On this page we will explain how dark and bright pupil eye tracking techniques work.
There are two different illumination setups that can be used with Pupil Center Corneal Reflection eye tracking: bright pupil eye tracking, where an illuminator is placed close to the optical axis of the imaging device causing the pupil to appear lit up (this is the same phenomenon that causes red eyes in photos), and dark pupil eye tracking, where an illuminator is placed away from the optical axis causing the pupil to appear darker than the iris.
Different factors can affect the pupil detection during remote eye tracking when using each of these two techniques. For example, when using the bright pupil method factors that affect the size of the pupil, such as age and environmental light, may have an impact on trackability of the eye. Ethnicity is also another factor that affects the bright/dark pupil response: the bright pupil method works very