Medium-wave infrared continuous zoom lens

Abstract

The invention discloses a medium-wave infrared continuous zoom lens, which sequentially comprises a front fixed group, a zoom group, a compensation group, a rear fixed group and a detector from an object side to an image side along an optical axis, and is characterized in that the front fixed group comprises a first lens with positive focal power, the zoom group comprises a second lens with negative focal power, and the compensation group comprises a third lens with positive focal power; the compensation group comprises a third lens with positive focal power, and the rear fixing group comprises a fourth lens with positive focal power or negative focal power, a fifth lens with negative focal power and a sixth lens with positive focal power. The distance of the zoom group and the compensation group relative to the detector in the optical axis direction is adjustable, and the positions of the front fixing group and the rear fixing group relative to the detector in the optical axis direction are fixed.

Description

Technical Field

[0001] The present application relates to the field of optical elements, and more specifically, to a medium-wave infrared continuous zoom lens. Background Art

[0002] With the development of optical design level and modern processing technology, infrared thermal imaging lenses are used more and more widely in the field of monitoring. Complex application scenarios have made the market have higher and higher design requirements for infrared thermal imaging lenses. In order to meet different usage functions, the optical system is usually required to include multiple fields of view.

[0003] Continuous zoom lenses can realize continuous switching of different fields of view, conduct large-scale observation and search in a large field of view, and perform long-distance target recognition in a small field of view. They can be applied to complex monitoring fields such as road monitoring, forest fire prevention, straw burning, and airport monitoring. However, many zoom lenses currently have a small magnification ratio, mostly within 6 times, which seriously limits the application of lenses in some important occasions. The needs of larger-scale target search and longer-distance accurate recognition require zoom lenses with a larger magnification ratio. Summary of the invention

[0004] The present application provides a medium-wave infrared continuous zoom lens, which may include: a front fixed group, a zoom group, a compensation group, a rear fixed group and a detector in sequence from the object side to the image side along the optical axis, wherein the front fixed group includes a first lens with positive optical power; the zoom group includes a second lens with negative optical power; the compensation group includes a third lens with positive optical power; and the rear fixed group includes a fourth lens with positive optical power or negative optical power, a fifth lens with negative optical power and a sixth lens with positive optical power. The distances of the zoom group and the compensation group relative to the detector in the direction of the optical axis are adjustable, and the positions of the front fixed group and the rear fixed group relative to the detector in the direction of the optical axis are fixed.

[0005] In one embodiment, a curvature radius R2 of the image-side surface of the first lens and a curvature radius R1 of the object-side surface of the first lens may satisfy: 1≤R2 / R1≤3.

[0006] In one embodiment, the focal length ft of the medium-wave infrared continuous zoom lens in the telephoto state, the refractive index n of the central wavelength of the first lens material, the F number FNO of the medium-wave infrared continuous zoom lens, and the curvature radius R1 of the object side of the first lens may satisfy: 1.0 <ft×(n-1) / (FNO×R1)<1.6。

[0007] In one embodiment, the effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens and the focal length ft of the medium-wave infrared continuous zoom lens in the telephoto state may respectively satisfy the following: 0.1<|f1 / ft|<0.5; 0.01<|f2 / ft|<0.2; and 0.01<|f3 / ft|<0.3.

[0008] In one embodiment, the effective focal length f4 of the fourth lens, the effective focal length f5 of the fifth lens, the effective focal length f6 of the sixth lens, and the focal length ft of the medium-wave infrared continuous zoom lens in the telephoto state may respectively satisfy the following: 0.03<|f4 / ft|<0.95; 0.01<|f5 / ft|<0.2; and 0.01≤|f6 / ft|<0.1.

[0009] In one embodiment, a distance BFL from the image side surface of the sixth lens to an imaging plane of the medium-wave infrared continuous zoom lens on the optical axis and a focal length ft of the medium-wave infrared continuous zoom lens in a telephoto state may satisfy: 0.01≤BFL / ft<0.3.

[0010] In one embodiment, the first lens is made of silicon; and the second lens and the fifth lens are both made of germanium.

[0011] In one embodiment, the first lens is a meniscus lens with its convex surface facing the object side; the second lens is a biconcave lens; the third lens is a biconvex lens; the fourth lens is a meniscus lens with its convex surface facing the object side; the fifth lens is a meniscus lens with its convex surface facing the image side; and the sixth lens is a biconvex lens, wherein the object side surface of the second lens, the object side surface and image side surface of the fourth lens, and the object side surface of the fifth lens all adopt an even-order aspheric surface type; the object side surface of the third lens and the object side surface of the sixth lens adopt a binary surface type.

[0012] In one embodiment, the medium-wave infrared continuous zoom lens comprises a lens barrel having a cam curve groove, wherein the zoom group and the compensation group perform nonlinear motion in the direction along the optical axis through the cam curve groove, so that the medium-wave infrared continuous zoom lens switches between a short-focus state, a medium-focus state, and a long-focus state.

[0013] In one embodiment, the short focal range of the medium-wave infrared continuous zoom lens is 20 nm to 60 nm, the long focal range is 600 nm to 1550 nm, and the zoom ratio is greater than or equal to 20 times.

[0014] In one embodiment, the medium-wave infrared continuous zoom lens has a short focal length of 50 nm, a long focal length of 1300 nm, and a zoom ratio of greater than or equal to 25 times.

