Patent ID: 6841742

Claim:
A digitizer system for digitizing operative strokes of a drawing implement comprising a body, a back end, and a front end opposite the back end against a board, the system comprising: a movable transmitter device comprising a housing and a central bore, the central bore receiving a portion of the body of the drawing implement with its operative tip extending through the central bore, and an ultrasound transmitter mounted relative to the housing proximal central bore; at least two ultrasound receivers mounted relative to the board for receiving air-borne ultrasound signals; a transducer associated with the board to detect vibrations from the transmitter device conducted through the board; and a processor responsive to outputs from the at least two ultrasound receivers to calculate a current position of the transmitter, the processor being additionally responsive to an output from the transducer to identity contact between the drawing implement and the board, thereby identifying operative strokes of the drawing implement.