Infrared continuous zoom lens and infrared thermal imaging system

Abstract

The present application discloses an infrared continuous zoom lens and an infrared thermal imaging system, which include a front fixed group, a zoom group, a compensation group, and a rear fixed group, which are arranged in sequence along the optical axis from the object side to the image plane; the front fixed group includes a first lens with positive optical power and a second lens with positive optical power, the zoom group includes a third lens with negative optical power, the compensation group includes a fourth lens with negative optical power and a fifth lens with positive optical power, and the rear fixed group includes a sixth lens with positive optical power, a seventh lens with negative optical power, and an eighth lens with positive optical power; wherein the number of lenses with optical power in the infrared continuous zoom lens is eight; the position of the sixth lens of the front fixed group and the rear fixed group is fixed relative to the image plane; and the distances of the seventh lens and the eighth lens of the zoom group, the compensation group, and the rear fixed group relative to the front fixed group on the optical axis are adjustable.

Description

Technical Field

[0001] This application relates to the field of optical devices, and particularly to an eight-piece infrared continuous zoom lens and an infrared thermal imaging system. Background Art

[0002] With the continuous development of infrared thermal imaging systems, their costs have been continuously reduced, making the applications of infrared thermal imaging systems in the civilian field increasingly emphasized. Infrared thermal imaging systems have the advantages of strong anti-interference ability, intuitive images, easy observation, etc., and can be used in extreme environments such as heavy rain, fog, rain, and snow, which further increases the demand for the use of infrared thermal imaging systems.

[0003] Fixed-focus infrared thermal imaging systems have certain limitations and cannot well complete the work tasks in complex scene areas. Zoom infrared thermal imaging systems have the functions of large-field-of-view search and small-field-of-view precise positioning. If zoom infrared thermal imaging systems can be fully applied in complex scene areas, they will be well promoted in civilian fields such as airport monitoring, forest fire prevention, and rail transit, and have broad application prospects. Summary of the Invention

[0004] This application provides an infrared continuous zoom lens and an infrared thermal imaging system that can at least solve or partially solve at least one problem or other problems existing in the prior art.

[0005] One aspect of this application provides such an infrared continuous zoom lens, which includes a front fixed group, a zoom group, a compensation group, and a rear fixed group arranged in sequence from the object side to the image plane along the optical axis; the front fixed group includes a first lens with a positive optical power and a second lens with a positive optical power, the zoom group includes a third lens with a negative optical power, the compensation group includes a fourth lens with a negative optical power and a fifth lens with a positive optical power, and the rear fixed group includes a sixth lens with a positive optical power, a seventh lens with a negative optical power, and an eighth lens with a positive optical power;

[0006] Among them, the number of lenses with optical power in the infrared continuous zoom lens is eight; the positions of the sixth lens in the front fixed group and the rear fixed group relative to the image plane are fixed; and the distances of the seventh and eighth lenses in the zoom group, the compensation group, and the rear fixed group relative to the front fixed group on the optical axis are adjustable.

[0007] According to an exemplary embodiment of this application, the front fixed group satisfies: 1 < R2 / Rl < 2; where, Rl is the curvature radius of the object side surface of the first lens, and R2 is the curvature radius of the image side surface of the first lens.

[0008] According to an exemplary embodiment of the present application, the infrared continuous zoom lens satisfies: -2 < ft×(n - 1) / (FNO×R1) < -1; and 0.01 < BFLt / ft < 0.04; where ft is the focal length of the infrared continuous zoom lens in the telephoto state, n is the refractive index at the center wavelength of the material of the first lens, FNO is the F-number of the infrared continuous zoom lens, R1 is the curvature radius of the object side surface of the first lens, and BFLt is the back focal length of the infrared continuous zoom lens in the telephoto state.

