CN100334477C - Optical system of large caliber wide viewing field two-rang reflection type infrared camera - Google Patents

Abstract

The present invention discloses an optical system of a large caliber wide viewing field two-wave band reflection type infrared camera. The optical system is composed of five lenses and a cold light color separation group, wherein the five lenses of the optical system use a positive-negative-positive structure to eliminate a color difference and correct field curvature. The lenses made of three different materials of silicon, germanium and calcium fluoride are used for controlling the color difference. The lenses comprise three silicon lenses, a calcium fluoride lens and a germanium lens. The residual color difference, spherical aberration, a coma difference and aberration are eliminated mainly by two secondary aspheric surfaces. The optical system has the advantages that the large caliber and the large viewing field are realized in an infrared wide wave band range, and the line viewing field of the present invention achieves 172mm and can completely cover a super long linear array infrared focal plane detector. Simultaneously, the large caliber with the pupil inlet diameter of 150mm ensures that a diffraction area spot size of the optical system in a wave band range of 2 mu m to 4.5 mu m is smaller than a picture element size. Incident light energy is increased, and thus, the optical system has good imaging quality.

Description

Large caliber wide visual field two waveband refraction type infrared camera optical system

Technical field

The present invention relates to optical element, system, specifically being meant can be simultaneously in the heavy caliber of 2-3um, 3-4.5um two wave band imagings, wide visual field infrared camera optical system.It mainly is used on the overlength linear array scanned infrared camera, stares on the infrared camera but also can be used on super large face battle array.

Background technology

At aspects such as space science, astronomical research, Earth Information and environmental informations thereof, high resolving power, highly sensitive infrared camera are being brought into play more and more important effect.And the infrared camera optical system is the critical component of high resolving power, high sensitivity infrared camera.Along with the development of present infrared focus plane technology, the infrared focus plane size is increasing, therefore presses for the infrared camera camera lens of big visual field.Simultaneously, because the imaging performance of infrared camera and the requirement of luminous energy, the infrared camera camera lens also need possess heavy caliber.Therefore as seen, the big visual field of heavy caliber broadband is the direction of present infrared camera optical system development.

Though reflective optical system is not introduced aberration, accomplish broadband easily, be difficult to accomplish big visual field.The reflective optical system of some special construction, as " from the axle astigmatism three-mirror system that disappears " though can accomplish big visual field owing to used the high order aspheric surface mirror, difficulty of processing is very big, and this system does not have axis of reference, and the dress school is very complicated, generally seldom uses.Though refractive optical system is influenced by aberration, relatively more difficult to the broadband imaging, can realize the broadband imaging by adopting the aberration of certain means corrective system.And, therefore in a lot of occasions, have a wide range of applications because do greatly easily the refractive optical system visual field.

Summary of the invention

Purpose of the present invention will provide a kind of heavy caliber, wide visual field refraction type infrared camera optical system exactly.

Optical system of the present invention as shown in Figure 1, optical system is made up of first lens 1, second lens 2, the 3rd lens 3, the 4th lens 4, the 5th lens 5, ice chest window 6 and cold light branch colour cell 7 to the side of elephant in order from object space.

Said cold light branch colour cell 7 is that 2 μ m-3 μ m optical filters 9 and transmission wave band are that 3 μ m-4.5 μ m optical filters 10 are formed by the prism 8 that places Vacuum cooling case 13, transmission wave band

Said cold light branch colour cell 7 can be that 2 μ m-3 μ m optical filters 9 and transmission wave band are that 3 μ m-4.5 μ m optical filters 10 are formed by the transmission wave band that places Vacuum cooling case also.

When being used for the scanned infrared imaging system, as depicted in figs. 1 and 2, object space light beam from different visual fields sees through first lens 1 successively, second lens 2, the 3rd lens 3, the 4th lens 4, the 5th lens 5, ice chest window 6 enters the cold light branch colour cell 7 of Vacuum cooling case 13, divided the prism 8 of colour cell 7 by the visual field beam split by cold light again, the a branch of light of two-beam separately is 2 μ m-3 μ m optical filters 9 through the transmission wave band, another Shu Guang is to focus on two-lines array detector 11 respectively after 3 μ m-4.5 μ m optical filters 10 filter through the transmission wave band, on 12, realized two detector two wavebands scanning imagery simultaneously.

