Infrared zoom lens and infrared thermal imaging system

Abstract

The application discloses an infrared zoom lens and an infrared thermal imaging system. The infrared zoom lens comprises, in sequence along an optical axis from an object side to an image plane, a front fixed group, a variable magnification group, a compensation group, a rear fixed group and a focusing group. The front fixed group comprises a first lens with positive refractive power and a second lens with negative refractive power. The variable magnification group comprises a third lens with negative refractive power. The compensation group comprises a fourth lens with positive refractive power. The rear fixed group comprises a fifth lens and a sixth lens. The fifth lens and the sixth lens have opposite signs of refractive power. The focusing group comprises a seventh lens with positive refractive power and an eighth lens with positive refractive power. The eighth lens is a biconvex lens. The infrared zoom lens has eight lenses with refractive power. The positions of the front fixed group and the rear fixed group relative to the image plane are fixed.

Description

Technical Field

[0001] This application relates to the field of optical devices, specifically to an eight-element infrared zoom lens and an infrared thermal imaging system. Background Technology

[0002] Infrared thermal imaging lenses rely on the thermal radiation of natural objects to create images, giving them excellent resistance to external interference and the ability to image 24 / 7 in all weather conditions. They can be used in extreme environments such as rain, snow, and fog. Therefore, infrared thermal imaging lenses are playing an increasingly important role in civilian surveillance.

[0003] Fixed-focus infrared thermal imaging lenses have certain limitations; they cannot handle tasks in complex scenarios and are prone to losing sight of monitored targets. Therefore, infrared zoom lenses have become a new research and development trend. Infrared zoom lenses have the functions of wide field-of-view search and precise positioning in a narrow field of view, and can effectively complete various complex surveillance tasks. However, existing infrared zoom lenses suffer from small zoom ratios and poor imaging performance, which affect and limit their application in the civilian surveillance field. Summary of the Invention

[0004] This application provides an infrared 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] The first aspect of this application provides an infrared zoom lens comprising, along the optical axis from the object side to the image plane, the following in sequence: a front fixed group comprising a first lens with positive optical power and a second lens with negative optical power; a zoom group comprising a third lens with negative optical power; a compensation group comprising a fourth lens with positive optical power; a rear fixed group comprising a fifth lens with optical power and a sixth lens with optical power, wherein the optical power signs of the fifth lens and the sixth lens are opposite; and a focusing group comprising a seventh lens with positive optical power and an eighth lens with positive optical power; the eighth lens being a biconvex lens; wherein the infrared zoom lens comprises eight lenses with optical power; the positions of the front fixed group and the rear fixed group relative to the image plane are fixed; and the distances of the zoom group, the compensation group, and the focusing group relative to the front fixed group on the optical axis are adjustable.

[0006] 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 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 concave surface facing the object side; the sixth lens is a meniscus lens with its convex surface facing the object side; and the seventh lens is a meniscus lens with its convex surface facing the object side.

[0007] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.1 < |f1 / ft| < 0.4, where f1 is the effective focal length of the first lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0008] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.1 < |f2 / ft| < 0.5, where f2 is the effective focal length of the second lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0009] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.01 < |f3 / ft| < 0.1, where f3 is the effective focal length of the third lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0010] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.02 < |f4 / ft| < 0.07, where f4 is the effective focal length of the fourth lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0011] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.1 < |f5 / ft| < 10, where f5 is the effective focal length of the fifth lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0012] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.2 < |f6 / ft| < 0.8, where f6 is the effective focal length of the sixth lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0013] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.3 < |f7 / ft| < 2.5, where f7 is the effective focal length of the seventh lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0014] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.01 < |f8 / ft| < 0.05, where f8 is the effective focal length of the eighth lens and ft is the focal length of the infrared zoom lens in telephoto mode.

[0015] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 1.0 < |ft×(n-1) / (FNO×R1)| < 3.5, where ft is the focal length of the infrared zoom lens in telephoto mode, n is the center wavelength refractive index of the first lens, FNO is the relative F number of the infrared zoom lens, and R1 is the radius of curvature of the object side surface of the first lens.

[0016] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.40 < |TTL / ft| < 0.65, where TTL is the axial distance from the object side of the first lens to the image plane, and ft is the focal length of the infrared zoom lens in telephoto mode.

[0017] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.01≤|f1 / f5|<0.95, where f1 is the effective focal length of the first lens and f5 is the effective focal length of the fifth lens.

[0018] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 20≤ft / fw≤22, where ft is the focal length of the infrared zoom lens in telephoto mode and fw is the focal length of the infrared zoom lens in short focal length mode.

[0019] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: fw≥15mm; and 300mm≤ft≤330mm, where ft is the focal length of the infrared zoom lens in telephoto mode and fw is the focal length of the infrared zoom lens in telephoto mode.

[0020] According to an exemplary embodiment of this application, the infrared zoom lens satisfies: 0.1≤△L / TTL≤0.4, where △L is the travel distance of the zoom group on the optical axis, and TTL is the axial distance from the object side of the first lens to the image plane.