[0015] In one embodiment, the working aperture F number of the medium-wave infrared continuous zoom lens is 5.5, and the detector is a cooled detector.

[0016] In one embodiment, the horizontal field of view angle of the medium-wave infrared continuous zoom lens ranges from 0.4° to 10.9°.

[0017] The medium-wave infrared continuous zoom lens provided in the present application adopts a six-piece optical structure. By setting the lens to include a front fixed group, a magnification group, a compensation group and a rear fixed group, and reasonably setting the number of lenses and optical focal length and other characteristics contained in each group, the magnification group and the compensation group are moved along the optical axis. By changing the positions of the magnification group and the compensation group relative to the detector in the direction of the optical axis, while keeping the positions of the front fixed group and the rear fixed group fixed in the direction of the optical axis relative to the detector, 26x continuous zoom of the lens can be achieved. Through this magnification method, the system length can be effectively shortened, the number of lenses in the optical system can be effectively controlled, and it is beneficial to reduce costs.

[0018] In addition, the medium-wave infrared continuous zoom lens provided by the present application can enable the lens to have an active heat elimination function through the reasonable setting of parameters such as lens material, refractive index, surface shape, focal length, etc., which can meet the requirements of the lens having a stable imaging effect in a wide temperature range of -40° to +60°, so that the lens can be used in an environment with large temperature changes. Moreover, the medium-wave infrared continuous zoom lens provided by the present application adopts a mixed use of aspherical and diffractive surfaces, which can effectively correct chromatic aberration and improve the imaging quality of the optical system. At the same time, the reduction in the number of lenses also improves the transmittance of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Other features, purposes and advantages of the present application will become more apparent through the following detailed description of non-limiting embodiments in conjunction with the accompanying drawings. In the accompanying drawings:

[0020] Figure 1 A schematic structural diagram of a medium-wave infrared continuous zoom lens according to an exemplary embodiment of the present application is shown;

[0021] Figure 2 A schematic diagram showing the structure of a medium-wave infrared continuous zoom lens in a short-focus state, a medium-focus state, and a long-focus state according to an exemplary embodiment of the present application;

[0022] Figure 3 , Figure 4 and Figure 5The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the short-focus state according to Example 1 of the present application are respectively shown;

[0023] Figure 6 , Figure 7 and Figure 8 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the medium-focus state according to Example 1 of the present application are respectively shown;

[0024] Fig. 9 , Fig.10 and Fig.11 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the telephoto state according to Example 1 of the present application are respectively shown;

[0025] Fig.12 , Fig.13 and Fig.14 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the short-focus state according to Example 2 of the present application are respectively shown;

[0026] Fig.15 , Fig.16 and Fig.17 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the medium-focus state according to Example 2 of the present application are respectively shown;

[0027] Fig.18 , Fig.19 and Fig. 20 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the telephoto state according to Example 2 of the present application are respectively shown;

[0028] Fig.21 , Fig. 22 and Fig.23 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the short-focus state according to Example 3 of the present application are respectively shown;

[0029] Fig.24 , Fig.25 and Fig.26 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the medium-focus state according to Example 3 of the present application are respectively shown; and

[0030] Fig. 27 , Fig.28 and Fig.29 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the telephoto state according to Example 3 of the present application are respectively shown. DETAILED DESCRIPTION

[0031] In order to better understand the present application, a more detailed description will be made of various aspects of the present application with reference to the accompanying drawings. It should be understood that these detailed descriptions are only 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. The expression "and / or" includes any and all combinations of one or more of the associated listed items.

[0032] It should be noted that in this specification, the expressions of first, second, third, etc. are only used to distinguish one feature from another feature, and do not represent any limitation on the features. Therefore, without departing from the teaching of the present application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0033] In the drawings, for the sake of convenience, the thickness, size and shape of the lens are not drawn strictly to scale. The shapes of the spherical or aspherical surfaces shown in the drawings are shown by way of example, that is, the shapes of the spherical or aspherical surfaces are not limited to the shapes of the spherical or aspherical surfaces shown in the drawings, and the drawings are only examples and are not drawn strictly to scale.

[0034] In this article, the paraxial area refers to the area near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial area; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial area. The judgment of the surface type in the paraxial area can be judged according to the general method in this field, for example, the positive and negative R value (R refers to the radius of curvature of the paraxial area) is used to judge the concave and convex. In this article, the surface of each lens closest to the subject is called the object side of the lens, and the surface of each lens closest to the imaging surface is called the image side of the lens. For the object side, when the R value is positive, it is judged as a convex surface, and when the R value is negative, it is judged as a concave surface; for the image side, when the R value is positive, it is judged as a concave surface, and when the R value is negative, it is judged as a convex surface.

[0035] It should also be understood that the terms "comprises", "including", "having", "includes" and / or "comprising", when used in this specification, indicate the presence of the stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof. In addition, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire listed features rather than modifying the individual elements in the list. In addition, when describing embodiments of the present application, "may" is used to mean "one or more embodiments of the present application". And, the term "exemplary" is intended to refer to an example or illustration.

[0036] Unless otherwise defined, all terms (including technical terms and scientific terms) used in this article have the same meaning as commonly understood by ordinary technicians in the field to which this application belongs. It should also be understood that terms (such as terms defined in commonly used dictionaries) should be interpreted as having the same meaning as their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined in this article.

