Large-zoom-ratio compact medium-wave infrared continuous zooming optical system

Abstract

The invention relates to a compact medium-wave infrared continuous zooming optical system with a large zoom ratio, which realizes continuous zooming with a focal length of 22-690mm, and comprises a front fixed group, a zoom group, a compensation group, a rear fixed group, a reflector group and a secondary imaging group which are sequentially arranged from the infinity of an object space to a focal plane of an image space, the front fixed group is sequentially provided with a positive meniscus lens A and a negative meniscus lens A from an object side to an image side; the zoom group is a biconcave negative lens B; the compensation group is a biconvex positive lens C; the rear fixing group is a biconcave negative lens D; the reflector group is sequentially provided with a first reflector E, a second reflector E and a third reflector E from the object space to the image space; and the secondary imaging group is sequentially provided with a positive meniscus lens F, a negative meniscus lens F and a biconvex positive lens F from the object side to the image side. The optical system is reasonable in design, has the advantages of high zoom ratio, high resolution, small optical axis drift distance, long detection distance, good imaging effect, compact structure and the like, and meets smooth zoom group and compensation group curves in a full-focus section.

Description

Technical Field

[0001] The invention relates to a compact medium-wave infrared continuous zoom optical system with a large zoom ratio. Background Art

[0002] With the development of infrared technology, continuous zoom infrared optical systems have been widely used in military and civilian fields. The continuous zoom infrared system can change the relative positions of two or more groups of lenses so that the system has a stable image plane and clear imaging during the continuous change of focal length, and it is not easy to lose the target during target search and tracking. There are already large zoom ratio medium-wave infrared continuous zoom optical systems in China, but the zoom ratio exceeds 30 times. In order to obtain a larger field of view and a higher zoom ratio, higher requirements are placed on the optical design. Therefore, it is the research purpose of this invention to develop a 22-690mm large zoom ratio compact medium-wave infrared continuous zoom optical system to overcome the above-mentioned defects. Summary of the invention

[0003] The object of the present invention is to provide a compact medium-wave infrared continuous zoom optical system with a large zoom ratio.

[0004] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a compact medium-wave infrared continuous zoom optical system with a large zoom ratio, a focal length of 22 to 690 mm continuous zoom, the optical system includes a front fixed group, a zoom group, a compensation group, a rear fixed group, a reflector group and a secondary imaging group which are arranged in sequence from the object side to the image side focal plane, the front fixed group is provided with a positive meniscus lens A and a negative meniscus lens A in sequence from the object side to the image side; the zoom group is a double concave negative lens B; the compensation group is a double convex positive lens C; the rear fixed group is a double concave negative lens D; the reflector group is provided with a first reflector E, a second reflector E and a third reflector E in sequence from the object side to the image side; the secondary imaging group is provided with a positive meniscus lens F, a negative meniscus lens F and a double convex positive lens F in sequence from the object side to the image side.

[0005] Furthermore, the air gap between the front fixed group and the zoom group is 18.5-112.9 mm; the air gap between the zoom group and the compensation group is 25.6-162.7 mm; the air gap between the compensation group and the rear fixed group is 7.7-50.4 mm; the air gap between the rear fixed group and the reflector group is 15.1 mm; and the air gap between the reflector group and the secondary imaging group is 13.4 mm.

[0006] Further, in the front fixed group, the air gap between the positive meniscus lens A and the negative meniscus lens A is 15.2 mm.

[0007] Further, in the reflector group, the air gap between the first reflector E and the second reflector E is 36 mm, and the air gap between the second reflector E and the third reflector E is 85 mm.

[0008] Further, in the secondary imaging group, the air space between the positive meniscus lens F and the negative meniscus lens F is 6 mm; the air space between the negative meniscus lens F and the biconvex positive lens F is 8.7 mm.

[0009] Furthermore, the positive meniscus lens A is made of silicon material, the negative meniscus lens A is made of germanium material; the zoom group is made of germanium material; the compensation group is made of silicon material; the rear fixed group is made of germanium material; the first reflector E, the second reflector E and the third reflector E are all made of H-K9L material; the positive meniscus lens F is made of silicon material, the negative meniscus lens F is made of germanium material, and the double convex positive lens F is made of silicon material.

[0010] Furthermore, the optical surfaces of the lenses in the front fixed group, the zoom group, the compensation group, the rear fixed group, and the secondary imaging group are coated with an anti-reflection film, and the optical surfaces of the lenses in the reflector group are coated with a high-reflection film.

[0011] Furthermore, the object side surface of the positive meniscus lens A, the image side surface of the zoom group, the object side surface and image side surface of the compensation group, the object side surface of the positive meniscus lens F, and the object side surface of the negative meniscus lens F are all high-order aspheric surfaces.

