RU126479U1 - LIGHT LIGHT - Google Patents

Abstract

A fast lens consisting of two successively single positive menisci convex toward the object made of germanium, characterized in that all optical surfaces are spherical and have the relations 0 <d <0.2f '; 2 <R / f '<4,5; 0,5 <R / f' <1; 4 <R / f '<8; 0,7 <R / f' <2, where R, R, R, R are the radii of curvature of the first, second, third and fourth optical surfaces; d is the air gap between two lenses; f 'is the focal length of the entire lens.

Description

The proposed utility model relates to optical instrumentation, namely to lenses operating in the far PC-wavelength range, and can be used in thermal imaging devices.

Known two-lens with an air gap for the spectral range from 8 to 14 microns according to the patent of Germany No. 1813085; IPC G02B 13/14; NKI 42h 3/01, publ. 1973, which contains two components along the rays, the first of which is a single biconvex positive lens, the second is a single negative lens. The lenses are made of different materials, moreover, the refractive index of the positive lens material is less than the refractive index of the negative lens material, the Abbe dispersion coefficient of the positive lens material is greater than the Abbe dispersion coefficient of the negative lens material. However, the lens has an insufficient relative aperture of 1: 2.5. In addition, the negative lens is made of zinc sulfide, and zinc sulfide in the spectral range from 8 to 14 μm has a worse transmittance compared to germanium and zinc selenide.

The closest analogue to the claimed technical solution is a lens (US patent No. 399992078; IPC G02B 3/00; NKI 350/2, 350/231; publ. 1976), consisting of front and rear simple positive lenses made of Germany moreover, these elements are spaced apart from each other along the axis at a distance from 0.8F to 1.2F, where F is the equivalent focal length of the entire lens; moreover, each lens can be made either in the form of a convex plane convex to the object, or a positive meniscus convex to the object, and the first along the rays of the surface of the first and second lenses are made with radii of curvature greater than 5F and 2F, respectively, smaller than radii of curvature of the rear surfaces of said respective lenses. In addition, the radius of the rear surface of the front lens and the radius of the rear surface of the rear lens can be greater than 50F, the thickness along the axis of the front and rear lenses can be less than 0.05F, the rear focal length of the lens can be more than 0.5F and less than 2F, the rear surface of the front the lens can be aspherical, and in two versions of a specific implementation of this lens described in the description of the US patent, the ratios R ₁ / R ₂ and R ₃ / R ₄ are from 0 to 0.1 inclusive. This lens is designed for a wavelength range from 8 to 14 microns, but it has an insufficient relative aperture of 1: 1, large longitudinal dimensions (the distance from the first surface to the focus is at least 1.3F; as follows from the claims). Both versions of a specific implementation of this lens have an aspherical surface on the second surface of the first lens, and it is known (“Computing Optics”, reference, edited by M. M. Rusinov, Leningrad, “Mechanical Engineering”, Leningrad Branch, 1984, p. 383, 384 , 385) that for large values of the ratio of the distance between two lenses to the focal length of the entire lens for a two-lens system from Germany, an increase in aperture is prevented by irreparable third-order spherical aberration that occurs on the last plane (and and close to the plane) of the lens surface. The elimination of this aberration and the increase in the aperture ratio of the two-lens system can be achieved by asphering one of the surfaces of the first lens. It follows that the area of positive solutions for this lens (with high image quality) can be obtained only with the use of aspherics, which reduces the manufacturability of this lens.

The objective of the claimed utility model is to create a fast lens with improved performance.

The technical result is an increase in the relative aperture, a decrease in dimensions and an increase in manufacturability with high image quality.

This is achieved by the fact that in a fast lens consisting of two successively single positive menisci, convex to the object, made of germanium, in contrast to the known, all optical surfaces are spherical and have the following relationships:

0 <d _at <0.2f ';

2 <R ₁ / f '<4.5;

0.5 <R ₃ / f '<1;

4 <R ₂ / f '<8;

0.7 <R ₄ / f '<2;

where: R ₁ , R ₂ , R ₃ , R _{4 -} are the radii of curvature of the first, second, third and fourth optical surfaces;

d _in - the air gap between the two lenses;

f 'is the focal length of the entire lens.

In FIG. The optical scheme of the proposed lens is presented.

A fast lens (Fig.) Consists of two single positive menisci 1 and 2 located along the rays, convex to the object. The entrance pupil or aperture diaphragm coincides with the first surface, but can be located in another place.

The proposed optical system works as a lens collecting from infinity, i.e. the luminous flux from an object located at infinity falls into the lens, where it passes through lenses 1 and 2 and forms an image of the object in the plane of the best setup in which the optical radiation receiver (not shown) is installed.

In accordance with the proposed solution, a specific lens is calculated, corrected in the spectral range from 8 to 12.5 microns.

The design parameters of the lens are shown in table 1.

Characteristics of the calculated lens:

focal length f ' 14.51 mm relative hole 1: 0.8 field of view angle 2.8 deg. back focal length 12.41 mm

In the calculated lens, the following conditions are met:

0 <d _at <0.2f '; d _B = 0.01034f '; 2 <R ₁ / f '<4.5; R ₁ / f '= 3.882; 0.5 <R ₃ / f '<l; R ₃ / f '= 0.779; 4 <R ₂ / f '<8; R ₂ / f '= 5.757; 0.7 <R ₄ / f '<2; R ₄ / f '= 0.844;

Table 1 Radii, mm Thickness mm Material Refractive index for λ = 4 μm Light diameter mm R ₁ = 56.34 eighteen d ₁ = 1.3 Ge 4,0024 R ₂ = 83.55 eighteen d ₂ = 0.15 one R ₃ = 11.3 17 d ₃ = 1.8 Ge 4,0024 R ₄ = 12.25 16

In the table. 2 shows aberrations for a wavelength of 10 μm of the proposed aperture lens with a relative aperture of 1: 0.8 and an angular field in the space of objects 2W = 2.8 deg.

The proposed lens has a distance from the first surface to the image plane of 1.078f ', which is much smaller than the dimensions of the closest analogue, an increased relative aperture of 1: 0.8, increased manufacturability (since it does not contain an aspherical surface) and high image quality, which follows from the table . 2.

Thus, a technical result was achieved - a high-aperture lens was created with a higher relative aperture, reduced dimensions and increased manufacturability with high image quality.

table 2 Type of aberration Lens aberration value, no more Transverse spherical aberration for a point on the axis 0.0129 mm Transverse aberration of a wide inclined beam in the meridional section 0.00457 mm Transverse aberration of a wide inclined beam in a sagittal section 0.00852 mm Meridional astigmatic segment X ' _m -0.0153 mm Sagittal astigmatic segment X ' _s -0.0055 mm Distortion 0.0052%

Claims (1)

A fast lens consisting of two successively single positive menisci convex towards the object made of germanium, characterized in that all optical surfaces are made spherical and have the ratio 0 <d _at <0.2f '; 2 <R ₁ / f '<4.5; 0.5 <R ₃ / f '<1; 4 <R ₂ / f '<8; 0.7 <R ₄ / f '<2, where R ₁ , R ₂ , R ₃ , R ₄ are the radii of curvature of the first, second, third and fourth optical surfaces; d _in - the air gap between the two lenses; f 'is the focal length of the entire lens.

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