Infrared continuous zoom lens and infrared thermal imaging system

Abstract

The application discloses an infrared continuous zoom lens and an infrared thermal imaging system, which 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 surface; 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, the rear fixed group comprises a fourth lens with negative refractive power and a fifth lens with positive refractive power; wherein the number of lenses with refractive power in the infrared continuous zoom lens is five; the position of the fourth lens of the front fixed group and the rear fixed group is fixed relative to the image surface; the distance of the zoom group, the compensation group, the fifth lens of the rear fixed group relative to the front fixed group on the optical axis is adjustable; and the curvature radius R1 of the object side of the first lens and the curvature radius R2 of the image side of the first lens satisfy 1 < R2 / R1 < 2.

Description

Technical Field

[0001] The present application relates to the field of optical devices, and specifically relates to a five-piece infrared continuous zoom lens and an infrared thermal imaging system. Background Art

[0002] Due to the particularity of the infrared thermal imaging system that relies on the self-thermal radiation of natural objects for imaging, it can achieve many functions that cannot be achieved by visible light systems, making the application of infrared thermal imaging systems in the fields of security monitoring, airport monitoring, forest fire prevention, rail transit, temperature measurement, etc. continuously emphasized. Among them, the zoom infrared thermal imaging system has a wider application due to its functions of large field of view search and small field of view positioning.

[0003] The zoom lens is the core component of the zoom infrared thermal imaging system. Existing zoom lenses are usually composed of many lenses. Since the lenses used in the zoom lens are scarce germanium materials, this will lead to too high cost of the zoom lens, and the use of too many lenses will also cause the transmittance of the zoom lens to decrease, thereby affecting the detection effect. Summary of the Invention

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

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

[0006] Among them, the number of lenses with optical power in the infrared continuous zoom lens is five; the positions of the fourth lens in the front fixed group and the rear fixed group relative to the image plane are fixed; the distances of the fifth lenses in the variable magnification group, the compensation group, and the rear fixed group on the optical axis relative to the front fixed group are adjustable; and the curvature radius R1 of the object side surface of the first lens and the curvature radius R2 of the image side surface of the first lens satisfy 1 < R2 / R1 < 2.

[0007] According to an exemplary embodiment of the present application, the infrared continuous zoom lens satisfies: 1.5 < ft×(n - 1) / (FNOt×R1) < 3; and 0.02 < BFLt / ft < 0.3; where ft is the focal length of the infrared continuous zoom lens in the long focal length state, n is the refractive index at the center wavelength of the material of the first lens, FNOt is the F-number of the infrared continuous zoom lens in the long focal length state, R1 is the curvature radius of the object side surface of the first lens, and BFLt is the back focal length of the infrared continuous zoom lens in the long focal length state.

[0008] According to an exemplary embodiment of this application, the infrared continuous zoom lens satisfies: 0.3 < |f1 / ft| < 1.2; 0.1 < |f2 / ft| < 0.5; 0.15 < |f3 / ft| < 0.7; 0.5 < |f4 / ft| < 3; and 0.1 < |f5 / ft| < 0.5; where f1 is the effective focal length of the first lens, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, and ft is the focal length of the infrared continuous zoom lens in telephoto mode.

[0009] According to an exemplary embodiment of this application, the first lens is made of germanium, and the refractive indices of the second, third, fourth, and fifth lenses are all in the range of 2.3 to 4.5.

[0010] According to an exemplary embodiment of this application, 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, and the fifth lens is a meniscus lens with its convex surface facing the object side.

[0011] According to an exemplary embodiment of this application, the image-side surface of the first lens, the image-side surface of the fourth lens, and the image-side surface of the fifth lens are aspherical surfaces, and the image-side surface of the third lens is a binary surface.

[0012] According to an exemplary embodiment of this application, the object side of the fourth lens is a binary surface.

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

[0014]

[0015] Where Z is the axial sagitta of the aspherical surface in the Z direction, r is the distance from a point on the aspherical surface to the optical axis, c is the curvature of the fitted sphere, which is numerically the reciprocal of the radius of curvature, k is the conic coefficient, and A, B, C, D, and E are the coefficients of the 4th, 6th, 8th, 10th, and 12th order terms of the aspherical polynomial.

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

[0017]

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

[0019] According to an exemplary embodiment of this application, the zoom group and the compensation group move nonlinearly along the optical axis in opposite or opposite directions to switch the infrared continuous zoom lens between short focal length, medium focal length and long focal length.

