Method for video-based nose location tracking and hands-free computer input devices based thereon
First Claim
1. A method for tracking the location of a moveable three-dimensional convex shape with a video camera, comprising the steps of:
- step a;
defining the location of an X-spot on said convex shape, said location being selected from the group consisting of a point on said convex shape closest to the video camera, and a point on said convex shape closest to a fixed point in space, said location being moveable on said convex shape as said convex shape changes location and orientation in space;
step b;
storing a digitized video image of said convex shape in a vicinity of said X-spot, the size of said vicinity being defined by the surface area of said convex shape with a substantially constant spherical curvature, said digitized video image having a luminance pattern referred to as a stored X-luminance pattern, said stored X-luminance pattern being stored as a stored matrix;
step c;
defining the location of a reference point selected from the group consisting of the centre of said stored X-luminance pattern, and a location within said stored X-luminance pattern;
step d;
registering a plurality of digitized video images, each one of said plurality of video images containing a video image of said convex shape which is referred to as a registered X-luminance pattern, said registered X-luminance pattern being of the same size as said stored X-luminance pattern, each one of said plurality of video images being registered as a registered matrix;
step e;
comparing said stored matrix and said registered matrix in each one of said plurality of video images on a pixel-by-pixel basis to determine the two-dimensional location of said reference point in each one of said plurality of video images with pixel accuracy; and
step g;
producing the two-dimensional location of said reference point as information useable by a computer in each one of said plurality of video images;
said method being substantially invariant to rotation of said convex shape.
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Abstract
A method for tracking the location of the tip of the nose with a video camera, and a hands-free computer input device based thereon have been described. According to this invention, a convex shape such as the shape of the tip of the nose, is a robust object suitable for precise and smooth location tracking purposes. The disclosed method and apparatus are substantially invariant to changes in head pose, user preferred seating distances and brightness of the lighting conditions. The location of the nose can be tracked with pixel and sub-pixel accuracy.
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Citations
17 Claims
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1. A method for tracking the location of a moveable three-dimensional convex shape with a video camera, comprising the steps of:
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step a;
defining the location of an X-spot on said convex shape, said location being selected from the group consisting of a point on said convex shape closest to the video camera, and a point on said convex shape closest to a fixed point in space, said location being moveable on said convex shape as said convex shape changes location and orientation in space;
step b;
storing a digitized video image of said convex shape in a vicinity of said X-spot, the size of said vicinity being defined by the surface area of said convex shape with a substantially constant spherical curvature, said digitized video image having a luminance pattern referred to as a stored X-luminance pattern, said stored X-luminance pattern being stored as a stored matrix;
step c;
defining the location of a reference point selected from the group consisting of the centre of said stored X-luminance pattern, and a location within said stored X-luminance pattern;
step d;
registering a plurality of digitized video images, each one of said plurality of video images containing a video image of said convex shape which is referred to as a registered X-luminance pattern, said registered X-luminance pattern being of the same size as said stored X-luminance pattern, each one of said plurality of video images being registered as a registered matrix;
step e;
comparing said stored matrix and said registered matrix in each one of said plurality of video images on a pixel-by-pixel basis to determine the two-dimensional location of said reference point in each one of said plurality of video images with pixel accuracy; and
step g;
producing the two-dimensional location of said reference point as information useable by a computer in each one of said plurality of video images;
said method being substantially invariant to rotation of said convex shape. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for tracking the location of a moveable three-dimensional convex shape with a video camera, comprising:
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a. means defining the location of an X-spot on said convex shape, said location being defined from the group consisting of a point on said convex shape closest to the video camera, and a point on said convex shape closest to a fixed reference point in space, said location being moveable on said convex shape as said convex shape changes location and orientation in space;
b. means storing a digitized video image of said convex shape in a vicinity of said X-spot, the size of said vicinity being defined by the surface area of said convex shape with a substantially constant spherical curvature;
c. means defining the location of a reference point selected from the group consisting of the centre of said stored video image, and a location within said stored video image;
d. means registering a plurality of digitized video images, each one of said plurality of video images containing a video image of said convex shape;
e. means comparing said stored video image to each one of said plurality of video images to determine the location of said reference point in each one of said plurality of video images with pixel accuracy; and
g. means producing the location of said reference point in each one of said plurality of video images as information useable by a computer;
said apparatus being substantially invariant to rotation of said convex shape. - View Dependent Claims (13, 14, 15, 16, 17)
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Specification