A 22.5mm-102mm long-wave infrared continuous zoom lens

Abstract

This invention discloses a 22.5mm-102mm long-wave infrared continuous zoom lens, comprising a front fixed group, a zoom group, a compensation group, and a focusing group arranged sequentially along the transmission direction of the incident beam; each of the front fixed group, zoom group, compensation group, and focusing group has a lens; the front fixed group is a meniscus lens with positive optical power, the first object-side surface is convex, and the first image-side surface is concave; the zoom group is a meniscus lens with negative optical power, the second object-side surface is convex, and the second image-side surface is concave; the compensation group is a meniscus lens with positive optical power, the third object-side surface is convex, the third image-side surface is concave, and the second image-side surface is concave; the focusing group is a meniscus lens with positive optical power, the fourth object-side surface is convex, and the fourth image-side surface is concave; and satisfies 0.3 / mm < TTL / ImgH / f < 1.8 / mm and 1.00 < FNO < 1.25. The present invention provides a 22.5mm-102mm long-wave infrared continuous zoom lens with high pixel resolution and adaptability to outdoor environments.

Description

Technical Field

[0001] This invention relates to a 22.5mm-102mm long-wave infrared continuous zoom lens, belonging to the field of infrared optical imaging technology. Background Technology

[0002] Infrared optical imaging technology was first applied to military reconnaissance, and continuous zoom lenses in infrared optical imaging primarily ensure clear observation of targets at different distances by changing the lens's focal length. Currently, many infrared continuous zoom lenses, in order to save costs, often reduce the transmission function quality, resulting in decreased lens contrast. Furthermore, existing continuous zoom lenses require a large number of lenses and are bulky. For example, patent application number 202111624703.8 discloses a continuous zoom camera lens that requires four lenses in the front fixed group, four lenses in the zoom group, three lenses in the rear fixed group, and two lenses in the compensation group. Although this reduces the lens size to some extent, it still requires 13 lenses. How to achieve good imaging quality in an infrared optical continuous zoom lens with a small size and high zoom capability is a pressing problem that needs to be solved. Summary of the Invention

[0003] This invention provides a 22.5mm-102mm long-wave infrared continuous zoom lens that can be paired with an infrared thermal imaging module with a 640*512 12um detector. While improving imaging quality, it can maximize the suitability for outdoor use.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] A 22.5mm-102mm long-wave infrared continuous zoom lens includes a front fixed group, a zoom group, a compensation group, and a focusing group arranged sequentially along the transmission direction of the incident beam; each of the front fixed group, zoom group, compensation group, and focusing group has a lens; along the transmission direction of the incident beam, the two sides of the front fixed group are respectively the first object-side side and the first image-side side, the two sides of the zoom group are respectively the second object-side side and the second image-side side, the two sides of the compensation group are respectively the third object-side side and the third image-side side, and the two sides of the focusing group are respectively the fourth object-side side and the fourth image-side side.

[0006] The front fixed group is a meniscus lens with positive optical power, the first object side is convex and the first image side is concave;

[0007] The zoom group is a meniscus lens with negative optical power, the second object side is concave, and the second image side is concave.

[0008] The compensation group is a meniscus lens with positive optical power, the third object side is convex and the third image side is concave.

[0009] The focusing group is a meniscus lens with positive optical power, the fourth object side is convex, and the fourth image side is concave; the 22.5mm-102mm long-wave infrared continuous zoom lens satisfies the following relationship: 0.3 / mm < TTL / ImgH / f < 1.8 / mm and 1.00 < FNO < 1.25; where TTL is the distance from the first object side to the image plane of the zoom lens on the optical axis, ImgH is half the image height of the zoom lens, f is the effective focal length of the zoom lens, and FNO is the aperture number of the zoom lens.

[0010] The aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens can reasonably control the total length of the infrared optical continuous zoom lens, while ensuring a sufficiently large aperture to receive more light, enhance the clarity and contrast of the lens image, effectively control the direction of light, reduce system aberrations, and improve image quality.

[0011] During imaging, light enters the front fixed group, zoom group, compensation group and focusing group sequentially from the side of the first object, and finally forms an image on the imaging plane of the zoom lens.

[0012] There is one lens each in the front fixed group, zoom group, compensation group and focusing group, for a total of 4 lenses. The number of lenses is small, the size is small and the weight is light.

[0013] To further improve image quality, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens satisfies the following relationship: 0.4 < |f12 / f| < 2; where f12 is the combined focal length of the front fixed group and the zoom group, and f is the lens focal length. This effectively controls the ratio of the combined focal length of the front fixed group and the zoom group to the effective focal length of the infrared optical continuous zoom lens. Lengthening the front group and the focal length helps reduce the introduction of aberrations.

[0014] To ensure that the focal length design requirements are met, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens satisfies the following relationship: 1.5 < |f23 / f| < 11; where f23 is the combined focal length of the zoom group and the compensation group, and f is the lens focal length. This effectively controls the ratio of the combined focal length of the zoom group and the compensation group to the effective focal length of the infrared optical continuous zoom lens, shortening the time required for the rear group and focal length to effectively match the front combined focal length, thereby ensuring that the overall focal length meets the design requirements.

[0015] To improve environmental adaptability, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens has a DLC film coated on its first side. This significantly enhances the environmental adaptability of the infrared optical continuous zoom lens, effectively reducing the impact of outdoor dust storms on the lens, while also minimizing the corrosive effects of salt spray environments. The material used for the front fixing assembly in this application is germanium, which can reliably bond with the DLC film, solving the problem of easy detachment of the DLC film from chalcogenide glass.

