Method and apparatus for multiplex addressing of a ferro-electric liquid crystal display

A method of multiplex addressing a ferro-electric liquid crystal matrix display formed by the intersections of a first set of electrodes and a second set of electrodes, said method comprising the steps of:

• applying a blanking waveform to each electrode in sequence in the first set of electrodes, said blanking waveform comprising a plurality of d.c. pulse of similar sign;
• applying a strobe waveform to each electrode in sequence in the first set of electrodes, said strobe waveform comprising a pair of strobe pulses of different amplitude, each strobe pulse lasting a single time slot duration ts;
• and
• applying one of two data waveforms to each electrode in the second set of electrodes coincidentally with the strobe waveform, both data waveforms being rectangular waveforms of alternate positive and negative values with one data waveform the inverse of the other data waveform, each data waveform value lasting a single time slot duration ts, wherein each intersection is addressed with a d.c. pulse of appropriate sign and magnitude to turn the intersection to a desired display state once per complete display address period.

A multiple addressed liquid crystal display comprising:

• a liquid crystal cell including a layer of ferro-electric smectic liquid crystal material contained between two walls, each wall bearing a set of electrodes, said electrodes in combination comprising a matrix of addressable intersections;
• driver circuits for applying data waveforms to one set of electrodes and blanking and strobe waveforms to the other set of electrodes in a multiplexed manner;
• waveform generators for generating data, blanking and strobe waveforms for applying to the drive circuits;
• means for controlling the order of data waveforms so that a desired display pattern is obtained;
• and
• means for sensing the liquid crystal temperature,
• said waveform generators include:
• a data waveform generator means for generating two sets of data waveforms of equal amplitude and frequency but opposite sign, each data waveform comprising d.c. pulses of alternate sign, each pulse lasting for a single time slot duration ts;
• a blanking waveform generator for generating blanking waveforms;
• and
• a strobe waveform generator means, responsive to said temperature sensing means, for generating strobe waveforms comprising a pair of strobe pulses of different amplitude, each strobe pulse having a duration coincident with and equal to said time slot duration ts, where amplitude and sign of a leading pulse in each strobe pulse pair is independently variable in response to sensed liquid crystal temperature to compensate for changes in liquid crystal temperature.