A continuous zoom long-wave infrared lens suitable for large target surface uncooled detector

Abstract

The application discloses a continuous zoom long-wave infrared lens suitable for a large target surface uncooled detector, which is provided with seven lenses from an object side to an image side, adopts a structure form of one-time imaging and negative group variable magnification and positive group compensation zooming, and is sequentially provided with a front fixed group lens, a variable magnification 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 along an optical axis from the object side to the image side; during continuous zooming, the variable magnification lens moves towards the object side, the first compensation group lens and the second compensation group lens move towards the image side, and the change from a small field of view to a large field of view is realized; the variable magnification lens and the first compensation group lens and the second compensation group lens are all in non-linear motion, and a clear image in a full focal length section is obtained. The application realizes the design of a large target surface, large relative aperture continuous zoom infrared optical system, the cam motion is more smooth and stable, and the imaging quality is good in a temperature range of-40 DEG C to 65 DEG C.

Description

Technical Field

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

[0002] Infrared thermal imagers use an object's own thermal radiation to capture its image. They can penetrate obstacles like jungle and dense fog to detect hidden targets, offering unique advantages in target detection and tracking. The infrared detection system's concealment and passivity, along with its excellent anti-interference capabilities, high sensitivity, and high resolution, have led to its widespread application in military fields such as surveillance, tracking, reconnaissance, and search. Long-wave infrared thermal imagers, in particular, offer high transparency in all weather conditions, including rain, snow, fog, and haze, significantly increasing their transmission distance and enhancing their detection capabilities.

[0003] Compared to cooled infrared thermal imagers, uncooled infrared thermal imagers do not require cooling of the detector, which greatly reduces device costs, greatly shortens startup time, is convenient 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, which is limited by aberrations, and the design of optical systems with large relative apertures increases the difficulty. Fixed-focus infrared thermal imagers have a fixed focal length and can only observe targets in a certain field of view area, which is not conducive to search and observation. Continuous zoom infrared thermal imagers, by continuously changing the relationship between the field of view and magnification of the optical system, achieve seamless connection between large and small fields of view and maintain a stable and clear image plane, thereby achieving continuous tracking of the target.

[0004] A large image sensor provides a wider field of view, facilitating the thermal imager's ability to search for targets over a wide range. However, for uncooled detectors, this requires a large relative aperture. Breakthroughs in infrared optical design, combining large image sensors with large relative apertures and continuous zoom, are prerequisites for uncooled infrared detectors to fully realize their advantages and represent a pressing challenge for those skilled in the art. 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 large-surface uncooled detectors. The lens comprises seven lenses from the object side to the image side, and adopts a structure of one-shot imaging, negative-group zooming, and positive-group compensating zooming.

[0008] A front fixed lens group, a variator lens, a first compensating lens group, a second compensating lens group, a first rear lens group, a second rear lens group, and a third rear lens group are arranged in sequence 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 compensating lens group and the second compensating lens group move toward the image side, thereby realizing a transition from a small field of view to a large field of view. The variator lens and the first compensating lens group and the second compensating lens group all perform nonlinear motion to obtain a clear image at all focal lengths.

[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 biconcave 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 that moves axially back and forth 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 zoom method, and the cam curve adopts a dual nonlinear design, so that 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 has a concave surface facing the object, the plano-convex lens of the first compensation lens group has a convex surface facing the object, the convex surface of the positive meniscus lens of the second compensation lens group, the convex surface of the negative meniscus lens of the second rear lens group, and the concave surface of the positive meniscus lens of the third rear lens group are all aspherical surfaces. The aspherical surface equations are as follows:

[0014]

[0015] Wherein, z is the sagittal 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 positive meniscus lens of the first rear lens group of the present invention has an aspherical surface facing the image side, and a diffraction surface formed by processing a continuous relief structure on the aspherical substrate satisfies the equation:

[0017]

[0018] Where HOR is the diffraction order, C1 and C2 are the diffraction surface coefficients, λ0 is the design center wavelength, n is the lens refractive index, and n0 is the air refractive index.

