Multi-component linked continuous zoom infrared optical system

Abstract

The present invention discloses a multi-component linked continuous zoom infrared optical system comprising a first fixed lens, a variator lens, a first compensating lens, a second compensating lens, a second fixed lens, a third fixed lens group, and an image plane, arranged sequentially from the object side to the image side along the optical axis. The third fixed lens group comprises a first rear fixed lens, a second rear fixed lens, and a third rear fixed lens, arranged sequentially from the object side to the image side. The variator lens, the first compensating lens, and the second compensating lens are all movable along the optical axis. The multi-component linked continuous zoom infrared optical system operates in a wavelength range of 3.7 μm to 4.8 μm. The system is applicable to medium-wave infrared light and employs a secondary imaging method. The variator lens achieves magnification change through axial movement. The first compensating lens and the second compensating lens compensate for image plane displacement caused by the variator lens through axial movement. This system can achieve a large magnification ratio while making the optical system structure more compact, thereby achieving miniaturization.

Description

Technical Field

[0001] The present invention relates to the technical field of optical systems, and in particular to a multi-component linked continuous zoom infrared optical system. Background Art

[0002] Continuous zoom optical systems can be divided into mechanically compensated continuous zoom optical systems and optically compensated continuous zoom optical systems. A system in which all the moving components in a zoom system are fixed together and move linearly along the optical axis is called an optically compensated continuous zoom optical system. A zoom system in which the movement of one moving component is compensated by the image plane displacement generated by the movement of another moving component is called a mechanically compensated continuous zoom optical system. An optically compensated continuous zoom optical system uses the linear movement of the lens groups in the optical system to achieve image plane compensation at a limited number of specific positions, thereby achieving continuous zoom. However, its structure is relatively long and the optical system imaging quality is not high. Mechanically compensated zoom optical systems, on the other hand, can continuously change the focal length of the entire optical system by changing the relative positions of the zoom lens and the compensation lens. They have the advantages of simple structure and low development cost. However, current mechanically compensated zoom optical systems still face the design contradiction of large zoom ratio and light weight. Summary of the Invention

[0003] The main purpose of the present invention is to propose a multi-component linkage continuous zoom infrared optical system. On the basis of the traditional optical compensation zoom system, it breaks the fixed connection mode of the zoom lens and the compensation lens in the existing technology, and enables the zoom lens and the compensation lens to move independently, thereby realizing a multi-component linkage and large zoom ratio infrared optical system.

[0004] To achieve the above objectives, the present invention provides a multi-component linked continuous zoom infrared optical system, comprising a first fixed lens, a variator lens, a first compensating lens, a second compensating lens, a first movable lens, a third fixed lens group, and an image plane, which are sequentially arranged from the object side to the image side along the optical axis. The third fixed lens group comprises a first rear fixed lens, a second rear fixed lens, and a third rear fixed lens, which are sequentially arranged from the object side to the image side. The variator lens, the first compensating lens, and the second compensating lens are all movable along the optical axis.

[0005] The operating band of the multi-component linked continuous zoom infrared optical system is set to 3.7 μm to 4.8 μm.

[0006] Optionally, the total optical system length TTL of the multi-component linked continuous zoom infrared optical system is less than 250 mm.

[0007] Optionally, the range of the zoom ratio Γ of the multi-component linked continuous zoom infrared optical system is set to 1<Γ≤40.

[0008] Optionally, the F-number range of the multi-component linked continuous zoom infrared optical system is set to 2≤F≤5.5.

[0009] Optionally, the first movable lens is movable along the optical axis.

[0010] Optionally, the first fixed lens is a meniscus spherical lens with positive optical power, and its concave surface is arranged toward the image plane, the magnification lens is a biconcave aspheric lens with negative optical power, the first compensation lens is a biconvex aspheric lens with positive optical power, the second compensation lens is a meniscus aspheric lens with negative optical power, and its convex surface is arranged toward the image plane, the first movable lens is a meniscus aspheric lens with positive optical power, and its concave surface is arranged toward the image plane, the first rear fixed lens is a meniscus aspheric lens with negative optical power, and its convex surface is arranged toward the image plane, the second rear fixed lens is a biconvex aspheric lens with positive optical power, and the third rear fixed lens is a meniscus aspheric lens with positive optical power, and its concave surface is arranged toward the image plane.

