| 摘要 |
<p>PROBLEM TO BE SOLVED: To perform coordinate calculation with high accuracy by eliminating or reducing an influence of level fluctuation of a sound wave detection signal of a sound wave detecting means to detect sound waves from a sound wave generation source of a coordinate input point instructing mans in a coordinate input device to permit calculation of three-dimensional coordinates in an air sound wave system. SOLUTION: An envelope signal of the sound wave detection signal of a sound wave sensor 3 is fetched by a circuit 61, a peculiar point of its waveform is detected by a circuit 62 and a gate to be validated at the time of detection is generated by a circuit 63. Meanwhile, the initial zero-cross point while the gate signal is valid is detected by a circuit 66 regarding a filter 64 to pass a band of the sound wave detection signal and a sound wave arrival timing signal to be validated at the time of detection is generated. The signal is defined as the sound wave arrival timing signal by phase speed of the sound waves and the three-dimensional coordinates of the coordinate input point are calculated based on the sound wave arrival timing by the sound wave arrival timing signal.</p> |
