GB854608A - Photographic camera with automatic exposure setting - Google Patents

Abstract

854,608. Photo-electric control devices. GAUTHIER G.m.b.H., A. Dec. 1, 1958 [Jan. 25, 1958], No. 38593/58. Class 40(3). In the automatic exposure setting device of a photographic camera, an exposure setting member is adjusted by a D.C. motor, the direction of rotation of which is determined by the alternative operation of two electronic amplifiers, preferably transistors, in dependence on the position of the displaceable contact of a moving coil relay responsive to the output of a photoelectric element exposed to ambient light. In Fig. 3, the output of a photo-cell 9, which may be amplified at 19, determines the state of a moving coil relay 8 whose displaceable contact 7 may be, as shown, in a central open position, or may contact one of two fixed contacts 10, 11, to earth the base of one of two transistors 12, 13, thus initiating a collector current in the transistor. A low-power, high speed, D.C. motor- 6 is driven in a direction dependent on which transistor is conducting, and operates through reduction gearing 23 and a friction clutch 32, to adjust a diaphragm setting ring 5 and also to move the wiper 15 of a logarithmically stepped resistor 14 which shunts the relay 8; alternatively, this resistor may be in series with the relay. The motor runs until the relay current is such that contact 7 moves to the open position; if the diaphragm setting ring 5 is driven against one of its stops, warning and locking signals are given, and a cut-out switch in each transistor circuit may operate. The resistor 14 is connected to an exposure time setting ring 4 so that account may be taken of the time setting; this connection may be by means of a detachable coupling such that relative adjustment may be made between resistor and time setting ring to allow for other exposure factors, e.g. filters, film sensitivity. Alternatively, the ring 5 and the wiper 15 may be made relatively adjustable. In addition, the fixed contacts 10, 11 of the relay 8 are mounted on an adjustable carrier 18 to provide for further adjustment. Temperature compensation is provided by a temperature-sensitive resistor 20 and a variable resistor 41 in the relay circuit. The motor and gearing are accommodated in the inner space of the lens shutter. The photo-cell and relay are located in the upper part of the camera, the carrier 18 being adjustable by an external knob; and the amplifier components are housed, separately or in combination, in free spaces in the cover hood. The adjustable exposure setting member may vary exposure time or exposure value instead of the diaphragm setting.