[0016] To further enhance environmental adaptability, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens uses germanium in its front fixed group, zoom group, compensation group, and focusing group. That is, the lens structure is GE+GE+GE+GE. This structure offers excellent stability because germanium single crystals have significantly higher density than materials like chalcogenide glass, thus contributing to its environmental adaptability.

[0017] To improve imaging quality, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens satisfies the following relationship: 0.1 < CT4 / BF < 0.3; where CT4 is the center thickness of the focusing group on the optical axis, and BF is the minimum distance from the image side of the focusing group to the image plane of the zoom lens on the optical axis. Satisfying this relationship allows for reasonable control of the focusing group and its distance to the image plane, which helps reduce the molding difficulty and surface shape error of the focusing group, controls distortion, and thus improves the imaging quality of the zoom lens. Ensuring a reasonable distance between the focusing group and the image plane also prevents the focusing group from being too close to the detector target surface when matching the zoom lens with the detector core, thus affecting the assembly of the imaging module and improving the compatibility of this infrared optical continuous zoom lens with different detectors.

[0018] To facilitate manufacturing while meeting imaging requirements, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens satisfies the following relationships: 10 < SD11 / CT1 < 16; 11 < SD21 / CT2 < 15; where SD11 is the maximum effective half-aperture of the first object-transmitting side, SD21 is the maximum effective half-aperture of the second object-side side, CT1 is the center thickness of the front fixed group on the optical axis, and CT2 is the center thickness of the zoom group on the optical axis. This allows for reasonable control of the ratio of the maximum effective half-aperture of the object-side side of the front fixed group, the object-side side of the zoom group, and the image-side side of the zoom group to the center thickness of the front fixed group and the zoom group on the optical axis, ensuring the rationality of the thickness settings of the front fixed group and the zoom group, i.e., controlling the diameter-to-thickness ratio, thereby improving the manufacturing rationality of the front fixed group and the zoom group.

[0019] To improve image quality, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens satisfies the following relationship: 1 < CT4 / ImgH < 1.5; where CT4 is the center thickness of the focusing group on the optical axis, and ImgH is half the image height of the zoom lens. This allows for reasonable control of the ratio of the center thickness of the focusing group to the image height radius of the zoom lens. This not only ensures reasonable control of the center thickness of the focusing group but also guarantees a large image height for the infrared optical continuous zoom lens, while effectively reducing system field curvature.

[0020] To further improve image quality, the aforementioned 22.5mm-102mm long-wave infrared continuous zoom lens features a spherical first object-side surface and a spherical first image-side surface; a spherical second object-side surface and a spherical second image-side surface; a spherical third object-side surface and a diffractive surface on the third image-side surface; and a spherical fourth object-side surface and a aspherical fourth image-side surface. This design saves costs, as the large aperture of the first lens and double-sided polishing are significantly cheaper than turning. Placing the diffractive surface on the third image-side surface helps converge edge light rays, giving the infrared optical continuous zoom lens a reasonable image height or field of view. Finally, adding an aspherical surface on the fourth image-side surface helps correct aberrations, thus improving image quality.

[0021] To ensure image quality, the center thickness of the front fixed group is 7.0~8.0mm; the center thickness of the zoom group is 2.0~3.0mm; the center thickness of the compensation group is 2.0~3.0mm; and the center thickness of the focusing group is 5.0~6.0mm. At a focal length of 22.5mm, the center spacing between the front fixed group and the zoom group is 21±2mm, and the center spacing between the zoom group and the compensation group is 51±2mm. At a focal length of 102mm, the center spacing between the front fixed group and the zoom group is 57±2mm, and the center spacing between the zoom group and the compensation group is 15.8±2mm. The radius of curvature of the first object side is 110~150mm, the radius of curvature of the first image side is 200~250mm, and the radius of curvature of the second object side is -160~160mm. -130mm, the radius of curvature of the second image side is 110~175mm; the radius of curvature of the third object side is 90~125mm, the radius of curvature of the third image side is 150~220mm; the radius of curvature of the fourth object side is 50~100mm, and the radius of curvature of the fourth image side is 100~160mm.

[0022] The tolerance fit between the lens and structural components of the aforementioned infrared optical continuous zoom lens satisfies the following relationships: -0.03≦△L1+△L2+△L3≦0.03; 0.01≦∣ΔΦ1∣≦0.04; 0.01≦∣ΔΦ2∣≦0.03; 0.01≦∣ΔΦ3∣≦0.03; 0.01≦∣ΔΦ4∣≦0.03;

[0023] Wherein, △L1 is the distance tolerance between the side edge of the first image and the side edge of the second image; △L2 is the distance tolerance between the side edge of the second image and the side edge of the third image; △L3 is the distance tolerance between the side edge of the third image and the side edge of the fourth image; ΔΦ1 is the diameter tolerance of the front fixed group; ΔΦ2 is the diameter tolerance of the zoom group; ΔΦ3 is the diameter tolerance of the compensation group; and ΔΦ4 is the diameter tolerance of the focusing group. This tolerance distribution, while maximizing the protection of the lens from thermal expansion and contraction caused by high and low temperatures, significantly reduces the time required for lens assembly and centering. Furthermore, within the current precision requirements achievable in the machining industry, it reasonably controls the lens spacing, reducing the risks to the lens surface caused by manual adjustment of the spacing.