[0009] According to an exemplary embodiment of the present application, the infrared continuous zoom lens satisfies: 0.1 < |f1 / ft| < 1; 0.3 < |f2 / ft| < 1.2; 0.01 < |f3 / ft| < 0.5; 2.5 < |f4 / ft| < 5; 0.02 < |f5 / ft| < 0.3; 0.05 < |f6 / ft| < 0.5; 0.01 < |f7 / ft| < 0.1; and 0.01 < |f8 / ft| < 0.13; where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, f7 is the effective focal length of the seventh lens, f8 is the effective focal length of the eighth lens, and ft is the focal length of the infrared continuous zoom lens in the telephoto state.

[0010] According to an exemplary embodiment of the present application, the material of the first lens is silicon material, and the refractive indices of the materials of the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the eighth lens are all within the range of 2.3 to 4.5.

[0011] According to an exemplary embodiment of the present application, the first lens is a meniscus lens with the convex surface facing the object side, the second lens is a meniscus lens with the convex surface facing the object side, the third lens is a biconcave lens, the fourth lens is a meniscus lens with the convex surface facing the object side, the fifth lens is a biconvex lens, the sixth lens is a meniscus lens with the convex surface facing the object side, the seventh lens is a meniscus lens with the concave surface facing the object side, and the eighth lens is a biconvex lens.

[0012] According to an exemplary embodiment of the present application, the object side surface of the third lens, the image side surface of the sixth lens, and the object side surface of the seventh lens are aspherical surfaces, and the object side surfaces of the fifth lens and the eighth lens are binary surfaces.

[0013] According to an exemplary embodiment of the present application, the aspherical surface satisfies the following equation:

[0014]

[0015] Where Z is the axial sagittal height in the Z direction of the aspheric surface, r is the distance from the point on the aspheric surface to the optical axis, c is the curvature of the fitted sphere, which is the inverse of the curvature radius, k is the cone coefficient, and A, B, C, and D are the coefficients of the 4th, 6th, 8th, and 10th order terms of the aspheric polynomial.

[0016] According to an exemplary embodiment of the present application, the binary surface satisfies the following equation:

[0017]

[0018] Among them, λ0 is the central wavelength during design, n0 is the refractive index corresponding to the central wavelength of the material, M is the diffraction order, N is the order of the polynomial coefficients in the series, A i is the diffraction surface phase coefficient, ρ is the normalized radial aperture coordinate, ρ = r / r1, r1 is the normalized radius of the diffraction surface.

[0019] According to an exemplary embodiment of the present application, the zoom group and the compensation group perform nonlinear motion along opposite directions or opposite directions on the optical axis to switch the infrared continuous zoom lens between a short focus state, a medium focus state, and a long focus state.

[0020] According to an exemplary embodiment of the present application, the zoom ratio of the infrared continuous zoom lens is 12X.

[0021] According to an exemplary embodiment of the present application, the infrared continuous zoom lens has an operating band of 3.7 μm to 4.8 μm, a zoom range of f80 mm to f950 mm, an F number of 4, and a horizontal field of view of 0.6° to 6.9°.

[0022] Another aspect of the present application provides an infrared thermal imaging system, which includes the above-mentioned infrared continuous zoom lens and a medium-wave cooled detector, wherein the medium-wave cooled detector is located on the image plane of the infrared continuous zoom lens.

[0023] The infrared continuous zoom lens provided in this application is configured as an eight-lens structure. By moving the seventh and eighth lenses in the zoom group, compensation group, and rear fixed group, it achieves a 12X continuous zoom function for the optical system. This effectively shortens the system length, controls the number of lenses in the optical system, significantly reduces costs, and significantly improves the system's transmittance. While achieving zoom, the infrared continuous zoom lens can also effectively compensate for aberrations caused by the zooming process and temperature changes, thereby ensuring that the infrared continuous zoom lens has good imaging effects at different focal lengths and temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other features, objects and advantages of the present application will become more apparent upon reading the detailed description of non-limiting embodiments made with reference to the following drawings:

[0025] Figure 1 shows a schematic structural diagram of an infrared thermal imaging system according to the present application;

[0026] Figure 2 Shown Figure 1 Schematic diagram of the movement of the infrared continuous zoom lens shown;

[0027] Figures 3 to 5 The figure shows the MTF diagram, the diffusion spot and the field curvature distortion diagram of the infrared continuous zoom lens according to Example 1 of the present application in the short-focus state;

[0028] Figures 6 to 8 shows the MTF diagram, blurring speckle, and field curvature distortion diagram of the infrared continuous zoom lens according to Example 1 of the present application in the mid-focus state; and

[0029] Figures 9 to 11 The diagram shows the MTF diagram, the blurring spot, and the field curvature distortion diagram of the infrared continuous zoom lens according to Example 1 of the present application in the telephoto state. DETAILED DESCRIPTION

[0030] In order to better understand the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely descriptions of exemplary embodiments of the present application and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements.

