The perfect mobile display

[Colin Dunstan]

The Feature is examining various display technologies that are currently on the market. Here is a summary:

LCD type I: a transmissive display, works by shining a fluorescent backlight through a sandwich of glass and liquid crystal material. Fine for use indoors, but when you step outside in the daytime, you have to take your sunglasses off to use them.

LCD type II: a reflective display, uses a frontlight. When the frontlight happens to be the sun, the resulting image is good. But in a low light condition, a reflective display has to use its built-in frontlight, and the quality is worse than a transmissive display.

LCD type III: a transflective display, uses a backlight -- just like a transmissive display -- but can also use bright outdoor light to improve readability. An increasing number of mobile phones are using transflective displays (TFT LCDs) because it offers a compromise between transmissive and reflective displays.

Bistable (aka e-paper): very low power-consumption and excellent legibility in both very bright and medium-light condition; alas very slow refresh rates. Examples: Boston's E-Ink, SiPix in Fremont, California, Dublin's Ntera, Nemoptic in France, ZBD in Worcester, and Kent Displays from Ohio

OLED: organic light-emitting diode, generates light when a current is applied. Better than LCDs on some counts -- such as lower power consumption and a faster refresh rate -- but they do an even worse job than LCDs in bright sunlight, because they don't crank out enough nits to do the job. OLED pigments tend to fade over time, giving them a shorter life than LCDs.

Others: iModD developed by Qualcomm uses iridescence to produce colors - in the the same way a butterfly's wings give off metallic looking hues. Uses reflected light, so it will work well in sunlight, and reduces power consumption.