Electrooptic diaphragm and circuit operative for causing the diaphragm

Abstract

Radially successive annular electrodes disposed in a general plane define between themselves intermediate annular zones in which is confined electrooptic material. Selected annular zones are rendered transparent by applying to pairs of selected annular electrodes potential differences which extend through the electrooptic material in the direction in which the general plane extends, not perpendicular to the general plane. The annular zones are rendered transparent in cumulative succession proceeding radially outwards, and have surface areas such that, as each next annular zone becomes transparent too, the transparent area of the arrangement doubles each time. A control circuit includes a counter whose outputs are connected to the inputs of a gating network, the latter having outputs connected to various ones of the annular electrodes, establishing the rate at which the cumulatively successive changes of state of radially outwardly successive annular zones proceeds. After all zones have been rendered transparent, they all are rendered non-transparent simultaneously to terminate an exposure, if this has not already been done by a light-totalizing circuit. The light-totalizing circuit includes a counter which counts a pluse train and reaches a predetermined count after a time interval which depends on scene light, the reaching of the predetermined count causing all annular zones thus far rendered transparent to go non-transparent.