A virtual retinal display (VRD) is a head-mounted display system that projects an image directly onto the human retina with low-energy lasers or LCDs. VRDs can give the user the illusion of viewing a typical screen-sized display hovering in the air several feet away. In principle the technology can provide full-color, high-resolution dynamic displays, but in practice the components necessary to achieve the full potential of the technology are either highly expensive or simply not built yet. Although the technology was invented by the University of Washington in the Human Interface Technology Lab (HIT) in 1991, development did not begin until 1993; the technology still needs much refinement and has only been commercialized in specialized sectors of the display market such as automobile repair and some parts of the military.
A VRD unit consists of 4 modules; drive electronics to break down an incoming source image into an information stream, a light source made up of laser(s) or LED(s), a scanner bank made up of horizontal and vertical scanners, and a lens to expand the image that projects through the scanners. As in a television, the scanners rapidly oscillate left-to-right or down-to-up, selectively permitting colors through in precise configurations that produce a high-resolution 2mm x 2mm field of pixels. Then a lens acting as an expander boosts the size of the image to something like 18mm x 18mm, allowing for a larger and more natural image. The pixel field is then projected onto the eye, where the eye's lens focuses the image onto the retina. Aside from tapping into the optic nerve itself, there may be no more effective way to display an image.
The virtual retinal display is highly efficient with respect to power consumption, requiring far less power than the postage-stamp LCD screens used commonly in today's mobile devices. A VRD display uses about a microwatt of power. Since VRD displays project images directly onto the retina, they provide a sharp, clear image regardless of external lighting conditions. VRD displays require a fraction of the hardware of conventional display devices, allowing for lighter and more elegant mobile devices, in high demand for today's electronics market. VRD shows strong potential to replace LCD screens in cell phones, handheld computers, handheld gaming systems, and eventually even larger computers such as laptops.
VRD technology is being exclusively commercialized by the Seattle-based tech company MicroVision, Inc. Two products available so far include Nomad(tm), a head-mounted VRD system that displays a monochromatic overlay of relevant information to a task at hand, and Flic(tm), a laser bar code scanner. Nomad uses Windows CE and the 802.11b wireless protocol. As the components of VRD displays decrease in cost and the manufacturing processes used to create them improve, distribution of the product will surely expand to a very large market.
