Patent ID: 7750894
Filing Date: 2010-07-06
Classification: G01S,G06F

Abstract:
1. A coordinates input system comprising: a pointing device including an ultrasonic wave transmitting device; an ultrasonic wave receiving device for receiving an ultrasonic wave transmitted from the ultrasonic wave transmitting device; a coordinates calculating device for calculating coordinates of the pointing device based on a propagation time of the ultrasonic wave transmitted from the ultrasonic wave transmitting device and received by the ultrasonic wave receiving device; a first arithmetic device for calculating a first time, which is a time period from the transmission timing of the ultrasonic wave to a reception recognized timing at which a wave height value of the ultrasonic wave received by the ultrasonic wave receiving device crosses a predetermined threshold for a first predetermined number of times; and a second arithmetic device for calculating a second time as the propagation time of the ultrasonic wave, the second time being relatively greater than the first time and being a time period from the transmission timing of the ultrasonic wave to a reception confirmed timing, which is a timing after the wave height value has crossed the predetermined threshold for a second predetermined number of times, the second predetermined number of times being greater than the first predetermined number of times, and before the wave height value crosses the predetermined threshold again, wherein the second arithmetic device varies the second predetermined number of times according to the first time.