[0020] According to an exemplary embodiment of this application, the zoom ratio of the infrared continuous zoom lens is 10X.

[0021] According to an exemplary embodiment of this application, the infrared continuous zoom lens operates in the wavelength range of 8μm to 12μm, has a zoom range of f35mm to f350mm, an F-number of 0.92 to 1.5, and a horizontal field of view of 2.48° to 25.2°.

[0022] Another aspect of this application provides an infrared thermal imaging system comprising the aforementioned infrared continuous zoom lens and a long-wavelength uncooled detector located on the image plane of the infrared continuous zoom lens.

[0023] The infrared continuous zoom lens provided in this application is configured with a five-element lens structure. By moving the fifth lens in the zoom group, compensation group, and rear fixed group, the continuous zoom function of the 10X optical system is achieved. This effectively shortens the system length, controls the number of lenses in the optical system, significantly reduces costs, and greatly improves the system's transmittance. While achieving zoom, this infrared continuous zoom lens can also effectively compensate for aberrations caused during zooming and aberrations caused by temperature changes, thereby ensuring good imaging performance at different focal lengths and temperatures. Attached Figure Description

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

[0025] Figure 1 A schematic diagram of the structure of an infrared thermal imaging system according to this application is shown;

[0026] Figure 2 It shows Figure 1 The diagram shows the movement pattern of the infrared continuous zoom lens.

[0027] Figures 3 to 5 The MTF diagram, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 1 of this application in the short focal length state are shown.

[0028] Figures 6 to 8The MTF diagram, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 1 of this application in the mid-focus state are shown;

[0029] Figures 9 to 11 The MTF diagram, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 1 of this application in telephoto mode are shown.

[0030] Figures 12 to 14 The MTF diagram, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 2 of this application in the short focal length state are shown;

[0031] Figures 15 to 17 The MTF diagram, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 2 of this application in the mid-focus state are shown;

[0032] Figures 18 to 20 The MTF diagram, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 2 of this application in telephoto mode are shown.

[0033] Figures 21 to 23 The MTF diagram, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 3 of this application in the short focal length state are shown;

[0034] Figures 24 to 26 The MTF chart, speckle and field curvature diagram of the infrared continuous zoom lens according to Embodiment 3 of this application in the mid-focus state are shown; and

[0035] Figures 27 to 29 The MTF diagram, blur pattern, and field curvature distortion diagram of the infrared continuous zoom lens according to Embodiment 3 of this application are shown in the telephoto state. Detailed Implementation

[0036] 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.

[0037] 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.

[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 drawn strictly to scale.

[0039] In this article, 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 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.

[0040] It should also be understood that the terms "comprising," "including," "having," "containing," and / or "comprising" as 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 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 the 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] The features, principles and other aspects of this application are described in detail below.

[0044] Figure 1 A schematic diagram of an infrared thermal imaging system according to an exemplary embodiment of this application is shown. (Reference) Figure 1 The infrared thermal imaging system includes an infrared continuous zoom lens 100, which includes a front fixed group 10, a zoom group 20, a compensation group 30 and a rear fixed group 40 along the optical axis from the object side to the image plane.

[0045] The front fixing group 10 may include, for example, a first lens 11 having positive optical power, and the front fixing group 10 is fixed in position relative to the image plane. The front fixing group 10 is used for converging and collecting light.

[0046] The zoom group 20 may include, for example, a second lens 21 with negative optical power, and the zoom group 20 is movable relative to the front fixed group 10 along the optical axis, meaning the distance between the zoom group 20 and the front fixed group 10 on the optical axis is adjustable. By adjusting the distance between the zoom group 20 and the front fixed group 10 on the optical axis, the focal length of the infrared continuous zoom lens 100 can be changed. During the zooming process of the infrared continuous zoom lens 100, the state of the infrared continuous zoom lens 100 is divided into three states according to the focal length: short focal length, medium focal length, and long focal length.

[0047] The compensation group 30 may include, for example, a third lens 31 with positive optical power, and the compensation group 30 is movable relative to the front fixed group 10 along the optical axis, that is, the distance of the compensation group 30 relative to the front fixed group 10 on the optical axis is adjustable. By adjusting the distance between the compensation group 30 and the front fixed group 10 on the optical axis, the image plane movement of the infrared continuous zoom lens 100 during zooming can be compensated, that is, the aberrations caused by the zoom group 20 during movement can be effectively compensated.

