Evaluating Eye Tracking Systems for Computer Input
Although visual displays are the most common, it is also valid to speak of "auditory displays" or "tactile displays". These are outputs from the machine or computer that stimulate the human sense of hearing or touch, respectively. Human motor responses come by way of our fingers, hands, arms, legs, feet, and so on, and are used to control the machine or computer. Of course, speech or articulated sounds are also human responses and may act as controls to issue commands to the computer or machine.
Today, computing technology is pervasive and ubiquitous. Computers are used by humans for work and pleasure, in tasks both complex and trivial, and for pursuits mundane, challenging, and creative. Eye trackers are just one example of a computing technology that offer tremendous potential for humans. Applications for eye trackers can be divided along two lines. In one application, an eye tracker is a passive instrument that measures and monitors the eyes to determine where, and at what, the human is looking. In another, the eye tracker is an active controller that allows a human, through his or her eyes, to interact with and control a computer. When a human uses an eye tracker for computer control, the "normal course of events" changes considerably. The eye is called upon to do "double duty", so to speak. Not only is it an important sensory input channel, it also provides motor responses to control the computer. A revised schematic of the human-computer interface is shown in Figure 2. The normal path from the human to the computer is altered. Instead of the hand providing motor responses to control the computer through physical devices (set in grey), the eye provides motor responses that control the computer through "soft controls" – virtual or graphical controls that appear on the system's display.
Figure 2. The human-computer interface. With an eye tracker, the eye serves double duty, processing sensory stimuli from computer displays and providing motor responses to control the system