[0021] According to an exemplary embodiment of this application, at least two of the first to eighth lenses are configured as calcium fluoride lenses.

[0022] The second aspect of this application provides an infrared thermal imaging system comprising the infrared zoom lens described in the first aspect and a mid-wave cooled detector located on the image plane of the infrared zoom lens.

[0023] The infrared zoom lens provided in this application employs eight lenses, enabling continuous zoom functionality through the movement of the zoom group, compensation group, and focusing group, while ensuring clear imaging. Furthermore, the rational configuration of the optical power of each lens helps balance aberrations and improves the imaging performance of the infrared zoom lens. 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 zoom lens according to this application is shown;

[0026] Figure 2A and Figure 2BA schematic diagram of the speckle of confusion and a field curvature distortion diagram of the infrared zoom lens according to Embodiment 1 of this application in a short focal length state are shown respectively.

[0027] Figure 3A and Figure 3B A schematic diagram of the blur pattern and a field curvature distortion diagram of the infrared zoom lens according to Embodiment 1 of this application in the mid-focus state are shown respectively.

[0028] Figure 4A and Figure 4B A schematic diagram of the speckle and field curvature distortion of the infrared zoom lens in telephoto mode according to Embodiment 1 of this application are shown respectively.

[0029] Figure 5A and Figure 5B A schematic diagram of the speckle of confusion and a field curvature distortion diagram of the infrared zoom lens according to Embodiment 2 of this application in a short focal length state are shown respectively.

[0030] Figure 6A and Figure 6B The diagrams show the blur pattern and field curvature distortion of the infrared zoom lens in the mid-focus state according to Embodiment 2 of this application.

[0031] Figure 7A and Figure 7B A schematic diagram of the speckle of confusion and a field curvature distortion diagram of the infrared zoom lens in telephoto mode according to Embodiment 2 of this application are shown respectively.

[0032] Figure 8A and Figure 8B The diagrams show the speckle of confusion and field curvature distortion of the infrared zoom lens according to Embodiment 3 of this application in a short focal length state.

[0033] Figure 9A and Figure 9B The diagrams showing the blur pattern and field curvature distortion of the infrared zoom lens in mid-focus state according to Embodiment 3 of this application are illustrated respectively; and

[0034] Figure 10A and Figure 10B The diagrams show the blur pattern and field curvature distortion of the infrared zoom lens in telephoto mode according to Embodiment 3 of this application. Detailed Implementation

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 image plane is called the image-side surface of the lens.

[0039] It should also be understood that the terms "comprising," "having," and / or "including," 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 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.

[0040] 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.

[0041] 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.

[0042] The features, principles and other aspects of this application are described in detail below.

[0043] refer to Figure 1 According to an exemplary embodiment of this application, the infrared zoom lens 100 may sequentially include a front fixed group G1, a zoom group G2, a compensation group G3, a rear fixed group G4, and a focusing group G5 along the optical axis from the object side to the image plane.

[0044] In an exemplary implementation, reference Figure 1 The front fixed group G1 may include a first lens L1 with positive optical power and a second lens L2 with negative optical power, and the position of the front fixed group G1 relative to the image plane is fixed.

[0045] In an exemplary implementation, reference Figure 1 The zoom group G2 may include a third lens L3 with negative optical power, and the zoom group G2 is movable relative to the front fixed group G1 along the optical axis, meaning the distance between the zoom group G2 and the front fixed group G1 on the optical axis is adjustable. By adjusting the distance between the zoom group G2 and the front fixed group G1 on the optical axis, the focal length of the infrared zoom lens 100 can be changed. During the zooming process of the infrared zoom lens 100, the state of the infrared zoom lens 100 is divided into three states according to the focal length: short focal length, medium focal length, and long focal length.

[0046] In an exemplary implementation, reference Figure 1 The compensation group G3 may include a fourth lens L4 with positive optical power, and the compensation group G3 is movable relative to the front fixed group G1 along the optical axis, that is, the distance of the compensation group G3 relative to the front fixed group G1 on the optical axis is adjustable. By adjusting the distance between the compensation group G3 and the front fixed group G1 on the optical axis, the image plane movement of the infrared zoom lens 100 during the zoom process can be compensated, that is, the aberrations caused by the zoom group G2 during the movement can be effectively compensated.

[0047] In an exemplary implementation, reference Figure 1 The rear fixed group G4 may include a fifth lens L5 with optical power and a sixth lens L6 with optical power, wherein the optical power signs of the fifth lens L5 and the sixth lens L6 are opposite. The position of the rear fixed group G4 relative to the image plane is fixed.

[0048] In an exemplary implementation, reference Figure 1 The focusing group G5 may include a seventh lens L7 with positive optical power and an eighth lens L8 with positive optical power, and the focusing group G5 is movable relative to the front fixed group G1 along the optical axis, that is, the distance of the focusing group G5 relative to the front fixed group G1 on the optical axis is adjustable. By adjusting the distance of the focusing group G5 relative to the front fixed group G1 on the optical axis, it is beneficial to ensure sharp imaging.

