Infrared continuous zoom imaging lens and infrared thermal imaging system

Abstract

The application discloses an infrared continuous zoom imaging lens and an infrared thermal imaging system. The infrared continuous zoom imaging lens comprises a front fixed group, a zoom group, a compensation group and a rear fixed group arranged in sequence along an optical axis from an object side to an image side, wherein the zoom group and the compensation group move along the optical axis during zooming of the imaging lens. The front fixed group comprises a first lens with positive refractive power and a second lens with negative refractive power; the zoom group comprises a third lens with negative refractive power; the compensation group comprises a fourth lens with positive refractive power; and the rear fixed group comprises a fifth lens and a sixth lens with positive refractive power. The radius of curvature R1 of the first lens towards the object side and the radius of curvature R2 of the first lens towards the image side satisfy 3 < R2 / R1 < 4. The application adopts the moving mode of the zoom group and the compensation group, can realize high-multiple continuous zooming function, effectively shortens the system length, controls the number of optical system lenses and greatly reduces the cost through the zooming mode.

Description

Technical Field

[0001] This application relates to the field of optical components, and more specifically, to an infrared continuous zoom imaging lens and an infrared thermal imaging system. Background Technology

[0002] With the continuous development of infrared thermal imaging theory, the application of infrared thermal imaging lenses is becoming increasingly widespread. Because of its unique ability to image by relying on the thermal radiation of natural objects, infrared thermal imaging systems can achieve many functions that visible light systems cannot, leading to increasing attention being paid to their application in the civilian sector.

[0003] Due to the limitations of fixed-focus infrared thermal imaging systems, they cannot effectively perform tasks in some complex scenarios. Continuous zoom lenses, on the other hand, possess the ability to switch between different fields of view, enabling large-field-of-view search and precise positioning in small-field-of-view scenarios. If continuous zoom lenses can be fully applied in complex environments, they will be more widely adopted in fields such as airport monitoring, railway safety, forest fire prevention, and life detection, showing broad application prospects.

[0004] Most existing medium-wave high zoom ratio continuous zoom lenses are large in size or have the same number of lenses, which cannot achieve the required high zoom ratio, thus limiting the application of zoom imaging lenses. Summary of the Invention

[0005] One aspect of this application provides an infrared continuous zoom imaging lens, comprising: a front fixed group, a zoom group, a compensation group, and a rear fixed group arranged sequentially along an optical axis from the object side to the image side, wherein the zoom group and the compensation group move along the optical axis during the zooming process of the imaging lens; the front fixed group includes a first lens with positive optical power and a second lens with negative optical power; the zoom group includes a third lens with negative optical power; the compensation group includes a fourth lens with positive optical power; and the rear fixed group includes a fifth lens and a sixth lens with positive optical power; wherein the radius of curvature R1 of the first lens facing the object side and the radius of curvature R2 of the first lens facing the image side satisfy the following relationship: 3 <R2 / R1<4。

[0006] In some embodiments, the focal length ft of the imaging lens in its telephoto state, the refractive index n of the first lens material at the center wavelength, the F-number FNO of the imaging lens, and R1 satisfy: 2 <ft*(n-1) / (FNO*R1)<3。

[0007] In some embodiments, the effective focal lengths f1 to f6 of the first to sixth lenses and ft respectively satisfy: 0.1 < |f1 / ft| < 0.5; 0.1 < |f2 / ft| < 0.5; 0.01 < |f3 / ft| < 0.5; 0.03 < |f4 / ft| < 0.5; 0.15 < |f5 / ft| < 1.0; and 0.15 < |f6 / ft| < 1.2.

[0008] In some implementations, the back focal length BFL of the imaging lens satisfies 0.01 with respect to ft. <BFL / ft<0.5。

[0009] In some embodiments, the first lens is made of silicon; and the second, third, fourth, fifth and sixth lenses are made of materials with a refractive index ranging from 2.3 to 4.5.

[0010] In some embodiments, the first lens is a meniscus lens with its convex surface facing the object side; the second lens is a meniscus lens with its convex surface facing the object side; the third lens is a biconcave lens; the fourth lens is a biconvex lens; the fifth lens is a meniscus lens with its convex surface facing the object side; and the sixth lens is a biconvex lens. The image-side surface of the second lens, the object-side surface of the third lens, the image-side surface of the fourth lens, and the image-side and object-side surfaces of the fifth lens are all of even order aspherical surface type, and the object-side surface of the fourth lens and the image-side surface of the sixth lens are of binary surface type.

