GB1580830A

GB1580830A - Viewfinder and exposure factor indicator for phtographic cameras

Info

Publication number: GB1580830A
Application number: GB2226877A
Authority: GB
Original assignee: Pentacon Dresden VEB
Current assignee: Pentacon GmbH Foto und Feinwerktechnik
Priority date: 1976-05-31
Filing date: 1977-05-26
Publication date: 1980-12-03
Also published as: DE2720400A1; DD126394B1; DD126394A1; DE7714405U1

Description

(54) VIEWFINDER AND EXPOSURE FACTOR INDICATOR FOR PHOTOGRAPHIC CAMERAS (71) We, VEB PENTACON DRES DEN, Kamera-und Kinowerke, a corporation organised under the laws of the German Demo critic Republic, of 76 Sohandauer Strasse, Dresden, German Democratic Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method iby which it is to be performed, to be particularly described in and by the following statement:- This invention relates to an indicator device in the vievrfinder system of photographic cameras with indicator panel illuminated by a luminous element.

For the indication of exposure factors in photographic cameras it is known to view microqincandescent lamps, luminous diodes and other micro-luminous elements through the viewfinder eyepiece directly as indicators.

In order to illuminate a symbol indicator with microzluminous elements, for example in the case of microXinlcandescent lamps, the lamp globe lis matted or ground; it is also known to arrange a diffuser plate between a lamp and a symbol indicator. With these measures the symbol indicator is illuminated irregularly and with loss of light.

The object o the invention consists in unifirmly illuminating symbol indicators with a luminous element in the viewfinder system of photographic cameras, and conducting images at maximum brightness to the viewing eye.

According to the invention we provide a viewfinder and exposure factor indicator system comprising a roof prism, an eyepiece and an indicator system including an indicator panel having exposure factor markings, at least one luminous element which illuminates the indicator panel via an optical system, the indication system including a reflecting surface before or after the panel and being arranged to transmit light to the roof prism so as to produce an image of the exposure factor markings and an image of the luminous element in the exit pupil of the viewfinder.

The invention is illustrated and explalined by reference to examples of embodiments shown in the accompanying drawings in which: FIGURE 1 shows a viewfinder system with symbol reflected in from beneath, seen from the eyepiece side, FIGURE 2 shows a variant with reflection on the side face of a pentahedral roof prism, FIGURE 3a shows an arrangement with reflection on the irnage-eirecting surface of a pentahedral roof prism, and FIGURE 3b shows the lateral elevation of FIGURE 3a.

In Figure 1 there is represented the viewfinder system with the arrangement according to the invention, seen from the eyepiece side.

A pentahedml ,roof prism 2 with field lens 3 lying therebeneath is arranged in known manner behind the eyepiece 1. Within the space between field lens 3 and pentahedral roof prism 2 there is provided an indicator system, consisting of luminous element (plreferably a micro-incandescent lamp) 4, subsequently placed image reproduction system 5 with deflector surface 6 and indicator panel 7 showing exposure factors such as time, aperture values and distance.

Figure 2 represents a variant of Figure 1 in which rhe pentahedral roof prism 2 possesses a bevelled-off side face adjacent which the indicator system is arranged.

Figure 3 shows another variant of the arrangement and formation of the indicator system. Here the indicator system is arranged opposite to the eyepiece 1, before the imageerecting surface of a pentahedral roof prism 2, and consists of a luminous element 4, a lens 5 serving as an image reproduction system, an indicator panel 7 and an optical component 8 varying the path length, with the deflector surfaces 9 and 10 (see Figures 3a and 3b). The optical component 8 which varies the path length is necessary whenever the indicator panel 7 to be .reflected in is situated far inside or outside the focal length of the eyepiece 1. In these cases it is necessary, w.ith the aid of an optical component with additional refractive power, to reproduce the indicator panel 7 in a plane which can be seen sharply simultaneously with the viewfinder image plane by the observer through the viewfinder eyepiece.

