RU2396581C1 - Large-aperture lens - Google Patents

Abstract

FIELD: physics. ^ SUBSTANCE: lens consists of four components. The first component is made from separate biconvex and concave-plane lenses. The second component is a separate convex-plane lens whose flat side faces the image. The third component is a positive lens made from a biconvex and a biconcave lens. The fourth component is a positive meniscus whose concave side faces the image and whose radius of curvature of the convex surface is greater than the radius of curvature of the concave surface. In the first component, the modulus of the radius of curvature of the second surface of biconvex lens is greater than the radius of curvature of the first surface of the concave-plane lens. Each biconvex lens is symmetrical. The refraction index of the fourth component is greater than 1.64 and less than 1.9 for line e. The refraction index of the biconvex lens of the fourth component is greater than 1.56 and less than 1.63 for line e and is less than the refraction index of the biconvex lens of the first component. The following condition is satisfied: 0.5f' <d4<f', where: f' is focal distance of the lens; d4 is distance between the first and second components. ^ EFFECT: wider angular field of view and miniaturisation with high image quality. ^ 2 cl, 1 dwg, 2 tbl

Description

The present 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 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 single biconvex and biconcave lenses, 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 whose radius of curvature is convex more radius of curvature of the concave surface. The modules of 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.

The aperture diaphragm is located between the first and second components. Lens Specifications:

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

This lens has a small relative aperture and angular field of view.

The closest analogue to the claimed technical solution is a fast lens (RF Patent No. 2351967; G02B 9/60, 11/30, 13/14; publ. 2009), containing six lenses in four components. The first one along the rays is positive, consisting of a single biconvex and concave plane lens, while in the first component the radius of curvature of the second surface of the biconvex lens is greater in magnitude than the radius of curvature of the first surface of the negative lens, the second component is the positive meniscus with the convex surface facing the image, and its radius of curvature is equal to the radius of curvature of the first surface of the negative lens of the first component, the third is positive, glued from a biconvex and concave plane lens, four the fifth is the positive meniscus facing concavity to the image in which the radius of curvature of the convex surface is greater than the radius of curvature of the concave surface, and each biconvex lens in the first and third components is made symmetrical and from the same material. 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.

In addition, the refractive index of the material of the fourth component, the positive meniscus, is 1.518294 for the line e, and the refractive index of the material of the biconvex lens of the third component is 1.662237 for the line e and the refractive index of the material of the positive meniscus, the second component, is 1.489118 for the line e .

The lens operates in the wavelength range from 650 to 900 nm. The aperture diaphragm is located behind the concave plane lens of the first component at a distance of 62.8 mm. Lens Specifications:

focal length 67.65 mm relative hole 1: 1,1 field of view angle 5 ° 11 ' back focal length 3.5 mm

The ratio of the distance from the first optical surface to the back focus to the focal length of the entire lens is 2.804.

By design, the lens is close to the claimed one, however, it has a small angular field of view and a large ratio of the distance from the first optical surface to the back focus to the focal length of the entire lens, which increases the longitudinal dimensions of the entire lens structure.

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

The technical result of the claimed invention is an increase in the angular field of view and a decrease in size with high image quality.

This is achieved by the fact that in a fast lens consisting of four components, the first of which is positive along the rays and is made of single biconvex and concave flat lenses, the second component is a single positive lens, the third component is positive, glued from biconvex and negative lenses, the fourth component is the positive meniscus turned by the concavity to the image, whose modulus of radius of curvature of the convex surface is greater than the modulus of radius of curvature of the concave surface, while in the first On the other hand, the radius of curvature of the second surface of the biconvex lens is larger in magnitude than the radius of curvature of the first surface of the negative lens, and the biconvex lenses of the first and third components are each symmetrical, unlike the known second component, they are made in the form of a plano-convex lens, the negative lens of the third component is biconcave, the refractive index of the fourth component - more than 1.64 and less than 1.9 for the line e, the refractive index of the biconvex lens of the third component is more than 1.56 and less than 1.63 d For line e and less than the refractive index of the biconvex lens of the first component, the condition holds:

0.5f '<d ₄ <f',

where: f 'is the focal length of the lens;

d ₄ is the distance between the first and second components.

In addition, in the lens, the refractive index of the second component, a plano-convex lens, can be more than 1.5 and less than 1.87 for line e.