[0024] Any techniques not mentioned in this invention are based on existing technologies.

[0025] This invention provides a 22.5mm-102mm long-wave infrared continuous zoom lens with high pixel density and adaptability to outdoor environments. Due to the low coefficient of friction of the DLC film (only 0.2), it has strong wear resistance compared to ordinary lenses of the same type (0.5). At the same time, it has strong temperature adaptability, reaching -45℃ to 80℃ without changing image quality. It uses fewer lenses, is small in size and light in weight, and has a simple and compact structure. The MTF can approach the diffraction limit. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the optical system of the 22.5mm long-wave infrared continuous zoom lens in Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of the optical system of the 102mm long-wave infrared continuous zoom lens in Embodiment 1 of the present invention;

[0028] Figure 3 shows the image quality of the 22.5mm-102mm long-wave infrared continuous zoom lens in Embodiment 1 of the present invention at a focal length of 22.5mm.

[0029] Figure 4 shows the image quality of the 22.5mm-102mm long-wave infrared continuous zoom lens at a focal length of 65mm in Embodiment 1 of the present invention.

[0030] Figure 5 shows the image quality of the 22.5mm-102mm long-wave infrared continuous zoom lens in Embodiment 1 of the present invention at a focal length of 102mm.

[0031] Figure 6 shows the image quality of a traditional 25mm-100mm long-wave infrared optical continuous zoom lens at a focal length of 25mm.

[0032] Figure 7 Image quality diagram of a traditional 25mm-100mm long-wave infrared optical continuous zoom lens at a focal length of 65mm.

[0033] Figure 8 Image quality diagram of a traditional 25mm-100mm long-wave infrared optical continuous zoom lens at a focal length of 100mm;

[0034] Figure 9 is a schematic diagram of the optical system of the 22.5mm-102mm long-wave infrared continuous zoom lens in Embodiment 2 of the present invention;

[0035] Figure 10 shows the image quality of the 22.5mm-102mm long-wave infrared continuous zoom lens in Embodiment 2 of the present invention at a focal length of 22.5mm.

[0036] Figure 11 shows the image quality of the 22.5mm-102mm long-wave infrared continuous zoom lens at a focal length of 65mm in Embodiment 2 of the present invention.

[0037] Figure 12 shows the image quality of the 22.5mm-102mm long-wave infrared continuous zoom lens at a focal length of 100mm in Embodiment 2 of the present invention.

[0038] Figure 13 shows the low temperature (-40℃) of the 22.5mm-102mm long-wave infrared continuous zoom lens in Embodiment 2 of the present invention. Figure 13-1 ) and high temperature 60℃ ( Figure 13-2 (spot chart);

[0039] In the figure, 1 represents L1 (front fixed group), L2 (zoom group), L3 (compensation group), L4 (focusing group), L5 (detector protection window), and L6 (image plane). Detailed Implementation

[0040] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0041] like Figure 1 , Figure 2 As shown, the 22.5mm-102mm long-wave infrared continuous zoom lens (hereinafter referred to as zoom lens 001) includes a front fixed group L1, a zoom group L2, a compensation group L3, and a focusing group L4 arranged sequentially from the object side to the image side along the optical axis o. During imaging, light enters the front fixed group L1, zoom group L2, compensation group L3, and focusing group L4 sequentially from the object side S1 of the front fixed group L1, and finally forms an image on the imaging plane L6 of the zoom lens 001. The front fixed group L1 has positive optical power, the zoom group L2 has negative optical power, and both the compensation group L3 and the focusing group L4 have positive optical power.

[0042] The first object-side surface S1 of the front fixed group L1 is convex near the optical axis o, and the first image-side surface S2 is concave near the optical axis o; the second object-side surface S3 of the zoom group L2 is concave near the optical axis o, and the second image-side surface S4 is concave near the optical axis o; the third object-side surface S5 of the compensation group L3 is convex near the optical axis o, and the third image-side surface S6 is concave near the optical axis o; the third object-side surface S7 of the focusing group L4 is convex near the optical axis o, and the fourth image-side surface S8 is concave near the optical axis o.

[0043] By setting the front fixed group L1 to have a positive optical power, it is beneficial to reduce the edge thickness of the lens element while ensuring that the light is not excessively deflected, thereby reducing spherical aberration. By setting the first image-side surface S1 of the front fixed group L1 to be concave at the near-optical axis o, it is beneficial to reduce the positive optical power of the front fixed group L1, further providing a reasonable incident angle for edge light rays, thus giving the zoom lens 001 a reasonable field of view. By setting the zoom group L2 to have a negative optical power and its second object-side surface S3 to be concave, the light rays converged by the front fixed group L1 can be gradually diffused. Setting the third image-side surface S6 of the compensation group L3 to be concave helps to correct distortion, astigmatism, and field curvature, thereby improving image quality.

[0044] In some embodiments, the zoom lens 001 further includes an aperture stop, which can be disposed between the second image-side surface S4 of the zoom group L2 and the third object-side surface of the compensation group L3, or it can be placed on the third image-side surface of the compensation group L3. The optical surface can be chosen as the aperture stop surface depending on the actual situation.

