Rendering, Adaptation and 3D Displays - 3DTV: Processing and Transmission of 3D Video Signals - page 146

display Full-HD (1920 1080) resolution content. However, a viewer is

still able to see a Full-HD video, when the left-eye view is combined
with the right-eye view. Another drawback with the special film-coated
passive stereoscopic 3D displays is that the black bars that separate the
horizontal and vertical stripes on the passive filter can sometimes give
rise to notable and visually distracting stepping effects on the displayed
stereoscopic view.

×

5.4.3 ActiveStereoscopicDisplays

Unlike the passive stereoscopic 3D displays that are presented in the previous
section, in active stereoscopic 3D displays, it is the special liquid crystal
''shutter'' glasses that have the primary role in creating the 3D depth effect.
Furthermore, this kind of displays deploys a ''time-division'' stereoscopic 3D
displaying mechanism unlike the ''space-division'' method used by passive
stereoscopic 3D displays.
Two other major differences from passive polarized stereoscopic 3D
displays are: the displays need much higher temporal resolution (i.e.
refresh/frame rate) in order to be able to divide the temporal frequency
for both eyes and the eye-glasses require special material and hardware
circuitry. In Figure 5.15, a pair of a passive-circularly polarized glasses and a
pair of active shutter glasses are shown side by side. It can easily be seen that
active shutter glasses look heavier and more complex than passive-polarized
glasses. Active stereoscopic displays arrived on the 3D consumer display
market earlier than their passive stereoscopic competitors.
The glass for both eyes contains a liquid crystal layer. This special layer has
the ability to change from light to dark (and vice versa) when electric voltage
is applied to it. Exploiting this ability of the liquid crystal glasses, both eyes'
glasses are periodically lightened and darkened in an alternating manner, and
in synchronicity with the 3D displays' screen refresh cycle. The 3D display
alternately displays the left-eye and the right-eye views in a time-divided
manner at a higher frame rate than the original stereoscopic video.
The synchronization is typically accomplished using a stereo connector
attached to the graphic processor that communicates either directly with
the glasses or via a wireless. This communication comprises sending the
appropriate timing signals for switching the glasses on and off. The glasses

Figure 5.15 RealD 3D style circularly polarized glasses (left), and generic
active shutter glasses (right)