A large-aperture, lightweight long-wave infrared continuous zoom lens

Abstract

This utility model discloses a large-aperture lightweight long-wave infrared continuous zoom lens, comprising a front fixed group, a compensation group, a rear fixed group, and a long-wave uncooled detector arranged sequentially along the optical axis from the object plane to the image plane. The front fixed group is a meniscus lens with positive optical power and a convex surface facing the object plane, with both sides being spherical. The zoom group is a plano-concave lens with negative optical power, with a planar front surface and an aspherical rear surface. The compensation group is a plano-concave lens with negative optical power, with an aspherical front surface and a planar rear surface. The rear fixed group has an aspherical front surface and a planar rear surface. This structure uses a zoom form where both the zoom group and the compensation group have negative optical power, achieving a large-aperture lightweight design while ensuring optical imaging capabilities. It uses only four even-order aspherical surfaces, does not use binary diffraction surfaces, and incorporates two planar surfaces in its design. This effectively reduces the system's tolerance sensitivity while ensuring good manufacturability and lens lightweight design.

Description

Technical Field

[0001] This utility model relates to a zoom lens, and more particularly to a large-aperture, lightweight, long-wave infrared continuous zoom lens. Background Technology

[0002] With the rapid development of infrared detection technology, infrared thermal imaging detection technology is now widely used in various military fields such as target identification, weapon guidance, and laser destruction, as well as in various civilian fields such as security monitoring, surveillance and reconnaissance, and temperature measurement. In the civilian sector, uncooled infrared detectors are widely used due to their advantages of rapid start-up, low cost, and low price. Consequently, infrared lenses compatible with uncooled infrared detectors are also widely used. Currently, uncooled infrared detectors operate only in the long-wave infrared band. Therefore, long-wave infrared optical lenses are the mainstream optical components in the civilian field, with long-wave infrared zoom lenses having a particularly high demand. As the size of infrared array elements continues to increase, the design of long-wave infrared zoom lenses faces greater challenges. Furthermore, with continuous technological innovation in the civilian field, new requirements have been placed on lens aperture and weight. Currently, long-wave infrared zoom lenses are mainly compatible with low-resolution, small-sized cooled infrared detectors. Therefore, how to increase the optical aperture of the lens while improving resolution and pixel size and reducing product weight has become a key technical challenge. Utility Model Content

[0003] This invention provides a large-aperture, lightweight, long-wave infrared continuous zoom lens to overcome the shortcomings of existing long-wave infrared zoom lenses in terms of improving the optical aperture.

[0004] To solve the above-mentioned technical problems, this utility model provides the following technical solution:

[0005] This utility model discloses a large-aperture lightweight long-wave infrared continuous zoom lens, comprising a front fixed group, a zoom group, a compensation group, a rear fixed group and a long-wave uncooled detector arranged sequentially from the object side to the image plane along the optical axis. The front fixed group is a meniscus lens with positive optical power and convex surface facing the object side, the zoom group is a plano-concave lens with negative optical power, and the compensation group is a plano-concave lens with negative optical power.

[0006] The positions of the zoom group and the compensation group are adjustable along the optical axis.

[0007] Both sides of the front fixing assembly are spherical.

[0008] The front surface of the zoom unit is a plane, and the rear surface is an aspherical surface;

[0009] The front surface of the compensation group is aspherical, and the rear surface is planar.

[0010] Furthermore, the rear fixing group includes a first biconvex lens with positive optical power and a second biconvex lens with positive optical power, which are sequentially distributed along the optical axis. Both sides of the first biconcave lens are aspherical surfaces; the object-side of the second biconvex lens is aspherical, and the image-side is spherical.

[0011] Furthermore, the zoom lens has an effective focal length of 20–100 mm, an F-number of 1 at the short focal length end, an F-number of 1 at the long focal length end, a total optical system length of 177 mm, a resolution of 640*512 pixels for the long-wavelength uncooled detector, a pixel size of 17 μm, and an effective field of view of 28.55°×23.52°–6.21°×4.97°.

