Infrared continuous zoom system

Abstract

The present invention discloses an infrared continuous zoom system, comprising a first lens, a second lens, an aperture, a third lens, a fourth lens, and an image plane, arranged sequentially from the object side to the image side. The second and third lenses are movable along the optical axis to achieve zooming. The aperture of the aperture is fixed and does not change with changes in focal length, eliminating the need for additional structural components to change the aperture. During zooming, the second lens acts as a variable magnification group, and its movement causes focal length changes, simultaneously shifting the image plane and resulting in blurred images. The third lens acts as a compensation group, performing nonlinear motion to compensate for image plane displacement, thereby maintaining a clear image throughout the zooming process. The lens is small in size, low in cost, and compact in structure, making it suitable for applications requiring high weight and volume. The aperture of the aperture does not change with changes in focal length, reducing the number of structural components required to adjust the aperture and maintaining consistent resolution from short to long focal lengths.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, in particular to an infrared continuous zoom system. Background Art

[0002] Long-wave infrared uncooled lenses hold great promise for development in both civilian and military applications due to their all-weather suitability in harsh environments, low cost, low power consumption, and compact size. In many applications, traditional fixed-focus lenses are limited in their ability to track and observe targets in varying fields of view, necessitating the use of zoom lenses. Current infrared zoom lenses on the market often use five or more elements, resulting in multiple lens elements with aberration correction, difficult assembly, and large system sizes. Furthermore, the aperture changes with focal length, often requiring additional structure to adjust the aperture, which limits assembly, cost, and installation size. Summary of the Invention

[0003] The main purpose of the present invention is to propose an infrared continuous zoom system, which involves a small number of lenses, has low cost, and is convenient for small-volume design. At the same time, it adopts a fixed aperture design to reduce the number of structural parts for adjusting the aperture and can maintain the consistency of resolution from short focus to long focus.

[0004] To achieve the above-mentioned objectives, the present invention proposes an infrared continuous zoom system, comprising a first lens, a second lens, an aperture, a third lens, a fourth lens and an image plane arranged in sequence from the object side to the image side, wherein the second lens and the third lens can move along the optical axis to achieve continuous zoom, and the aperture of the aperture is fixed.

[0005] Optionally, the total optical length TTL of the infrared continuous zoom system is ≤70 mm.

[0006] Optionally, the F number of the infrared continuous zoom system is set to F≤1.

[0007] Optionally, the first lens is a meniscus lens with positive optical power, with its concave surface facing the image plane;

[0008] The second lens is a biconcave lens with negative optical power;

[0009] The third lens is a meniscus lens with positive optical power, with its concave surface facing the image plane;

[0010] The fourth lens is a meniscus lens with positive refractive power, with a concave surface facing the image plane.

[0011] Optionally, the first lens, the second lens, and the fourth lens are all made of germanium glass, and the third lens is made of chalcogenide IRG206 glass.

[0012] Optionally, a distance between the first lens and the second lens is L1, where 5.9 mm ≤ L1 ≤ 16.02 mm.

[0013] Optionally, a distance between the third lens and the fourth lens is L3, wherein 15.93 mm ≤ L3 ≤ 21.34 mm.

[0014] Optionally, the third lens can be moved back and forth along the optical axis alone to achieve clear imaging within the full focal range of -40°C to 80°C.

[0015] The technical solution of the present invention utilizes four functional lenses, two of which are fixed at the edges and two in the middle as movable lenses, to achieve a continuous zoom range of 10-35mm. A diaphragm is provided between the second and third lenses, and its aperture is fixed and does not change with focal length, eliminating the need for additional structural components to alter the aperture. During zooming, the second lens acts as a variable magnification group, and its movement causes focal length changes, shifting the image plane and resulting in blurred images. The third lens, acting as a compensation group, then performs nonlinear motion to compensate for image displacement, ensuring a consistently clear image throughout the zoom process. This lens is small, low-cost, and compact, making it suitable for applications requiring high weight and volume. The diaphragm aperture is fixed and does not change with focal length, reducing the number of components required to adjust the aperture while maintaining consistent resolution from short to long focus. Image deformation is minimal, and distortion is minimal at short focus. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0017] Figure 1 A schematic diagram of an embodiment of the infrared continuous zoom system provided by the present invention (mid-focus state);

[0018] Figure 2 for Figure 1 Schematic diagram of the mid-infrared continuous zoom system (short focus state);

[0019] Figure 3 for Figure 1 Short-focus MTF curve of the mid-infrared continuous zoom system;

[0020] Figure 4 for Figure 1 Mid-focus MTF curve of the mid-infrared continuous zoom system;

[0021] Figure 5 for Figure 1 Long-focus MTF curve of the mid-infrared continuous zoom system;

[0022] Figure 6 for Figure 1 Short-focus distortion curve of the mid-infrared continuous zoom system;

[0023] Figure 7 for Figure 1 Telephoto distortion curve of the mid-infrared continuous zoom system.

