Directional eye fixation sensor using birefringence-based foveal detection.
We recently developed and reported an eye fixation monitor that detects the fovea by its radial orientation of birefringent nerve fibers. The instrument used a four-quadrant photodetector and a normalized difference function to check for a best match between the detector quadrants and the arms of the bow-tie pattern of polarization states surrounding the fovea. This function had a maximum during central fixation but could not tell where the subject was looking relative to the center. We propose a linear transformation to obtain horizontal and vertical eye position coordinates from the four photodetector signals, followed by correction based on a priori calibration information. The method was verified on both a computer model and on human eyes. The major advantage of this new eye-tracking method is that it uses true information coming from the fovea, rather than reflections from other structures, to identify the direction of foveal gaze.
Gramatikov
Boris I
BI
Krieger Children's Eye Center at the Wilmer Institute, the Johns Hopkins University School of Medicine, MD 21287-9028, USA. bgramat@jhmi.edu
Zalloum
Othman H Y
OH
Wu
Yi Kai
YK
Hunter
David G
DG
Guyton
David L
DL
D005403:Fixation, Ocular / Q000502:physiology*; D005584:Fovea Centralis / Q000033:anatomy & histology* / Q000502:physiology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods*; D014159:Transducers