[0048] The rear fixed group 40 may include, for example, a fourth lens 41 with negative optical power and a fifth lens 42 with positive optical power. The fourth lens 41 is fixed in position relative to the image plane, while the fifth lens 42 is movable relative to the front fixed group 10 along the optical axis; that is, the distance of the fifth lens 42 relative to the front fixed group 10 on the optical axis is adjustable. By adjusting the distance between the fifth lens 42 and the front fixed group 10 on the optical axis, the focal length of the infrared continuous zoom lens 100 can be finely adjusted to compensate for the shift in image plane position under different object distances and temperatures.

[0049] The infrared continuous zoom lens 100 provided in this application can be composed of five lenses with optical power. By adjusting the distance of the fifth lens 42 of the zoom group 20, compensation group 30, and rear fixed group 40 relative to the front fixed group 10 on the optical axis, the infrared continuous zoom lens 100 can switch between short focal length, medium focal length, and long focal length. While realizing the zoom of the infrared continuous zoom lens 100, it can effectively compensate for the aberrations caused by the zoom process and the aberrations caused by temperature changes, thereby ensuring that the infrared continuous zoom lens 100 has good imaging effect under different focal lengths and different temperatures.

[0050] Figure 2 It shows Figure 1 A schematic diagram illustrating the movement of the infrared continuous zoom lens 100. (Reference) Figure 2The zoom group 20 and the compensation group 30 move non-linearly along the optical axis in opposite or opposing directions to switch the infrared continuous zoom lens 100 between short focal length, medium focal length, and telephoto states. When the zoom group 20 and the compensation group 30 move non-linearly along the optical axis in opposite directions, the focal length of the infrared continuous zoom lens 100 increases; for example, the infrared continuous zoom lens 100 switches from a short focal length state to a medium focal length state, or from a medium focal length state to a telephoto state. When the zoom group 20 and the compensation group 30 move non-linearly along the optical axis in opposite directions, the focal length of the infrared continuous zoom lens 100 decreases; for example, the infrared continuous zoom lens 100 switches from a telephoto state to a medium focal length state, or from a medium focal length state to a short focal length state.

[0051] Taking the increase in focal length of the infrared continuous zoom lens 100 as an example, we can illustrate the movement of the zoom group 20 and the compensation group 30:

[0052] When the zoom group 20 moves to the right on the optical axis, the compensation group 30 needs to move to the left accordingly. Essentially, this increases the distance between the zoom group 20 and the front fixed group 10, while simultaneously decreasing the distance between the compensation group 30 and the zoom group 20. It can be understood that when the zoom group 20 moves to the right, the divergence effect of the zoom group 20 on the beam emitted from the front fixed group 10 is relatively delayed. By moving the compensation group 30 to the left by a corresponding distance, the time of the beam-converging effect of the compensation group 30 on the beam is changed, thereby altering the beam-converging effect of the entire lens and thus increasing the focal length of the infrared continuous zoom lens 100.

[0053] Taking the focal length reduction of the infrared continuous zoom lens 100 as an example, the movement of the zoom group 20 and the compensation group 30 will be explained:

[0054] When the zoom group 20 moves to the left on the optical axis, the compensation group 30 needs to move to the right accordingly. Essentially, this shortens the distance between the zoom group 20 and the front fixed group 10, while simultaneously increasing the distance between the compensation group 30 and the zoom group 20. It can be understood that when the zoom group 20 moves to the left, its divergence effect on the beam emitted from the front fixed group 10 will be relatively advanced. By moving the compensation group 30 to the right by a corresponding distance, the timing of its beam-converging effect is changed, altering the overall beam-converging effect of the lens, thereby reducing the focal length of the infrared continuous zoom lens 100.

[0055] It should be noted that, in actual use, the movement of the zoom group 20 and the compensation group 30 in the infrared continuous zoom lens 100 needs to be synchronously driven according to the determined positional relationship in order to ensure that the image of the infrared continuous zoom lens 100 is clear during the zooming process.

[0056] In an exemplary embodiment, the front fixed group 10, the zoom group 20, the compensation group 30, and the rear fixed group 40 are disposed within a lens barrel. The fourth lens 41 in the front fixed group 10 and the rear fixed group 40 is fixed in position within the lens barrel, while the fifth lens 42 in the zoom group 20, the compensation group 30, and the rear fixed group 40 can reciprocate along the optical axis within the lens barrel to change the focal length. Specifically, three cam curve grooves are respectively provided on the inside of the lens barrel to control the movement of the fifth lens 42 in the zoom group 20, the compensation group 30, and the rear fixed group 40.

