Browse Prior Art Database

Back Light Power Reduction by Optimizing Gray Level Range of Software

IP.com Disclosure Number: IPCOM000119105D
Original Publication Date: 1997-Nov-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 168K

Publishing Venue

IBM

Related People

Itoh, H: AUTHOR

Abstract

Disclosed is a method of optimizing an actual using range of Gray Level of any Software (S/W) Application up to a maximum upper side range of Gray Level of the using LCD module. At the same time, in order to keep the same brightness using the S/W application, on a normal LCD module, this method makes the brightness of the Backlight darker than normal. This method reduces power consumption of the backlight. By the way, in the case of an almost low brightness screen, like the DOS prompt or some S/W application, by compressing the higher gray levels which are not used in the DOS prompt or some S/W, this method can reduce power enormously by reducing the brightness and Backlight power evenly.

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Back Light Power Reduction by Optimizing Gray Level Range of Software

      Disclosed is a method of optimizing an actual using range of
Gray Level of any Software (S/W) Application up to a maximum upper
side range of Gray Level of the using LCD module.  At the same time,
in order to keep the same brightness using the S/W application, on a
normal LCD module, this method makes the brightness of the Backlight
darker than normal.  This method reduces power consumption of the
backlight.  By the way, in the case of an almost low brightness
screen, like the DOS prompt or some S/W application, by compressing
the higher gray levels which are not used in the DOS prompt or some
S/W, this method can reduce power enormously by reducing the
brightness and Backlight power evenly.  At this time, this method
also has effects  whereby White defect dot pixels are hard to be
seen, because of reduction  in brightness of the LCD module.
  1.  Optimization in typical middle gray level
      'aLxx' means gray level XX (ex: L30 means gray level 30)aa
       and 'L(typ)' means typical(average) gray level during
       sampling time (ex. 10 seconds or 1 minutes).
         Fig. 1 shows that using range of input gray level and
       transparency are in the case of L(typ)=L30(typical middle
       gray level).  At first, using range of input gray level and
       transparency of Fig. 1 are optimized up to the maximum side
       gray range of LCD module (LCD's max gray level is 'L64'
       &'T64').  Then, as input gray level is L, and as L' is
       optimized L, also as input transparency is T, and as T' is
       optimized T.  In the case of Fig. 1, according to the
       liner L(gray level)-T(Transparency) characteristics, as
       optimization function parameter is F(x):
        L'(max)/L(max)=T'(max)/T(max)=F(x)
        L'(min)/L(min)=T'(min)/T(min)=F(x)
        L'(typ)/L(typ)=T'(typ)/T(typ)=F(x)

          As an example, optimization function parameter in the case
of Fig. 2 is F(x)=7/5.  As normal the Brightness of Backlight is B,
and as the brightnes...