DE2360357A1 - Range finder for SLR camera - has inclined transparent plate with reflecting parts for partial images - Google Patents

Abstract

A transparent plate is set at an angle in the viewfinder light path in the SLR camera. Part of the bottom surface and part of the top surface are silvered so that two partial images are obtained. If the incident rays from the two partial images are parallel then the resulting images are overlapped and the camera is in focus. Any slight out of focus condition is magnified by the refraction in the block to produce two images in the viewfinder. The system is simple to operate and the user simply alters the focus and distance controls on the camera to produce coincident images.

Description

Patent attorney DIPL-PHYS. DR, W. LANGHOFF Attorney B. LANGHOFF *

θ MUNICH 81 · WISSMANNSTRASSE 14 · TELEPHONE 932774 · TELEGRAM ADDRESS: LANeHOFFPATENT MUNICH

Munich, December 3, 1973 Our reference: - 62-1335 "

Braun Aktiengesellschaft, Frankfurt / Main, Rüsselsheimerstraße 22

Rangefinder

The invention relates to a range finder for lenses, which when in focus between at least two lens elements have a practically parallel beam path /, in particular varifocal lenses, being in the area of the parallel Beam path at least two mirror elements are arranged, which are at right angles to the optical axis of the lens at a distance from each other and with their mirror surfaces in the .. ■ are essentially parallel to one another and oriented in such a way that the reflected rays are directed into a collecting viewfinder system be, whose insight forms the rangefinder view, wherein the mirror elements are part of an essentially plane-parallel, transparent plate are.

The invention is based on the object of such To develop rangefinder so that it can be produced relatively easily. '

The solution to this problem is to be seen in the fact that both mirror elements as fully reflective surface mirrors the front or the back of the tr anspjär harvest plate are upset. Such a distance measuring element can be relatively easy to manufacture, since both surface mirrors

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can be applied in one uninterrupted operation.

The accuracy of the range finder can be increased by making the surface mirror at an angle form with each other, the optical effect here half the angle between the two middle

Rays of the bundles of rays used by the range finder is equivalent to. It is thereby achieved that the rays leaving the distance measuring element are completely parallel.

The invention is described below with reference to schematic drawings additionally described using an exemplary embodiment.

Figure 1 is an axial section through a zoom lens for a pilm camera with a range finder according to the invention, which also serves as a seeker.

FIG. 2 is a sectional view through a transparent glass plate, on the surfaces of which the mirror elements are upset.

The varifocal lens shown in Figure 1 for a film camera comprises a vario part 2 with a distance setting ring 1 and a basic lens 3 »behind it which in turn is a film stage 4 of the film recording camera.

The varifocal lens shows between the Vario part 2 and the basic lens 3 have a practically parallel beam path. In. this area lies one opposite the optical axis of the lens inclined distance measuring element 6, which consists of an approximately plane-parallel transparent There is glass plate 21 which is cemented into a housing part 22 of the film camera. The front surface of the glass plate 21 has on the surface facing the Vario part 2 in the area of its exposed edge a completely reflective upper

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3 23 & 0357

surface mirror 23, and the back of the glass plate is provided with a surface mirror extending over a larger area 2Ά, which is also completely reflective. The distance measuring element is inclined at an angle of 45 ° to the optical axis, so that the reflected rays run at right angles to the optical axis and reach a viewfinder lens 7 and from there via a deflecting mirror 8 into an erecting lens system 9, through an image mask and through ocular elements 11, through which: the image can be perceived with the eye 12 of a viewer.

The finder lens 7, the erecting lens system 9 and the ocular members 11 form the finder system. However, it can also be any Another lens system can be used as a viewfinder, with which it is possible to look out of the essentially parallel rays, ... which are masked out by the distance measuring element 6 to generate an image that can be observed with the eye. ■ '- ■ "-" ■ ;.

The distance measuring element 6 consists of a transparent glass plate, the front and back of which form an angle with each other which is half the size of the central rays of the bundles of rays 25 and 26, marked with arrows in FIG - "Part 2 and the basic objective 3 a parallel beam path. In this case, a plane-parallel glass plate 21 can be used. In practice, however, the rays between the vario part and the basic objective are not completely parallel, so that it is necessary to design the glass plate 21 in a wedge shape in order to compensate for the deviation from the parallel beam path. The wedge angle of the surfaces of the glass plate 21 bearing the surface mirrors 23 and 2k , however, is at most in the order of magnitude of "angular minutes.

As can be seen from FIG. 2, the light beam becomes broken at the front of the glass plate 21 and reaches up

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at_the-back of the same, is then taken from the surface mirror 24 reflects and leaves the glass plate 21 after a refraction at the front surface as exiting Light beam 25a.

The light beam at a distance from the light beam 25 26 is reflected by the surface mirror 23 applied to the front of the glass plate and forms an exiting light beam 26a, which next to the light beam 25a. runs.

The rear surface mirror 2k can also be made smaller than is shown in FIG. 2, since only the surface of the rear side hit by the light beam 25 has to be mirrored.

The two light beams 25 and 26 are assumed to be of equal size in FIG. However, they can also be different be measured.

Furthermore, those surface areas of the glass plate 21, which are not penetrated or hit by the light beams 25 and 26, with an anti-reflective coating or a be provided with absorbent covering.

As long as the incident light beams 25 and 26 run parallel to one another, the exiting light beams are also 25a and 26a in parallel. Any inaccurate distance setting of the lens, however, leads to the fact that the light beams incident at different points on the glass plate 21 25 and 26 are no longer parallel to one another, so that the emerging light beams 25a and 26a are not either run more parallel to each other. This leads to a double image or a 'blurred' image in the viewfinder system.

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Claims (2)

P ate η ta η s ρ r ü c h e Rangefinder for lenses j when focusing between at least two. lens members · one practical have parallel beam paths, in particular varifocal lenses, wherein at least two mirror elements are arranged in the area of the parallel beam path, which are at right angles to the optical axis of the lens have a distance from each other and which are oriented with their mirror surfaces substantially parallel to each other and so that the reflected rays are directed into a collecting viewfinder system, whose view the rangefinder forms, the mirror elements being part of "an essentially plane-parallel, transparent plate are, according to patent Mr. (Patent application P 22 54 446.3), thereby geke η η ζ eich η et > that both mirror elements are applied as fully reflective surface mirrors (23, 24) on the front and the back of the transparent plate (21). 2. Distance meter according to claim 1γ da d u r c h g e k e n.n ζ e i η et that the surface mirror (23, 24) form an angle with each other 'from the optical Effect is half the angle between the two middle ones Rays of the rays used by the range finder ■ bundle corresponds to ... '' 509823/05 51 Blank page