[0037] It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The following embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for those of ordinary skill in the art, several variations and improvements can also be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0038] The features, principles and other aspects of the present application are described in detail below.

[0039] like Figure 1 As shown, the medium-wave infrared continuous zoom lens according to the exemplary embodiment of the present application may include a front fixed group I, a zoom group II, a compensation group III, a rear fixed group IV and a detector V arranged in sequence from the object side to the image side along the optical axis. Among them, the front fixed group I may include a first lens E1; the zoom group II may include a second lens E2; the compensation group III may include a third lens E3; the rear fixed group IV may include a fourth lens E4, a fifth lens E5 and a sixth lens E6 in sequence from the object side to the image side along the optical axis; the detector V may include E7 and E8 in sequence from the object side to the image side along the optical axis. And, the medium-wave infrared continuous zoom lens may also include an image plane IMA.

[0040] In an exemplary embodiment, the first lens in the front fixed group of the medium-wave infrared continuous zoom lens of the present application may have a positive optical power; the second lens in the zoom group may have a negative optical power; the third lens in the compensation group may have a positive optical power; the fourth lens in the rear fixed group may have a positive optical power or a negative optical power, the fifth lens may have a negative optical power, and the sixth lens may have a positive optical power.

[0041] In an exemplary embodiment, the zoom group and the compensation group of the medium-wave infrared continuous zoom lens of the present application can move along the optical axis, and the front fixed group and the rear fixed group can remain stationary relative to the detector in the optical axis direction. In other words, the distances of the zoom group and the compensation group relative to the detector in the optical axis direction are adjustable, and the positions of the front fixed group and the rear fixed group relative to the detector in the optical axis direction are fixed.

[0042] Figure 2FIG. 101, FIG. 102, and FIG. 103 are schematic structural diagrams of a mid-wave infrared continuous zoom lens according to an exemplary embodiment of the present application when it is in a short focal length state, a medium focal length state, and a long focal length state, respectively. Comparing the schematic structural diagrams of the mid-wave infrared continuous zoom lens in the short focal length, medium focal length, and long focal length states, it can be seen that the adjustment or switching between different focal length states of the lens is achieved by the relative movement of the second lens E2 of the zoom group and the third lens E3 of the compensation group along the optical axis. As Figure 2 shown, by moving, the distances of the second lens E2 and the third lens E3 relative to the detectors E7 and E8 in the optical axis direction have both changed, while the distances of the first lens E1 of the front fixed group and the fourth lens E4, the fifth lens E5, and the sixth lens E6 of the rear fixed group relative to the detectors E7 and E8 in the optical axis direction remain unchanged.

[0043] The mid-wave infrared continuous zoom lens provided by the present application adopts a six-piece optical structure. By setting the lens to include a front fixed group, a zoom group, a compensation group, and a rear fixed group, and reasonably setting the number of lenses and optical power included in each group and other characteristics, and adopting the method of moving the zoom group and the compensation group along the optical axis, by changing the positions of the zoom group and the compensation group relative to the detector in the optical axis direction, while keeping the positions of the front fixed group and the rear fixed group relative to the detector in the optical axis direction fixed, 26-fold continuous zoom of the lens can be achieved. And through this zoom method, the system length can be effectively shortened, the number of lenses in the optical system can be effectively controlled, and the cost can be greatly reduced.

[0044] In an exemplary embodiment, the front fixed group of the mid-wave infrared continuous zoom lens of the present application can satisfy the conditional formula 1≤R2 / R1≤3, where R2 is the curvature radius of the image side of the first lens, and R1 is the curvature radius of the object side of the first lens.

[0045] In an exemplary embodiment, the mid-wave infrared continuous zoom lens of the present application can satisfy the conditional formula 1.0<ft×(n - 1) / (FNO×R1)<1.6, where ft is the focal length of the mid-wave infrared continuous zoom lens in the long focal length state, n is the refractive index of the center wavelength of the first lens material, FNO is the F-number of the mid-wave infrared continuous zoom lens, and R1 is the curvature radius of the object side of the first lens.

[0046] In an exemplary embodiment, the medium-wave infrared continuous zoom lens of the present application may satisfy the conditional formula 0.1<|f1 / ft|<0.5, 0.01<|f2 / ft|<0.2, and 0.01<|f3 / ft|<0.3, wherein 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, and ft is the focal length of the medium-wave infrared continuous zoom lens in the telephoto state. More specifically, f2 and ft may satisfy 0.01<|f2 / ft|<0.1; f3 and ft may satisfy 0.01<|f3 / ft|<0.1.

[0047] In an exemplary embodiment, the medium-wave infrared continuous zoom lens of the present application may satisfy the conditional formula 0.03<|f4 / ft|<0.95, 0.01<|f5 / ft|<0.2, and 0.01≤|f6 / ft|<0.1, wherein 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, and ft is the focal length of the medium-wave infrared continuous zoom lens in the telephoto state. More specifically, f4 and ft may satisfy 0.1<|f4 / ft|<0.95; f5 and ft may satisfy 0.01<|f5 / ft|<0.1.

[0048] In an exemplary embodiment, the medium-wave infrared continuous zoom lens of the present application may satisfy the conditional formula 0.01≤BFL / ft<0.3, wherein BFL is the distance on the optical axis from the image side surface of the sixth lens to the imaging surface of the medium-wave infrared continuous zoom lens, and ft is the focal length of the medium-wave infrared continuous zoom lens in a telephoto state. More specifically, BFL and ft may satisfy 0.01≤BFL / ft<0.1.

