| 摘要 |
PROBLEM TO BE SOLVED: To make raster edge measurements easy by detecting light emission from a 1st edge of a measured image moving in a 1st direction and light emission from a 2nd edge of a measured image moving in a 2nd direction and combining the motions of the 1st and 2nd edges in the detected state. SOLUTION: Most of a reference current is given to a sensor detector 275 as a current Isw. The current Isw biases the detector 275 in a state that an output state is low, that is, in a selecting state to represent no light reception or a sensor not lighted. When a photo transistor(TR) is irradiated, electric charges produced by light make the photo TR conductive to introduce its current from the reference current. Since a constant current source 250 generates the reference current, the sensor current is deviated from the current Isw of the sensor detector 275. The photo TR deviates a sufficient current from the sensor detector 275 at a prescribed lighting level to turn off the sensor detector 275.
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