Medium-wave infrared refrigeration continuous zooming transmission-type micro-scanning optical system

Abstract

The utility model provides a medium-wave infrared refrigeration continuous zooming transmission-type micro-scanning optical system, which comprises a first fixed lens, a zoom lens, a compensation lens group, a second fixed lens, a first reflector, a second reflector, a third fixed lens group and a micro-scanning lens which are sequentially arranged from an object space to an image space along a light propagation direction, wherein the compensating lens group comprises a first compensating lens and a second compensating lens, and the third fixed lens group comprises a third fixed lens and a fourth fixed lens. By introducing the micro-scanning lens, the spatial resolution is effectively improved, the precision of the micro-scanning lens is high, and the optical axis consistency is easy to guarantee. Through the optimization of the focal length and the tolerance of the micro-scanning lens, the displacement of the micro-scanning lens at different variable focus positions and the displacement of an image point can be kept in an accurate proportional relation, and in the micro-scanning process, the image quality of an optical system is not influenced, and the focusing of an object distance from 50m to infinity is realized.

Description

Technical Field

[0001] The utility model relates to an optical system, in particular to a medium-wave infrared refrigeration continuous zoom transmission micro-scanning optical system, belonging to the technical field of photoelectric detection. Background Art

[0002] In the photoelectric detection system, the spatial resolution of the image will directly affect the detection distance of the target. In some cases, due to the undersampling of the infrared detector array, the optical resolution of the infrared continuous zoom optical system cannot be effectively utilized, resulting in a decrease in the spatial resolution of the final image. Micro-scanning imaging technology reconstructs a high-resolution image by repeatedly sampling the same scene with multiple low-resolution images that are slightly displaced from each other and continuous in time series, so as to reduce the image aliasing effect caused by undersampling. According to the optical elements used in micro-scanning, it can be divided into two types: transmission micro-scanning and reflection micro-scanning. Among them, compared with reflection micro-scanning, the advantage of transmission micro-scanning is that it can reduce one optical path deflection for the optical system, which is more conducive to ensuring the consistency of the optical axis and the micro-scanning accuracy is high. However, the existing technology still lacks a continuous zoom transmissive micro-scanning optical system. The design difficulty of this type of optical system is that, at any focal length of continuous zoom, it is necessary to ensure that the displacement of the micro-scanning lens and the displacement of the focal plane meet a predetermined proportional relationship, and make the image quality of the optical system insensitive to the displacement of the micro-scanning lens, otherwise the servo difficulty of the micro-scanning lens will be greatly increased, thereby reducing the image quality. Therefore, it is necessary to improve the existing technology. Utility Model Content

[0003] In order to solve the problem that the prior art cannot realize transmission micro-scanning in the process of continuous zooming, the utility model provides a medium-wave infrared refrigeration continuous zoom transmission micro-scanning optical system.

[0004] The utility model is completed by the following technical scheme: a medium-wave infrared cooling continuous zoom transmission type micro-scanning optical system, comprising a first fixed lens, a zoom lens, a compensation lens group, a second fixed lens, a first reflector, a second reflector, a third fixed lens group, and a micro-scanning lens arranged in sequence from the object side to the image side along the light propagation direction, wherein the compensation lens group includes a first compensation lens and a second compensation lens, and the third fixed lens group includes a third fixed lens and a fourth fixed lens, characterized in that:

[0005] The first fixed lens is a meniscus lens with positive optical power, with its convex surface facing the object, for converging the light beam;

[0006] The zoom lens is a double concave lens with negative optical power, and realizes continuous zooming by moving along the optical axis.

