| 摘要 |
<p>PURPOSE:To obtain a coordinate input device which can always and highly precisely execute a coordinate detection operation in spite of the display state of a liquid crystal panel or the use state of a detection pen. CONSTITUTION:The induced voltage (spike-like static noise) of the detection pen 8 due to AC driving in the display period of the liquid crystal panel is set to be DC voltage by smoothing rectification and holding a peak value, and the binarization processing of analog voltage induced by the detection pen 8 is executed in a coordinate detection period based on DC voltage. DC voltage is used as the reference voltage of comparators 23 and 24 executing the binarization processing, for example, or DC voltage is used for the automatic control of the amplification factor of an operand amplifier 9 amplifying the induced voltage of the detection pen 8.</p> |
