Continuous zoom lens for the mid-wave infrared

Abstract

The application discloses a middle-wave infrared continuous zoom lens, which comprises a front fixed group, a zoom group, a compensation group, a rear fixed group and a detector in sequence from an object side to an image side along an optical axis. The front fixed group comprises a first lens with positive refractive power, the zoom group comprises a second lens with negative refractive power, the compensation group comprises a third lens with positive refractive power, and the rear fixed group comprises a fourth lens with positive refractive power or negative refractive power, a fifth lens with negative refractive power and a sixth lens with positive refractive power. The distance between the zoom group and the compensation group relative to the detector in the direction of the optical axis is 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.

Description

Technical Field

[0001] This application relates to the field of optical components, and more specifically, to a mid-wave infrared continuous zoom lens. Background Technology

[0002] With the development of optical design and modern processing technology, infrared thermal imaging lenses are being used more and more widely in the field of surveillance. Complex application scenarios have led to increasingly higher design requirements for infrared thermal imaging lenses. To meet different functional requirements, optical systems usually need to include multiple fields of view.

[0003] Continuous zoom lenses enable seamless switching between different fields of view, allowing for wide-area observation and searching in a large field of view, and long-distance target identification in a small field of view. They can be applied to complex surveillance fields such as road monitoring, forest fire prevention, straw burning surveillance, and airport monitoring. However, many current zoom lenses have relatively small zoom ratios, mostly below 6x, which severely limits their application in some important situations. The need for wider target searching and more accurate identification at greater distances requires zoom lenses with larger zoom ratios. Summary of the Invention

[0004] This application provides a mid-wave infrared continuous zoom lens, which may include, sequentially from the object side to the image side along the optical axis: a front fixed group, a zoom group, a compensation group, a rear fixed group, and a detector. 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 either positive 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 along the optical axis are adjustable, while the positions of the front fixed group and the rear fixed group relative to the detector along the optical axis are fixed.

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

[0006] In one embodiment, the focal length ft of the mid-wave infrared continuous zoom lens in telephoto mode, the refractive index n of the center wavelength of the first lens material, the F-number FNO of the mid-wave infrared continuous zoom lens, and the radius of curvature R1 of the object-side surface of the first lens can 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 mid-wave infrared continuous zoom lens in telephoto mode can respectively satisfy: 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 mid-wave infrared continuous zoom lens in telephoto mode can respectively satisfy: 0.03 < |f4 / ft| < 0.95; 0.01 < |f5 / ft| < 0.2; and 0.01 ≤ |f6 / ft| < 0.1.

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

[0010] In one embodiment, the first lens is made of silicon; 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 the image-side surface of the fourth lens, and the object-side surface of the fifth lens are all of even order aspherical surface type; the object-side surface of the third lens and the object-side surface of the sixth lens are of binary surface type.

[0012] In one embodiment, the mid-wave infrared continuous zoom lens includes a lens barrel with a cam groove, wherein the zoom group and the compensation group move non-linearly along the optical axis via the cam groove, thereby switching the mid-wave infrared continuous zoom lens between a short focal length state, a medium focal length state, and a long focal length state.

[0013] In one embodiment, the mid-wave infrared continuous zoom lens has a short focal length range of 20mm to 60mm, a long focal length range of 600mm to 1550mm, and a zoom ratio of ≥20x.

[0014] In one embodiment, the mid-wave infrared continuous zoom lens has a short focal length of 50mm, a long focal length of 1300mm, and a zoom ratio of ≥25x.

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

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

[0017] The mid-wave infrared continuous zoom lens provided in this application adopts a six-element 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 of each group, the zoom group and the compensation group are moved along the optical axis. By changing the position of the zoom group and the compensation group relative to the detector in the optical axis direction, while keeping the position of the front fixed group and the rear fixed group relative to the detector in the optical axis direction fixed, a 26x continuous zoom can be achieved. Moreover, this zoom method can effectively shorten the system length, effectively control the number of lenses in the optical system, and help reduce costs.

