CN111999866B - An optical system of a large field of view and low distortion aerial survey camera - Google Patents

Abstract

The invention relates to an optical system of a large field of view and low distortion aerial survey camera, comprising a front group lens, a diaphragm and a rear group lens; the elements of the front group lens and the rear group lens are arranged in sequence along the optical axis; the focal length of the front group lens is 100mm, and the rear group lens Lens focal length is ‑500. The optical system adopts the telecentric design of the quasi-image side, and the maximum incident angle outside the image plane axis is less than 20°. The total length of the optical system is 320mm; the length of the back focal length of the optical system is 67mm. The invention has the characteristics of large field of view, high resolution, and telecentricity of the quasi-image side, and also has the characteristics of symmetrical structure, light and small size, and low cost.

Description

An optical system of a large field of view and low distortion aerial survey camera

technical field

The invention belongs to the technical field of aerial remote sensing and surveying and mapping, and relates to an optical system applied to a spliced large area array digital aerial survey camera.

Background technique

Large-format, large-field, and high-resolution area scan cameras are the inevitable direction for the development of aerial survey cameras. At present, the more famous aerial survey cameras in the world mainly include Leica's ADS40/80, Intergraph's DMC series, and MicrosoftVexcel's UltraCam series. However, due to the technical bottleneck of a single large-format device due to the high cost, currently only DMCII uses a single large area CCD with a maximum resolution of 17k × 14k. Other aerial survey cameras are mostly formed by a combination of multi-lens and multi-detector splicing structures. Large format.

For a large area aerial survey camera with a combination of multiple lenses and multiple detectors, the optical system generally requires the characteristics of long focal length, wide field of view, ultra-low distortion and telecentricity of the quasi-image. The Institute of Optoelectronic Technology of the Chinese Academy of Sciences proposed a panchromatic objective lens for aerial survey cameras. The objective lens has a large field of view, low distortion and long working distance. However, the optical system does not have the characteristics of quasi-image telecentricity, and the front end of the system is too large and the total length is too long. When the system focal length is 118.93mm, the total length of the system is 336.5mm, and the system is not small enough. risk of interference. The Xi'an Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences proposed an optical system for aerial survey cameras. The optical system has the characteristics of large field of view, high resolution, low distortion, and telecentricity of the quasi-image side, but the back focal length of the system is only 25mm short. , and the total length of the system is long. When the focal length is 156mm, the total length of the system is 474.88mm. When this system is used for splicing, the weight of the whole machine will inevitably increase. The system contains a total of 14 lenses, but as many as 11 types of optical glass materials are used, which increases the system cost.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies of the prior art, and to propose an optical system of a large field of view and low distortion aerial survey camera, which has the characteristics of large field of view, high resolution, and telecentricity of the quasi-image side, as well as symmetrical structure and small size. , low cost and so on.

The invention is realized by the following technical solutions: an optical system of a large field of view and low distortion aerial survey camera, comprising: a front group lens, a diaphragm and a rear group lens; the elements of the front group lens and the rear group lens are arranged in sequence along the optical axis; The focal length of the group lens is 100mm, and the focal length of the rear group lens is -500.

The focal length of the optical system: 142mm; the field of view is 68°; the relative aperture is 5.6; the distortion is less than 0.005%.

The optical system adopts the telecentric design of the quasi-image side, and the maximum incident angle outside the image plane axis is less than 20°.

The total length of the optical system is 320mm; the length of the back focal length of the optical system is 67mm.

The front lens group includes a first negative lens, a second negative lens, a first positive lens, a second positive lens, a third negative lens, and a third positive lens arranged in sequence along the same optical axis; the rear lens group includes a sequence along the same optical axis. A fourth positive lens, a fourth negative lens, a fifth positive lens, a fifth negative lens, a sixth negative lens, and a sixth positive lens are provided.

The concave surface of the first positive lens is aspherical, the rear surface of the third positive lens is aspherical, and the concave surface of the sixth negative lens is aspherical.

The optical material of the first negative lens is H-K9L, the optical material of the second negative lens is H-K9L, the optical material of the first positive lens is H-K9L, and the optical material of the second positive lens is H-K9L, The optical material of the third negative lens is H-K9L, the optical material of the third positive lens is H-FK61, the optical material of the fourth positive lens is H-FK61, the optical material of the fourth negative lens is H-TF3L, the fifth The optical material of the positive lens is BaF4, the optical material of the fifth negative lens is H-K9L, the optical material of the sixth negative lens is H-K9L, and the optical material of the sixth positive lens is H-K9L.