[0049] The infrared zoom lens provided in this application employs eight lenses. By adjusting the distances of the zoom group, compensation group, and focusing group relative to the front fixed group on the optical axis, the infrared zoom lens can switch between short-focus, medium-focus, and long-focus modes. Furthermore, while achieving zooming, it effectively compensates for aberrations caused during the zoom process, thus ensuring good imaging performance at different focal lengths and expanding its application range in complex scenes. In addition, the aforementioned infrared zoom lens can also produce clear images. Reasonable configuration of the optical power of each lens helps balance aberrations and improve the imaging performance of the infrared zoom lens.

[0050] In an exemplary implementation, reference Figure 1 The zoom group G2 and the compensation group G3 move non-linearly along the optical axis in opposite or opposing directions to switch the infrared zoom lens 100 between short focal length, medium focal length, and telephoto modes. When the zoom group G2 and the compensation group G3 move non-linearly along the optical axis in opposite directions, the focal length of the infrared zoom lens 100 increases; for example, the infrared zoom lens 100 switches from a short focal length mode to a medium focal length mode, or from a medium focal length mode to a telephoto mode. When the zoom group G2 and the compensation group G3 move non-linearly along the optical axis in opposite directions, the focal length of the infrared zoom lens 100 decreases; for example, the infrared zoom lens 100 switches from a telephoto mode to a medium focal length mode, or from a medium focal length mode to a short focal length mode.

[0051] The following example, using the increase in focal length of the infrared zoom lens 100, illustrates the movement of zoom group G2 and compensation group G3:

[0052] When the zoom group G2 moves along the optical axis towards the image plane, the compensation group G3 needs to move accordingly towards the object side. Essentially, this increases the distance between the zoom group G2 and the front fixed group G1, while simultaneously decreasing the distance between the compensation group G3 and the zoom group G2. It can be understood that when the zoom group G2 moves towards the image plane, the divergence effect of the zoom group G2 on the beam emitted from the front fixed group G1 is relatively delayed. By moving the compensation group G3 a corresponding distance towards the object side, the time of the beam-converging effect of the compensation group G3 is changed, thereby altering the beam-converging effect of the entire lens and ultimately increasing the focal length of the infrared zoom lens 100.

[0053] The following example, using the focal length reduction of the infrared zoom lens 100, illustrates the movement of zoom group G2 and compensation group G3:

[0054] When the zoom group G2 moves along the optical axis towards the object side, the compensation group G3 needs to move accordingly towards the image plane. Essentially, this reduces the distance between the zoom group G2 and the front fixed group G1, while simultaneously increasing the distance between the compensation group G3 and the zoom group G2. It can be understood that when the zoom group G2 moves towards the object side, its divergence effect on the beam emitted from the front fixed group G1 will be relatively advanced. By moving the compensation group G3 a corresponding distance towards the image plane, the time of its beam-converging effect is changed, thereby altering the overall beam-converging effect of the lens and ultimately reducing the focal length of the infrared zoom lens 100.

[0055] It should be noted that, in actual use, the movement of the zoom group G2 and the compensation group G3 in the infrared zoom lens 100 needs to be synchronously driven according to the established positional relationship in order to ensure that the image of the infrared zoom lens 100 is clear during the zooming process.

[0056] In an exemplary embodiment, the front fixed group G1, the zoom group G2, the compensation group G3, the rear fixed group G4, and the focusing group G5 are disposed within a lens barrel. The positions of the front fixed group G1 and the rear fixed group G4 are fixed within the lens barrel, while the zoom group G2, the compensation group G3, and the focusing group G5 can reciprocate along the optical axis within the lens barrel to change the focal length. Specifically, four cam curve grooves are respectively provided on the inside of the lens barrel corresponding to the third lens L3, the fourth lens L4, the seventh lens L7, and the eighth lens L8 to control the movement of the corresponding lenses.

[0057] In an exemplary embodiment, the first lens L1 can be a meniscus lens with its convex surface facing the object side. The second lens L2 can be a meniscus lens with its convex surface facing the object side. The third lens L3 can be a biconcave lens. The fourth lens L4 can be a biconvex lens. The fifth lens L5 can be a meniscus lens with its concave surface facing the object side. The sixth lens L6 can be a meniscus lens with its convex surface facing the object side. The seventh lens L7 can be a meniscus lens with its convex surface facing the object side. The eighth lens L8 can be a biconvex lens. Properly configuring the object-side and image-side surface shapes of each lens is beneficial for correcting aberrations and ensuring good imaging performance of the infrared zoom lens.

