| 摘要 |
PURPOSE:To detect the position of a light pen with following optional adjustment of luminance by generating the comparison voltage of a comparator from the output signal from the light pen. CONSTITUTION:At the time of using the light pen 11, the output signal from the light pen 11 is amplified in an amplifier 12 and the outputs are introduced to the non-inversion input end(+) of the comparator 13 and also inputted in the amplifier 15. The output from the amplifier 15 is rectified by a diode 16 and the voltage near to the peak output of the amplifier 15 is held across a capacitor 17, then the voltage whose dividing ratio voltage decided by a resistor 18 and a resistor 9 is supplied to the comparator 13 as the comparison voltage. At the time of not using the light pen 11, a transistor 23 becomes an ON state with an off-switching signal based on the OFF of a switch 11b in the light pen 11, so that charges accumulated in the capacitor 17 are discharged. Thus, a stable detection can be executed.
|