[0024] Description of Figure Numbers:

[0025] Label name Label name 100 Infrared continuous zoom system 4 The third lens 1 First lens 5 Fourth lens 2 Second lens 6 Protective glass 3 aperture

[0026] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0027] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0028] It should be noted that if a directional indication is involved in an embodiment of the present invention, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0029] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0030] Long-wave infrared uncooled lenses hold great promise for development in both civilian and military applications due to their all-weather performance in harsh environments, low cost, low power consumption, and compact size. In many applications, traditional fixed-focus lenses are limited in tracking and observing targets in varying fields of view, necessitating the use of zoom lenses. Currently, most infrared zoom lenses on the market utilize zinc selenide crystals and multiple lens elements for aberration correction, which poses limitations in assembly, cost, and installation size. Furthermore, their high F-numbers result in low light transmission, which compromises lens resolution.

[0031] Therefore, the prior art has the following defects:

[0032] 1. The same type of infrared continuous zoom system has many lenses, usually 5 or more, which makes installation and adjustment difficult and the system size large.

[0033] 2. The same type of infrared continuous zoom system has a small aperture and a large F number, which will reduce the image signal-to-noise ratio, increase the pixel size, and reduce the resolution, affecting the imaging effect.

[0034] In view of this, the present invention provides an infrared continuous zoom system. Figures 1 to 2 The embodiment of the infrared continuous zoom system provided by the present invention is: Figures 3 to 7 The corresponding curve data graph is shown in FIG.

[0035] Please refer to Figures 1 to 2 The infrared continuous zoom system 100 includes a first lens 1, a second lens 2, an aperture 3, a third lens 4, a fourth lens 5 and an image plane, which are arranged in sequence from the object side to the image side. The second lens 2 and the third lens 4 can move along the optical axis to achieve continuous zoom, and the aperture of the aperture 3 is fixed.

[0036] The technical solution of the present invention utilizes four functional lenses: two fixed lenses at the edges and two movable lenses in the middle, achieving a continuous zoom range of 10 to 35 mm. A diaphragm 3 is positioned between the second lens 2 and the third lens 4. The aperture of diaphragm 3 is fixed and does not change with focal length, eliminating the need for additional structural components to adjust the aperture. During zooming, the second lens 2 acts as a variable magnification group, and its movement causes focal length changes, simultaneously shifting the image plane and causing image blur. The third lens 4, acting as a compensating group, then performs nonlinear motion to compensate for the image plane shift, ensuring a consistently clear image throughout the zoom process. This lens is compact, low-cost, and well-designed for applications requiring high weight and volume. The aperture of diaphragm 3 is fixed and does not change with focal length, reducing the number of structural components required to adjust the aperture while maintaining consistent resolution from short to long focal lengths. Image distortion is minimal, and distortion is minimal at short focal lengths.

[0037] Specifically, the infrared continuous zoom system 100 has a total optical length (TTL) of 70 mm or less, and an F-number of F ≤ 1. This large aperture design, compared to other products with an F-number of 1.1 to 1.2, allows for greater light transmission, captures more target information, and effectively improves the signal-to-noise ratio of the lens.

[0038] At the same time, in this embodiment, a high-resolution target surface with a resolution of 384*288 pixels and a size of 12um is used, and high-definition imaging is performed at a spatial resolution of 42lp / mm, which has high resolution and greater target detection accuracy.

[0039] Please refer again Figure 1 In this embodiment, the aperture 3 is arranged on the side of the third lens 4 facing the object, close to the surface of the third lens 4. The aperture of the aperture 3 will not change, but the aperture 3 can be set to move together with the third lens 4. In other embodiments, the position of the aperture 3 can also be set to remain fixed, and its setting position should not affect the movement of the second lens 2 and the third lens 4.

[0040] Furthermore, in this embodiment, the first lens 1 is a meniscus lens with positive optical power, whose concave surface faces the image plane; the second lens 2 is a biconcave lens with negative optical power; the third lens 4 is a meniscus lens with positive optical power, whose concave surface faces the image plane; and the fourth lens 5 is a meniscus lens with positive optical power, whose concave surface faces the image plane.

[0041] It should be understood that in other embodiments, the selection of each lens may vary, and the distance design between two adjacent lenses will be changed accordingly, which will not be elaborated in detail in the present invention.

[0042] Furthermore, the first lens 1, the second lens 2, and the fourth lens 5 are all made of germanium glass, and the third lens 4 is made of chalcogenide IRG206 glass. Based on design requirements and desired effects, chalcogenide glass was chosen for the third lens 4, which offers superior image correction compared to conventional zinc selenide crystals.

[0043] To properly control the zoom range and image clarity, in one embodiment, the distance between the first lens 1 and the second lens 2 is L1, where 5.9mm≤L1≤16.02mm. The first lens 1 is fixed in position, and the distance between the second lens 2 and the first lens 1 remains between 5.9mm and 16.02mm during the zoom range from short to medium to long focal lengths.

[0044] In another embodiment, the distance between the third lens 4 and the fourth lens 5 is L3, where 15.93 mm ≤ L3 ≤ 21.34 mm. The fourth lens 5 is fixed in position, and the distance between the third lens 4 and the fourth lens 5 is maintained between 15.93 mm and 21.34 mm during the process of cooperating to achieve short focal length, medium focal length, and long focal length.