[0057] In an exemplary embodiment, the first lens 11 may be, for example, a meniscus lens with its convex surface facing the object side. The second lens 21 may be, for example, a biconcave lens. The third lens 31 may be, for example, a biconvex lens. The fourth lens 41 may be, for example, a meniscus lens with its convex surface facing the object side. The fifth lens 42 is a meniscus lens with its convex surface facing the object side.

[0058] In an exemplary embodiment, at least three surfaces of the first lens 11 to the fifth lens 42 are aspherical, and at least one surface is a binary surface (i.e., a diffraction surface). The infrared continuous zoom lens 100 provided in this application uses a combination of aspherical and diffraction surfaces, which can effectively correct chromatic aberration, compensate for the chromatic aberration caused by temperature changes, and improve the imaging quality of the infrared continuous zoom lens 100.

[0059] The image-side surfaces of the first lens 11, the fourth lens 41, and the fifth lens 42 can be, for example, aspherical surfaces, wherein the aspherical surfaces are even-order aspherical surfaces and satisfy the following equation:

[0060]

[0061] Where Z is the axial sagitta in the Z-direction of the aspherical surface, r is the distance from a point on the aspherical surface to the optical axis, c is the curvature of the fitted sphere, numerically the reciprocal of the radius of curvature, k is the conic coefficient, and A, B, C, D, and E are the coefficients of the 4th, 6th, 8th, 10th, and 12th order terms of the aspherical polynomial. Through the above settings, at least the image-side surfaces of the first lens 11, the fourth lens 41, and the fifth lens 42 can be set as aspherical, which is beneficial for correcting various aberrations in the optical system and further ensures that the infrared continuous zoom lens 100 can achieve clear imaging.

[0062] The image-side surface of the third lens 31 can be, for example, a binary surface (i.e., a diffraction surface), and the aforementioned binary surface satisfies the following equation:

[0063]

[0064] Where λ0 is the center wavelength during design, and n0 is the refractive index corresponding to the center wavelength of the material. M is the diffraction order, N is the order of the polynomial coefficients in the series, A i is the phase coefficient of the diffraction surface, ρ is the normalized radial aperture coordinate, ρ = r / r1, and r1 is the normalized radius of the diffraction surface. Through the above settings, at least the image side of the third lens 31 can be set as the diffraction surface, which plays a role in compensating for the thermal difference and further ensures that the infrared continuous zoom lens 100 can form a clear image. In some embodiments, the object side of the fourth lens 41 can also be set as a binary surface.

[0065] In an exemplary embodiment, the material of the first lens 11 is germanium material, and the refractive indices of the materials of the second lens 21, the third lens 31, the fourth lens 41, and the fifth lens 42 are all within the range of 2.3 to 4.5.

[0066] In an exemplary embodiment, the front fixed group 10 satisfies the following condition: 1 < R2 / R1 < 2; where R1 is the radius of curvature of the object side of the first lens 11, and R2 is the radius of curvature of the image side of the first lens 11. By controlling the radii of curvature of the object side and the image side of the first lens 11, the first lens 11 can have a specific meniscus shape, which can provide an appropriate and stable light converging effect while ensuring its positive optical power, and can cooperate with other lenses to achieve the corresponding optical power combination as a basis to support the moving zoom of the varifocal group 20 and the compensation group 30.

[0067] In an exemplary embodiment, the infrared continuous zoom lens 100 satisfies: 0.3 < |f1 / ft| < 1.2; 0.1 < |f2 / ft| < 0.5; 0.15 < |f3 / ft| < 0.7; 0.5 < |f4 / ft| < 3; and 0.1 < |f5 / ft| < 0.5; where f1 is the effective focal length of the first lens 11, f2 is the effective focal length of the second lens 21, f3 is the effective focal length of the third lens 31, f4 is the effective focal length of the fourth lens 41, f5 is the effective focal length of the fifth lens 42, and ft is the focal length of the infrared continuous zoom lens 100 in the long focal state. By controlling the mutual relationship between the effective focal lengths of the first lens 11 to the fifth lens 42 and the focal length of the infrared continuous zoom lens 100 in the long focal state, the functions of each lens in its respective group can be reasonably defined, and the mutual cooperation of each lens can be ensured, so that the infrared continuous zoom lens 100 can achieve zooming and clear imaging.