[0058] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 1.0 < |ft×(n-1) / (FNO×R1)| < 3.5, where ft is the focal length of the infrared zoom lens in telephoto mode, n is the refractive index of the center wavelength of the first lens, FNO is the relative F-number of the infrared zoom lens, and R1 is the radius of curvature of the object-side surface of the first lens. By ensuring that the infrared zoom lens satisfies the above condition, it is possible to guarantee that the infrared zoom lens meets the high-resolution image quality requirements of the cooled detector.

[0059] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.1 < |f1 / ft| < 0.4, where f1 is the effective focal length of the first lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the first lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0060] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.1 < |f2 / ft| < 0.5, where f2 is the effective focal length of the second lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the second lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0061] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.01 < |f3 / ft| < 0.1, where f3 is the effective focal length of the third lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the third lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0062] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.02 < |f4 / ft| < 0.07, where f4 is the effective focal length of the fourth lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the fourth lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0063] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.1 < |f5 / ft| < 10, where f5 is the effective focal length of the fifth lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the fifth lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0064] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.2 < |f6 / ft| < 0.8, where f6 is the effective focal length of the sixth lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the sixth lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0065] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.3 < |f7 / ft| < 2.5, where f7 is the effective focal length of the seventh lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the seventh lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0066] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.01 < |f8 / ft| < 0.05, where f8 is the effective focal length of the eighth lens, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the eighth lens is beneficial for correcting aberrations, thereby ensuring that the infrared zoom lens has good imaging performance.

[0067] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.40 < |TTL / ft| < 0.65, where TTL is the axial distance from the object-side surface of the first lens to the image plane, and ft is the focal length of the infrared zoom lens in telephoto mode. Reasonably configuring the ratio of the axial distance from the object-side surface of the first lens to the image plane to the focal length of the infrared zoom lens in telephoto mode helps to reduce the overall optical length of the infrared zoom lens, making its structure more compact and its integration higher, thereby achieving a miniaturized design of the infrared zoom lens.

[0068] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.01 ≤ |f1 / f5| < 0.95, where f1 is the effective focal length of the first lens and f5 is the effective focal length of the fifth lens. Reasonably configuring the ratio of the effective focal length of the first lens to the effective focal length of the fifth lens is beneficial for achieving miniaturization of the infrared zoom lens and ensuring good imaging performance.

[0069] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 20 ≤ ft / fw ≤ 22, where ft is the focal length of the infrared zoom lens in telephoto mode and fw is the focal length of the infrared zoom lens in short focal length mode. By reasonably configuring the ratio of the focal lengths of the infrared zoom lens in telephoto and short focal length modes, a large zoom ratio can be achieved, for example, a zoom ratio of 20 to 22.

[0070] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 300mm ≤ ft ≤ 330mm; and fw ≥ 15mm, where ft is the focal length of the infrared zoom lens in telephoto mode, and fw is the focal length of the infrared zoom lens in telephoto mode. In this example, 15mm ≤ fw ≤ 25mm. Properly configuring the focal length of the infrared zoom lens in both telephoto and telephoto modes enables the infrared zoom lens to have a large zoom ratio and good imaging performance in both telephoto and telephoto modes.

[0071] In an exemplary embodiment, the infrared zoom lens 100 can satisfy: 0.1 ≤ ΔL / TTL ≤ 0.4, where ΔL is the travel distance of the zoom group on the optical axis, and TTL is the axial distance from the object-side surface of the first lens to the image plane. By rationally configuring the ratio of the travel distance of the zoom group on the optical axis to the axial distance from the object-side surface of the first lens to the image plane, the travel distance of the zoom group can be constrained to a small range, reducing the travel requirements of the motor used to drive the zoom group, reducing the design difficulty of the motor, improving the control precision of the motor, and further improving the imaging quality of the infrared zoom lens.

[0072] In an exemplary embodiment, at least two of the first to eighth lenses may be configured as calcium fluoride lenses. Calcium fluoride lenses have a low refractive index, and their use is more advantageous for imaging in infrared zoom lenses.

[0073] In an exemplary embodiment, the infrared zoom lens 100 achieves a zoom range of f15mm to f330mm, with a relative F-number of 3 to 5, and half the diagonal length of the effective pixel area of ​​the image plane (i.e., half-image height) of 6mm to 7mm. Furthermore, the relative F-number can be 4, and the half-image height can be 6.15mm.

[0074] Based on the same concept, this application also provides an infrared thermal imaging system. This infrared thermal imaging system includes the aforementioned infrared zoom lens 100, and also includes a cooled detector located on the image plane of the infrared zoom lens 100. The cooled detector can be, for example, a mid-wave cooled detector. The infrared zoom lens 100 has a zoom ratio of 20 to 22, a zoom range of f15mm to f330mm, a relative F-number of 3 to 5, and a half-image height of 6mm to 7mm, making it compatible with mid-wave cooled detectors with a size of 640×512_15μm. Furthermore, since this infrared thermal imaging system includes the aforementioned infrared zoom lens 100, it possesses the same or similar technical effects as the aforementioned infrared zoom lens 100, which will not be elaborated further here.

