What is eye tracking?
In its most fundamental form eye tracking is the human process of watching another person and where this person is looking. It’s a natural part of human behavior and, with the innovation of highly accurate eye tracking technology, it has become widely used, both to understand human behavior and to enhance computer interaction.
Eye tracking step by step
An eye tracker is a device that uses projection patterns and optical sensors to gather data about gaze direction or eye movements with very high accuracy. Most eye trackers are based on the fundamental principle of corneal-reflection tracking:
The eye gaze provides a very efficient way of pointing. We do it all the time in interaction with other humans. Eye tracking technology enables us to use our gaze in interaction with computers and machines. It's fast, intuitive and natural.
What can be tracked?
- Gaze direction and gaze point - used in both gaze interaction with computers and other interfaces, and in behavioral research/human response testing to better understand what attracts peoples’ attention. The eye tracker provides high precision at a detailed level.
- Eye presence detection - finding the eyes is the first thing the eye tracking system does and is therefore a fundamental part of eye tracking. It is also used in specific features, such as power saving by dimming the screen when eyes are not present etc.
- Eye position - the ability to calculate the position of the eyes in real time is part of what makes the eye tracking system accurate and precise while allowing the user to move freely. Eye position tracking is used to render 3D images to the user without the use of glasses, as in the Tobii EyeAsteroids in 3D.
- Eye identification - the eye tracker identifies individual eye features based on geometry through a quick calibration. Geometrical eye features and iris identification can also be used for user identification, driver identification, and automatic logon to your home PC.
- Eyelid closure - is used to monitor people’s attention or sleepiness, for instance in advanced driver assistance or operator safety solutions.
- Eye movement and patterns - are studied to understand human behavior and to assess and diagnose injuries or diseases. You can, for example, perform hearing tests on infants or identify markers of diseases such as Alzheimer or autism at a very early stage. The study of micro-saccades is also central in neurological research. For these purposes, high-frequency eye trackers are indispensable.
- Pupil size and pupil dilation - are reliable markers of impairment, concussion, drug or alcohol influence, or emotions. Commonly used in market research, scientific research and medical assessment.
Eye tracking glossary
- Eye tracker - A device that incorporates illumination, sensors and processing to track eye movements and gaze. The use of near-infrared light allows for accurate, continuous tracking regardless of surrounding light conditions. This technology is often referred to as pupil center corneal reflection eye tracking.
- Dark and bright pupil tracking - Two different illumination setups can be used with pupil center corneal reflection eye tracking: Bright pupil eye tracking causes the pupil to appear brighter than the iris and dark pupil eye tracking causes the pupil to appear darker than the iris. Implementing both dark and bright pupil tracking makes it possible to track greater variations in ambient lighting and ethnicity than using only one of the techniques.
- Remote eye tracker - A system that is placed at a distance from the user, most commonly attached to or integrated with a monitor.
- Mobile eye tracker - A wearable eye tracker often integrated in the frame of a pair of glasses.
- Long-range eye tracker - A system that is placed far from the user, for instance in TV-settings or simulators.
- Eye control / gaze control - Hands-free control of electronic devices, similar to the ways users operate a mouse. The user not only uses their eyes to navigate, but also to select on screen. Eye control is used by people who have speech impairments or physical disabilities, by operators working in heavy industry or using industrial vehicles, or in operating rooms.
- Dwell point - The selection mechanism in systems using eye control where the user clicks by staring at the area of interest for a specified duration (i.e. 500ms, 900ms).
- Calibration - Before an eye tracking session starts, the system calibrates the user’s eyes. By identifying individual eye characteristics, the eye tracker can estimate the gaze point with very high accuracy. Tobii eye trackers can even use a calibration-free setup, where calibration is carried out undetected by the user.
Eye tracking with other technologies
Recently, there has been a trend to use standard camera components such as a webcam or mobile cam to do some of what an eye tracker can do.
- Standard webcam technology is used to determine the more indicative studies of visual attention and direction of interest of website users. Not as precise as standard eye tracking, but provides a general and cost-effective solution to non-scientific studies for online websites and other visuals provided on a computer.
- Mobile camera technology is used in some smartphones for eye presence detection. It is primarily a power-saving feature and, contrary to eye tracking technology with illumination, you are limited by the ambient light in the environment.