RU2348059C1 - Large-aperture lens - Google Patents

Abstract

FIELD: physics, optics.

SUBSTANCE: invention concerns lenses operating in long-range infrared range of wavelengths, and can be applied in thermal vision devices. Lens consists of four components, the first one being a single positive meniscus lens with concave side oriented towards image side. Second component is a single negative meniscus lens with convex side oriented towards image. Third and fourth components are single positive meniscus lenses. Third lens is oriented towards image with its convex side. Fourth lens is oriented towards image with its concave side. First and third components are made of germanium. Second and fourth components are made of zinc selenide. All optic surfaces are spherical and meet the requirement: |R₂| = |R₅|; |R₃| = |R₆| = |R₈|; |R₅| > |R₆|, where: R₂, R₃, R₅, R₆, R₈ are radii of second, third, fifth, sixth and eighth optic surfaces respectively.

EFFECT: improved manufacturability, increased focal distance and aperture ratio at high image quality.

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Description

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

Known fast lens [Russia, patent No. 2183340; G02B 13/14, 9/34; 2002 publication] containing four components along the ray:

- positive meniscus facing concavity to the image;

- concave flat lens;

- flat convex lens;

- positive meniscus convex to the subject.

This lens works in the wavelength range from 8 to 12.5 microns and all of its lenses are made of germanium with a refractive index of more than 4.

Lens Specifications:

focal length 51.14 mm relative hole 1: 1.65 field of view angle 18 deg. back focal length 45.23 mm

This lens is close in design to the claimed, but has a small focal length and relative aperture.

The closest analogue to the claimed technical solution is a fast lens [Russia, utility model certificate No. 26664; G02B 13/14, 9/34, 9/56, 3/02, publication 2002], containing four components, the first of which (along the beam) is the positive meniscus facing the concavity to the image, the second is the negative meniscus facing concavity to the object, the third and fourth - positive menisci, convex to the object. The second, concave surface of the first meniscus is aspherical and the following relations hold:

| R ₅ | <| R ₆ |,

d ₃ ≤0.01R ₅ ,

where R ₅ is the radius of the fifth optical surface;

R ₆ is the radius of the sixth optical surface;

d ₃ is the thickness of the third component.

In addition, there is equality:

R ₅ / R ₆ = 0.1192

This lens works in the wavelength range from 8 to 12.5 microns and all of its lenses are made of germanium with a refractive index of more than 4.

Lens Specifications:

focal length 62 mm relative hole 1: 2 field of view angle 16 deg. back focal length 52.78 mm

This lens is close in design to the claimed one, however, it has a small focal length and relative aperture, as well as insufficient manufacturability, as it contains an aspherical optical surface; in addition, all the radii of the optical surfaces are different, which does not allow the unification of the reference and working test glasses and the processing tool.

The objective of the invention is the creation of a fast lens with improved performance and high adaptability.

The technical result is an increase in manufacturability and an increase in focal length and relative aperture with high image quality.

This is achieved due to the fact that the fast lens consists of four components described along the rays, moreover: the first component is a single positive meniscus, facing concavity to the image; the second component is a single negative meniscus convex to the image; the third and fourth components are single positive menisci. The third component is convex to the image. The fourth component is the concavity of the image. The first and fourth components are made of Germany. The second and third components are made of zinc selenide. All optical surfaces are spherical and the following conditions are met:

| R ₂ | = | R ₅ |

| R ₃ | = | R ₆ | = | R ₈ |

| R ₅ |> | R ₆ |,

where: R ₂ , R ₃ , R ₅ , R ₆ , R ₈ are the radii of the second, third, fifth, sixth, eighth optical surfaces, respectively.

In addition, the thickness along the axis of the second component may be equal to the thickness along the axis of the third component or thickness along the axis of the fourth component. An embodiment is possible when the thicknesses along the axes of the second, third and fourth components are equal to each other. Or equal thickness along the axes of the third and fourth components. In addition, the thickness along the axis of the third component can be more than 0.015 in magnitude of the radius of the fifth optical surface.