[0011] Optionally, the first fixed lens, the variable power lens, the first compensation lens, the second compensation lens, the first movable lens, the first rear fixed lens, the second rear fixed lens, and the third rear fixed lens are all aspherical lenses.

[0012] Optionally, the first fixed lens, the first compensation lens, the first movable lens and the first rear fixed lens are made of silicon glass material;

[0013] The zoom lens, the second compensation lens and the third rear fixed lens are made of germanium glass material;

[0014] The second rear fixed lens is made of calcium fluoride glass.

[0015] Optionally, a distance between the first compensation lens and the second compensation lens is L1, wherein 2 mm ≤ L1 ≤ 49.6 mm.

[0016] Optionally, the distance between the variator lens and the first compensation lens is L2, where 2.7 mm ≤ L2 ≤ 81.7 mm.

[0017] The technical solution of the present invention is applicable to medium-wave infrared light and adopts a secondary imaging method. Zooming is achieved through the linkage of the three components of the variator lens, the first compensation lens, and the second compensation lens. The variator lens achieves magnification through axial movement, and the first compensation lens and the second compensation lens compensate for the image plane displacement caused by the variator lens through axial movement. The variator lens, the first compensation lens, and the second compensation lens move independently and separately, and can all perform nonlinear movement. In addition, in this optical system, the magnification function and the compensation function are relative, that is, the compensation lens can also perform the magnification function, and the variator lens can also perform the compensation function, so as to give full play to the functions of the variator lens and the compensation lens. Therefore, when the magnification ratio increases, the optical tube length of the optical system can still be limited to a smaller range, and a large magnification ratio can be achieved while making the optical system structure more compact, thereby achieving the purpose of miniaturization. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] 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.

[0019] Figure 1 A schematic diagram of an embodiment (telephoto) of a multi-component linked continuous zoom infrared optical system provided by the present invention;

[0020] Figure 2 for Figure 1 Schematic diagram of the medium multi-component linked continuous zoom infrared optical system (medium focus);

[0021] Figure 3 for Figure 1 Schematic diagram of the multi-component linked continuous zoom infrared optical system (short focus);

[0022] Figure 4 for Figure 1 MTF curve of the multi-component linked continuous zoom infrared optical system at the wide-angle end;

[0023] Figure 5 for Figure 1 MTF curve of the multi-component linked continuous zoom infrared optical system at intermediate magnification;

[0024] Figure 6 for Figure 1 MTF curve of the multi-component linked continuous zoom infrared optical system at the telephoto end.

[0025] Description of Figure Numbers:

[0026]

[0027] 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

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Infrared imaging technology uses the difference in infrared radiation between the target and the background, or the difference in their reflection of natural light sources, to form an image. It is generally used for detecting, identifying, tracking, and aiming targets at night or during adverse weather conditions during the day. It is a passive imaging technology with strong concealment and anti-interference capabilities. Continuous zoom optical systems can maintain clear imaging of the target during a continuous change in the field of view, and will not lose track of the target due to field switching, thus gaining widespread application. In recent years, with the development of infrared imaging technology, the application of airborne infrared systems for target detection, identification, tracking, and aiming requires thermal imagers with longer recognition distances and larger search ranges, leading to an increasing demand for ultra-long focal length and ultra-large field of view continuous zoom optical systems.

[0032] However, conventional zoom optical systems are difficult to achieve with large zoom ratios and miniaturization requirements. Consequently, these systems must be optimized by adding a moving lens group to the zoom objective optical system, ensuring that the optical system remains compact during zooming. Therefore, the present invention provides a multi-component linked continuous zoom infrared optical system. This system, based on conventional optical compensation zoom systems, breaks the existing pattern of fixed connection between the zoom lens and the compensation lens, allowing the zoom lens and the compensation lens to move independently, thereby achieving a multi-component linked, large zoom ratio infrared optical system. Figures 1 to 3 This is an embodiment of the multi-component linked continuous zoom infrared optical system provided by the present invention. Figures 4 to 6 The MTF curves of the optical systems are shown respectively.