[0018] Furthermore, the mid-wave infrared continuous zoom lens provided in this application, through the rational setting of parameters such as lens material, refractive index, surface shape, and focal length, enables the lens to have an active pyrometry function, ensuring stable imaging performance within a wide temperature range of -40°C to +60°C, allowing the lens to be used in environments with significant temperature variations. Moreover, the mid-wave infrared continuous zoom lens provided in this application employs a hybrid approach using aspherical and diffractive surfaces, effectively correcting chromatic aberration and improving the imaging quality of the optical system. Simultaneously, the reduction in the number of lenses also significantly improves the system's transmittance. Attached Figure Description

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

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

[0021] Figure 2 A schematic diagram of a mid-wave infrared continuous zoom lens according to an exemplary embodiment of this application is shown in a short focal length state, a medium focal length state and a long focal length state respectively.

[0022] Figure 3 , Figure 4 and Figure 5The diffusion pattern, field curvature curve and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 1 of this application are shown respectively in the short focal length state;

[0023] Figure 6 , Figure 7 and Figure 8 The diffusion pattern, field curvature curve and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 1 of this application are shown respectively in the mid-focal state.

[0024] Figure 9 , Figure 10 and Figure 11 The diffusion pattern, field curvature curve and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 1 of this application are shown respectively in the telephoto state;

[0025] Figure 12 , Figure 13 and Figure 14 The blur pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 2 of this application are shown respectively in the short focal length state;

[0026] Figure 15 , Figure 16 and Figure 17 The diffusion pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 2 of this application are shown respectively in the mid-focal state.

[0027] Figure 18 , Figure 19 and Figure 20 The diffusion pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 2 of this application are shown respectively in the telephoto state.

[0028] Figure 21 , Figure 22 and Figure 23 The blur pattern, field curvature curve and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 3 of this application are shown respectively in the short focal length state;

[0029] Figure 24 , Figure 25 and Figure 26 The diffusion pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 3 of this application are shown respectively in the mid-focus state; and

[0030] Figure 27 , Figure 28 and Figure 29 The diffusion pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Embodiment 3 of this application are shown respectively in the telephoto state. Detailed Implementation

[0031] To better understand this application, various aspects of this application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of this application and are not intended to limit the scope of this 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 terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Therefore, without departing from the teachings of this application, the first lens discussed below may also be referred to as the second lens or the third lens.

[0033] In the accompanying drawings, for ease of illustration, the thickness, size, and shape of the lenses are not drawn to scale. The shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example only; that is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings, and the drawings are merely examples and not drawn to scale.

[0034] In this paper, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of the convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of the concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface shape in the paraxial region can be determined according to methods commonly used in the art, such as using the sign of the R value (R refers to the radius of curvature of the paraxial region) to determine concavity or convexity. In this paper, 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. For the object-side surface, when the R value is positive, it is determined to be convex, and when the R value is negative, it is determined to be concave; for the image-side surface, when the R value is positive, it is determined to be concave, and when the R value is negative, it is determined to be convex.

[0035] It should also be understood that the terms "comprising," "including," "having," "containing," 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. Furthermore, when expressions such as "at least one of..." appear after a list of listed features, they modify the entire list of features, not individual elements in the list. Additionally, when describing embodiments of this application, the word "may" is used to mean "one or more embodiments of this application." And the term "exemplary" is intended to refer to an example or illustration.

[0036] Unless otherwise specified, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. It should also be understood that terms (e.g., those defined in common dictionaries) shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art and shall not be interpreted in an idealized or overly formalized sense, unless expressly so specified herein.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other. The following embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of this application. It should be pointed out that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. This application will now be described in detail with reference to the accompanying drawings and embodiments.

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

[0039] like Figure 1 As shown, a mid-wave infrared continuous zoom lens according to an exemplary embodiment of this 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 sequentially along the optical axis from the object side to the image side. Specifically, 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 arranged sequentially along the optical axis from the object side to the image side; and the detector V may include E7 and E8 arranged sequentially along the optical axis from the object side to the image side. Furthermore, the mid-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 mid-wave infrared continuous zoom lens of this application may have positive optical power; the second lens in the zoom group may have negative optical power; the third lens in the compensation group may have positive optical power; the fourth lens in the rear fixed group may have positive or negative optical power, the fifth lens may have negative optical power, and the sixth lens may have positive optical power.