[0045] In some embodiments, the zoom lens 001 satisfies the following relationships: 0.3 / mm < TTL / ImgH / f < 1.8 / mm and 1.00 < FNO < 1.25; where TTL is the distance on the optical axis from the first object side to the image plane of the zoom lens, ImgH is half the image height of the zoom lens, f is the effective focal length of the zoom lens, and FNO is the aperture number of the zoom lens. This allows for reasonable control of the total length of the infrared optical continuous zoom lens, while ensuring a sufficiently large aperture to receive more light, enhancing the sharpness and contrast of the lens image. It also effectively controls the light path, reduces system aberrations, and improves image quality. During imaging, light enters the front fixed group, zoom group, compensation group, and focusing group sequentially from the first object side, and finally forms an image on the imaging plane of the zoom lens. This effectively controls the light path, reduces system aberrations, and improves image quality. When TTL / ImgH / f ≥ 1.8, the total length of the zoom lens 001 is large, and it is difficult to achieve a large field of view design. When TTL / ImgH / f≤0.3, the total length of zoom lens 001 is small and the field of view is large, and the focal length is relatively large. The image quality of the design will be reduced, and the lens shape will be more curved, making it difficult to process. This leads to a decrease in the production yield of zoom lens 001 and an increase in production costs.

[0046] In some embodiments, as an optional implementation, the side of the front fixed assembly of the zoom lens 001 is coated with a DLC film. This greatly enhances the environmental adaptability of the infrared optical continuous zoom lens, effectively reducing the impact of outdoor sandstorms on the lens, while also reducing the corrosive effect of salt spray environments. When only an AR film is selected, although there is an increase of about 4% in transmittance, its corrosion resistance and wind and sand resistance will be significantly reduced, making it completely unsuitable for use in harsh outdoor environments. If the front fixed assembly is replaced with a DLC film design using chalcogenide glass, due to the large coefficient of thermal expansion of chalcogenide glass, the film layer has a certain probability of local peeling off after a period of time. Furthermore, chalcogenide glass itself has weak corrosion resistance, which can easily lead to lens damage and affect its use.

[0047] In some embodiments, the zoom lens 001 satisfies the following relationships: 10 < SD11 / CT1 < 16; 11 < SD21 / CT2 < 15; where SD11 is the maximum effective half-aperture of the first object-transmitting side, SD21 is the maximum effective half-aperture of the second object-side side, CT1 is the center thickness of the front fixed group on the optical axis, and CT2 is the center thickness of the zoom group on the optical axis. This allows for reasonable control of the ratio of the maximum effective half-aperture of the object-side side of the front fixed group, the object-side side of the zoom group, and the image-side side of the zoom group to the center thickness of the front fixed group and the zoom group on the optical axis, ensuring the rationality of the thickness settings of the front fixed group and the zoom group, i.e., controlling the diameter-to-thickness ratio, thereby improving the processing rationality of the front fixed group and the zoom group. When SD11 / CT1≥16 and SD21 / CT2≥15, the aspect ratios of the front fixed group L1 and the zoom group L2 of zoom lens 001 are too large, making them prone to deformation during manufacturing, affecting processing efficiency. Furthermore, after lens assembly, they are susceptible to deformation under tension, impacting image quality. When SD11 / CT1≤10 and SD21 / CT2≤11, the lens aspect ratios are too small, resulting in increased lens weight, wasted costs, and an excessively heavy product.

[0048] In some embodiments, the zoom lens 001 satisfies the following relationship: 0.4 < |f12 / f| < 2; where f12 is the combined focal length of the front fixed group and the zoom group, and f is the lens focal length. This effectively controls the ratio of the combined focal length of the front fixed group and the zoom group to the effective focal length of the infrared optical continuous zoom lens. Lengthening the front group and focal length helps reduce the introduction of aberrations. When f12 / f ≥ 2, the front focal length is too low, and the light rays enter the front fixed group L1 and the zoom group L2 and contract slowly, transferring all the processing sensitivity to the rear end, which is not conducive to assembly. When f12 / f ≤ 0.4, the combined focal length of the front fixed group L1 and the zoom group L2 is small, resulting in excessive refraction of large-angle light rays. This puts too much pressure on the front fixed group L1 and the zoom group L2, especially when there is only one aspherical surface, which is not conducive to the balanced distribution of aberrations.

[0049] In some embodiments, the zoom lens 001 satisfies the following relationship: 1.5 < |f23 / f| < 11; where f23 is the combined focal length of the zoom group and the compensation group, and f is the lens focal length. This effectively controls the ratio of the combined focal length of the zoom group and the compensation group to the effective focal length of the infrared optical continuous zoom lens, shortening the effective coordination between the rear group and the front group focal length, thereby ensuring that the overall focal length meets the design requirements. When f23 / f ≥ 11, the rear optical focal length is too low, and the light entering the zoom group L2 and the compensation group L3 contracts slowly, transferring all the processing sensitivity to the front end, which is not conducive to processing and manufacturing. When f23 / f ≤ 1.5, the combined focal length of the zoom group L2 and the compensation group L3 is small, resulting in excessive refraction of large-angle light, causing the zoom group L2 and the compensation group L3 to bear too much pressure. When the aspherical surfaces are too dense, high-order aberrations are easily generated, affecting the image quality.

