Low-distortion fisheye optical system for space environment

Abstract

The present invention relates to a low-distortion fish-eye optical system for a space environment, which solves the technical problem that traditional optical systems cannot take into account the field of view, focal length, and light weight and miniaturization. It includes a first negative lens, a second negative lens, a first positive lens, an aperture, a second positive lens, a third negative lens, a third positive lens, and a filter arranged in sequence along the optical axis from the object side to the image side; the focal length f’1 of the first negative lens satisfies: -4f’ < f’1 < -3f’; the focal length f’2 of the second negative lens satisfies: -2f’ < f’2 < -f’; the focal length f’3 of the first positive lens satisfies: f’ < f’3 < 2f’; the focal length f’4 of the second positive lens satisfies: f’ < f’4 < 2f’; the focal length f’5 of the third negative lens satisfies: -3f’ < f’5 < -2f’; the focal length f’6 of the third positive lens satisfies: 9f’ < f’6 < 10f’; where f’ is the focal length of the optical system. This system has the characteristics of high imaging quality, large imaging field of view, wide imaging range, good adaptability to the space environment, small size, and light weight.

Description

Technical Field

[0001] This invention belongs to the field of optical systems, specifically relating to a low-distortion fisheye optical system for use in space environments. It is primarily used for space target imaging and wide-field imaging, but can also be applied to civilian machine vision and security imaging equipment, as well as other fields requiring large field-of-view optical systems. Background Technology

[0002] With the rapid development of my country's national economy and defense industry technology, the demand for situational awareness around spacecraft is increasing, and the need for space target imaging and wide-area imaging is becoming more urgent, placing higher demands on the imaging effect and performance of ultra-large field-of-view optical systems. Optical imaging systems can acquire target images and obtain position parameters through image recognition technology, playing a crucial role in space target imaging and wide-area imaging. Currently, ultra-large field-of-view optical imaging systems have been successfully applied in spacecraft such as the International Space Station and the Space Shuttle.

[0003] Optical systems used in these applications require a large field of view for imaging. To adapt to missions under different lighting conditions, they must be able to achieve good imaging over a wide object distance range; and to meet the needs of space missions, the optical systems must be miniaturized.

[0004] However, existing optical systems cannot simultaneously meet the requirements of a large field of view, a wide spectral range, and miniaturization. Summary of the Invention

[0005] The purpose of this invention is to provide a low-distortion fisheye optical system for space environments, aiming to solve the technical problems of traditional optical systems being unable to simultaneously achieve optimal field of view, focal length, and miniaturization. It features high imaging quality, a large imaging field of view, a wide imaging range, good adaptability to space environments, small size, and light weight.

[0006] The technical solution of this invention is:

[0007] A low-distortion fisheye optical system for space environments is characterized by comprising a first negative lens, a second negative lens, a first positive lens, an aperture stop, a second positive lens, a third negative lens, a third positive lens, and a filter arranged sequentially along the optical axis from the object side to the image side.

[0008] The focal length f'1 of the first negative lens mentioned above satisfies: -4f' <f’1<-3f’;

[0009] The focal length f'2 of the second negative lens mentioned above satisfies: -2f' <f’2<-f’;

[0010] The focal length f'3 of the first positive lens mentioned above satisfies: f' <f’3<2f’;

[0011] The focal length f'4 of the second positive lens mentioned above satisfies: f' <f’4<2f’;

[0012] The focal length f'5 of the third negative lens mentioned above satisfies: -3f' <f’5<-2f’;

[0013] The focal length f'6 of the third positive lens mentioned above satisfies: 9f' <f’6<10f’;

[0014] Where f' is the focal length of the optical system.

[0015] Furthermore, the surface that the light rays first reach is defined as the front surface of each lens, and the surface that the light rays reach afterward is defined as the rear surface of each lens;

[0016] The front surface radius of curvature R1 and the rear surface radius of curvature R2 of the first negative lens are respectively: 8f' <R1<10f’,f’<R2<2f’;

[0017] The front surface radius of curvature R3 and the rear surface radius of curvature R4 of the second negative lens are as follows:

[0018] 3f' <R3<4f’,0.5f’<R4<f’;

[0019] The radii of curvature R5 of the front surface and R6 of the rear surface of the first positive lens are as follows:

[0020] 2f' <R5<3f’,-3 f’<R6<-2f’;

[0021] The front surface radius of curvature R7 and the rear surface radius of curvature R8 of the second positive lens are as follows:

[0022] 2f' <R7<3f’, -2f’<R8<-f’;

[0023] The radius of curvature R9 of the front surface and the radius of curvature R of the rear surface of the aforementioned third negative lens 10 They are respectively:

[0024] - 2f' <R9<-f’,-3f’<R 10 <-2f';

[0025] The radius of curvature R of the front surface of the aforementioned third positive lens 11 and the radius of curvature R of the subsequent surface 12 They are respectively:

[0026] -5f' <R 11 <-3f',-3f' <R 12 <-2f'.

