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Design of eye movement monitoring system for practical environment

This paper describes improved design and implementation of real-time eye movement data acquisition and monitoring system. The main object of the system design is to provide a more practical environment, which allows less restriction on subjects'' head displacement and eliminates tedious optical mirror adjustments. An eye-mark recorder is used as the input device to measure the x-y coordinates of eye movements relative to a subject''s head. In addition, the continuous front view image is taken by a video camera set on the subject''s head. A CRT display is placed in front of the subject. The subject is shown visual objects displayed on the screen and asked to avoid deliberate head motion. Eight infrared LED reference points invisible to the subject are fixed on the screen. These points are used to calibrate the head displacement. First, a set of nonlinear photogrammetric equations including trigonometric functions are developed to relate the reference points to the camera displacements. Second, the equations are linearized for faster calculations. The errors caused by the approximation are evaluated. It is concluded that the linear equations give satisfactory results considering the physical configurations. A set of typical experiment results are shown to demonstrate the system performance.