[0050] In some embodiments, the zoom lens 001 satisfies the following relationship: 1 < CT4 / ImgH < 1.5; where CT4 is the center thickness of the focusing group on the optical axis, and ImgH is half the image height of the zoom lens. This allows for reasonable control of the ratio of the center thickness of the focusing group to the image height radius of the zoom lens, not only controlling the center thickness of the focusing group but also ensuring a large image height for the infrared optical continuous zoom lens, while effectively reducing system field curvature. When CT4 / ImgH ≤ 1, the center thickness of the focusing group L4 is small, which is not conducive to spherical aberration correction, and an excessively thin center thickness is also detrimental to manufacturing. When CT4 / ImgH ≥ 1.5, the center thickness of the focusing group L4 is too large, which is not conducive to shortening the overall length of the zoom lens 001 and will lead to increased costs.

[0051] In some embodiments, the zoom lens 001 satisfies the following relationship: 0.1 < CT4 / BF < 0.3; where CT4 is the center thickness of the focusing group on the optical axis, and BF is the minimum distance from the image side of the focusing group to the image plane of the zoom lens on the optical axis. Satisfying this relationship allows for reasonable control of the focusing group and the distance from the focusing group to the image plane, which helps reduce the molding difficulty and processing surface error of the focusing group, helps control distortion, thereby improving the imaging quality of the zoom lens, ensuring a reasonable distance between the focusing group and the image plane, and also preventing the focusing group from being too close to the detector target surface when the zoom lens is matched with the detector core, thus affecting the assembly of the imaging module and improving the compatibility of the infrared optical continuous zoom lens with different detectors. When CT4 / BF≥0.3, the center thickness of the focusing group is too thick, which is not conducive to reducing the weight of the zoom lens 001. At the same time, the back cutoff of the system is too short, and the compensation group is too close to the detector target surface, which is not conducive to the assembly and cooperation between the zoom lens 001 and the detector. This may cause a mismatch between the zoom lens 001 and the detector, resulting in the inability to form a clear image quality, or even the complete inability to form an image.

[0052] In some embodiments, the first object side and the first image side of the front fixed group of the zoom lens 001 are spherical. This design saves costs because the cost of double-sided polishing is much lower than the cost of turning due to the large aperture of the first lens.

[0053] In some embodiments, the second object side of the zoom lens 001 zoom group is aspherical, and the second image side is spherical. This design is beneficial for quickly reducing the spherical aberration introduced by the front fixed group and can smoothly compress light and make it output smoothly.

[0054] In some embodiments, the third object-side surface of the zoom lens 001 compensation group is spherical, and the third image-side surface is a diffraction surface. Adding a diffraction surface is equivalent to modifying the material surface. One diffraction surface is equivalent to saving at least one lens element. Therefore, this design not only saves materials but also effectively controls aberrations such as chromatic aberration and distortion. If a diffraction surface is not designed, aberrations such as spherical aberration are difficult to control in this model of product, resulting in larger aberrations and reduced image quality. Alternatively, to ensure image quality, the lens thickness may be increased, and the lens shape may be changed to increase optical power, which increases the manufacturing difficulty.

[0055] In some embodiments, the fourth object side of the focusing group of the zoom lens 001 is spherical, and the fourth image side is aspherical. This design allows the infrared optical continuous zoom lens to have a reasonable image height or field of view, and the aspherical surface of the fourth image side helps to correct aberrations, thereby improving image quality.

[0056] In some embodiments, the tolerance fit between the zoom lens 001 and the structural components satisfies the following relationships: -0.03≦△L1+△L2+△L3≦0.03; 0.01≦∣ΔΦ1∣≦0.04; 0.01≦∣ΔΦ2∣≦0.03; 0.01≦∣ΔΦ3∣≦0.03; 0.01≦∣ΔΦ4∣≦0.03;

[0057] Wherein, △L1 is the distance tolerance between the side edge of the first image and the side edge of the second image; △L2 is the distance tolerance between the side edge of the second image and the side edge of the third image; △L3 is the distance tolerance between the side edge of the third image and the side edge of the fourth image; ΔΦ1 is the diameter tolerance of the front fixed group; ΔΦ2 is the diameter tolerance of the zoom group; ΔΦ3 is the diameter tolerance of the compensation group; and ΔΦ4 is the diameter tolerance of the focusing group. This tolerance distribution, while maximizing the protection of the lens from thermal expansion and contraction caused by high and low temperatures, significantly reduces the time required for lens assembly and centering. Furthermore, within the current precision requirements achievable in the machining industry, it reasonably controls the lens spacing, reducing the risks to the lens surface caused by manual adjustment of the spacing.

[0058] When |ΔΦ1| < 0.01, |ΔΦ2| < 0.01, and |ΔΦ3| < 0.01, the tolerance is too tight, increasing processing costs. Furthermore, due to thermal expansion and contraction, structural expansion may cause stress on the lens, potentially leading to lens breakage. Conversely, when |ΔL1+ΔL2+ΔL3| > 0.03, |ΔΦ1| > 0.03, |ΔΦ2| > 0.03, and |ΔΦ3| > 0.03, the tolerance is too loose, increasing assembly difficulty and working time. Moreover, excessively large gaps make it difficult to guarantee process accuracy, posing potential risks.

