An analysis of possible drive schemes for complex liquid-crystal displays

Abstract

The paper is concerned with the problem of generating complex patterns on two-dimensional liquid-crystal arrays, without either an excessive number of control terminals or prohibitively complex control circuits. Following a brief introduction to the operating principles of liquid-crystal displays, the initial Section indicates how the problem could be solved using a two-dimensional shift-register/liquid-crystal sandwich—if the technology were available. Succeeding Sections then derive and analyse efficient ways of arranging and driving sets of parallel X and Y conductors to generate desired display patterns. Particular attention is given to the examples of generating arrays of 7×5 dot matrix symbols, and of generating single two- or three-valued waveform displays. Drive sequences within the response speed of the liquid crystals are shown to be feasible for character displays, and to have the advantage of simplicity and tolerance to variations in operating conditions. Mean-squared, slow-response drives are shown to be more widely applicable and to provide superior visual performance in certain conditions, providing that the ratio of the mean-squared white-to-black voltages is adequate.