Low-distortion large field of view bifocal optical system

Abstract

The present application relates to a kind of low distortion large field of view bifocal optical system, overcome the problem that existing optical system cannot give attention to high-resolution imaging of central field of view and large field of view target search demand, including the first positive lens, second positive lens, third positive lens, first negative lens, second negative lens, fourth positive lens, diaphragm, fifth positive lens, third negative lens, sixth positive lens and optical filter being arranged along optical path;First positive lens, second positive lens, third positive lens, first negative lens, second negative lens, fourth positive lens, diaphragm, fifth positive lens, third negative lens, sixth positive lens, optical filter constitute long focal length optical system, for realizing the imaging of central near field of view;First negative lens, second negative lens, fourth positive lens, diaphragm, fifth positive lens, third negative lens, sixth positive lens, optical filter constitute short focal length optical system, for realizing the imaging of large field of view;Long focal length optical system and short focal length optical system are imaged in the same target surface partition.

Description

Technical Field

[0001] This invention relates to a low-distortion, large-field-of-view dual-focal-length optical system, mainly used for space target imaging and wide-area imaging, and can also be applied to fields requiring large-field-of-view optical systems, such as civilian machine vision and security imaging equipment. 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. Operating in harsh environments with drastic temperature variations, the optical systems need to have good space environment adaptability; to meet the needs of space missions, the optical systems must be miniaturized. While conventional fisheye optical systems can achieve large field-of-view imaging, their f-θ distortion-based optical systems have low central field-of-view resolution, making it difficult to simultaneously meet the requirements of high-resolution imaging in the central field of view and large field-of-view target search. Summary of the Invention

[0004] To overcome the problem that existing optical systems cannot simultaneously meet the requirements of high-resolution imaging in the central field of view and target search in a large field of view, this invention proposes a low-distortion, large-field-of-view dual-focal-length optical system. The long focal length in the central field of view of this system is used for high-resolution imaging of the central target, while the short focal length in the edge field of view is used for target search in a large field of view. This system features a large field of view, dual focal lengths, good adaptability to spatial environments, and meets the technical requirements of miniaturization.

[0005] The technical solution of this invention is:

[0006] A low-distortion, large-field-of-view dual-focal-length optical system is characterized by comprising a first positive lens, a second positive lens, a third positive lens, a first negative lens, a second negative lens, a fourth positive lens, an aperture stop, a fifth positive lens, a third negative lens, a sixth positive lens, and a filter arranged sequentially along the optical path from the object side to the image side.

[0007] The first positive lens, the second positive lens, the third positive lens, the first negative lens, the second negative lens, the fourth positive lens, the aperture stop, the fifth positive lens, the third negative lens, the sixth positive lens, and the filter constitute a long focal length optical system, which is used to achieve field of view imaging near the center.

[0008] Among them, the first negative lens, the second negative lens, the fourth positive lens, the aperture stop, the fifth positive lens, the third negative lens, the sixth positive lens, and the filter form a short focal length optical system for achieving large field of view imaging;

[0009] The long focal length optical system and the short focal length optical system share the imaging target surface and image in zones on the target surface.

[0010] Furthermore, the focal length f’1 of the above-mentioned first positive lens satisfies: 9f’ < f’1 < 10f’;

[0011] The focal length f’2 of the above-mentioned second positive lens satisfies: 8f’ < f’2 < 9f’;

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

[0013] The focal length f’4 of the above-mentioned second negative lens satisfies: -2f’ < f’4 < -f’;

[0014] The focal length f’5 of the above-mentioned third negative lens satisfies: -2f’ < f’5 < -f’;

[0015] The focal length f’6 of the above-mentioned third positive lens satisfies: 0.5f’ < f’6 < 1.5f’; 13 1>The focal length f’7 of the above-mentioned fourth positive lens satisfies: f’ < f’7 < 2f’;

[0017] The focal length f’8 of the above-mentioned fifth positive lens satisfies: f’ < f’8 < 2f’;

[0018] The focal length f’9 of the above-mentioned sixth positive lens satisfies: 2f’ < f’9 < 3f’;

[0019] Among them, f’ is the focal length of the long focal length optical system.

