Addressing smectic displays

Claim 1

l.A display device incorporating a matrix-addressed smectic cell whose pixels are addressed by means of a strobe pulse applied to successive rows in sequence, and in synchronisation with the parallel input of data pulses to the column electrodes, characterised in that the voltage excursion of the data pulses is less than the threshold voltage value V T , sufficient just to switch the cell if applied across its electrodes for an infinitely long period, that the device includes means for switching the addressing of the cell between a whole row entry mode and a segmented row entry mode, and that in the whole row entry mode the pulses are of relatively shorter duration and the voltage excursion of the strobe pulses is greater than twice V T , while in the segmented row entry mode the pulses are of relatively longer duration and the voltage excursion of the strobe pulses is less than twice V T .

Claim 2

A method of operating a display device incorporating a matrix addressed smectic cell, wherein the pixels of the cell are addressed by means of a strobe pulse applied to successive rows in sequence, and in synchronism with the parallel input of data pulses to the column electrodes, characterised in that the voltage excursion of the data pulses is less than the threshold voltage value, V T, sufficient just to switch the cell if applied across its electrodes for an infinitely long period, that for data that is to be entered a whole row at a time, the data pertaining to a row is, having first erased that row, entered using a strobing pulse of relatively shorter duration whose voltage excursion is greater than twice V T , and that for data that is to be entered into a row in a sequence of time-spaced segments the data pertaining to a row is entered using a sequence of strobing pulses of relatively longer duration whose voltage excursion is less than twice V T , only the first member of the sequence being preceded by the erasure of that row.