Quality Assessment - 3DTV: Processing and Transmission of 3D Video Signals - page 161

Convergence
Binocular convergence is based on the fact that in order to project images on
the retinas, the two eyes must rotate inward toward each other. The closer
the perceived object is, the more they must rotate, so the brain uses the
information it receives about the degree of rotation as a cue to interpret the
distance of the perceived objects. This depth cue is effective only for short
distances (less than 10 metres).

BinocularParallax
As our eyes see the world from slightly different locations, the images sensed
by the eyes are slightly different, as shown in Figure 6.7. This difference in
the sensed images is called binocular parallax. The HVS is very sensitive to
these differences, and binocular parallax is the most important depth cue for
medium viewing distances. A sense of depth can be achieved using binocular
parallax even if all other depth cues are removed.
MicroHeadMovements
This depth cue is related to movement parallax, but is much less apparent than
the previously described motion parallax effects. Neuroscientists' research
in the field of human reception of 3D found that binocular parallax in itself
is not enough for the brain to understand the 3D space [8]. A brain area, the
anterior intraparietal cortex (AIP), integrates binocular and motion parallax
[9]. As soon as the brain thinks that it sees a 3D image, it starts working as if
in a normal 3D world, employing micro head movements to repeatedly and
unconsciously check the 3D model built into our brain. When the displayed
3D image is checked and the real 3D world mismatches the 3D image, the
trick is revealed. Presumably the AIP cortex never got used to experiencing
such 3D cue mismatch during its evolution, and this mismatch produces
unwanted effects.

α

Viewing
distance

Depth

Left

Fixation
point P

α

β

β

Q

Right

Figure 6.7 Binocular parallax