[0020] Furthermore, it is defined that the surface first reached by the light is the front surface of each lens, and the surface later reached by the light is the rear surface of each lens;

[0021] The front surface curvature radius R1 of the above-mentioned first positive lens is 2f’ < R1 < 3f’, and the rear surface curvature radius R2 of the first positive lens is 3f’ < R2 < 4f’;

[0022] The front surface curvature radius R3 of the above-mentioned second positive lens is f’ < R3 < 2f’, and the rear surface curvature radius R4 of the second positive lens is f’ < R4 < 2f’;

[0023] The front surface curvature radius R5 of the above-mentioned first negative lens is f’ < R5 < 2f’, and the rear surface curvature radius R6 of the first negative lens is 0.5f’ < R6 < f’;

[0024] The radius of curvature R7 of the front surface of the second negative lens is 2f’ < R7 < 3f’, and the radius of curvature R8 of the rear surface of the second negative lens is 0.5f’ < R8 < f’;

[0025] The radius of curvature R9 of the front surface of the third negative lens is 3f’ < R9 < 4f’, and the radius of curvature R 10 of the rear surface of the third negative lens is 0.5f’ < R 10 < f’;

[0026] The radius of curvature R 11 of the front surface of the third positive lens is f’ < R 11 < 2f’, and the radius of curvature R 12 of the rear surface of the third positive lens is -2f’ < R 12 < -f’;

[0027] The radius of curvature R 13 of the front surface of the fourth positive lens is 2f’ < R 13 < 3f’, and the radius of curvature R 14 of the rear surface of the fourth positive lens is -2f’ < R 14 < -f’;

[0028] The radius of curvature R 15 of the front surface of the fifth positive lens is -f’ < R 15 < -0.5f’, and the radius of curvature R 16 of the rear surface of the fifth positive lens is -3f’ < R 16 < -2f’;

[0029] The radius of curvature R 17 of the front surface of the sixth positive lens is -12f’ < R 17 < -10f’, and the radius of curvature R 18 of the rear surface of the sixth positive lens is -3f’ < R 18 < -2f’.

[0030] Furthermore, the refractive index n1 of the first positive lens is: 1.7 < n1 < 1.9;

[0031] The refractive index n2 of the second positive lens is: 1.7 < n2 < 1.9;

[0032] The refractive index n3 of the first negative lens is: 1.8 < n3 < 2.0;

[0033] The refractive index n4 of the second negative lens is: 1.5 < n4 < 1.7;

[0034] The refractive index n5 of the third negative lens is: 1.5 < n5 < 1.7;

[0035] The refractive index n6 of the third positive lens mentioned above is 1.6. <n6<1.8;

[0036] The refractive index n7 of the fourth positive lens mentioned above is 1.5. <n7<1.7;

[0037] The refractive index n8 of the fifth positive lens mentioned above is 1.8. <n8<2.0;

[0038] The refractive index n9 of the sixth positive lens mentioned above is 1.5. <n9<1.7。

[0039] Furthermore, the working distance of the aforementioned low-distortion, large-field-of-view dual-focal-length optical system is greater than 4mm.

[0040] Furthermore, short focal length optical systems achieve imaging within a half-field of view of 35°-85°; long focal length optical systems achieve imaging within a half-field of view of 0°-15°.

[0041] The beneficial effects of this invention are:

[0042] 1. This invention employs a dual-focal-length optical system, wherein the first positive lens, second positive lens, third positive lens, first negative lens, second negative lens, fourth positive lens, aperture stop, fifth positive lens, third negative lens, sixth positive lens, and filter constitute the long-focal-length optical system for achieving near-center field-of-view imaging; wherein the first negative lens, second negative lens, fourth positive lens, aperture stop, fifth positive lens, third negative lens, sixth positive lens, and filter constitute the short-focal-length optical system for achieving large field-of-view imaging; thus satisfying the requirements for high-resolution imaging of the central field of view and large field-of-view target search.

[0043] 2. The short focal length optical system of the present invention 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.