[0011] In some implementations, the surface shape of an even-order aspherical surface satisfies the following equation:

[0012]

[0013] Where z is the distance from the even-order aspherical surface to the vertex of the even-order aspherical surface along the optical axis, r is the height from the optical axis, c is the curvature, c = 1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, and a2, a3, a4, and a5 are the higher-order coefficients of the aspherical surface.

[0014] In some implementations, the shape of the binary surface satisfies the following equation:

[0015]

[0016] Where z is the distance from the binary surface along the optical axis to the vertex of the even-order aspherical surface, r is the height from the optical axis, c is the curvature, c = 1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, a2, a3, a4, and a5 are the higher-order coefficients of the aspherical surface; λ0 is the center wavelength during design, and n0 is the refractive index corresponding to the center wavelength of the lens material.

[0017]

[0018] Where M is the diffraction order, N is the order of the polynomial coefficients in the series, and A i Yes, the coefficient of the 2ith power, where ρ is the normalized radial aperture coordinate.

[0019] In some implementations, during the change of focal length of the imaging lens, the zoom group and the compensation group move nonlinearly along the optical axis in opposite or opposite directions.

[0020] In some implementations, the zoom range of the imaging lens is f12mm to f340mm.

[0021] One aspect of this application provides an infrared thermal imaging system, including an infrared continuous zoom imaging lens as described above and a mid-wave uncooled detector, the mid-wave uncooled detector being located on the image side of the infrared continuous zoom imaging lens.

[0022] The infrared continuous zoom imaging lens provided in this application employs a zoom group and compensation group movement method to achieve high-magnification continuous zoom functionality. Furthermore, this application effectively shortens the system length and controls the number of optical system lenses through this zoom method, significantly reducing costs.

[0023] In addition, this application uses a combination of aspherical and diffractive surfaces to 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 system's transmittance. Attached Figure Description

[0024] Other features, objects, and advantages of this utility application will become more apparent from the following detailed description of the embodiments, taken in conjunction with the accompanying drawings. In the drawings:

[0025] Figure 1 This is a schematic diagram of the structure of an infrared thermal imaging system according to an exemplary embodiment of this application;

[0026] Figure 2 yes Figure 1 The diagram shows the zoom process of an infrared continuous zoom imaging lens.

[0027] Figure 3 This is the MTF diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the short focal length state;

[0028] Figure 4 This is a blur pattern of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in a short focal length state;

[0029] Figure 5 This is a field curvature distortion diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in a short focal length state;

[0030] Figure 6This is the MTF diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the mid-focus state;

[0031] Figure 7 This is a blur pattern of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the mid-focus state;

[0032] Figure 8 This is a field curvature distortion diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the mid-focus state;

[0033] Figure 9 This is the MTF diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the telephoto state;

[0034] Figure 10 This is the blur pattern of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the telephoto state; and

[0035] Figure 11 This is a field curvature distortion diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the telephoto state. Detailed Implementation

[0036] To facilitate understanding of this application, a more complete description of the application will be provided below with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely illustrative of exemplary embodiments of the application and are not intended to limit the scope of the 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.

[0037] It should be noted that in this specification, the terms "first," "second," 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, and vice versa.

[0038] In the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical or aspherical surfaces shown in the drawings are illustrated by way of example. That is, the shapes of the spherical or aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustrative purposes only and are not strictly to scale.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.

[0043] Figure 1 This is a schematic diagram of the structure of an infrared thermal imaging system provided in an exemplary embodiment of this application. (Reference) Figure 1 The infrared thermal imaging system includes an infrared continuous zoom imaging lens 100 and a mid-wave uncooled detector 200. The infrared continuous zoom imaging lens 100, along the optical axis from the object side to the image side, includes a front fixed group 10, a zoom group 20, a compensation group 30, and a rear fixed group 40. The front fixed group 10 includes a first lens 11 and a second lens 12; the zoom group 20 includes a third lens 21; the compensation group 30 includes a fourth lens 31; and the rear fixed group 40 includes a fifth lens 41 and a sixth lens 42. In some embodiments, the first lens 11, the fourth lens 31, the fifth lens 41, and the sixth lens 42 may all have positive optical power, and the second lens 12 and the third lens 21 may have negative optical power. When the infrared continuous zoom imaging lens 100 is in different focal length states, the positions of the zoom group 20 and the compensation group 30 along the optical axis will be different, while the positions of the front fixed group 10 and the rear fixed group 40 along the optical axis will be fixed. Figure 2 As shown.