[0059] The zoom lens 001 of this embodiment will be described in detail below with reference to specific parameters. Example 1

[0060] like Figure 1 , Figure 2 As shown, the 22.5mm-102mm long-wave infrared continuous zoom lens includes a front fixed group L1, a zoom group L2, a compensation group L3, and a focusing group L4 arranged sequentially along the optical axis o from the object side to the image side. Each of the front fixed group L1, zoom group L2, compensation group L3, and focusing group L4 has one lens. During imaging, light enters from the object side S1 of the front fixed group L1, passes through the front fixed group L1, zoom group L2, compensation group L3, and focusing group L4 in sequence, and finally forms an image on the imaging plane L6 of the zoom lens 001. Among them, the front fixed group L1 has positive optical power, the zoom group L2 has negative optical power, and the compensation group L3 and focusing group L4 both have positive optical power. The first object-side surface S1 of the front fixed group L1 is convex near the optical axis o, and the first image-side surface S2 is concave near the optical axis o; the second object-side surface S3 of the zoom group L2 is concave near the optical axis o, and the second image-side surface S4 is concave near the optical axis o; the third object-side surface S5 of the compensation group L3 is convex near the optical axis o, and the third image-side surface S6 is concave near the optical axis o; the third object-side surface S7 of the focusing group L4 is convex near the optical axis o, and the fourth image-side surface S8 is concave near the optical axis o. All four optical groups are made of germanium single crystal, with the first object-side surface coated with a DLC film and the other surfaces coated with an AR film.

[0061] Specifically, taking zoom lens 001 with a zoom focal length of f = 22.5mm~102mm, aperture FNO = 1.2, field of view FOV = 24.6~6.2deg, light transmission band 8μm~12μm, center wavelength 10μm, and total optical length TTL = 196mm as an example, its ImgH is 5mm (half height), f12 is -43mm, f23 is -222mm, f34 is 61mm, CT3 is 2.7mm, CT4 is 5.4mm, SD11 is 103mm, CT1 is 7.5mm, SD21 is 33mm, CT2 is 2.7mm, BF is 42mm, ΔΦ1 is 0.03mm, ΔΦ2 is 0.02mm, ΔΦ3 is 0.02mm, and ΔΦ4 is 0.02mm. Other parameters of zoom lens 001 are given in Table 1 below. In this arrangement, the elements along the optical axis o of the zoom lens 001, from the object side to the image side, are arranged sequentially from top to bottom according to Table 1. In Table 1, D represents the diameter of the object-side or image-side surface of the corresponding surface number, and H represents the center distance from the current surface to the next surface, i.e., the distance along the optical axis o. By default, the direction from the first object-side surface S1 of the front fixed group L1 to the image-side surface of the last lens is the positive direction of the optical axis o. In Table 1, R represents the vertex radius of curvature of the surface. When this value is negative, it indicates that the center of curvature of the surface is on the left side of the surface; conversely, when this value is positive, it indicates that the center of curvature of the surface is on the right side of the surface. The units for D, H, and R in Table 1 are all mm.

[0062] Table 1 Basic parameters of each lens in Example 1

[0063] face shape R (mm) H (mm) D (mm) First object side surface S1 spherical 125.02 7.5 103 First image, side view, S2 spherical 207.1 21~57 100 Second side surface S3 aspherical -146.2 2.7 33 Second image, side view, S4 spherical 141.02 51~15.8 33 Third object side S5 spherical 113.3 2.7 40 Third image side view S6 Diffraction surface 200.2 63 38 Fourth side surface S7 spherical 67.1 5.4 58 Fourth image side view S8 aspherical 128.2 42 56

[0064] The formula for aspherical surfaces is as follows:

[0065]

[0066] The meanings of the quantities in the equation are as follows:

[0067] z is the lens dropout of the aspherical surface along the optical axis;

[0068] R is the vertex radius of curvature of the lens;

[0069] r is the half-aperture of the lens perpendicular to the optical axis;

[0070] k is the conic coefficient;

[0071] c = 1 / R;

[0072] α1, α2, α3, α4, α5, α6, α7, and α8 are all aspherical coefficients, of which α1, α7, and α8 are all 0.

[0073] Table 2 Aspheric coefficients of Example 1

[0074] <![CDATA[α2]]> <![CDATA[α3]]> <![CDATA[α4]]> <![CDATA[α5]]> <![CDATA[α6]]> First side surface S1 (spherical DLC film) 0 0 0 0 0 First image, side view S2 (spherical) 0 0 0 0 0 The second object's side surface S3 (non-spherical) 6.65444E-7 -6.44556E-10 1.72362E-12 2.07934E-15 -6.77809E-18 The second image is on the side, S4 (spherical). 0 0 0 0 0 The third object's side surface S5 (spherical) 0 0 0 0 0 The third image, side view S6 (diffraction plane) 3.77958E-5 6.91500E-7 -4.94516E-9 1.5394E-10 -5.57991E-13 The fourth object's side surface S7 (spherical) 0 0 0 0 0 The fourth image, side view S8 (aspherical). 1.77958E-5 2.91900E-7 -8.94516E-9 4.59294E-10 -5.52991E-13

[0075] Third image side diffraction plane (formula: The coefficients β are -9.52, 0.1 and -0.09, respectively.

[0076] As shown in Figures 3-5, its spot size (4~10μm) is superior to the Airy disk size (15μm), and it can achieve 0.3@40 line pairs in 80% of different fields of view, meaning that there is almost no room for improvement in resolution and sharpness. Furthermore, the 22.5mm-102mm long-wave infrared continuous zoom lens has strong temperature adaptability, capable of reaching -45℃ to 80℃ without changing image quality.

[0077] Figure 6-8 shows the spot image quality and MTF of a traditional 25-100mm long-wave continuous zoom lens. As can be seen from the figure, there is still a lot of room for improvement in resolution and sharpness.

