DE2246966C3 - Four-part telephoto lens - Google Patents

Description

table Surface curvature vertex refractive breaking

che radius distances index number

No.

r dn, v,

1 +0.25755 0.0448 1.64304 59.85

2 +1.04505 0.0008

3 +0.23167 0.0411 1.64304 59.85

4 +0.52272 0.0207

5 -t-1.02055 0.0165 1.75458 34.72

6 +0.15835 0.2543

7 +0.65891 0.0328 1.79180 25.87

8 +1.25205

2. Four-section telephoto lens with two sections with positive refractive power in front of the diaphragm Element of negative refractive power follows and at a considerable distance from it behind the diaphragm as a member of positive refractive power formed against the image plane of a hollow meniscus is arranged, characterized in that the following .Konstruktionsdaten in the context of minor changes of the correction status are maintained:

Focal length. 1.00

Focal ratio 1: 4

Angle of view 27 °

Back focal length 0.4238 /

table Surface curvature vertex refractive breaking

che radius distances index number

No.

r rf η, ν,

1 +0.37841 0.03333 1.69660 53.05

2 +2.26722 0.00022

3 +0.28981 0.09488 1.64129 55.15

4 +0.45103 0.02389

5 +1.02474 0.01967 1.76167 27.37

6 +0.20093 0.32910

7 +0.63116 0.02778 1.66499 32.69

8 +2.59609

The invention relates to a four-part telephoto lens, in which, in front of the diaphragm, two members of positive refractive power are followed by one member of negative refractive power and at a clear distance therefrom behind the diaphragm a meniscus which is hollow towards the image plane Member of positive refractive power is arranged.

Lenses of this type are often designed for medium focal lengths and light intensities and are used as interchangeable lenses both as portrait and as long-range lenses with an angle of view approximately half that of normal optics on small-format cameras of the format 24 36 mm ^2. When developing such lenses, the aim is to reduce the external dimensions, such as overall length and lens diameter, without, however, reducing the

ίο to worsen image error correction once achieved. Lenses that have become known so far come as desired and within the scope of the described Structure close to possible properties, whereby the required image quality is only maintained in this way.

can be obtained that at least one of the

Lens members is designed as a cement member. Through this

but the manufacturing costs for the lens are increased in any case.

The invention was therefore based on the object

to further simplify the known structure of a telephoto lens and with the lowest possible external dimensions to improve the error correction, especially the chromatic and the sagittal residual error both for the infinitely distant

as well as for the object in the vicinity to a minimum.

In the case of telephoto lenses with the structure described at the outset, this object is achieved by designing them with the design data in accordance with one of the data tables listed in the features of claims 1 and 2.
The drawing sheets show in the
F 1 g. 1 and 2 a lens section and the correction curves for the spherical aberration, the astigmatism and the distortion ces objective according to claim 1 and in the

F i g. 3 and 4 a lens section and the Korrektionskunen for the objective according to claim 2.
In FIGS. 1 and 3, the radii of curvature of the lens surfaces are denoted by T ₁ to r ₈ , the distances between the lens vertices are denoted by d _x to d ₇ , the distance between the last lens surfaces up to the image plane is denoted by s' (rear focal length) and the diaphragm is denoted by B1 . From the data it can be seen that the overall length of the lenses from the first vertex to the film plane can be kept smaller than the focal length.

The F i g. 2 and 4 show the excellent state of correction of the specified objectives a relative aperture of 1: 4 and an image angle of ± 13.5 °. It is noteworthy that all lens elements are designed as individual lenses, all surfaces of these lenses being hollow towards the image plane.

The excellent state of correction was achieved, among other things, by the fact that the refractive indices of the Glasses greater than 1.64 used in the positive lenses and those used in the negative lens Glass are greater than 1.75 and the Abbe number of the positive lens behind the diaphragm is less than 33 is. This also makes it possible to increase the size of the diaphragm space between 0.25 · / and 0.37 · / choose what has a direct effect on the shortening of the overall length.

The further improvement of the correction of the invention Objective according to claim 2 was achieved in that the center thickness of the second Positive lens larger than 0.085 · / was chosen.

For this purpose 2 sheets of drawings

Claims (1)

Patent claims: 1. Four-section telephoto lens with two sections with positive refractive power in front of the diaphragm Element of negative refractive power follows and at a considerable distance from it behind the diaphragm as member of positive refractive power formed against the image plane of hollow meniscus is arranged, thereby characterized in that the following design data are within minor Changes to the correction status are complied with: Focal length 1.0 Focal ratio 1: 4 Angle of view ± 13.5 * Back focal length 0.5102 /