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About the reflection-type photosensor
The reflection-type photosensor is comprised of an infrared LED (Light Emitting Diode) and a pho-
totransistor. The sensor detects an original with a pulse modulation of LED.
Fig. 6-18
The LED is driven by a pulse having a 130 µsec cycle and an 8 µsec ON time. When the pho-
totransistor receives the same signal as this pulse, it is determined that there is an original. The
pulse modulation is performed inside the reflection-type phototransistor.
130µsec
LED Photoransistor
Original
8µsec
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