RU2592746C1 - High-aperture lens - Google Patents

Abstract

FIELD: photography.

SUBSTANCE: lens consists of two components separated by aperture diaphragm. First component consists of single plane-convex lens, which convex surface faces object plane, single positive meniscus, which convex surface faces object plane, and negative meniscus, which convex surface faces object plane. Second component consists of negative meniscus, which concave surface faces object plane and glued from negative and positive menisci; positive meniscus, which concave surface faces object plane; plane-convex lens, which convex surface faces image plane and plane-convex lens, which convex surface faces object plane.

EFFECT: technical result is increase of rear section for use of lens with reflex cameras of APS-C (25 5/10×18 6/10 mm) form, high resolution of lens, while maintaining focal distance, angular field and aperture ratio of 1:1 2/10 while maintaining high image quality and improved manufacture ability.

1 cl, 5 dwg, 2 tbl

Description

The invention relates to optical instrumentation and can be used as a photographic and filming lens.

Known fast lens, which is described in the patent for utility model RU 109575, IPC G02B 9/00, publ. 10/20/2012. In a fast lens containing two components separated by an aperture diaphragm, the first I of which contains three menisci, convex to the space of the object, of which the first and second menisci with positive optical forces, the third meniscus with negative optical power φ _{I, 3} , the second component II, consisting of the first glued meniscus with optical power φ _{II, 1} , facing concavity to the space of the object, consisting of a biconcave lens with optical power φ _{II, 1,1} , and a biconvex lens with optical power φ _{I I, 1,2} , the second positive meniscus with optical power φ _{II, 2} and the third lens with optical power φ _{II, 3} , the first glued meniscus of the second component II with optical power φ _{II, 1} , facing concavities to the space of the object, is made positive, the second positive meniscus with optical power φ _{II, 2 is} convex to the object space, and the third lens with optical power φ _{II, 3 is} made in the form of a negative meniscus convex to the space of the object.

However, this lens has insufficient aperture and a small angular field.

The closest analogue is a fast lens, described in the patent for invention RU 2431165, IPC G02B 9/62, publ. 10/10/2011. The lens contains two components separated by an aperture diaphragm. The first component contains three meniscuses that are convex to the space of the object: a positive meniscus, a glued meniscus containing positive and negative menisci, and a negative meniscus with optical power φ _I glued from biconvex with optical power φ _{I, 1} and biconcave with optical power φ _{I , 2} lenses. The second component consists of a negative meniscus glued from a biconcave and biconvex lens, turned concavity to the space of the object, a biconvex lens and a positive meniscus, convex to the space of the object. The negative meniscus of the first component and the positive meniscus with the optical power φ _{n of the} second component are made in the form of single lenses.

However, the lens with a focal length of 50 mm and a relative aperture of 1: 1.2 has an insufficiently large rear segment of 33.32 mm.

The task of the invention is the creation of a fast lens with enhanced optical and technological characteristics and a rear segment of at least 39 mm.

The technical result is an increase in the rear segment for using the lens with APS-C format SLR cameras (25.5 × 18.6 mm), an increase in the resolution of the lens, while maintaining the focal length, angular field and relative aperture of 1: 1.2.

To solve this problem, a fast lens is proposed, consisting of two components separated by an aperture diaphragm, the first component is made of three lenses, the first of which is a single positive lens, convex to the space of objects, the second is the positive meniscus, convex to the space of objects, and the third lens along the rays is the negative meniscus, convex to the space of objects, the second component is presented in the form of a glued negative meniscus, facing the vogue a flat surface to the plane of objects, consisting of a negative and a positive lens, a positive lens and the last lens along the rays, represented by a positive lens, convex to the plane of objects, in contrast to the first lens, the first lens is a convex-flat lens and all lenses of the first component single, and in the second component in the first meniscus, the negative and positive lenses are made in the form of menisci, the second lens along the rays is represented by the meniscus, facing concavity to DMetI after the second lens along the ray added planoconvex lens facing the convex surface to the image plane, and the last lens in the course of rays in the lens convex-flat.

