| 摘要 |
<p>PURPOSE:To eliminate the deterioration of precision for detecting a coordinate due to noise by making the phase of higher harmonics of a detecting radio wave the same even if the higher harmonics of an AC signal lighting an illuminator overlaps with the radio wave at the time of detecting the radio wave for detecting the state of a position indicator. CONSTITUTION:The output signal J of LPR 309 for detecting the state of the position indicator is inputted to a device as a signal without noise when an invertor circuit 600 does not operate. When the invertor circuit 600 operates, the signal in which the higher harmonics of a clock signal CK 2 in the invertor circuit 600 is overlapped is inputted. In such a case, characters written by a pen from above a light crystal display panel which is overlapped on a sense part 10 are brightly displayed on the liquid crystal display panel by receiving the operation of a back light 60 and a light-introducing board installed under the sense part 10 with the handwriting of the graphic being the same handwriting since the clock signal CK 1 and the signal CK2 in the circuit detecting the state of the position indicator are always synchronized.</p> |