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

[0042] Figure 2FIG. 101, FIG. 102, and FIG. 103 show 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. By 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 that the lens includes 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 surface of the first lens, and R1 is the curvature radius of the object side surface 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 surface of the first lens.

[0046] In an exemplary embodiment, the mid-wave infrared continuous zoom lens of this application can satisfy the conditions 0.1 < |f1 / ft| < 0.5, 0.01 < |f2 / ft| < 0.2, and 0.01 < |f3 / ft| < 0.3, 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, and ft is the focal length of the mid-wave infrared continuous zoom lens in telephoto mode. More specifically, f2 and ft can satisfy 0.01 < |f2 / ft| < 0.1; f3 and ft can satisfy 0.01 < |f3 / ft| < 0.1.

[0047] In an exemplary embodiment, the mid-wave infrared continuous zoom lens of this application can satisfy the conditions 0.03 < |f4 / ft| < 0.95, 0.01 < |f5 / ft| < 0.2, and 0.01 ≤ |f6 / ft| < 0.1, where 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 mid-wave infrared continuous zoom lens in telephoto mode. More specifically, f4 and ft can satisfy 0.1 < |f4 / ft| < 0.95; f5 and ft can satisfy 0.01 < |f5 / ft| < 0.1.

[0048] In an exemplary embodiment, the mid-wave infrared continuous zoom lens of this application can satisfy the condition 0.01≤BFL / ft<0.3, where BFL is the distance on the optical axis from the image side of the sixth lens to the imaging plane of the mid-wave infrared continuous zoom lens, and ft is the focal length of the mid-wave infrared continuous zoom lens in telephoto mode. More specifically, BFL and ft can satisfy 0.01≤BFL / ft<0.1.

[0049] In an exemplary embodiment, the first lens in the front fixed group of the mid-wave infrared continuous zoom lens of this application can be made of silicon; the second lens in the zoom group and the fifth lens in the rear fixed group can both be made of germanium. 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 mid-wave infrared continuous zoom lens of this application can be a meniscus lens with its 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 its convex surface facing the object side; the fifth lens in the rear fixed group can be a meniscus lens with its 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, 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 of the mid-wave infrared continuous zoom lens of this application can all adopt an even-order aspherical surface.

[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 fixing group can adopt a binary surface type.

[0053] In an exemplary embodiment, during the focal length change process, the zoom group and compensation group of the mid-wave infrared continuous zoom lens of this application can perform non-linear movement along the optical axis, enabling the lens to switch between short focal length, medium focal length, and long focal length states. Exemplarily, the zoom group and compensation group can perform non-linear movement in opposite directions along the optical axis. Exemplarily, the relative movement of the zoom group and compensation group can be controlled, for example, by a cam groove provided on the lens barrel, to achieve focal length adjustment of the mid-wave infrared continuous zoom lens. Exemplarily, for example, two cam grooves can be provided on the lens barrel to respectively control the relative movement of the second lens of the zoom group and the third lens of the compensation group.

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

[0055] In an exemplary embodiment, the mid-wave infrared continuous zoom lens of this application has a short focal length of 50mm, a long focal length of 1300mm, and a zoom ratio of greater than or equal to 25x.

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

[0057] In an exemplary embodiment, the operating wavelength of the mid-wave infrared continuous zoom lens of this application is 3.7μm to 4.8μm.

[0058] In an exemplary embodiment, the detector adapted to the mid-wave infrared continuous zoom lens of this application is a cooled detector. The detector has a resolution of 640×512 and a pixel size of 15μm.

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

[0060] In summary, the mid-wave infrared continuous zoom lens provided according to the exemplary embodiments of this application adopts a six-element optical structure, can achieve 26x continuous zoom, and has an active thermal differential function, which can ensure that the lens has a stable imaging effect in a wide temperature range of -40° to +60°, and can meet the requirements of the lens for use in environments with large temperature variations.

[0061] The mid-wave infrared continuous zoom lens provided in the exemplary embodiment of this application, by employing a zoom group and compensation group movement method, not only can a 26x continuous zoom function of the optical system be achieved, but also the system length can be effectively shortened and the number of optical system lenses can be effectively controlled, thus significantly reducing costs. Simultaneously, this application uses a hybrid approach of aspherical and diffractive surfaces, which can effectively correct chromatic aberration and improve the imaging quality of the optical system. Furthermore, the reduction in the number of lenses can also significantly improve the system's transmittance.

