Infrared zoom lens and infrared thermal imaging system

Abstract

The invention discloses an infrared zoom lens and an infrared thermal imaging system, and the infrared zoom lens sequentially comprises a front fixed group which comprises a first lens with positive focal power and a second lens with negative focal power from an object side to an image plane along an optical axis; the zoom group comprises a third lens with negative focal power; the compensation group comprises a fourth lens with positive focal power; the rear fixed group comprises a fifth lens and a sixth lens, and the positive and negative attributes of the focal power symbols of the fifth lens and the sixth lens are opposite; the focusing group comprises a seventh lens with positive focal power and an eighth lens with positive focal power; the eighth lens is a biconvex lens; the number of the lenses with the focal power of the infrared zoom lens is eight; the positions of the front fixing group and the rear fixing group relative to the image plane are fixed.

Description

Technical Field

[0001] The present application relates to the field of optical devices, and in particular to an eight-element infrared zoom lens and an infrared thermal imaging system. Background Art

[0002] Infrared thermal imaging lenses rely on the thermal radiation of natural objects to form images, have good resistance to external interference, and can image 24 hours a day, even in extreme environments such as rain, snow, fog and haze. Therefore, infrared thermal imaging lenses have increasingly important applications in the field of civilian surveillance.

[0003] Fixed-focus infrared thermal imaging lenses have certain limitations. They are unable to perform tasks in complex scenarios and are prone to losing surveillance targets. Therefore, infrared zoom lenses have become a new research and development trend. Infrared zoom lenses can search over a large field of view and accurately locate targets in a small field of view, making them excellent for various complex surveillance tasks. However, existing infrared zoom lenses suffer from a small zoom ratio and poor imaging performance, which affect and limit their application in the civilian surveillance field. Summary of the Invention

[0004] The present 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] In a first aspect, the present application provides an infrared zoom lens, which comprises, in order from the object side to the image plane along the optical axis: a front fixed group, including a first lens with positive optical power and a second lens with negative optical power; a zoom group, including a third lens with negative optical power; a compensation group, including a fourth lens with positive optical power; a rear fixed group, including a fifth lens with optical power and a sixth lens with optical power, the signs of the optical powers of the fifth lens and the sixth lens being opposite; and a focusing group, including a seventh lens with positive optical power and an eighth lens with positive optical power; the eighth lens is a biconvex lens; wherein the number of lenses with optical power in the infrared zoom lens is eight; 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 the present application, the first lens is a meniscus lens with a convex surface facing the object side; the second lens is a meniscus lens with a 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 a concave surface facing the object side; the sixth lens is a meniscus lens with a convex surface facing the object side; and the seventh lens is a meniscus lens with a convex surface facing the object side.

[0007] According to an exemplary embodiment of the present 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 a telephoto state.

[0008] According to an exemplary embodiment of the present 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 a telephoto state.

[0009] According to an exemplary embodiment of the present 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 a telephoto state.

[0010] According to an exemplary embodiment of the present 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 a telephoto state.

[0011] According to an exemplary embodiment of the present 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 a telephoto state.

[0012] According to an exemplary embodiment of the present 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 a telephoto state.

[0013] According to an exemplary embodiment of the present 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 a telephoto state.

[0014] According to an exemplary embodiment of the present 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 a telephoto state.

[0015] According to an exemplary embodiment of the present application, the infrared zoom lens satisfies the following: 1.0<|ft×(n-1) / (FNO×R1)|<3.5, where ft is the focal length of the infrared zoom lens in a telephoto state, n is the central wavelength refractive index of the first lens element, 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 element.

[0016] According to an exemplary embodiment of the present application, the infrared zoom lens satisfies: 0.40<|TTL / ft|<0.65, where TTL is the on-axis 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 the telephoto state.

[0017] According to an exemplary embodiment of the present 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 the present application, the infrared zoom lens satisfies: 20≤ft / fw≤22, where ft is the focal length of the infrared zoom lens in a telephoto state, and fw is the focal length of the infrared zoom lens in a short focal state.

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

[0020] According to an exemplary embodiment of the present application, the infrared zoom lens satisfies: 0.1≤ΔL / TTL≤0.4, where ΔL is the movement stroke of the zoom group on the optical axis, and TTL is the on-axis distance from the object side surface of the first lens to the image plane.

