Method and apparatus for reducing optical cross talk in a liquid crystal optical switch

DETAILED DESCRIPTION The present invention relates to a method and an apparatus for electrically driving a liquid crystal device operating as a high-speed optical switch in a preferred field sequential color display system.
The liquid crystal device has three electrode structures formed into two cell segments of the type described in the Middleton and Shanks et al.
patents and includes a liquid crystal material captured between a pair of spaced-apart and generally parallel transparent substrates.
One substrate has a pair of contiguous conductive regions that comprise first and second electrode structures, and the other substrate has a single conductive region that comprises a common electrode structure.
The first and common electrode structures define a first cell segment, and the second and common electrode structures define a second cell segment.
The method of the present invention includes the steps of applying an excitation potential difference between the first and common electrode structures of the first cell segment during a first time interval to bias the first cell segment to its "ON" state, and applying an excitation potential difference between the second and common electrode structures of the cell segment during a second time interval to bias the second cell segment to its "ON" state.
To minimize optical cross talk between the first and second cell segments while the second cell segment is biased in its "ON" state during the second time interval, a high impedance condition is introduced between the first and common electrode structures for at least part of the time while the second cell segment is biased in its "ON" state.
The above-described method can be practiced in an analogous manner to minimize the optical cross talk between the first and second cell segments while the first cell segment is biased in its "ON" state.
The apparatus of the present invention is a switching circuit that has a separate output to electrically drive a different one of the cell segments.
The switching circuit is operable to carry out the above-described method steps