[0062] Although exemplary structures and features of mid-wave infrared continuous zoom lenses are described herein, those skilled in the art should understand that one or more features may be omitted, substituted, or added without departing from the technical solutions claimed in this application. The above description is merely an exemplary illustration of the embodiments of this application. The scope of protection involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the technical concept of this application. For example, technical solutions formed by substituting the above-described features with technical features that have similar functions disclosed in this application (but not limited to those with similar functions).

[0063] The following is in conjunction with the appendix Figures 3 to 29 Specific embodiments of a mid-wave infrared continuous zoom lens applicable to the above-described embodiments are further described.

[0064] Example 1

[0065] The structural schematic diagram of the mid-wave infrared continuous zoom lens according to Embodiment 1 can be found here. 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 sequentially along the optical axis from the object side to the image side. 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 arranged sequentially along the optical axis from the object side to the image side; and the detector V includes E7 and E8 arranged sequentially along the optical axis from the object side to the image side. Furthermore, the mid-wave infrared continuous zoom lens may also include an image plane IMA.

[0066] Table 1 shows the basic optical parameters of the mid-wave infrared continuous zoom lens according to Embodiment 1 of this application.

[0067] Face number face shape Radius of curvature (mm) Spacing (mm) Material Diameter (mm) S1 spherical 489.27 22.16 silicon 275 S2 spherical 860.18 37.48～304.18 269 S3 aspherical -311.34 6.77 germanium 81 S4 spherical 570.23 7.26～341.90 81 S5 Binary Surface 209.69 14.77 Zinc selenide 87 S6 spherical -226.09 5.54～73.48 88 S7 aspherical 39.23 9.23 Chalcogenide Glass 42 S8 aspherical 32.29 49.17 35 S9 aspherical -54.23 4.92 germanium 12 S10 spherical -134.77 62.48 12 S11 Binary 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 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 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. The shape of each aspherical surface can be defined using, but is not limited to, the following aspherical formula:

[0070]

[0071] Where z(r) is the distance vector from the vertex of the aspherical surface at a height of r along the optical axis; c is the paraxial curvature of the aspherical surface, c = 1 / R (i.e., the paraxial curvature c is the reciprocal of the radius of curvature R in Table 1 above); k is the conic coefficient; a i These are higher-order correction coefficients for aspherical surfaces. Table 2 below shows the conic coefficients k and higher-order coefficients a4, a6, a8, a4, a5, a6, a7, a8, a9, a10, a11 for each aspherical mirror surface S3, S5, S7 to S9, and S11 in this embodiment. 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 binary surfaces, and the surface shape of the binary surfaces can be defined by, but is not limited to, the following formula:

[0076]

[0077] Where λ0 is the center wavelength during design, n0 is the refractive index corresponding to the center wavelength of the material, and

[0078]

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

[0080] Table 3 below shows the normalized radius values ​​and coefficients A1, A2, A3, and A4 values ​​of the binary surfaces S5 and S11 that can be used in this embodiment.

[0081] Face number face shape Normalized radius <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[A3]]> <![CDATA[A4]]> S5 Binary Surface 42.00 -136.49 -61.90 130.14 -67.27 S11 Binary Surface 12.00 -61.26 -10.24 37.28 -33.99

[0082] Table 3

[0083] According to Embodiment 1, the mid-wave infrared continuous zoom lens can achieve adjustment or switching between different focal length states by moving the second lens E2 of the zoom group and the third lens E3 of the compensation group along the optical axis. Schematic diagrams of the lens in short focal length, medium focal length, and long focal length states can be found in [reference needed]. Figure 2 During continuous zooming, the distances of the first lens E1 in the front fixed group and the fourth, fifth, fifth, and sixth lenses E4, E5, and E6 in the rear fixed group relative to the detectors E7 and E8 along the optical axis remain constant.