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

[0022] The second aspect of the present application provides an infrared thermal imaging system, which includes the infrared zoom lens and a medium-wave cooled detector described in the first aspect, wherein the medium-wave cooled detector is located on the image plane of the infrared zoom lens.

[0023] The infrared zoom lens provided herein utilizes eight lenses. By moving the zoom, compensating, and focusing groups, it achieves continuous zooming and ensures clear imaging. Furthermore, the rational allocation of the optical power of each lens helps balance aberrations and improve the imaging performance of the infrared zoom lens. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0025] Figure 1 A schematic structural diagram of an infrared zoom lens according to the present application is shown;

[0026] Figure 2A and Figure 2BSchematic diagram of the diffuse spot and field curvature distortion diagram of the infrared zoom lens in the short-focus state according to Example 1 of the present application are respectively shown;

[0027] Figure 3A and Figure 3B Schematic diagram of the diffused spot and field curvature distortion diagram of the infrared zoom lens in the mid-focus state according to Example 1 of the present application are respectively shown;

[0028] Figure 4A and Figure 4B Schematic diagram of the diffused spot and field curvature distortion diagram of the infrared zoom lens in telephoto state according to Example 1 of the present application are respectively shown;

[0029] Figure 5A and Figure 5B Schematic diagram of the diffuse spot and field curvature distortion diagram of the infrared zoom lens in the short-focus state according to Example 2 of the present application are respectively shown;

[0030] Figure 6A and Figure 6B Schematic diagram of the diffused spot and field curvature distortion diagram of the infrared zoom lens in the mid-focus state according to Example 2 of the present application are respectively shown;

[0031] Figure 7A and Figure 7B Schematic diagram of the diffused spot and field curvature distortion diagram of the infrared zoom lens in telephoto state according to Example 2 of the present application are respectively shown;

[0032] Figure 8A and Figure 8B Schematic diagram of the diffused spot and field curvature distortion diagram of the infrared zoom lens in the short-focus state according to Example 3 of the present application are respectively shown;

[0033] Figure 9A and Figure 9B Schematic diagram of the diffused spots and field curvature distortion diagram of the infrared zoom lens in the middle focus state according to Example 3 of the present application are respectively shown; and

[0034] Figure 10A and Figure 10B Schematic diagram of the diffuse spot and diagram of the field curvature distortion of the infrared zoom lens in telephoto state according to Example 3 of the present application are respectively shown. DETAILED DESCRIPTION

[0035] In order to better understand the present application, various aspects of the present application will be described in more detail with reference to the accompanying drawings. It should be understood that these detailed descriptions are merely descriptions of exemplary embodiments of the present application and are not intended to limit the scope of the present application in any way. Throughout the specification, the same reference numerals refer to the same elements.

[0036] It should be noted that in this specification, the terms "first," "second," "third," etc., are used solely to distinguish one feature from another and do not limit the features. Thus, the first lens discussed below could also be referred to as the second lens or the third lens without departing from the teachings of this application.

[0037] In the drawings, the thickness, size, and shape of the lenses are slightly exaggerated for ease of illustration. Specifically, the shapes of the spherical and aspherical surfaces shown in the drawings are provided by way of example. That is, the shapes of the spherical and aspherical surfaces are not limited to those shown in the drawings. The drawings are for illustration only and are not drawn strictly to scale.

[0038] In this article, the paraxial region refers to the area near the optical axis. If a lens surface is convex and the location of the convex surface is undefined, it means that the lens surface is convex at least in the paraxial region. If a lens surface is concave and the location of the concave surface is undefined, 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 "including," "having," and / or "comprising," when used in this specification, indicate the presence of the stated features, elements, and / or components, but do not preclude the presence or addition of one or more other features, elements, components, and / or combinations thereof. Furthermore, when describing embodiments of the present application, the term "may" is used to mean "one or more embodiments of the present application." Furthermore, the term "exemplary" is intended to refer to an example or illustration.

[0040] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by those skilled in the art to which this application belongs. It should also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and will not be interpreted in an idealized or overly formal sense unless expressly defined as such herein.

