Compact rapid switching type four-view-field medium-wave infrared optical system

Abstract

The invention relates to a compact quick switching type four-view-field medium-wave infrared optical system, which comprises a first zoom lens group, a second zoom lens group, a focusing group and a detector which are arranged on the same optical axis, the first zoom lens group and the second zoom lens group are respectively connected with a rotating hub; the first zoom lens group and the second zoom lens group respectively comprise various lenses for changing the magnification, and the focusing group comprises various lenses for adjusting the focal length; the first zoom lens group and the second zoom lens group are cut in / out of the optical axis by controlling the rotation of the rotating hubs respectively, and light passes through any 0-2 of the first zoom lens group and the second zoom lens group and then passes through the focusing group to enter the detector; through double-rotating-hub switching, the optical system can have four focal lengths, switching of the four-view-field optical system is achieved, view field switching is carried out in a rotating hub mode, the view field switching time is shorter than one second, the switching time is short, and the needed focal length can be rapidly switched.

Description

Technical Field

[0001] The invention relates to the field of optical technology, and in particular to a compact fast-switching four-field-of-view medium-wave infrared optical system. Background Art

[0002] In the application field of infrared thermal imaging, it is usually required that the infrared optical system has the function of switching between large and small fields of view; the optical system can complete the functions of target recognition, aiming and tracking by switching between a large field of view with low magnification and a small field of view with high magnification. The optical system adopts a dual field of view or multi-field of view design to make the optical system have more applications. When the focal length is small, the field of view angle is relatively large, which makes it easy to find the target; when the focal length is large, the field of view angle is relatively small, and the view is farther, and the details of the distant target can be seen clearly. When the focal length magnification ratio between the large and small fields of view is relatively large, adding a transition field of view between the two fields of view can more accurately identify and track target objects of different sizes.

[0003] Currently, there are two ways to achieve field of view switching in infrared optical systems: axial magnification and hub cutting in and out. The axial magnification system uses the relative position movement of the magnification lens group and the compensation lens group to achieve field of view change. Its working principle is the same as that of the continuous magnification optical system. During the installation and adjustment process, the consistency of the optical axis must be taken into consideration, which will increase the difficulty of system installation and adjustment, and the field of view switching time is long.

[0004] In the technical solution disclosed in the Chinese invention patent application entitled "Large-ratio medium-wave infrared optical system with secondary mirror switching and thermal aperture changing F-number (publication number: CN115857151A)", switching of four fields of view is achieved by switching in and out of four modules: short-focus front group, medium-focus front group, common rear group and thermal aperture rear group. Not only is the structure complex and bulky, and the operation is troublesome, but the F-numbers of each field of view are different. The F-number of the ultra-telephoto field of view is 7, and it needs to be replaced with an F7 detector that is not commonly used on the market for collection. Summary of the invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a compact, fast-switching four-field-of-view medium-wave infrared optical system. Through dual-hub switching, the optical system can have four focal lengths, thereby realizing the conversion of the four-field-of-view optical system. The field-of-view switching is performed by a hub method. The field-of-view switching time is less than one second, the switching time is fast, and the desired focal length can be quickly switched.

[0006] According to a first aspect of the present invention, there is provided a compact fast-switching four-field-of-view medium-wave infrared optical system, comprising: a first zoom lens group, a second zoom lens group, a focus adjustment group and a detector on the same optical axis; the first zoom lens group and the second zoom lens group are respectively connected to a rotating hub; The first zoom lens group and the second zoom lens group respectively include various lenses for changing the magnification, and the focus adjustment group includes various lenses for adjusting the focal length; The first zoom lens group and the second zoom lens group are made to cut into / out of the optical axis by controlling the rotation of each hub respectively. After the light passes through any 0-2 of the first zoom lens group and the second zoom lens group, it passes through the focusing group and enters the detector, thereby realizing the conversion of the four-field optical system with four focal lengths of the optical system.

[0007] Based on the above technical solution, the present invention can also make the following improvements.

[0008] Optionally, the optical system further comprises: a front fixing group disposed before the first zoom lens group; The front fixed group includes: a first lens, a second lens and a third lens arranged in sequence from the object side to the image plane along the optical axis of the lens; The first lens is a positive meniscus lens, the second lens is a negative meniscus lens, and the third lens is a positive meniscus lens; The focal length of the first lens satisfies: 短 <f 1 <f 长 ; where f 短 is the shortest focal length of the system; f 长 is the focal length of the longest focal length of the system; f 1 is the focal length of the first lens; The first surface of the second lens is a diffractive surface, and the second surface of the third lens 3 is an aspherical surface.