When being used for staring infrared imaging system, as shown in Figure 3, only need the prism 8 in the cold light branch colour cell is removed, the one in 2 μ m-3 μ m optical filters 9 or the 3 μ m-4.5 μ m optical filters 10 places light path.Enter the incident light of cold light branch colour cell 7, mating plate 9 or optical filter 10 filter after filtration, carry out the staring imaging of 2 μ m-3 μ m or 3 μ m-4.5 mu m wavebands on super large face battle array infrared focus plane.The difference of staring infrared imaging optical system and scanned infrared optical system is, has removed prism in the cold light branch colour cell, though optical system also can be to two wave band imagings, and can not two wave band imagings simultaneously.

The convex surface of said first lens 1 is a sphere, and concave surface is a sphere, adopts silicon materials.

The convex surface of second lens 2 is a sphere, and concave surface is a hyperboloid, adopts silicon materials.

The convex surface of the 3rd lens 3 is a sphere, and concave surface is a sphere, adopts calcium fluoride material.

The convex surface of the 4th lens 4 is a sphere, and concave surface is oblate, adopts germanium material.

Two nonreentrant surfaces of the 5th lens 5 are sphere, adopt silicon materials.

Prism 8 adopts microcrystal glass material.

Five lens of this optical system are just adopting-negative-positive structure, and the main aberration of optical system is aberration and spherical aberration, also has other aberrations such as coma, the curvature of field and astigmatism in addition.

Just adopt-negative-positive structure is for color difference eliminating and proofreaies and correct the curvature of field, is because the curvature of field and the total focal power of system are proportional.A slice lens are directly proportional for the contribution of the system's focal power product with the height of its focal power and the marginal ray by aperture diaphragm, with the 4th lens 4 is the centre that negative lens places optical system, though make that its focal power is big, but the height of marginal ray on lens is lower, lower to total focal power contribution, can improve the curvature of field.Because the size of single lens chromatic aberration is directly proportional with focal power, be directly proportional in addition, just using-negative-the just combination of structure and different materials lens with the material dispersion degree, can achromatism.

This optical system has adopted the lens of silicon, germanium, three kinds of different materials of calcium fluoride to control aberration, from left to right is respectively first silicon lens, second silicon lens, the 3rd calcium fluoride lens, the 4th germainium lens, the 5th silicon lens.For aberration, coma, spherical aberration, the astigmatism of remnants, we have adopted two secondary asphericals to eliminate.In order to reduce processing and check difficulty, secondary aspherical is positioned on the concave surface of second less silicon lens of size and the 4th germainium lens.The concave surface of second silicon lens is a hyperboloid, and the concave surface of the 4th germainium lens is oblate.

The refractive index of silicon, germanium crystal is still calculated with the variation of temperature formula analysis according to its refractive index for responsive to temperature, and its temperature changes (± 20 °) and can compensate by mobile focal plane among a small circle.± 20 ° among a small circle in, mobile focal plane can well compensate hot Jiao and move, and can not bring the deterioration of picture element.General physical construction just can realize easily that focal plane moves.Certainly, if under the indoor conditions, the temperature that controls environment can need not focusing about 20 ℃.

The advantage of this optical system is: realize heavy caliber, big visual field in infrared broadband scope, its linear field reaches 172mm, can cover the large scale infrared focal plane detector fully.Simultaneously, the entrance pupil diameter is that the heavy caliber of 150mm had both guaranteed in 2 μ m-4.5 mu m waveband scope inner optical system diffraction Aili spot sizes to have increased incident optical energy again less than pixel dimension, makes this optical system have favorable imaging quality.Simultaneously, the cold light branch colour cell of native system adopts a prism to carry out the visual field beam split, the light of two specific visual fields is reflexed on two detectors, and whole cold light branch colour cell places an ice chest, realizes the imaging simultaneously in an ice chest of shortwave, two detectors of medium wave.

Description of drawings

Fig. 1 is the structural representation of scanned infrared camera optics of the present invention system.

