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HIGH PERFORMANCE LOW COST STEREO PROJECTOR
SYSTEM FOR VIRTUAL REALITY

Heikki Kosola, Karri Palovuori

Tampere university of Technology
Institute of Electronics
P.O.Box 692, 33101 Tampere,
Finland

ABSTRACT
This paper describes a novel method for producing projected stereo images with very high quality and
reduced cost. Using two standard LCD-projectors with an electro-mechanical shutter it is possible to
produce a time division multiplexed stereo image pair with a very high refresh rate. All beneficial
characteristics of the LCD-projectors like the spatial stability, good geometry and image sharpness are
preserved.

KEYWORDS

Stereo projection, Virtual reality, LCD, Shutter

INTRODUCTION
Motion and position compensated stereographic visualization is an almost essential requirement for
any virtual environment setup today. To produce projected stereographic image there are three main
techniques available: autostereoscopic, passive stereo and active stereo. In the autostereoscopic display
each pixel is divided to subpixels. Each subpixel has its own spatial sector where it can be seen.
Spectator's eyes see different set of subpixels and stereoscopic information can be shown. The demand
for unpractical number of subpixels and the required optics makes autostereoscopy an unthinkable
solution for a large virtual reality display.

The high cost of a stereo enabled CRT or DLP projector could be avoided by using passive methods to
separate the images between the viewer's two eyes. Word 'passive' means that user is not wearing
active shutter glasses to blank out the unwanted picture. Passive filters are used instead. Both images
are projected simultaneously on the screen. Separation is done typically by different polarization of the
two images. Both linear and circular polarization are used. Wavelength multiplexing is also used [1].
All of the projection techniques (CRT, DLP, LCD) could be used with passive stereo. Advantages of