Apparatus for measuring eye gaze and fixation duration, and method therefor
First Claim
1. An apparatus for measuring the ocular gaze points of regard and fixation durations and binocular convergence point of a viewer, comprising:
- a) a headset;
b) a position and orientation sensor having an electrical output, wherein said sensor is constructed so as to connect to said headset, said position and orientation sensor comprising means to determine position and orientation of said headset on head of said viewer;
c) an optical unit constructed so as to provide a clocked raster-scan pulse electrical output and further constructed so as to provide a clocked display field refresh pulse electrical output having an optical output, said optical unit is constructed so as to connect to said headset so as to display a visual image onto eyes of said viewer, and further constructed so as to optically output cornea and pupil reflections of the viewer'"'"'s eyes;
d) an opto-electronic device constructed so as to receive an optical input, said optical input connected to said optical output of said optical unit, said opto-electronic device further constructed so as to receive a clocked raster scan pulse electrical input from said optical unit, said opto-electronic device further constructed so as to provide an analog electrical output, said opto-electronic device further constructed so as to provide a digital electrical output for transmitting an electrical signal said opto-electronic device further comprising means for electronically representing spatially optical corneal reflection transmitted from said optical unit;
e) a digital processor constructed so as to receive a clocked raster-scan pulse electrical input from said optical unit, said digital processor further constructed so as to receive an electrical digital input, said electrical digital input connected to the digital output from said opto-electronic device, said processor further constructed to read an output from said opto-electronic device on each clock-pulse and further constructed to write said output from said opto-electronic device to a double-buffered digital memory;
f) an image processor constructed so as to receive an electrical analog input, said electrical analog input connected to said analog output of said opto-electronic device, said image processor further constructed so as to receive a clocked display field refresh pulse input from said optical unit, said image processor further constructed so as to provide a memory mapped digital output of pupil image coordinates and principal axes following each of a clocked field refresh pulse;
g) a digital computer, constructed so as to receive an input connected to the output of said position and orientation sensor, said digital computer comprising means to access an output of said double-buffered digital memory of said digital processor, said digital computer constructed so as to access the memory mapped output of said image processor, said digital computer further constructed so as to receive a clocked display field refresh pulse input, said digital computer further constructed so as to provide a digital output for each of calibration, computed gaze points of regard and fixation durations, and binocular convergence point of the viewer, following said each clocked field refresh pulse, during application.
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Accused Products
Abstract
The invention is an apparatus for measuring eye gaze and fixation duration employing an electronic video display array as sequential sources of eye illumination. The video display of the apparatus may be task related or near infrared light sources used merely to track the user'"'"'s eye. The apparatus of the invention is based on an opto-transistor array, a comparator array and an encoder and latch clocked by the raster-scan pulses of the display driver, which are configured to construct a pairing table of sequential source corneal reflections to sensor activations over the display field refresh cycle. An accurate three dimensional ocular model is computed from opthalmometric techiniques from which the viewing direction and fixation duration are derived. The apparatus is easily extended to the simultaneous tracking of both eyes and is designed to be used with head-mounted video displays. The accuracy of the apparatus is independent of shifts of the helmet on the user'"'"'s head. Additionally, the apparatus is readily incorporated into panel mounted displays and head-free sensor arrays. The apparatus can be used as an eyetracker to control computerized machinery by ocular gaze point of regard and fixation duration.
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Citations
10 Claims
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1. An apparatus for measuring the ocular gaze points of regard and fixation durations and binocular convergence point of a viewer, comprising:
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a) a headset; b) a position and orientation sensor having an electrical output, wherein said sensor is constructed so as to connect to said headset, said position and orientation sensor comprising means to determine position and orientation of said headset on head of said viewer; c) an optical unit constructed so as to provide a clocked raster-scan pulse electrical output and further constructed so as to provide a clocked display field refresh pulse electrical output having an optical output, said optical unit is constructed so as to connect to said headset so as to display a visual image onto eyes of said viewer, and further constructed so as to optically output cornea and pupil reflections of the viewer'"'"'s eyes; d) an opto-electronic device constructed so as to receive an optical input, said optical input connected to said optical output of said optical unit, said opto-electronic device further constructed so as to receive a clocked raster scan pulse electrical input from said optical unit, said opto-electronic device further constructed so as to provide an analog electrical output, said opto-electronic device further constructed so as to provide a digital electrical output for transmitting an electrical signal said opto-electronic device further comprising means for electronically representing spatially optical corneal reflection transmitted from said optical unit; e) a digital processor constructed so as to receive a clocked raster-scan pulse electrical input from said optical unit, said digital processor further constructed so as to receive an electrical digital input, said electrical digital input connected to the digital output from said opto-electronic device, said processor further constructed to read an output from said opto-electronic device on each clock-pulse and further constructed to write said output from said opto-electronic device to a double-buffered digital memory; f) an image processor constructed so as to receive an electrical analog input, said electrical analog input connected to said analog output of said opto-electronic device, said image processor further constructed so as to receive a clocked display field refresh pulse input from said optical unit, said image processor further constructed so as to provide a memory mapped digital output of pupil image coordinates and principal axes following each of a clocked field refresh pulse; g) a digital computer, constructed so as to receive an input connected to the output of said position and orientation sensor, said digital computer comprising means to access an output of said double-buffered digital memory of said digital processor, said digital computer constructed so as to access the memory mapped output of said image processor, said digital computer further constructed so as to receive a clocked display field refresh pulse input, said digital computer further constructed so as to provide a digital output for each of calibration, computed gaze points of regard and fixation durations, and binocular convergence point of the viewer, following said each clocked field refresh pulse, during application. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. 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:
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(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. - View Dependent Claims (9)
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10. 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:
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(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.
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Specification