Visual Discomfort in 3DTV: Definitions, Causes, Measurement, and Modeling - Novel 3D Media Technologies - page 187

2 and 6 % significantly affected image quality and visual comfort.” In [ 18 ], they
found “crosstalk level of about 5 % is sufficient to induce visual discomfort in half of
the population.” In [ 28 ], they reported that the crosstalk tolerance limit is 5-10%, and
visual detection limit is 1-2 %. In [ 29 ], it is shown with natural still images that the
S-3D display technology with the lowest luminance and contrast level tolerates the
highest level of crosstalk, while still maintaining an acceptable image-quality level.
10.2.4 Motion
Motion in 3DTV can be classified into planar motion (or lateral motion) and
in-depth motion. Planar motion means that the object only moves in a certain
depth plane perpendicular to the observer, and the disparity does not change
temporally. In-depth motion, which is also called motion in depth or z-motion, is
defined as object movement toward or away from an observer [ 30 ]. For planar
motion, both eyes make the same conjunctive eye movements, called version
[ 31 ]. For in-depth motion, the eyes make opposite, disjunctive eye movement,
called vergence [ 32 ]. The eye movements for the planar motion and in-depth
motion are shown in Fig. 10.2 . The speed of the planar motion and in-depth motion
can be expressed by the change of distance per second or the change of the visual
angle (version or vergence) per second.
Fast motion can induce visual discomfort even if the object is within the
comfortable viewing zone [ 9 , 11 ]. Studies showed a consistent conclusion on the
influence of motion velocity on visual discomfort, i.e., visual discomfort increases
with the in-depth motion velocity [ 9 , 11 , 12 , 31 ], and for planar motion video
sequences, visual discomfort increases with the planar motion velocity [ 12 , 33 ].
Fig. 10.2 The left figure shows the eye movement of the planar motion object. Planar motion
velocity is the amount of the change of the version per second. The right figure shows the eye
movement of the in-depth motion object. In-depth motion velocity is the amount of the change of
the vergence per second. A N represents the perceived virtual object at frame N , and A N and A N
represent the left and right view images at frame N