| 摘要 |
<p>PURPOSE:To improve the accuracy of a finger-touch coordinate detector of capacity/time transducer system by using a frequency negative feedback type similar to a PLL constituting a 90 deg. phase shift circuit of the capacity to be measured to constitute a capacity detecting oscillator with high noise resistance. CONSTITUTION:The capacity proportional to a coordinate value produced by the finger touch to a touch panel 22 is supplied to a capacity terminal of a frequency negative feedback type capacity detecting circuit 36 of a capacity measurement part via analog switch arrays 23-26, an analog switch 27 and an operational amplifier 28. The circuit 36 serves as an oscillation system similar to a PLL and the capacity produced by the finger touch forms a 90 deg. phase shift circuit. Thus the width of an obtained pulse output is changed in response to the coordinate value, and said pulse output width is ANDed with a clock 37 through a gate 38. Then a counter 39 counts the number of pulses to obtain the output corresponding to the coordinate value.</p> |