[0075] The following describes a specific embodiment of the infrared zoom lens 100 applicable to the above embodiments with reference to the accompanying drawings.

[0076] Example 1

[0077] The following is for reference Figure 1 The infrared zoom lens according to Embodiment 1 of this application is described.

[0078] like Figure 1As shown, the infrared zoom lens 100, along the optical axis from the object side to the image plane (IMA), sequentially includes a front fixed group G1, a zoom group G2, a compensation group G3, a rear fixed group G4, and a focusing group G5. The front fixed group G1 includes a first lens L1 and a second lens L2. The zoom group G2 includes a third lens L3. The compensation group G3 includes a fourth lens L4. The rear fixed group G4 includes a fifth lens L5 and a sixth lens L6. The focusing group G5 includes a seventh lens L7 and an eighth lens L8.

[0079] The first lens L1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens L2 has negative optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens L3 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being concave. The fourth lens L4 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The fifth lens L5 has negative optical power, with its object-side surface S9 being concave and its image-side surface S10 being convex. The sixth lens L6 has positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The seventh lens L7 has positive optical power, with its object-side surface S13 being convex and its image-side surface S14 being concave. The eighth lens L8 has positive optical power, with its object-side surface S15 being convex and its image-side surface S16 being convex. The appropriate selection of the eighth lens L8 can reduce cold reflections in the system.

[0080] The image plane IMA may be equipped with a cooled detector. In other examples, a first optical element, a second optical element, and a cold stop may also be disposed between the eighth lens L8 and the image plane IMA. The first optical element may have an object-side surface S17 and an image-side surface S18. The second optical element may have an object-side surface S19 and an image-side surface S20. The cold stop may have an aperture surface S21. The types of the first and second optical elements can be specifically selected according to the actual application requirements.

[0081] In this embodiment, the zoom range of the infrared zoom lens is 15mm to 315mm. The relative F-number of the infrared zoom lens is 4, and the half-image height is 6.15mm. The absolute value of the effective focal length |f5| of the fifth lens L5 is 50mm. The on-axis distance TTL from the object-side surface of the first lens to the image plane is 141.5mm.

[0082] Table 1 shows the basic parameters of the infrared zoom lens 100 of Embodiment 1, wherein the units for radius of curvature and spacing are millimeters (mm).

[0083]

[0084]

[0085] Table 1

[0086] In this embodiment, when the infrared zoom lens is in telephoto mode, the value of D1 is 45.4mm, the value of D2 is 2.4mm, and the value of D3 is 17.0mm.

[0087] In this embodiment, the image-side surface S6 of the third lens L3, the object-side surface S7 of the fourth lens L4, and the image-side surface S16 of the eighth lens L8 are aspherical surfaces. Aspherical surfaces satisfy the following equation:

[0088]

[0089] 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, and D are the coefficients of the 4th, 6th, 8th, and 10th order terms of the aspherical polynomial. The conic coefficients of S6, S7, and S16 in Example 1, as well as the coefficients of the order terms of the aspherical polynomial, are shown in Table 2.

[0090] S6 0 -1.2709E-05 1.3454E-09 2.7870E-11 -6.0984E-14 S7 0 -6.2474E-06 9.9391E-11 2.2388E-11 -5.4856E-14 S16 0 1.4175E-04 -8.2518E-07 -2.4705E-09 5.6150E-11

[0091] Table 2

[0092] As described above, the infrared zoom lens provided in Embodiment 1 can have a short focal length mode, a medium focal length mode, and a long focal length mode, wherein, Figure 2A This is a schematic diagram of the blur pattern of an infrared zoom lens in short focal length mode. Figure 2B This is a field curvature distortion diagram of an infrared zoom lens in short focal length mode. Figure 3A This is a schematic diagram of the blur pattern of an infrared zoom lens in mid-range focal length mode. Figure 3B This is a field curvature distortion diagram of an infrared zoom lens in mid-range focal length mode. Figure 4A This is a schematic diagram of the blur pattern of an infrared zoom lens in telephoto mode. Figure 4B This is a field curvature distortion diagram of an infrared zoom lens in telephoto mode. (By...) Figure 2A , Figure 3A and Figure 4A It can be seen that, at different focal lengths, the blur spot of the infrared zoom lens reaches the diffraction limit, indicating that the infrared zoom lens has good imaging performance. Figure 2B , Figure 3B and Figure 4B It can be seen that, at different focal lengths, the maximum distortion of the infrared zoom lens is within ±5%, and the field curvature in the meridional and sagittal directions for different wavelengths of light is between ±0.50mm. This means that the infrared zoom lens can achieve small distortion and field curvature at different focal lengths. In summary, the infrared zoom lens provided in Example 1 can correct various aberrations and ensure imaging quality at all focal lengths. The infrared zoom lens provided in Example 1 has good imaging performance during zooming.