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 - positive, consists of a single biconvex lens 1, made symmetrical with equal radii of curvature of the first and second surfaces | R ₁ | = | R ₂ | and a concave plane lens 2, and the radius of curvature modulus of the second surface R _{2 of the} biconvex lens 1 is greater than the radius of curvature modulus of the first surface R _{3 of the} concave plane lens 2. The second component is made in the form of a plano-convex lens 3 facing the image to the plane. The third component is positive, glued from a biconvex lens 4 and a biconcave lens 5. The biconvex lens 4 is symmetrical with equal radii of curvature of both surfaces | R ₇ | = | R ₈ |. The fourth component is the meniscus 6 turned by the concavity to the image, in which the radius of curvature of the convex surface R _{10 is} greater than the radius of curvature R _{11 of the} concave surface. The meniscus 6 is made positive by increasing its thickness d ₁₀ and the refractive index of the material — lanthanum glass of the CTK19 superheavy crown group. Behind the meniscus 6, a light filter and one or more plane-parallel plates can be located.

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. variances ν _e Light diameter mm R ₁ = 79.62 48 d ₁ = 10.1 STK3 1.662237 57.09 R ₂ = -79.62 47.4 d ₂ = 5, l one R ₃ = -55.85 43,2 d ₃ = 3.8 TF5 1.761712 27.32 R ₄ = ∞ 42.5 d ₄ = 48.0b one R ₅ = ∞ 34.5 d ₅ = 7 K8 1,518294 63.83 R ₆ = -51.29 34 d ₆ = 0.5 one R ₇ = 43.75 30.5 d ₇ = 11 TK14 1,615506 60.34 R ₈ = -43.75 26.6 d ₈ = 3.8 TF5 1.761712 27.32 R ₉ = 254.1 23,4 d ₉ = 1,2 one R ₁₀ = 18.793 20.5 d ₁₀ = 6 STK19 1,747647 50.21 R ₁₁ = 16,444 16 d ₁₁ = 5 one R ₁₂ = ∞ fifteen d ₁₂ = 1.2 KC13 1,525 63.83 R ₁₃ = ∞ fifteen d ₁₃ = 6.28 one R _l4 = ∞ 10,2 d ₁₄ = 1 K8 1,518294 63.83 R ₁₅ = ∞ 10,2

Characteristics of the calculated lens:

focal length 52.05 mm relative hole 1: 1,08 field of view angle 8 ° 40 ' back focal length 3.52 mm

the aperture diaphragm coincides with the first optical surface of the lens 3, but can be located in another place.

In the calculated lens, the condition d ₄ =, 9233f 'is fulfilled, where: f' is the focal length of the entire lens for a wavelength of 766.49 nm. The focal length of the fourth component is meniscus 6 for a wavelength of 766.49 nm f ' ₄ = 2189.37 mm, i.e. the meniscus 6 is positive and made of CTK19 lanthanum glass of the group of superheavy crowns with a refractive index of 1.747647 for the e line. The biconvex lens of the third component 4 is made of glass TK14 of the heavy crown group with a refractive index of 1.615506 for the line e and less than the refractive index of the biconvex lens of the first component 1.662237 made of STKZ lanthanum glass of the group of superheavy crowns. Flat-convex lens - the second component is made of glass from a group of crowns with a refractive index of 1.518294 for line e.

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

The proposed lens has an angular field of view 2W = 8 ° 40 ', which is 67% more than the angular field of view of the closest analogue; the ratio of the distance from the first optical surface to the back focus to the focal length of the entire lens is 2.18; and high image quality, which follows from table.2. All this ensures the achievement of a technical result — an increase in the angular field of view and a decrease in the ratio of the distance from the first optical surface to the back focus to the focal length of the entire lens with high image quality.

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: 1.08 0.017 mm Transverse aberration of a wide inclined beam in the meridional section for the field of view 2W = 8 ° 40 ' 0.021 mm Transverse aberration of a wide inclined beam in a sagittal section for the field of view 2W = 8 ° 40 ' 0.025 mm Meridional astigmatic segment X ' _m for the field of view 2W = 8 ° 40' -0.05 mm Sagittal astigmatic segment X ' _s for the field of view 2W = 8 ° 40' -0.071 mm Distortion for the field of view 2W = 8 ° 40 ' -0.29%

Claims (2)

1. A fast lens consisting of four components, the first of which is positive along the rays and is made of single biconvex and concave planes, the second component is a single positive lens, the third component is positive, bonded from biconvex and negative lenses, the fourth component is reversed concavity to the image is a positive 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 and the biconvex lens is larger in magnitude than the radius of curvature of the first surface of the negative lens, and each biconvex lens in the first and third components is symmetrical, characterized in that the second component is made in the form of a plano-convex lens facing the object with a plane, the negative lens of the third component is biconcave, indicator the refraction of the fourth component - a positive meniscus of more than 1.64 and less than 1.9 for the line e, the refractive index of the biconvex lens of the third component is more 1.56 and less than 1.63 for line e and less than the refractive index of the biconvex lens of the first component, in addition, the condition:
0.5f '<d ₄ <f',
where f 'is the focal length of the lens;
d ₄ is the distance between the first and second components. 2. A fast lens according to claim 1, characterized in that the refractive index of the second component is a plano-convex lens of more than 1.5 and less than 1.87 for line e.