[0044] As the zoom group 20 and the compensation group 30 move along the optical axis, the focal length of the infrared continuous zoom imaging lens 100 can continuously change within the range of 12mm to 340mm. During the movement of the zoom group 20 and the compensation group 30 along the optical axis, the distance between them changes accordingly. In an exemplary embodiment, the infrared continuous zoom imaging lens 100 can have its minimum focal length when the distance between the zoom group 20 and the compensation group 30 is at its maximum value, and its maximum focal length when the distance between them is at its minimum value.

[0045] As can be understood, optical power equals the difference between the convergence of the image-side beam and the convergence of the object-side beam; it characterizes the ability of an optical system to deflect light. The larger the absolute value of optical power, the stronger the bending ability of light; the smaller the absolute value, the weaker the bending ability. When optical power is positive, the refraction of light is converging; when optical power is negative, the refraction of light is diverging. Optical power can be used to characterize a single refractive surface of a lens (i.e., one surface of the lens), a single lens or lens group, or a system composed of multiple lenses (i.e., a group or lens assembly).

[0046] In this embodiment, the front fixed group 10, the zoom group 20, the compensation group 30, and the rear fixed group 40 can be arranged in a lens barrel. The front fixed group 10 and the rear fixed group 40 are fixed in position within the lens barrel, while the zoom group 20 and the compensation group 30 can move along the optical axis within the lens barrel, thereby achieving a change in focal length. For example, the relative movement of the zoom group 20 and the compensation group 30 can be controlled by providing three cam grooves on the inside of the lens barrel, respectively.

[0047] The focal length of the lens can be adjusted by moving the zoom group 20, thus achieving focal length changes in this infrared continuous zoom imaging lens. The compensation group 30 is used to compensate for aberrations caused during the movement of the zoom group 20. It can be understood that during the zoom process achieved by moving the corresponding group, the infrared continuous zoom imaging lens can be divided into three states based on the focal length: short focal length, medium focal length, and long focal length.

[0048] In the embodiments of the present application, the front fixed group 10 is configured to include a first lens 11 with positive optical power and a second lens 12 with negative optical power, the zoom group 20 includes a third lens 21 with negative optical power, the compensation group 30 includes a fourth lens 31 with positive optical power, and the rear fixed group 40 includes a fifth lens 41 and a sixth lens 42 both with positive optical power. The present application utilizes the optical power cooperation of six lenses, and can realize effective compensation for the aberration caused during the zoom movement of the third lens 21 through the position adjustment and mutual cooperation of the two lenses, the third lens 21 and the fourth lens 31, so as to achieve 28X continuous zoom, and has an active athermalization function, which can ensure the lens has a stable imaging effect in a wide temperature range of -40° to +80°, and further meet the requirements for the lens to be used in environments with large temperature changes. Moreover, by adopting the manner of moving the zoom group 20 and the compensation group 30, the lens length can be effectively shortened, the number of lenses of the lens can be controlled, and the cost can be greatly reduced.

[0049] In addition, the relationship between the curvature radius R1 of the object side of the first lens 11 and the curvature radius R2 of the image side of the first lens 11 satisfies: 3<R2 / R1<4. Illustratively, the relationship between R1 and R2 satisfies: 3.5<R2 / R1<4. At this time, when the first lens is a spherical lens and cooperates with the above limitation on the curvature radius, the first lens 11 has a specific meniscus shape, which can ensure positive optical power while providing an appropriate and stable light converging effect, and as a basis, realize corresponding optical power cooperation with other lens groups to support the moving zoom of the zoom group and the compensation group.

[0050] Figure 2 is Figure 1 a schematic diagram of the zoom process of the infrared continuous zoom imaging lens shown, with reference Figure 2 , during the focal length change process, the compensation group 30 and the zoom group 20 perform non-linear motion along the opposite direction or the opposite direction on the optical axis.