[0049] In an exemplary embodiment, the first lens in the front fixed group of the medium-wave infrared continuous zoom lens of the present application can be made of silicon material; the second lens in the zoom group and the fifth lens in the rear fixed group can both be made of germanium material. Specifically, the second lens in the zoom group and the fifth lens in the rear fixed group can both be made of germanium single crystal material.

[0050] In an exemplary embodiment, the first lens in the front fixed group of the medium-wave infrared continuous zoom lens of the present application can be a meniscus lens with a convex surface facing the object side; the second lens in the zoom group can be a biconcave lens; the third lens in the compensation group can be a biconvex lens; the fourth lens in the rear fixed group can be a meniscus lens with a convex surface facing the object side; the fifth lens in the rear fixed group can be a meniscus lens with a convex surface facing the image side; and the sixth lens in the rear fixed group can be a biconvex lens.

[0051] In an exemplary embodiment, the object side surface of the second lens in the zoom group of the medium-wave infrared continuous zoom lens of the present application, the object side surface and image side surface of the fourth lens in the rear fixed group, and the object side surface of the fifth lens in the rear fixed group can all adopt an even-order aspherical surface type.

[0052] In an exemplary embodiment, the object-side surface of the third lens in the compensation group and the object-side surface of the sixth lens in the rear fixed group may adopt a binary surface type.

[0053] In an exemplary embodiment, during the focal length change process of the medium-wave infrared continuous zoom lens of the present application, the zoom group and the compensation group can perform nonlinear motion along the optical axis, so that the lens can be switched between a short-focus state, a medium-focus state, and a long-focus state. Exemplarily, the zoom group and the compensation group can perform nonlinear motion in the opposite directions of the optical axis. Exemplarily, the relative motion of the zoom group and the compensation group can be controlled by, for example, a cam curve groove provided on the lens barrel to achieve the adjustment of the focal length of the medium-wave infrared continuous zoom lens. Exemplarily, two cam curve grooves, for example, can be provided on the lens barrel to respectively control the relative motion of the second lens of the zoom group and the third lens of the compensation group.

[0054] In an exemplary embodiment, the short focal range of the medium-wave infrared continuous zoom lens of the present application is 20nm to 60nm, and the long focal range is 600nm to 1550nm. The zoom ratio of the medium-wave infrared continuous zoom lens of the present application can be greater than or equal to 20 times, for example, up to 26 times.

[0055] In an exemplary embodiment, the short focal length of the medium-wave infrared continuous zoom lens of the present application is 50 nm, the long focal length is 1300 nm, and the zoom ratio is greater than or equal to 25 times.

[0056] In an exemplary embodiment, the working aperture F number of the medium-wave infrared continuous zoom lens of the present application is 5.5.

[0057] In an exemplary embodiment, the working band of the medium-wave infrared continuous zoom lens of the present application is 3.7 μm to 4.8 μm.

[0058] In an exemplary embodiment, the detector adapted to the medium-wave infrared continuous zoom lens of the present application is a refrigerated detector, with a resolution of 640×512 and a pixel size of 15 μm.

[0059] In an exemplary embodiment, the horizontal field of view angle of the medium-wave infrared continuous zoom lens of the present application ranges from 0.4° to 10.9°.

[0060] In summary, the medium-wave infrared continuous zoom lens provided in accordance with the exemplary embodiment of the present application adopts a six-piece optical structure, can achieve 26x continuous zoom, and has an active thermal difference elimination function, which can meet the requirements of the lens having a stable imaging effect within a wide temperature range of -40° to +60°, and can meet the requirements of the lens being used in an environment with large temperature changes.

[0061] According to the medium-wave infrared continuous zoom lens provided by the exemplary embodiment of the present application, the zoom group and the compensation group are moved, which not only realizes the continuous zoom function of the 26x optical system, but also effectively shortens the system length and effectively controls the number of lenses in the optical system through the zoom method, which can greatly reduce the cost. At the same time, the present application adopts a mixed use of aspheric and diffractive surfaces, which can effectively correct chromatic aberration and improve the imaging quality of the optical system. At the same time, the reduction in the number of lenses can also improve the transmittance of the system.

[0062] Although the exemplary structure and features of the medium-wave infrared continuous zoom lens are described in this article, those skilled in the art should understand that one or more features may be omitted, replaced or added without departing from the technical solution claimed for protection in this application. The above description is only an exemplary illustration of the implementation method of the present application. The scope of protection involved in this application is not limited to the technical solution formed by a specific combination of the above-mentioned technical features, but should also cover other technical solutions formed by any combination of the above-mentioned technical features or their equivalent features without departing from the technical concept of this application. For example, the above-mentioned features are replaced with the technical features with similar functions disclosed in this application (but not limited to) to form a technical solution.

[0063] The following is combined with Figures 3 to 29 A specific embodiment of a medium-wave infrared continuous zoom lens applicable to the above-mentioned embodiment is further described.