[0031] It should be noted that in this specification, the terms "first," "second," "third," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, the first lens discussed below could also be referred to as the second lens or the third lens without departing from the teachings of this application.

[0032] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical and aspherical surfaces shown in the drawings are provided by way of example. That is, the shapes of the spherical and aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0033] In this article, the paraxial region refers to the area near the optical axis. If a lens surface is convex and the location of the convex surface is undefined, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the location of the concave surface is undefined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the subject is called the object-side surface of the lens, and the surface of each lens closest to the imaging plane is called the image-side surface of the lens.

[0034] It should also be understood that the terms "comprise," "including," "having," "include," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when describing embodiments of the present application, the term "may" is used to mean "one or more embodiments of the present application." Furthermore, the term "exemplary" is intended to refer to an example or illustration.

[0035] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0036] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] The features, principles and other aspects of the present application are described in detail below.

[0038] Figure 1 FIG2 shows a schematic structural diagram of an infrared thermal imaging system according to an exemplary embodiment of the present application. Figure 1 The infrared thermal imaging system includes an infrared continuous zoom lens 100, which includes a front fixed group 10, a zoom group 20, a compensation group 30 and a rear fixed group 40 along the optical axis from the object side to the image plane.

[0039] The front fixed group 10 may include, for example, a first lens 11 having positive refractive power and a second lens 12 having positive refractive power, and the position of the front fixed group 10 relative to the image plane is fixed. The front fixed group 10 is used to converge light.

[0040] The zoom group 20 may, for example, include a third lens element 21 having negative optical power. The zoom group 20 is movable along the optical axis relative to the front fixed group 10. Specifically, the distance of the zoom group 20 relative to the front fixed group 10 on the optical axis is adjustable. By adjusting the distance between the zoom group 20 and the front fixed group 10 on the optical axis, the focal length of the infrared continuous zoom lens 100 can be changed. During the zooming process of the infrared continuous zoom lens 100, the infrared continuous zoom lens 100 can be divided into three states: short focus, medium focus, and long focus, depending on the focal length.

[0041] The compensation group 30 may, for example, include a fourth lens element 31 having negative optical power and a fifth lens element 32 having positive optical power. The compensation group 30 is movable along the optical axis relative to the front fixed group 10. In other words, the distance of the compensation group 30 relative to the front fixed group 10 on the optical axis is adjustable. By adjusting the distance between the compensation group 30 and the front fixed group 10 on the optical axis, image plane movement during zooming of the infrared continuous zoom lens 100 can be compensated, effectively compensating for aberrations caused by the movement of the variator group 20.

[0042] The rear fixed group 40 may, for example, include a sixth lens 41 having positive optical power, a seventh lens 42 having negative optical power, and an eighth lens 43 having positive optical power. The sixth lens 41 is fixed relative to the image plane, while the seventh lens 42 and the eighth lens 43 are movable along the optical axis relative to the front fixed group 10. That is, the distance between the seventh lens 42 and the eighth lens 43 on the optical axis relative to the front fixed group 10 is adjustable. By adjusting the distance between the seventh lens 42 and the eighth lens 43 and the front fixed group 10 on the optical axis, the focal length of the infrared continuous zoom lens 100 can be fine-tuned to compensate for image plane position shifts at different object distances and temperatures.

