Large-aperture middle-wave infrared continuous zoom optical system capable of electromagnetic shielding

Abstract

The application provides a large-aperture middle-wave infrared continuous zoom optical system capable of realizing electromagnetic shielding, comprising a first front lens, a second front lens, a zoom lens, a compensation lens, a focusing lens, a first relay lens, a second relay lens and a third relay lens arranged in sequence along the optical axis direction from the object side to the image side; the first and second front lenses are meniscus positive lenses with convex surfaces facing the object side, the zoom lens is a double-concave silicon negative lens, the compensation lens is a double-convex silicon positive lens, and the first, second and third relay lenses are a double-convex silicon positive lens, a double-concave germanium negative lens and a double-convex silicon positive lens in sequence. The secondary imaging configuration designed by the application improves the optical axis consistency precision in the full field of view during optical mechanical adjustment, and realizes clear imaging of an infrared dim small target with a large optical aperture. The outer side of the light transmission area of each optical element extends outward with a modified extension structure, a metal electrode is plated on the surface, and an antireflection film is plated on the light transmission area, so that the imaging system is suitable for a strong electromagnetic environment.

Description

Technical Field

[0001] This invention belongs to the field of infrared continuous zoom optical imaging technology, specifically relating to a large-aperture mid-wave infrared continuous zoom optical system that can achieve electromagnetic shielding. Background Technology

[0002] Currently, to protect one's own infrared optoelectronic system, microwave electromagnetic shielding is mainly addressed from two levels: mechanical structure and imaging mechanism. On the one hand, electromagnetic interference (EMI) protection is designed for the circuitry within the imaging mechanism; on the other hand, the entire system is mechanically sealed. These two methods can shield the system from low-power EMI to a certain extent. However, neither method completely eliminates the gap between the optical frame and the lens, leaving insufficient protection against high-power electromagnetic environments. While electromagnetic shielding sealing strips can be used to fill the gap between the optical frame and the lens, in structures with narrow edge contours, such as biconvex optical lenses, adding sealing strips can easily cause optical axis tilting, resulting in poor imaging. If gap elimination is neglected, the electromagnetic shielding effect will be compromised. Currently, there are few reports in the industry of solutions to this technical problem.

[0003] In photoelectric detection and identification, large-aperture mid-wave infrared continuous zoom observation and aiming systems, with their advantages of high detection resolution, high sensitivity, large field of view search, and small field of view stabilization, have become an effective means of detecting "low, slow, and small" infrared targets. However, existing technologies still have certain limitations. For example, Chinese patent CN110703422B discloses a 50x continuous zoom mid-wave infrared optical system with an ultra-large zoom ratio. Although it achieves 50x ultra-large continuous zoom, its entrance pupil diameter is relatively small, limiting its ability to receive incident radiation energy and making it unfavorable for photoelectric detection of infrared targets. Another example is the Chinese paper "Design of a Large-Area Continuous Zoom Area Scanning Infrared Optical System," which discloses an optical system with a large optical aperture, but its zoom ratio is only 10x, limiting the system's search range and detail acquisition capabilities, making it unfavorable for identifying and indicating infrared targets. Furthermore, most mid-wave infrared continuous zoom optical systems, including the aforementioned patents, have not been specifically designed for high-power electromagnetic conditions, making them difficult to adapt to application requirements in complex electromagnetic environments.

[0004] In summary, infrared optical systems require excellent optomechanical electromagnetic shielding performance to ensure stable operation even in strong electromagnetic environments. Therefore, developing a mid-wave infrared continuous zoom optical system that combines large aperture, high zoom ratio, and adaptability to strong electromagnetic environments is a key technological direction for improving the effectiveness against unmanned aerial vehicles (UAVs) and is of great significance for promoting technological development in related fields. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of unclear imaging of weak infrared targets and poor adaptability to strong electromagnetic environments in existing mid-wave infrared continuous zoom optical systems, and to provide a large-aperture mid-wave infrared continuous zoom optical system that can achieve electromagnetic shielding. This invention employs a secondary imaging optical configuration, which not only achieves 100% cold stop efficiency but also helps reduce stray light and cold reflections within the optical system itself. The designed fully transmissive large-aperture mid-wave infrared zoom optical system uses optical lenses as shielding gateways from external electromagnetic radiation. By performing zoned shaping and elongation, and zoned coating on selected optical components in the optical system, it not only facilitates ensuring the accuracy of optical axis consistency across the entire field of view during optomechanical assembly and adjustment, but also allows the large optical aperture to receive more incident radiation energy, achieving clear imaging of weak infrared targets and good electromagnetic shielding effectiveness in high electromagnetic environments.

