Eye tracking apparatus and method employing grayscale threshold values

An eye-tracking system for determining a point of regard on a display, said eye-tracking system comprising:

• a display screen providing said display and displaying information corresponding to said point of regard;
• a camera for acquiring a video image of an eye having a pupil, the position of said pupil corresponding to said point of regard, and said video image comprising a pupil image;
• a frame grabber, coupled to said camera, for accepting video data corresponding to said video image from said camera and converting said video data to digital pixel data of a given dynamic range so as to provide said digital pixel data as a grayscale mapping of said video image;
• a computer, coupled between said frame grabber and said display screen, for processing said digital pixel data to substantially determine said point of regard on said display screen wherein said computer includes:
• memory means for providing an expected area value for the area of said pupil within said video image;
• means for determining a grayscale threshold value in accordance with said expected area value and grayscale distribution of said digital pixel data;
• means for segregating said digital pixel data into two separate binary groups as first and second groups using said grayscale threshold value as a discriminator;
• and
• means for substantially determining the position of said pupil in accordance with the segregated data;
• and
• a support, connected to said camera and said display screen, for substantially fixing the physical positions of said camera means and said display screen relative to said eye.

In a vision-tracking system, a tracking method for determining a point of regard, said method comprising the steps of:

• acquiring video data from a camera corresponding to a video image of a vision means, said vision means comprising a pupil, the position of said pupil corresponding to said point of regard, and said video image comprising a pupil image;
• converting said video data to digital pixel data corresponding to said video image using an analog-to-digital interface coupled to said camera so as to provide said digital pixel data of a given dynamic range as a grayscale mapping of said video image;
• providing an expected area value for said pupil;
• determining a grayscale threshold value in accordance with said expected area value and grayscale distribution of said digital pixel data;
• segregating said digital pixel data into first and second groups using said grayscale threshold value as a discriminator;
• determining the position of said pupil in accordance with the segregated data of one of said first group or said second group;
• and
• providing feedback data corresponding to said pupil position from said computer.