[0033] Please refer to Figures 1 to 3 The multi-component linked continuous zoom infrared optical system 100 includes a first fixed lens 1, a variator lens 2, a first compensation lens 3, a second compensation lens 4, a first movable lens 5, a third fixed lens group 6 and an image plane, which are arranged in sequence from the object side to the image side in the direction of the optical axis. The third fixed lens group 6 includes a first rear fixed lens 6-1, a second rear fixed lens 6-2, and a third rear fixed lens 6-3, which are arranged in sequence from the object side to the image side. The variator lens 2, the first compensation lens 3 and the second compensation lens 4 can all be movable along the optical axis. The working band of the multi-component linked continuous zoom infrared optical system 100 is set to 3.7μm~4.8μm.

[0034] The technical solution of the present invention is applicable to medium-wave infrared light and adopts a secondary imaging method. Zooming is achieved through the linkage of the three components of the variator lens 2, the first compensation lens 3, and the second compensation lens 4. The variator lens 2 achieves magnification through axial movement, and the first compensation lens 3 and the second compensation lens 4 compensate for the image plane displacement caused by the variator lens 2 through axial movement. The variator lens 2, the first compensation lens 3, and the second compensation lens 4 move separately and independently, and can all perform nonlinear movement. In this optical system, the magnification function and the compensation function are relative, that is, the compensation lens can also perform the magnification function, and the variator lens 2 can also perform the compensation function, so as to give full play to the functions of the variator lens 2 and the compensation lens. As a result, the optical tube length of the optical system can be limited to a smaller range when the magnification ratio increases, and the optical system structure can be made more compact while achieving a large magnification ratio, thereby achieving the purpose of miniaturization.

[0035] Specifically, an imaging beam from the object side sequentially passes through the first fixed lens 1, the variator lens 2, the first compensating lens 3, the second compensating lens 4, the first movable lens 5, and the third fixed lens group 6, forming an image on the image plane. As the variator lens 2 moves toward the object, the first compensating lens 3 moves toward the image, and the second compensating lens 4 moves toward the object, the focal length shortens. As the variator lens 2 moves toward the image, the first compensating lens 3 moves toward the object, and the second compensating lens 4 moves toward the image, the focal length lengthens. Thus, continuous zooming is achieved through the combined movement of the variator lens 2, the first compensating lens 3, and the second compensating lens 4.

[0036] Furthermore, the total optical system length TTL of the multi-component linked continuous zoom infrared optical system 100 is less than 250 mm, the focal length range is 30 mm-600 mm, and it is equipped with a medium-wave infrared F4 cooled detector.

[0037] Furthermore, the short focal length of the optical system is f1, and the long focal length is f2. The corresponding magnification ratio of the multi-component linked continuous zoom infrared optical system 100 is: Γ=f2 / f1. In this embodiment, the range of Γ is set to 1<Γ≤40, and the range of the F number of the multi-component linked continuous zoom infrared optical system 100 is set to 2≤F≤5.5.

[0038] Not only that, the first movable lens 5 can move along the optical axis, so as to realize the image plane drift under different working temperatures and the image plane drift compensation function at different object distances. It can achieve an operating temperature range of -40℃~+60℃, and the image quality is good under the conditions of the imaging object distance range of 10m to infinity, and can ensure that the focal plane position remains unchanged.

[0039] The present invention is not limited to the specific types of lenses involved. In one embodiment, the first fixed lens 1, the zoom lens 2, the first compensating lens 3, the second compensating lens 4, the first movable lens 5, the first rear fixed lens 6-1, the second rear fixed lens 6-2, and the third rear fixed lens 6-3 are all aspherical lenses. In other embodiments, all lenses may be spherical lenses, or some lenses may be spherical lenses and the rest may be aspherical lenses, as long as they can achieve the corresponding functions. The present invention does not require any special surface shape when selecting lenses, which reduces processing difficulty and ensures good imaging quality throughout the entire zoom range.

[0040] In this embodiment, the selection of lenses is as follows: the first fixed lens 1 is a meniscus spherical lens with positive optical focal length, and its concave surface is arranged toward the image plane; the magnification lens 2 is a biconcave aspheric lens with negative optical focal length; the first compensation lens 3 is a biconvex aspheric lens with positive optical focal length; the second compensation lens 4 is a meniscus aspheric lens with negative optical focal length, and its convex surface is arranged toward the image plane; the first movable lens 5 is a meniscus aspheric lens with positive optical focal length, and its concave surface is arranged toward the image plane; the first rear fixed lens 6-1 is a meniscus aspheric lens with negative optical focal length, and its convex surface is arranged toward the image plane; the second rear fixed lens 6-2 is a biconvex aspheric lens with positive optical focal length; and the third rear fixed lens 6-3 is a meniscus aspheric lens with positive optical focal length, and its concave surface is arranged toward the image plane.

