Two-stage zoom large-target low-light optical system with variable aperture diaphragm position

Abstract

The present invention discloses a two-stage zoom large-target surface low-light optical system with variable aperture diaphragm positions. The system comprises, from object side to image side, a front fixed group with positive refractive power, a zoom group with negative refractive power, and a rear fixed group with positive refractive power. The zoom group is used for simultaneous zooming and focusing. The optical system also includes a mechanical variable diaphragm located on the rear surface of the last lens in the front fixed group. When the zoom group moves away from the front fixed group, the aperture of the mechanical variable diaphragm is reduced, and the optical system is in a telephoto position. When the zoom group moves closer to the front fixed group, the aperture of the mechanical variable diaphragm is increased, and the optical system is in a short-focus position. A virtual aperture diaphragm is formed on the front surface of the first lens in the front fixed group. The present invention has good imaging quality.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a large-target surface low-light optical system with a variable aperture diaphragm position and two-step zoom. Background Art

[0002] Low-light-level optoelectronic devices can capture target images even in low-light conditions, and offer higher resolution and clarity than infrared wavelengths. They are widely used in nighttime observation, aiming, driving, navigation, and guidance. In recent years, advances in solid-state CMOS image sensors, which can respond to illumination levels down to e-4Lux, have led to their gradual adoption in handheld devices, helmets, and other optoelectronic devices.

[0003] Since zoom optical systems can simultaneously possess the characteristics of large field of view and high resolution, they are gradually being used in low-light-level optical systems. However, since the aperture diaphragm of visible light zoom optical systems is generally located in the rear fixed group, the position of the aperture diaphragms at different focal positions remains unchanged. Direct application in low-light-level optical systems with small F# and large target areas will lead to a sharp increase in the aperture of the optical system, a longer optical length, and large off-axis field of view vignetting. Therefore, they are not suitable for individual equipment such as helmets and handheld optoelectronics that have high requirements on volume and weight. Summary of the Invention

[0004] The purpose of the present invention is to provide a large-target-surface low-light-level optical system with a two-stage zoom function and variable aperture diaphragm position. The aperture diaphragm position is set at different positions of a front fixed group at different focal positions, thereby solving the problems of large lens aperture, long optical system length, and large off-axis vignetting caused by the unchangeable aperture diaphragm position in the large-target-surface low-light-level zoom optical system, and realizing the design of a large-target-surface low-light-level zoom optical system in a smaller space.

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] A two-stage zoom large-target surface low-light optical system with variable aperture diaphragm position is provided. The system comprises, from the object side to the image side, a front fixed group with positive refractive power, a zoom group with negative refractive power, and a rear fixed group with positive refractive power. The zoom group is used for simultaneous zooming and focusing.

[0007] The optical system also includes an aperture diaphragm, the position of which changes with the focal length. When the zoom group is away from the front fixed group, the optical system is in a telephoto position, and the aperture diaphragm is located on the rear surface of the last lens of the front fixed group; when the zoom group is close to the front fixed group, the optical system is in a short focal position, and the aperture diaphragm is located on the front surface of the first lens of the front fixed group.

[0008] According to the above technical solution, when the optical system is in the telephoto position, the F# is 3; when the optical system is in the short focal position, the F# is 1.4.

[0009] Following the above technical solution, wherein:

[0010] The front fixed group includes a cemented lens 1 and a cemented lens 2; the cemented lens 1 includes a meniscus light crown lens with negative focal power and a fluorite biconvex lens with positive focal power; the cemented lens 2 includes a biconvex fluorite crown lens with positive focal power and a lanthanum flint biconcave lens with negative focal power;

[0011] The zoom group includes a zoom lens 1, a zoom lens 2, and a cemented lens 3; the zoom lens 1 is a biconvex lanthanum flint lens with positive focal power; the zoom lens 2 is a meniscus lanthanum flint lens with negative focal power; the cemented lens 3 includes a meniscus fluorine crown lens with positive focal power and a biconcave heavy flint lens with negative focal power;

[0012] The rear fixed group includes a rear fixed mirror 1, a filter and a rear fixed mirror 2; the rear fixed mirror 1 is a double convex heavy barium flint lens with positive focal length; the rear fixed mirror 2 is a meniscus lanthanum flint lens with negative focal length; the filter is flat glass.

