Eye tracking is the growing field of monitoring what people do with their eyes, including what they choose to look at, how their eyes move, how their visual activities behave. Eye tracking devices are the instruments that measure our eye behavior. For example, they measure the directions that our eyes are pointed and predict our gaze points, that is, the locations of the objects that we look at.
Many eye tracking devices are based on video cameras that observe our eyes and produce high-resolution images of our irises, pupils, and scleras. In this process, light emitting diodes illuminate the eyes, and these LEDs produce reflections off the corneal surfaces to provide critical geometric information about the orientation of the eyeball.
An essential part of an eye tracking device lies behind the cameras. This image processing function identifies the eyes within the images, measures the geometric features of the eye elements, and computes the spatial positions and orientations of the eyes.
Once the previous functions have occurred, an eye tracker projects the spatial locations of the eye’s gaze points. If a person is looking at a computer screen, for example, the gaze point may be expressed in x,y screen coordinates.
So, what is the significance of tracking eye movements? Our eyes and vision systems are our brain’s primary tools for gathering current information about our environment. However, our eyes can only look one place at a time. Our brains have evolved a highly sophisticated strategy to point our eyes at what we predict will provide the most useful visual information available to us at the time.
Researchers can use eye tracking devices to observe what our brains choose to look at. While these devices cannot explain why our brain chooses to look at specific things, they can measure and record the sequence of visual pointing decisions the brain ultimately makes. Using data from eye tracking devices, we can make powerful inferences about what is visually important to people’s underlying cognitive processes.