| 摘要 |
<p>PURPOSE:To detect the position of an input pen with a high precision, by measuring the time difference of zero-crossing points of a signal detected by the input pen to obtain a phase difference. CONSTITUTION:A plane resistor 11 is provided with changeover switches 12a and 12b for scanning, and these switches consist of interlocking switch pairs (S)Xa and (S)Xb. A clock pulse generating circuit 20 which generates a clock pulse frequency signal in inverse proportion to the position differential value of a phase difference and a counter 21 which counts clock pulses generated from the circuit 20 are provided. The time difference of zero-crossing points between a sine wave signal and the signal detected by an input pen 23 is measured to obtain the phase difference, thus detecting the coordinate position of the input pen.</p> |