[0012] Furthermore, the rear fixing group can move along the optical axis within a range of -2.2 / +1.6 mm, wherein the direction away from the positive meniscus lens A is negative and the direction close to the positive meniscus lens A is positive.

[0013] Compared with the prior art, the present invention has the following effects: the present invention is reasonably designed, has the advantages of high zoom ratio, high resolution, small optical axis drift, long detection distance, good imaging effect, compact structure, etc., and satisfies smooth zoom group and compensation group curves within the full focal length. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the structure of an embodiment of the present invention; Figure 2 is a telephoto MTF (modulation transfer function) diagram of an embodiment of the present invention; Figure 3 is a short-focus MTF diagram of an embodiment of the present invention; Figure 4 is a telephoto field curvature distortion diagram of an embodiment of the present invention; Figure 5 4 is a short focal field curvature distortion diagram of an embodiment of the present invention.

[0015] In the figure: 1-front fixed group; 101-positive meniscus lens A; 102-negative meniscus lens A; 2-zooming group; 201-double concave negative lens B; 3-compensation group; 301-double convex positive lens C; 4-rear fixed group; 401-double concave negative lens D; 5-reflector group; 501-first reflector E; 502-second reflector E; 503-third reflector E; 6-secondary imaging group; 601-positive meniscus lens F; 602-negative meniscus lens F; 603-double convex positive lens F; 7-focal plane. DETAILED DESCRIPTION

[0016] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0017] In the description of the present invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0018] like Figure 1 As shown, the present invention is a compact medium-wave infrared continuous zoom optical system with a larger zoom ratio and a compact structure, with a focal length of 22 to 690 mm and continuous zoom. The optical system includes a front fixed group 1, a zoom group 2, a compensation group 3, a rear fixed group 4, a reflector group 5 and a secondary imaging group 6, which are arranged in sequence from the object side to the image side focal plane. The front fixed group 1 is provided with a positive meniscus lens A101 and a negative meniscus lens A102 in sequence from the object side to the image side; the zoom group 2 is a double concave negative lens B201; the compensation group 3 is a double convex positive lens C301; the rear fixed group 4 is a double concave negative lens D401; the reflector group 5 is provided with a first reflector E501, a second reflector E502 and a third reflector E503 in sequence from the object side to the image side, the first reflector E, the second reflector E and the third reflector E are all plane reflection mechanisms, and the light path is folded by three plane reflectors to compress the system volume, so that the system structure is compact; the secondary imaging group 6 is provided with a positive meniscus lens F601, a negative meniscus lens F602 and a double convex positive lens F603 in sequence from the object side to the image side.

[0019] The optical system has the advantages of high zoom ratio, high resolution, small optical axis drift, long detection distance, good imaging effect, compact structure, etc. It also meets the smooth zoom group and compensation group curves within the full focal length. It can be adapted to the cooled medium-wave infrared detector with a pixel number of 640×512 and a pixel size of 15μm to perform real-time large-field-of-view target search, small-field-of-view target tracking and measurement tasks.

[0020] In this embodiment, the air gap between the front fixed group 1 and the zoom group 2 is 18.5-112.9 mm; the air gap between the zoom group 2 and the compensation group 3 is 25.6-162.7 mm; the air gap between the compensation group 3 and the rear fixed group 4 is 7.7-50.4 mm; the air gap between the rear fixed group 4 and the reflector group 5 is 15.1 mm; and the air gap between the reflector group 5 and the secondary imaging group 6 is 13.4 mm.

[0021] In this embodiment, in the front fixed group 1, the air gap between the positive meniscus lens A101 and the negative meniscus lens A102 is 15.2 mm.

[0022] In this embodiment, in the reflector group 5, the air gap between the first reflector E501 and the second reflector E502 is 36 mm, and the air gap between the second reflector E502 and the third reflector E503 is 85 mm.

[0023] In this embodiment, in the secondary imaging group 6, the air space between the positive meniscus lens F601 and the negative meniscus lens F602 is 6 mm; the air space between the negative meniscus lens F602 and the double convex positive lens F603 is 8.7 mm.

[0024] In this embodiment, the positive meniscus lens A is made of silicon material, the negative meniscus lens A is made of germanium material; the zoom group is made of germanium material; the compensation group is made of silicon material; the rear fixed group is made of germanium material; the first reflector E, the second reflector E and the third reflector E are all made of H-K9L material; the positive meniscus lens F is made of silicon material, the negative meniscus lens F is made of germanium material, and the double convex positive lens F is made of silicon material.

