RU2431165C1 - Large-aperture lens - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: lens has two components separated by an aperture diaphragm. The first component contains three menisci whose convex sides face the object space: a positive meniscus, a glued meniscus consisting of a positive and a negative meniscus, and a negative meniscus with optical power φ_I, glued from a biconvex lens with optical power φ_I,1 and a biconcave lens with optical power φ_I,2. The second component consists of a negative meniscus consisting of a biconvex and a biconcave lens glued to each other, the concave side of said negative meniscus facing the object space, a biconvex lens and a positive meniscus whose convex side faces the object space. The negative meniscus of the first component and the positive meniscus with optical power φ_p of the second component are in form of a single lens. Relative optical power of the single and glued lenses assumes the following values:

where φ_eq is the equivalent optical power of the lens as a whole.

EFFECT: increasing the linear image field to a S35 film format (25,5 × 18,6 mm) while simultaneously increasing the rear section and maintaining quality of the image.

1 dwg, 1 app

Description

The invention relates to film technology, namely to film-making and photo equipment.

Known fast wide-angle lens [1], consisting of two components separated by an aperture diaphragm. The first component includes those installed in series: a negative meniscus, a biconvex lens, a negative meniscus, a biconvex lens, a positive meniscus, two negative meniscus and a biconvex lens, and the second component includes a biconvex lens, a biconcave lens, a positive biconvex meniscus and two biconvex meniscus.

The lens has the following characteristics: relative aperture 1: 1.2, field of view 84 °. But this lens can be used to shoot movies in the S16 format (12.3 × 7.5 mm).

The closest technical solution to the proposed invention is a fast aperture lens with a large relative aperture [2].

The lens consists of two components sequentially located along the optical axis, separated by an aperture diaphragm. The first component includes a meniscus-shaped positive lens convex to the space of the object, a double-glued positive lens consisting of positive and negative menisci, a negative meniscus facing the convex side into the space of the object.

The second component consists of a negative meniscus facing concavity to the space of the object glued from a biconcave lens and a positive biconvex lens, a positive biconvex lens and a positive meniscus convex to the space of an object glued from a negative and positive meniscus.

The lens has a high relative aperture of 1: 0.95, satisfactory image quality, but its linear field of view is 12.3 × 7.5 mm (film format S16), the rear segment from the last surface of the lens to the plane of the film is too small, which does not allow use it when shooting professional filming equipment containing a mirror shutter, with which the operator has the opportunity to simultaneously monitor the composition of the frame and the sharpness of the subject.

The main task to which the invention is directed is to increase the linear image field to the S35 film format (25.5 × 18.6 mm) while increasing the back section and maintaining image quality.

To solve this problem, a fast lens was proposed, which, like the prototype, contains two components separated by an aperture diaphragm, the first of which contains three menisci, convex to the space of the object, a positive meniscus, a negative glued meniscus containing positive and negative menisci, convex to the space of the object, and the negative meniscus, and the second consists of a glued negative meniscus facing concavity to the space of the object, consisting of the negative a solid biconcave and positive biconvex lenses, a positive biconvex lens and a positive meniscus convex to the space of the object.

In contrast to the prototype, the negative meniscus of the first component with optical power φ _I is glued, consisting of a biconvex positive with optical power φ _{I, 1} and biconcave negative with optical power φ _{I, 2} lenses, and the positive meniscus with optical power φ _{i of the} second component is made in the form of a single lens, while the relative optical powers of single and bonded lenses are:

where φ _eq is the equivalent optical power of the lens as a whole.

The essence of the invention lies in the fact that this embodiment of the proposed fast lens allowed to increase the linear field of view to the film format S35 (25.5 × 18.6 mm), i.e. approximately twice, while maintaining a relative aperture of 1: 1.2 and ensuring high image quality: visual resolution over the entire field reaches 100 l / mm. In addition, the lens provides a large rear segment in excess of 32 mm.

This allows you to use the lens in film cameras - digital and film. In the latter, a shutter is used, requiring a large rear segment.

Thus, a technical result is achieved, consisting in increasing the linear field of view, the posterior segment and high resolution throughout the field.

The present invention is illustrated in the drawing, which shows the optical scheme of the fast lens, as well as the Appendix, which gives the design parameters and graphs of the frequency-contrast characteristics.

The fast lens contains two components separated by an aperture diaphragm AD.

The first component I contains a positive meniscus 1, convex to the space of the object, a negative glued meniscus, convex to the space of the object, containing positive 2 and negative 3 menisci, convex to the space of the object, and a negative meniscus, convex to the space of the object, made glued, consisting of a biconvex positive lens 4 and a biconcave negative lens 5.

