Scanner Control Pc Board - Toshiba 8070 Service Manual

7.7 Automatic Original-Size Detection Circuit
This circuit detects the original size (standard sizes only) using reflection-type photosensors on the base
frame and lens cover of the optical unit.
7.7.1 Principle of original-size detection
The reflection-type photosensors are located on the base frame and lens cover of the optical unit. Each
photosensor comprises an infrared light emitting diode (LED, light-emitting side) and a phototransistor
(light-receiving side). When an original is placed on the original glass, the light emitted by the LEDs is
reflected by the original and led to the phototransistor. In this way, the presence or absence of an original
is detected by whether reflected light exists or not.
[A4 Series]
Original
7.7.2 Original size detection
(1) If the copier is set in the original size detection mode, the carriage is set at its home position.
(2) Detection is performed in an instant when the platen cover is opened, each sensor receive the
reflecting light and the condition of a matrix shown in (4) are satisfied.
(3) Original size detection is performed when the output signals from each sensor are input to the S-
CPU (IC7) on the scanner control PC board.
6570/5570 SCANNER
Original glass
APS
Fig. 7.7-1
[LT Series]
Original
7 - 14
Original glass
APS
Mar. 1999 © TOSHIBA TEC