Computers that sense eye position on the display
Thomas E HlIlchinsol · 1993
Method. The most wide Iv used method of determining oclar point of regard is based on the bright phenomenon. The method uses infra red illumination of the face. origi nat ing from a light-emitting diode placed at the center of a video camera lens. to produce a high signal- to-nois e im age of the eye's pupiL The resulting video signal is digitized nnd sent to the personal computer for analysis, The analysis determines the pupil cen ter, a long with the center of a glint re flection arising from the front surface reflec tion of the infrared source, The vector distnnce between the glint and pupil center is a measure of point of regard and, when calibrated. deter mines eye position on a computer dis play with high accuracy, A cursor, placed at the point where the comput er thinks the eye is looking. provides interactive control to null slight calcu lation errors, Clearly. this description grossly sim plifies the actual process, The analysis requires several thousand lines of code to implement algori thms that (1) accurately calculate pupil and glint center. (2) calibrate the system t o the geometry of a part icular user's eye, and (3) null the effect of both lateral and display-distanci ng head motions.