Game Development Reference
Figure 24-7. Wire-grid polarization
Early 3D display systems used linearly polarized light to separate the right eye channel
from the left eye channel. However, there is one problem with using linear polarizers.
It follows that if you place another wire-grid polarizer after the first, with its wires rotated
90 degrees, no light will pass through! In fact, if you have an old pair of sunglasses or
3D glasses and you hold the right eye lens against the left eye lens, you won't be able to
see anything. That is because each filter is blocking out one direction of oscillations,
preventing any light from coming through. If you rotated one of the lenses, then the
combined lens will lighten as you align the polarization directions. The problem with
these types of lenses is that if you were watching a movie and tilted your head to one
side, the same effect would occur and the image would be greatly dimmed. This means
your date could no longer rest his or her head on your shoulder while watching the
movie. Something had to be done.
Circular polarization is another form of filtering out certain orientations so that you
can control which light beams pass through which lens. However, in this case the di‐
rection of oscillation is not a single orientation but more accurately a pattern of oscil‐
lations parameterized by time. The first step to achieve circular polarization is to send
the light through a linear polarizer as just discussed. That light is then sent through what
is known as a quarter-wave filter . A typical arrangement is shown in Figure 24-8 .