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

[0085] Depend on Figure 3 , Figure 6 and Figure 9 It is evident that, under different focal lengths, the blur radius of the mid-wave infrared continuous zoom lens according to Example 1 varies little at different field-of-view positions, which means that the aberrations of the mid-wave infrared continuous zoom lens are small at different field-of-view positions. Figure 4 , Figure 7 and Figure 10 It can be seen that, under different focal lengths, the meridional and sagittal field curvatures produced by the mid-wave infrared continuous zoom lens of Example 1 for different wavelengths of light are respectively between -1.0mm~0mm, -1.0mm~0mm, and -0.2mm~0.2mm. Figure 5 , Figure 8 and Figure 11 As can be seen, under different focal lengths, the maximum distortion of the mid-wave infrared continuous zoom lens according to Example 1 is within -2.0% to 0, which means that the mid-wave infrared continuous zoom lens can achieve small field curvature and distortion under different focal lengths. In summary, the mid-wave infrared continuous zoom lens provided in Example 1 can guarantee image quality at all focal lengths and has good imaging effect during zooming.

[0086] Example 2

[0087] The structural schematic diagram of the mid-wave infrared continuous zoom lens according to Embodiment 2 can be found here. 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 sequentially along the optical axis from the object side to the image side. 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 arranged sequentially along the optical axis from the object side to the image side; and the detector V includes E7 and E8 arranged sequentially along the optical axis from the object side to the image side. Furthermore, the mid-wave infrared continuous zoom lens may also include an image plane IMA.

[0088] Table 4 shows the basic optical parameters of the mid-wave infrared continuous zoom lens according to Embodiment 2 of this application.

[0089] Face number face shape Radius of curvature (mm) Spacing (mm) Material Diameter (mm) S1 spherical 400.30 14.5 silicon 230 S2 spherical 717.69 37～249 224 S3 aspherical -255.13 5.5 germanium 69 S4 spherical 468.49 3～269 69 S5 Binary Surface 166.09 12.0 Zinc selenide 74 S6 spherical -195.16 6～61 74 S7 aspherical 31.60 7.5 Chalcogenide Glass 36 S8 aspherical 26.70 34.54 27.2 S9 aspherical -30.51 4.0 germanium 10.8 S10 spherical -50.03 52.26 14 S11 Binary 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 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 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 formula (1) given in Embodiment 1 above. Table 5 below gives the conic coefficient k and higher-order coefficients a4, a6, a8, a4, a5, a6, a7, a8, a9, a10 ... 10 and a 12 .

[0092] Face number face shape k <![CDATA[a4]]> <![CDATA[a6]]> <![CDATA[a8]]> <![CDATA[a 10 ]]> <![CDATA[a 12 ]]> S3 aspherical -2.86 1.07E-08 1.24E-11 -1.25E-14 4.47E-18 -3.60E-22 S5 aspherical -5.30 -9.12E-08 4.51E-12 -1.61E-15 2.09E-18 -1.07E-21 S7 aspherical 0.00 2.82E-07 3.91E-10 4.56E-12 -2.33E-14 -2.16E-18 S8 aspherical 0.11 -1.52E-06 -3.55E-09 3.05E-11 -2.71E-13 1.38E-16 S9 aspherical 32.80 1.16E-04 4.54E-08 1.13E-07 -3.69E-09 7.33E-11 S11 aspherical 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 binary surfaces, and the surface shape of each binary surface can be defined by formula (2) given in embodiment 1 above. Table 6 below gives the normalized radius values ​​and coefficients A1, A2, A3, and A4 values ​​of the binary surfaces S5 and S11 that can be used in this embodiment.

[0095] Face number face shape Normalized radius <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[A3]]> <![CDATA[A4]]> S5 Binary Surface 40.00 -151.99 -32.58 104.77 -75.69 S11 Binary Surface 13.00 -106.52 -39.28 264.38 -322.51

[0096] Table 6

[0097] According to Embodiment 2, the mid-wave infrared continuous zoom lens can achieve adjustment or switching between different focal length states by moving the second lens E2 of the zoom group and the third lens E3 of the compensation group along the optical axis. Schematic diagrams of the lens in short focal length, medium focal length, and long focal length states can be found in [reference needed]. Figure 2During continuous zooming, the distances of the first lens E1 in the front fixed group and the fourth, fifth, fifth, and sixth lenses E4, E5, and E6 in the rear fixed group relative to the detectors E7 and E8 along the optical axis remain constant.