Among the figure: d1 is the spacing distance of first lens, 1 rear surface and second lens, 2 front surfaces;

D2 is the spacing distance of second lens, 2 rear surfaces and the 3rd lens 3 front surfaces;

D3 is the spacing distance of the 3rd lens 3 rear surfaces and the 4th lens 4 front surfaces;

D4 is the spacing distance of the 4th lens 4 rear surfaces and the 5th lens 5 front surfaces;

D5 is the spacing distance of the 5th lens 5 rear surfaces and prism drift angle.

Fig. 2 is the vertical view of Fig. 1.

Fig. 3 is for staring infrared camera optical system structure synoptic diagram.

Embodiment

According to the optical system structure of Fig. 1, we have designed footpath at a gulp, wide visual field, dual-band infrared camera optics system, and its concrete technical indicator is as follows:

Two waveband: 2 μ m-3 μ m, 3 μ m-4.5 μ m

Entrance pupil diameter: 150mm

Focal length: 410mm

F/#：2.73

Visual field: ± 12 °

Picture element is near diffraction limit.

The specific design parameter of optical system is as shown in table 1.

Table 1

Element names	Face shape	Radius-of-curvature	Thickness	At interval	Asphericity coefficient	Material	Unified
								First lens	The convex surface concave surface	154.88 140.01	25	29.53		Silicon	94 83
Second lens	The convex surface concave surface	244.3 392.57	20.17	7.68	-2.140182	Silicon	78 74
								The 3rd lens	The convex surface concave surface	154.88 135.52	13.9	18		Calcium fluoride	63 55
The 4th lens	The convex surface concave surface	526 295.5513	22.9	188.82	3.779660	Germanium	50 49
								The 5th lens	The convex surface convex surface	1414.5 -1753.9	20	105.05		Silicon	96 96
The ice chest window	Dull and stereotyped	∞	24.6			Silicon	90
								Cold light divides colour cell		∞		(25.53 apart from prism vertex angle)			90

Claims (2)

1. large caliber wide visual field two waveband refraction type infrared camera optical system comprises: five lens and cold light branch colour cell is characterized in that:

A). optical system is made up of first lens (1), second lens (2), the 3rd lens (3), the 4th lens (4), the 5th lens (5), ice chest window (6) and cold light branch colour cell (7) to the side of elephant in order from object space;

B). said cold light branch colour cell (7) is that 2 μ m-3 μ m optical filters (9) and transmission wave band are that 3 μ m-4.5 μ m optical filters (10) are formed by the prism that places Vacuum cooling case (13) (8), transmission wave band;

C). the light beam from object space sees through first lens (1), second lens (2), the 3rd lens (3), the 4th lens (4), the 5th lens (5) successively, ice chest window (6) enters the cold light branch colour cell (7) of Vacuum cooling case (13), prism (8) through cold light branch colour cell (7) is divided into two-beam, a branch of light is 2 μ m-3 μ m optical filters (9) through the transmission wave band, and another Shu Guang is 3 μ m-4.5 μ m optical filter (10) filtering imagings on the two-lines array detector respectively through the transmission wave band;

D). the convex surface of said first lens (1) is a sphere, and concave surface is a sphere, adopts silicon materials;

The convex surface of second lens (2) is a sphere, and concave surface is a hyperboloid, adopts silicon materials;

The convex surface of the 3rd lens (3) is a sphere, and concave surface is a sphere, adopts calcium fluoride material;

The convex surface of the 4th lens (4) is a sphere, and concave surface is oblate, adopts germanium material;

Two convex surfaces of the 5th lens (5) are sphere, adopt silicon materials;

Prism (8) adopts microcrystal glass material.

2. according to a kind of large caliber wide visual field two waveband refraction type infrared camera optical system of claim 1, it is characterized in that: said cold light branch colour cell (7) can be that 2 μ m-3 μ m optical filters (9) or transmission wave band are that 3 μ m-4.5 μ m optical filters (10) are formed by the transmission wave band that places Vacuum cooling case also; Enter the incident light of cold light branch colour cell (7), mating plate (9) filters after filtration, on super large face battle array infrared focus plane, carry out the staring imaging of 2 μ m-3 μ m or mating plate (10) optical filtering after filtration, on super large face battle array infrared focus plane, carry out the staring imaging of 3 μ m-4.5 μ m.

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