[0093] Example 2

[0094] The structure of the infrared zoom lens according to Embodiment 2 of this application is similar to that of the infrared zoom lens in Embodiment 1, that is, it is similar to... Figure 1 Similarly, this application will not elaborate further.

[0095] Specifically, the infrared zoom lens 100, along the optical axis from the object side to the image plane IMA, sequentially includes a front fixed group G1, a zoom group G2, a compensation group G3, a rear fixed group G4, and a focusing group G5. The front fixed group G1 includes a first lens L1 and a second lens L2. The zoom group G2 includes a third lens L3. The compensation group G3 includes a fourth lens L4. The rear fixed group G4 includes a fifth lens L5 and a sixth lens L6. The focusing group G5 includes a seventh lens L7 and an eighth lens L8.

[0096] The first lens L1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens L2 has negative optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens L3 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being concave. The fourth lens L4 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The fifth lens L5 has positive optical power, with its object-side surface S9 being concave and its image-side surface S10 being convex. The sixth lens L6 has negative optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The seventh lens L7 has positive optical power, with its object-side surface S13 being convex and its image-side surface S14 being concave. The eighth lens L8 has positive optical power, with its object-side surface S15 being convex and its image-side surface S16 being convex. The appropriate selection of the eighth lens L8 can reduce cold reflections in the system.

[0097] The image plane IMA may be equipped with a cooled detector. In other examples, a first optical element, a second optical element, and a cold stop may also be disposed between the eighth lens L8 and the image plane IMA. The first optical element may have an object-side surface S17 and an image-side surface S18. The second optical element may have an object-side surface S19 and an image-side surface S20. The cold stop may have an aperture surface S21. The types of the first and second optical elements can be specifically selected according to the actual application requirements.

[0098] In this embodiment, the zoom range of the infrared zoom lens is 15mm to 300mm. The relative F-number of the infrared zoom lens is 4, and the half-image height is 6.15mm. The absolute value of the effective focal length |f5| of the fifth lens L5 is 2632mm. The on-axis distance TTL from the object-side surface of the first lens to the image plane is 138.9mm.

[0099] Table 3 shows the basic parameters of the infrared zoom lens 100 of Embodiment 2, where the units for radius of curvature and spacing are millimeters (mm).

[0100]

[0101]

[0102] Table 3

[0103] In this embodiment, when the infrared zoom lens is in telephoto mode, the value of D1 is 45.2mm, the value of D2 is 3.2mm, and the value of D3 is 18.1mm.

[0104] In this embodiment, the image-side surface S6 of the third lens L3, the object-side surface S7 of the fourth lens L4, and the image-side surface S16 of the eighth lens L8 are aspherical surfaces. The conic coefficients of S6, S7, and S16 in Embodiment 2, as well as the order coefficients of the aspherical polynomials, are shown in Table 4.

[0105] S6 0 -1.2343E-05 -3.9589E-09 8.7504E-11 -2.9641E-13 S7 0 -5.4330E-06 1.3636E-09 1.8484E-11 -5.6635E-14 S16 0 1.6651E-04 -6.9470E-07 -8.3964E-09 2.2249E-10

[0106] Table 4

[0107] As described above, the infrared zoom lens provided in Embodiment 2 can have a short focal length mode, a medium focal length mode, and a long focal length mode, wherein, Figure 5A This is a schematic diagram of the blur pattern of an infrared zoom lens in short focal length mode. Figure 5B This is a field curvature distortion diagram of an infrared zoom lens in short focal length mode. Figure 6A This is a schematic diagram of the blur pattern of an infrared zoom lens in mid-range focal length mode. Figure 6B This is a field curvature distortion diagram of an infrared zoom lens in mid-range focal length mode. Figure 7A This is a schematic diagram of the blur pattern of an infrared zoom lens in telephoto mode. Figure 7B This is a field curvature distortion diagram of an infrared zoom lens in telephoto mode. (By...) Figure 5A , Figure 6A and Figure 7A It can be seen that, at different focal lengths, the blur spot of the infrared zoom lens reaches the diffraction limit, indicating that the infrared zoom lens has good imaging performance. Figure 5B , Figure 6B and Figure 7B It can be seen that, under different focal lengths, the maximum distortion of the infrared zoom lens is within ±5%, and the field curvature in the meridional and sagittal directions for different wavelengths of light is between ±0.50mm. This means that the infrared zoom lens can achieve small distortion and field curvature at different focal lengths. In summary, the infrared zoom lens provided in Example 2 can correct various aberrations and ensure imaging quality at all focal lengths. The infrared zoom lens provided in Example 2 has good imaging performance during zooming.

[0108] Example 3

[0109] The structure of the infrared zoom lens according to Embodiment 3 of this application is similar to that of the infrared zoom lens in Embodiment 1, that is, it is similar to... Figure 1 Similarly, this application will not elaborate further.

