Computer vision system for position monitoring in three dimensions using non-coplanar light sources attached to a monitored object

An apparatus for three-dimensional (3-D) cursor control by an operator comprising:

• a single electronic camera having an image plane, a center of projection, an optical axis, and a camera reference coordinate frame being centered at the center of projection with x and y axes parallel to the image plane and a z-axis parallel to the optical axis, the single electronic camera producing an analog video signal;
• a plurality of at least four light sources configured in any noncoplanar arrangement so long as the light sources are not all located along three orthogonal lines, the light sources having a light source reference coordinate frame and light source coordinates in this object reference coordinate frame, these light sources projecting bright spots onto the image plane of the camera;
• means for processing the analog video signal and determining a list of bright spot locations in the camera reference coordinate frame;
• handle means for allowing an operator to hold and move the plurality of light sources freely in space;
• computing means for:
• repeatedly combining the bright spot locations with the light source coordinates;
• repeatedly producing a rotation matrix and a translation vector in the camera reference coordinate frame;
• repeatedly outputting onto display means in front of the operator's eyes a perspective image of a 3-D virtual cursor located in space at a position and orientation defined by the rotation matrix and the translation vector.

A sensing system for producing at successive time instants digital signals expressing positions and orientations of a rigid three-dimensional (3-D) object in space comprising:

• a single electronic camera having an image plane, a center of projection, an optical axis, and a camera reference coordinate frame being centered at the center of projection with x and y axes parallel to the image plane and a z-axis parallel to the optical axis, the single electronic camera producing an analog video signal;
• at least four noncoplanar light sources rigidly attached to the rigid 3D object in any noncoplanar arrangement so long as the light sources are not all located along three orthogonal lines, the light sources having light source coordinates in an object reference coordinate frame of the rigid 3D object, the light sources projecting bright spots onto the image plane of the camera;
• means for processing the analog video signal and determining a list of bright spot locations in the camera reference coordinate frame;
• computing means which include memory means and output means;
• the memory means storing a precomputed pseudo-inverse matrix depending only on the light source coordinates in the object reference coordinate frame;
• the computing means including pose computing means for:
• computing a translation vector and a rotation matrix of the rigid 3-D object in the camera reference coordinate frame,
• combining the precomputed pseudo-inverse matrix with the list of bright spot locations, by matrix multiplications, vector normalizations and vector cross-products,
• and providing to the output means for each frame of the video signal the three coordinates of the translation vector of the rigid 3-D object and the nine elements of the rotation matrix of the rigid 3-D object in digital form.