[0051] Specifically, when transitioning from the short focal state to the medium focal state or from the medium focal state to the telephoto state, the zoom group 20 (the third lens 21) moves toward the image side on the optical axis, and the corresponding position of the compensation group 30 (the fourth lens 31) needs to move toward the object side. At this time, in essence, the distance between the zoom group 20 and the front fixed group 10 and the distance between the compensation group 30 and the rear fixed group 40 are extended, while the distance between the compensation group 30 and the zoom group 20 is shortened. When the zoom group 20 moves toward the image side, its diverging effect on the light beam emitted from the front fixed group 10 is relatively delayed. By moving the compensation group 30 toward the object side by a corresponding distance, the sequence time of the light beam converging effect exerted by the compensation group can be changed, thereby changing the light beam converging effect of the entire lens, so as to realize the expansion of the overall focal length.

[0052] On the contrary, when transitioning from the telephoto state to the medium focal state or from the medium focal state to the short focal state, the zoom group 20 moves toward the object side on the optical axis, and the position of the corresponding compensation group 30 needs to move toward the image side, so as to achieve the reduction of the overall focal length. It should be noted that in the actual use process, the movement of the zoom group 20 and the compensation group 30 in the infrared continuous zoom imaging lens needs to be synchronously driven according to the determined positional relationship to ensure real-time image clarity during the zoom process.

[0053] In some embodiments, the focal length of each lens in the infrared continuous zoom imaging lens satisfies the following conditions: 0.1<|f1 / ft|<0.5; 0.1<|f2 / ft|<0.5; 0.01<|f3 / ft|<0.5; 0.03<|f4 / ft|<0.5; 0.15<|f5 / ft|<1.0; and 0.15<|f6 / ft|<1.2. Wherein, ft is the focal length of the infrared continuous zoom imaging lens in the long focal length state; f1 to f6 are respectively the effective focal lengths of the first lens 11 to the sixth lens 42. The above design of the lenses is mainly used to limit the role of each lens in its respective group, ensure the mutual cooperation of each lens, and realize zooming and clear imaging.

[0054] In some embodiments, the infrared continuous zoom imaging lens satisfies the following conditions: 2<ft*(n-1) / (FNO*R1)<3; 0.01<BFL / ft<0.5. Wherein, n is the refractive index of the material of the first lens 11 at the central wavelength; FNO is the F-number of the infrared continuous zoom imaging lens; R1 is the curvature radius of the object-side surface of the first lens 11; BFL is the back focal length of the infrared continuous zoom imaging lens.

[0055] In some embodiments, the first lens 11 is a meniscus positive lens with its convex surface facing the object side; the second lens 12 is a meniscus negative lens with its convex surface facing the object side; the third lens 21 is a biconcave negative lens; the fourth lens 31 is a biconvex positive lens; the fifth lens 41 is a meniscus positive lens with its convex surface facing the object side; and the sixth lens 42 is a biconvex positive lens.

[0056] The image-side surface of the second lens 12, the object-side surface of the third lens 21, the object-side surface and image-side surface of the fourth lens 31, the image-side surface and object-side surface of the fifth lens 41, and the image-side surface of the sixth lens 42 all adopt aspheric surfaces, and all the remaining surfaces are spherical surfaces.

[0057] Exemplarily, the image-side surface of the second lens 12, the object-side surface of the third lens 21, the image-side surface of the fourth lens 31, and the image-side surface and object-side surface of the fifth lens 41 all adopt even aspheric surface profiles, and the object-side surface of the fourth lens 31 and the image-side surface of the sixth lens 42 adopt diffractive optical elements.

[0058] In this embodiment, the image-side surface of the second lens 12, the object-side surface of the third lens 21, the object-side and image-side surfaces of the fourth lens 31, the image-side and object-side surfaces of the fifth lens 41, and the image-side surface of the sixth lens 42 are all set as aspherical surfaces. Furthermore, the object-side surface of the fourth lens 31 and the image-side surface of the sixth lens 42 are set as binary surfaces, i.e., diffraction surfaces.

[0059] In the above-mentioned scheme, this application adopts a combination of aspherical and diffractive surfaces, which can effectively correct chromatic aberration, improve the imaging quality of infrared continuous zoom imaging lens, reduce the number of lenses, and also improve the transmittance of infrared continuous zoom imaging lens.

[0060] For example, the surface shape of the above even-order aspherical surface satisfies the following equation:

[0061]

[0062] Where z is the distance from the even-order aspherical surface to the vertex of the even-order aspherical surface along the optical axis, r is the height from the optical axis, c is the curvature, c = 1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, and a2, a3, a4, and a5 are the higher-order coefficients of the aspherical surface.