[0019] The present invention provides a large-target-area uncooled continuous-zoom infrared optical system, which adopts the above-mentioned continuous-zoom long-wave infrared lens suitable for large-target-area uncooled 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 continuous zoom infrared optical system with a large target area and large relative aperture;

[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 thermal differences, 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 when used with a large-surface, long-wave, uncooled detector with a resolution of 1280×1024 and a pixel size of 12 μm, it can achieve higher resolution, longer effective distance, and larger field of view, making it more conducive to the thermal imager's search for targets over a wide range.

[0027] 5. Infrared optical materials change greatly with temperature, making 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, ensuring that the system can maintain high image quality within 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-zoom 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 This 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 This 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 : This is the transfer function curve of the uncooled continuous zoom infrared lens of the present invention at a telephoto focal length of 42 lp / 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 42 lp / mm;

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

[0036] Figure 7 This is the spot diagram of the uncooled continuous zoom infrared lens of the present invention at short focus;

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

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

[0039] Figure 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 solutions and advantages of the present invention more clearly understood, 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 used to explain the present invention and are not intended to limit the present invention.

[0041] Example 1

[0042] like Figure 1 As shown, an embodiment of the present invention provides a continuous zoom long-wave infrared lens suitable for large-area uncooled detectors. A total of seven lenses are arranged from the object side to the image side, and a structure of one-shot imaging, negative group magnification, and positive group compensation zoom is adopted; wherein:

[0043] A front fixed lens group 1, a variator lens 2, a first compensating lens group 3, a second compensating lens group 4, a first rear lens group 5, a second rear lens group 6, and a third rear lens group 7 are arranged in sequence 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 compensating lens group 3 and the second compensating 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 variator lens 2 and the first compensating lens group 3 and the second compensating lens group 4 all perform nonlinear motion to obtain a clear image at all focal lengths.

[0044] The front fixed lens group 1 is a positive meniscus lens convex to the object side, the zoom lens 2 is a biconcave negative lens, the first compensating lens group 3 is a plano-convex lens convex to the object side, the second compensating 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. All lenses in this lens are made of germanium and IRG206.

[0045] The second rear lens group 6 is a focusing lens that moves axially back and forth 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 uncooled 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 magnification 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) arranged in sequence on the same optical axis 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's concave object-side surface S3, the plano-convex positive lens's convex object-side surface S5, the two positive meniscus lens's convex surface S8, the negative meniscus lens's convex surface S12, and the positive meniscus lens's concave image-side surface S14 are all aspherical surfaces. The aspheric surface equations are as follows:

[0052]

[0053] Where z is the aspheric height 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] Where HOR is the diffraction order, C1 and C2 are the diffraction surface coefficients, λ0 is the design center wavelength, n is the lens refractive index, and n0 is the air refractive index.

[0057] like Figure 2 、 3 As shown, the double concave negative lens is the zoom lens, and the plano-convex positive lens and the second positive meniscus lens together form the 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 Figure 10 At 150mm telephoto, 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, achieving a 30mm short focal length. As shown by the cam curve, the zoom lens's zoom lens undergoes nonlinear motion with a travel of 48.13mm, and the compensating lens group undergoes nonlinear motion with a travel of 54.20mm. Throughout the entire travel range, the zoom curve is smooth, with no sudden drops.

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

[0059] Example 3

[0060] The specific technical specifications 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] Table 2 shows the 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 coefficients of the convex surface S8 of the second positive meniscus lens 4 of the optical system of the present invention are:

[0072] After design simulation, such as Figure 4 、 5 The detector pixel size matched to this 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 diffusion 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 usage 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 this application.

[0074] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such 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-area uncooled detectors, characterized in that: There are seven lenses from the object side to the image side, adopting a structure of single-shot imaging, negative group zooming, and positive group compensation zooming; among them: A front fixed lens group (1), a zoom 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 zoom 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 zoom 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 all focal lengths.

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 side, the zoom 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 side, the second compensation lens group (4) is a positive meniscus lens with a convex surface facing the image side, the first rear lens group (5) is a positive meniscus lens with a convex surface facing 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 with a convex surface facing the object side.

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 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 that 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 nonlinear design. The zoom curve is smooth and has no inflection point within the entire focal length 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 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. The aspherical surface equations are as follows: Where z is the sagittal 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 second compensation lens group (4) 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: Where HOR is the diffraction order, C1 and C2 are the diffraction surface coefficients, λ0 is the design center 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.

Images