[0012] Furthermore, the lens materials of the front fixation group, the zoom group, the compensation group, and the rear fixation group are all germanium.

[0013] Furthermore, during the zoom process, both the zoom group and the compensation group move monotonically along the optical axis, while the positions of the front fixed group and the rear fixed group on the optical axis remain unchanged.

[0014] Furthermore, the total travel distance of the zoom unit is 57.30 mm.

[0015] Furthermore, the total travel distance of the compensation group is 20.4 mm.

[0016] The beneficial effects achieved by this utility model are as follows: This structure uses a zoom form where both the zoom group and the compensation group are negative optical power. While ensuring optical imaging capabilities, it can achieve a large-aperture lightweight design. It uses only 4 even-order aspherical surfaces and does not use binary diffraction surfaces. It also uses two planes in the design, which can effectively reduce the tolerance sensitivity of the system while ensuring good manufacturing process and lightweight lenses.

[0017] In terms of material selection, all-germanium materials are used, and the diameter and thickness are optimized to effectively achieve lightweight lens design.

[0018] It can achieve 5x continuous zoom of the optical system focal length from 100mm to 20mm, and has good optical system imaging quality throughout the entire zoom range, without the need for manual operation during zooming. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the present invention and form part of the specification. They are used together with the embodiments of the present invention to explain the present invention, but do not constitute a limitation thereof. In the drawings:

[0020] Figure 1 This is a diagram of the optical system of the large-aperture lightweight long-wave infrared continuous zoom lens of this utility model at a focal length of 100mm.

[0021] Figure 2 This is a diagram of the optical system of the large-aperture lightweight long-wave infrared continuous zoom lens of this utility model at a focal length of 60mm.

[0022] Figure 3 This is a diagram of the optical system of the large-aperture lightweight long-wave infrared continuous zoom lens of this utility model at a focal length of 20mm.

[0023] Figure 4 This is the MTF curve of this utility model at a focal length of 100mm and a spatial frequency of 30lp / mm;

[0024] Figure 5 This is the MTF curve of this utility model at a focal length of 60mm and a spatial frequency of 30lp / mm;

[0025] Figure 6 This is the MTF curve of the present invention at a focal length of 20mm and a spatial frequency of 30lp / mm.

[0026] In the diagram: A, front fixed group; B, zoom group; C, compensation group; D, rear fixed group; D-1, first biconvex lens; D-2, second biconvex lens; E, image plane. Detailed Implementation

[0027] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0028] Example 1

[0029] like Figures 1-3 As shown, a large-aperture lightweight long-wave infrared continuous zoom lens includes a front fixed group A, a zoom group B, a compensation group C, a rear fixed group D, and a long-wave uncooled detector, which are arranged sequentially along the optical axis from the object plane to the image plane E. The front fixed group A is a meniscus lens with positive optical power and convex surface facing the object plane. The zoom group B is a plano-concave lens with negative optical power. The compensation group C is a plano-concave lens with negative optical power. The rear fixed group D includes a first biconvex lens D-1 with positive optical power and a second biconvex lens D-2 with positive optical power, which are arranged sequentially along the optical axis.

[0030] The large-aperture, lightweight long-wave infrared continuous zoom lens has an effective focal length of 20–100 mm, an F-number of 1.0 at both the short and long focal lengths, a total optical system length of 177 mm, a compatible detector resolution of 640*512 pixels, a pixel size of 17 μm, and an effective field of view of 28.55°×23.52°–6.21°×4.97°.

[0031] The optical aperture is 100mm at the telephoto end and 20mm at the short focal length end.

[0032] The zoom group B and the compensation group C move monotonically along the optical axis. During zooming, the zoom group B moves monotonically along the optical axis, the compensation group C moves monotonically along the optical axis, and the positions of the front fixed group A and the rear fixed group D on the optical axis remain unchanged during zooming.

[0033] The lens material of the front fixation group A, the zoom group B, the compensation group C, the rear fixation group D-1, and the rear fixation group D-2 is germanium.