[0007] The first compensation lens of the compensation lens group is set as a positive meniscus lens with a convex surface facing the image side, and the second compensation lens is set as a double convex lens with a positive optical power. The compensation lens group compensates for the image shift caused by the zooming process by axial movement;

[0008] The second fixed lens is a meniscus lens with negative focal power, with its convex surface facing the object, and realizes temperature compensation and long and short distance focusing through axial movement;

[0009] The first rear fixed lens of the third fixed lens group is a positive meniscus lens with a convex surface facing the object, and the second rear fixed lens is a negative meniscus lens with a convex surface facing the object. The third fixed lens group is used to converge the light twice;

[0010] The micro scanning lens is a biconvex positive lens with positive optical power, and realizes the micro scanning function by moving in two orthogonal directions, horizontal and pitch, in the radial plane;

[0011] The first reflector and the second reflector are both plane reflectors, used for light path folding;

[0012] In order to converge the light beam through the first fixed lens, and then change the focal length and increase the magnification ratio through the zoom lens, and then compensate for the image shift in the zoom process through the compensation lens group, and then achieve temperature compensation and long and short distance focusing through the second fixed lens. After the light path is changed by the first and second reflectors, the light is converged for the second time by the third fixed lens group, and finally the system micro-scanning is achieved by the scanning microlens, which doubles the sampling frequency in each direction, improves the resolution of the system, and can ensure that the image is clear and the image shift ratio is correct during the micro-scanning process at any variable focus position.

[0013] The medium-wave infrared refrigerated continuous zoom micro-scanning optical system adopts a secondary imaging method to ensure 100% cold aperture efficiency and compress the aperture of the first lens. It is suitable for medium-wave refrigerated detectors. The working band of the optical system is set to 3.7μm~4.8μm, and the F number is 3.

[0014] The variable power lens and the compensation lens group are configured as lenses that move along the axial direction.

[0015] The micro scanning lens is configured to move in two orthogonal directions, horizontal and pitch, within a radial plane.

[0016] The utility model has the following advantages and effects: adopting the above scheme, by introducing a transmission type micro scanning mechanism into the infrared continuous zoom optical system, the spatial resolution can be effectively improved on the basis of the existing infrared detector, and the micro scanning lens has high precision and is easy to ensure the consistency of the optical axis. By optimizing the focal length and tolerance of the micro scanning lens, the displacement of the micro scanning lens and the displacement of the image point at different focal points can maintain an accurate proportional relationship, and in the process of micro scanning, the image quality of the optical system will not be affected. The zoom method of negative lens magnification and positive lens compensation is adopted, and the high and low temperature compensation and the focusing control of the long and short distances are performed through the second fixed lens to optimize the high and low temperature and long and short distance image quality. It can be applied to the servo method of cam structure zoom. The optical system has good imaging quality within the full focal range. At the same time, the cam zoom curve is smooth throughout the whole process without inflection points, and the working temperature of -40℃ to 60℃ is compensated to achieve focusing of the object distance from 50m to infinity. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural diagram of the optical system of the utility model;

[0018] Figure 2 This is a two-dimensional diagram of the 306mm long focal length of the utility model;

[0019] Figure 3 This is a 2D diagram of the 51mm short focal length of the present utility model;

[0020] Figure 4 The transfer function curves of each field of view at the telephoto end of the utility model;

[0021] Figure 5 It is a spot diagram of each field of view at the telephoto end of the utility model;

[0022] Figure 6 The transfer function curves of each field of view at the short focal end of the utility model;

[0023] Figure 7 It is a spot diagram of each field of view at the short focal end of the utility model;

[0024] Figure 8 The transfer function curves of each field of view when the telephoto end micro-scanning lens of the utility model moves 15um in the radial direction;

[0025] Fig. 9 This is the transfer function curve of each field of view when the micro-scanning lens moves 15um in the radial direction at the short focal end of the utility model;

[0026] Fig.10 This is the transfer function curve of each field of view at the telephoto end of the utility model at a high temperature of 60°C;

[0027] Fig.11This is the transfer function curve of each field of view at the telephoto end of the utility model at a low temperature of -40°C. DETAILED DESCRIPTION

[0028] The utility model is further described below with reference to an embodiment given in the accompanying drawings.

