A microdisplay is a video
screen smaller than that which would be used in a handheld
device like a cell phone or PDA
. They measure under a half an inch on the diagonal.
Microdisplays are used in near-eye applications like heads-up displays on helmets, virtual reality goggles, and in camera viewfinders.
Most microdisplays are simply tiny LCDs (liquid-crystal displays), but there are several new types:
Liquid Crystal on Silicon (LCoS)displays are made like LCDs, but instead of modulating light shone through them, the crystals change light reflected off of them. This technolgy is also being used in some of the latest projection TV sets.
Retina-scanning displays use a pivoting micromirror to actually scan an image on the user's retina much in the way an image is built up on a TV screen. The mirror steers low-power laser light in a raster pattern, and persistence of vision creates an image that appears to hover in the air in front of the viewer.
Organic Light-Emitting Diode (OLED) displays use newly-discovered carbon-based (hence "organic") molecules that emit light when current runs through them. A display of this type is being developed for the heads-up display in the Land Warrior system.