Electro-optical light shutter device

Claim 1

An electro-optical light shutter device comprising a pair of polarizers, a thin plate of solid-solution ceramic material disposed between said polarizers, a pair of electrodes provided on at least one of the surfaces of said thin plate of solid-solution ceramic material so as to produce an electric field in a direction parallel to the plane of said thin plate, said solid-solution ceramic material having a non-ferroelectric phase adjoining to a ferroelectric phase through a morphotropic phase boundary so that application of an electric field to said ceramic material causes forced transition between the non-ferroelectric phase and the ferroelectric phase, and voltage source means for applying a first voltage having a voltage value required for shutter operation in the operating position of the shutter and a second voltage of polarity opposite to that of said first voltage and having an absolute value smaller than that of said first voltage in the non-operating position of the shutter to reduce transmission light intensity of the shutter device to a level less than the zero voltage level to provide a high contrast ratio between the operation position and the non-operating position of the shutter.