[0013] Following the above technical solution, the working band of the optical system is 450nm~950nm, the focal length is 80mm / 120mm, and the total optical length is 123.6mm.

[0014] Following the above technical solution, the zoom group is also used to move back and forth along the optical axis to compensate for temperature and drift of the image plane of the long-wave infrared optical system during close-range imaging.

[0015] Following the above technical solution, the optical system is applied to a solid-state low-light-level CCD with a resolution of 1280×1024 and a pixel size of 12μm×12μm.

[0016] The beneficial effects of the present invention are as follows: the two-stage zoom large-target surface low-light optical system with variable aperture diaphragm position of the present invention sets the aperture diaphragm position at different positions of the front fixed group at different focal positions, thereby solving the problems of large lens aperture, long optical system length, large off-axis vignetting, etc. caused by the unchangeable aperture diaphragm position of the large-target surface zoom optical system, and realizing the design of the large-target surface low-light level zoom optical system in a smaller space. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0018] Figure 1 Schematic diagram of the structure of the two-step zoom large target surface low-light optical system with variable aperture stop position according to an embodiment of the present invention when it is in the short-focus position;

[0019] Figure 2 Schematic diagram of the structure of the two-step zoom large target surface low-light optical system with variable aperture stop position according to an embodiment of the present invention when it is at the telephoto position;

[0020] Figure 3A two-dimensional diagram of the two-stage zoom large target surface low-light optical system with variable aperture stop position according to an embodiment of the present invention when it is at a short focal position;

[0021] Figure 4 A two-dimensional diagram of the optical system of the two-step zoom large target surface low-light optical system with variable aperture stop position according to an embodiment of the present invention when the system is at a telephoto position;

[0022] Figure 5 is a transfer function diagram of the optical system of an embodiment of the present invention at a short focal position;

[0023] Figure 6 FIG. 4 is a transfer function diagram of the optical system at the telephoto position according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] like Figure 1 、 Figure 2 As shown in the figure, the two-stage zoom large-target surface low-light optical system with variable aperture stop position according to the embodiment of the present invention comprises, from the object side to the image side, a front fixed group 1 with positive refractive power, a zoom group 2 with negative refractive power, and a rear fixed group 3 with positive refractive power. The front fixed group 1 is used to converge the object side light, and the aperture stop 4 is a virtual optical stop whose position changes with the focal length. A mechanical variable stop is provided on the rear surface of the last lens in the front fixed group. Figure 2 As shown in FIG, when the zoom group 2 is away from the front fixed group 1, the optical system is in the telephoto position, the aperture of the mechanical variable iris is reduced, and the light beam aperture is limited. At this time, the position of the mechanical variable iris is the position of the virtual aperture stop 4, and the F# is 3; Figure 1 As shown, when the zoom group 2 is close to the front fixed group 1, the optical system is in a short-focus position, the aperture of the mechanical variable iris becomes larger, and the beam aperture is no longer restricted. At this time, the surface limiting the beam aperture is the front surface of the first lens of the front fixed group, that is, the virtual aperture diaphragm 4 is located on the front surface of the first lens of the front fixed group, and the F# is 1.4.

[0026] The optical system of the embodiment of the present invention has an operating band of 450nm to 950nm, a focal length of 80mm / 120mm, a total optical length of 123.6mm, and is suitable for a solid-state low-light-level CCD with a resolution of 1280×1024 and a pixel size of 12μm×12μm.

[0027] Specifically, the front fixed group 1 consists of a cemented lens 11 and a cemented lens 2 12. The cemented lens 1 consists of a meniscus light crown lens with negative optical power and a fluorite biconvex lens with positive optical power; the cemented lens 2 consists of a biconvex fluorite crown lens with positive optical power and a lanthanum flint biconcave lens with negative optical power.

