| 摘要 |
<p>PURPOSE:To simplify the circuit constitution of a tablet as well as the arithmetic software and to improve the tablet accuracy, corresponding to the temperature change of a medium material by omitting a detection element which is used for compensation of the speed change of an elastic wave owing to the temperature change. CONSTITUTION:An ultrasonic wave oscillator 1 set inside an input pen 2 of an ultrasonic table is excited by an exciting circuit 5 for oscillation of ultrasonic waves. When the pen 2 has a contact with an isotropic medium 3, the concentric elastic waves are transmitted to the medium centering on the pen 2. These ultrasonic waves are converted into electric signals by detection elements 4-a-4-c set at four corners. These electric signals undergo the waveform shaping through an amplification/comparison circuit 8. While the time needed for transmission to those elements 4-a-4-c are supplied to a coordinate arithmetic circuit 7 by a transmission time counter 6 in the form of the count numbers of reference clocks. Then the circuit 7 calculates the coordinates of the pen 2 and this coordinate value is displayed on a display device 10 by a coordinate display circuit 9.</p> |