[0006] To achieve the above objectives, the technical solution provided by this invention is:

[0007] A large-aperture mid-wave infrared continuous zoom optical system capable of electromagnetic shielding includes a front fixed assembly, a zoom lens, a compensation lens, a focusing lens, a first relay lens, a second relay lens, and a third relay lens arranged sequentially from the object side to the image side along the optical axis. The front fixed assembly, zoom lens, compensation lens, and focusing lens are used to achieve the first image, with the primary image plane located between the focusing lens and the first relay lens. The first, second, and third relay lenses constitute a relay assembly for performing a second image processing on the image obtained from the first image.

[0008] The front fixed group includes a first front lens and a second front lens arranged sequentially along the optical axis transmission direction; the first front lens is a meniscus silicon positive lens with its convex surface facing the object side, and the second front lens is a meniscus germanium positive lens with its convex surface facing the object side. The zoom lens is a biconcave silicon negative lens, and the compensation lens is a biconvex silicon positive lens; the zoom lens and the compensation lens can reciprocate along the optical axis to realize continuous switching between long focal length and short focal length in the infrared continuous zoom optical system.

[0009] The focusing lens is a meniscus zinc selenide negative lens with its convex surface facing the image side. It can move along the optical axis to maintain the image plane position unchanged during zooming. The first relay lens is a biconvex silicon positive lens, the second relay lens is a biconcave germanium negative lens, and the third relay lens is a biconvex silicon positive lens.

[0010] Among them, the compensating lens and the first relay lens, located outside the light-transmitting area of ​​the front refractive surface and the rear refractive surface, extend outward along their side to form a modified extension structure. The outer wall of the modified extension structure is flat and is used to cooperate with the lens frame for mounting and depositing metal electrodes. In addition, the light-transmitting area of ​​all optical lenses is coated with an anti-reflection film, and the non-light-transmitting area is coated with a metal electrode.

[0011] Furthermore, the infrared continuous zoom optical system has a focal length of 40 mm to 920 mm, a zoom ratio of 23×, and an optical aperture of 230 mm.

[0012] Furthermore, the distance between the vertex of the front refractive surface of the zoom lens and the vertex of the rear refractive surface of the first front lens group is 8mm to 173mm; the distance between the vertex of the rear refractive surface of the zoom lens and the vertex of the front refractive surface of the focusing lens is 3.1mm to 229.7mm; and the distance between the vertex of the rear refractive surface of the compensation lens and the vertex of the front refractive surface of the focusing lens is 4mm to 52mm.

[0013] Furthermore, the focusing lens can move back and forth along the optical axis within a range of ±5mm; the distance between the rear refractive surface of the focusing lens and the front refractive surface of the first relay lens is 168.92mm to 178.92mm.

[0014] Furthermore, both the front and rear refractive surfaces of the first front lens group are spherical.

[0015] The front and rear refractive surfaces of the second front lens, the zoom lens, and the second relay lens are all aspherical.

[0016] The back refractive surfaces of both the compensating lens and the third relay lens are aspherical.

[0017] The front refractive surfaces of both the focusing lens and the first relay lens are aspherical.

[0018] Furthermore, aspherical surfaces satisfy the following expression:

[0019]

[0020] In the formula, Z is the distance vector from the vertex of the aspherical surface to the optical axis at a position of height r. , Represents the paraxial radius of curvature of the mirror surface; The conic coefficient; , , , All are high-order aspherical coefficients.

[0021] Furthermore, the aspherical parameters of the front refractive surface in the second front lens group are as follows: , , , , The aspherical parameters of the back refraction surface are as follows: , , , , .