[0041] Furthermore, the first fixed lens 1, the first compensating lens 3, the first movable lens 5, and the first rear fixed lens 6-1 are made of silicon glass; the variator lens 2, the second compensating lens 4, and the third rear fixed lens 6-3 are made of germanium glass; and the second rear fixed lens 6-2 is made of calcium fluoride glass. All eight lenses in this embodiment are made of common domestic infrared materials such as silicon, germanium, and calcium fluoride, with glass of varying refractive index and thickness selected for different locations.

[0042] Specifically, the optical performance selection of the lens in this embodiment can be referred to Table 1. The data in the table is a set of data of the multi-component linked continuous zoom infrared optical system 100 in this embodiment, including the surface number, surface type, radius, thickness and optical material. The positive and negative signs of the radius meet the basic sign rules of optics. Each set of data in the optical material represents the refractive index and Abbe number of the material.

[0043] Table 1

[0044]

[0045] In addition, in this embodiment of the present invention, the distance between the first compensating lens 3 and the second compensating lens 4 is L1, where 2mm≤L1≤49.6mm. The distance between the variator lens 2 and the first compensating lens 3 is L2, where 2.7mm≤L2≤81.7mm. In the long-focus and short-focus states, the directions and travels of the variator lens 2, the first compensating lens 3, and the second compensating lens 4 along the optical axis vary. The specific distance values ​​are shown in Table 2 below.

[0046] Table 2

[0047]

[0048] Figures 4 to 6The MTF curves of the multi-component linked continuous zoom infrared optical system are shown respectively when the system is at the wide-angle end, the intermediate magnification and the telephoto end.

[0049] In order to quickly and effectively design a better initial structure, the present invention proposes a method of combined design using parameter setting and optical design software. The specific design steps are as follows:

[0050] Step 1: To achieve smooth replacement of the compensating lenses, the magnification of the variator lens 2 and each compensating lens is assumed to be -1 as the starting state for the calculation. Assuming the focal length of the variator lens 2 is -1, the focal length of each compensating lens, the object-image distance between each compensating lens and the variator lens 2, and the spacing between each compensating lens and each other are calculated.

[0051] Step 2: Set the magnification of the zoom lens 2 at long focus, calculate the object distance, image distance, and movement along the optical axis of the zoom lens 2 at long focus, and then calculate the magnification of the zoom lens 2 and the compensation lens at short focus using the zoom ratio;

[0052] Step 3: Based on the initial state (the magnification of the zoom lens 2 and the compensation lens is -1), calculate the parameters of the optical system at short focus.

[0053] Step 4: Select the short focus state and calculate the focal length of the first fixed lens 1;

[0054] Step 5: Select the short focus state, set the magnification of the third fixed lens group 6, and then calculate the focal length of the third fixed lens group 6;

[0055] Step 6: Obtain the distances between components at long, medium, and short focal lengths by scaling the system parameters.

[0056] Step 7: Bring the calculated parameters into the optical design software, optimize the system's curvature radius and aspheric coefficient and other parameters, optimize the control cam curve, and ensure that the cam curve is smooth and has no inflection points;

[0057] Step 8: Move the first movable lens 5 so that the system can obtain higher imaging quality under high and low temperature conditions and under long and short focus conditions, thereby obtaining a focusing stroke of the first movable lens 5;

[0058] Step 9: Simulate and analyze the system's narcissistic reflections. Based on the analyzed narcissistic reflection paths, control the curvature radius of the surface that may form narcissistic reflections, change the incidence angles of the paraxial and marginal rays on the surface, constrain the spacing between lens groups, and adjust the incident height of the light on the lens.

[0059] Step 10: Ensure the optical axis consistency of the system through guide shafts, linear bearings, etc.

[0060] The technical solution of the present invention has the following advantages over the prior art:

[0061] 1. Using domestic common infrared materials such as silicon and germanium, the entire system uses only 8 lenses, all of which are spherical or aspherical, without special surface shapes, to ensure good imaging quality throughout the entire zoom range. The MTF value of each field of view is above 0.2 at 33lp / mm.