[0110] Specifically, the infrared zoom lens 100, along the optical axis from the object side to the image plane IMA, sequentially includes a front fixed group G1, a zoom group G2, a compensation group G3, a rear fixed group G4, and a focusing group G5. The front fixed group G1 includes a first lens L1 and a second lens L2. The zoom group G2 includes a third lens L3. The compensation group G3 includes a fourth lens L4. The rear fixed group G4 includes a fifth lens L5 and a sixth lens L6. The focusing group G5 includes a seventh lens L7 and an eighth lens L8.

[0111] The first lens L1 has positive optical power, with its object-side surface S1 being convex and its image-side surface S2 being concave. The second lens L2 has negative optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens L3 has negative optical power, with its object-side surface S5 being concave and its image-side surface S6 being concave. The fourth lens L4 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The fifth lens L5 has negative optical power, with its object-side surface S9 being concave and its image-side surface S10 being convex. The sixth lens L6 has positive optical power, with its object-side surface S11 being convex and its image-side surface S12 being concave. The seventh lens L7 has positive optical power, with its object-side surface S13 being convex and its image-side surface S14 being concave. The eighth lens L8 has positive optical power, with its object-side surface S15 being convex and its image-side surface S16 being convex. The appropriate selection of the eighth lens L8 can reduce cold reflections in the system.

[0112] The image plane IMA may be equipped with a cooled detector. In other examples, a first optical element, a second optical element, and a cold stop may also be disposed between the eighth lens L8 and the image plane IMA. The first optical element may have an object-side surface S17 and an image-side surface S18. The second optical element may have an object-side surface S19 and an image-side surface S20. The cold stop may have an aperture surface S21. The types of the first and second optical elements can be specifically selected according to the actual application requirements.

[0113] In this embodiment, the zoom range of the infrared zoom lens is 15mm to 330mm. The relative F-number of the infrared zoom lens is 4, and the half-image height is 6.15mm. The absolute value of the effective focal length |f5| of the fifth lens L5 is 105mm. The on-axis distance TTL from the object-side surface of the first lens to the image plane is 149mm.

[0114] Table 5 shows the basic parameters of the infrared zoom lens 100 of Embodiment 3, where the units for radius of curvature and spacing are millimeters (mm).

[0115]

[0116]

[0117] Table 5

[0118] In this embodiment, when the infrared zoom lens is in short focal length mode, the value of D1 is 9.3mm, the value of D2 is 56.8mm, and the value of D3 is 2.0mm.

[0119] In this embodiment, the image-side surface S6 of the third lens L3, the object-side surface S7 of the fourth lens L4, and the image-side surface S16 of the eighth lens L8 are aspherical surfaces. The conic coefficients of S6, S7, and S16 in Embodiment 3, as well as the order coefficients of the aspherical polynomials, are shown in Table 6.

[0120] S6 0 -8.8653E-06 2.0659E-09 1.4008E-12 1.6508E-14 S7 0 -3.9593E-06 1.2142E-09 2.0749E-12 1.9757E-15 S16 0 1.3186E-04 -5.4850E-07 -1.1013E-08 1.6724E-10

[0121] Table 6

[0122] As described above, the infrared zoom lens provided in Embodiment 3 can have a short focal length mode, a medium focal length mode, and a long focal length mode, wherein, Figure 8A This is a schematic diagram of the blur pattern of an infrared zoom lens in short focal length mode. Figure 8B This is a field curvature distortion diagram of an infrared zoom lens in short focal length mode. Figure 9A This is a schematic diagram of the blur pattern of an infrared zoom lens in mid-range focal length mode. Figure 9B This is a field curvature distortion diagram of an infrared zoom lens in mid-range focal length mode. Figure 10A This is a schematic diagram of the blur pattern of an infrared zoom lens in telephoto mode. Figure 10B This is a field curvature distortion diagram of an infrared zoom lens in telephoto mode. (By...) Figure 8A , Figure 9A and Figure 10A It can be seen that, at different focal lengths, the blur spot of the infrared zoom lens reaches the diffraction limit, indicating that the infrared zoom lens has good imaging performance. Figure 8B , Figure 9B and Figure 10B It can be seen that, at different focal lengths, the maximum distortion of the infrared zoom lens is within ±5%, and the field curvature in the meridional and sagittal directions for different wavelengths of light is between ±0.50mm. This means that the infrared zoom lens can achieve small distortion and field curvature at different focal lengths. In summary, the infrared zoom lens provided in Example 3 can correct various aberrations and ensure imaging quality at all focal lengths. The infrared zoom lens provided in Example 3 has good imaging performance during zooming.

[0123] In summary, Figure 7 shows the numerical values ​​of the relevant conditional expressions for Examples 1 to 3.

