Method for video-based nose location tracking and hands-free computer input devices based thereon

DETAILED DESCRIPTION According to the invention, a convex shape such as the shape of the tip of the nose, is a robust object for precise and smooth location tracking with a video camera.
In its method aspect, the invention relates to first defining an X-spot which is generally either a point on the tip of the nose closest to the video camera or slightly off from it.
The thus defined X-spot moves therefore on the tip of the nose as the user changes his head pose.
A video image of the X-spot and its immediate vicinity is stored as an X-luminance pattern.
A reference point is defined in the X-luminance pattern, preferably in its centre location.
In subsequent video frames, a best match for the stored X-luminance pattern is found by comparing luminance patterns on a pixel-by-pixel basis, thereby determining the two-dimensional location of the reference point in each video frame with pixel accuracy.
The reference point location tracking method achieves sub-pixel accuracy by subsequently performing a weighted average operation on the pixel locations in the immediate neighbourhood of the location of the reference point determined with pixel accuracy.
In its apparatus aspect, the invention relates to the implementation of the reference point location tracking method using the corresponding video-based X-spot defining, X-luminance pattern storing, reference point defining, video image registering, video image comparing, and average weighting means.
The two-dimensional location of the reference point is used as input to a computer for display and control related applications.
The reference point location tracking method and apparatus are invariant to rotation of the convex shape or orientation of the tip of the nose, size of the convex shape or distance of the tip of the nose to the video camera, and changes in brightness of the lighting conditions.
It is submitted, that the benefit of the invention lies in the use of video cameras for hands-free operation of a computer input device using the tip of the nose, thereby achieving pixel and sub-pixel accuracies