[0063] The surface shape of the aforementioned binary surface satisfies the following equation:

[0064]

[0065] Where z is the distance from the binary surface along the optical axis to the vertex of the even-order aspherical surface, r is the height from the optical axis, c is the curvature, c = 1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, a2, a3, a4, and a5 are the higher-order coefficients of the aspherical surface; λ0 is the center wavelength during design, and n0 is the refractive index corresponding to the center wavelength of the lens material.

[0066]

[0067] Where M is the diffraction order, N is the order of the polynomial coefficients in the series, and A i Yes, the coefficient of the 2ith power, where ρ is the normalized radial aperture coordinate.

[0068] In some embodiments, the first lens 11 is made of silicon; the second lens 12, the third lens 21, the fourth lens 31, the fifth lens 41 and the sixth lens 42 are made of materials with a refractive index ranging from 2.3 to 4.5.

[0069] Optionally, the first lens 11, the third lens 21 and the sixth lens 42 may be made of silicon (SI), the second lens 12 and the fifth lens 41 may be made of germanium (GE), and the fourth lens 31 may be made of zinc selenide (ZNSE).

[0070] In a specific embodiment of this application, the working band of the infrared continuous zoom imaging lens can be set to 3.7μm to 4.8μm, the zoom ratio is 28X, and the zoom range is f12mm to f340mm. The F number is fixed at 4, and it is compatible with a 640*512_15μm mid-wave uncooled detector with a horizontal field of view of 44.8° to 1.6°.

[0071] Compared to existing mid-wave zoom lenses, the infrared continuous zoom imaging lens provided in this application achieves continuous zoom functionality for a 28X optical system by employing a zoom group and compensation group movement method. Furthermore, this zoom method effectively shortens the system length, controls the number of optical system lenses, and significantly reduces costs. In addition, this application uses a hybrid approach of aspherical and diffractive surfaces to effectively correct chromatic aberration and improve the imaging quality of the optical system. Simultaneously, the reduction in the number of lenses also significantly improves the system's transmittance.

[0072] Based on the same inventive concept, this application also provides an infrared thermal imaging system, which will be discussed further below. Figure 1 The infrared thermal imaging system includes an infrared continuous zoom imaging lens 100 provided in any embodiment of this application, and also includes a mid-wave uncooled detector 200 located on the image side of the infrared continuous zoom imaging lens 100. The operating wavelength of the infrared continuous zoom imaging lens 100 can be set to 3.7μm to 4.8μm, with a zoom ratio of 28X, and a zoom range of f12mm to f340mm. The F-number is fixed at 4, and it is compatible with a 640*512_15μm mid-wave uncooled detector, with a horizontal field of view of 44.8° to 1.6°. Furthermore, since this infrared thermal imaging system includes any one of the infrared continuous zoom imaging lenses 100 provided in the above embodiments, it possesses the same or similar technical effects as the aforementioned infrared continuous zoom imaging lens 100, which will not be elaborated further here.

[0073] Specific embodiments of the optical system applicable to the above-described embodiments are further described below with reference to the accompanying drawings.

[0074] Example 1

[0075] The following is for reference Figures 3 to 11 An infrared thermal imaging system according to Embodiment 1 of this application is described.

[0076] like Figure 1As shown, the infrared thermal imaging system includes an infrared continuous zoom imaging lens 100 and a mid-wave uncooled detector 200, with the mid-wave uncooled detector 200 located on the image side of the infrared continuous zoom imaging lens 100. The infrared continuous zoom imaging lens 100, along the optical axis from the object side to the image side, sequentially includes a front fixed group 10, a zoom group 20, a compensation group 30, and a rear fixed group 40. The front fixed group 10 includes a first lens 11 with positive optical power and a second lens 12 with negative optical power; the zoom group 20 includes a third lens 21 with negative optical power; the compensation group 30 includes a fourth lens 31 with positive optical power; and the rear fixed group 40 includes a fifth lens 41 and a sixth lens 42 with positive optical power. The zoom group 20 and the compensation group 30 move synchronously along the optical axis during zooming, while the front fixed group 10 and the rear fixed group 40 are fixed relative to the mid-wave uncooled detector 200. The medium-wave uncooled detector 200 includes a first medium-wave uncooled detector window 201 and a second medium-wave uncooled detector window 202, which are respectively disposed on both sides of the aperture.

