HEAD MOUNTED DISPLAY WITH EYETRACKING CAPABILITY

The eye-tracking system is based on the reflection of four light emitting diodes (LED)s at the cornea of user's eve. The LEDs emit infrared light at 900 nanometers and the virtual images formed behind the cornea as well as a near infrared image of the pupil are displayed on a charged couple device (CCD) sensor. The optical system used to display virtual environments is also used to conjugate the virtual images of the LEDs to the CCD sensor. This optimizes the integration of eyetracking system into the head mounted device (HMD). The four LEDs are laid out around the imaging (optical) system and their beam (rays) impinge directly on the eye by reflection on the hot mirror. Then the light reflected by the cornea is reflected again by the hot mirror, goes through the optical system and the cold mirror to be imaged on the sensor. The whole eye is illuminated by near infrared light and the contrast between the dark pupil and the bright iris on the CCD sensor allows knowledge of the location of the center of the entrance pupil. The processing of the location of the cornea images and the center of the entrance pupil leads to determine the sight direction.