Information Technology Reference
In-Depth Information
(a)
(b)
Figure 6: Visual expressions (a) and the extracted features (b) for three base
emotions (one per row) [10].
As an example, completely open eyes where lower eyelids are down,
while eyebrows are raised and curved indicate surprise. Eye images should be
acquired using high-resolution colour cameras.
Figure 6(a) shows the eye regions corresponding to anger, surprise and
happiness. Figure 6(b) shows irises, eyelids and eyebrows extracted from the
images on the left side.
3.1.3
Visual perception
Eye-gaze tracking to evaluate the user's cognitive status relies on the
immediacy assumption (people elaborate pieces of information while they are
looking at them) and on the eye-mind assumption (the eye is fixed on a
particular object while it is being analysed). There are several eye-gaze
tracking methods. If we focus on data collected from eyes directly, there are
two main techniques:
•
detection of the corneal reflection from a lit eye and
•
iris recognition from eye pictures.
One can choose between these two approaches on the basis of the external
lighting conditions. Moreover, there are three methods to compute fixations.
The first one implies simple computations because it relies on fixed
geometry. In this case, the users have to hold their head still using a restraint.
In the second technique, the user wears a head-tracking sensor that is able to
detect 3D position and attitude of the head and merges them with the data
about the eye direction. The third technique uses an eye-tracking device and a