In FIG. 1 presents an optical diagram of the proposed aperture lens. In FIG. 2 shows a graph of the modulation transfer function as a function of the image field with a relative aperture of 1: 1.2. In FIG. Figure 3 shows a graph of the modulation transfer function versus the image field with a relative aperture of 1: 2.8. In FIG. 4 is a graph of the modulation transfer function versus spatial frequency with a relative aperture of 1: 1.2. In FIG. 5 is a graph of the modulation transfer function versus spatial frequency with a relative aperture of 1: 2.8.

A fast lens (Fig. 1) consists of two components separated by an aperture diaphragm. The first component I consists of a single plano-convex lens 1 facing a convex surface to the plane of objects, a single positive meniscus 2 facing a convex surface to the plane of the object, and a negative meniscus 3 facing a convex surface to the plane of the object. The second component II consists of a negative glued meniscus facing a concave surface to the plane of objects, consisting of a negative meniscus 4 and a positive meniscus 5; a positive meniscus 6 facing a concave surface to the plane of objects; a plano-convex lens 7 facing a convex surface to the image plane, and a plano-convex lens 8 facing a convex surface to a plane of objects.

The lens works as follows: the light flux from an object located at infinity falls into the lens, where it passes through lenses 1, 2, 3, 4, 5, 6, 7, and 8 and forms an image of the object in the plane of the best setting.

In accordance with the proposed solution, an aperture lens with a focal length f` = 50 mm, a relative aperture of 1: 1.2 and a linear image field of 25.5 × 18.6 mm was calculated. The calculation results are represented by graphs in FIG. 2, 3, 4, 5.

The spectral characteristics are presented in table 1.

The design parameters of the proposed lens are shown in table 2.

Characteristics of the calculated fast lens:

Focal length 51.478 mm Aperture D / F: 1: 1.2 Entrance pupil diameter 41.05 mm Entrance pupil position 57.23 mm Exit pupil diameter 144.9 mm Exit pupil position - 181.73 mm System length 119.577 mm

The negative spherical aberration of the first component I is compensated by the positive spherical aberration of the second component II. The coma of the first and second components are correlated. The positive astigmatism of the first component I is offset by the negative astigmatism of the second component II. The distortion of the first component I, positive in magnitude, is minimized by the negative distortion of the second component II. Chromatic aberrations of position and magnification are correlated independently in the first I and second components.

The image contrast to y` = 10 mm at a frequency of 30 l / mm with a relative aperture of 1: 1.2> 38%, while the prototype ≈33%. The rear segment is S` = 39.777, and the light diameter of the last lens does not exceed 36.1 mm, which allows you to mount the lens on SLR cameras, including Nikon F mount.

Thus, the proposed fast lens allowed maintaining the linear field to improve image quality and increase the rear segment, improve manufacturability, increase resolution, which allows it to be used together with APS-C format SLR cameras (25.5 × 18.6 mm or less)

Claims (1)

A fast lens consisting of two components separated by an aperture diaphragm, the first component is made of three lenses, the first of which is a single positive lens, convex to the space of objects, the second is the positive meniscus, convex to the space of objects, and the third lens along the rays - a negative meniscus convex to the space of objects, and the second component is represented as a glued negative meniscus facing a concave surface to the plane of objects consisting of a negative and a positive lens, a positive lens and the last along the rays of the lens, represented by a positive lens, convex to the plane of objects, characterized in that in the first component the first lens is a convex-flat lens and all the lenses of the first component are single, and in the second the component in the first meniscus, the negative and positive lenses are made in the form of menisci, the second lens along the rays is represented by the meniscus facing concavity to the plane of objects, after the second lens along the rays to avlena plano-convex lens facing the convex surface to the image plane, and the last lens in the course of rays in the lens convex-flat.

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