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Method for Forming a Reciprocal Filter to Provide Uniform Luminance of a Liquid Crystal Display

IP.com Disclosure Number: IPCOM000114631D
Original Publication Date: 1995-Jan-01
Included in the Prior Art Database: 2005-Mar-29
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Cone, JM: AUTHOR

Abstract

Disclosed is a method for forming a reciprocal filter to be placed over a Liquid Crystal Display (LCD) screen to compensate for localized variations in the luminance of the screen, whether such variations are caused by local differences in the level at which the LCD is illuminated, or by variations in the transmittance of certain groups of cells in the LCD.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 74% of the total text.

Method for Forming a Reciprocal Filter to Provide Uniform Luminance
of a Liquid Crystal Display

      Disclosed is a method for forming a reciprocal filter to be
placed over a Liquid Crystal Display (LCD) screen to compensate for
localized variations in the luminance of the screen, whether such
variations are caused by local differences in the level at which the
LCD is illuminated, or by variations in the transmittance of certain
groups of cells in the LCD.

      This method is applied to a backlit LCD by exposing a sheet of
negative photosensitive material coated on a transparent substrate,
such as a sheet of photographic film held in contact with the front
surface of the LCD, to light transmitted through the LCD with the
backlight and all pixels of the LCD turned "on."  Alternately, the
photosensitive material may be exposed through a lens to the light
emitted by the LCD.  The photosensitive material is then developed,
in the classical photographic sense, with the areas receiving more
illumination during exposure having a higher absorption density after
development.  A number of parameters, such as the time of exposure,
the time of development, the type of film used, and the chemical
mixture used for development, may be varied to obtain a reciprocal
filter compensating for nonuniformities in illumination.  The
developed film is subsequently used as a filter, being placed
adjacent to the LCD.  For example, the film may be placed between the
backlight and the...