Importance Of Eye Tracker Devices

Eye tracking is a technique whereby an individual’s eye movements are measured, so it can indicate where the person is looking at certain time and the order in which their eyes transition between area of interest (saccade).[30]
There are two main parts must be considered, when study gaze behavior in any field, which are eye tracker device, and algorithms, in addition to this a functional task according to specific field must determine by experts to give indication about something related to aim of study.
Eye Tracker Devices
Old Devices
Eye tracker device is an equipment determine where person looking, by project a certain sign on the scene, which is gaze sign, eye tracker devices starts with non-usable designs such as contact lens based

[30] Figure ‎1 55 Purkinje Image which show the effect of the infrared light on the eye, the pupil will be bright and there will be a corneal reflection point on the eyes.[30]
After detect the center of pupil and the corneal reflection, the vector between them is used to determine the gaze direction as shown in Figure ‎1 56, This technique has ability to eliminate the optical reflective effect of accessories and glasses.[36] Figure ‎1 56 Example on the direction of line sight , calculated depend on the relation between the center of pupil and corneal reflection. Eye tracking using dark and bright pupil effect
Figure ‎1 57 shows the dark and bright pupil, the location of the dark pupil is determined by the image captured by the camera but this difficult the person has dark brown eyes because of the low contrast between the brown iris and the black pupil, bright pupil is caused by infrared light as explained in