[0025] In this embodiment, the optical surfaces of the lenses in the front fixed group, the zoom group, the compensation group, the rear fixed group, and the secondary imaging group are all coated with anti-reflection films, and the optical surfaces of the lenses in the reflector group are all coated with high-reflection films.

[0026] In this embodiment, the object side surface of the positive meniscus lens A, the image side surface of the zoom group, the object side surface and image side surface of the compensation group, the object side surface of the positive meniscus lens F, and the object side surface of the negative meniscus lens F are all high-order aspheric surfaces.

[0027] In this embodiment, the rear fixing group can move along the optical axis, and the moving range is: -2.2 / +1.6mm, where the direction away from the positive meniscus lens A is negative, and the direction close to the positive meniscus lens A is positive. In the optical design, in order to ensure the use requirements of the lens in high and low temperature environments, temperature compensation and near and far distance compensation are achieved by moving the rear fixing group 4.

[0028] In this embodiment, the optical element parameters of the positive meniscus lens A, the negative meniscus lens A, the biconcave negative lens B, the biconvex positive lens C, the biconcave negative lens D, the positive meniscus lens F, the negative meniscus lens F and the biconvex positive lens F are as follows. Among them, surface numbers 1 and 2 are respectively the object side and image side of the positive meniscus lens A, surface numbers 3 and 4 are respectively the object side and image side of the negative meniscus lens A, surface numbers 5 and 6 are respectively the object side and image side of the biconcave negative lens B, surface numbers 7 and 8 are respectively the object side and image side of the biconvex positive lens C, surface numbers 9 and 10 are respectively the object side and image side of the biconcave negative lens D, surface numbers 11 and 12 are respectively the object side and image side of the positive meniscus lens F, surface numbers 13 and 14 are respectively the object side and image side of the negative meniscus lens F, and surface numbers 15 and 16 are respectively the object side and image side of the biconvex positive lens F.

[0029] In this embodiment, the aspheric expression is: Aspheric surface related data: .

[0030] In this embodiment, the optical system composed of the above-mentioned lens group achieves the following optical indicators: (1) working band: 3.7μm~4.8μm; (2) focal length f′: 22~690mm; (3) detector: medium-wave infrared cooling type 640×512, 15μm; (4) field of view: 24.6°×19.8°~0.8°×0.64°; (5) relative aperture D / f′: 1 / 5.5; (6) optical volume: 269mm×130mm×165mm (length×width×height).

[0031] In this embodiment, the optical design software is used to reasonably set variables and optimization functions to optimize the initial structure. Figure 1 The figure shows the optical path structure of the optical system, which realizes continuous zoom by using the negative zoom group and positive compensation group in the form of single zoom group and single compensation group. The medium-wave continuous zoom optical system consists of eight lenses and three plane reflectors. The front fixed group consists of a silicon positive lens and an aspheric germanium lens, which are used to collect the light entering the optical system; the zoom group is an aspheric silicon lens with negative optical power, which can continuously change the focal length of the optical system; the compensation group is an aspheric silicon lens with positive optical power, which is used to eliminate chromatic aberration and compensate for the aberration generated in zooming, ensuring that the image plane position does not move during the continuous zooming process; the rear fixed group is a germanium lens, and the secondary imaging system consists of an aspheric silicon lens, an aspheric germanium lens and a silicon lens. The three reflectors are located between the rear fixed group and the secondary imaging group.

[0032] In this embodiment, in the optical design, in order to ensure clear imaging at each focal length under continuous zoom, 5 high-order aspheric surfaces are introduced simultaneously in the optical design, which helps to balance the system aberration and provide more degrees of freedom for the optical design optimization process. By optimizing the YNI value of the cold reflection "black spot" sensitive surface under short focal length, the cold reflection "black spot" is kept away from the imaging surface; by optimizing the cam curve design, the optical axis drift during zooming is ensured to be small, and the imaging quality is excellent within the full focal length range. In order to ensure the use requirements of the lens in high and low temperature environments, the movable rear fixed group can realize temperature compensation and far and near distance compensation, and the moving range is: -2.2 / +1.6mm; away from the first lens (positive meniscus lens A) is negative, and close to the first lens (positive meniscus lens A) is positive. Three plane reflectors are used to fold the optical path and compress the system volume, making the system structure compact, with a volume of 269mm (length) × 130mm (width) × 165mm (height) and a weight of 795g.

[0033] In this embodiment, Figure 2 , 3 , 4, and 5, it can be seen that the optical system has good imaging quality in both the long-focus and short-focus ranges.