[0029] The utility model provides a medium-wave infrared cooling continuous zoom transmission micro-scanning optical system, comprising a first fixed lens 1, a variable magnification lens 2, a compensation lens group, a second fixed lens 5, a first reflector 6, a second reflector 7, a third fixed lens group, and a micro-scanning lens 10, which are arranged in sequence from the object side to the image side along the light propagation direction, wherein: the compensation lens group comprises a first compensation lens 3 and a second compensation lens 4; the third fixed lens group comprises a first rear fixed lens 8 and a second rear fixed lens 9, wherein:

[0030] The first fixed lens 1 is a meniscus lens with positive optical power;

[0031] The zoom lens 2 is a biconcave lens with negative optical power;

[0032] The first compensation lens 3 of the compensation lens group is a meniscus lens with positive optical power, with its convex surface facing the image side, and the second compensation lens 4 is a biconvex lens with positive optical power;

[0033] The second fixed lens 5 is a meniscus lens with negative optical power, with its convex surface facing the object;

[0034] The first rear fixed lens 8 of the third fixed lens group is a meniscus lens with positive focal length, with its convex surface facing the object, and the second rear fixed lens 9 is a meniscus lens with negative focal length, with its convex surface facing the object;

[0035] The micro scanning lens 10 is a biconvex positive lens with positive optical power;

[0036] The first reflector 6 and the second reflector 7 are both plane reflectors;

[0037] The variable-power lens 2 and the compensating lens groups 3 and 4 achieve continuous zooming by cooperating and moving along the axial direction. The variable-power lens moves from right to left with a moving stroke of 50 mm, and the compensating lens group moves from left to right with a moving stroke of 21 mm.

[0038] The second fixed lens 5 can achieve temperature compensation and long and short distance focusing by axial movement with a movement stroke of 1 mm;

[0039] The first reflector 6 and the second reflector 7 are both plane reflectors, used to fold the light path emitted from the second fixed lens by 180°, thereby reducing the length and volume of the optical system;

[0040] The micro scanning lens 10 is a biconvex lens with positive optical power, and realizes micro scanning of the image point on the image plane by moving 15 μm in two orthogonal directions of horizontal and pitch in the radial plane;

[0041] The positions of the lenses of the optical system provided by the utility model at the long focal end and the short focal end are respectively as follows: Figure 2 and Figure 3 shown.

[0042] In the embodiment of the utility model, the material of the first fixed lens 1 is silicon, the material of the zoom lens 2 is germanium, the material of the first compensation lens 3 is silicon, the material of the second compensation lens 4 is zinc selenide, the material of the second fixed lens 5 is germanium, the material of the first rear fixed lens 8 is silicon, the material of the second rear fixed lens 9 is zinc sulfide, and the material of the micro scanning lens 10 is silicon.

[0043] In the embodiment of the utility model, the focal length variation range is 306-51mm, and the magnification ratio is 6 times. In order to ensure 100% cold aperture efficiency and to compress the aperture of the first lens, a secondary imaging method is adopted. The system as a whole adopts 8 lenses to meet the 6-fold magnification ratio. It is suitable for medium-wave cooled detectors, the working band is 3.7-4.8μm, the F number is 3, the number of pixel units is 640×512, and the pixel unit size is 15μm.

[0044] During operation, the light beam is converged by the first fixed lens 1, and then the zoom lens 2 changes the focal length and increases the zoom ratio. After that, the image shift caused by the zoom process is compensated by the compensation lens groups 3 and 4, and then the second fixed lens 5 performs temperature compensation and long and short distance focusing. After the light path is folded by the first and second reflectors 6 and 7, the light is converged for the second time by the third fixed lens group 8 and 9, and finally the micro scanning is completed by the scanning micro lens 10.