[0041] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

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

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

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

[0045] In an exemplary embodiment, reference Figure 1 The variator group G2 can include a third lens L3 with negative optical power, and can move along the optical axis relative to the front fixed group G1. This means that the distance of the variator group G2 relative to the front fixed group G1 on the optical axis is adjustable. By adjusting the distance between the variator 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, the infrared zoom lens 100 can be divided into three states: short focus, medium focus, and long focus, depending on the focal length.

[0046] In an exemplary embodiment, reference Figure 1 The compensation group G3 may include a fourth lens element L4 having positive refractive power and is movable along the optical axis relative to the front fixed group G1. This means that the distance between the compensation group G3 and 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, image plane movement during zooming of the infrared zoom lens 100 can be compensated, effectively compensating for aberrations caused by the movement of the variator group G2.

[0047] In an exemplary embodiment, reference Figure 1 The rear fixed group G4 may include a fifth lens L5 having optical power and a sixth lens L6 having optical power, and the signs of the optical powers 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 embodiment, reference Figure 1 Focusing group G5 can include a seventh lens element L7 with positive refractive power and an eighth lens element L8 with positive refractive power. Focusing group G5 is movable along the optical axis relative to front fixed group G1. That is, the distance of focusing group G5 relative to front fixed group G1 on the optical axis is adjustable. Adjusting the distance of focusing group G5 relative to front fixed group G1 on the optical axis helps ensure clear imaging.

[0049] The infrared zoom lens provided by this application uses eight lenses. By adjusting the distance of the zoom group, compensation group, and focus group relative to the front fixed group on the optical axis, the infrared zoom lens can be switched between short-focus, medium-focus, and long-focus states. While achieving zooming of the infrared zoom lens, the aberrations caused by the zooming process are effectively compensated, thereby ensuring that the infrared zoom lens has good imaging effects at different focal lengths, expanding its application range in complex scenes. In addition, the above-mentioned infrared zoom lens can also produce clear images. Reasonable configuration of the optical focal length of each lens is conducive to balancing aberrations and improving the imaging performance of the infrared zoom lens.

[0050] In an exemplary embodiment, reference Figure 1 The zoom group G2 and the compensation group G3 perform nonlinear motion along opposite directions or opposite directions on the optical axis to switch the infrared zoom lens 100 between a short focus state, a medium focus state, and a long focus state. When the zoom group G2 and the compensation group G3 perform nonlinear motion along opposite directions on the optical axis, the focal length of the infrared zoom lens 100 increases, for example, the infrared zoom lens 100 switches from the short focus state to the medium focus state, or from the medium focus state to the long focus state. When the zoom group G2 and the compensation group G3 perform nonlinear motion along opposite directions on the optical axis, the focal length of the infrared zoom lens 100 decreases, for example, the infrared zoom lens 100 switches from the long focus state to the medium focus state, or from the medium focus state to the short focus state.

[0051] The following describes the movement of the zoom group G2 and the compensation group G3 by taking the increase of the focal length of the infrared zoom lens 100 as an example:

[0052] When the zoom group G2 moves along the optical axis toward the image plane, the compensation group G3 must correspondingly move toward the object side. This effectively increases the distance between the zoom group G2 and the front fixed group G1, while decreasing the distance between the compensation group G3 and the zoom group G2. It is understood that when the zoom group G2 moves toward the image plane, the divergence of the light beam emitted by the front fixed group G1 by the zoom group G2 is relatively delayed. By moving the compensation group G3 toward the object side by a corresponding distance, the time it takes for the compensation group G3 to converge the light beam is changed, thereby changing the overall convergence effect of the lens, thereby increasing the focal length of the infrared zoom lens 100.

[0053] The following uses the example of the reduction of the focal length of the infrared zoom lens 100 to explain the movement of the zoom group G2 and the compensation group G3:

[0054] When the zoom group G2 moves along the optical axis toward the object side, the compensation group G3 must correspondingly move toward the image plane. This effectively reduces the distance between the zoom group G2 and the front fixed group G1, while increasing the distance between the compensation group G3 and the zoom group G2. It is understood that when the zoom group G2 moves toward the object side, the divergence of the light beam emitted by the front fixed group G1 by the zoom group G2 is relatively advanced. By moving the compensation group G3 toward the image plane by a corresponding distance, the timing of the compensation group G3's convergence of the light beam is changed, thereby changing the overall convergence effect of the lens, thereby 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 a predetermined positional relationship to ensure clear images during zooming of the infrared zoom lens 100 .