[0068] In an exemplary embodiment, the infrared continuous zoom lens 100 satisfies: 1.5 < ft×(n - 1) / (FNOt×R1) < 3; and 0.02 < BFLt / ft < 0.3; where ft is the focal length of the infrared continuous zoom lens 100 in the long - focal - length state, n is the refractive index at the center wavelength of the material of the first lens 11, FNOt is the F - number of the infrared continuous zoom lens 100 in the long - focal - length state, R1 is the curvature radius of the object - side surface of the first lens 11, and BFLt is the back focal length of the infrared continuous zoom lens 100 in the long - focal - length state.

[0069] In an exemplary embodiment, the working wavelength band of the infrared continuous zoom lens 100 can be set to 8μm to 12μm, and the zoom range is f35mm to f350mm, the zoom ratio is 10X, the horizontal field of view angle is 2.48° to 25.2°, and the F - number is 0.92 to 1.5.

[0070] Compared with the existing zoom lenses, the infrared continuous zoom lens 100 provided in this application adopts the method of moving the fifth lens 42 in the zoom group 20, the compensation group 30, and the rear fixed group 40 to achieve the continuous zoom function of the 10X optical system. And through this zoom method, the system length is effectively shortened, the number of lenses in the optical system is controlled, and the cost is greatly reduced. The infrared continuous zoom lens 100 provided in this application adopts a 5P optical structure and a method of mixing aspherical surfaces and diffractive surfaces to achieve 10X continuous zoom. It can not only effectively correct chromatic aberration, has the function of actively eliminating thermal aberration, realizes stable imaging of the lens within a wide temperature range of - 40° to + 60°, meets the requirement that the lens can be used in an environment with large temperature changes, but also can well improve the transmittance of the system by reducing the number of lenses.

[0071] Based on the same concept, this application also provides an infrared thermal imaging system. Continuing to refer to Figure 1 , the infrared thermal imaging system includes the above - mentioned infrared continuous zoom lens 100, and also includes a long - wave uncooled detector 200 located on the image plane 70 of the infrared continuous zoom lens 100. Among them, the long - wave uncooled detector 200 has a first window 50 and a second window 60. The working wavelength band of the infrared continuous zoom lens 100 is 8μm to 12μm, the zoom range is f35mm to f350mm, the zoom ratio is 10X, the F - number is 0.92 to 1.5, the horizontal field of view angle is 2.48° to 25.2°, and it can be adapted to the long - wave uncooled detector 200 with a specification of 1280×1024_12μm. And since this infrared thermal imaging system includes the above - mentioned infrared continuous zoom lens 100, it has the same or similar technical effects as those of the above - mentioned infrared continuous zoom lens 100, which will not be elaborated here.

[0072] The following describes a specific embodiment of the infrared continuous zoom lens 100 applicable to the above embodiments with reference to the accompanying drawings.

[0073] Example 1

[0074] Table 1 shows the basic parameters of the infrared continuous zoom lens 100 of Embodiment 1, wherein the units for radius of curvature, spacing and aperture are all millimeters (mm).

[0075]

[0076] Table 1

[0077] The surface numbers in Table 1 are assigned according to the surface sequence of each lens, where "1" represents the object-side surface of the first lens 11, "2" represents the image-side surface of the first lens 11, and so on. The radius of curvature indicates the degree of curvature of the lens surface, where "infinity" indicates an infinite radius of curvature, 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 20 and compensation group 30 need to move back and forth along the optical axis, the spacing corresponding to the zoom group 20 and compensation group 30 is a range value. The refractive index of the material represents its ability to deflect light; a blank space indicates that the current position is air with a refractive index of 1.

[0078] In this embodiment, the conic coefficients of the aspheric surface and the binary surface, as well as the order coefficients of the aspheric polynomial, are shown in Table 2.

[0079] Face number face shape k A B C D E 2 aspherical 0 9.37E-10 -8.19E-15 1.67E-18 -1.07E-22 2.44E-27 3 aspherical 0 1.34E-07 -5.62E-12 -2.06E-16 -1.11E-19 3.96E-23 6 Binary Surface 0 6.11E-08 -1.97E-11 1.64E-14 -7.55E-18 1.40E-21 7 Binary Surface 0 -1.39E-06 -6.37E-10 1.51E-13 -1.68E-17 -2.65E-21 8 aspherical 0 -2.29E-06 -1.19E-09 6.42E-13 -1.93E-16 2.11E-20 10 aspherical 0 1.07E-07 2.23E-11 -2.24E-14 1.23E-17 -2.66E-21

[0080] Table 2

[0081] In this embodiment, the normalized radius and phase coefficient of the binary surface are shown in Table 3.