[0077] Table 1 is the optical parameter table of the infrared thermal imaging system provided in Embodiment 1 of this application, Table 2 is the aspherical high-order coefficient table, and Table 3 is the binary surface coefficient table.

[0078] S1 spherical 80.539 5～15 n＝3.4 38.6 S2 spherical 312.354 2～10 36.2 S3 spherical 858.457 2～6 n＝4 35.3 S4 aspherical 252.529 1～40 32.8 S5 aspherical -56.173 1.5～6.5 n＝3.4 12.55 S6 spherical 43.328 1～60 12.55 S7 Binary Surface 55.918 2.5～9 n＝2.3 13.8 S8 aspherical -44.056 1.5～30 13.8 S9 aspherical 10.309 2～10 n＝4 7.2 S10 aspherical 6.327 15～25 4.6 S11 spherical 55.33 1～8 n＝3.4 8.5 S12 Binary Surface -25.159 1～10 8.5 S13 spherical infinity 1 silicon - S14 spherical infinity 2.85 - S15 aperture infinity - - S16 spherical infinity 0.3 germanium - S17 spherical infinity 0.57 - IMA flat infinity - -

[0079] Table 1

[0080] S4 aspherical 0 3.36-08 -1.09E-11 -3.03E-15 2.37E-18 S5 aspherical 0 1.59E-05 -2.38E-08 6.54E-11 -1.12E-13 S7 Binary Surface 0 2.56E-06 -3.36E-08 -3.29E-12 3.07E-14 S8 aspherical 0 1.14E-05 -3.10E-08 0.00E+00 0.00E+00 S9 aspherical 0 -2.67E-05 -4.73E-07 0.00E+00 0.00E+00 S10 aspherical 0 -2.54E-04 -9.56E-06 1.78E-07 -3.67E-09 S12 Binary Surface 0 8.39E-05 -3.50E-07 1.79E-09 -2.36E-12

[0081] Table 2

[0082] S7 Binary Surface 15 -126.369 15.357 S12 Binary Surface 8 -49.537 3.565

[0083] Table 3

[0084] The surface numbers in Tables 1, 2, and 3 are sequentially numbered according to the surface order of each lens. "S1" represents the object-side surface of the first lens, "S2" represents the image-side surface of the first lens, and so on. The radius of curvature represents the degree of curvature of the lens surface; a positive value indicates that the surface bends towards the image side, and a negative value indicates that the surface bends towards the object side. "Infinity" indicates that the radius of curvature is infinite, meaning the surface is planar. The spacing represents the axial distance between the current surface and the next surface. It can be understood that since the zoom group and compensation group need to move back and forth along the optical axis, the distance between the surface and the next surface is a range value. Furthermore, in this embodiment 1, n represents the refractive index of each lens, representing its ability to deflect light. A blank space indicates that the current position is air, with a refractive index of 1.

[0085] Figures 3 to 5 These are the MTF diagram, speckle and field curvature diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the short focal length state. Figures 6 to 8These are the MTF chart, speckle and field curvature diagrams of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the mid-focus state. Figures 9 to 11 These are the MTF diagram, speckle and field curvature diagram of the infrared continuous zoom imaging lens provided in Embodiment 1 of this application in the telephoto state.

[0086] contrast Figure 3 , Figure 6 and Figure 9 At different focal lengths, the transfer function of this infrared continuous zoom imaging lens is around 0.2, which indicates that the zoom lens can achieve good resolution in both the central and peripheral fields of view, and can meet the resolution requirements of large fields of view and large target surfaces.

[0087] contrast Figure 4 , Figure 7 and Figure 10 Under different focal lengths, the radius of the blur spot of this infrared continuous zoom imaging lens changes little at different field-of-view positions, indicating that the aberration of the zoom lens is small at different field-of-view positions.

[0088] contrast Figure 5 , Figure 8 , Figure 11 The field curvature and distortion shown indicate that, under different focal lengths, the distortion of this infrared continuous zoom imaging lens is less than -5%, and the field curvature in the meridional and sagittal directions for different wavelengths of light is between ±0.6mm. This means that the zoom lens can achieve small distortion and field curvature under different focal lengths.

[0089] In summary, the infrared continuous zoom imaging lens provided in this embodiment 1 has well corrected aberrations at each focal length, has good MTF, and the blur spots are within the pixel range, thus achieving the correction of various aberrations and ensuring imaging quality at each focal length. In other words, the infrared continuous zoom imaging lens provided in this embodiment 1 has good imaging effect during zooming.