[0124]

[0125]

[0126] Table 7

[0127] 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 zoom lens, characterized in that, Along the optical axis from the object side to the image plane, the sequence includes: The front fixed assembly includes a first lens with positive optical power and a second lens with negative optical power. The first lens is a meniscus lens with its convex surface facing the object side, and the second lens is a meniscus lens with its convex surface facing the object side. The zoom group includes a third lens with negative optical power, said third lens being a biconcave lens; The compensation group includes a fourth lens with positive optical power, wherein the fourth lens is a biconvex lens; The rear fixed assembly includes a fifth lens with optical power and a sixth lens with optical power, wherein the optical power signs of the fifth and sixth lenses are opposite; the fifth lens is a meniscus lens with its concave surface facing the object side, and the sixth lens is a meniscus lens with its convex surface facing the object side; and The focusing group includes a seventh lens with positive optical power and an eighth lens with positive optical power. The seventh lens is a meniscus lens with its convex surface facing the object side, and the eighth lens is a biconvex lens. The infrared zoom lens has eight lenses with optical power. The positions of the front fixed group and the rear fixed group relative to the image plane are fixed; the distances of the zoom group, the compensation group and the focusing group on the optical axis relative to the front fixed group are adjustable.

2. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.1 < |f1 / ft| < 0.4 Where f1 is the effective focal length of the first lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

3. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.1 < |f² / ft| < 0.5 Where f2 is the effective focal length of the second lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

4. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.01 < |f3 / ft| < 0.1, Where f3 is the effective focal length of the third lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

5. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.02 < |f4 / ft| < 0.07 Where f4 is the effective focal length of the fourth lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

6. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.1 < |f5 / ft| < 10, Where f5 is the effective focal length of the fifth lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

7. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.2 < |f6 / ft| < 0.8 Where f6 is the effective focal length of the sixth lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

8. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.3 < |f7 / ft| < 2.5 Where f7 is the effective focal length of the seventh lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

9. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.01 < |f8 / ft| < 0.05 Where f8 is the effective focal length of the eighth lens, and ft is the focal length of the infrared zoom lens in telephoto mode.

10. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 1.0<|ft×(n-1) / (FNO×R1)|<3.5, Where ft is the focal length of the infrared zoom lens in telephoto mode, n is the center wavelength refractive index of the first lens, FNO is the relative F number of the infrared zoom lens, and R1 is the radius of curvature of the object side surface of the first lens.

11. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.40 < |TTL / ft| < 0.65 Wherein, TTL is the axial distance from the object side of the first lens to the image plane, and ft is the focal length of the infrared zoom lens in telephoto mode.

12. The infrared zoom lens according to claim 2, characterized in that, The infrared zoom lens satisfies: 0.01≤|f1 / f5|<0.95, Where f1 is the effective focal length of the first lens and f5 is the effective focal length of the fifth lens.

13. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 20≤ft / fw≤22, Wherein, ft is the focal length of the infrared zoom lens in telephoto mode, and fw is the focal length of the infrared zoom lens in short focal length mode.

14. The infrared zoom lens according to claim 13, characterized in that, The infrared zoom lens satisfies: fw≥15mm; and 300mm≤ft≤330mm, Wherein, ft is the focal length of the infrared zoom lens in telephoto mode, and fw is the focal length of the infrared zoom lens in short focal length mode.

15. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies: 0.1≤△L / TTL≤0.4 Wherein, △L is the travel distance of the zoom group on the optical axis, and TTL is the axial distance from the object surface of the first lens to the image surface.

16. The infrared zoom lens according to claim 1, characterized in that, At least two of the first to eighth lenses are configured as calcium fluoride lenses.

17. The infrared zoom lens according to claim 1, characterized in that, The infrared zoom lens satisfies one of the following conditions: 0.1<|f1 / ft|≤0.15; 0.30≤|f2 / ft|≤0.33; 0.03≤|f3 / ft|≤0.04; 0.02<|f4 / ft|≤0.05; 0.16≤|f5 / ft|≤8.77; 0.22≤|f6 / ft|≤0.50; 0.47≤| f7 / ft|≤1.04; 0.02≤|f8 / ft|<0.05; 2.20≤|ft×(n-1) / (FNO×R1)|≤2.47; 0.45≤|TTL / ft|≤0.46; 0.01≤|f1 / f5|≤0.92; 0.24≤△L / TTL≤0.26; Wherein, f1 is the effective focal length of the first lens, ft is the focal length of the infrared zoom lens in telephoto mode, f2 is the effective focal length of the second lens, f3 is the effective focal length of the third lens, f4 is the effective focal length of the fourth lens, f5 is the effective focal length of the fifth lens, f6 is the effective focal length of the sixth lens, f7 is the effective focal length of the seventh lens, f8 is the effective focal length of the eighth lens, n is the center wavelength refractive index of the first lens, FNO is the relative F number of the infrared zoom lens, R1 is the radius of curvature of the object-side surface of the first lens, TTL is the axial distance from the object-side surface of the first lens to the image plane, and ΔL is the travel distance of the zoom group on the optical axis.

18. An infrared thermal imaging system, characterized in that, It includes an infrared zoom lens as described in any one of claims 1 to 17 and a mid-wave cooled detector, wherein the mid-wave cooled detector is located on the image plane of the infrared zoom lens.

Images