RU2351967C1 - Fast lens - Google Patents

Abstract

FIELD: physics; optics.

SUBSTANCE: lens consists of four components. The first component - positive and consisting from single convexo-convex and plano-concave lenses. The second - single positive meniscus converted by protuberant surface to image. The third - positive, conglutinated from convexo-convex and plano-concave lenses. The fourth - converted by incurvation to image plus meniscus. In the first builder the radius of curvature of the second surface of convexo-convex lens on the module is bigger than radius of curvature of the first surface of the subzero lens, and the radius of curvature of protuberant surface of meniscus of the second component is equal to radius of curvature of the first surface of the subzero lens of the first builder. The convexo-convex lenses of the first and third components are executed symmetrical and from one material.

EFFECT: angular aperture increase at high quality of image and pinch of adaptability to manufacture of manufacturing of objective at the expense of equality of curvature of a part of optical surfaces and replacement of spherical surfaces by the flat.

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Description

The invention relates to optical instrumentation and can be used in various devices, in particular in cameras operating with a receiving matrix, for example, in the infrared wavelength range.

Known fast photographic lens (SU 1691806; G02B 9/36, 11/20; publ. 1991), containing four components. The first component along the rays is the positive meniscus, facing concavity to the image. The second is the negative meniscus facing concavity to the image and consisting of glued positive and negative menisci facing concavity to the image. The third component is the negative meniscus, facing concavity to the subject. The fourth component is a positive one, consisting of a negative meniscus glued together, turned concave to the image, and a biconvex lens. The aperture diaphragm is located between the second and third components.

Lens Specifications:

focal length 52 mm relative hole 1: 1.9 field of view angle 45 °

This lens has a small relative aperture.

The closest analogue to the claimed technical solution is a fast lens (SU 1527604; G02B 9/62, 11/32; publ. 1989), containing six lenses in four components. The first of them along the rays is positive, consisting of a single biconvex and biconcave lens, the second is a biconvex lens, the third is a positive meniscus glued from a biconvex and biconcave lenses, and the fourth is a negative meniscus with a concavity facing the image.

The distance d ₂ between the first and second components satisfies the condition:

0.5 f '<d ₂ <f',

where f 'is the focal length of the lens.

The radii of curvature of the second R ₂ surface of the biconvex lens of the first component and the first surface R _{3 of} its biconcave lens satisfy the condition:

| R ₃ | <| R ₂ |.

The lens operates in the wavelength range from 700 to 900 nm.

Lens Specifications:

focal length 250 mm relative hole 1: 1.25 field of view angle 5 °

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

The technical result of the claimed invention is to increase the relative aperture with high image quality and increase the manufacturability of the lens due to the equality of the curvature of part of the optical surfaces and the replacement of spherical surfaces with flat ones.

This is achieved by the fact that in a fast lens consisting of four components, the first component along the rays - positive and consisting of single biconvex and negative lenses, the second component - single positive lenses, the third component - positive, glued from biconvex and negative lenses and fourth component - turned concavity to the image of the meniscus, in which the radius of curvature of the convex surface is greater than the radius of curvature of the concave surface, while in the first component since the curvature of the second surface of the biconvex lens is larger in absolute value than the radius of curvature of the first surface of the negative lens, in contrast to the known one, the negative lenses of the first and third components along the rays are concave planes, the second component is made in the form of a positive meniscus with a convex surface facing the image, and its radius the curvature is equal to the radius of curvature of the first surface of the negative lens of the first component, the biconvex lenses of the first and third components are each symmetrical and from one Container material, and a fourth component - Meniscus - made positive.

In the lens, the distance d ₄ between the first and second components can satisfy the condition:

F '<d ₄ <1.5f',

where f 'is the focal length of the lens.

The drawing shows an optical diagram of the proposed lens. A fast lens consists of six lenses in four components. The first component along the rays is positive, consists of single biconvex 1 and concave flat lens 2; in it, the radius of curvature of the second surface R _{2 of the} biconvex lens 1 is larger in magnitude than the radius of curvature of the first surface R _{3 of the} concave plane lens 2. The second component is a single positive meniscus 3 facing the convex surface of the image, and its radius of curvature R ₆ is equal to the radius of curvature of the first surface R ₃ concave lenses 2 of the first component. The third component is positive, glued from a biconvex lens 4 and a concave plane lens 5. The biconvex lenses of the first and third components 1 and 4 are each symmetrical, i.e. R ₁ = R ₂ and R ₇ = R ₈ , and from one material, in particular lanthanum glass. The refractive index of the biconvex lenses of the first and third components is more than 1.63 and less than 1.71 for the line e. The dispersion coefficient of the glass for the line e is more than 56.7 and less than 71. The fourth component is the meniscus 6, which has a concavity facing the image, whose radius of curvature is convex surface R ₁₀ greater than the radius of curvature R ₁₁ concave surface. The meniscus 6 is made positive by increasing its thickness d ₁₀ .

Here, for the meniscus 6, the well-known formula of a lens of finite thickness is used ("The Handbook of the Designer of Optical-Mechanical Devices", edited by M. Ya. Kruger and Panov VA, L., publishing house "Engineering", 1968, p. 111 ), connecting the focal length of the lens f ' ₄ , its refractive index n, the radii of curvature R ₁₀ and the second R ₁₁ optical surfaces and its thickness d ₁₀ :

1 / f ' ₄ = (n-1) · (1 / R ₁₀ -1 / R ₁₁ ) + (n-1) ² _· d ₁₀ / (n · R ₁₀ · R ₁₁ ).

