Patent ID: 6717073
Filing Date: 2004-04-06
Classification: G06F

Abstract:
A method of operating an ultrasonic coordinate input system comprising:transmitting a burst of ultrasonic energy from an ultrasonic transmitter in a projection plane; receiving the burst of ultrasonic energy at a receiver an unknown distance away from the ultrasonic transmitter in the projection plane; determining the unknown distance from a propagation time of the ultrasonic energy; receiving at the receiver a higher frequency burst signal from a stylus; receiving at the receiver ultrasonic signals from the stylus; receiving at an additional receiver in the projection plane ultrasonic signals from the stylus; triangulating the position of the stylus relative to the projection plane; and when the ultrasonic signals from the stylus are at a first frequency, triangulating in two dimensions; and when the ultrasonic signals from the stylus are at a second frequency, triangulating in three dimensions.