Electronic displays

Claim 1

A polar coordinate plotter comprising the cooperative combination of: a display including a set of concentric spiral electrodes and a set of radial electrodes arranged opposite one another and disposed either side of an electrically sensitive medium of dyed phase change liquid crystal material, the electrodes defining by their overlap a display area formed of a matrix of intersections; an address signals source for providing a set of four signal waveforms V 1 , V 2 , V 3 and V x ; a first multiplex address control, responsive to co-ordinate data, connected to the radial electrodes, for applying one of the two signals V 1 or V x to each radial electrode in turn, whilst at the same time applying the signal V x to all other radial electrodes; and, a second multiplex address control, responsive to coordinate data, connected to the spiral electrodes, for applying to these all each in turn selected signals V 1 , V 2 and V 3 ; the set of four signal waveforms V 1 , V 2 , V 3 and V x having the following conditioned interelationships: RMS(V.sub.x -V.sub.1)=RMS(V.sub.x -V.sub.2)=RMS(V.sub.x -V.sub.3)=V.sub.p ; RMS(V.sub.1 -V.sub.2)=V.sub.p ; RMS(V.sub.1 -V.sub.3)=V.sub.o ; where V p is an upper threshold voltage, and V o a saturation voltage, for dyed phase change hysteresis.