The drawing shows an optical diagram of the proposed aperture lens.

A high-speed lens consists of four components along the rays: the first component is a single positive meniscus 1, facing concavity to the image, the second component is a single negative meniscus 2, convex to the image, the third component is a single positive meniscus 3, convex to the image, and the fourth component - a single positive meniscus 4, facing concavity to the image. Behind the meniscus 4, one or more plane-parallel plates can be located.

The proposed optical system works like a lens collecting from infinity.

The lens works as follows: the light flux from an object located at infinity enters the lens, where it passes through lenses 1, 2, 3, 4 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, an aperture lens is calculated, corrected in the spectral range from 8 to 12.5 microns. Its design parameters are given in table 1.

Characteristics of the calculated lens:

focal length 130.03 mm relative hole 1: 1,08 field of view angle 5 deg. 20 minutes. back focal length 25.07 mm

the entrance pupil coincides with the first surface. In the calculated lens, the thickness of the third component is equal to 0.0246 modulo the radius of the fifth optical surface (see Table 1).

Table 2 shows the aberrations for a wavelength of 10 μm of the calculated aperture lens.

Table 1 Radius mm Thickness mm Material Refractive index for λ = 10 μm Light diameter mm R ₁ = 186.64 120 d ₁ = 10 Ge 4,0024 R ₂ = 272.3 116.8 d ₂ = 73.4 one R ₃ = 116.14 77.9 d ₃ = 6.7 Znse 2,4067 R ₄ = -418.8 80 d ₄ = 10.7 one R ₅ = -272.3 81.5 d ₅ = 6.7 Znse 2,4067 R ₆ = 116.14 82 d ₆ = 39.9 one R ₇ = 93.11 57.7 d ₇ = 6.7 Ge 4,0024 R ₈ = 116.14 54.5 d ₈ = 20 R ₉ = ∞ 40 d ₉ = 1 Ge 4,0024 R ₁₀ = ∞ 40

table 2 Type of aberration The amount of aberration of the proposed lens (no more) Transverse spherical aberration for a point on the axis with a relative aperture of 1: 1.08 0.009 mm Transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 5 deg. 12 min 0.004 mm Transverse aberration of a wide inclined beam in a sagittal section for the field of view 2W = 5 deg. 12 min 0.0048 mm The meridional astigmatic segment X ' _m for the field of view 2W = 5 deg. 12 min -0.021 mm Sagittal astigmatic segment X ' _s for the field of view 2W = 5 deg. 12 min -0.032 mm Distortion for the field of view 2W = 5 deg. 12 min - 0,049%

The proposed lens contains only spherical optical surfaces and there is equality of the radii of the five spherical optical surfaces, which provides it with high manufacturability. In addition, the proposed lens has a focal length of 130 mm, a relative aperture of 1: 1.08 and high image quality, which follows from table 2.

Thus, as a result of the proposed solution, a technical result is obtained: a high-aperture lens is created for the spectral range from 8 to 12.5 microns with high adaptability and increased focal length and relative aperture with high image quality.

Claims (1)

A fast lens consisting of four components along the rays: the first component is a single positive meniscus, convex to the image, the second component is a single negative meniscus, convex to the image, the third and fourth components are single positive menisci, with the fourth component facing concavity to image, in addition, the first and fourth components are made of germanium, characterized in that the third component is convex to the image, all opt The surfaces are spherical, the second and third components are made of zinc selenide and the conditions are met
| R ₂ | = | R ₅ |,
| R ₃ | = | R ₆ | = | R ₈ |,
| R ₅ |> | R ₆ |,
where R ₂ , R ₃ , R ₅ , R ₆ , R ₈ are the radii of the second, third, fifth, sixth, eighth optical surfaces, respectively.