Rapid starting, high-speed liquid crystal variable retarder

Claim 1

A rapid starting, high-speed liquid crystal variable optical retarder comprising: a liquid crystal cell which includes liquid crystal material contained between a pair of opposed, spaced-apart optically transparent electrode structures; the liquid crystal material having directors and including a chiral additive to inhibit director relaxation beyond the π radian twist state, each electrode structure having a conductive layer applied thereto and having a conditioned inner surface which has been conditioned so that the directors of the liquid crystal material in contact therewith become substantially uniformly aligned to form tilt bias angles with the conditioned surface, the tilt bias angles of the directors in contact with the conditioned surface of one electrode structure being defined in a rotational sense opposite to the tilt bias angles of the directors in contact with the other conditioned surface of the other electrode structure; and field means for applying an electric field to the cell when the directors are intially relaxed in the (radian twist state to cause a substantial number of the surface noncontacting directors to align in substantially end-to-end relation in a direction normal to the conditioned surfaces to provide substantially reduced optical retardation through the cell of light incident to one of the surfaces of the electrode structures, and for changing the electric field to cause at least some of the surface noncontacting directors within the interior of the cell to recede from the end-to-end alignment to provide in a relatively short time essentially half-wave optical retardation of light incident to one of the surfaces of the electrode structures.