Toshiba e-STUDIO520 Service Manual page 138

About reflection type photosensor
The reflection type photosensor is comprised of an infrared light emitting diode and a phototransistor. It
uses the pulse modulation to detect an original.
Original
8 µsec
130 µsec
LED Phototransistor
Fig.6-14
The light emitting diode is driven by a pulse having a 130-µsec cycle and an 8-µsec ON time. When the
phototransistor 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.
e-STUDIO520/600/720/850 SCANNING SECTION March 2005 © TOSHIBA TEC
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