The principal channel of interactive communication from a computer to a person is an electronic display. The amount of information shown and the way in which it can be exhibited depend on successfully matching the capabilities of the display to the human visual system. Making this channel as wide, as fast, and as effective as possible has been the goal of electronic display development for the last fifty years. The cathode ray tube (CRT), which has been the dominant display device used in offices and homes, is the display device on which the personal computer and the graphical user interface were developed. Today, the capabilities of information technology are brought to new environments by new display technologies. Active-matrix liquid crystal displays (AMLCDs) have freed the personal computer from the desktop, projection displays bring the power of information technology into meetings, small liquid crystal displays have allowed the development of hand-held computers, and head-mounted displays are bringi ng wearable computer technology onto the factory and warehouse floor.