[0045] In this embodiment, the size requirements of 5.9 mm ≤ L1 ≤ 16 mm and 15.9 ≤ L2 ≤ 21.3 mm are met at the same time, that is, the distance between the movable second lens 2 and the third lens 4 is ultimately 3.1 mm ≤ L2 ≤ 16.3 mm.

[0046] by Figure 2 Taking the embodiment of as an example, the basic parameters of each lens are shown in Table 1, where the units of curvature radius and thickness are all millimeters (mm).

[0047] Table 1

[0048]

[0049] For example, in the telephoto state, the corresponding distance between the first lens 1 and the second lens 2 is 15.99 mm, the distance between the second lens 2 and the third lens 4 is 3.54 mm, and the distance between the third lens 4 and the fourth lens 5 is 20.58 mm; in the short focus state, the corresponding distance between the first lens 1 and the second lens 2 is 5.91 mm, the distance between the second lens 2 and the third lens 4 is 15.24 mm, and the distance between the third lens 4 and the fourth lens 5 is 18.96.

[0050] In this embodiment, the sum of the intervals is 40.11 mm, and together with other fixed values, the total length is 70 mm.

[0051] The aspheric and diffractive surface coefficients of each surface are shown in Table 2.

[0052] Table 2

[0053] Surface serial number E4 E6 E8 E10 E12 S1 9.2049e-008 -2.4737e-010 0 0 0 S2 0 0 0 0 0 S3 6.293e-005 -2.5881e-008 -4.9123e-010 0 0 S4 4.2273e-005 7.8324e-008 -8.4007e-010 0 0 S5 -7.7003e-006 6.8327e-007 -7.1132e-009 2.6722e-011 0 S6 6.0231e-006 9.1359e-007 -1.0897e-008 5.1301e-011 -4.7672e-014 S7 -1.927e-006 -7.083e-008 -8.7303e-010 0 0 S8 7.4069e-006 -4.5855e-007 6.7285e-010 0 0

[0054] The S6 surface is a diffraction surface based on an aspherical surface, and the diffraction surface coefficients are A2 = -26.4957, A4 = 4.1075, and A6 = -1.318.

[0055] In addition, a protective glass 6 is provided between the fourth lens 5 and the image plane. The object side light passes through the first lens 1, the second lens 2, the aperture 3, the third lens 4, the fourth lens 5 and the protective glass 6 in sequence to obtain a clear image on the image plane.

[0056] At the same time, in the present application, the third lens 4 can be moved back and forth along the optical axis alone to achieve clear imaging within the full focal length range of -40°C to 80°C.

[0057] Compared with the prior art, the technical solution of the present invention has the following advantages: the lens is small in size, and continuous zoom of 10-35mm is achieved through the movement of the second lens 2 and the third lens 4. The total length of the lens is 70mm, and the structure is compact, which is very suitable for occasions with high weight and volume requirements; it adopts a high-resolution target surface with a resolution of 384*288 pixels and a size of 12um, and achieves high-definition imaging at a spatial resolution of 42lp / mm, with high resolution and greater target detection accuracy; it has a large aperture, F / #≤1.0, compared with other products with F / #=1.1~1.2, the amount of light passing through is greater, more target information is obtained, and the signal-to-noise ratio of the lens is effectively improved; the distortion is small, the image deformation is small, the short-focus distortion is <5%; the long-focus distortion is <2%; clear imaging is achieved at -40℃~80℃.

[0058] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An infrared continuous zoom system, characterized in that: The optical system comprises a first lens, a second lens, an aperture, a third lens, a fourth lens, and an image plane, which are arranged in sequence from the object side to the image side, wherein the second lens and the third lens can move along the optical axis to achieve continuous zooming, and the aperture of the aperture is fixed; The total optical length TTL of the infrared continuous zoom system is ≤70 mm, and the F number of the infrared continuous zoom system is set to F≤1.

2. The infrared continuous zoom system according to claim 1, wherein: The first lens is a meniscus lens with positive optical power, with its concave surface facing the image plane; The second lens is a biconcave lens with negative optical power; The third lens is a meniscus lens with positive optical power, with its concave surface facing the image plane; The fourth lens is a meniscus lens with positive refractive power, with a concave surface facing the image plane.

3. The infrared continuous zoom system according to claim 1, wherein: The first lens, the second lens, and the fourth lens are all made of germanium glass, and the third lens is made of chalcogenide IRG206 glass.

4. The infrared continuous zoom system according to claim 1, wherein: The distance between the first lens and the second lens is L1, where 5.9 mm≤L1≤16.02 mm.

5. The infrared continuous zoom system according to claim 1, wherein: The distance between the third lens and the fourth lens is L3, wherein, 15.93mm≤L3≤21.34mm.

6. The infrared continuous zoom system according to claim 1, wherein: The third lens can be moved back and forth along the optical axis to achieve clear imaging within the full focal length range of -40°C to 80°C.

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