Browse Prior Art Database

Gray Scale TFT/LCD Driving

IP.com Disclosure Number: IPCOM000103956D
Original Publication Date: 1993-Feb-01
Included in the Prior Art Database: 2005-Mar-18
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Matino, H: AUTHOR

Abstract

Disclosed is a driving method for gray scale TFT/LCD using a combination of area modulation or dither method and frame modulation method while liquid crystal itself is driven by binary.

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This is the abbreviated version, containing approximately 70% of the total text.

Gray Scale TFT/LCD Driving

      Disclosed is a driving method for gray scale TFT/LCD using a
combination of area modulation or dither method and frame modulation
method while liquid crystal itself is driven by binary.

      The methods to obtain gray scale are (1) analog driving, (2)
area modulation or dither, or (3) frame number modulation for
TFT/LCD.  In analog driving, liquid crystal is driven by analog
voltage and tilted various angles as applied analog voltages.  Front
of screen quality especially from tilted viewing angle is very poor.
Also, integration circuities for analog driver requires analog
circuit and therefore higher cost.  Pure dither method requires
multidivision for each pixel.  For color display, the number of this
division is multiplied by three times.  Smallest pixel size is too
small and would not be practical for 16 level gray scale because of
very small aperture ratio and low brightness.  Frame modulation
method introduces flicker problem or higher frame frequency which is
costly in driver IC's.

      The disclosed technique presents practical solution by using a
combination of dither method and frame modulation method while liquid
crystal itself is driven by binary.  One of the applications of this
technique is shown in the Figure for color display.

      In the example, area density modulation with 4 levels, for each
color, by using two divisional areas wherein the ratio of their sizes
is 1:2 is selected as one of area d...