[0056] In an exemplary embodiment, the front fixed group G1, the zoom group G2, the compensating group G3, the rear fixed group G4, and the focusing group G5 are disposed within a lens barrel. The front fixed group G1 and the rear fixed group G4 are fixed within the lens barrel, while the zoom group G2, the compensating 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 grooves are provided on the interior of the lens barrel, corresponding to the third lens L3, the fourth lens L4, the seventh lens L7, and the eighth lens L8, respectively, to control the movement of the corresponding lenses.

[0057] In an exemplary embodiment, the first lens L1 may be a meniscus lens with a convex surface facing the object side. The second lens L2 may be a meniscus lens with a convex surface facing the object side. The third lens L3 may be a biconcave lens. The fourth lens L4 may be a biconvex lens. The fifth lens L5 may be a meniscus lens with a concave surface facing the object side. The sixth lens L6 may be a meniscus lens with a convex surface facing the object side. The seventh lens L7 may be a meniscus lens with a convex surface facing the object side. The eighth lens L8 may be a biconvex lens. Properly configuring the object-side and image-side surface shapes of each lens facilitates aberration correction and ensures excellent imaging performance of the infrared zoom lens.

[0058] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 1.0 < |ft × (n-1) / (FNO × R1) | < 3.5, where ft is the focal length of the infrared zoom lens in the telephoto position, n is the refractive index of the first lens element at the center wavelength, 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 element. By ensuring that the infrared zoom lens meets this condition, it can ensure that the high-resolution image quality required by the cooled detector is achieved.

[0059] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.1 < |f1 / ft| < 0.4, where f1 is the effective focal length of the first lens element, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the effective focal length of the first lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0060] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.1 < |f2 / ft| < 0.5, where f2 is the effective focal length of the second lens element, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the effective focal length of the second lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0061] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.01 < |f3 / ft| < 0.1, where f3 is the effective focal length of the third lens element, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the effective focal length of the third lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0062] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.02 < |f4 / ft| < 0.07, where f4 is the effective focal length of the fourth lens element, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the effective focal length of the fourth lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0063] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.1 < |f5 / ft| < 10, where f5 is the effective focal length of the fifth lens element, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the effective focal length of the fifth lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0064] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.2 < |f6 / ft| < 0.8, where f6 is the effective focal length of the sixth lens element, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the effective focal length of the sixth lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0065] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.3 < |f7 / ft| < 2.5, where f7 is the effective focal length of the seventh lens element, and ft is the focal length of the infrared zoom lens in telephoto mode. Properly configuring the effective focal length of the seventh lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0066] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.01 < |f8 / ft| < 0.05, where f8 is the effective focal length of the eighth lens element, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the effective focal length of the eighth lens element facilitates aberration correction, thereby ensuring excellent imaging performance of the infrared zoom lens.

[0067] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.40 < |TTL / ft| < 0.65, where TTL is the on-axis distance from the object-side surface of the first lens element to the image plane, and ft is the focal length of the infrared zoom lens in the telephoto position. Properly configuring the ratio of the on-axis distance from the object-side surface of the first lens element to the image plane to the focal length of the infrared zoom lens in the telephoto position helps reduce the overall optical length of the infrared zoom lens, making the infrared zoom lens more compact and highly integrated, thereby achieving a miniaturized design of the infrared zoom lens.

[0068] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.01 ≤ |f1 / f5| < 0.95, where f1 is the effective focal length of the first lens element and f5 is the effective focal length of the fifth lens element. Properly configuring the ratio of the effective focal length of the first lens element to the effective focal length of the fifth lens element facilitates a compact design of the infrared zoom lens and ensures excellent imaging performance.

[0069] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 20 ≤ ft / fw ≤ 22, where ft is the focal length of the infrared zoom lens in the telephoto position, and fw is the focal length of the infrared zoom lens in the short focal position. Properly configuring the ratio of the focal lengths of the infrared zoom lens in the telephoto position to the short focal position allows the infrared zoom lens to have a large zoom ratio, for example, a zoom ratio of 20 to 22.