[0082] Face number face shape Naturalization radius <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[A3]]> <![CDATA[A4]]> 6 Binary Surface 41.00 -122.89 -3.91 5.97 -1.33 7 Binary Surface 40.00 44.33 32.01 -1.96 -17.34

[0083] Table 3

[0084] The infrared continuous zoom lens 100 provided in Example 1 can have a short focal length mode, a medium focal length mode, and a long focal length mode, wherein, Figures 3 to 5 These are the MTF chart, speckle and field curvature diagrams of the infrared continuous zoom lens 100 in short focal length mode. Figures 6 to 8 These are the MTF chart, blur pattern, and field curvature distortion chart of an infrared continuous zoom lens 100 in mid-range focal length mode. Figures 9 to 11 These are the MTF (Mean Transformer File) chart, speckle pattern, and field curvature distortion chart of an infrared continuous zoom lens 100 in telephoto mode. (Comparison) Figure 3 , Figure 6 and Figure 9At different focal lengths, the transfer function of the infrared continuous zoom lens 100 is consistently around 0.15 or higher. This indicates that the infrared continuous zoom lens 100 achieves good resolution in both the central and peripheral fields of view, meeting the resolution requirements for large fields of view and large target surfaces. (Comparison) Figure 4 , Figure 7 and Figure 10 At different focal lengths, the radius of the blur spot of the infrared continuous zoom lens 100 varies little at different field-of-view positions, which means that the aberrations of the infrared continuous zoom lens 100 are small at different field-of-view positions. (Comparison) Figure 5 , Figure 8 and Figure 11 At different focal lengths, the maximum distortion of the infrared continuous zoom lens 100 is within ±5%, and the field curvature in the meridional and sagittal directions for different wavelengths of light is between ±0.20mm. This means that the infrared continuous zoom lens 100 can achieve small distortion and field curvature at different focal lengths. In summary, the infrared continuous zoom lens 100 provided in Example 1 can correct various aberrations and ensure imaging quality at all focal lengths. The infrared continuous zoom lens 100 provided in Example 1 has good imaging performance during zooming.

[0085] Example 2

[0086] Table 4 shows the basic parameters of the infrared continuous zoom lens 100 of Example 2, where the units for radius of curvature, spacing and aperture are millimeters (mm).

[0087]

[0088]

[0089] Table 4

[0090] In this embodiment, the conic coefficients of the aspheric surface and the binary surface, as well as the order coefficients of the aspheric polynomial, are shown in Table 5.

[0091] Face number face shape k A B C D E 2 aspherical 0 1.51E-09 -2.09E-13 1.19E-16 -2.09E-20 1.36E-24 3 aspherical 0 2.79E-07 -5.53E-11 6.43E-14 -5.47E-17 1.84E-20 6 Binary Surface 0 6.05E-08 -3.02E-11 3.83E-14 -2.66E-17 7.58E-21 7 aspherical 0 -2.69E-06 -1.39E-09 2.59E-13 5.19E-17 -3.52E-20 8 aspherical 0 -3.97E-06 -2.09E-09 1.31E-12 -2.44E-16 -4.01E-20 10 aspherical 0 1.07E-07 2.23E-11 -2.24E-14 1.23E-17 -2.66E-21

[0092] Table 5

[0093] In this embodiment, the normalized radius and phase coefficient of the binary surface are shown in Table 6.

[0094] Face number face shape Naturalization radius <![CDATA[A1]]> <![CDATA[A2]]> <![CDATA[A3]]> <![CDATA[A4]]> 6 Binary Surface 40.00 -24.11 1.90 3.71 -4.31

[0095] Table 6

[0096] The infrared continuous zoom lens 100 provided in Example 2 can have a short focal length mode, a medium focal length mode, and a long focal length mode, wherein, Figures 12 to 14These are the MTF chart, speckle and field curvature diagrams of the infrared continuous zoom lens 100 in short focal length mode. Figures 15 to 17 These are the MTF chart, blur pattern, and field curvature distortion chart of an infrared continuous zoom lens 100 in mid-range focal length mode. Figures 18 to 20 These are the MTF (Mean Transformer File) chart, speckle pattern, and field curvature distortion chart of an infrared continuous zoom lens 100 in telephoto mode. (Comparison) Figure 12 , Figure 15 and Figure 18 At different focal lengths, the transfer function of the infrared continuous zoom lens 100 is consistently around 0.2 or higher. This indicates that the infrared continuous zoom lens 100 achieves good resolution in both the central and peripheral fields of view, meeting the resolution requirements for large fields of view and large target surfaces. (Comparison) Figure 13 , Figure 16 and Figure 19 At different focal lengths, the radius of the blur spot of the infrared continuous zoom lens 100 varies little at different field-of-view positions, which means that the aberrations of the infrared continuous zoom lens 100 are small at different field-of-view positions. (Comparison) Figure 14 , Figure 17 and Figure 20 At different focal lengths, the maximum distortion of the infrared continuous zoom lens 100 is within ±5%, and the field curvature in the meridional and sagittal directions for different wavelengths of light is between ±0.10mm. This means that the infrared continuous zoom lens 100 can achieve small distortion and field curvature at different focal lengths. In summary, the infrared continuous zoom lens 100 provided in Embodiment 2 can correct various aberrations and ensure imaging quality at all focal lengths. The infrared continuous zoom lens 100 provided in Embodiment 2 has good imaging performance during zooming.