The second component II contains a negative glued meniscus facing concavity to the space of the object, consisting of a negative biconcave lens 6 and a positive biconvex lens 7, a positive biconvex lens 8 and a positive meniscus 9, convex to the space of the object and made in the form of a single lens.

In addition, the negative meniscus of the first component with optical power φ _I , containing a biconvex positive lens 4 with optical power φ _{I, 1} and a biconcave lens 5 with optical power φ _{I, 2} , and a single positive lens 9 of the second component with optical power φ _p have values:

where φ _I is the optical power of the first component;

φ _{I, 1} - optical power of a positive biconvex lens of a negative glued meniscus;

φ _{I, 2} - optical power of a negative biconcave lens of a negative glued meniscus;

φ _p - the optical power of the positive meniscus;

φ _eq is the equivalent optical power of the lens as a whole.

The proposed fast lens works as follows.

The rays from the subject pass through the first component I, limited to the aperture diaphragm AD, and the second component II of the lens in a plane aligned with the receiver.

The introduction of single and bonded lenses, the choice of their configuration, their optical powers, made it possible to correct the lens aberrations.

A positive meniscus 1 reduces the angle of the main beam and introduces significant positive spherical aberration, coma, astigmatism, distortion and negative position chromatism.

A negative glued meniscus convex to the object space containing positive 2 and negative 3 menisci convex to the object space introduces negative spherical aberration, to whom the astigmatism, distortion and chromaticity of the position are smaller in absolute value of the aberration of the positive meniscus 1.

A glued negative meniscus, consisting of a biconvex positive lens 4 and a biconcave negative lens 5, introduces negative values of spherical aberration, coma, astigmatism, positive distortion and increase chromatism, and thereby minimizes the aberration of the first component as a whole.

A negative bonded meniscus consisting of a negative biconcave lens 6 and a positive biconvex lens 7, the second component introduces negative spherical aberration, coma, astigmatism, distortion and positive chromatic aberration, which mainly minimize the aberrations of the positive biconvex lens 8 and positive meniscus 9, the space of the object and made in the form of a single lens.

The finally 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 II components.

The choice of the optical forces of the negative meniscus of the first component - φ _I and the biconvex positive lens 4 containing it with the optical power φ _{I, 1} and the biconcave negative lens 5 with the optical power φ _{I, 2} satisfies the condition:

and positive lens 9 of the second component

and allowed to correct image curvature and chromatic aberration of position and magnification.

The execution of the negative meniscus of the first component glued from a biconvex positive lens 4 and a biconcave negative lens 5, and the positive meniscus 9 of the second component in the form of a single lens, made it possible to minimize higher-order aberrations.

Thanks to the use of the proposed technical solution, a fast 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 given in the Appendix.

The optical materials of the lenses and their optical powers are shown in the table.

Key Image Quality Features

Television distortion ρµ image field coordinates

y '= 12.25 mm

- the contrast of the image at a frequency of 30 l / mm with a relative aperture of 1: 1.2> 30% over the entire field of the image, while the prototype has 20%, with a relative aperture of 1: 2.8 - more than 30%, with the prototype ≈ 20%, with a relative aperture of 1:11 - more than 40%, the prototype ≈ 20%.

The rear segment is S '= 33.32 mm, with the light diameter of the last lens D = 34.2 mm. This allows the lens to be used both in digital film cameras and in cameras operating on a film, in which a shutter is installed between the lens and the film at an angle of 45 ° to the optical axis, requiring a large rear segment S '.

Thus, the proposed fast lens allowed to increase the linear field of the image to the film format S35 (25.5 × 18.6 mm) while increasing the rear segment and improve image quality.

Information sources

1. Patent RU No. 2123713, IPC G02B 9/62, G02B 11/34, publ. 12/20/1998

2. DE patent No. 269693, IPC G02B 9/62, G02B 11/34, publ. 07/05/1989 - a prototype.

Claims (1)

A fast lens containing two components separated by an aperture diaphragm, the first of which contains three menisci, convex to the space of the object, a positive meniscus, a glued meniscus containing positive and negative menisci, convex to the space of the object, and a negative meniscus, and the second component, consisting of a glued negative meniscus facing concavity to the space of the object, consisting of a negative biconcave and positive biconvex lenses, polo itelnoy biconvex lens and a positive meniscus facing convex toward the object space, characterized in that the negative meniscus first component having an optical power φ _I, configured glued consisting of a biconvex positive optical power φ _{I, 1} and a biconcave negative optical power φ _{I, 2} lenses, a positive meniscus with an optical power φ _{p of the} second component is made in the form of a single lens, while the relative optical powers of single and bonded lenses are:

,

,

,
where φ _eq is the equivalent optical power of the lens as a whole.

Images