[0070] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following conditions: 300mm ≤ ft ≤ 330mm; and fw ≥ 15mm, where ft is the focal length of the infrared zoom lens in the telephoto position, and fw is the focal length of the infrared zoom lens in the short-focus position. In this example, 15mm ≤ fw ≤ 25mm. Properly configuring the focal lengths of the infrared zoom lens in the telephoto and short-focus positions enables the infrared zoom lens to achieve a large zoom ratio and excellent imaging performance in both telephoto and short-focus positions.

[0071] In an exemplary embodiment, the infrared zoom lens 100 can satisfy the following condition: 0.1 ≤ ΔL / TTL ≤ 0.4, where ΔL is the travel distance of the zoom group on the optical axis, and TTL is the on-axis distance from the object-side surface of the first lens element to the image plane. By properly configuring the ratio of the travel distance of the zoom group on the optical axis to the on-axis distance from the object-side surface of the first lens element to the image plane, the travel distance of the zoom group can be constrained to a smaller range, reducing the travel requirements of the motor driving the zoom group, simplifying motor design, and improving motor control precision, thereby further enhancing the imaging quality of the infrared zoom lens.

[0072] In an exemplary embodiment, at least two lenses among the first to eighth lenses may be configured as calcium fluoride lenses. Calcium fluoride lenses have a lower refractive index and are more conducive to infrared zoom lens imaging.

[0073] In an exemplary embodiment, the infrared zoom lens 100 achieves a zoom range of f15mm to f330mm, a relative F-number of 3 to 5, and half the diagonal length of the effective pixel area of the image plane (i.e., the 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, the present application also provides an infrared thermal imaging system. The infrared thermal imaging system includes the above-mentioned infrared zoom lens 100, and also includes a cooling detector located on the image plane of the infrared zoom lens 100. The cooling detector can be, for example, a medium-wave cooling 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, which can be adapted to a medium-wave cooling detector with a specification of 640×512_15μm. Moreover, since the infrared thermal imaging system includes the above-mentioned infrared zoom lens 100, it has the same or similar technical effects as the above-mentioned infrared zoom lens 100, which will not be described in detail here.

[0075] A specific embodiment of the infrared zoom lens 100 applicable to the above-mentioned embodiment will be further described below with reference to the accompanying drawings.

[0076] Example 1

[0077] The following reference Figure 1 The infrared zoom lens according to Example 1 of the present application is described.

[0078] like Figure 1As shown, the infrared zoom lens 100 may include, in order from the object side to the image plane IMA along the optical axis, 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 system narration.

[0080] Image plane IMA may be provided with a refrigerated detector. In other examples, a first optical element, a second optical element, and a cold stop may be further provided between the eighth lens element L8 and 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 a stop surface S21. The types of the first and second optical elements may be selected based on actual application requirements.

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

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

[0083]

[0084]

[0085] Table 1

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

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

[0088]

[0089] Wherein, Z is the axial sagittal height in the Z direction of the aspheric surface, r is the distance from the point on the aspheric surface to the optical axis, c is the curvature of the fitted sphere, which is numerically the inverse of the radius of curvature, k is the cone coefficient, and A, B, C, and D are the coefficients of the 4th, 6th, 8th, and 10th order terms of the aspheric polynomial. The cone coefficients of S6, S7, and S16 of Example 1 and the order coefficients of the aspheric polynomial are shown in Table 2.

[0090] Face number k A B C D 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 Example 1 can have a short focus state, a medium focus state, and a long focus state, wherein: Figure 2A This is a schematic diagram of the diffuse spot when the infrared zoom lens is in the short-focus state. Figure 2B This is the field curvature distortion diagram of the infrared zoom lens in the short focal state. Figure 3A This is a schematic diagram of the diffuse spot when the infrared zoom lens is in the mid-focus state. Figure 3B This is the field curvature distortion diagram of the infrared zoom lens in the mid-focus state. Figure 4A This is a schematic diagram of the diffused spots when the infrared zoom lens is in the telephoto state. Figure 4B This is the field curvature distortion diagram of the infrared zoom lens in the telephoto state. Figure 2A 、 Figure 3A and Figure 4A It can be seen that under different focal lengths, the diffuse spot of the infrared zoom lens reaches the diffraction limit, and the infrared zoom lens has a good imaging effect. 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 tangential and sagittal directions for light of different wavelengths is between ±0.50mm. This means that the infrared zoom lens can achieve minimal distortion and field curvature at all focal lengths. In summary, the infrared zoom lens provided in Example 1 can correct for various aberrations and ensure image quality at all focal lengths. The infrared zoom lens provided in Example 1 has excellent imaging performance during zooming.

