Calibration Relationship between Ellipse center to Scene Image * = Scene Position HomographyPupil Center
Solving for homographies 8 degrees of freedom in 3 x 3 matrix H, so at least n = 8 pairs of points are sufficient to determine it Set up a system of linear equations: Ah = 0 where vector of unknowns h = [a,b,c,d,e,f,g,h] T Need at least 8 eqs, but the more the better… Solve for h. solve using least-squares X’ = Hx
calibration method 1. Look at Scene Marker and Press corresponding number on keyboard, 2. Each marker press 2 to 3 times. 3. Randomly select 8 pairs of points to calculate Homography.(Repeatly) 3. Choose the best Homography matrix.
Mapping (x1, y1) (x2, y2)
Experimental Results Frame rate 25/second Accurate Pupil Ellipse Mapping error is low( 13 pixels in 640*480 image)
Demo Link ntext=C25ea4ADOEgsToPDskIo6A6rLXR8eySvaEf82q 6h ntext=C25ea4ADOEgsToPDskIo6A6rLXR8eySvaEf82q 6h
Future Work Hardware Lighter cameras Scene camera position Software Use corneal refletion Try different mapping techniques