[0022] The aspherical parameters of the front refractive surface in the zoom lens are as follows: , ,

[0023] , , The aspherical parameters of the back refraction surface are as follows: , , , , .

[0024] The aspherical parameters of the back refractive surface in the compensating lens are as follows: , ,

[0025] , , .

[0026] The aspherical parameters of the front refractive surface in the focusing lens are as follows: , ,

[0027] , , .

[0028] The aspherical parameters of the front refractive surface in the first relay lens are as follows: , , , , .

[0029] The aspherical parameters of the front refractive surface in the second relay lens are as follows: , ,

[0030] , , The aspherical parameters of the back refraction surface are as follows: , , , , .

[0031] The aspherical parameters of the rear refractive surface in the third relay lens are as follows: , , , , .

[0032] Furthermore, the radii of curvature of the front and rear refractive surfaces of the first front lens are 278 mm and 1028 mm, respectively, and the optical apertures are 230 mm and 224.5 mm, respectively; the radii of curvature of the front and rear refractive surfaces of the second front lens are 979.565 mm and 455.197 mm, respectively, and the optical apertures are 204 mm and 190.5 mm, respectively.

[0033] The front and rear refractive surfaces of the zoom lens have radii of curvature of -167.968 mm and 128.051 mm, respectively, and an optical aperture of 50 mm; the front and rear refractive surfaces of the compensation lens have radii of curvature of 242.3 mm and -194.947 mm, respectively, and an optical aperture of 51 mm for both; the front and rear refractive surfaces of the focusing lens have radii of curvature of -85.694 mm and -219.21 mm, respectively, and optical apertures of 29.5 mm and 32 mm, respectively.

[0034] The first relay lens has front and rear refractive surfaces with radii of curvature of 95.723 mm and -197.240 mm, respectively, and an optical aperture of 43 mm for both. The second relay lens has front and rear refractive surfaces with radii of curvature of -23.226 mm and -809.949 mm, respectively, and an optical aperture of 24 mm for both. The third relay lens has front and rear refractive surfaces with radii of curvature of 109.900 mm and -28.157 mm, respectively, and an optical aperture of 12 mm for both.

[0035] Furthermore, the antireflective membrane is magnesium fluoride, and the metal electrode is a gold electrode.

[0036] Furthermore, metal electrodes are plated on the outer wall surface of the modified epitaxial structure.

[0037] The advantages of this invention are:

[0038] The large-aperture continuous zoom mid-wave infrared optical system of this invention adopts a secondary imaging optical configuration, which not only meets the requirement of 100% cold stop efficiency, but also helps to reduce stray light and cold reflection in the optical system itself. Based on a fully transmissive large-aperture mid-wave infrared zoom optical system, it not only facilitates ensuring the accuracy of optical axis consistency across the entire field of view during optomechanical assembly, but also allows the large optical aperture to receive more incident radiation energy, achieving clear imaging of "low, slow, and small" infrared targets.

[0039] Meanwhile, the large-aperture continuous zoom mid-wave infrared optical system of this invention also features a large zoom ratio, enabling it to simultaneously possess a wider search range and higher detail capture capability. By performing zoned reshaping and zoned coating treatments on all optical lenses in this invention, the large-aperture continuous zoom mid-wave infrared optical system is suitable for clear imaging and accurate detection of weak infrared targets in strong electromagnetic environments. This invention boasts advantages such as large aperture, large zoom ratio, and high resolution, achieving excellent imaging quality across the entire focal length range, and is suitable for clear imaging and accurate detection of "low, slow, and small" weak infrared targets in strong electromagnetic environments.