Due to the arrangement of the lens 5, in combination with the path-varying optical component 8 and/or the eyepiece 1, the illuminating surface of the luminous element 4 is reproduced in the exit pupil of the viewfinder system and thus in the pupil of the eye of the observer.

The indicator panel 7 is arranged in the vicinity of the lens 5. Thus the possibility is gained of arranging the indicator panel 7 in the plane of sharpness of the viewfinder eyepiece 1 in larger dimensions than is the case with direct viewing of the effective surface of the luminous element 4.

Furthermore due to the reproduction of the effective surface of the luminous element 4 in the exit pupil of rhe viewfinder system a uniform illumination of the indicator panel is achieved with optimum brightness. One or more luminous elements and thus indicator systems may be arranged for the indication of exposure. The indicator panel may carry any desired exposure factor symbols, such as arrows, triangles, etc. Moreover it is also wi.thin the scope of the invention to arrange numenical indications in the indicator panel.

WHAT WE CLArM rs:- 1, A camera viewfinder and exposure factor indicator system comprising a roof prism, an eyepiece and an indicator system including an indicator panel having exposure factor markings, at least one luminuous element which illuminates the indicator panel via an optical system, the indication system including a reflecting surface before or after the panel and being arranged to transmit light to the roof prism so as to produce an image of the exposure factor markings and an image of the luminous element in the exit pupil of the viewfinder.

2. A viewfinder and indicator system as claimed in claim 1, in which the roof prism is formed with a bevelled off side face wherein said reproduction system is disposed against said bevelled-off side face.

3. A viewfinder and indicator system as claimed in claim 1, wherein said reproduction system has said reflecting surface incorporated therein.

4. A viewfinder indicator system as claimed in claim 3, wherein the image reproduction system is positioned adjacent a surface of the roof prism which surface is on the opposite side of the roof prism to the eyepiece, said reflecting surface being incorporated in an optical component disposed between said panel and said prism surface.

5. A viewfinder and indicator system substantially as described with reference to any of the examples shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

plane which can be seen sharply simultaneously with the viewfinder image plane by the observer through the viewfinder eyepiece.

Due to the arrangement of the lens 5, in combination with the path-varying optical component 8 and/or the eyepiece 1, the illuminating surface of the luminous element 4 is reproduced in the exit pupil of the viewfinder system and thus in the pupil of the eye of the observer.

The indicator panel 7 is arranged in the vicinity of the lens 5. Thus the possibility is gained of arranging the indicator panel 7 in the plane of sharpness of the viewfinder eyepiece 1 in larger dimensions than is the case with direct viewing of the effective surface of the luminous element 4.

Furthermore due to the reproduction of the effective surface of the luminous element 4 in the exit pupil of rhe viewfinder system a uniform illumination of the indicator panel is achieved with optimum brightness. One or more luminous elements and thus indicator systems may be arranged for the indication of exposure. The indicator panel may carry any desired exposure factor symbols, such as arrows, triangles, etc. Moreover it is also wi.thin the scope of the invention to arrange numenical indications in the indicator panel.

WHAT WE CLArM rs:- 1, A camera viewfinder and exposure factor indicator system comprising a roof prism, an eyepiece and an indicator system including an indicator panel having exposure factor markings, at least one luminuous element which illuminates the indicator panel via an optical system, the indication system including a reflecting surface before or after the panel and being arranged to transmit light to the roof prism so as to produce an image of the exposure factor markings and an image of the luminous element in the exit pupil of the viewfinder.
2. A viewfinder and indicator system as claimed in claim 1, in which the roof prism is formed with a bevelled off side face wherein said reproduction system is disposed against said bevelled-off side face.
3. A viewfinder and indicator system as claimed in claim 1, wherein said reproduction system has said reflecting surface incorporated therein.
4. A viewfinder indicator system as claimed in claim 3, wherein the image reproduction system is positioned adjacent a surface of the roof prism which surface is on the opposite side of the roof prism to the eyepiece, said reflecting surface being incorporated in an optical component disposed between said panel and said prism surface.
5. A viewfinder and indicator system substantially as described with reference to any of the examples shown in the accompanying drawings.