| 摘要 |
A coordinate detection apparatus used, for example, to input handwriting to a computer. The apparatus measures the number of times of crossing of the waveform (55) of an ultrasonic wave signal over a threshold value (Vth), detects the crossing timing at, for example, the waveform having the maximal amplitude (W4) after a predetermined number of times counting from a crossing point of a first crossing, measures the time period from the transmission start of the ultrasonic wave by the transmission unit (10) to the detected crossing timing and calculates a length (L) based on the time measured. A coordinate inputting apparatus (100) comprises a pen (102) for transmitting an ultrasonic wave and a coordinate inputting apparatus for inputting coordinate positions of the pen (102) based on a propagation time of the ultrasonic wave transmitted by the pen (102) and received by a plurality of ultrasonic wave receivers (304) and the receiver comprises at least a pair of ultrasonic receivers (304-1, 304-2) for receiving the ultrasonic wave transmitted by the pen (102) and a clip mechanism for pinching a corner of a sheet. Malfunctioning due to contact noise between the pen and sheet can be avoided by delaying the transmission timing of the signal from the pen. |