[0027] Furthermore, the refractive index n1 of the glass used in the first negative lens satisfies: 1.4 <n1<1.6;

[0028] The refractive index n2 of the glass used in the second negative lens described above satisfies: 1.5 <n2<1.7;

[0029] The refractive index n3 of the glass used in the third negative lens described above satisfies: 1.5 <n3<1.7;

[0030] The refractive index n4 of the glass used in the aforementioned fourth negative lens satisfies: 1.7 <n4<1.9;

[0031] The refractive index n5 of the glass used in the fifth negative lens described above satisfies: 1.8 <n5<2.0;

[0032] The refractive index n6 of the glass used in the aforementioned sixth negative lens satisfies: 1.5 <n6<1.7。

[0033] Furthermore, the back working distance of the aforementioned low-distortion fisheye optical system for space environments is greater than 4 mm, and the length is 42 mm.

[0034] The beneficial effects of this invention are:

[0035] 1. The optical system adopts a "- - + + - +" lens combination structure. The optical power distribution of the system determines the field curvature. The system of the present invention is more conducive to the correction of field curvature.

[0036] 2. The optical system uses fused silica JGS1 as the first negative lens. The excellent radiation resistance of GJS1 can effectively resist complex particle radiation in space.

[0037] 3. The optical system using the present invention can achieve the following performance indicators:

[0038] (1) It has a large imaging field of view and can ensure imaging quality within a 170° imaging field of view;

[0039] (2) The imaging field of view is large, and the imaging quality can be guaranteed from 1m to infinity;

[0040] (3) Within the entire field of view, the distortion is controlled within 2% within the imaging object distance range and imaging temperature range.

[0041] (4) Even in a vacuum environment, the indicators mentioned in (1)-(3) can still be achieved. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the optical system in the embodiment;

[0043] The accompanying diagrams are labeled as follows: 1. First negative lens; 2. Second negative lens; 3. First positive lens; 4. Aperture stop; 5. Second positive lens; 6. Third negative lens; 7. Third positive lens; 8. Filter;

[0044] Figure 2 MTF curve of the optical system in the example;

[0045] Figure 3 Image plane blur pattern of the optical system in the example embodiment;

[0046] Figure 4 The field curvature distortion curve of the optical system in the example is shown. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0048] See Figure 1 This embodiment is a low-distortion fisheye optical system for space environments. The system includes a first negative lens 1, a second negative lens 2, a first positive lens 3, an aperture stop 4, a second positive lens 5, a third negative lens 6, a third positive lens 7, and a filter 8. The first negative lens 1, the second negative lens 2, the first positive lens 3, the aperture stop 4, the second positive lens 5, the third negative lens 6, the third positive lens 7, and the filter 8 are sequentially arranged on the same optical path.

[0049] To better adapt to the space environment, the first mirror uses JGSl fused silica material with excellent radiation resistance, while the other glasses are made of ordinary optical glass.

[0050] To avoid the optical system's adhesive surface from detaching due to ultraviolet radiation or to cause a change in the performance of the photosensitive adhesive that would affect transmittance, no adhesive surface was used.

[0051] To obtain clear imaging over a wide area, the aperture needs to be as large as possible to provide more energy and information. Therefore, a full-field-of-view vignetting design is adopted in the design.

[0052] In practical operation, the first negative lens 1, the second negative lens 2, the first positive lens 3, the aperture 4, the second positive lens 5, the third negative lens 6, the third positive lens 7, and the filter 8 are configured with reference to the following parameters to achieve better results:

[0053] The optical characteristics of the first negative lens 1 are as follows:

[0054] -4f' <f’1<-3f’, 1.4<n1<1.6, 8f’<R1<10f’, f’<R2<2f’;

[0055] The optical characteristics of the second negative lens 2 are as follows:

[0056] -2f' <f’2<-f’, 1.5<n2<1.7, 3f’<R3<4f’, 0.5f’<R4<f’;

[0057] The optical characteristics of the first positive lens 3 are as follows:

[0058] f' <f’3<2f’, 1.5<n3<1.7, 2f’<R5<3f’, -3 f’<R6<-2f’;

[0059] The optical characteristics of the second positive lens 5 are as follows:

[0060] f' <f’4<2f’, 1.7<n4<1.9, 2f’<R7<3f’, -2f’<R8<-f’;

[0061] The optical characteristics of the third negative lens 6 are as follows:

[0062] -3f' <f’5<-2f’, 1.8<n5<2.0, - 2f’<R9<-f’, -3f’<R 10 <-2f';

[0063] The optical characteristics of the third positive lens 7 are as follows:

[0064] 9f' <f’6<10f’, 1.5<n6<1.7, -5f’<R 11 <-3f', -3f' <R 12 <-2f'.