The focal lengths of each lens are as follows:

The first negative lens: -1.8f<f1<-f,

Second negative lens: -1.7f<f2<-0.9f,

The first positive lens: 3.5f<f3<4.3f,

Second positive lens: 0.7f<f4<1.5f,

The third negative lens: -1.7f<f5<-0.9f,

The third positive lens: 0.1f<f6<f,

Fourth positive lens: 0.1f<f7<f,

Fourth negative lens: -0.7f<f8<-0.1f,

Fifth positive lens: 0.2f<f9<f,

Fifth negative lens: -1.4f<f10<-0.6f,

Sixth negative lens: -1.3f<f11<-0.5f,

Sixth positive lens: 1.5f<f12<2.3f.

Compared with the prior art, the present invention has the following advantages:

1) The field of view angle of the present invention is 68°, and the distortion is 0.005%, which achieves the requirement of ultra-low distortion under the super-large field of view;

2) When the focal length of the present invention is 142mm, its length is only 320mm, and the back focal length is 67mm, which realizes a miniaturized and lightweight design;

3) The maximum incident angle of the image plane of the present invention is less than 20°, which realizes the telecentric design of the quasi-image side, and ensures the uniformity of the illuminance of the image plane and the limit resolution of the off-axis field of view.

4) The present invention includes 12 lenses, only four kinds of materials are used, and most of the lenses are made of H-K9L, an optical material with low price but excellent performance, which reduces the system manufacturing cost.

Description of drawings

FIG. 1 is a structural diagram of an optical system of the present invention.

FIG. 2 is an aberration curve diagram of the optical system of the present invention.

FIG. 3 is the MTF curve of the optical system of the present invention.

Detailed ways

As shown in Figures 1-3, the main performance indicators of the large field of view low distortion optical system of the present invention are:

1. The working spectrum is 500nm-700nm;

2. System focal length: 142mm;

3. The field of view is 68°;

4. The relative aperture is 5.6;

5. Distortion is less than 0.005%;

6. The telecentric design of the quasi-image side, the maximum incident angle outside the image plane axis is less than 20°;

7. The total length of the optical system is 320mm;

8. The focal length of the optical system is 67mm;

The optical system has a very small distortion and telecentricity is contradictory. The general aerial camera optical system mostly adopts a symmetrical structure. Although the field of view angle is large, the distortion can be corrected to a small amount. The exit angle of the optical system and the incident angle The angle is equal, and the telecentricity of the optical system is very poor. Therefore, for the optical system with a large field of view, the edge illumination of the image plane will be very low, and the uniformity of the image plane illumination will be very poor, which seriously affects the application.

The large field of view and low distortion aerial survey camera optical system proposed by the present invention properly balances this inherent contradiction by skillfully setting the optical power of each group of the optical system. The front lens group of the optical system includes a first negative lens 1 , a second negative lens 2 , a first positive lens 3 , a second positive lens 4 , a third negative lens 5 , and a third positive lens 6 arranged in sequence along the same optical axis. The rear group of lenses includes a fourth positive lens 7, a fourth negative lens 8, a fifth positive lens 9, a fifth negative lens 10, a sixth negative lens 11, and a sixth positive lens 12, which are sequentially arranged along the same optical axis. The focal length of the front group is about 100mm, and the focal length of the rear group is about -500.

The front group adopts a structure in which the negative lens is in the front and the positive lens is behind. The light is diffused by the negative lens and then enters the positive lens to converge, which is used to increase the field of view of the system, reduce the size of the lens at the front of the lens, and improve the uniformity of illumination on the image surface. sex. Due to the relatively large aperture of the front group, the introduced advanced aberrations related to the aperture increase. The optical system is designed to introduce an aspheric surface for correction. The aspheric surface is set on the concave surface of the first positive lens and the rear surface of the third positive lens.

The rear group adopts a negative-positive-negative structure. The fourth positive lens and the fourth negative lens of the rear group are combined with optical materials H-FK61 and H-TF3L to form a negative focal length. The fifth positive lens and the fifth negative lens are made of optical materials BaF4 and The H-FK61 is combined into a positive focal length, and the sixth negative lens and the sixth positive lens are both optical materials H-K9L combined into a negative focal length. The combination of the fourth positive lens and the fourth negative lens is used to correct the primary chromatic aberration and secondary spectrum of the system. The negative focal length formed by the fourth positive lens and the fourth negative lens is combined with the positive focal length formed by the fifth positive lens and the fifth negative lens. The combination further eliminates the advanced chromatic aberration of the system and vertical axis aberrations such as large coma and distortion in the front group, and the concave surface of the sixth negative lens in the rear group introduces an aspheric surface to further eliminate the residual aberration of the system.