[0009] Optionally, the first lens 1 is made of silicon, and the second lens 2 and the third lens 3 are made of germanium.

[0010] Optionally, the optical system further comprises: a first reflector and a second reflector arranged up and down, wherein the reflective surfaces of the first reflector and the second reflector are opposite to each other and both have an angle of 45° with the horizontal line; The light passing through the front fixed group and the first zoom lens group in the horizontal direction is then reflected by the first reflector and output downward to enter the second zoom lens group, and then reflected by the second reflector to become horizontal before entering the focusing group and the detector.

[0011] Optionally, the first zoom lens group includes: a fourth lens, a fifth lens and a sixth lens; The fourth lens is a meniscus negative lens, the fifth lens is a meniscus positive lens, and the sixth lens is a biconvex positive lens; The first surface of the fourth lens is an aspherical surface, and the second surface of the fifth lens is an aspherical surface.

[0012] Optionally, the fourth lens 4, the fifth lens and the sixth lens are all made of germanium.

[0013] Optionally, the second zoom lens group includes: a seventh lens and an eighth lens; The seventh lens is a meniscus positive lens, and the eighth lens is a meniscus positive lens; The first surface of the eighth lens is aspherical.

[0014] Optionally, the material of the seventh lens is zinc selenide, and the material of the eighth lens is germanium.

[0015] Optionally, the focusing group includes a ninth lens, a tenth lens and an eleventh lens; The ninth lens is a positive meniscus lens, the tenth lens is a negative meniscus lens, and the eleventh lens is a positive meniscus lens; The first surface of the ninth lens is an aspherical surface; the second surface of the tenth lens is an aspherical surface.

[0016] Optionally, the ninth lens is made of silicon, and the tenth lens and the eleventh lens are made of different types of germanium.

[0017] The present invention provides a compact fast-switching four-field-of-view medium-wave infrared optical system, which has the following beneficial effects: The use of two sets of lenses for cutting in and out allows the optical system to have four focal lengths. Clear imaging can be achieved in any combination of the cutting in and out arrangements of the two sets of lenses, so that all four fields of view can have good imaging quality. By controlling the rotating hub lens, free switching from any field of view to any field of view can be achieved. The one-piece structure is simple to manufacture and has high stability, high lens utilization rate and small system size.

[0018] The system has the characteristics of small F number and large aperture. It can match the cooled detectors of F3.0 and F4.0, with the image plane not larger than 12.3mm and the pixel size not less than 15um. The F3.0 optical system will collect more energy and observe tiny objects more clearly. It is also compatible with the F4.0 medium-wave optical detector.

[0019] A secondary imaging design is adopted, in which the focusing group lens is set behind the primary image plane. The movement of the focusing group can better compensate for the effects of working distance and high and low temperatures on the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A schematic structural diagram of an embodiment of a compact fast-switching four-field-of-view medium-wave infrared optical system provided by the present invention at a focal length of 120 mm; Figure 2A schematic structural diagram of an embodiment of a compact fast-switching four-field-of-view medium-wave infrared optical system provided by the present invention at a focal length of 240 mm; Figure 3 A schematic structural diagram of an embodiment of a compact fast-switching four-field-of-view medium-wave infrared optical system provided by the present invention at a focal length of 360 mm; Figure 4 A schematic structural diagram of an embodiment of a compact fast-switching four-field-of-view medium-wave infrared optical system provided by the present invention at a focal length of 480 mm; Figure 5 A schematic diagram of the MTF of an optical system provided by the present invention when the optical system is in a working state of 120mm focal length; Figure 6 A schematic diagram of the MTF of an optical system provided by the present invention when the optical system is in a working state of 240mm focal length; Figure 7 A schematic diagram of the MTF of an optical system provided by the present invention when the optical system is in a working state of 360mm focal length; Figure 8 A schematic diagram of the MTF of an optical system provided by the present invention when the optical system is in a working state of 480mm focal length; In the accompanying drawings, the components represented by the reference numerals are listed as follows: 1-first lens, 2-second lens, 3-third lens, 4-fourth lens, 5-fifth lens, 6-sixth lens, 7-first reflector, 8-seventh lens, 9-eighth lens, 10-second reflector, 11-ninth lens, 12-tenth lens, 13-eleventh lens, 14-window, 15-aperture, 16-detector. DETAILED DESCRIPTION

