GB1139286A - Exposure control apparatus - Google Patents

Abstract

1,139,286. Photo-electric diaphragm control. EASTMAN KODAK CO. Feb. 9, 1967 [July 28, 1966; Feb.14, 1966], No. 6353/67. Heading G2A. [Also in Division G1] In an exposure control apparatus of the type having an exposure aperture regulator controlled by a photo-electric device, the device controls the energy content of one polarity of a source of current pulses energizing an electro-mechanical transducer to determine the mean regulator position and to provide vibration thereabout. Light incident upon a lens L, Fig. 1, passes through a pair of apertures in a plate A to fall respectively on a photo-sensitive material F and a photo-resistor R4. The latter is connected to shunt a resistor R2 in a multivibrator energizing the coils N1, N2, of a motor controlling the aperture plate A through a linkage B and the plate is driven to a point whereat the amount of light falling on the photoresistor equalizes the pulse currents through the two coils. A number of permanent magnet and electromagnet motor arrangements with coils N1, N2, mounted alternatively on the stator or rotor are described with reference to Figs. 2-4 (not shown). Further arrangements described include a transistor amplifier between the multi-vibrator and coil N1, and single and double stage transistor amplifier between the multi-vibrator and both the coils, and in still further arrangements the direction of current flow through a motor comprising a single coil element is reversed by four switching transistors or by a Schmitt trigger. The circuit may include filters to suppress noise and may be built as an integrated component. Application of the invention to a television camera is also mentioned.