An ultra-wide field of view passive athermalized fish-eye optical system

Abstract

An ultra-large field of view passive athermalized fish-eye optical system of the present invention belongs to the technical field of optics; it includes a first lens, a second lens, a third lens, a first cemented lens, a fourth lens, a fifth lens, a second cemented lens, a third cemented lens, and a sixth lens arranged in sequence along the optical path; the first lens and the second lens are meniscus lenses with negative optical power, the third lens is a biconcave lens with negative optical power, the first cemented lens is a doublet lens with positive optical power, the fourth lens and the fifth lens are biconvex lenses with positive optical power, the second cemented lens is a doublet lens with negative optical power, the third cemented lens is a doublet lens with positive optical power, and the sixth lens is a biconvex lens with positive optical power; the second lens and the fourth lens adopt aspherical surfaces, and the remaining lenses are all composed of spherical lenses. The present invention can observe multiple targets within the ultra-hemisphere range and realizes high-quality imaging in the visible light band with an ultra-large field of view.

Description

Technical Field

[0001] The present invention belongs to the technical field of optics, and particularly relates to an ultra-large field of view passive athermalized fisheye optical system. Background Art

[0002] With the development of optical technology, high-resolution images and large field of view requirements are needed in many fields. Ultra-wide-angle optical imaging systems, such as fisheye lens optical systems, are special optical systems with very large imaging field angles. They can achieve the acquisition of all-airspace inclusion and all-time-domain real-time information, realizing functions that ordinary imaging systems cannot achieve. Since fisheye lenses can obtain a field of view that general optical systems cannot reach, they have a wide range of applications in many fields. For a fisheye lens optical system, it can be divided into a front group optical system and a rear group optical system; the front group optical system is generally composed of several negative meniscus lenses, which play a role in compressing the field angle; the rear group optical system is composed of a conventional optical system. In a fisheye lens optical system, the field angle of light rays emitted from object points with a large field angle hitting the surface of optical elements is very large, resulting in relatively serious aberrations in such optical systems; in addition, in current applications in various fields, in order to obtain clearer images, small and medium apertures cannot meet the requirements, so large-aperture imaging is pursued, which makes the design of such optical systems more complex.

[0003] Currently, such domestic fisheye optical systems have low resolution, large volume, large weight, and cannot achieve clear imaging within a wide temperature range. When applied to aircraft, athermalization cannot be achieved in the harsh airborne environment, resulting in unclear imaging. Summary of the Invention

[0004] Technical Problems to be Solved

[0005] In order to avoid the deficiencies of the prior art, the present invention provides an ultra-large field of view passive athermalized fisheye optical system, which is used to photograph the scene below the aircraft, the retraction and extension of the landing gear, the opening and closing of the cabin door, and the situation of the rear target. Through the cooperation of lenses and cemented lenses, passive athermalization can be achieved in the airborne environment, and clear imaging can be achieved within a wide temperature range without focusing.

[0006] The technical solution of the present invention is: an ultra-large field of view passive athermalized fisheye optical system, including a first lens, a second lens, a third lens, a first cemented lens, a fourth lens, a fifth lens, a second cemented lens, a third cemented lens, and a sixth lens arranged in sequence along the optical path;

[0007] Among them, the first lens and the second lens are meniscus lenses with negative optical power, the third lens is a biconcave lens with negative optical power, the first cemented lens is a doublet lens with positive optical power, the fourth lens and the fifth lens are biconvex lenses with positive optical power, the second cemented lens is a doublet lens with negative optical power, the third cemented lens is a doublet lens with positive optical power, and the sixth lens is a biconvex lens with positive optical power;

[0008] The second lens and the fourth lens adopt aspherical surfaces, and the remaining lenses are all composed of spherical lenses.

[0009] A further technical solution of the present invention is that the data of the fish-eye optical system are as follows:

[0010]

[0011]

[0012] A further technical solution of the present invention is that the fish-eye optical system is of a straight barrel type.

[0013] A further technical solution of the present invention is that the fish-eye optical system adopts a passive athermal design to achieve clear imaging in a wide temperature range from -55° to 95°.

[0014] A further technical solution of the present invention is that the field of view of the fish-eye optical system is a super-hemispherical field of view, and the circular field of view is not less than 200°.

[0015] A further technical solution of the present invention is that the materials of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass.

[0016] A further technical solution of the present invention is that the first lens adopts fused silica, and the front surface is not coated with an anti-reflection film layer to prevent the film layer from being scratched and falling off after sand blowing in bad weather.

[0017] Beneficial effects

[0018] The beneficial effects of the present invention are as follows: The present invention provides a super-wide-field passive athermal fish-eye optical system, which adopts a combined design of 6 lenses and 3 cemented lenses, can observe multiple targets within a super-hemispherical range, and realizes high-quality imaging in the visible light band with a super-wide field of view. Among them, the second lens and the fourth lens adopt aspherical designs, which increase the degree of freedom in the design process of the optical system, increase the number of selectable variables, coordinate and correct the coma, spherical aberration, and astigmatism of the system, greatly improve the image quality, and it is easy to obtain excellent image quality;

[0019] The present invention uses a variety of visible light optical materials for thermal-difference elimination material matching. Considering the relatively harsh airborne environment compared to the ground environment, it can achieve passive thermal-difference elimination within a wide temperature range and clear imaging. Through the mutual combination of different materials, the optical system can maintain high-quality imaging within a wide temperature range of -55°C to +95°C.

