JPS6015246B2 - telephoto lens for photography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a telephoto lens, and more particularly to a photographic telephoto lens in which focusing is performed by moving a part of the lens in the rear lens group, which is arranged apart from the front lens group along the optical axis. .

Telephoto lenses used as interchangeable lenses for single-lens reflex cameras have traditionally been focused by extending the entire lens, but
As a result, a technique has been established for performing focusing with a telephoto lens without degrading image quality by only moving a portion of the lens, and various modifications and improvements have been proposed since then.

This new focusing method is effective when the focal point is long or when the lens is bright.In the case of a fast follow-up type photographic lens, as the front element becomes larger, a large amount of force is required to drive the focusing. Changes in the balance when the lens system was drawn out made it difficult to operate.

The purpose of the present invention is to make a telephoto lens with a large opening, which performs focusing by moving some lenses in the rear lens group,
In particular, the objective is to obtain good image quality in all aspects of chromatic aberration, spherical aberration, coma aberration, astigmatism, and distortion. In the lens of the present invention, the front lens group consists of three single lenses, positive, negative, and positive in order from the object side, and the rear lens group consists of a negative niscus lens with a concave surface facing the image side, and a positive and negative lens. It consists of a bonded negative lens, and focusing is performed by moving the bonded negative lens in the direction of the optical axis. year,
The numerical specifications described below are given.

The cross-sectional shape of the lens is as depicted in FIG. 1, and various aberrations at infinity are shown in FIG.

r is the Shinnes radius of curvature, d is the distance between lens surfaces, the refractive index for the n'-d line, and is the Abbe number, then the focal length f = 1
00, Fno=1:5.0 angle of view 2=3. ㅅface number
r d n re1
64.618 2.236 1.497 81
．． 62 -30.938 2.3413 -
27.163 0.835 1.6134 43.
84 143.973 0.2715
38.504 1.632 1.54771 62.
96 -134.854 35.7937
5.808 0.642 1.58913 61.1
8 5.439 2.8519 23
．． 806 0.514 1.7552 27.51
0 51.239 0.385 1.713
53.911 14.023As can be seen from the aberration curves in FIG. 2, various aberrations are well corrected.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a lens showing an example. Figure 2 is an aberration diagram. In the figure, r is the sinus surface, d is the sinus thickness or air spacing, M is the meridional occlusion line, and S is the sagittal occlusion line. Figure 1 Figure 2

Claims (1)

[Claims] 1. Consists of 6 elements in 5 groups, including a front lens group with positive refractive power consisting of three positive, negative, and positive single lenses in order from the object side, a negative meniscus lens, and a positive and negative lens. a rear lens group consisting of a bonded negative lens and spaced axially from a front lens group;
In a telephoto lens in which focusing is performed by moving a bonded negative lens, the focal length is normalized to f = 100, r is the radius of curvature, d is the distance between lens surfaces, n is the refractive index of the d-line,
When ν is Atsube number, surface number r d n ν 1 64.618 2.236 1.497 81.6
2 -30.938 2.3413 -27.163
0.835 1.6134 43.84 143.97
3 0,2715 38.504 1.632 1.5
4771 62.96 -134.854 35.79
37 5.808 0.642 1.58913 61
．． 18 5.439 2.8519 23.806 0
．． 514 1.7552 27.510 51.239
0.385 1.7713 53.911 14.0
A photographic telephoto lens that almost satisfies 23 specifications.