From this formula it follows that with an increase in the thickness d _{10 of the} negative meniscus with a convex radius of the first optical surface R ₁₀ and concave R _{11 of the} second optical surface with a certain thickness d ₁₀ , the meniscus focal length becomes positive. At the same time, the aberrations of the entire lens are reduced, including such a positive meniscus, in particular, the fourth Seidel sum, which makes it possible to increase the relative aperture of the lens. The increase in the relative aperture of the lens also contributes to the fact that the meniscus 6 is now an additional positive component. Behind the meniscus 6, a light filter and one or more plane-parallel plates can be located. The distance d ₄ between the first and second components satisfies the condition:

f '<d ₄ <1.5f'.

The proposed optical system works like a lens collecting from infinity. The luminous flux from an object located at infinity enters the lens, where it passes through lenses 1, 2, 3, 4, 5, 6 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, the design of an aperture lens, corrected in the spectral range from 650 to 900 nm, was calculated. Its design parameters are given in table 1.

Table 1 Radius mm Thickness mm Glass mark Refractive index n _e Coeff. variance v _e Light diameter mm R ₁ = 165.96 60 d ₁ = 8.5 STK3 1.662237 57.09 R ₂ = -165.96 59.6 d ₂ = 14.4 one R ₃ = -83.37 53,2 d ₃ = 4,5 TF5 1.761712 27.32 R ₄ = ∞ 53,4 d ₄ = 74.5 one R ₅ = -1000 57.8 d ₅ = 8 LK3 1,489118 69.87 R ₆ = -83.37 58 d ₆ = 14.7 one R ₇ = 69.5 52.7 d ₇ = 14.1 STK3 1.662237 57.09 R ₈ = -69.5 50.9 d ₈ = 4.3 TF5 1.761712 27.32 R ₉ = ∞ 47.4 d ₉ = 1.5 one R ₁₀ = 31.99 41.3 d ₁₀ = 21.2 K8 1,518294 63.83 R ₁₁ = 25.82 24.8 d ₁₁ = 6 one R _l2 = ∞ 22 d ₁₂ = 1.2 KC13 1,525 63.83 R ₁₃ = ∞ 22 d ₁₃ = 12.26 one R ₁₄ = ∞ 10 d ₁₄ = 1 K8 1,518294 63.83 R ₁₅ = ∞ 10

Characteristics of the calculated lens:

focal length 67.65 mm relative hole 1: 1,1 field of view angle 5 ° 11 ' back focal length 3.5 mm aperture diaphragm located behind lens 2 in the distance 62.8 mm.

In the calculated lens, the condition d ₄ = 1,101 f 'is fulfilled, where f' is the focal length of the entire lens for a wavelength of 766.49 nm. And the focal length of the fourth component is meniscus 6 for a wavelength of 766.49 nm f ' ₄ = 1616.4 mm, i.e. meniscus 6 is positive. The biconvex lens of the third component is made of STKZ lanthanum glass of the group of superheavy crowns.

Table 2 shows the aberrations for a wavelength of 766.49 nm of the calculated lens.

table 2 Type of aberration Aberration value of the calculated lens, not more than Transverse spherical aberration for a point on the axis with a relative aperture of 1: 1,1 0.008 mm Transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 5 ° 11 '. 0.013 mm Transverse aberration of a wide inclined beam in a sagittal section for the field of view 2W = 5 ° 11 ' 0.014 mm The meridional astigmatic segment X ' _m for the field of view 2W = 5 ° 11' - 0,025 mm Sagittal astigmatic segment X ' _s for the field of view 2W = 5 ° 11' - 0.0264 mm Distortion for the field of view 2W = 5 ° 11 ' - 0.25%

Replacing spherical optical surfaces with planar ones allows them to be processed using a tool available in optical production and controlled on an interferometer without using test glasses. The introduction of optical surfaces with equal radii of curvature into the lens provides a great unification of test glasses and a processing tool. All this ensures the achievement of a technical result - an increase in manufacturability (there are two flat optical surfaces in the lens and the equality in modulus of the pairwise radii of six spherical surfaces). In addition, the proposed fast lens for the spectral range from 650 to 900 nm has a high relative aperture of 1: 1.1 with high image quality, which follows from table 2.

Claims (2)

1. A fast lens consisting of four components, the first component along the rays of the positive and consisting of single biconvex and negative lenses, the second component is a single positive convex lens, the third component is positive, glued from biconvex and negative lenses, the fourth component is concave to the image of the meniscus, in which the radius of curvature of the convex surface is greater than the radius of curvature of the concave surface, while in the first component the radius of curvature of the second surface These biconvex lenses are larger in magnitude than the radius of curvature of the first surface of the negative lens, characterized in that the negative lenses of the first and third components along the rays are concave, the second component is made in the form of a positive meniscus with a convex surface facing the image, and its radius of curvature is equal to the radius of curvature the first surface of the negative lens of the first component, the biconvex lenses of the first and third components are each symmetrical and from the same material, and the fourth t - Meniscus - made positive. 2. A fast lens according to claim 1, characterized in that the distance d ₄ between the first and second components satisfies the condition
f '<d ₄ <1,5f',
where f 'is the focal length of the lens.