Apparatus for measuring eye gaze and fixation duration, and method therefor

A method for computing, by digital computer using a digital computer program, the gaze point of regard and fixation duration for each eye, and the binocular convergence point for both eyes of a viewer, said method comprising the steps of:

• (a) responding through an interrupt service routine operating in response to a clocked display field refresh pulse output from a display driver;
• (b) reading the position and orientation of headset sensor;
• (c) computing corneal center of said each eye from a three dimensional model of corneal reflections, and further computing cornea surface point locations of the reflections from a source-to-sensor pairing table and embedded memory tables of geometries for a light array and a sensor array;
• (d) smoothing the computed corneal reflections for said each eye by clustering together surface points with similar orientation relative to the respective corneal center;
• (e) computing pupil center for said each eye from the respective said corneal center of said each eye, further computing memory mapped pupil image center and source to sensor pairing table;
• (f) computing optical origin and axis for said each eye from the corresponding corneal and pupil centers;
• (g) computing median axes for cornea of said each eye from a corresponding said optical axis and from data obtained on said smoothed corneal reflection;
• (h) computing viewing origin and axis for said each eye from the corresponding said optical origin and axis and median axes;
• (i) converting viewing origin and axis for said each eye to the viewer's workspace from a headset position and orientation sensor reading;
• (j) classifying viewing status of said each eye as saccadic, fixation, or pursuit from data obtained in steps (a) through (i);
• (k) classifying gaze status of said each eye by grouping local fixations, and computing the gaze point of regard in the viewer's workspace and fixation duration, from the respective viewing origin and axis, and an embedded memory table of workspace geometry;
• and
• (l) computing the binocular convergence point from the viewing origins and axes of both of said eyes for the viewer's workspace.

A method for determining optical constants for developing routines for the gaze point of regard and fixation duration for each eye, and the binocular convergence point for both eyes of a viewer, said method further comprising:

• (a) sequentially displaying a calibration marker at a set of predetermined locations within a visual field of a viewer, and directing the viewer's gaze at said marker locations;
• (b) obtaining a digital output for step a;
• (c) displaying said calibration marker within said field of the viewer using a video display;
• (d) sending a digital instruction to said display driver and displaying said calibration marker at a predetermined location within said visual field of the viewer, said sending step further comprises using a computer program with a display prompting routine;
• (e) fixating said viewer's gaze on a target and releasing said target from hibernation;
• (f) establishing an interrupt service routine in response to a clocked display field refresh pulse output from the display driver;
• (g) establishing a routine for reading position and orientation of a headset sensor when said calibration display is not attached to the headset;
• (h) establishing a routine using said three dimensional model of corneal reflections, from a source-to-sensor pairing table and embedded memory tables of geometries for light array and a sensor array;
• (i) establishing a routine for smoothing the computed corneal reflections for each eye by clustering together surface points with nearly the same orientation relative to the corresponding corneal center;
• (j) establishing a routine for computing the optical origin and axis, and the median axes for cornea of each eye from said corneal center and smoothed corneal reflection data;
• (k) computing a routine once three such calibration markers have been presented at separate locations, said routine computes using the marker location headset position and orientation, a set of constant parameters for each eye relating the viewing origin and orientation to the optical origin and the optical and median axes;
• (l) establishing a routine for computing, once three such calibration markers have been presented at separate locations, using pupil image centroid, interocular corneal center to pupil center distance, a constant parameter for each eye;
• and
• (m) establishing a routine called by said display prompting routine following the display of the calibration marker at all locations, said routine computing best estimate to said optical constants and saving values of said constants in a memory file for reference.