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LCD backlight illumination uniformity compensation

IP.com Disclosure Number: IPCOM000218253D
Publication Date: 2012-May-30
Document File: 2 page(s) / 50K

Publishing Venue

The IP.com Prior Art Database

Abstract

Uniform illumination is an important quality for LCD displays. Hardware circuitry can be used to compensate luminance of the part of the screen which are nearer to the light source (e.g. the bottom part of the screen in a laptop).

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LCD backlight illumination uniformity compensation

LCD displays work by selectively blocking a background light on each pixel. Uniformity of backlight illumination is critical to reach a good quality of the displayed picture. The light source is almost always not as big as the entire screen; instead, for cost reasons, it is often limited to a simple lamp or LED array placed on one side of the LCD panel. For example, a typical notebook has a thin and long light source on the lower part of the screen.

For a typical LCD with a lamp on the bottom part of the screen light uniformity is currently achieved by using plastic shapes acting as lens and mirrors. This optical system is designed to carry sufficient light to the top part of the screen. Nonetheless it is usual to have a greater luminosity on the bottom part of the screen, which is much nearer to the light source. This is especially apparent when using the entire screen for movies or other uniform color cases; it is less evident in everyday use as the lower part of the screen is often used to show a virtual panel including a taskbar and some icons.

The problem of non-uniform illumination for an LCD has been approached with many technological means. An additional compensation strategy can be implemented by a cheap processing system applied to the displayed picture. This compensation consists of a direct modification of the RGB values which are displayed on the screen.

A first solution proposed here consists in maintaining the bottom rows of the image darkened to compensate the stronger back illumination of the area.

A second, more complex, solution includes processing...