[0043] The infrared continuous zoom lens 100 provided herein may be composed of eight lenses having optical focal lengths. By adjusting the distances of the zoom group 20, the compensation group 30, and the seventh and eighth lenses 42 and 43 of the rear fixed group 40 relative to the front fixed group 10 on the optical axis, the infrared continuous zoom lens 100 can be switched between short-focus, medium-focus, and long-focus states. Furthermore, while achieving zooming, the infrared continuous zoom lens 100 effectively compensates for aberrations caused by the zooming process and temperature changes. This ensures that the infrared continuous zoom lens 100 achieves good imaging results at different focal lengths and temperatures, expanding its application in complex scenes.

[0044] Figure 2 Shown Figure 1 The schematic diagram of the movement of the infrared continuous zoom lens 100 is shown. Figure 2The zoom group 20 and the compensation group 30 perform nonlinear motion along the optical axis in opposite directions or in opposite directions, so that the infrared continuous zoom lens 100 switches between a short focus state, a medium focus state, and a long focus state. When the zoom group 20 and the compensation group 30 perform nonlinear motion along the optical axis in opposite directions, the focal length of the infrared continuous zoom lens 100 increases, for example, the infrared continuous zoom lens 100 switches from a short focus state to a medium focus state, or from a medium focus state to a long focus state. When the zoom group 20 and the compensation group 30 perform nonlinear motion along the optical axis in opposite directions, the focal length of the infrared continuous zoom lens 100 decreases, for example, the infrared continuous zoom lens 100 switches from a long focus state to a medium focus state, or from a medium focus state to a short focus state. It should be noted that the fourth lens 31 and the fifth lens 32 in the compensation group 30 move synchronously.

[0045] Taking the increase in focal length of the infrared continuous zoom lens 100 as an example, the movement of the zoom group 20 and the compensation group 30 is explained:

[0046] When the zoom group 20 moves rightward on the optical axis, the compensating group 30 must correspondingly move leftward. This effectively increases the distance between the zoom group 20 and the front fixed group 10, while simultaneously decreasing the distance between the compensating group 30 and the zoom group 20. It is understood that when the zoom group 20 moves rightward, the divergence of the light beam emitted by the front fixed group 10 by the zoom group 20 is relatively delayed. By moving the compensating group 30 a corresponding distance to the left, the time it takes for the compensating group 30 to converge the light beam is altered, thereby changing the overall convergence effect of the lens, thereby increasing the focal length of the infrared continuous zoom lens 100.

[0047] The movement of the zoom group 20 and the compensation group 30 is described by taking the focal length reduction of the infrared continuous zoom lens 100 as an example:

[0048] When the zoom group 20 moves leftward on the optical axis, the compensation group 30 must correspondingly move rightward. This effectively shortens the distance between the zoom group 20 and the front fixed group 10, while simultaneously increasing the distance between the compensation group 30 and the zoom group 20. It is understood that when the zoom group 20 moves leftward, the divergence of the light beam emitted by the front fixed group 10 by the zoom group 20 is relatively advanced. By moving the compensation group 30 rightward by a corresponding distance, the timing of the compensation group 30's convergence of the light beams can be altered, thereby changing the overall convergence effect of the lens, thereby reducing the focal length of the infrared continuous zoom lens 100.

[0049] It should be noted that, in actual use, the movement of the zoom group 20 and the compensation group 30 in the infrared continuous zoom lens 100 needs to be driven synchronously according to a predetermined positional relationship to ensure that the image of the infrared continuous zoom lens 100 is clear during the zooming process.

[0050] In an exemplary embodiment, the front fixed group 10, the zoom group 20, the compensating group 30, and the rear fixed group 40 are disposed within a lens barrel. The sixth lens 41 in the front fixed group 10 and the rear fixed group 40 is fixed within the lens barrel, while the seventh lens 42 and the eighth lens 43 in the zoom group 20, the compensating group 30, and the rear fixed group 40 are capable of reciprocating along the optical axis within the lens barrel to change focal length. Specifically, five cam grooves are provided on the interior of the lens barrel, corresponding to the zoom group 20, the fourth lens 31, the fifth lens 32, the seventh lens 42, and the eighth lens 43, respectively, to control the movement of the corresponding lenses.