[0040] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0041] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0042] Figure 1-1 This is a schematic diagram of the large-aperture mid-wave infrared continuous zoom optical system that can achieve electromagnetic shielding according to the present invention;

[0043] Figure 1-2 yes Figure 1-1 Enlarged view of a portion of point A in the middle;

[0044] Figure 2 This is a two-dimensional diagram of the short focal length optical system in this invention;

[0045] Figure 3 This is a focal two-dimensional diagram of the optical system in this invention;

[0046] Figure 4 This is a two-dimensional diagram of the long focal length of the optical system in this invention;

[0047] Figure 5 These are the short focal length endpoint diagrams and MTF diagrams of the optical system in this invention at 33 lp / mm;

[0048] Figure 6 These are the focal length diagram and MTF diagram at 33 lp / mm in the optical system of this invention;

[0049] Figure 7 These are the telephoto end-point diagrams and MTF diagrams at 33 lp / mm of the optical system in this invention;

[0050] Figure 8 This is a graph showing the zoom magnification and compensation lens displacement-focal length curves of the optical system in this invention during zooming.

[0051] Figure 9 This is a schematic diagram of the partitioned shaping and extension of the biconvex optical lens in this invention;

[0052] Figure 10 This is a schematic diagram of the partitioned coating of all optical lenses in this invention;

[0053] Figure 11 This is a diagram showing the results of an electromagnetic shielding test conducted after the continuous zoom optical system of this invention was assembled and adjusted.

[0054] Explanation of reference numerals in the attached figures:

[0055] 1-Front fixed group, 101-First front group lens, 102-Second front group lens; 2-Zoom lens, 3-Compensation lens, 4-Focusing lens, 5-First relay lens, 6-Second relay lens, 7-Third relay lens, 8-First infrared filter, 901-Second infrared filter, 902-Cold aperture, 10-Infrared detector target surface, 11-Shaped extensional structure, 12-Light transmission area, 13-Frame, 14-Metal electrode. Detailed Implementation

[0056] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0057] Reference Figure 1-1 and Figure 1-2 This invention provides a large-aperture mid-wave infrared continuous zoom optical system capable of electromagnetic shielding, comprising: a front fixed group, a zoom lens 2, a compensation lens 3, a focusing lens 4, a first relay lens 5, a second relay lens 6, and a third relay lens 7 arranged sequentially from the object side to the image side along the main optical path. The front fixed group includes a first front lens 101 and a second front lens 102 arranged sequentially from the object side to the image side. The incident light beam from the object side is refracted and focused sequentially by the first front lens 101, the second front lens 102, the zoom lens 2, the compensation lens 3, and the focusing lens 4 to achieve the first image. Then, it is refracted and focused sequentially by the first relay lens 5, the second relay lens 6, the third relay lens 7, and the first infrared filter 8 and the second infrared filter combined with the aperture of the infrared detector to achieve the second image on the target surface 10 of the infrared detector. The zoom lens 2 and the compensation lens 3 can move back and forth along the optical axis to achieve zoom imaging within the range of 40mm to 920mm. The first infrared filter 8, the second infrared filter and aperture combination, and the infrared detector target surface 10 are sequentially arranged from the object side to the image side along the main optical path. The second infrared filter and aperture combination includes a second infrared filter 901 and a cold aperture 902 disposed thereon. Specifically, the cold aperture 902 is located at the intersection of the infrared detector window and the maximum off-axis beam of the optical system. The optical system designed in this invention adopts a secondary imaging optical configuration, which not only meets the requirement of 100% cold aperture efficiency but also helps to reduce stray light and cold reflection in the optical system itself.

[0058] In this invention, the optical lens materials are all commonly used infrared materials such as silicon, germanium, and zinc selenide (ZnSe). The infrared light incident direction is object-side, and the light exit direction is image-side. The first front lens 101 is a meniscus positive silicon lens with its convex surface facing the object side and an optical aperture of 230mm. The second front lens 102 is a meniscus positive germanium lens with its convex surface facing the object side. The zoom lens 2 is a biconcave silicon negative lens. The compensation lens 3 is a biconvex silicon positive lens. The focusing lens 4 is a meniscus zinc selenide negative lens with its convex surface facing the image side. The first relay lens 5 is a biconvex silicon positive lens. The second relay lens 6 is a biconcave germanium negative lens. The third relay lens 7 is a biconvex silicon positive lens. The first infrared filter 8, the second infrared filter and aperture combination, and the infrared detector target surface 10 are all inherent components of the detector product and will not be described in detail here.

