Environmental Engineering Reference
In-Depth Information
3.1.1 Head Mounted Display (HMD)
This is a headset used for full immersion. It can contain a pair of goggles or a full helmet. In
front of the eyes are two tiny monitors that present images in three dimensions. Most HMDs
include a head tracker so that the system can respond to head movements. The small
monitors placed in front of each eye provide stereo, bi-ocular or monocular images. The
Stereo images come in a similar way to shutter glasses as only a slightly different image is
presented to each eye. The major difference is that the two screens are placed very close (50-
70mm) to the eye, while the HMD optical system keeps the image which the wearer focuses
on much further away. Bi-ocular images can present identical images on each screen while
monocular images are formed using only one display screen.
The most commonly used HMDs employ small Liquid Crystal Display (LCD) panels which
provides enough screen resolution for many applications, but the more expensive ones
employ Cathode Ray Tubes (CRT) that increase the resolution of the screen image. Fully
immersive systems usually exclude the user's view of the real world and enhance the field
of view of the computer generated world. The advantage of this method is that the user is
provided with a 360° field of regard giving them a visual image in whatever direction they
turn their head. The HMDs are central to achieving the sense of full immersion; hence their
resolution, the update rate, and contrast and illumination of the display are critical factors.
Fig. 2. Virtual Reality Headsets
3.2 Non-immersive environments or desktop systems
These are the least immersive implementation of virtual simulation techniques. With
Personal Computers on the desks, the virtual environment is created through a portal or
