Electronic Control Method for Optical Ferroelectric Shutter at Unequal Duration of its Open and Closed States

Abstract
Optical shutters based on ferroelectric liquid crystal (FLC) possess small transition times and provide accurate selection of pulsed light fluxes of millisecond duration. However, when an optical FLC-shutter must work with unequal duration of the open and closed optical states, the use of the traditional method of electronic control causes dysfunction. In this case, an average (during the control period) direct current begins to flow through the FLC shutter creating a residual volumetric ion charge in the FLC layer. The electric field of this charge distorts the action of the control electric field on the FLC molecules.
The article describes the proposed method of solving the indicated problem. The essence of the method: the control electrical signal corresponding to the longer optical state of the FLC shutter is composed of a sequence of short pulses. This provides mutual equalization of the average energy of positive and negative control signals and, as a consequence - minimizing (zeroing) the direct current. The relations between the time parameters of the FLC shutter and the additional pulses, ensuring the required action of them with preservation of a given (initial) form of the temporal optical response of the FLC shutter are given. The principal operability of the method was experimentally tested. Physical properties and the substance of the FLC shutter layer used in the experiment are described.

Keywords: ferroelectric liquid crystal, FLC, optical shutter, ion charge, control voltage