Eye tracking is the process of electronically locating the point of a person's gaze, or following and recording the movement of the point of gaze. Various technologies exist for accomplishing this task; some methods involve attachments to the eye, while others rely on images of the eye taken without any physical contact.
A special lens or film can be affixed to the cornea, incorporating precise position sensors to follow physical movements of the eye. A tiny mirror or electromechanical transducer, embedded in the lens or film, can use light beams or electromagnetic fields to quantify the eye's orientation and follow changes in gaze position. Such devices have proven sensitive and accurate, as long as they don't slip on the surface of the eye.
Eye position and movement can be detected remotely, without involving any attachments to the cornea. For most people, this method is preferred over mechanical methods because it is non-invasive and portable. A device called a microprojector transmits an infrared beam at the eye, and the reflection patterns are picked up by a set of sensors. The reflections may occur from the cornea or from the retina as the infrared beam passes through the lens, into the eye, and back out.
One of the earliest applications of eye-tracking was enabling computer access for the disabled. A device that pinpoints the gaze point on a computer screen can allow a quadriplegic to operate that computer by "pointing" with the gaze and "clicking" by blinking the eyelids or staring at a certain point on the screen for a length of time, thereby obtaining the functionality of a mouse. An on-screen keyboard and numeric keypad can allow for text typing and calculations, and continuous eye-movement tracking can allow the user to draw diagrams or create graphs.
Here are some other current or potential applications:
- Providing new features for e-readers, such as displaying dictionary definitions for words that the reader stares at for a certain length of time.
- Helping paralyzed people to operate wheelchairs and other mechanical devices.
- Alerting drivers when their gaze wanders off the road.
- Allowing surgeons to control instruments without touching them.
- Controlling common household appliances such as TV sets and Hi-Fi equipment.
- Diagnosing visual disorders by detecting abnormal gaze patterns.
- Development of new gaze-based or eye-movement-controlled video games.
- Helping marketers determine which parts of an advertisement people look at the most.
- Monitoring the eye movements of pilots in flight simulators.
- Remote control of drones and guided missiles.
- Detecting abnormal eye movements in SCUBA divers that might indicate nitrogen narcosis or oxygen deprivation.