1, characterized in that: The second rear lens group (6) is a focusing lens, which moves axially forward and backward to achieve clear imaging of the system in high and low temperature environments.

5. The continuous zoom long-wave infrared lens suitable for large-target uncooled detectors according to claim 1, characterized in that: The lens adopts mechanical compensation zoom, and the cam curve adopts a dual non-linear design. The zoom curve is smooth without inflection points within the full focal range.

6. The continuous zoom long-wave infrared lens suitable for large-target uncooled detectors according to claim 2, characterized in that: The double concave negative lens of the zoom lens (2) is concave toward the object, the plano-convex lens of the first compensation lens group (3) is convex toward the object, the convex surface of the positive meniscus lens of the second compensation lens group (4), the convex surface of the negative meniscus lens of the second rear lens group (6), and the positive meniscus lens of the third rear lens group (7) are all aspherical surfaces concave toward the image, and the aspherical surface equations are as follows: Among them, z is the vector height of the aspheric surface along the optical axis, c is the curvature, c=1 / R, R represents the radius of curvature of the lens, r is the radial coordinate, k is the quadratic curve constant, A is the fourth-order aspheric coefficient, B is the sixth-order aspheric coefficient, and D is the eighth-order aspheric coefficient.

7. The continuous zoom long-wave infrared lens suitable for large-target uncooled detectors according to claim 6, characterized in that: The positive meniscus lens of the first rear lens group (5) has an aspherical surface on the side facing the image side, and a diffraction surface formed by processing a continuous relief structure on the aspherical substrate satisfies the equation: Among them, HOR is the diffraction order, C1 and C2 are the diffraction surface coefficients, λ0 is the designed central wavelength, n is the lens refractive index, and n0 is the air refractive index.

8. A large-target uncooled continuous zoom infrared optical system, characterized in that: A continuous zoom long-wave infrared lens suitable for a large-target uncooled detector as described in any one of claims 1 to 7 is used.

9. The large-target-area uncooled continuous-zoom infrared optical system according to claim 8, characterized in that: The lens focal length range of this optical system is 30mm to 150mm, and the F number is 1.

10. The large-target-area uncooled continuous-zoom infrared optical system according to claim 8, characterized in that: The cam zoom curve of the optical system is smooth without inflection points, and the lens is adapted to the high-resolution 1280×1024 long-wave uncooled detector to achieve a large observation range.

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