[0044] 3. The optical system of the present invention can achieve the following indicators:

[0045] (1) The short focal length optical system achieves high-quality imaging within a half field of view of 35°-85°;

[0046] (2) Long focal length optical systems achieve high-quality imaging within a half field of view of 0°-15°;

[0047] (3) Within the entire field of view, within the range of imaging object distance and imaging temperature, the distortion (f-θ) is controlled within 2%. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the optical system in the embodiment;

[0049] The attached diagram is labeled as follows: 1. First positive lens; 2. Second positive lens; 3. Third positive lens; 4. First negative lens; 5. Second negative lens; 6. Fourth positive lens; 7. Aperture stop; 8. Fifth positive lens; 9. Third negative lens; 10. Sixth positive lens; 11. Filter.

[0050] Figure 2 The optical path diagram of the optical system provided by this invention;

[0051] Figure 3 The MTF curve of the long focal length optical system in the optical system provided by this invention;

[0052] Figure 4 The MTF curve of the short focal length optical system provided in the optical system of this invention;

[0053] Figure 5 The image plane blur pattern of the long focal length optical system provided in the optical system of the present invention;

[0054] Figure 6 The image plane blur pattern of the short focal length optical system provided in the optical system of this invention;

[0055] Figure 7 The field curvature distortion curve of the long focal length optical system in the optical system provided by this invention;

[0056] Figure 8 The field curvature distortion curve of the short focal length optical system provided in the optical system of this invention. Detailed Implementation

[0057] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0058] See Figure 1 This embodiment is a low-distortion, large-field-of-view dual-focal-length optical system. The system includes a first positive lens 1, a second positive lens 2, a third positive lens 3, a first negative lens 4, a second negative lens 5, a fourth positive lens 6, an aperture stop 7, a fifth positive lens 8, a third negative lens 9, a sixth positive lens 10, and a filter 11 arranged sequentially on the same optical path.

[0059] 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.

[0060] 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.

[0061] In actual operation, the optical system is configured with reference to the following parameters for the first positive lens 1, the second positive lens 2, the third positive lens 3, the first negative lens 4, the second negative lens 5, the fourth positive lens 6, the aperture 7, the fifth positive lens 8, the third negative lens 9, the sixth positive lens 10, and the filter 11 to achieve better results:

[0062] The optical characteristics of the first positive lens 1 are as follows:

[0063] 9f' <f’1<10f’,1.7<n1<1.9,2f’<R1<3f’,3 f’<R2<4f’;

[0064] The optical characteristics of the second positive lens 2 are as follows:

[0065] 8f' <f’2<9f’,1.7<n2<1.9,f’<R3<2f’, f’<R4<2f’;

[0066] The optical characteristics of the first negative lens 4 are as follows:

[0067] -3f' <f’3<-2f’,1.8<n3<2.0,f’<R5<2f’,0.5f’<R6<f’;

[0068] The optical characteristics of the second negative lens 5 are as follows:

[0069] -2f' <f’4<-f’,1.5<n4<1.7,2f’<R7<3f’,0.5f’<R8<f’;

[0070] The optical characteristics of the third negative lens 9 are as follows:

[0071] -2f' <f’5<-f’,1.5<n5<1.7,3f’<R9<4f’,0.5f’<R 10 <f’;

[0072] The optical characteristics of the third positive lens 3 are as follows:

[0073] 0.5f' <f’6<1.5f’,1.6<n6<1.8, f’<R 11 <2f',-2f' <R 12 <-f';

[0074] The optical characteristics of the fourth positive lens 6 are as follows:

[0075] f' <f’7<2f’,1.5<n7<1.7, 2f’<R13 <3f', -2f' <R 14 <-f';

[0076] The optical characteristics of the fifth positive lens 8 are as follows:

[0077] f' <f’8<2f’,1.8<n8<2.0,-f’<R 15 <-0.5f',-3f' <R 16 <-2f';

[0078] The optical characteristics of the sixth positive lens 10 are as follows:

[0079] 2f' <f’9<3f’,1.5<n9<1.7,-12f’<R 17 <-10f',-3f' <R 18 <-2f'.