[0059] This invention provides a large-aperture mid-wave infrared continuous zoom optical system with electromagnetic shielding. The system has an optical aperture of 230mm, a zoom ratio of 23×, and a focal length of 40mm to 920mm. During zooming, the F-number remains constant at 4. It is suitable for large-area mid-wave cooled infrared detectors with a focal length of 1280×1024 pixels at 15μm / F2, achieving high-resolution mid-wave infrared imaging. When the optical system switches from a short focal length of 40mm to a long focal length of 920mm, the zoom lens 2 moves linearly along the optical axis towards the second front lens group 102 to achieve zooming. The compensation lens 3 moves non-linearly towards the second front lens group 102 to compensate for the image plane shift caused by the focal length change, achieving a continuous zoom of 23×. In Figure 1, the solid lines represent the short focal length position, and the dashed lines represent the long focal length position.

[0060] In practical use, the focusing lens 4 in the optical system of this invention can move a maximum of ±5mm along the optical axis to compensate for the cumulative optical path error caused by various factors (optical-mechanical adjustment, temperature drift), ensuring that it can form a clear image across the entire focal length. The distance from the rear refractive surface of the focusing lens 4 to the front refractive surface of the first relay lens 5 ranges from 168.92mm to 178.92mm.

[0061] In one embodiment of the present invention, along the main optical path direction, the two refractive surfaces of the optical lens from the object side to the image side are respectively referred to as the front refractive surface and the rear refractive surface. Specifically, the optical system of the present invention includes eight lenses: a first front lens 101 is a meniscus positive silicon lens with its convex surface facing the object side and an optical aperture of 230 mm; a second front lens 102 is a meniscus positive germanium lens with its convex surface facing the object side, and both its front and rear refractive surfaces are aspherical; a zoom lens 2 is a biconcave silicon negative lens with both its front and rear refractive surfaces aspherical; a compensation lens 3 is a biconvex silicon positive lens with its rear refractive surface aspherical; a focusing lens 4 is a meniscus zinc selenide negative lens with its convex surface facing the image side and its front refractive surface aspherical; a first relay lens 5 is a biconvex silicon positive lens with its front refractive surface aspherical; a second relay lens 6 is a biconcave germanium negative lens with both its front and rear refractive surfaces aspherical; and a third relay lens 7 is a biconvex silicon positive lens with its rear refractive surface aspherical.

[0062] The first front lens 101 has an optical aperture of up to 230mm. Both of its refractive surfaces are spherical, avoiding the use of aspherical designs. The spherical processing technology is simple, and the optical accuracy can be easily guaranteed.

[0063] During the zoom process from 40mm to 920mm, the optical system of this invention has the following distances along the optical axis: the vertex of the front refractive surface of the zoom lens 2 to the vertex of the rear refractive surface of the first front group lens 101 ranges from 8mm to 173mm; the distance from the vertex of the rear refractive surface of the zoom lens 2 to the vertex of the front refractive surface of the compensation lens 3 ranges from 3.1mm to 229.7mm; and the distance from the vertex of the rear refractive surface of the compensation lens 3 to the vertex of the front refractive surface of the focusing lens ranges from 4mm to 52mm. The zoom curve of the optical system is smooth and without inflection points, making it suitable for processing and assembly.

[0064] The following description, based on specific data, illustrates the present invention. In the preferred embodiment, along the principal optical axis, the front and rear refractive surfaces of each optical lens are sequentially numbered from the object side to the image side as S1 to S20. The structural parameters of each optical element in the large-aperture mid-wave infrared continuous zoom optical system capable of electromagnetic shielding according to the present invention are shown in Table 1, and the aspherical coefficients are shown in Table 2. In Table 1, the optical spacing refers to the lens thickness or the center-to-center distance between the front and rear surfaces of adjacent lenses.