[0021] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0022] Figure 1 A schematic diagram of the structure of an embodiment of a compact fast-switching four-field-of-view medium-wave infrared optical system provided by the present invention at a focal length of 120 mm, combined with Figure 1 It can be seen that the optical system includes: a first zoom lens group, a second zoom lens group, a focus adjustment group and a detector 16 on the same optical axis; the first zoom lens group and the second zoom lens group are respectively connected to a rotating hub.

[0023] The first variator lens group and the second variator lens group respectively include various lenses for changing the magnification, and the focus adjustment group includes various lenses for adjusting the focal length.

[0024] By controlling the rotation of each hub respectively, the first zoom lens group and the second zoom lens group are cut into / out of the optical axis. After the light passes through any 0-2 of the first zoom lens group and the second zoom lens group, it passes through the focusing group and enters the detector 16, thereby realizing the conversion of the four-field optical system with four focal lengths of the optical system.

[0025] The present invention provides a compact fast-switching four-field-of-view medium-wave infrared optical system, which adopts two groups of lenses for cutting in and out so that the optical system can have four focal lengths, and any combination of the cut-in and cut-out arrangements of the two groups of lenses can form clear images, so that the four fields of view can have good imaging quality, and switching from any field of view to any field of view can be achieved. The integrated structure is simple to manufacture and has high stability, high lens utilization rate and small system size; the system has the characteristics of small F number and large aperture, and can match F3.0 and F4.0 refrigerated detectors; a secondary imaging design is adopted, in which a focusing group lens is arranged behind a primary image plane, and the movement of the focusing group can better compensate for the influence of working distance and high and low temperatures on the system.

[0026] Example 1 Embodiment 1 provided by the present invention is an embodiment of a compact fast-switching four-field-of-view medium-wave infrared optical system provided by the present invention. Figure 1-Figure 4 The schematic diagrams of the structures of the embodiments of a compact fast-switching four-field-of-view medium-wave infrared optical system provided by the present invention at focal lengths of 120mm, 240mm, 360mm and 480mm, respectively, are combined with Figure 1-Figure 4 It can be seen that the embodiment of the optical system includes: The front fixed group, the first magnification lens group, the second magnification lens group, the focusing group and the detector 16 are on the same optical axis; the first magnification lens group and the second magnification lens group are respectively connected to a rotating hub.

[0027] In a possible implementation manner, the front fixed group includes: a first lens 1, a second lens 2, and a third lens 3 which are sequentially arranged along the optical axis of the lens from the object side to the image plane.

[0028] The first lens 1 is a positive meniscus lens, the second lens 2 is a negative meniscus lens, and the third lens 3 is a positive meniscus lens.

[0029] The focal length of the first lens 1 satisfies: f 短 <f 1 <f 长 ; where f 短 is the shortest focal length of the system; f 长 is the focal length of the longest focal length of the system; f 1 is the focal length of the first lens.

[0030] The first surface of the second lens 1 is a diffraction surface, and the second surface of the third lens 3 is an aspheric surface. The first surface is the surface where light is incident, and the second surface is the surface where light is emitted.

[0031] In a possible embodiment, the material of the first lens 1 is silicon, and the materials of the second lens 2 and the third lens 3 are germanium. The combination of silicon material and germanium material in the front fixed group is very helpful in eliminating the chromatic aberration of the system.

[0032] The first variator lens group and the second variator lens group respectively include various lenses for changing the magnification, and the focus adjustment group includes various lenses for adjusting the focal length.

[0033] By controlling the rotation of each hub respectively, the first zoom lens group and the second zoom lens group are cut into / out of the optical axis. After the light passes through any 0-2 of the first zoom lens group and the second zoom lens group, it passes through the focusing group and enters the detector 16, thereby realizing the conversion of the four-field optical system with four focal lengths of the optical system.

[0034] In a possible embodiment, the optical system further includes: a first reflector 7, a second reflector 10, a window 14 and an aperture 15, wherein the upper and lower reflective surfaces of the first reflector 7 and the second reflector 10 are opposite to each other and both have an angle of 45° with the horizontal line.