[0078] As can be seen from the comparison above, the 22.5-102mm continuous zoom lens has a clear advantage in both MTF and spot image quality. Example 2

[0079] As shown in Figure 9, the 22.5mm-102mm long-wave infrared continuous zoom lens includes a front fixed group L1, a zoom group L2, a compensation group L3, and a focusing group L4 arranged sequentially along the optical axis o from the object side to the image side. Each of the front fixed group L1, zoom group L2, compensation group L3, and focusing group L4 has one lens. During imaging, light enters from the first object side S1 of the front fixed group L1, passes through the front fixed group L1, zoom group L2, compensation group L3, and focusing group L4 in sequence, and finally forms an image on the imaging plane L6 of the zoom lens 001. Among them, the front fixed group L1 has positive optical power, the zoom group L2 has negative optical power, and the compensation group L3 and focusing group L4 both have positive optical power. The first object-side surface S1 of the front fixed group L1 is convex near the optical axis o, and the first image-side surface S2 is concave near the optical axis o; the second object-side surface S3 of the zoom group L2 is concave near the optical axis o, and the second image-side surface S4 is concave near the optical axis o; the third object-side surface S5 of the compensation group L3 is convex near the optical axis o, and the third image-side surface S6 is concave near the optical axis o; the third object-side surface S7 of the focusing group L4 is convex near the optical axis o, and the fourth image-side surface S8 is concave near the optical axis o. All four optical groups are made of germanium single crystal, with the first object-side surface coated with a DLC film and the other surfaces coated with an AR film.

[0080] Specifically, taking zoom lens 001 with a zoom focal length of f = 22.5mm~102mm, aperture FNO = 1.2, field of view FOV = 24.6~6.2deg, light transmission band 8μm~12μm, center wavelength 10μm, and total optical length TTL = 196mm as an example, its ImgH is 5mm (half height), f12 is -44mm, f23 is -216mm, f34 is 61mm, CT3 is 2.7mm, CT4 is 5.4mm, SD11 is 103mm, CT1 is 7.5mm, SD21 is 33mm, CT2 is 2.7mm, BF is 42mm, ΔΦ1 is 0.03mm, ΔΦ2 is 0.02mm, ΔΦ3 is 0.02mm, and ΔΦ4 is 0.02mm. Other parameters of zoom lens 001 are given in Table 1 below. In this arrangement, the elements along the optical axis o of the zoom lens 001, from the object side to the image side, are arranged sequentially from top to bottom according to Table 1. In Table 1, D represents the diameter of the object side or image side of the corresponding surface number, and H represents the center distance from the current surface to the next surface, i.e., the distance along the optical axis o. By default, the direction from the first object side S1 of the front fixed group L1 to the image side of the last lens is the positive direction of the optical axis o. In Table 1, R represents the vertex radius of curvature of the surface. When this value is negative, it indicates that the center of curvature of the surface is on the left side of the surface; conversely, when this value is positive, it indicates that the center of curvature of the surface is on the right side of the surface. The units for D, H, and R in Table 3 are all mm.

[0081] Table 3 Basic parameters of each lens in Example 2

[0082] face shape R (mm) H (mm) D (mm) First object side surface S1 spherical 123.2 7.5 103 First image, side view, S2 spherical 202.1 21~57 100 Second side surface S3 aspherical -158.1 2.7 33 Second image, side view, S4 spherical 131.2 51~15.8 33 Third object side S5 spherical 113.2 2.7 40 Third image side view S6 Diffraction surface 199.1 63 38 Fourth side surface S7 spherical 67.3 5.4 58 Fourth image side view S8 aspherical 126.86 42 56

[0083] The formula for aspherical surfaces is as follows:

[0084]

[0085] The meanings of the quantities in the equation are as follows:

[0086] z is the lens dropout of the aspherical surface along the optical axis;

[0087] R is the vertex radius of curvature of the lens;

[0088] r is the half-aperture of the lens perpendicular to the optical axis;

[0089] k is the conic coefficient;

[0090] c = 1 / R;

[0091] α1, α2, α3, α4, α5, α6, α7, and α8 are all aspherical coefficients, of which α1, α7, and α8 are all 0.

[0092] Table 4 Aspheric coefficients in Example 2

[0093] a2 a3 a4 a5 a6 First object side surface S1 0 0 0 0 0 First image, side view, S2 0 0 0 0 0 Second side surface S3 7.65444E-7 -6.44524E-10 1.39362E-12 8.07634E-15 -6.77825E-18 Second image, side view, S4 0 0 0 0 0 Third object side S5 0 0 0 0 0 Third image side view S6 2.77958E-6 4.91500E-7 -7.94516E-9 7.5364E-10 -3.56751E-13 Fourth side surface S7 0 0 0 0 0 Fourth image side view S8 2.17958E-6 5.91300E-7 -6.94516E-9 6.55294E-10 -4.54591E-13

[0094] Third image side diffraction plane (formula: The coefficients β are -9.8, 0.14 and -0.071, respectively.

[0095] As shown in Figures 10-12, its spot size (4~10μm) is superior to the Airy disk size (15μm), and it can achieve 0.3@40 line pairs in 80% of different fields of view, meaning that there is almost no room for improvement in resolution and sharpness. As shown in Figure 13, the 22.5mm-102mm long-wave infrared continuous zoom lens has strong temperature adaptability, reaching -45℃ to 80℃ without changing image quality.