[0051] In an exemplary embodiment, the first lens 11 may be, for example, a meniscus lens with a convex surface facing the object side, the second lens 12 may be, for example, a meniscus lens with a convex surface facing the object side, the third lens 21 may be, for example, a biconcave lens, the fourth lens 31 may be, for example, a meniscus lens with a convex surface facing the object side, the fifth lens 32 may be, for example, a biconvex lens, the sixth lens 41 may be, for example, a meniscus lens with a convex surface facing the object side, the seventh lens 42 may be, for example, a meniscus lens with a concave surface facing the object side, and the eighth lens 43 may be, for example, a biconvex lens.

[0052] In an exemplary embodiment, the object-side surface of the third lens 21, the image-side surface of the sixth lens 41, and the object-side surface of the seventh lens 42 are aspherical surfaces, while the object-side surface of the fifth lens 32 and the object-side surface of the eighth lens 43 are binary surfaces (i.e., diffractive surfaces). The infrared continuous zoom lens 100 provided herein utilizes a combination of aspherical and diffractive surfaces to effectively correct chromatic aberration, compensate for chromatic aberration caused by temperature changes, and improve the imaging quality of the infrared continuous zoom lens 100.

[0053] The above-mentioned aspheric surface is an even-order aspheric surface, which satisfies the following equation:

[0054]

[0055] Where Z is the axial sagittal height in the Z direction of the aspheric surface, r is the distance from a point on the aspheric surface to the optical axis, c is the curvature of the fitted sphere, numerically the inverse of the radius of curvature, k is the conic coefficient, and A, B, C, and D are the coefficients of the 4th, 6th, 8th, and 10th order terms of the aspheric surface polynomial. Through the above arrangement, the object-side surface of the third lens 21, the image-side surface of the sixth lens 41, and the object-side surface of the seventh lens 42 can be configured as aspheric surfaces, which facilitates correction of various aberrations in the optical system and further ensures clear imaging by the infrared continuous zoom lens 100.

[0056] The above two-dimensional surface satisfies the following equation:

[0057]

[0058] Among them, λ0 is the central wavelength at the time of design, and n0 is the refractive index corresponding to the central wavelength of the material. M is the diffraction order, N is the order of the polynomial coefficients in the series, A i is the phase coefficient of the diffraction surface, ρ is the normalized radial aperture coordinate, ρ = r / r1, and r1 is the normalized radius of the diffraction surface. Through the above settings, the object side surfaces of the fifth lens 32 and the eighth lens 43 can be set as diffraction surfaces, which plays a role in compensating for the thermal difference and further ensures that the infrared continuous zoom lens 100 can achieve clear imaging.

[0059] In an exemplary embodiment, the material of the first lens 11 is a silicon material, and the refractive indices of the materials of the second lens 12, the third lens 21, the fourth lens 31, the fifth lens 32, the sixth lens 41, the seventh lens 42, and the eighth lens 43 are all within the range of 2.3 to 4.5.

[0060] In an exemplary embodiment, the front fixed group 10 satisfies the following condition: 1 < R2 / R1 < 2; where R1 is the curvature radius of the object side surface of the first lens 11, and R2 is the curvature radius of the image side surface of the first lens 11. By controlling the curvature radii of the object side surface and the image side surface of the first lens 11, the first lens 11 can have a specific meniscus shape, which can provide an appropriate and stable light convergence effect while ensuring its positive optical power, and can cooperate with other lenses to achieve the corresponding optical power combination to support the moving zoom of the zoom group 20 and the compensation group 30.