[0065] Table 1. Specific parameters of the optical system (unit: mm)

[0066]

[0067] The second front lens 102, zoom lens 2, compensation lens 3, focusing lens 4, first relay lens 5, second relay lens 6, and third relay lens 7 in the optical system of this invention all contain aspherical surfaces. The aspherical surfaces satisfy the following expression:

[0068]

[0069] in, For an aspherical surface along the optical axis at a height of When the position is such that the distance from the vertex of the non-spherical surface is the sag; , Represents the paraxial radius of curvature of the mirror surface; is the conic coefficient; A, B, C, and D are higher-order aspheric coefficients.

[0070] Table 2 Aspherical coefficients of optical lenses

[0071]

[0072] Based on the relevant parameters of the aforementioned large-aperture mid-wave infrared continuous zoom optical system, its optical performance is illustrated through dot plots and modulation transfer function (MTF) graphs, as follows:

[0073] Figure 2 The image shows a two-dimensional diagram of the optical system of the present invention with a short focal length. The zoom lens and the compensating lens are located at the position of the solid line in Figure 1, with a focal length of 40mm.

[0074] Figure 3 The image shows a two-dimensional focal length diagram of the optical system of the present invention. The zoom lens and the compensating lens are located between the solid line and the dashed line in Figure 1, with a focal length of 480 mm.

[0075] Figure 4 The image shows a two-dimensional view of the optical system of the present invention with a focal length of 920 mm. The zoom lens and the compensating lens are located at the position indicated by the dotted line in Figure 1.

[0076] Figure 5 The diagram shows the optical system in this invention at a short focal length, with the zoom lens and compensating lens positioned as shown by the solid line in Figure 1, and a focal length of 40mm. The dot plots for each field of view and the MTF plot at a cutoff frequency of 33 lp / mm are shown below. Figure 5 a and Figure 5 As shown in b. From Figure 5 As can be seen from a, the RMS value of the spot radius of each field of view all meets the requirement of being less than 15μm of the infrared detector pixel size. Figure 5 As can be seen from b, the MTF values ​​of each field of view at the cutoff frequency of 33 lp / mm all meet the requirement of being greater than 0.1.

[0077] Figure 6 The diagram shows the optical system of this invention at the mid-focal position, with the zoom lens and compensator positioned between the solid and dashed lines in Figure 1, and a focal length of 480mm. The dot plots for each field of view and the MTF plot at a cutoff frequency of 33 lp / mm are shown below. Figure 6 a and Figure 6 As shown in b. From Figure 6As can be seen from a, the RMS value of the spot radius of each field of view all meets the requirement of being less than 15μm of the infrared detector pixel size. Figure 6 b indicates that at a cutoff frequency of 33 lp / mm, the MTF values ​​for each field of view all meet the requirement of being greater than 0.1.

[0078] Figure 7 The diagram shows the optical system of this invention at its telephoto position, with the zoom lens and compensating lens located at the position indicated by the dotted line in Figure 1, and a focal length of 920mm. The dot plots for each field of view and the MTF plot at a cutoff frequency of 33 lp / mm are shown below. Figure 7 a and Figure 7 As shown in b. From Figure 7 As can be seen from a, the RMS value of the spot radius of each field of view all meets the requirement of being less than 15μm smaller than the pixel size of the infrared detector; from Figure 7 As can be seen from b, the MTF values ​​of each field of view at the cutoff frequency of 33 lp / mm all meet the requirement of being greater than 0.1.

[0079] Figure 8 The figure shows the zoom magnification and compensation lens displacement-focal length curves of the optical system of the present invention during zooming. As can be seen from the figure, the zoom curve of the optical system is smooth and has no inflection point, which is suitable for processing and assembly.

[0080] Depend on Figure 2-8 As shown, the performance indicators of this optical system have met the expected standards for use.

[0081] Meanwhile, to make the designed infrared continuous zoom optical system suitable for strong electromagnetic environments, in this embodiment of the invention, the biconvex optical lenses of the compensation lens 3 and the first relay lens 5 undergo partitioned shaping and extension processing. The areas of their front and rear refractive surfaces, excluding the light-transmitting aperture, are extended outwards along their sides to form a shaping and extension structure. The outer walls of the shaping and extension structure are all planar, facilitating subsequent installation and metal electrode plating, such as... Figure 9 The diagram shows a schematic of the modified outer extension of a biconvex optical lens. Furthermore, the first front lens group 101, the second front lens group 102, the zoom lens 2, the compensation lens 3, the focusing lens 4, the first relay lens 5, the second relay lens 6, and the third relay lens 7 undergo zoned coating treatment. An anti-reflective coating is deposited on the light-transmitting areas of the optical lenses, and a metal electrode is deposited on the non-light-transmitting areas. Preferably, the anti-reflective coating is magnesium fluoride (MgF3), and the metal electrode is a gold electrode, such as... Figure 10 The diagram shown illustrates the partitioned coating process for an optical lens.