[0035] The light passing through the horizontal front fixed group and the first zoom lens group is then reflected by the first reflector 7 and output downward to enter the second zoom lens group, and then reflected by the second reflector 10 to become horizontal before entering the focusing group, window 14, aperture 15 and detector 16.

[0036] After the light is incident through the front fixed group, it passes through the first zoom lens group and is reflected by the first reflector. The light passes through the second zoom lens group and is reflected by the second reflector. After the light passes through the focusing group, it enters the detector 16, which can further make the rhythm of the entire system more compact.

[0037] In a possible implementation manner, the first zoom lens group includes: a fourth lens 4 , a fifth lens 5 and a sixth lens 6 .

[0038] The fourth lens 4 is a meniscus negative lens, the fifth lens 5 is a meniscus positive lens, and the sixth lens 6 is a double convex positive lens.

[0039] The first surface of the fourth lens 4 is an aspherical surface, and the second surface of the fifth lens 5 is an aspherical surface.

[0040] In a possible embodiment, the fourth lens 4, the fifth lens 5 and the sixth lens 6 are all made of germanium. The refractive index of the germanium material can eliminate most of the spherical aberration.

[0041] In a possible implementation manner, the second zoom lens group includes: a seventh lens 8 and an eighth lens 9 .

[0042] The seventh lens 8 is a positive meniscus lens, and the eighth lens 9 is a positive meniscus lens.

[0043] The first surface of the eighth lens 9 is aspherical.

[0044] In a possible implementation manner, the material of the seventh lens 8 is zinc selenide, and the material of the eighth lens 9 is germanium.

[0045] In a possible implementation manner, the focusing group includes a ninth lens 11 , a tenth lens 12 , and an eleventh lens 13 .

[0046] The ninth lens 11 is a positive meniscus lens, the tenth lens 12 is a negative meniscus lens, and the eleventh lens 13 is a positive meniscus lens.

[0047] The first surface of the ninth lens 11 is an aspherical surface; the second surface of the tenth lens 12 is an aspherical surface.

[0048] In a possible implementation manner, the ninth lens 11 is made of silicon, and the tenth lens 12 and the eleventh lens 13 are made of different types of germanium. This material combination can effectively correct the distortion of the optical system.

[0049] Specific, combined Figure 1-Figure 4 It can be seen that when the lenses of the first magnification lens group are in the cut-in state and the second magnification lens group is in the cut-in state, the focal length of the optical system is 120m; when the lenses of the first magnification lens group are in the cut-in state and the second magnification lens group is in the cut-in state, the focal length of the optical system is 240mm; when the lenses of the first magnification lens group are in the cut-in state and the second magnification lens group is in the cut-in state, the focal length of the optical system is 360mm; when the lenses of the first magnification lens group are in the cut-in state and the second magnification lens group is in the cut-in state, the focal length of the optical system is 480mm.

[0050] like Figure 5-8 The figures are schematic diagrams of the system MTF (modulation transfer function) of an optical system provided by the present invention when the focal lengths are 120 mm, 240 mm, 360 mm and 480 mm, respectively. Figure 5-Figure 8The given complex light diffraction MTF, the fast switching four-field medium-wave cooled infrared imaging system of the present invention, the full-field MTF of the optical system at the detector cutoff frequency when the focal length is 120 mm is greater than 0.25, the full-field MTF of the optical system at the detector cutoff frequency when the focal length is 240 mm is greater than 0.3, the full-field MTF of the optical system at the detector cutoff frequency when the focal length is 360 mm is greater than 0.3, and the full-field MTF of the optical system at the detector cutoff frequency when the focal length is 480 mm is greater than 0.3.

[0051] It can also be seen that the light in the central field of view is close to the diffraction limit and the edge field of view also has a high transfer function, which can ensure good imaging quality.

[0052] The technical indicators achieved by an optical system provided by an embodiment of the present invention are as follows: Focal length 120mm / 240mm / 360mm / 480mm; F / #:3.0; Detector: 640 512; pixel size: 15μm; total optical length: 615mm; applicable spectral range: 3.7~4.8μm; distortion less than 3%.