[0020] The optical system adopts a straight-tube configuration, which is structurally compact, greatly reduces the process requirements, and all components in the optical path are fixed components, making the alignment simple and largely reducing the alignment difficulty of the system, which is conducive to mass production. Brief Description of the Drawings

[0021] Figure 1 is the optical path diagram of the optical system of the present invention;

[0022] Figure 2 is the MTF curve diagram of the optical system of the present invention at room temperature;

[0023] Figure 3 is the MTF curve diagram of the optical system of the present invention at -55°C low temperature;

[0024] Figure 4 is the MTF curve diagram of the optical system of the present invention at +95°C high temperature.

[0025] Description of the Reference Numerals: 1. First lens, 2. Second lens, 3. Third lens, 4. First cemented lens, 5. Fourth lens, 6. Fifth lens, 7. Second cemented lens, 8. Third cemented lens, 9. Sixth lens. Detailed Embodiment

[0026] The embodiments described below by referring to the drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0027] Referring to Figure 1 as shown, an ultra-wide field-of-view passive thermal-difference elimination fish-eye optical system in this embodiment adopts a straight-tube type one-time imaging system configuration, and the entire optical system is composed of six single lenses and three cemented lenses. This system includes from the object side: First lens 1, Second lens 2, Third lens 3, First cemented lens 4, Fourth lens 5, Fifth lens 6, Second cemented lens 7, Third cemented lens 8, Sixth lens 9;

[0028] The first lens 1 and the second lens 2 are meniscus lenses with negative optical power, the third lens 3 is a biconcave lens with negative optical power, the first cemented lens 4 is a doublet lens with positive optical power, the fourth lens 5 and the fifth lens 6 are biconvex lenses with positive optical power, the second cemented lens 7 is a doublet lens with negative optical power, the third cemented lens 8 is a doublet lens with positive optical power, and the sixth lens 9 is a biconvex lens with positive optical power;

[0029] The second lens 2 and the fourth lens 5 are aspherical lenses, and the remaining lenses are all spherical lenses.

[0030] The specific parameters of this optical system are shown in Table 1.

[0031] Table 1 Data Sheet of the Optical System

[0032]

[0033]

[0034] Among them, the materials of the first lens 1, the second lens 2, the third lens 3, the fourth lens 5, the fifth lens 6, and the sixth lens are all glass.

[0035] The fish-eye optical system of the present invention adopts a passive athermal design to achieve clear imaging within a wide temperature range from -55°C to 95°C. The field of view of the fish-eye optical system is a super-hemispherical field of view, and the circular field of view is not less than 200°.

[0036] Since the field of view of the optical system already exceeds a hemisphere, a flat optical window is no longer applicable. Either a super-hemispherical dome is used or the optical window is no longer used. The present invention adopts the scheme of not using an optical window. At the same time, in order to prevent the first lens from being affected by sand and wind during use and causing frosting, which will affect the imaging effect, therefore, the first lens is made of quartz glass with a relatively high hardness, and the front surface is not coated with an anti-reflection film layer to prevent the film layer from being scratched and falling off after sand blowing in bad weather.

[0037] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principle and spirit of the present invention.

Claims

1. An ultra-wide field of view passive athermalized fisheye optical system, Characterized in that: It includes a first lens, a second lens, a third lens, a first cemented lens, a fourth lens, a fifth lens, a second cemented lens, a third cemented lens, and a sixth lens arranged in sequence along the optical path; The first lens and the second lens are meniscus lenses with negative optical power, the third lens is a biconcave lens with negative optical power, the first cemented lens is a doublet lens with positive optical power, the fourth lens and the fifth lens are biconvex lenses with positive optical power, the second cemented lens is a doublet lens with negative optical power, the third cemented lens is a doublet lens with positive optical power, and the sixth lens is a biconvex lens with positive optical power; The second lens and the fourth lens adopt aspherical surfaces, and the remaining lenses are all composed of spherical lenses; The data of the fisheye optical system are as follows: 。 2. The ultra-wide field of view passive athermalized fisheye optical system according to claim 1, Characterized in that: The fisheye optical system is a straight barrel type.

3. The ultra-wide field of view passive athermalized fisheye optical system according to claim 1, Characterized in that: The fisheye optical system adopts a passive athermalization design to achieve clear imaging in a wide temperature range from -55°C to 95°C.

4. The ultra-wide field of view passive athermalized fisheye optical system according to claim 1, Characterized in that: The field of view of the fisheye optical system is a super-hemispherical field of view, and the circular field of view is not less than 200°.

5. The ultra-wide field of view passive athermalized fisheye optical system according to claim 1, Characterized in that: The materials of the first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all glass.

6. The ultra-wide field of view passive athermalized fisheye optical system according to any one of claims 1-5, Characterized in that: The first lens adopts fused silica, and the front surface is not coated with an anti-reflection film layer to prevent the film layer from being scratched and falling off after sandblasting in bad weather.

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