Virtual Reality - What it is and How it Works

Imagine being able to point into the sky and fly. Or
perhaps walk through space and connect molecules together.
These are some of the dreams that have come with the
invention of virtual reality. With the introduction of
computers, numerous applications have been enhanced or
created. The newest technology that is being tapped is that
of artificial reality, or "virtual reality" (VR). When
Morton Heilig first got a patent for his "Sensorama
Simulator" in 1962, he had no idea that 30 years later
people would still be trying to simulate reality and that
they would be doing it so effectively. Jaron Lanier first
coined the phrase "virtual reality" around 1989, and it has
stuck ever since. Unfortunately, this catchy name has
caused people to dream up incredible uses for this
technology including using it as a sort of drug. This became
evident when, among other people, Timothy Leary became
interested in VR. This has also worried some of the
researchers who are trying to create very real applications
for medical, space, physical, chemical, and entertainment
uses among other things.

In order to create this alternate reality, however, you
need to find ways to create the illusion of reality with a
piece of machinery known as the computer. This is done with
several computer-user interfaces used to simulate the
senses. Among these, are stereoscopic glasses to make the
simulated world look real, a 3D auditory display to give
depth to sound, sensor lined gloves to simulate tactile
feedback, and head-trackers to follow the orientation of the
head. Since the technology is fairly young, these
interfaces have not been perfected, making for a somewhat
cartoonish simulated reality.

Stereoscopic vision is probably the most important
feature of VR because in real life, people rely mainly on
vision to get places and do things. The eyes are
approximately 6.5 centimeters apart, and allow you to have a
full-colour, three-dimensional view of the world.
Stereoscopy, in itself, is not a very new idea, but the new
twist is trying to generate completely new images in real-
time. In 1933, Sir Charles Wheatstone invented the first
stereoscope with the same basic principle being used in
today's head-mounted displays. Presenting different views
to each eye gives the illusion of three dimensions. The
glasses that are used today work by using what is called an
"electronic shutter". The lenses of the glasses interleave?h)0*0*0*???the left-eye and right-eye views every thirtieth of a
second. The shutters selectively block and admit views of
the screen in sync with the interleaving, allowing the
proper views to go into each eye. The problem with this
method though is that you have to wear special glasses.

Most VR researchers use complicated headsets, but it is
possible to create stereoscopic three-dimensional images
without them. One such way is through the use of lenticular
lenses. These lenses, known since Herman Ives experimented
with them in 1930, allow one to take two images, cut them
into thin vertical slices and interleave them in precise
order (also called multiplexing) and put cylinder shaped
lenses in front of them so that when you look into them
directly, the images correspond with each eye. This
illusion of depth is based on what is called binocular
parallax. Another problem that is solved is that which
occurs when one turns their head. Nearby objects appear to
move more than distant objects. This is called motion
parallax. Lenticular screens can show users the proper
stereo images when moving their heads well when a head-
motion sensor is used to adjust the effect.

Sound is another important part of daily life, and thus
must be simulated well in order to create artificial
reality. Many scientists including Dr. Elizabeth Wenzel, a
researcher at NASA, are convinced the 3D audio will be
useful for scientific visualization and space applications
in the ways the 3D video is somewhat limited. She has come
up with an interesting use for virtual sound that would
allow an astronaut to hear the state of their oxygen, or
have an acoustical beacon that directs one to a trouble spot
on a satellite. The "Convolvotron" is one such device that
simulates the location of up to four audio channels with a
sort of imaginary sphere surrounding the listener. This
device takes into account that each person has specialized
auditory signal processing, and personalizes what each
person hears.

Using a position sensor from Polhemus, another VR
research company, it is possible to move the position of
sound by simply moving a small cube around in your hand.
The key to the Convolvotron is something called the "Head-
Related Transfer Function (HRTF)", which is a set of
mathematically modelable responses that our ears