RU2630194C1 - Large-aperture lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: lens consists of four components along the ray path. The first component is a single positive meniscus which concave side faces the image, the second component is a single negative meniscus which convex side faces the image, the third component is a single positive meniscus which convex side faces the image, and the fourth component is a single positive meniscus which concave surface faces the image. The first and fourth components are made of germanium, while the second and third components are made of zinc selenide. All optical surfaces are spherical. The following ratios are fulfiled: |R₅|>|R₆|, |R₅|≤|R₂|, |R₃|≥|R₈|, where R₂, R₃, R₅, R₆, R₈ - radii of the second, third, fifth, sixth and eighth optical surfaces, respectively. |R₃| may be greater or less than |R₆|.

EFFECT: increased aperture ratio with high image quality.

3 cl, 1 dwg, 3 tbl

Description

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

Known fast lens described in patent RU No. 2183340, IPC G02B 13/14, 9/34; publ. 2002, containing four components along the rays, the first of which is a positive meniscus facing concavity to the image, the second is a concave plane lens facing the image, the third is a positive convex lens facing the object, and the fourth is the positive meniscus bulge to the subject. This lens works in the wavelength range from 8 to 12.5 μm and all of its lenses are made of germanium with a refractive index of more than 4. Moreover, the focal length of the lens is 51.14 mm, the relative aperture is 1: 1.65, and the field of view angle is 18 degrees, rear focal segment 45.23 mm. This lens is close in design to the claimed invention, however, has a small relative aperture.

The closest analogue to the claimed technical solution is a fast lens described in patent RU No. 2348059; IPC G02B 9/34, 13/14, publ. 02/27/2009, 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 component is a single positive meniscus, convex to the image, and the fourth component - a single positive meniscus facing concavity to the image, in addition, the first and fourth components are made of germanium, all optical surfaces are osilnogo lens are spherical, second and third components are made of zinc selenide and conditions occur:

| R ₂ | = | R ₅ |

| R ₃ | = | R ₆ | = | R ₈ |

| R ₅ |> | R ₆ |

where R ₂ is the radius of the second optical surface;

R ₃ is the radius of the third optical surface;

R ₅ is the radius of the fifth optical surface;

R ₆ is the radius of the sixth optical surface;

R ₈ is the radius of the eighth optical surface.

This lens works in the wavelength range from 8 to 12.5 microns. The focal length of the lens is 130.03 mm, the relative aperture is 1: 1.08, the angle of view is 5 degrees 20 minutes, the rear focal length is 25.07 mm, but it has a small relative aperture.

The task of the invention is the creation of a fast lens with improved performance.

The technical result is an increase in the relative aperture with high image quality.

This is achieved by the fact that in a fast lens consisting of four components along the rays, the first of them is a single positive meniscus facing the concavity to the image, the second is the single negative meniscus facing the convex to the image, and the third is the single positive meniscus facing the convex to image, and the fourth component is a single positive meniscus facing concavity to the image, in addition, the first and fourth components are made of germanium, all optical surfaces of the aperture Nogo lens are spherical, second and third components are made of zinc selenide and the relations

| R ₅ |> | R ₆ |

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

R ₆ is the radius of the sixth optical surface,

differs in that there are relations

| R ₅ | ≤ | R ₂ |

| R ₃ | ≥ | R ₈ |

where R ₂ is the radius of the second optical surface,

R ₃ is the radius of the third optical surface,

R ₈ is the radius of the eighth optical surface.

In addition, in a fast lens | R ₃ | may be more or less | R ₆ |.

The figure shows the optical scheme of a fast lens.

A fast 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 is a single positive meniscus 4, facing concavity to the image. Behind the meniscus 4 is a plane-parallel plate 5, which may also be a protective glass.

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 the lenses 1, 2, 3, 4, plane-parallel plate 5 and forms an image of the object in the plane of the best setting in which the optical radiation receiver is installed (not shown).

In accordance with the proposed solution, two versions of the fast lens design are calculated, corrected in the spectral range from 8 to 12.5 μm.

The design parameters of the lens according to the first embodiment are shown in table 1.

The characteristics of the calculated lens according to the first embodiment:

focal length 130.14 mm relative hole 1: 0.978 field of view angle 5 deg 20 min back focal length 1,765 mm back focal length excluding plane-parallel plate 46.515 mm entrance pupil coincides with the first surface

In the proposed first version of the lens, the following relationships occur:

| R ₃ | = | R ₈ | = 116.14,

266.7 = | R ₅ |> | R ₆ | = 115.88,

266.7 = | R ₅ | <| R ₂ | = 272.3,

116.14 = | R ₃ |> | R ₆ | = 115.88.

The characteristics of the calculated lens according to the second embodiment:

focal length 130 mm relative hole 1: 1 field of view angle 5 deg 20 min back focal length 1,027 mm back focal length excluding plane-parallel plate 46.277 mm entrance pupil coincides with the first surface

In the proposed second version of the lens, the following relations occur:

| R ₂ | = | R ₅ | = 272.3,

272.3 = | R ₅ |> | R ₆ | = 116.41,

116.14 = | R ₃ | <| R ₆ | = 116.41,

116.14 = | R ₃ |> | R ₈ | = 115.35.

The design parameters of the lens according to the second embodiment are shown in table 2.

In the table. 3 shows aberrations for a wavelength of 10 μm of the proposed embodiments of the fast lens.

Thus, as a result of the proposed solutions in two options, a technical result is obtained: two fast lenses are created according to the first and second options for the spectral range from 8 to 12.5 μm with an increased relative aperture with high image quality.

Claims (12)

1. Aperture lens, consisting of four components along the rays, the first of which is a single positive meniscus, convex to the image, the second is a negative negative meniscus, convex to the image, the third is a single positive meniscus, convex to the image, and the fourth component - a single positive meniscus facing concavity to the image, in addition, the first and fourth components are made of germanium, all optical surfaces of the fast lens are made spherical, the second and third components are made of zinc selenide and the relations | R ₅ |> | R ₆ |, where R ₅ is the radius of the fifth optical surface, R ₆ is the radius of the sixth optical surface, characterized in that the relations | R ₅ | ≤ | R ₂ |, | R ₃ | ≥ | R ₈ |, where R ₂ is the radius of the second optical surface, R ₃ is the radius of the third optical surface, R ₈ is the radius of the eighth optical surface. 2. A fast lens according to claim 1, in which | R ₃ | more | R ₆ |. 3. A fast lens according to claim 1, in which | R ₃ | less than | R ₆ |.

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