| 摘要 |
<p>PURPOSE:To set an optimum load resistance at all times and to detect the existence or nonexistence of a medium with high sensitivity by reading an output voltage of a variable load resistance while varying this resistance, by determining an output characteristic curve, searching a boundary point between a saturated area and an unsaturated area, and determining an optimum operating point for detecting the existence or nonexistence of the medium. CONSTITUTION:An output characteristic calculating means 9 which conducts an operation of searching a boundary point between an unsaturated area and a saturated area of a light-sensing element 4 by making an output of a voltage reading circuit 5 inputted from a control unit 8 and a resistance value of a variable load resistance 3 correspond to each other and an operation of determining an optimum operating point, is provided. Since a load resistance value at the optimum operating point in the case when the existence or nonexistence of a medium is set thereby, the existence or nonexistence of the medium can be detected with optimum sensitivity irrespective of nonuniformity of characteristics, contamination, etc., of the light-sensing element 4 fitted to a device.</p> |