[0064] Example 1

[0065] The structural schematic diagram of the medium-wave infrared continuous zoom lens according to Example 1 can be found in Figure 1 , specifically, it may include a front fixed group I, a zoom group II, a compensation group III, a rear fixed group IV and a detector V arranged in sequence from the object side to the image side along the optical axis. Among them, the front fixed group I includes a first lens E1; the zoom group II includes a second lens E2; the compensation group III includes a third lens E3; the rear fixed group IV includes a fourth lens E4, a fifth lens E5 and a sixth lens E6 in sequence from the object side to the image side along the optical axis; the detector V includes E7 and E8 in sequence from the object side to the image side along the optical axis. And, the medium-wave infrared continuous zoom lens may also include an image plane IMA.

[0066] Table 1 shows basic optical parameters of the medium-wave infrared continuous zoom lens according to Example 1 of the present application.

[0067] Face number Face type Curvature radius (mm) Spacing(mm) Material Diameter(mm) S1 Spherical 489.27 22.16 silicon 275 S2 Spherical 860.18 37.48～304.18 269 S3 Aspheric -311.34 6.77 germanium 81 S4 Spherical 570.23 7.26～341.90 81 S5 Two-dimensional surface 209.69 14.77 Zinc Selenide 87 S6 Spherical -226.09 5.54～73.48 88 S7 Aspheric 39.23 9.23 Chalcogenide glass 42 S8 Aspheric 32.29 49.17 35 S9 Aspheric -54.23 4.92 germanium 12 S10 Spherical -134.77 62.48 12 S11 Two-dimensional surface 31.91 4.92 silicon 20 S12 Spherical 121.92 16.51 19 S13 flat infinity 1 silicon - S14 flat infinity 2.83 - S15 Aperture surface infinity 0.3 germanium - S16 flat infinity 20 - IMA flat infinity - -

[0068] Table 1

[0069] In this embodiment, the object-side surface S3 of the second lens, the object-side surface S5 of the third lens, the object-side surface S7 and the image-side surface S8 of the fourth lens, the object-side surface S9 of the fifth lens, and the object-side surface S11 of the sixth lens are all aspherical surfaces, and the surface shape of each aspherical surface can be defined by but not limited to the following aspherical surface formula:

[0070]

[0071] Wherein, z(r) is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of r along the optical axis; c is the paraxial curvature of the aspheric surface, c=1 / R (i.e., the paraxial curvature c is the reciprocal of the curvature radius R in Table 1 above); k is the cone coefficient; a i The following table 2 shows the cone coefficient k and the high-order coefficient a of each aspheric mirror surface S3, S5, S7 to S9 and S11 that can be used in this embodiment. 4 、a 6 、a 8 、a 10 and a 12 .

[0072]

[0073]

[0074] Table 2

[0075] In this embodiment, the object-side surface S5 of the third lens and the object-side surface S11 of the sixth lens are two-dimensional surfaces, and the surface shape of the two-dimensional surface can be defined by but not limited to the following formula:

[0076]

[0077] Among them, λ 0 is the central wavelength at design time, n 0 is the refractive index of the material at the central wavelength, and

[0078]

[0079] Where M is the diffraction order, N is the order of the polynomial coefficients in the series, and A i is the coefficient of ρ raised to the 2ith power, where ρ is the normalized radial aperture coordinate.

[0080] Table 3 below gives the normalized radius values ​​and coefficients A that can be used for the binary surfaces S5 and S11 in this embodiment. 1 , A 2, A 3 , A 4 The value of .

[0081] Face number Face type Normalized radius <![CDATA[A 1 ]]> <![CDATA[A 2 ]]> <![CDATA[A 3 ]]> <![CDATA[A 4 ]]> S5 Two-dimensional surface 42.00 -136.49 -61.90 130.14 -67.27 S11 Two-dimensional surface 12.00 -61.26 -10.24 37.28 -33.99

[0082] Table 3

[0083] The medium-wave infrared continuous zoom lens according to Example 1 can adjust or switch the lens between different focal length states by relative movement of the second lens E2 of the zoom group and the third lens E3 of the compensation group along the optical axis. The structural schematic diagram of the lens in the short focal state, the medium focal state and the long focal state can be seen in Figure 2 During the continuous zooming process of the lens, the distances of the first lens E1 of the front fixed group and the fourth lens E4, the fifth lens E5 and the sixth lens E6 of the rear fixed group relative to the detectors E7 and E8 along the optical axis direction remain unchanged.

[0084] Figure 3 , Figure 4 and Figure 5 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 1 in a short-focus state are respectively shown; Figure 6 , Figure 7 and Figure 8 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 1 in the medium focus state are respectively shown; and Fig. 9 , Fig.10 and Fig.11 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 1 in the telephoto state are respectively shown.

[0085] Depend on Figure 3 , Figure 6 and Fig. 9 It can be seen that under different focal lengths, the diffuse spot radius of the medium-wave infrared continuous zoom lens according to Example 1 at different field of view positions varies slightly, which means that the aberration of the medium-wave infrared continuous zoom lens at different field of view positions is relatively small. Figure 4 , Figure 7 and Fig.10 It can be seen that under different focal lengths, the field curvatures in the meridian and sagittal directions generated by the medium-wave infrared continuous zoom lens according to Example 1 for light of different wavelengths are respectively between -1.0mm and 0mm, -1.0mm and 0mm, and -0.2mm and 0.2mm. Figure 5 , Figure 8 and Fig.11It can be seen that under different focal lengths, the maximum distortion of the medium-wave infrared continuous zoom lens according to Example 1 is within the range of -2.0% to 0, which means that the medium-wave infrared continuous zoom lens can achieve smaller field curvature and distortion under different focal lengths. In summary, the medium-wave infrared continuous zoom lens provided in Example 1 can ensure the imaging quality under various focal lengths and has a good imaging effect during the zooming process.

