| 摘要 |
<p>PURPOSE:To prevent a malfunction which is caused by an insect by generating an infrared beam about 3mm above a tube surface, performing position detection as to one axis at least twice, and regarding the same coordinate values as plane coordinates when the same coordinate values are detected. CONSTITUTION:The position detection of one axis, e.g. an X or Y beam is performed at least twice and when 1st and 2nd values are equal, they are regarded as the detected value of the beam position of another axis and regarded as the determined correct plane coordinates, since a fly, etc., never interrupts the same beam. A light emitting diode 11 and a phototransistor 12 are so arranged as to generate the infrared beam about 3mm above the tube surface so that the beam between both is not interrupted by an insect such as the fly on the tube surface of a CRT 10. Consequently, the problem of parallax is not caused and the malfunction which is caused by the fly, etc., is prevented.</p> |
