LCD Back Light
Backlight systems for LCDs can be divided roughly into two types:
1. directly-under (reflective) systems, and
2. sidelight/edge light (light-guiding plate) types.
In the directly-under system a fluorescent lamp is positioned in a cage consisting of a reflective plate and diffusive plate, so that light from the lamp is reflected and scattered. Fluorescent lamp shapes in use include straight tubes, U-shaped and W-shaped lamps. A light curtain and a
diffuser are mounted over the lamps to reduce unevenness in brightness. Compared with other methods, the directly under system offers higher brightness.
Sidelight/edge light uses a straight CCFL lamp along one side of the LCD, or two lamps on opposite sides of the LCD, or L-shaped lamps along the opposite corners of the LCD. Edge light units use a reflector and light-guiding plate to direct light from the fluorescent lamp to the screen to evenly disperse light over the LCD. LCD panels using this backlighting technique are usually thinner and have good average brightness. In addition, greater ease in changing the lamp, and lower power consumption are also important features.
