| 摘要 |
PURPOSE:To prevent an erroneous operation in which an air flow rate, focusing degree are rapidly lowered even when dirt is increased by lowering the flow rate while a reference value is not updated when a predetermined time is elapsed in a state that an increase in a detected value of a detector does not arrive at sensitivity of a dirt increasing direction for the reference value. CONSTITUTION:When a predetermined time is elapsed in a state that an increase in an output voltage of a detector 6 due to an increase in dirt of the air does not arrive at a sensitivity voltage of ah increasing direction, a reference value is not updated, but an air flow rate due to a blower 5 and fouling degree are lowered by one stage. Thus, when the dirt is further increased so that the increase in the output voltage becomes the sensitivity voltage or more of an increasing direction for the reference value which is not updated, the flow rate due to the blower 5 and the fouling degree are raised by one stage, and the reference value is updated at that time. Thus, an erroneous operation in which the flow rate and the fouling degree are rapidly lowered even when the dirt is increased can be prevented. |
