Title :
Deformable model of the human iris for measuring ocular torsion from video images
Author :
Ivins, J.P. ; Porrill, J. ; Frisby, J.P.
Author_Institution :
AI Vision Res. Unit, Sheffield Univ., UK
fDate :
6/1/1998 12:00:00 AM
Abstract :
The authors describe a deformable model of the human iris, which forms part of a system for accurate offline measurement of binocular eye movements, particularly cyclotorsion (torsion), from video image sequences. At least two existing systems measure torsion from infrared video images by pupil tracking followed by cross-correlation of bandpass filtered iris sectors. Unfortunately, pupil expansion and contraction reduce the accuracy of this method. In addition, infrared iris images typically contain very little texture, so correlation can be unreliable. A five-parameter deformable model was therefore developed for taken in visible light. This model can translate (horizontal and vertical eye motion), rotate (torsion) and scale both uniformly and radially (pupil changes). A series of software simulations and hardware tests suggest that torsion measurements obtained with the model are repeatable and accurate to within 0.1°. This performance is illustrated by analysing binocular torsion during fixation on a static target; the results match previously published data from other equipment
Keywords :
biological techniques; biomedical equipment; biomedical measurement; eye; image sequences; motion estimation; video signal processing; bandpass filtered iris sectors; binocular eye movements; cross-correlation; cyclotorsion; deformable model; hardware tests; horizontal eye motion; human iris; ocular torsion measurement; offline measurement; pupil tracking; software simulations; static target; vertical eye motion; video image sequences; visible light;
Journal_Title :
Vision, Image and Signal Processing, IEE Proceedings -
DOI :
10.1049/ip-vis:19981914