[0082] After the optical lens and frame are modified and coated, strong electromagnetic energy cannot propagate along the gap between the lens and frame, achieving a good electromagnetic shielding effect. Figure 11The figure shows the electromagnetic shielding test results at the imaging core position after the system of the present invention has been assembled and adjusted. SE0 represents the electromagnetic shielding effectiveness of the control group without electromagnetic shielding, and SE1 represents the electromagnetic shielding effectiveness of the present invention. It can be seen from the figure that in the test frequency band of 1GHz to 2GHz, the electromagnetic effectiveness of the present invention far exceeds that of the control group, and meets the usage requirement of greater than 50dB across the entire frequency band.

[0083] In summary, this invention provides a large-aperture mid-wave infrared continuous zoom optical system capable of electromagnetic shielding. Employing a secondary imaging and positive group compensation zoom optical configuration, it achieves 100% cold aperture efficiency while reducing stray light and cold reflections within the optical system itself. The first front lens 101 has an optical aperture of 230mm, enabling it to receive more incident radiation energy and achieve clear imaging of low-, slow-moving, and small infrared targets. During zooming, the zoom lens 2 and compensation lens 3 move back and forth along the optical axis to achieve continuous zooming. Through partitioned reshaping and extension of the optical lenses, and partitioned coating treatment, the optical system of this invention meets the requirements for use under strong electromagnetic conditions. This invention has advantages such as large aperture, large zoom ratio, and high-resolution clear imaging across the entire focal length range, and is suitable for clear imaging and accurate detection of low-, slow-moving, and small infrared targets in strong electromagnetic environments.

[0084] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A large-aperture mid-wave infrared continuous zoom optical system capable of achieving electromagnetic shielding, characterized in that, It includes a front fixed assembly, a zoom lens, a compensation lens, a focusing lens, a first relay lens, a second relay lens, and a third relay lens arranged sequentially from the object side to the image side along the optical axis. The front fixed assembly, zoom lens, compensation lens, and focusing lens are used to achieve the first image, and the primary image plane is located between the focusing lens and the first relay lens; the first relay lens, the second relay lens, and the third relay lens constitute a relay assembly, which is used to perform a second image on the image after the first image. The front fixed group includes a first front lens and a second front lens arranged sequentially along the optical axis transmission direction; the first front lens is a meniscus silicon positive lens with its convex surface facing the object side, and the second front lens is a meniscus germanium positive lens with its convex surface facing the object side. The zoom lens is a biconcave silicon negative lens, and the compensation lens is a biconvex silicon positive lens; the zoom lens and the compensation lens can reciprocate along the optical axis to realize the continuous switching between long focal length and short focal length of the infrared continuous zoom optical system. The focusing lens is a meniscus zinc selenide negative lens with its convex surface facing the image side. It can move along the optical axis to keep the image plane position unchanged during zooming. The first relay lens is a biconvex silicon positive lens, the second relay lens is a biconcave germanium negative lens, and the third relay lens is a biconvex silicon positive lens. Among them, the compensating lens and the first relay lens, located outside the light-transmitting area of ​​the front refractive surface and the rear refractive surface, extend outward along their side to form a modified extension structure. The outer wall of the modified extension structure is flat and is used to cooperate with the lens frame for mounting and depositing metal electrodes. In addition, the light-transmitting area of ​​all optical lenses is coated with an anti-reflection film, and the non-light-transmitting area is coated with a metal electrode.

2. The infrared continuous zoom optical system according to claim 1, characterized in that, The infrared continuous zoom optical system has a focal length of 40mm to 920mm, a zoom ratio of 23×, and an optical aperture of 230mm.