[0098] Figure 12 , Figure 13 and Figure 14 The blur pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Example 2 are shown respectively in the short focal length state; Figure 15 , Figure 16 and Figure 17 The blur pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Example 2 at mid-focus are shown respectively; and Figure 18 , Figure 19 and Figure 20 The diffusion pattern, field curvature curve, and distortion curve of the mid-wave infrared continuous zoom lens according to Example 2 in telephoto mode are shown respectively.

[0099] Depend on Figure 12 , Figure 15 and Figure 18 It is evident that, under different focal lengths, the blur radius of the mid-wave infrared continuous zoom lens according to Example 2 varies little at different field-of-view positions, which means that the aberrations of the mid-wave infrared continuous zoom lens are small at different field-of-view positions. Figure 13 , Figure 16 and Figure 19 It can be seen that, under different focal lengths, the meridional and sagittal field curvatures produced by the mid-wave infrared continuous zoom lens of Example 2 for different wavelengths of light are respectively between -1.0mm to 0mm, 0mm to 0.5mm, and 0mm to 1.0mm. Figure 14 , Figure 17 and Figure 20 As can be seen, under different focal lengths, the maximum distortion of the mid-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. This means that the mid-wave infrared continuous zoom lens can achieve small field curvature and distortion under different focal lengths. In summary, the mid-wave infrared continuous zoom lens provided in Example 2 can guarantee imaging quality at all focal lengths and has good imaging effect during zooming.

[0100] Example 3

[0101] The structural schematic diagram of the mid-wave infrared continuous zoom lens according to Embodiment 3 can be found here. Figure 1Specifically, 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 sequentially along the optical axis from the object side to the image side. 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 arranged sequentially along the optical axis from the object side to the image side; and the detector V includes E7 and E8 arranged sequentially along the optical axis from the object side to the image side. Furthermore, the mid-wave infrared continuous zoom lens may also include an image plane IMA.

[0102] Table 7 shows the basic optical parameters of the mid-wave infrared continuous zoom lens according to Embodiment 3 of this application.

[0103] Face number face shape Radius of curvature (mm) Spacing (mm) Material Diameter (mm) S1 spherical 188.13 8.61 silicon 123 S2 spherical 328.20 16.11～118.28 121 S3 aspherical -111.55 2.63 germanium 38 S4 spherical 255.73 3.1～131.79 39 S5 Binary Surface 85.54 5.74 Zinc selenide 43 S6 spherical -83.69 2.26～29.34 43 S7 aspherical 15.12 3.59 Chalcogenide Glass 21 S8 aspherical 12.51 18.95 18 S9 aspherical -11.39 1.91 germanium 7 S10 spherical -15.35 22.33 8 S11 Binary 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 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 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 formula (1) given in Embodiment 1 above. Table 8 below gives the conic coefficient k and higher-order coefficients a4, a6, a8, a4, a5, a6, a7, a8, a9, a10 ... 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 binary surfaces, and the surface shape of each binary surface can be defined by formula (2) given in embodiment 1 above. Table 9 below gives the normalized radius values ​​and coefficients A1, A2, A3, and A4 values ​​of the binary surfaces S5 and S11 that can be used in this embodiment.

[0110] Face number face shape Normalized radius <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[A3]]> <![CDATA[A4]]> S5 Binary Surface 19.1 -77.20 -19.10 47.86 -22.98 S11 Binary Surface 6.2 -30.48 -7.59 21.93 -11.85

[0111] Table 9

[0112] According to Embodiment 3, the mid-wave infrared continuous zoom lens can achieve adjustment or switching between different focal length states by moving the second lens E2 of the zoom group and the third lens E3 of the compensation group along the optical axis. Schematic diagrams of the lens in short focal length, medium focal length, and long focal length states can be found in [reference needed]. Figure 2During continuous zooming, the distances of the first lens E1 in the front fixed group and the fourth, fifth, fifth, and sixth lenses E4, E5, and E6 in the rear fixed group relative to the detectors E7 and E8 along the optical axis remain constant.