[0061] In an exemplary embodiment, the infrared continuous zoom lens 100 satisfies: 0.1 < |f1 / ft| < 1; 0.3 < |f2 / ft| < 1.2; 0.01 < |f3 / ft| < 0.5; 2.5 < |f4 / ft| < 5; 0.02 < |f5 / ft| < 0.3; 0.05 < |f6 / ft| < 0.5; 0.01 < |f7 / ft| < 0.1; and 0.01 < |f8 / ft| < 0.13; where f1 is the effective focal length of the first lens 11, f2 is the effective focal length of the second lens 12, f3 is the effective focal length of the third lens 21, f4 is the effective focal length of the fourth lens 31, f5 is the effective focal length of the fifth lens 32, f6 is the effective focal length of the sixth lens 41, f7 is the effective focal length of the seventh lens 42, f8 is the effective focal length of the eighth lens 43, and ft is the focal length of the infrared continuous zoom lens 100 in the long focal state. By controlling the mutual relationship between the effective focal lengths of the first lens 11 to the eighth lens 43 and the focal length of the infrared continuous zoom lens 100 in the long focal state, the functions of each lens in its respective group can be reasonably defined, and the mutual cooperation of each lens can be ensured, so that the infrared continuous zoom lens 100 can achieve zooming and clear imaging.

[0062] In an exemplary embodiment, the infrared continuous zoom lens 100 satisfies: -2 < ft×(n - 1) / (FNO×R1) < -1; and 0.01 < BFLt / ft < 0.04; where ft is the focal length of the infrared continuous zoom lens 100 in the telephoto state, n is the refractive index at the center wavelength of the material of the first lens 11, FNO is the F-number of the infrared continuous zoom lens 100, R1 is the curvature radius of the object side surface of the first lens 11, and BFLt is the back focal length of the infrared continuous zoom lens 100 in the telephoto state.

[0063] In an exemplary embodiment, the working wavelength band of the infrared continuous zoom lens 100 can be set to 3.7 μm to 4.8 μm, and the zoom range is f80 mm to f950 mm, the zoom ratio is 12X, the horizontal field angle is 0.6° to 6.9°, and the F-number is 4.

[0064] Compared with the existing zoom lenses, the infrared continuous zoom lens 100 provided in this application adopts the method of moving the seventh lens 42 and the eighth lens 43 in the zoom group 20, the compensation group 30 and the rear fixed group 40 to achieve the continuous zoom function of the 12X optical system. Moreover, through this zoom method, the system length is effectively shortened, the number of lenses in the optical system is controlled, and the cost is greatly reduced. The infrared continuous zoom lens 100 provided in this application adopts an 8P optical structure and a method of using aspherical and diffractive surfaces in combination to achieve 12X continuous zoom. It can not only effectively correct chromatic aberration, has the function of actively eliminating thermal aberration, and realizes stable imaging of the lens in a wide temperature range from -40° to +60°, meeting the requirement that the lens can be used in an environment with large temperature changes, but also can well improve the transmittance of the system by reducing the number of lenses.

[0065] Based on the same concept, this application also provides an infrared thermal imaging system. Continuing to refer to Figure 1 , this infrared thermal imaging system includes the above-mentioned infrared continuous zoom lens 100, and also includes a mid-wave refrigeration detector 200 located on the image plane 50 of the infrared continuous zoom lens 100. The working wavelength band of the infrared continuous zoom lens 100 is 3.7 μm to 4.8 μm, the zoom ratio is 12X, the zoom range is f80 mm to f950 mm, the F-number is 4, and the horizontal field angle is 0.6° to 6.9°. It can be adapted to the mid-wave refrigeration detector 200 with a specification of 640×512_15μm. Moreover, since this infrared thermal imaging system includes the above-mentioned infrared continuous zoom lens 100, it has the same or similar technical effects as those of the above-mentioned infrared continuous zoom lens 100, which will not be elaborated here.

[0066] The following further describes specific embodiments of the infrared continuous zoom lens 100 applicable to the above embodiments with reference to the accompanying drawings.

[0067] Example 1

[0068] Table 1 shows basic parameters of the infrared continuous zoom lens 100 of Example 1, wherein the units of curvature radius, spacing and aperture are all millimeters (mm).

[0069]

[0070] Table 1

[0071] The surface numbers in Table 1 are numbered according to the order of the surfaces of each lens, where "1" represents the object side of the first lens 11, "2" represents the image side of the first lens 11, and so on. The radius of curvature represents the degree of curvature of the lens surface, where "infinity" means that the radius of curvature is infinite, indicating that the surface is a plane. The spacing represents the central axial distance from the current surface to the next surface. It can be understood that since the zoom group 20 and the compensation group 30 need to move back and forth along the optical axis, the spacing corresponding to the zoom group 20 and the compensation group 30 is a range value. The refractive index of the material represents the ability to deflect light. The space represents that the current position is air, and the refractive index is 1.