[0034] The advantages of the present invention are: (1) In the optical design, in order to make the optical system have the advantages of high zoom ratio, high resolution, small optical axis drift, long detection distance, good imaging effect and compact structure, the optical power of each lens group is reasonably allocated. In the zoom group 2, compensation group 3, rear fixed group 4 and secondary imaging group 6, a total of five even-order aspheric corrections are introduced to balance the system aberrations; (2) In the optical design, in order to ensure the use requirements of the lens in high and low temperature environments, temperature compensation and near and far distance compensation are achieved by moving the rear fixed group 4, and the movement range is: -2.2 / +1.6mm; (3) In optical design, by optimizing and controlling the YNI values ​​of each short-focus surface, the specular reflection "ghost image" and cold reflection "black spot" are kept away from the detector image plane; (4) Excellent imaging quality over the entire focal length range; (5) Three plane mirrors are used to fold the optical path, compress the system volume, and make the system structure compact.

[0035] If the present invention discloses or involves components or structures that are fixedly connected to each other, then, unless otherwise stated, the fixed connection can be understood as: a detachable fixed connection (for example, connection using bolts or screws), and can also be understood as: a non-detachable fixed connection (for example, riveting, welding). Of course, the mutual fixed connection can also be replaced by an integrated structure (for example, manufactured by one-piece molding using a casting process) (except when it is obviously impossible to use an one-piece molding process).

[0036] In addition, unless otherwise stated, the terms used to indicate positional relationships or shapes in any of the technical solutions disclosed in the present invention include states or shapes that are approximate, similar, or close to them.

[0037] Any component provided by the present invention may be assembled from a plurality of separate components, or may be a separate component manufactured by an integral forming process.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or some technical features can be replaced by equivalents without departing from the spirit of the technical solution of the present invention, which should be included in the scope of the technical solution for protection of the present invention.

Claims

1. A compact medium-wave infrared continuous zoom optical system with a large zoom ratio, with a focal length of 22 to 690 mm, characterized by: The optical system comprises a front fixed group, a zoom group, a compensation group, a rear fixed group, a reflector group and a secondary imaging group which are arranged in sequence from the object side to the image side focal plane, wherein the front fixed group is provided with a positive meniscus lens A and a negative meniscus lens A in sequence from the object side to the image side; the zoom group is a double concave negative lens B; the compensation group is a double convex positive lens C; the rear fixed group is a double concave negative lens D; the reflector group is provided with a first reflector E, a second reflector E and a third reflector E in sequence from the object side to the image side; the secondary imaging group is provided with a positive meniscus lens F, a negative meniscus lens F and a double convex positive lens F in sequence from the object side to the image side.

2. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: The air space between the front fixed group and the zoom group is 18.5-112.9 mm; the air space between the zoom group and the compensation group is 25.6-162.7 mm; the air space between the compensation group and the rear fixed group is 7.7-50.4 mm; the air space between the rear fixed group and the reflector group is 15.1 mm; and the air space between the reflector group and the secondary imaging group is 13.4 mm.

3. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: In the front fixed group, the air space between the positive meniscus lens A and the negative meniscus lens A is 15.2 mm.

4. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: In the reflector group, the air interval between the first reflector E and the second reflector E is 36 mm, and the air interval between the second reflector E and the third reflector E is 85 mm.

5. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: In the secondary imaging group, the air space between the positive meniscus lens F and the negative meniscus lens F is 6 mm; the air space between the negative meniscus lens F and the biconvex positive lens F is 8.7 mm.

6. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: The positive meniscus lens A is made of silicon material, the negative meniscus lens A is made of germanium material; the zoom group is made of germanium material; the compensation group is made of silicon material; the rear fixed group is made of germanium material; the first reflector E, the second reflector E and the third reflector E are all made of H-K9L material; the positive meniscus lens F is made of silicon material, the negative meniscus lens F is made of germanium material, and the double convex positive lens F is made of silicon material.

7. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: The optical surfaces of the lenses in the front fixed group, the zoom group, the compensation group, the rear fixed group and the secondary imaging group are all coated with anti-reflection films, and the optical surfaces of the lenses in the reflector group are all coated with high-reflection films.

8. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: The object side surface of the positive meniscus lens A, the image side surface of the zoom group, the object side surface and image side surface of the compensation group, the object side surface of the positive meniscus lens F, and the object side surface of the negative meniscus lens F are all high-order aspherical surfaces.

9. The compact medium-wave infrared continuous zoom optical system with a large zoom ratio according to claim 1, characterized in that: The rear fixing group can move along the optical axis, and the moving range is: -2.2 / +1.6mm, wherein the direction away from the positive meniscus lens A is negative, and the direction close to the positive meniscus lens A is positive.

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