Patent ID: 6120461
Filing Date: 2000-09-19
Classification: A61B,H04N

Abstract:
A device for measuring the ocular gaze point of regard and fixation duration, and the binocular convergence point of a viewer comprising:an optical unit having a clocked raster-scan pulse output, a clocked display field refresh pulse output, and an optical output;said optical unit connected to a headset having a head position and orientation sensor for displaying a visual image into the eyes of said viewer, said headset optically outputting the reflections from the cornea, pupil, and inner structure of said viewer's eyes;an opto-electronic unit;said opto-electronic unit having an input connected to said optical output of said optical unit, an input from said clocked raster scan pulse output of said optical unit, an analog light output of said viewer's eye image, and a digital output for transmitting a signal that electronically represents spatially the optical corneal reflection transmitted from said optical unit;a double-buffered digital memory;a digital processor;said digital processor having an input from said clocked raster-scan pulse output of said optical unit, and input from said clocked display field refresh pulse output of said optical unit, and an input from said digital output of said opto-electronic unit to read said digital output from said opto-electronic unit on each clock-pulse and to write said digital output to said double-buffered digital memory;an image processor;said image processor having an input from said analog light output of said opto-electronic device, an input from said clocked display field refresh pulse output of said optical unit, and a memory mapped digital output comprising the image coordinates and principal axes for the pupil and inner structures of the eye of said viewer following each clocked field refresh pulse; anda digital computer;said digital computer having an input from said output of said head position and orientation sensor, an input from said double-buffered digital memory, an input from said memory mapped digital output of said image processor, an input from said clocked display field refresh pulse output of said optical unit, and an output providing the computed gaze point of regard and fixation duration, and the binocular convergence point of said viewer following each said clocked display field refresh pulse;said optical unit comprises a video display unit, a dielectric polarizer disposed in the path of light emanating from said video display to polarize said light, means for directing and focusing said polarized light onto the eyes of said viewer, a quarter-wave retarder plate, disposed in the path of said polarized light directed to and reflected from said viewers eyes, for rotating said polarized light one-half wavelength, a linear polarizer, disposed in the path of said polarized light reflected from the eyes of said viewer, for reflecting the polarized light in a direction away from the eyes of said viewer, and an optical lens, disposed in the path of said light reflecting off the eyes of said viewer after the light reflecting from said eyes has passed through said wave plate and reflected from said linear polarizing mirror, for optically filtering and focusing the corneal and inner reflections of said eyes in response to the illumination caused by said video display;said video display comprises:a retinal scanning display having a light emitting source activated so as to directly illuminate point-wise portions of the retina of said viewer with a modulated beam forming a diffraction-limited spot;an electronic display driver where said driver excites said light emitting source in a sequential manner according to a specific display refresh order such that said display driver shifts the illuminating beam of said light emitting source to the next position in said order and concurrently modulates the output of said light emitting source for that position;said display refresh order being in a raster scanning pattern forming an array of rows and columns such that a horizontal scanning action moves said beam to draw in turn a row of array pixel elements, and a vertical scanning action moves said beam to the start of the next row to repeat the drawing process; andthe refresh signal from said display driver for said array pixel elements being synchronized with the electrical output of said clocked raster-scan pulse from said video display to said opto-electronic device and said digital processor, and said display field refresh cycle for said display driver being synchronized with the output of said clocked display field refresh pulse from said video display to said image processor and said digital computer.