[0072] In this embodiment, the conic coefficients of the aspheric surface and the binary surface and the order coefficients of the aspheric polynomial are shown in Table 2.

[0073] Surface number Face shape k A B C D 5 Aspheric 0 1.35E-07 3.71E-12 -1.12E-14 3.75E-18 9 Two-dimensional surface 0 -1.25E-07 -1.20E-11 1.08E-14 -2.63E-18 12 Aspheric 0 2.69E-07 9.54E-10 -2.21E-12 8.67E-15 13 Aspheric 0 2.35E-05 -5.46E-08 4.02E-09 -3.97E-11 15 Two-dimensional surface 0 -1.58E-05 8.49E-09 -8.06E-11 2.11E-13

[0074] Table 2 In this embodiment, the normalized radius and phase coefficient of the binary plane are shown in Table 3.

[0075] Surface number Face shape naturalized radius <![CDATA[A1]]> <![CDATA[A2]]> 9 Two-dimensional surface 36 -159.23 7.52 15 Two-dimensional surface 12.5 -94.15 6.71

[0076] Table 3

[0077] The infrared continuous zoom lens 100 provided in Example 1 can have a short focus state, a medium focus state, and a long focus state, wherein: Figures 3 to 5 It is the MTF diagram, the diffusion spot and the field curvature distortion diagram of the infrared continuous zoom lens 100 in the short focus state. Figures 6 to 8 The MTF diagram, the diffusion spot and the field curvature distortion diagram of the infrared continuous zoom lens 100 in the mid-focus state are shown below. Figures 9 to 11 The following are the MTF graphs, blurring speckles, and field curvature distortion graphs of the infrared continuous zoom lens 100 in the telephoto state. Figure 3 、 Figure 6 and Figure 9 At different focal lengths, the transfer function of the infrared continuous zoom lens 100 is around 0.10 or above, which means that the infrared continuous zoom lens 100 can achieve good resolution in both the central field of view and the edge field of view, and can meet the resolution requirements of a large field of view and a large target area. Figure 4 、 Figure 7 and Figure 10 , under different focal length states, the diffuse spot radius of the infrared continuous zoom lens 100 at different field of view positions changes slightly, which means that the aberration of the infrared continuous zoom lens 100 at different field of view positions is small. Figure 5 、 Figure 8 and Figure 11 At different focal lengths, the infrared continuous zoom lens 100 exhibits maximum distortion within ±1%, and the resulting meridional and sagittal curvatures for light of different wavelengths range from ±0.50 mm. This indicates that the infrared continuous zoom lens 100 achieves minimal distortion and field curvature at all focal lengths. In summary, the infrared continuous zoom lens 100 provided in Example 1 is capable of correcting various aberrations and ensuring image quality at all focal lengths. The infrared continuous zoom lens 100 provided in Example 1 exhibits excellent imaging performance during zooming.

[0078] The above description is merely a preferred embodiment of the present application and an illustration of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. Infrared continuous zoom lens, characterized by: It includes a front fixed group, a variable magnification group, a compensation group, and a rear fixed group that are sequentially arranged from the object side to the image plane along the optical axis; the front fixed group includes a first lens with a positive optical power and a second lens with a positive optical power, the variable magnification group includes a third lens with a negative optical power, the compensation group includes a fourth lens with a negative optical power and a fifth lens with a positive optical power, and the rear fixed group includes a sixth lens with a positive optical power, a seventh lens with a negative optical power, and an eighth lens with a positive optical power; Among them, the number of lenses with optical power in the infrared continuous zoom lens is eight; The first lens is a meniscus lens with a convex surface facing the object side, the second lens is a meniscus lens with a convex surface facing the object side, the third lens is a biconcave lens, the fourth lens is a meniscus lens with a convex surface facing the object side, the fifth lens is a biconvex lens, the sixth lens is a meniscus lens with a convex surface facing the object side, the seventh lens is a meniscus lens with a concave surface facing the object side, and the eighth lens is a biconvex lens; The positions of the sixth lens of the front fixed group and the rear fixed group relative to the image plane are fixed; and The distances of the variable magnification group, the compensation group, the seventh lens and the eighth lens of the rear fixed group on the optical axis relative to the front fixed group are adjustable.

