"Down inside the computer are three lasers - a red one, a green one,
and a blue one. They are powerful enough to make a bright light, but not powerful
enough to burn through the back of eyeball and broil your brain, fry your
frontals, lase your lobes. As everyone learned in elementary school, these
three colours of light can be combined, with different intensities, to produce
any colour that Hiro's eye is capable of seeing."
Snowcrash, page 22
VRD or Virtual Retinal Display is an offshoot of HMD display technology, which,
instead of placing a pair of display screens in front of the eyes, actually
projects an image directly onto the human retina with low-energy lasers or LCDs.
A Virtual Retinal Display thus bypasses the eye almost completely, itself doing
all the work to refocus, and just delivering the result. This bypasses the eyestrain
problems of looking at a 3D image on a 2D display, and trying to focus on an
image that is perceived to be further away. . In principle the technology can
provide full-colour, high-resolution dynamic displays, but in practice the technology
is simply not advanced enough yet.
The original technology was was invented by the University of Washington in
the Human Interface Technology Lab (HIT) in 1991, however the technology at
the time was not sufficient for practical use.
VRD displays are actually a lot less complex than flatscreens to create, requiring
a fraction of the hardware components. This has the effect of making the display
systems much lighter and more reliable - even if the components they use are
a lot more intricate than normal. Once the technology is fully realised, it
is very likely they will replace mobile phone, ipod, and other such handheld
display systems very quickly, moving to other systems from there.
In the modern, power-centred world, it is worth noting that a VRD is much more
efficient than CRT or LCD flatscreens, and requires much less power than even
a mobile phone display. Using about a microwatt of power to run and fill an
entire eye with vision, they provide a sharp, clear image regardless of external
A VRD system consists of four stages:
- Information Stream
- Laser / LED light source
- Scanner matrix: Rows of horizontal scanners interlaced with rows of vertical
- Lens to focus the image
The scanner bank oscillates like shutter glasses, allowing colour frequencies
to cycle past it, in sequence to build up a pixel display which is blasted through
the lens by the laser beams, and directly onto the retina of the eye, blanketing