[0080] This embodiment provides a set of specific parameters for each lens:

[0081] The optical characteristics of the first positive lens 1 are as follows:

[0082] G1=H-ZLAF2A, R1=24.4mm, R2=37.2 mm, D1=3.1 mm, D2=2.0 mm;

[0083] The optical characteristics of the second positive lens 2 are as follows:

[0084] G2=H-LAK53A, R3=13.7 mm, R4=16.6 mm, D3=3.1 mm, D4=2.0 mm;

[0085] The optical characteristics of the first negative lens 4 are as follows:

[0086] G3=H-ZF72A, R5=12.8 mm, R6=7.2 mm, D5=3.0 mm, D6=4.0 mm;

[0087] The optical characteristics of the second negative lens 5 are as follows:

[0088] G4=JGS1, R7=42.2 mm, R8=7.3 mm, D7=2.7 mm, D8=6.8 mm;

[0089] The optical characteristics of the third negative lens 9 are as follows:

[0090] G5=H-ALK11, R9=19.8 mm, R 10 =4.8 mm, D9=1.5 mm, D 10=5.2 mm;

[0091] The optical characteristics of the third positive lens 3 are as follows:

[0092] G6=H-ZK21, R 11 =12 mm, R 12 =-10.9 mm, D 11 =6.5 mm, D 12 =3 mm;

[0093] The optical characteristics of the fourth positive lens 6 are as follows:

[0094] G7=H-ZPK7, R 13 =15.3 mm, R 14 =-7.3 mm, D 13 =3.1 mm, D 14 =1.2 mm;

[0095] The optical characteristics of the fifth positive lens 8 are as follows:

[0096] G8=H-ZF88, R 15 =-5.6 mm, R 16 =-13.4 mm, D 15 =1.3 mm, D 16 =0.7 mm;

[0097] The optical characteristics of the sixth positive lens 10 are as follows:

[0098] G9=H-ZK21, R 17 =-25.8 mm, R 18 =-14.8 mm, D 17 =2.0 mm, D 18 =5.6 mm;

[0099] Where f' is the focal length of the long focal length optical system, f'1, f'2, ..., f'9 are the focal lengths of the 9 lenses, n1, n2, ..., n9 are the refractive indices of the glass used for the 9 lenses, G1, G2, ..., G9 are the materials of the 9 lenses, and D1, D2, ..., D... 18 The center thickness and optical spacing of the nine lenses are R1, R2, ... R. 18 These are the radii of curvature of the 18 surfaces of the nine lenses.

[0100] In the optical system provided in this embodiment, the long focal length system has a focal length of approximately 8.78 mm, an imaging half-field of view of 0°-15°, and an entrance pupil diameter greater than 1.62 mm; the long focal length system has a focal length of approximately 5.4 mm, an imaging half-field of view of 35°-85°, and an entrance pupil diameter greater than 1.02 mm. Both systems exhibit no vignetting or cemented surfaces in their fields of view. Within the 450 nm-650 nm wavelength range, the MTF at 50 lp / mm is greater than 0.2 across the entire field of view, and the f-θ relative distortion is less than 2%. This invention can also be applied to fields requiring large depth-of-field optical systems, such as machine vision and security imaging equipment.

Claims

1. A low-distortion, large-field-of-view dual-focal-length optical system, characterized in that: It consists of a first positive lens, a second positive lens, a third positive lens, a first negative lens, a second negative lens, a fourth positive lens, an aperture stop, a fifth positive lens, a third negative lens, a sixth positive lens and a filter, which are arranged in sequence along the optical path from the object side to the image side; The object side surface of the first positive lens is convex, and the image side surface is concave; the object side surface of the second positive lens is convex, and the image side surface is concave; the object side surface of the third positive lens is convex, and the image side surface is concave; the object side surface of the first negative lens is convex, and the image side surface is concave; the object side surface of the second negative lens is convex, and the image side surface is concave; the object side surface of the fourth positive lens is convex, and the image side surface is convex; the object side surface of the fifth positive lens is convex, and the image side surface is convex; the object side surface of the third negative lens is concave, and the image side surface is convex; the object side surface of the sixth positive lens is concave, and the image side surface is convex; Among them, the first positive lens, the second positive lens, the third positive lens, the first negative lens, the second negative lens, the fourth positive lens, the aperture stop, the fifth positive lens, the third negative lens, the sixth positive lens and the filter constitute a long focal length optical system for realizing imaging of the field of view near the center; Among them, the first negative lens, the second negative lens, the fourth positive lens, the aperture stop, the fifth positive lens, the third negative lens, the sixth positive lens and the filter constitute a short focal length optical system for realizing imaging of a large field of view; The long focal length optical system and the short focal length optical system share an imaging target surface and perform partitioned imaging on the target surface; The focal length f’1 of the first positive lens satisfies: 9f’ < f’1 < 10f’; The focal length f’2 of the second positive lens satisfies: 8f’ < f’2 < 9f’; The focal length f’3 of the first negative lens satisfies: -3f’ < f’3 < -2f’; The focal length f’4 of the second negative lens satisfies: -2f’ < f’4 < -f’; The focal length f’5 of the third negative lens satisfies: -2f’ < f’5 < -f’; The focal length f’6 of the third positive lens satisfies: 0.5f’ < f’6 < 1.5f’; The focal length f’7 of the fourth positive lens satisfies: f’ < f’7 < 2f’; The focal length f’8 of the fifth positive lens satisfies: f’ < f’8 < 2f’; The focal length f’9 of the sixth positive lens satisfies: 2f’ < f’9 < 3f’; Among them, f’ is the focal length of the long focal length optical system.

