The Maryland Revolving-Field Monitor: Theory of the Instrument and Processing Its Data

This report contains a complete description of the method for processing the data from Table Experiments collected by the Maryland Revolving-Field Monitor (RFM). The apparatus used in these experiments included magnetic-field-sensor coils worn on each of the subject's eyes (sensor-coils), two non-coplanar coils attached to the subject's forehead (head-coil device), and a sparker device attached to the subject's head (head-sparker). The raw data recorded from this apparatus included horizontal and vertical eye angles for both eyes, horizontal, vertical, and torsional head angles, and distances from the head sparker to each of four microphones all in real time. All of the above raw data are processed to produce quantities that can be used to analyze the eye-movement behavior of subjects who participated in the Table Experiments. Such quantities include the real-time lines-of-sight of the subject, horizontal and vertical gaze errors relative to a given target, table gaze-positions, and target and ocular vergence. All of these analysis quantities can be determined once the real-time positions of the sighting centers of both eyes are known The body of this work contains a description of the RFM apparatus, descriptions of various calibration activities performed during the Table Experiments, derivations of the equations relating the subject's real-time sighting-center positions to the raw data collected by the RFM, and derivations of the equations that relate the sighting-center positions to the analysis quantities mentioned above. The report concludes with three appendixes that contain Table Experiment calibration details, introductory material regarding vectors and matrices, and a derivation of the basic equation used to determine the elements of the matrix describing an arbitrary rotation.