[0062] 2. Through multi-element linked zoom, a 20x zoom ratio can be achieved in the continuous zoom state. By rationally selecting the structural form of each element, rationally allocating the optical focal length, and rationally matching the glass materials, such as using a negative lens group for zooming, and using positive and negative lens groups for compensation lenses, the system aberrations and optical length are comprehensively balanced.

[0063] 3. During the design process, the cam curve is optimized and controlled, and a segmented form is used in curve fitting to ensure that the cam curve is smooth and has no inflection points.

[0064] 4. Conduct simulation analysis on the system's cold reflections, and strictly control the cold reflections based on the analyzed cold reflection light path. For example, the aperture diaphragm of the optical system coincides with the cold diaphragm of the detector to ensure 100% cold diaphragm matching; set requirements for the lens film system to ensure a transmittance of ≥99%; for surfaces that may form cold reflections, control their curvature radius, change the exit angles of the paraxial light and edge light on the surface, constrain the spacing between lens groups, and adjust the incident height of the light on the lens.

[0065] 5. Ensure the optical axis consistency of the system through guide shafts, linear bearings, etc.

[0066] 6. The distance of the first movable lens 5 is adjusted forward and backward to achieve -40°C~+60°C working temperature compensation, focusing of different imaging distances and non-uniform correction compensation.

[0067] 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 inventive 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. A multi-component linked continuous zoom infrared optical system, characterized in that: The optical system comprises a first fixed lens, a variator lens, a first compensating lens, a second compensating lens, a first movable lens, a third fixed lens group, and an image plane, which are arranged in sequence from the object side to the image side along the optical axis. The third fixed lens group comprises a first rear fixed lens, a second rear fixed lens, and a third rear fixed lens, which are arranged in sequence from the object side to the image side. The variator lens, the first compensating lens, and the second compensating lens are all movable along the optical axis. The operating wavelength band of the multi-element linked continuous zoom infrared optical system is set to 3.7 μm to 4.8 μm; The total optical system length TTL of the multi-component linked continuous zoom infrared optical system is less than 250 mm; The first movable lens is movable along the optical axis.

2. The multi-component linked continuous zoom infrared optical system according to claim 1, characterized in that: The range of the zoom ratio Γ of the multi-component linked continuous zoom infrared optical system is set to 1<Γ≤40.

3. The multi-component linked continuous zoom infrared optical system according to claim 1, wherein: The F number range of the multi-component linked continuous zoom infrared optical system is set to 2≤F≤5.

5.

4. The multi-component linked continuous zoom infrared optical system according to any one of claims 1 to 3, wherein: The first fixed lens is a meniscus spherical lens with positive optical power, and its concave surface is arranged toward the image plane. The magnification lens is a biconcave aspheric lens with negative optical power. The first compensation lens is a biconvex aspheric lens with positive optical power. The second compensation lens is a meniscus aspheric lens with negative optical power, and its convex surface is arranged toward the image plane. The first movable lens is a meniscus aspheric lens with positive optical power, and its concave surface is arranged toward the image plane. The first rear fixed lens is a meniscus aspheric lens with negative optical power, and its convex surface is arranged toward the image plane. The second rear fixed lens is a biconvex aspheric lens with positive optical power. The third rear fixed lens is a meniscus aspheric lens with positive optical power, and its concave surface is arranged toward the image plane.

5. The multi-component linked continuous zoom infrared optical system according to claim 1, wherein: The first fixed lens, the variable power lens, the first compensation lens, the second compensation lens, the first movable lens, the first rear fixed lens, the second rear fixed lens, and the third rear fixed lens are all aspherical lenses.

6. The multi-component linked continuous zoom infrared optical system according to claim 1, wherein: The first fixed lens, the first compensation lens, the first movable lens and the first rear fixed lens are made of silicon glass; The zoom lens, the second compensation lens and the third rear fixed lens are made of germanium glass material; The second rear fixed lens is made of calcium fluoride glass.

7. The multi-component linked continuous zoom infrared optical system according to claim 1, wherein: The distance between the first compensation lens and the second compensation lens is L1, wherein 2mm≤L1≤49.6mm.

8. The multi-component linked continuous zoom infrared optical system according to claim 1, wherein: The distance between the variator lens and the first compensation lens is L2, where 2.7 mm ≤ L2 ≤ 81.7 mm.

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