Dual-camera acquisition for accurate measurement of three-dimensional eye movements

In this paper, we suggest a new approach for accurate measurement of three-dimensional eye movements employing dual-camera acquisition. Two calibrated mini CCD cameras are used to capture two simultaneous images of one eye. Center-of-mass and template-matching algorithms are utilized to obtain two-dimensional coordinates of the center of pupil and iris striation. Instead of asking each subject to fulfill intricate calibration steps, a novel and simpler technique to solve geometric distortion is presented by utilizing direct linear transformation (DLT) algorithm which requires only one preliminary calibration procedure for each camera without changing any camera installation. The DLT algorithm is then used to extract three-dimensional coordinates of the center of the pupil and iris striation from prior two-dimensional coordinates, allowing the three-dimensional angular positions of the eye to be computed. Real-time eyeball visualization based on tracking results is incorporated to help clinicians diagnose eye movements. Experimental results show that our system has high accuracy, as the average errors in the horizontal, vertical, and torsional angular positions were confined to 0.15 degrees, 0.14 degrees, and 0.20 degrees, respectively. Real-time implementation demonstrates that our system can be used in clinical routines to observe either voluntary or involuntary human eye movements. (c) 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.