[0065] This embodiment provides a set of specific parameters for each lens:

[0066] The optical characteristics of the first negative lens 1 are as follows:

[0067] G1=JGS1, R1=42.2mm, R2=7.3 mm, D1=2.7 mm, D2=6.8 mm;

[0068] The optical characteristics of the second negative lens 2 are as follows:

[0069] G2=H-ALK11, R3=19.8 mm, R4=4.8 mm, D3=1.5 mm, D4=5.2 mm;

[0070] The optical characteristics of the first positive lens 3 are as follows:

[0071] G3=H-ZK21, R5=12 mm, R6=-10.9 mm, D5=6.5 mm, D6=3 mm;

[0072] The optical characteristics of the second positive lens 5 are as follows:

[0073] G4=H-ZPK7, R7=15.3 mm, R8=-7.3 mm, D7=3.1 mm, D8=1.2 mm;

[0074] The optical characteristics of the third negative lens 6 are as follows:

[0075] G5=H-ZF88, R9=-5.6 mm, R 10 =-13.4 mm, D9=1.3 mm, D 10 =0.7 mm;

[0076] The optical characteristics of the third positive lens 7 are as follows:

[0077] G6=H-ZK21, R 11 =-25.8 mm, R 12 =-14.8 mm, D 11 =2.0 mm, D 12 =5.6 mm;

[0078] Where f' is the focal length of the optical system, f'1, f'2, ..., f'6 are the focal lengths of the six lenses, n1, n2, ..., n6 are the refractive indices of the glass used for the six lenses, G1, G2, ..., G6 are the materials of the six lenses, and D1, D2, ..., D... 12 The center thicknesses and air gaps of the six lenses are R1, R2, ... R. 12 These are the radii of curvature of the 12 surfaces of the 6 lenses.

[0079] like Figures 2 to 4 The optical system provided in this embodiment has a system focal length of approximately 5.38 mm, a field of view greater than 170°, an entrance pupil diameter greater than 1 mm, no vignetting across the entire field of view, and no cemented surface. Within the 450 nm-650 nm wavelength range and from 1 m to infinity, the MTF is greater than 0.2 at 50 lp / mm across the entire field of view. At the aligned position, the image quality is close to the diffraction limit, and the relative distortion is less than 2%.

[0080] This invention can also be applied to fields that require large depth-of-field optical systems, such as machine vision and security imaging equipment.

Claims

1. A low-distortion fisheye optical system for space environments, characterized in that: It consists of a first negative lens, a second negative lens, a first positive lens, an aperture stop, a second positive lens, a third negative lens, a third positive lens, and a filter arranged sequentially along the optical axis from the object side to the image side. The object-side surface of the first negative lens is convex, and the image-side surface is concave; the focal length f'1 of the first negative lens satisfies: -4f' <f’1<-3f’; The object-side surface of the second negative lens is convex, and the image-side surface is concave; the focal length f'2 of the second negative lens satisfies: -2f' <f’2<-f’; The object-side surface of the first positive lens is convex, and the image-side surface is also convex; the focal length f'3 of the first positive lens satisfies: f' <f’3<2f’; The object-side surface of the second positive lens is convex, and the image-side surface is also convex; the focal length f'4 of the second positive lens satisfies: f' <f’4<2f’; The object-side surface of the third negative lens is concave, and the image-side surface is convex; the focal length f'5 of the third negative lens satisfies: -3f' <f’5<-2f’; The object-side surface of the third positive lens is concave, and the image-side surface is convex; the focal length f'6 of the third positive lens satisfies: 9f' <f’6<10f’; Where f' is the focal length of the optical system.

2. The low-distortion fisheye optical system for space environments according to claim 1, characterized in that: The surface that the light rays first reach is defined as the front surface of each lens, and the surface that the light rays reach last is defined as the rear surface of each lens. The radii of curvature R1 of the front surface and R2 of the rear surface of the first negative lens are respectively: 8f' <R1<10f’,f’<R2<2f’; The radii of curvature R3 of the front surface and R4 of the rear surface of the second negative lens are respectively: 3f' <R3<4f’,0.5f’<R4<f’; The radii of curvature R5 of the front surface and R6 of the rear surface of the first positive lens are respectively: 2f' <R5<3f’,-3 f’<R6<-2f’; The radii of curvature R7 of the front surface and R8 of the rear surface of the second positive lens are respectively: 2f' <R7<3f’, -2f’<R8<-f’; The radius of curvature R9 of the front surface and the radius of curvature R of the rear surface of the third negative lens 10 They are respectively: - 2f' <R9<-f’,-3f’<R 10 <-2f'; The radius of curvature R of the front surface of the third positive lens 11 and the radius of curvature R of the subsequent surface 12 They are respectively: -5f' <R 11 <-3f',-3f' <R 12 <-2f'。 3. The low-distortion fisheye optical system for space environments according to claim 2, characterized in that: The refractive index n1 of the glass used in the first negative lens satisfies: 1.4 <n1<1.6; The refractive index n2 of the glass used for the second negative lens satisfies: 1.5 <n2<1.7; The refractive index n3 of the glass used for the first positive lens satisfies: 1.5 <n3<1.7; The refractive index n4 of the glass used for the second positive lens satisfies: 1.7 <n4<1.9; The refractive index n5 of the glass used for the third negative lens satisfies: 1.8 <n5<2.0; The refractive index n6 of the glass used for the third positive lens satisfies: 1.5 <n6<1.7。 4. The low-distortion fisheye optical system for space environments according to claim 3, characterized in that: The rear working distance is greater than 4mm, and the length is 42mm.

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