[0028] Zoom group 2 consists of zoom lens 1 21, zoom lens 2 22, and cemented lens 3 23. Zoom lens 1 21 is a biconvex lanthanum flint lens with positive focal power; zoom lens 2 22 is a meniscus lanthanum flint lens with negative focal power; cemented lens 3 23 consists of a meniscus fluorine crown lens with positive focal power and a biconcave heavy flint lens with negative focal power. The center-to-center distance between zoom group 2 and the rear surface of cemented lens 2 12 of front fixed group 1 varies from 33.7mm to 4.2mm.

[0029] Rear fixed group 3 consists of rear fixed mirror 1 31, filter 32, and rear fixed mirror 2 33. Rear fixed mirror 1 31 is a biconvex heavy barium flint lens with positive optical power; rear fixed mirror 2 32 is a meniscus lanthanum flint lens with negative optical power. Filter 32 is made of flat glass and can be switched or selected according to actual usage.

[0030] In a preferred embodiment of the present invention, the specific design parameters of the optical system are shown in Table 1.

[0031] Table 1 Optical system design parameters

[0032]

[0033] Table 2 Transfer function values

[0034]

[0035] In Table 1, curvature radius refers to the curvature radius of each lens surface, thickness or spacing refers to the lens thickness or the distance between adjacent lens surfaces, material refers to the material used for the lens, and air refers to the medium between the two lenses being air.

[0036] Figure 3-6 They are a two-dimensional diagram and a transfer function curve of a two-speed zoom large target surface low-light optical system with variable aperture stop position at a long focus position and a short focus position, respectively.

[0037] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A two-step zoom large target surface low-light optical system with variable aperture diaphragm position, characterized in that: The lens comprises, from the object side to the image side, a front fixed group (1) with positive refractive power, a zoom group (2) with negative refractive power, and a rear fixed group (3) with positive refractive power, wherein the zoom group (2) is used for zooming and focusing simultaneously; The optical system further comprises a mechanical variable iris, which is located on the rear surface of the last lens of the front fixed group (1); when the zoom group (2) is away from the front fixed group (1), the aperture of the mechanical variable iris is reduced, and the optical system is in a telephoto position; when the zoom group is close to the front fixed group (1), the aperture of the mechanical variable iris is increased, and the optical system is in a short-focus position, and the virtual aperture iris formed is located on the front surface of the first lens of the front fixed group (1); in: The front fixed group (1) includes a first cemented lens (11) and a second cemented lens (12); the first cemented lens includes a meniscus light crown lens with negative focal power and a fluorite biconvex lens with positive focal power; the second cemented lens includes a biconvex fluorite crown lens with positive focal power and a lanthanum flint biconcave lens with negative focal power; The zoom group (2) includes a zoom lens 1 (21), a zoom lens 2 (22) and a cemented lens 3 (23); the zoom lens 1 (21) is a double convex lanthanum flint lens with positive focal length; the zoom lens 2 (22) is a meniscus lanthanum flint lens with negative focal length; the cemented lens 3 (23) includes a meniscus fluorine crown lens with positive focal length and a double concave heavy flint lens with negative focal length; The rear fixed group (3) includes a rear fixed mirror 1 (31), a filter (32) and a rear fixed mirror 2 (33); the rear fixed mirror 1 (31) is a double convex heavy barium flint lens with positive optical power; the rear fixed mirror 2 (33) is a meniscus lanthanum flint lens with negative optical power; the filter (32) is a flat glass; The zoom group (2) is also used for moving forward and backward along the optical axis to compensate for temperature and drift of the image plane of the long-wave infrared optical system during close-range imaging.

2. The two-step zoom large target surface low-light optical system with variable aperture stop position according to claim 1, characterized in that: When the optical system is in the telephoto position, F# is 3, and when the optical system is in the short focal position, F# is 1.

4.

3. The two-step zoom large target surface low-light optical system with variable aperture stop position according to claim 1, characterized in that: The operating band of the optical system is 450nm~950nm, the focal length is 80mm / 120mm, and the total optical length is 123.6mm.

4. The two-step zoom large target surface low-light optical system with variable aperture stop position according to claim 1, characterized in that: The optical system is applied to a solid-state low-light-level CCD with a resolution of 1280×1024 and a pixel size of 12μm×12μm.

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