[0097] Example 3

[0098] Table 7 shows the basic parameters of the infrared continuous zoom lens 100 of Example 3, wherein the units for radius of curvature, spacing and aperture are millimeters (mm).

[0099]

[0100] Table 7

[0101] In this embodiment, the conic coefficients of the aspheric surface and the binary surface, as well as the order coefficients of the aspheric polynomial, are shown in Table 8.

[0102] Face number face shape k A B C D E 2 aspherical 0 9.73E-11 4.02E-15 -2.16E-19 4.22E-24 4 aspherical 0 -5.49E-08 -1.05E-11 6.12E-15 -1.22E-18 6 Binary Surface 0 3.39E-08 -3.60E-12 2.14E-15 -4.87E-19 7 Binary Surface 0 -7.69E-07 -6.80E-10 -7.08E-14 -2.87E-17 8 aspherical 0 -1.51E-06 -1.82E-09 / / 10 aspherical 0 1.99E-07 7.45E-12 6.00E-15 3.07E-17

[0103] Table 8

[0104] In this embodiment, the normalized radius and phase coefficient of the binary surface are shown in Table 9.

[0105] Face number face shape Naturalization radius <![CDATA[A1]]> <![CDATA[A2]]> 6 Binary Surface 40.00 -114.21 4.83 7 Binary Surface 40.00 34.90 7.08

[0106] Table 9

[0107] The infrared continuous zoom lens 100 provided in Example 3 can have a short focal length mode, a medium focal length mode, and a long focal length mode, wherein, Figures 21 to 23 These are the MTF chart, speckle and field curvature diagrams of the infrared continuous zoom lens 100 in short focal length mode. Figures 24 to 26 These are the MTF chart, blur pattern, and field curvature distortion chart of an infrared continuous zoom lens 100 in mid-range focal length mode. Figures 27 to 29 These are the MTF (Mean Transformer File) chart, speckle pattern, and field curvature distortion chart of an infrared continuous zoom lens 100 in telephoto mode. (Comparison) Figure 21 , Figure 24 and Figure 27 At different focal lengths, the transfer function of the infrared continuous zoom lens 100 is consistently around 0.1 or higher. This indicates that the infrared continuous zoom lens 100 achieves good resolution in both the central and peripheral fields of view, meeting the resolution requirements for large fields of view and large target surfaces. (Comparison) Figure 22 , Figure 25 and Figure 28 At different focal lengths, the radius of the blur spot of the infrared continuous zoom lens 100 varies little at different field-of-view positions, which means that the aberrations of the infrared continuous zoom lens 100 are small at different field-of-view positions. (Comparison) Figure 23 , Figure 26 and Figure 29 At different focal lengths, the maximum distortion of the infrared continuous zoom lens 100 is within ±5%, and the field curvature in the meridional and sagittal directions for different wavelengths of light is between ±0.20mm. This means that the infrared continuous zoom lens 100 can achieve small distortion and field curvature at different focal lengths. In summary, the infrared continuous zoom lens 100 provided in Embodiment 3 can correct various aberrations and ensure imaging quality at all focal lengths. The infrared continuous zoom lens 100 provided in Embodiment 3 has good imaging performance during zooming.