The focal length of each lens is as follows:

First negative lens 1: -1.8f<f1<-f

Second negative lens 2: -1.7f<f2<-0.9f

First positive lens 3: 3.5f<f3<4.3f

Second positive lens 4: 0.7f<f4<1.5f

The third negative lens 5: -1.7f<f5<-0.9f

Third positive lens 6: 0.1f<f6<f

Fourth positive lens 7: 0.1f<f7<f

Fourth negative lens 8: -0.7f<f8<-0.1f

Fifth positive lens 9: 0.2f<f9<f

Fifth negative lens 10: -1.4f<f10<-0.6f

Sixth negative lens 11: -1.3f<f11<-0.5f

Sixth positive lens 12: 1.5f<f12<2.3f

According to the above-mentioned optical path sequence and the focal length constraints of each lens, an example parameter determined by the final optimization is shown in the following table.

The content that is not described in detail in the present invention belongs to the well-known technology of those skilled in the art.

Claims (3)

1. A large field of view low distortion aerial survey camera optical system, comprising: the lens comprises a front group of lenses, a diaphragm and a rear group of lenses; the elements of the front group lens and the rear group lens are sequentially arranged along the optical axis; the focal length of the front group of lenses is 100mm, and the focal length of the rear group of lenses is-500 mm;

focal length of the optical system: 142 mm; the field angle is 68 degrees; the relative aperture is 5.6; distortion is less than 0.005%;

the total length of the optical system is 320 mm; the length of the rear intercept of the optical system is 67 mm;

the front group of lenses comprises a first negative lens (1), a second negative lens (2), a first positive lens (3), a second positive lens (4), a third negative lens (5) and a third positive lens (6) which are sequentially arranged along the same optical axis; the rear group of lenses comprises a fourth positive lens (7), a fourth negative lens (8), a fifth positive lens (9), a fifth negative lens (10), a sixth negative lens (11) and a sixth positive lens (12) which are sequentially arranged along the same optical axis;

the concave surface of the first positive lens (3) is an aspheric surface, the rear surface of the third positive lens (6) is an aspheric surface, and the concave surface of the sixth negative lens (11) is an aspheric surface;

the number of the lens pieces with the focal power is 12;

the focal lengths of the lenses are as follows:

first negative lens: -1.8f < f1 < -f,

a second negative lens: -1.7f < f2 < -0.9f,

first positive lens: f3 is more than 3.5f and less than 4.3f,

a second positive lens: f4 is more than 0.7f and less than 1.5f,

third negative lens: -1.7f < f5 < -0.9f,

a third positive lens: f6 is more than 0.1f and less than f,

fourth positive lens: f7 is more than 0.1f and less than f,

fourth negative lens: -0.7f < f8 < -0.1f,

a fifth positive lens: f9 is more than 0.2f and less than f,

fifth negative lens: -1.4f < f10 < -0.6f,

sixth negative lens: -1.3f < f11 < -0.5f,

sixth positive lens: 1.5f < f12 < 2.3 f.

2. The large-field-of-view low-distortion aerial survey camera optical system as claimed in claim 1, wherein the optical system is of a quasi-image-side telecentric design, and the maximum off-axis angle of incidence of the image plane is less than 20 °.

3. The large-field-of-view low-distortion aerial survey camera optical system of claim 2, the optical material of the first negative lens (1) is H-K9L, the optical material of the second negative lens (2) is H-K9L, the optical material of the first positive lens (3) is H-K9L, the optical material of the second positive lens (4) is H-K9L, the optical material of the third negative lens (5) is H-K9L, the optical material of the third positive lens (6) is H-FK61, the optical material of the fourth positive lens (7) is H-FK61, the optical material of the fourth negative lens (8) is H-TF3L, the optical material of the fifth positive lens (9) is BaF4, the optical material of the fifth negative lens (10) is H-K9L, the optical material of the sixth negative lens (11) is H-K9L, and the optical material of the sixth positive lens (12) is H-K9L.

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