[0086] Example 2

[0087] The structural schematic diagram of the medium-wave infrared continuous zoom lens according to Example 2 can be found in Figure 1 , specifically, it may include a front fixed group I, a zoom group II, a compensation group III, a rear fixed group IV and a detector V arranged in sequence from the object side to the image side along the optical axis. Among them, the front fixed group I includes a first lens E1; the zoom group II includes a second lens E2; the compensation group III includes a third lens E3; the rear fixed group IV includes a fourth lens E4, a fifth lens E5 and a sixth lens E6 in sequence from the object side to the image side along the optical axis; the detector V includes E7 and E8 in sequence from the object side to the image side along the optical axis. And, the medium-wave infrared continuous zoom lens may also include an image plane IMA.

[0088] Table 4 shows the basic optical parameters of the medium-wave infrared continuous zoom lens according to Example 2 of the present application.

[0089] Face number Face type Curvature radius (mm) Spacing(mm) Material Diameter(mm) S1 Spherical 400.30 14.5 silicon 230 S2 Spherical 717.69 37～249 224 S3 Aspheric -255.13 5.5 germanium 69 S4 Spherical 468.49 3～269 69 S5 Two-dimensional surface 166.09 12.0 Zinc Selenide 74 S6 Spherical -195.16 6～61 74 S7 Aspheric 31.60 7.5 Chalcogenide glass 36 S8 Aspheric 26.70 34.54 27.2 S9 Aspheric -30.51 4.0 germanium 10.8 S10 Spherical -50.03 52.26 14 S11 Two-dimensional surface 55.45 4.0 silicon 23 S12 Spherical -100.00 15.11 23 S13 flat infinity 1 silicon - S14 flat infinity 2.83 - S15 Aperture surface infinity 0.3 germanium - S16 flat infinity 20 - IMA flat infinity - -

[0090] Table 4

[0091] In this embodiment, the object side surface S3 of the second lens, the object side surface S5 of the third lens, the object side surface S7 and the image side surface S8 of the fourth lens, the object side surface S9 of the fifth lens, and the object side surface S11 of the sixth lens are all aspherical surfaces, and the surface shape of each aspherical surface can be defined by the formula (1) given in the above embodiment 1. The following Table 5 gives the cone coefficient k and the high-order coefficient a of each aspherical mirror surface S3, S5, S7 to S9 and S11 that can be used in this embodiment. 4 、a 6 、a 8 、a 10 and a 12 .

[0092] Face number Face type k <![CDATA[a 4 ]]> <![CDATA[a 6 ]]> <![CDATA[a 8 ]]> <![CDATA[a 10 ]]> <![CDATA[a 12 ]]> S3 Aspheric -2.86 1.07E-08 1.24E-11 -1.25E-14 4.47E-18 -3.60E-22 S5 Aspheric -5.30 -9.12E-08 4.51E-12 -1.61E-15 2.09E-18 -1.07E-21 S7 Aspheric 0.00 2.82E-07 3.91E-10 4.56E-12 -2.33E-14 -2.16E-18 S8 Aspheric 0.11 -1.52E-06 -3.55E-09 3.05E-11 -2.71E-13 1.38E-16 S9 Aspheric 32.80 1.16E-04 4.54E-08 1.13E-07 -3.69E-09 7.33E-11 S11 Aspheric 3.65 -1.79E-05 -4.50E-09 2.54E-10 -4.06E-12 1.39E-14

[0093] Table 5

[0094] In this embodiment, the object side surface S5 of the third lens and the object side surface S11 of the sixth lens are two-dimensional surfaces, and the surface shape of each two-dimensional surface can be defined by the formula (2) given in the above embodiment 1. The following table 6 gives the normalized radius values ​​and coefficients A of the two-dimensional surfaces S5 and S11 that can be used in this embodiment. 1 , A 2 , A3 , A 4 The value of .

[0095] Face number Face type Normalized radius <![CDATA[A 1 ]]> <![CDATA[A 2 ]]> <![CDATA[A 3 ]]> <![CDATA[A 4 ]]> S5 Two-dimensional surface 40.00 -151.99 -32.58 104.77 -75.69 S11 Two-dimensional surface 13.00 -106.52 -39.28 264.38 -322.51

[0096] Table 6

[0097] The medium-wave infrared continuous zoom lens according to Example 2 can adjust or switch the lens between different focal length states by relative movement of the second lens E2 of the zoom group and the third lens E3 of the compensation group along the optical axis. The structural schematic diagram of the lens in the short focal state, the medium focal state and the long focal state can be seen in Figure 2 During the continuous zooming process of the lens, the distances of the first lens E1 of the front fixed group and the fourth lens E4, the fifth lens E5 and the sixth lens E6 of the rear fixed group relative to the detectors E7 and E8 along the optical axis direction remain unchanged.

[0098] Fig.12 , Fig.13 and Fig.14 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 2 in a short-focus state are respectively shown; Fig.15 , Fig.16 and Fig.17 respectively show the dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 2 in a medium-focus state; and Fig.18 , Fig.19 and Fig. 20 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 2 in the telephoto state are respectively shown.