3. The infrared continuous zoom optical system according to claim 2, characterized in that, The distance between the vertex of the front refractive surface of the zoom lens and the vertex of the rear refractive surface of the first front lens group is 8mm to 173mm; the distance between the vertex of the rear refractive surface of the zoom lens and the vertex of the front refractive surface of the focusing lens is 3.1mm to 229.7mm; and the distance between the vertex of the rear refractive surface of the compensation lens and the vertex of the front refractive surface of the focusing lens is 4mm to 52mm.

4. The infrared continuous zoom optical system according to claim 3, characterized in that, The focusing lens can move back and forth along the optical axis within a range of ±5mm; the distance between the rear refractive surface of the focusing lens and the front refractive surface of the first relay lens is 168.92mm to 178.92mm.

5. The infrared continuous zoom optical system according to claim 1 or 2, characterized in that, The front and rear refractive surfaces of the first front lens are both spherical. The front and rear refractive surfaces of the second front lens, the zoom lens, and the second relay lens are all aspherical. The back refractive surfaces of both the compensation lens and the third relay lens are aspherical. The front refractive surfaces of both the focusing lens and the first relay lens are aspherical. Furthermore, the aspherical surface satisfies the following expression: In the formula, It is the distance vector from the vertex of the aspherical surface along the optical axis at a position of height r; , Represents the paraxial radius of curvature of the mirror surface; The conic coefficient; , , , All are high-order aspherical coefficients.

6. The infrared continuous zoom optical system according to claim 5, characterized in that, The aspherical parameters of the front refractive surface in the second front lens group are as follows: , , , ; The aspherical parameters of the back-refracting surface are as follows: , , , , ; The aspherical parameters of the front refractive surface of the zoom lens are as follows: , , ， ， ； The aspherical parameters of the back-refracting surface are as follows: , , , , ; The aspherical parameters of the back refractive surface in the compensation lens are as follows: , , ， ， ； The aspherical parameters of the front refractive surface of the focusing lens are as follows: , , ， ， ； The aspherical parameters of the front refractive surface in the first relay lens are as follows: , , , , ; The aspherical parameters of the front refractive surface in the second relay lens are as follows: , , , , The aspherical parameters of the back refraction surface are as follows: , , , ， ； The aspherical parameters of the rear refractive surface in the third relay lens are as follows: , ， ， ， 。 7. The infrared continuous zoom optical system according to claim 1, characterized in that, The first front lens has front and rear refractive surfaces with radii of curvature of 278 mm and 1028 mm, respectively, and optical apertures of 230 mm and 224.5 mm, respectively; the second front lens has front and rear refractive surfaces with radii of curvature of 979.565 mm and 455.197 mm, respectively, and optical apertures of 204 mm and 190.5 mm, respectively. The zoom lens has front and rear refractive surface radii of curvature of -167.968 mm and 128.051 mm, respectively, and an optical aperture of 50 mm; the compensation lens has front and rear refractive surface radii of curvature of 242.3 mm and -194.947 mm, respectively, and an optical aperture of 51 mm for both; the focusing lens has front and rear refractive surface radii of curvature of -85.694 mm and -219.21 mm, respectively, and optical apertures of 29.5 mm and 32 mm, respectively. The first relay lens has front and rear refractive surfaces with radii of curvature of 95.723 mm and -197.240 mm, respectively, and an optical aperture of 43 mm for both. The second relay lens has front and rear refractive surfaces with radii of curvature of -23.226 mm and -809.949 mm, respectively, and an optical aperture of 24 mm for both. The third relay lens has front and rear refractive surfaces with radii of curvature of 109.900 mm and -28.157 mm, respectively, and an optical aperture of 12 mm for both.

8. The infrared continuous zoom optical system according to claim 1 or 2, characterized in that, The antireflective membrane is magnesium fluoride, and the metal electrode is a gold electrode.

9. The infrared continuous zoom optical system according to claim 8, characterized in that, Metal electrodes are plated on the outer wall surface of the modified epitaxial structure.

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