[0093] Example 2

[0094] The structure of the infrared zoom lens according to Example 2 of the present application is similar to that of the infrared zoom lens according to Example 1, that is, Figure 1 Similarly, this application will not go into details.

[0095] Specifically, the infrared zoom lens 100 may include, in order from the object side to the image plane IMA along the optical axis, 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 proper selection of the eighth lens L8 can reduce system narration.

[0097] Image plane IMA may be provided with a refrigerated detector. In other examples, a first optical element, a second optical element, and a cold stop may be further provided between the eighth lens element L8 and 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 a stop surface S21. The types of the first and second optical elements may be selected based on actual application requirements.

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

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

[0100]

[0101]

[0102] Table 3

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

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

[0105] Face number k A B C D 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 Example 2 can have a short focus state, a medium focus state, and a long focus state, wherein: Figure 5A This is a schematic diagram of the diffuse spot when the infrared zoom lens is in the short-focus state. Figure 5B This is the field curvature distortion diagram of the infrared zoom lens in the short focal state. Figure 6A This is a schematic diagram of the diffuse spot when the infrared zoom lens is in the mid-focus state. Figure 6B This is the field curvature distortion diagram of the infrared zoom lens in the mid-focus state. Figure 7A This is a schematic diagram of the diffused spots when the infrared zoom lens is in the telephoto state. Figure 7B This is the field curvature distortion diagram of the infrared zoom lens in the telephoto state. Figure 5A 、 Figure 6A and Figure 7A It can be seen that under different focal lengths, the diffuse spot of the infrared zoom lens reaches the diffraction limit, and the infrared zoom lens has a good imaging effect. Figure 5B 、 Figure 6B and Figure 7B As can be seen, at different focal lengths, the infrared zoom lens's maximum distortion is within ±5%, and the resulting meridional and sagittal curvatures for light of different wavelengths range from ±0.50 mm. This means that the infrared zoom lens achieves minimal distortion and field curvature at all focal lengths. In summary, the infrared zoom lens provided in Example 2 can correct for various aberrations and guarantee imaging quality at all focal lengths. The infrared zoom lens provided in Example 2 exhibits excellent imaging performance during zooming.

[0108] Example 3

[0109] The structure of the infrared zoom lens according to Example 3 of the present application is similar to that of the infrared zoom lens according to Example 1, that is, Figure 1 Similarly, this application will not go into details.

[0110] Specifically, the infrared zoom lens 100 may include, in order from the object side to the image plane IMA along the optical axis, 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 system narration.

[0112] Image plane IMA may be provided with a refrigerated detector. In other examples, a first optical element, a second optical element, and a cold stop may be further provided between the eighth lens element L8 and 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 a stop surface S21. The types of the first and second optical elements may be selected based on actual application requirements.

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

[0114] Table 5 shows basic parameters of the infrared zoom lens 100 of Example 3, wherein the units of the curvature radius and the pitch are both millimeters (mm).

[0115]

[0116]

[0117] Table 5

[0118] In this embodiment, when the infrared zoom lens is in a short-focus state, the value of D1 is 9.3 mm, the value of D2 is 56.8 mm, and the value of D3 is 2.0 mm.

