Ultrasonic coordinate input apparatus

摘要

An ultrasonic coordinate input apparatus identifies using ultrasonic waves whether an input pen contacts a handwriting surface or it is held in the air within a predetermined distance, and can input not only a contact input locus but also an aerial movement locus. A receiver of the ultrasonic coordinate input apparatus is fixed to any of the four corners of the handwriting surface in an appropriate method. Infrared and ultrasonic waves are transmitted respectively from an Infrared transmitting unit and an ultrasonic transmission unit of the input pen being used at predetermined intervals. A distance detection unit of the receiver computes and inputs the contact movement locus or the aerial movement locus of the point of the input pen to the handwriting surface using the ultrasonic waves detected by two ultrasonic sensors only when the infrared from the input pen is received at 90° in the horizontal direction and 10° in the vertical direction.