[0090] 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 the invention 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 inventive concept. For example, technical solutions formed by substituting the above-described features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An infrared continuous zoom imaging lens, characterized in that, include: A front fixed group, a zoom group, a compensation group, and a rear fixed group are arranged sequentially from the object side to the image side along the optical axis. The zoom group and the compensation group move along the optical axis during the zooming process of the imaging lens. The front fixed assembly includes a first lens with positive optical power and a second lens with negative optical power; The zoom group includes a third lens with negative optical power; The compensation group includes a fourth lens with positive optical power; and The rear fixation group includes a fifth lens with negative optical power and a sixth lens with positive optical power; The first lens is a meniscus lens with its convex surface facing the object side; The second lens is a meniscus lens with its convex surface facing the object side; The third lens is a biconcave lens; The fourth lens is a biconvex lens; The fifth lens is a meniscus lens with its convex surface facing the object side; and The sixth lens is a biconvex lens; The infrared continuous zoom imaging lens has six lenses with optical power. Wherein, the radius of curvature R1 of the first lens facing the object side and the radius of curvature R2 of the first lens facing the image side satisfy the following relationship: 3 <R2 / R1<4。 2. The infrared continuous zoom imaging lens according to claim 1, wherein, The focal length ft of the imaging lens in telephoto mode, the refractive index n of the first lens material at the center wavelength, and the F-number FNO and R1 of the imaging lens satisfy: 2 <ft (n-1) / (FNO R1)<3.

3. The infrared continuous zoom imaging lens according to claim 2, wherein, The effective focal lengths f1 to f6 of the first lens to the sixth lens respectively satisfy the following conditions: 0.1 < |f1 / ft| < 0.5; 0.1 < |f² / ft| < 0.5; 0.01 < |f3 / ft| < 0.5; 0.03 < |f4 / ft| < 0.5; 0.15 < |f5 / ft| < 1.0; and 0.15 < |f6 / ft| < 1.

2.

4. The infrared continuous zoom imaging lens according to claim 2, wherein, The back focal length BFL of the imaging lens satisfies 0.01 with respect to ft. <BFL / ft<0.5。 5. The infrared continuous zoom imaging lens according to claim 1, wherein, The first lens is made of silicon material; and The refractive index of the materials used for the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens ranges from 2.3 to 4.

5.

6. The infrared continuous zoom imaging lens according to claim 1, wherein, The image-side surface of the second lens, the object-side surface of the third lens, the image-side surface of the fourth lens, and the image-side and object-side surfaces of the fifth lens are all of even order aspherical surface type, and the object-side surface of the fourth lens and the image-side surface of the sixth lens are of binary surface type.

7. The infrared continuous zoom imaging lens according to claim 6, wherein, The surface shape of the even-order aspherical surface satisfies the following equation: Where z is the distance from the even-order aspherical surface to the vertex of the even-order aspherical surface along the optical axis, r is the height from the optical axis, c is the curvature, c=1 / R, and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, and a2, a3, a4, and a5 are the higher-order coefficients of the aspherical surface.

8. The infrared continuous zoom imaging lens according to claim 6, wherein, The shape of the binary surface satisfies the following equation: Where z is the distance from the vertex of the binary surface along the optical axis, r is the height from the optical axis, c is the curvature (c = 1 / R), and R is the radius of curvature at the vertex of the lens; k is the conic coefficient, a2, a3, a4, and a5 are aspherical higher-order coefficients; λ0 is the center wavelength during design, and n0 is the refractive index corresponding to the center wavelength of the lens material. Where M is the diffraction order, N is the order of the polynomial coefficients in the series, and A i Yes, the coefficient of the 2ith power, where ρ is the normalized radial aperture coordinate.

9. The infrared continuous zoom imaging lens according to claim 1, wherein, During the focal length change of the imaging lens, the zoom group and the compensation group move nonlinearly along the optical axis in opposite or opposite directions.

10. The infrared continuous zoom imaging lens according to claim 9, wherein, The zoom range of the imaging lens is 12mm to 340mm.

11. An infrared thermal imaging system, characterized in that, include: The infrared continuous zoom imaging lens as described in any one of claims 1-10; as well as A mid-wave uncooled detector is located on the image side of the infrared continuous zoom imaging lens.

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