[0108] 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 features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An infrared continuous zoom lens characterized by, The infrared continuous zoom lens comprises, in sequence from the object side to the image plane along the optical axis, a front fixed group, a variable magnification group, a compensation group and a rear fixed group; the front fixed group comprises a first lens with positive refractive power, the variable magnification group comprises a second lens with negative refractive power, the compensation group comprises a third lens with positive refractive power, the rear fixed group comprises a fourth lens with negative refractive power and a fifth lens with positive refractive power; the fourth lens is a meniscus lens with a convex surface facing the object side, and the fifth lens is a meniscus lens with a convex surface facing the object side; The number of lenses with refractive power in the infrared continuous zoom lens is five. The positions of the fourth lens of the front fixed group and the rear fixed group relative to the image plane are fixed. The distance of the fifth lens of the variable magnification group, the compensation group and the rear fixed group relative to the front fixed group on the optical axis is adjustable. When the infrared continuous zoom lens is in a long-focus state, the distance of the front fixed group and the variable magnification group on the optical axis is greater than the distance of the fourth lens of the compensation group and the rear fixed group on the optical axis. The curvature radius R1 of the object side surface of the first lens and the curvature radius R2 of the image side surface of the first lens satisfy 1 < R2 / R1 ≤ 294.76 / 166.

01. The effective focal length f2 of the second lens and the focal length ft of the infrared continuous zoom lens in a long-focus state satisfy 0.1 < |f2 / ft| < 0.5; and The effective focal length f3 of the third lens and the focal length ft of the infrared continuous zoom lens in a long-focus state satisfy 0.15 < |f3 / ft| < 0.

7.

2. The infrared zoom lens according to claim 1, characterized by The infrared continuous zoom lens satisfies: 1.5 < ft×(n-1) / (FNOt×R1) < 3; and 0.02 < BFLt / ft < 0.3; wherein ft is the focal length of the infrared continuous zoom lens in a long-focus state, n is the refractive index of the material of the first lens at the central wavelength, FNOt is the F number of the infrared continuous zoom lens in a long-focus state, R1 is the curvature radius of the object side surface of the first lens, and BFLt is the back focal length of the infrared continuous zoom lens in a long-focus state.

3. The infrared zoom lens of claim 1, wherein The infrared continuous zoom lens satisfies: 0.3 < |f1 / ft| < 1.2; 0.5 < |f4 / ft| < 3; and 0.1 < |f5 / ft| < 0.5; wherein f1 is the effective focal length of the first lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, and ft is the focal length of the infrared continuous zoom lens in a long-focus state.

4. The infrared zoom lens of claim 1, wherein The material of the first lens is germanium material, and the materials of the second lens, the third lens, the fourth lens and the fifth lens have a refractive index in the range of 2.3-4.

5.

5. The infrared continuous zoom lens according to claim 1, wherein The first lens is a meniscus lens with a convex surface facing the object side, the second lens is a double-concave lens, and the third lens is a double-convex lens.

6. The infrared zoom lens of claim 1, wherein, The image side surface of the first lens, the image side surface of the fourth lens and the image side surface of the fifth lens are aspheric surfaces, and the image side surface of the third lens is a binary surface.

7. The infrared continuous zoom lens according to claim 6, characterized in that, The object side surface of the fourth lens is a binary surface.

8. The infrared continuous zoom lens according to claim 6, wherein The aspherical surface satisfies the following equation: Wherein, Z is the axial height of the aspherical surface in the Z direction, r is the distance from a point on the aspherical surface to the optical axis, c is the curvature of the fitting sphere, which is the reciprocal of the radius of curvature in value, k is the conic coefficient, A, B, C, D, and E are the 4th, 6th, 8th, 10th, and 12th order term coefficients of the aspherical surface polynomial.

9. The infrared continuous zoom lens according to claim 6, wherein The binary surface satisfies the following equation: where λ0 is the center wavelength at design, n0 is the refractive index corresponding to the center wavelength of the material, ; M is the diffraction order, N is the order of polynomial coefficients in the series, A i is the phase coefficient of the diffractive surface, p is the normalized radial aperture coordinate, p = r / r1, r1 is the normalized radius of the diffractive surface.

10. The infrared continuous zoom lens of claim 1, wherein, The variable magnification group and the compensation group move in a non-linear manner along the optical axis in opposite directions or in the same direction, so that the infrared continuous zoom lens switches between a short focus state, a medium focus state, and a long focus state.

11. The infrared continuous zoom lens of claim 1, wherein, The variable magnification ratio of the infrared continuous zoom lens is 10X.

12. The infrared zoom lens of claim 1, wherein, The working waveband of the infrared continuous zoom lens is 8-12 μm, the zoom range is f35mm-f350mm, the F number is 0.92-1.5, and the horizontal field of view is 2.48°-25.2°.

13. An infrared thermal imaging system characterized by, The infrared continuous zoom lens according to any one of claims 1-12 and a long-wave uncooled detector, wherein the long-wave uncooled detector is located on the image plane of the infrared continuous zoom lens.

Images