[0034] The large-aperture lightweight long-wave infrared continuous zoom lens has aspherical surfaces for the rear surface of the zoom group B, the front surface of the compensation group C, the rear surface of the first biconvex lens D-1, and the front surface of the second biconvex lens D-2.

[0035] The back surface of the variable magnification group B is an even-order aspherical surface, and its surface shape equation is as follows:

[0036]

[0037] Where c = 1 / r, r = 196.34 mm, K = 0, a1 = 0, a2 = -2.4738 × 10⁻⁷, a3 = -9.3672 × 10⁻¹⁰, a4 = 2.1130 × 10⁻¹².

[0038] The front surface of the compensation group C is an even-order aspherical surface, and its surface shape equation is as follows:

[0039]

[0040] Where c = 1 / r, r = -105.38 mm, K = 0, a1 = 0, a2 = -4.644 × 10⁻⁶, a3 = 3.8892 × 10⁻⁹, a4 = -8.0976 × 10⁻¹²,

[0041] a5 = 1.3332 × 10⁻¹⁵.

[0042] The rear surface of the first biconvex lens D-1 is an even-order aspherical surface, and its surface shape equation is as follows:

[0043]

[0044] Where c = 1 / r, r = -116.88 mm, K = 0, a1 = 0, a2 = -4.9836 × 10⁻⁶, a3 = 4.8873 × 10⁻⁹, a4 = -9.0965 × 10⁻¹².

[0045] The front surface of the second biconvex lens D-2 is an even-order aspherical surface, and its surface shape equation is as follows:

[0046]

[0047] Where c = 1 / r, r = 365.778 mm, K = 0, a1 = 0, a2 = 4.8876 × 10⁻⁸, a3 = 8.3422 × 10⁻¹⁰, a4 = 5.4663 × 10⁻¹², a5 = -2.1165 × 10⁻¹⁵.

[0048] The large-aperture lightweight long-wave infrared continuous zoom lens has a focal length range of 20mm to 100mm. The distance between the rear surface of the front fixed group A and the front surface of the zoom group B is Z1, the distance between the rear surface of the zoom group B and the front surface of the compensation group C is Z2, and the distance between the rear surface of the compensation group C and the front surface of the first biconvex lens D-1 is Z3. When the focal length of the long-wave infrared lens changes unidirectionally within the range of 20mm to 100mm, Z1 increases from 14.70mm to 72.00mm, Z2 decreases from 41.70mm to 5.00mm, and Z3 decreases from 32.10mm to 11.50mm. The distance between the rear surface of the first biconvex lens D-1 and the front surface of the second biconvex lens D-2 is 38mm, and the distance between the rear surface of the second biconvex lens D-2 and the detector remains at 24.20mm.

[0049] The distance between the center vertex of the front surface of the front fixed group A and the image plane is controlled to be 177.00 mm in full zoom mode.

[0050] The surfaces of each lens group are marked along the optical axis from the object side to the image side: the front and rear surfaces of the fixed group A are S1 and S2, the front and rear surfaces of the zoom group B are S3 and S4, the front and rear surfaces of the compensation group C are S5 and S6, the front and rear surfaces of the first biconvex lens D-1 are S7 and S8, and the front and rear surfaces of the second biconvex lens D-2 are S9 and S10. During zooming, the distance between the rear surface of the fixed group A and the front surface of the zoom group B is Z1, the distance between the rear surface of the zoom group B and the front surface of the compensation group C is Z2, and the distance between the rear surface of the compensation group C and the front surface of the first biconvex lens D-1 is Z3. The optical structural parameters of this invention at focal lengths of 100mm, 60mm, and 20mm are shown in Table 1.

