| 摘要 |
PURPOSE:To enable the setting of level at a low cost and handily without requiring any complicated circuitry, by decreasing an emission output when the quantity level of light received in the output of a circuit reaches a non-identification area to shift it to a non-saturation area. CONSTITUTION:An apparatus is made up of a light emitting element 2 provided through a medium 1, a light receiving element 3, a variable resistor 4 and a amplifier 5 both for adjusting level by amplifying a current value of the light receiving element 3, a level switching circuit 6 for switching an emission output of the light emitting element 2. When the quantity of light received in an area B without a medium 1 reaches a saturated state to narrow the range D of an output value, the quantity of light emitted by the light emitting element 2is damped with the level switching circuit 6 to shift the quantity of light received without a medium to a non-saturation area nd the total quantity E of light receivied without a medium on a non-saturation area shall be a reference value as maximum output value. |