[0045] Specifically, the optical performance selection of the lens in this embodiment can refer to Table 1, which is the optical structure parameter data of the medium-wave infrared cooling continuous zoom micro-scanning optical system of the utility model at a focal length of 306 mm, including the lens name, surface number, surface type, radius, curvature radius, thickness and optical material, and the positive and negative values ​​of the radius meet the basic optical sign rules.

[0046] Table 1 Optical structure parameters

[0047]

[0048] The infrared continuous zoom transmission micro-scanning optical system of the utility model has good imaging quality in the full focal length range, and the cam zoom curve is smooth without inflection points throughout the entire process. The optical transfer function and point diagram of the optical system at the telephoto end are respectively as follows: Figure 4 and Figure 5As shown in the figure, the optical transfer function and point diagram at the short focal end are Figure 6 and Figure 7 shown.

[0049] The infrared continuous zoom transmission micro-scanning optical system of the utility model effectively controls the tolerance of each lens during the design process, reduces the difficulty of processing and adjustment, and ensures good engineering performance of the optical system. By optimizing the eccentricity tolerance of the micro-scanning lens at each focal length position during the optimization process, it is ensured that the image quality of the optical system is not affected during the micro-scanning process within the full focal range. The optical transfer function in the micro-scanning state at the long focal end and the optical transfer function in the micro-scanning state at the short focal end are respectively as follows: Figure 8 and Fig. 9 shown.

[0050] The infrared continuous zoom transmission micro-scanning optical system of the utility model adopts the axial movement of the second fixed lens for temperature compensation and long-distance focusing. By optimizing the high and low temperature and long and short distance image quality, it realizes compensation for the working temperature of -40℃ to 60℃ and realizes focusing for the object distance from 50m to infinity. The optical transfer functions of the high temperature 60℃ and low temperature -40℃ environment at the telephoto end are respectively as follows: Fig.10 and Fig.11 shown.

[0051] Finally, it should be noted that the above is only a preferred embodiment of the utility model, and does not limit the patent scope of the utility model. All equivalent structural changes made by using the contents of the utility model specification and drawings under the utility model concept, or directly / indirectly used in other related technical fields are included in the patent protection scope of the utility model.

Claims

1. A medium-wave infrared cooling continuous zoom transmission micro-scanning optical system, comprising a first fixed lens, a zoom lens, a compensation lens group, a second fixed lens, a first reflector, a second reflector, a third fixed lens group, and a micro-scanning lens arranged in sequence from the object side to the image side along the light propagation direction, wherein the compensation lens group includes a first compensation lens and a second compensation lens, and the third fixed lens group includes a third fixed lens and a fourth fixed lens, characterized in that: The first fixed lens is a meniscus lens with positive optical power; The zoom lens is a biconcave lens with negative optical power; The first compensation lens of the compensation lens group is a meniscus lens with positive optical power, with its convex surface facing the image side, and the second compensation lens is a biconvex lens with positive optical power; The second fixed lens is a meniscus lens with negative optical power, with its convex surface facing the object; The first rear fixed lens of the third fixed lens group is a meniscus lens with positive focal length, with its convex surface facing the object, and the second rear fixed lens is a meniscus lens with negative focal length, with its convex surface facing the object; The micro scanning lens is set as a biconvex positive lens with positive optical power; The first reflecting mirror and the second reflecting mirror are both plane reflecting mirrors.

2. The medium-wave infrared cooling continuous zoom transmission micro-scanning optical system according to claim 1, characterized in that The working band of the optical system is 3.7 μm to 4.8 μm, and the F number is 3.

3. The medium-wave infrared cooling continuous zoom transmission micro-scanning optical system according to claim 1, characterized in that The variable power lens and the compensation lens group are configured as lenses that move along the axial direction.

4. The medium-wave infrared cooling continuous zoom transmission micro-scanning optical system according to claim 1, characterized in that The micro scanning lens is configured to move in two orthogonal directions, horizontal and pitch, within a radial plane.

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