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

[0120] Face number k A B C D 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 Example 3 can have a short focus state, a medium focus state, and a long focus state, wherein: Figure 8A This is a schematic diagram of the diffuse spot when the infrared zoom lens is in the short-focus state. Figure 8B This is the field curvature distortion diagram of the infrared zoom lens in the short focal state. Figure 9A This is a schematic diagram of the diffuse spot when the infrared zoom lens is in the mid-focus state. Figure 9B This is the field curvature distortion diagram of the infrared zoom lens in the mid-focus state. Figure 10A This is a schematic diagram of the diffused spots when the infrared zoom lens is in the telephoto state. Figure 10B This is the field curvature distortion diagram of the infrared zoom lens in the telephoto state. Figure 8A 、 Figure 9A and Figure 10A It can be seen that under different focal lengths, the diffuse spot of the infrared zoom lens reaches the diffraction limit, and the infrared zoom lens has a good imaging effect. Figure 8B 、 Figure 9B and Figure 10B As can be seen, at different focal lengths, the infrared zoom lens's maximum distortion is within ±5%, and the resulting meridional and sagittal curvatures for light of different wavelengths range from ±0.50 mm. This means that the infrared zoom lens achieves minimal distortion and field curvature at all focal lengths. In summary, the infrared zoom lens provided in Example 3 is capable of correcting various aberrations and ensuring image quality at all focal lengths. The infrared zoom lens provided in Example 3 exhibits excellent imaging performance during zooming.

[0123] In summary, FIG7 shows the numerical values of the relevant conditional expressions of Examples 1 to 3.

[0124]

[0125]

[0126] Table 7

[0127] The above description is merely a preferred embodiment of the present application and an illustration 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 the technical solutions formed by the specific combination of the above-mentioned technical features, but also encompasses other technical solutions formed by any combination of the above-mentioned technical features or their equivalents without departing from the inventive concept. For example, a technical solution formed by replacing the above-mentioned features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. Infrared zoom lens, characterized in that, Along the optical axis from the object side to the image plane, they include: a front fixed group including a first lens having positive optical power and a second lens having negative optical power; a zoom group including a third lens having negative optical power; a compensation group including a fourth lens having positive refractive power; a rear fixed group comprising a fifth lens having optical power and a sixth lens having optical power, wherein the signs of the optical powers of the fifth lens and the sixth lens are opposite in positive and negative properties; and A focusing group comprising a seventh lens having positive focal power and an eighth lens having positive focal power; 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 focus adjustment group relative to the front fixed group on the optical axis are adjustable.

2. The infrared 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 meniscus lens with a 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 a concave surface facing the object side; The sixth lens is a meniscus lens with a convex surface facing the object side; and The seventh lens is a meniscus lens with a convex surface facing the object side.

3. The infrared zoom lens according to claim 1 or 2, characterized in that: The infrared zoom lens meets the following requirements: 0.01<|f3 / ft|<0.1, Wherein, f3 is the effective focal length of the third lens, and ft is the focal length of the infrared zoom lens in the telephoto state.

4. The infrared zoom lens according to claim 1 or 2, characterized in that: The infrared zoom lens meets the following requirements: 0.02<|f4 / ft|<0.07, Wherein, f4 is the effective focal length of the fourth lens, and ft is the focal length of the infrared zoom lens in the telephoto state.

5. The infrared zoom lens according to claim 1 or 2, characterized in that: The infrared zoom lens meets the following requirements: 0.1<|f5 / ft|<10, Wherein, f5 is the effective focal length of the fifth lens, and ft is the focal length of the infrared zoom lens in the telephoto state.

6. The infrared zoom lens according to claim 1 or 2, characterized in that: The infrared zoom lens meets the following requirements: 0.01≤|f1 / f5|<0.95, Wherein, f1 is the effective focal length of the first lens, and f5 is the effective focal length of the fifth lens.

7. The infrared zoom lens according to claim 1 or 2, characterized in that: The infrared zoom lens meets the following requirements: 20≤ft / fw≤22, Wherein, ft is the focal length of the infrared zoom lens in the telephoto state, and fw is the focal length of the infrared zoom lens in the short focal state.

8. The infrared zoom lens according to claim 1 or 2, characterized in that: The infrared zoom lens meets the following requirements: 0.1≤△L / TTL≤0.4, Wherein, ΔL is the movement stroke of the zoom group on the optical axis, and TTL is the on-axis distance from the object side of the first lens to the image plane.

9. The infrared zoom lens according to claim 1 or 2, characterized in that: At least two lenses among the first to eighth lenses are configured as calcium fluoride lenses.

10. An infrared thermal imaging system, characterized in that: The infrared zoom lens and the medium-wave cooled detector are included according to any one of claims 1 to 9, wherein the medium-wave cooled detector is located on the image plane of the infrared zoom lens.

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