[0051] Table 1

[0052]

[0053] As shown in Table 1, this invention focuses on lightweight design and optimizes lens thickness. 10mm, 3.8mm, 4.2mm, 4.35mm, and 4.2mm correspond sequentially to the center thicknesses of the front fixed group A, zoom group B, compensation group C, first biconvex lens D-1, and second biconvex lens D-2, respectively. The center thickness of the lenses remains constant during continuous zooming. The distance between the rear surface of the front fixed group A and the front surface of the zoom group B is Z1, the distance between the rear surface of the zoom group B and the front surface of the compensation group C is Z2, and the distance between the rear surface of the compensation group C and the front surface of the first biconvex lens D-1 is Z3, which continuously changes during continuous zooming. The air gap between the rear surface of the first biconvex lens D-1 and the front surface of the second biconvex lens D-2 is 38mm, and the distance between the rear surface of the second biconvex lens D-2 and the image plane is 24.20mm. Both of these parameters remain constant during zooming.

[0054] The values ​​of Z1, Z2, and Z3 at different focal lengths during continuous zoom are shown in Table 2.

[0055] Table 2

[0056]

[0057]

[0058] During continuous zoom, as the system focal length gradually changes from 100mm to 20mm, Z1 will undergo a monotonous linear change, gradually decreasing from 72.00mm to 14.70mm; Z2 will undergo a monotonous linear change, gradually increasing from 5.00mm to 41.70mm; and Z3 will undergo a monotonous linear change, increasing from 11.50mm to 32.10mm.

[0059] like Figures 4-6 The figures show the optical transfer function (MTF) curves of this invention at a spatial frequency of 30 lp / mm for focal lengths of telephoto (100mm), medium telephoto (60mm), and short telephoto (20mm). The horizontal axis represents the number of line pairs per millimeter, and the vertical axis represents the normalized contrast. As can be seen from the figures, the modulation transfer function values ​​of this invention are high at different focal lengths, indicating that it can achieve clear imaging of the target throughout the continuous zoom process.

[0060] It should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The terminology used in the description of this application is only for describing specific embodiments and is not intended to limit the exemplary embodiments according to this application. For ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings indicate similar items, and therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0061] It should be noted that the terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and not to describe a specific order or sequence. It should be understood that such use of data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0062] It should be noted that in the description of this application, the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

Claims

1. A lightweight long-wave infrared continuous zoom lens with a large aperture, characterized by, It includes a front fixed group, a zoom group, a compensation group, a rear fixed group, and a long-wavelength uncooled detector, which are arranged sequentially along the optical axis from the object plane to the image plane. The front fixed group is a meniscus lens with positive optical power and convex surface facing the object plane. The zoom group is a plano-concave lens with negative optical power. The compensation group is a plano-concave lens with negative optical power. The positions of the zoom group and the compensation group are adjustable along the optical axis. Both sides of the front fixing assembly are spherical. The front surface of the zoom unit is a plane, and the rear surface is an aspherical surface; The front surface of the compensation group is aspherical, and the rear surface is planar.

2. The lightweight long wave infrared continuous zoom lens of claim 1, wherein, The rear fixing group includes a first biconvex lens with positive optical power and a second biconvex lens with positive optical power, which are sequentially distributed along the optical axis. Both sides of the first biconcave lens are aspherical surfaces; the object-side of the second biconvex lens is aspherical, and the image-side is spherical.

3. The lightweight long wave infrared continuous zoom lens of claim 1, wherein, The long-wavelength uncooled detector has a resolution of 640*512 pixels, a pixel size of 17μm, an effective field of view of 28.55°×23.52°~6.21°×4.97°, an effective focal length of 20~100mm for the zoom lens, an F-number of 1 at both the short and long focal lengths, and a total optical system length of 177mm.

4. The large-aperture lightweight long-wave infrared continuous zoom lens according to claim 1, characterized in that, The lenses of the front fixation group, zoom group, compensation group, and rear fixation group are all made of germanium.

5. The lightweight long wave infrared continuous zoom lens of claim 1, wherein, During zooming, both the zoom group and the compensation group move monotonically along the optical axis, while the positions of the front fixed group and the rear fixed group on the optical axis remain unchanged.

6. The lightweight long wave infrared continuous zoom lens of claim 5, wherein, The total travel distance of the zoom unit is 57.30 mm.

7. The lightweight long wave infrared continuous zoom lens of claim 5, wherein, The total travel distance of the compensation group is 20.4 mm.

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