Claims

1. A 22.5mm-102mm long-wave infrared continuous zoom lens, characterized in that: The lens consists of four elements, including a front fixed group, a zoom group, a compensation group, and a focusing group arranged sequentially along the transmission direction of the incident beam; each of the front fixed group, zoom group, compensation group, and focusing group has one lens; along the transmission direction of the incident beam, the two sides of the front fixed group are the first object-side side and the first image-side side, the two sides of the zoom group are the second object-side side and the second image-side side, the two sides of the compensation group are the third object-side side and the third image-side side, and the two sides of the focusing group are the fourth object-side side and the fourth image-side side. The front fixed group is a meniscus lens with positive optical power, the first object side is convex and the first image side is concave; The zoom group is a meniscus lens with negative optical power, the second object side is concave, and the second image side is concave. The compensation group is a meniscus lens with positive optical power, the third object side is convex and the third image side is concave. The focusing group is a meniscus lens with positive optical power, the fourth object side is convex and the fourth image side is concave. The 22.5mm-102mm long-wave infrared continuous zoom lens satisfies the following relationship: 0.3 / mm<TTL / ImgH / f<1.8 / mm and 1.00<FNO<1.25; where TTL is the distance from the first object side to the image plane of the zoom lens on the optical axis, ImgH is half of the image height of the zoom lens, f is the effective focal length of the zoom lens, and FNO is the aperture number of the zoom lens; The following relationships are satisfied: 0.4 < |f12 / f| < 2 and 1.5 < |f23 / f| < 11; where f12 is the combined focal length of the fixed group and the zoom group, and f23 is the combined focal length of the zoom group and the compensation group. The center thickness of the front fixed group is 7.0~8.0mm; the center thickness of the zoom group is 2.0~3.0mm; the center thickness of the compensation group is 2.0~3.0mm; the center thickness of the focusing group is 5.0~6.0mm; at a focal length of 22.5mm, the center interval between the front fixed group and the zoom group is 21±2mm, and the center interval between the zoom group and the compensation group is 51±2mm; at a focal length of 102mm, the center interval between the front fixed group and the zoom group is 57±2mm, the center interval between the zoom group and the compensation group is 15.8±2mm; and the center interval between the compensation group and the focusing group is 63±2mm.

2. The 22.5mm-102mm long-wave infrared continuous zoom lens according to claim 1, characterized in that, The materials used in the front fixed group, zoom group, compensation group and focusing group are all germanium. The first side is coated with DLC film, and the other sides are coated with AR film.

3. The 22.5mm-102mm long-wave infrared continuous zoom lens according to claim 1 or 2, characterized in that, The following relationship must be satisfied: 0.1 < CT4 / BF < 0.3; where CT4 is the center thickness of the focusing group on the optical axis, and BF is the minimum distance on the optical axis from the image side of the focusing group to the image plane of the zoom lens.

4. The 22.5mm-102mm long-wave infrared continuous zoom lens according to claim 1 or 2, characterized in that, The following relationships are satisfied: 10 < SD11 / CT1 < 16; 11 < SD21 / CT2 < 15; where SD11 is the maximum effective half-aperture of the first object side, SD21 is the maximum effective half-aperture of the second object side, CT1 is the center thickness of the front fixed group on the optical axis, and CT2 is the center thickness of the zoom group on the optical axis.

5. The 22.5mm-102mm long-wave infrared continuous zoom lens according to claim 1 or 2, characterized in that, The following relationship must be satisfied: 1 < CT4 / ImgH < 1.5; where CT4 is the center thickness of the focusing group on the optical axis, and ImgH is half the image height of the zoom lens.

6. The 22.5mm-102mm long-wave infrared continuous zoom lens according to claim 1 or 2, characterized in that, The first object side and the first image side are spherical; the second object side is aspherical, and the second image side is spherical; the third object side is spherical, and the third image side is a diffraction surface; the fourth object side is spherical, and the fourth image side is aspherical.

7. The 22.5mm-102mm long-wave infrared continuous zoom lens according to claim 1 or 2, characterized in that, The radius of curvature of the first object side is 110~150mm, and the radius of curvature of the first image side is 200~250mm; the radius of curvature of the second object side is -160~-130mm, and the radius of curvature of the second image side is 110~175mm; the radius of curvature of the third object side is 90~125mm, and the radius of curvature of the third image side is 150~220mm; the radius of curvature of the fourth object side is 50~100mm, and the radius of curvature of the fourth image side is 100~160mm.

8. The 22.5mm-102mm long-wave infrared continuous zoom lens according to claim 1 or 2, characterized in that, Assembly tolerances satisfy the following relationships: -0.03≦△L1+△L2+△L3≦0.03; 0.01≦∣ΔΦ1∣≦0.04; 0.01≦∣ΔΦ2∣≦0.03; 0.01≦∣ΔΦ3∣≦0.03; 0.01≦∣ΔΦ4∣≦0.03; where △L1 is the distance tolerance between the side edge of the first image and the side edge of the second image; △L2 is the distance tolerance between the side edge of the second image and the side edge of the third image; △L3 is the distance tolerance between the side edge of the third image and the side edge of the fourth image; ΔΦ1 is the diameter tolerance of the front fixed group; ΔΦ2 is the diameter tolerance of the variable magnification group; ΔΦ3 is the diameter tolerance of the compensation group; and ΔΦ4 is the diameter tolerance of the focusing group.

Images