2. The low-distortion, large-field-of-view dual-focal-length optical system according to claim 1, characterized in that: It is defined that the surface first reached by the light is the front surface of each lens, and the surface later reached by the light is the back surface of each lens; The front surface curvature radius R1 of the first positive lens satisfies: 2f’ < R1 < 3f’, and the back surface curvature radius R2 of the first positive lens satisfies: 3f’ < R2 < 4f’; The front surface curvature radius R3 of the second positive lens satisfies: f’ < R3 < 2f’, and the back surface curvature radius R4 of the second positive lens satisfies: f’ < R4 < 2f’; The front surface curvature radius R5 of the first negative lens satisfies: f’ < R5 < 2f’, and the back surface curvature radius R6 of the first negative lens satisfies: 0.5f’ < R6 < f’; The front surface curvature radius R7 of the second negative lens satisfies: 2f’ < R7 < 3f’, and the back surface curvature radius R8 of the second negative lens satisfies: 0.5f’ < R8 < f’; The front surface curvature radius R9 of the third negative lens satisfies 3f’ < R9 < 4f’, and the rear surface curvature radius R 10 is 0.5f’ < R 10 < f’; The radius of curvature R of the front surface of the third positive lens 11 f' <R 11 <2f', Radius of curvature R of the rear surface of the third positive lens 12 -2f' <R 12 <-f'; The radius of curvature R of the front surface of the fourth positive lens 13 2f' <R 13 <3f', the radius of curvature R of the rear surface of the fourth positive lens 14 -2f' <R 14 <-f'; The radius of curvature R of the front surface of the fifth positive lens 15 -f' <R 15 <-0.5f', the radius of curvature R of the rear surface of the fifth positive lens 16 -3f' <R 16 <-2f'; The radius of curvature R of the front surface of the sixth positive lens 17 -12f' <R 17 <-10f', Radius of curvature R of the rear surface of the sixth positive lens 18 -3f' <R 18 <-2f'.

3. The low-distortion, large-field-of-view dual-focal-length optical system according to claim 2, characterized in that: The refractive index n1 of the first positive lens is 1.

7. <n1<1.9; The refractive index n2 of the second positive lens is 1.

7. <n2<1.9; The refractive index n3 of the first negative lens is 1.

8. <n3<2.0; The refractive index n4 of the second negative lens is 1.

5. <n4<1.7; The refractive index n5 of the third negative lens is 1.

5. <n5<1.7; The refractive index n6 of the third positive lens is 1.

6. <n6<1.8; The refractive index n7 of the fourth positive lens is 1.

5. <n7<1.7; The refractive index n8 of the fifth positive lens is 1.

8. <n8<2.0; The refractive index n9 of the sixth positive lens is 1.

5. <n9<1.7。 4. The low-distortion, large-field-of-view dual-focal-length optical system according to claim 3, characterized in that: The system's back working distance is greater than 4mm.

5. The low-distortion, large-field-of-view dual-focal-length optical system according to claim 4, characterized in that: Short focal length optical systems enable imaging within a half-field of view of 35°-85°; long focal length optical systems enable imaging within a half-field of view of 0°-15°.

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