Multiplexed liquid crystal display having a gray scale image

Details Multiplexed liquid crystal display having a gray scale image Multiplexed liquid crystal display having a gray scale image

1981-08-31

1984-01-24

Trafton, David L.

Communications: electrical

Land vehicle alarms or indicators

Internal alarm or indicator responsive to a condition of the...

340793, 350333, 358236, G09G 336

Patent

active

044279787

ABSTRACT:
A field effect liquid crystal display is disclosed wherein an composite alternating voltage is successively produced across a matrix of pixels formed by crossed arrays of row and column electrodes of the display. The composite alternating voltage consists of a row driving alternating voltage component and a column driving alternating component voltage. The phases of the row and column alternating voltage components are relatively phased so as to produce the composite alternating voltage across the individual pixels. The column alternating voltage component includes a gray scale component having an (root mean square) RMS value variable in accordance with the gray scale of the image to be displayed on the liquid crystal display. Two systems are disclosed for deriving the composite RMS voltage having the gray scale component. In an analog system, an alternating square wave video signal is compared with a triangular wave to convert the gray scale video signal into a phase modulated square wave which is then fed to the column electrodes for summing with the row alternating voltage signals to derive a composite alternating voltage for energizing the respective pixels. In a second embodiment, the video analog signal is fed to an analog-to-digital converter and then to a serial-to-parallel shift register for deriving gray scale words fed to respective column counters to produce an output column drive signal having a phase modulated component variable in accordance with the gray scale of the image to be displayed.

REFERENCES:
patent: 3776615 (1973-12-01), Tsukamoto et al.
patent: 3838209 (1974-09-01), Tsuchiya et al.
patent: 4180813 (1979-12-01), Yoneda

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