[0099] Depend on Fig.12 , Fig.15 and Fig.18 It can be seen that under different focal lengths, the diffuse spot radius of the medium-wave infrared continuous zoom lens according to Example 2 at different field of view positions varies slightly, which means that the aberration of the medium-wave infrared continuous zoom lens at different field of view positions is relatively small. Fig.13 , Fig.16 and Fig.19 It can be seen that under different focal lengths, the field curvatures in the meridian and sagittal directions generated by the medium-wave infrared continuous zoom lens according to Example 2 for light of different wavelengths are respectively between -1.0 mm and 0 mm, 0 mm and 0.5 mm, and 0 mm and 1.0 mm. Fig.14 , Fig.17 and Fig. 20It can be seen that under different focal lengths, the maximum distortion of the medium-wave infrared continuous zoom lens according to Example 2 is within -0.2% to 0, 0 to 1.0%, and 0 to 1.0%, respectively, which means that the medium-wave infrared continuous zoom lens can achieve smaller field curvature and distortion under different focal lengths. In summary, the medium-wave infrared continuous zoom lens provided in Example 2 can ensure the imaging quality under each focal length state and has a good imaging effect during the zooming process.

[0100] Example 3

[0101] The structural schematic diagram of the medium-wave infrared continuous zoom lens according to Example 3 can be found in Figure 1 , specifically, it may include a front fixed group I, a zoom group II, a compensation group III, a rear fixed group IV and a detector V arranged in sequence from the object side to the image side along the optical axis. Among them, the front fixed group I includes a first lens E1; the zoom group II includes a second lens E2; the compensation group III includes a third lens E3; the rear fixed group IV includes a fourth lens E4, a fifth lens E5 and a sixth lens E6 in sequence from the object side to the image side along the optical axis; the detector V includes E7 and E8 in sequence from the object side to the image side along the optical axis. And, the medium-wave infrared continuous zoom lens may also include an image plane IMA.

[0102] Table 7 shows the basic optical parameters of the medium-wave infrared continuous zoom lens according to Example 3 of the present application.

[0103] Face number Face type Curvature radius (mm) Spacing(mm) Material Diameter(mm) S1 Spherical 188.13 8.61 silicon 123 S2 Spherical 328.20 16.11～118.28 121 S3 Aspheric -111.55 2.63 germanium 38 S4 Spherical 255.73 3.1～131.79 39 S5 Two-dimensional surface 85.54 5.74 Zinc Selenide 43 S6 Spherical -83.69 2.26～29.34 43 S7 Aspheric 15.12 3.59 Chalcogenide glass 21 S8 Aspheric 12.51 18.95 18 S9 Aspheric -11.39 1.91 germanium 7 S10 Spherical -15.35 22.33 8 S11 Two-dimensional surface 34.05 2.40 silicon 13 S12 Spherical -70.46 7.41 13 S13 flat infinity 1 silicon - S14 flat infinity 2.83 - S15 Aperture surface infinity 0.3 germanium - S16 flat infinity 20 - IMA flat infinity - -

[0104] Table 7

[0105] In this embodiment, the object side surface S3 of the second lens, the object side surface S5 of the third lens, the object side surface S7 and the image side surface S8 of the fourth lens, the object side surface S9 of the fifth lens, and the object side surface S11 of the sixth lens are all aspherical surfaces, and the surface shape of each aspherical surface can be defined by the formula (1) given in the above embodiment 1. The following Table 8 gives the cone coefficient k and the high-order coefficient a of each aspherical mirror surface S3, S5, S7 to S9 and S11 that can be used in this embodiment. 4 、a 6 、a 8 、a 10 and a 12 .

[0106]

[0107]

[0108] Table 8

[0109] In this embodiment, the object side surface S5 of the third lens and the object side surface S11 of the sixth lens are two-dimensional surfaces, and the surface shape of each two-dimensional surface can be defined by the formula (2) given in the above embodiment 1. The following table 9 gives the normalized radius values ​​and coefficients A of the two-dimensional surfaces S5 and S11 that can be used in this embodiment. 1 , A 2 , A 3 , A 4 The value of .

[0110] Face number Face type Normalized radius <![CDATA[A 1 ]]> <![CDATA[A 2 ]]> <![CDATA[A 3 ]]> <![CDATA[A 4 ]]> S5 Two-dimensional surface 19.1 -77.20 -19.10 47.86 -22.98 S11 Two-dimensional surface 6.2 -30.48 -7.59 21.93 -11.85

[0111] Table 9

[0112] The medium-wave infrared continuous zoom lens according to Example 3 can adjust or switch the lens between different focal length states by relative movement of the second lens E2 of the zoom group and the third lens E3 of the compensation group along the optical axis. The structural schematic diagram of the lens in the short focal state, the medium focal state and the long focal state can be seen in Figure 2 During the continuous zooming process of the lens, the distances of the first lens E1 of the front fixed group and the fourth lens E4, the fifth lens E5 and the sixth lens E6 of the rear fixed group relative to the detectors E7 and E8 along the optical axis direction remain unchanged.

[0113] Fig.21 , Fig. 22 and Fig.23 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens in the short-focus state according to Example 3 are respectively shown; Fig.24 , Fig.25 and Fig.26 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 3 in the medium focus state are respectively shown; and Fig. 27 , Fig.28 and Fig.29 The dispersion pattern, field curvature curve and distortion curve of the medium-wave infrared continuous zoom lens according to Example 3 in the telephoto state are respectively shown.