[0053] The embodiment of the present invention provides a compact, fast-switching, four-field-of-view medium-wave infrared optical system, which adopts two groups of lenses for cutting in and out so that the optical system can have four focal lengths. Any combination of the cutting-in and cutting-out arrangements of the two groups of lenses can produce clear images, so that the four fields of view can have good imaging quality. By controlling the rotating hub lens, it is possible to switch freely from any field of view to any field of view. The integrated structure is simple to manufacture and has high stability, high lens utilization and a small system size.

[0054] The system has the characteristics of small F number and large aperture. It can match the cooled detectors of F3.0 and F4.0, with the image plane not larger than 12.3mm and the pixel size not less than 15um. The F3.0 optical system will collect more energy and observe tiny objects more clearly. It is also compatible with the F4.0 medium-wave optical detector.

[0055] A secondary imaging design is adopted, in which the focusing group lens is set behind the primary image plane. The movement of the focusing group can better compensate for the effects of working distance and high and low temperatures on the system.

[0056] It should be noted that in the above embodiments, the description of each embodiment has its own emphasis, and for parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0057] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0058] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0059] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0060] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the computer or other programmable device. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0061] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0062] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A compact, fast-switching four-field-of-view medium-wave infrared optical system, characterized in that: The optical system comprises: a first zoom lens group, a second zoom lens group, a focus adjustment group and a detector on the same optical axis; the first zoom lens group and the second zoom lens group are respectively connected to a rotating hub; The first zoom lens group and the second zoom lens group respectively include various lenses for changing the magnification, and the focus adjustment group includes various lenses for adjusting the focal length; The first zoom lens group and the second zoom lens group are made to cut into / out of the optical axis by controlling the rotation of each hub respectively. After the light passes through any 0-2 of the first zoom lens group and the second zoom lens group, it passes through the focusing group and enters the detector, thereby realizing the conversion of the four-field optical system with four focal lengths of the optical system.

2. The optical system according to claim 1, characterized in that The optical system further comprises: a front fixing group arranged in front of the first zoom lens group; The front fixed group includes: a first lens, a second lens and a third lens arranged in sequence from the object side to the image plane along the optical axis of the lens; The first lens is a positive meniscus lens, the second lens is a negative meniscus lens, and the third lens is a positive meniscus lens; The focal length of the first lens satisfies: 短 <f1<f 长 ; Among them, f 短 is the shortest focal length of the system; f 长 is the focal length of the longest focal length of the system; f1 is the focal length of the first lens; The first surface of the second lens is a diffractive surface, and the second surface of the third lens is an aspherical surface.

3. The optical system according to claim 2, characterized in that The material of the first lens is silicon, and the materials of the second lens and the third lens are germanium.

4. The optical system according to claim 2, characterized in that The optical system further comprises: a first reflector and a second reflector arranged up and down, wherein the reflective surfaces of the first reflector and the second reflector are opposite to each other and the angle between the first reflector and the second reflector and the horizontal line are both 45°; The light passing through the front fixed group and the first zoom lens group in the horizontal direction is then reflected by the first reflector and output downward to enter the second zoom lens group, and then reflected by the second reflector to become horizontal before entering the focusing group and the detector.

5. The optical system according to claim 1, characterized in that The first zoom lens group includes: a fourth lens, a fifth lens and a sixth lens; The fourth lens is a meniscus negative lens, the fifth lens is a meniscus positive lens, and the sixth lens is a biconvex positive lens; The first surface of the fourth lens is an aspherical surface, and the second surface of the fifth lens is an aspherical surface.

6. The optical system according to claim 1, characterized in that The fourth lens, the fifth lens and the sixth lens are all made of germanium.

7. The optical system according to claim 1, characterized in that The second zoom lens group includes: a seventh lens and an eighth lens; The seventh lens is a meniscus positive lens, and the eighth lens is a meniscus positive lens; The first surface of the eighth lens is aspherical.

8. The optical system according to claim 7, characterized in that The material of the seventh lens is zinc selenide, and the material of the eighth lens is germanium.

9. The optical system according to claim 1, characterized in that The focusing group includes a ninth lens, a tenth lens and an eleventh lens; The ninth lens is a positive meniscus lens, the tenth lens is a negative meniscus lens, and the eleventh lens is a positive meniscus lens; The first surface of the ninth lens is an aspherical surface; the second surface of the tenth lens is an aspherical surface.

10. The optical system according to claim 9, characterized in that The ninth lens is made of silicon, and the tenth lens and the eleventh lens are made of different types of germanium.

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