Time integration grey scales for ferroelectric LCD'S

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Abstract
Although FLCD's basically are black-and-white displays, several methods have been suggested to obtain grey scales, e.g. time integration.1,2 However, most papers only state the general idea of making a same pixel consecutively black and white during one frame time, resulting in a grey impression due to the human eye's time averaging properties. Very few treat the subject in any further detail. In this note we derive row and column signals in order to obtain 8, 16, 32, etc. logarithmically spaced grey shades for an arbitrary matrix FLCD, by means of time integration multiplexing. Overall DC-compensation of every pixel voltage is guaranteed by the fact that all row and column pulse sequences are derived from a subset of the so-called Walsh functions. The feasibility of the method for displays filled with today's FLCD mixtures is demonstrated for a modest number of grey shades and matrix size. A second procedure has been developed, paying much attention to optimal switching times, so as to allow for a maximum number of grey levels and/or pixel rows.

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