[0114] Depend on Fig.21 , Fig.24 and Fig. 27 It can be seen that under different focal lengths, the diffuse spot radius of the medium-wave infrared continuous zoom lens according to Example 3 at different field of view positions varies slightly, which means that the aberration of the medium-wave infrared continuous zoom lens at different field of view positions is relatively small. Fig. 22 , Fig.25 and Fig.28It can be seen that under different focal lengths, the field curvatures in the meridian and sagittal directions generated by the medium-wave infrared continuous zoom lens according to Example 3 for light of different wavelengths are respectively between -0.5mm to 0.5mm, -1.0mm to 1.0mm, and -1.0mm to 1.0mm. Fig.23 , Fig.26 and Fig.29 It can be seen that under different focal lengths, the maximum distortion of the medium-wave infrared continuous zoom lens according to Example 3 is within -5.0% to 0, -2.0% to 0, and -2.0% to 0, respectively, which means that the medium-wave infrared continuous zoom lens can achieve smaller field curvature and distortion under different focal lengths. In summary, the medium-wave infrared continuous zoom lens provided in Example 3 can ensure the imaging quality under each focal length state and has a good imaging effect during the zooming process.

[0115] In addition, Example 1 to Example 3 respectively satisfy the conditions shown in Table 10 below.

[0116]

[0117]

[0118] Table 10

[0119] The present application also provides an imaging device, which is provided with an electronic photosensitive element for imaging, and the electronic photosensitive element can be a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS). The imaging device is equipped with the above-described medium-wave infrared continuous zoom lens.

[0120] The above description is only a preferred embodiment of the present application and an explanation of the technical principles used. Those skilled in the art should understand that the scope of protection involved in the present application is not limited to the technical solution formed by a specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the concept of the present application. For example, the above features are replaced with the technical features with similar functions disclosed in the present application (but not limited to) to form a technical solution.

Claims

1. A medium-wave infrared continuous zoom lens, characterized in that: Along the optical axis from the object side to the image side, it includes: a front fixed group, a zoom group, a compensation group, a rear fixed group and a detector, wherein: The front fixed group includes a first lens having positive optical power; The zoom group includes a second lens having negative optical power; The compensation group includes a third lens having positive optical power; and The rear fixed group includes a fourth lens having positive or negative optical power, a fifth lens having negative optical power, and a sixth lens having positive optical power; The distances of the variable magnification group and the compensation group relative to the detector in the direction of the optical axis are adjustable, and the positions of the front fixing group and the rear fixing group relative to the detector in the direction of the optical axis are fixed.

2. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The curvature radius R2 of the image-side surface of the first lens and the curvature radius R1 of the object-side surface of the first lens satisfy: 1≤R2 / R1≤3.

3. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The focal length ft of the medium-wave infrared continuous zoom lens in the telephoto state, the refractive index n of the central wavelength of the first lens material, the F number FNO of the medium-wave infrared continuous zoom lens, and the curvature radius R1 of the object side surface of the first lens satisfy: 1.0 <ft×(n-1) / (FNO×R1)<1.6。 4. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The effective focal length f1 of the first lens, the effective focal length f2 of the second lens, the effective focal length f3 of the third lens and the focal length ft of the medium-wave infrared continuous zoom lens in the telephoto state respectively satisfy: 0.1<|f1 / ft|<0.5; 0.01<|f2 / ft|<0.2; as well as 0.01<|f3 / ft|<0.

3.

5. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The effective focal length f4 of the fourth lens, the effective focal length f5 of the fifth lens, the effective focal length f6 of the sixth lens and the focal length ft of the medium-wave infrared continuous zoom lens in the telephoto state respectively satisfy: 0.03<|f4 / ft|<0.95; 0.01<|f5 / ft|<0.2; as well as 0.01≤|f6 / ft|<0.

1.

6. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The distance BFL from the image side surface of the sixth lens to the imaging surface of the medium-wave infrared continuous zoom lens on the optical axis and the focal length ft of the medium-wave infrared continuous zoom lens in the telephoto state satisfy: 0.01≤BFL / ft<0.

3.

7. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The first lens is made of silicon material; The second lens and the fifth lens are both made of germanium.

8. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The first lens is a meniscus lens with a convex surface facing the object side; The second lens is a biconcave lens; The third lens is a biconvex lens; The fourth lens is a meniscus lens with a convex surface facing the object side; The fifth lens is a meniscus lens with a convex surface facing the image side; and The sixth lens is a biconvex lens, Among them, the object side surface of the second lens, the object side surface and image side surface of the fourth lens, and the object side surface of the fifth lens all adopt an even-order aspheric surface type; the object side surface of the third lens and the object side surface of the sixth lens adopt a binary surface type.

9. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The medium-wave infrared continuous zoom lens comprises a lens barrel having a cam curve groove, wherein the zoom group and the compensation group perform nonlinear motion in the direction along the optical axis through the cam curve groove, so that the medium-wave infrared continuous zoom lens switches between a short-focus state, a medium-focus state and a long-focus state.

10. The medium-wave infrared continuous zoom lens according to claim 1, characterized in that: The short focal range of the medium-wave infrared continuous zoom lens is 20nm to 60nm, the long focal range is 600nm to 1550nm, and the zoom ratio is greater than or equal to 20 times.

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