Browse Prior Art Database

Auxiliary Lighting Device for Reflective Liquid Crystal Displays

IP.com Disclosure Number: IPCOM000118443D
Original Publication Date: 1997-Feb-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Mamiya, J: AUTHOR [+3]

Abstract

Disclosed is a device that is to be used as an auxiliary light source for a reflective Liquid Crystal Display (LCD). This device is installed on top of the display area of a reflective LCD, as shown in the Figure. The device is turned on when there is insufficient ambient light for the reflective LCD to yield good quality image and is turned off when there is sufficient light input. A high degree of light transmissibility of this device is an advantage because, therefore, it does not affect the image quality of the LCD.

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Auxiliary Lighting Device for Reflective Liquid Crystal Displays

      Disclosed is a device that is to be used as an auxiliary light
source for a reflective Liquid Crystal Display (LCD).  This device is
installed on top of the display area of a reflective LCD, as shown in
the Figure.  The device is turned on when there is insufficient
ambient light for the reflective LCD to yield good quality image and
is turned off when there is sufficient light input.  A high degree of
light transmissibility of this device is an advantage because,
therefore, it does not affect the image quality of the LCD.

      The main component of this device is a light guide which has
inside tilted surfaces facing downward toward the LCD, as shown in
the Figure.  An internal surface's adjoining two media's refraction
indeces are to be close (i.e., 1.5 and 1.55).

Two important characteristics derived from this construction are:
  1.  Light traveling horizontally within the light guide will be
       reflected at internal surfaces and directed downward.
  2.  Light traveling vertically passes through the light guide.
       The transmission rate in this direction perpendicular to
       the surface is over 90%.

      When the device is turned on, the input light from the lamp is
reflected at the internal surfaces and directed toward the reflective
LCD.  The light travels into the LCD and reflects back again upwards
out of the LCD.  Light will then pass through...