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

[0114] Depend on Figure 21 , Figure 24 and Figure 27 It is evident that, under different focal lengths, the blur radius of the mid-wave infrared continuous zoom lens according to Example 3 varies little at different field-of-view positions, which means that the aberrations of the mid-wave infrared continuous zoom lens are small at different field-of-view positions. Figure 22 , Figure 25 and Figure 28 It can be seen that, under different focal lengths, the meridional and sagittal field curvatures produced by the mid-wave infrared continuous zoom lens of Example 3 for different wavelengths of light are respectively between -0.5mm~0.5mm, -1.0mm~1.0mm, and -1.0mm~1.0mm. Figure 23 , Figure 26 and Figure 29 As can be seen, under different focal lengths, the maximum distortion of the mid-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. This means that the mid-wave infrared continuous zoom lens can achieve small field curvature and distortion under different focal lengths. In summary, the mid-wave infrared continuous zoom lens provided in Example 3 can guarantee imaging quality at all focal lengths and has good imaging effect during zooming.

[0115] Furthermore, Examples 1 to 3 respectively satisfy the conditions shown in Table 10 below.

[0116]

[0117]

[0118] Table 10

[0119] This application also provides an imaging device equipped with an electronic photosensitive element for imaging, wherein the electronic photosensitive element may be a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS). The imaging device is fitted with the mid-wave infrared continuous zoom lens described above.

[0120] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of protection involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the concept of this application. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. A mid-wave infrared continuous zoom lens, characterized in that, Along the optical axis from the object side to the image side, it includes, in sequence: a front fixation group, a zoom group, a compensation group, a rear fixation group, and a detector. The front fixation 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 assembly includes a fourth lens with positive or negative optical power, a fifth lens with negative optical power, and a sixth lens with positive optical power. The zoom group and the compensation group are adjustable in distance from the detector in the optical axis direction, while the front fixed group and the rear fixed group are fixed in position relative to the detector in the optical axis direction. The number of lenses with optical power in the mid-wave infrared continuous zoom lens is six; The object-side surface of the first lens is convex, and the image-side surface is concave. The object-side surface of the second lens is concave, and the image-side surface is also concave. The object-side surface of the third lens is convex, and the image-side surface is also convex. The object-side surface of the fourth lens is convex, and the image-side surface is concave. The object-side surface of the fifth lens is concave, and the image-side surface is convex. The object-side surface of the sixth lens is convex. The radius of curvature R2 of the image side of the first lens and the radius of curvature R1 of the object side of the first lens satisfy: 1≤R2 / R1≤3.

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

3.

4. The mid-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 mid-wave infrared continuous zoom lens in telephoto mode respectively satisfy the following: 0.03 < |f4 / ft| < 0.95; 0.01 < |f5 / ft| < 0.2; as well as 0.01≤|f6 / ft|<0.

1.

5. The mid-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 mid-wave infrared continuous zoom lens on the optical axis satisfies the following condition: 0.01≤BFL / ft<0.

3.

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

7. The mid-wave infrared continuous zoom lens according to claim 1, characterized in that, The object-side surface of the second lens, the object-side surface and the image-side surface of the fourth lens, and the object-side surface of the fifth lens are all of even order aspherical surface type; the object-side surface of the third lens and the object-side surface of the sixth lens are of binary surface type.

8. The mid-wave infrared continuous zoom lens according to claim 1, characterized in that, The mid-wave infrared continuous zoom lens includes a lens barrel with a cam curve groove, wherein the zoom group and the compensation group move non-linearly along the optical axis via the cam curve groove, so that the mid-wave infrared continuous zoom lens switches between short focal length, medium focal length and long focal length.

9. The mid-wave infrared continuous zoom lens according to claim 1, characterized in that, The mid-wave infrared continuous zoom lens has a short focal length range of 20mm to 60mm, a long focal length range of 600mm to 1550mm, and a zoom ratio of ≥20x.

10. The mid-wave infrared continuous zoom lens according to claim 1, characterized in that, The mid-wave infrared continuous zoom lens has a short focal length of 50mm, a long focal length of 1300mm, and a zoom ratio of ≥25x.

11. The mid-wave infrared continuous zoom lens according to claim 1, characterized in that, The working aperture F-number of the mid-wave infrared continuous zoom lens is 5.5, and the detector is a cooled detector.

12. The mid-wave infrared continuous zoom lens according to claim 1, characterized in that, The horizontal field of view of the mid-wave infrared continuous zoom lens ranges from 0.4° to 10.9°.

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