2. The infrared continuous zoom lens according to claim 1, characterized in that: The front fixed group satisfies: 1 < R2 / R1 < 2; Among them, R1 is the curvature radius of the object side surface of the first lens, and R2 is the curvature radius of the image side surface of the first lens.

3. The infrared continuous zoom lens according to claim 1, characterized in that: The infrared continuous zoom lens satisfies: -2 < ft×(n - 1) / (FNO×R1) < -1; and 0.01 < BFLt / ft < 0.04; Among them, ft is the focal length of the infrared continuous zoom lens in the long focal length state, n is the refractive index of the material of the first lens at the center wavelength, FNO is the F-number of the infrared continuous zoom lens, R1 is the curvature radius of the object side surface of the first lens, and BFLt is the back focal length of the infrared continuous zoom lens in the long focal length state.

4. The infrared continuous zoom lens according to claim 1, characterized in that: The infrared continuous zoom lens satisfies: 0.1< f1 / ft <1; 0.3< f2 / ft <1.2; 0.01< f3 / ft <0.5; 2.5< f4 / ft <5; 0.02< f5 / ft <0.3; 0.05< f6 / ft <0.5; 0.01< f7 / ft <0.1; And 0.01< f8 / ft <0.13; Among them, f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, f7 is the effective focal length of the seventh lens, f8 is the effective focal length of the eighth lens, and ft is the focal length of the infrared continuous zoom lens in the long focal length state.

5. The infrared continuous zoom lens according to claim 1, characterized in that: The material of the first lens is silicon material, and the refractive indices of the materials of the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the eighth lens are all within the range of 2.3 to 4.

5.

6. The infrared continuous zoom lens according to claim 1, characterized in that: The object side surface of the third lens, the image side surface of the sixth lens and the object side surface of the seventh lens are aspherical surfaces, and the object side surfaces of the fifth lens and the eighth lens are binary surfaces.

7. The infrared continuous zoom lens according to claim 6, characterized in that: The aspherical surface satisfies the following equation: Where Z is the axial sagittal height in the Z direction of the aspheric surface, r is the distance from the point on the aspheric surface to the optical axis, c is the curvature of the fitted sphere, which is the inverse of the curvature radius, k is the cone coefficient, and A, B, C, and D are the coefficients of the 4th, 6th, 8th, and 10th order terms of the aspheric polynomial.

8. The infrared continuous zoom lens according to claim 6, characterized in that: The two-dimensional surface satisfies the following equation: Among them, λ0 is the central wavelength during design, n0 is the refractive index corresponding to the central wavelength of the material, ; M is the diffraction order, N is the order of the polynomial coefficients in the series, A i is the diffraction surface phase coefficient, ρ is the normalized radial aperture coordinate, ρ=r / r1, r1 is the normalized radius of the diffraction surface.

9. The infrared continuous zoom lens according to claim 1, characterized in that: The zoom group and the compensation group perform nonlinear motion along opposite directions or opposite directions on the optical axis, so that the infrared continuous zoom lens is switched among a short focus state, a medium focus state and a long focus state.

10. The infrared continuous zoom lens according to claim 1, characterized in that: The infrared continuous zoom lens has a zoom ratio of 12X.

11. The infrared continuous zoom lens according to claim 1, characterized in that: The infrared continuous zoom lens has an operating band of 3.7 μm to 4.8 μm, a zoom range of f80 mm to f950 mm, an F number of 4, and a horizontal field angle of 0.6° to 6.9°.

12. An infrared thermal imaging system, characterized in that: The invention comprises the infrared continuous zoom lens according to any one of claims 1 to 11 and a medium-wave cooled detector, wherein the medium-wave cooled detector is located on the image plane of the infrared continuous zoom lens.

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