Toshiba 4560, Service Manual

Page: 78 / 369

4560/4570 OPTICAL 7 - 16 Nov. 1997 © TOSHIBA
7.6 Automatic Original-Size Detection Circuit
This circuit detects the original size (standard sizes only) using the 3-beam type reflecting photosensor
and 2 – 3 reflecting photosensors (3 for A4 series, 2 for LT series) on the base frame of the optical unit.
7.6.1 Principle of original-size detection
On the base frame of the optical unit, the reflecting
photosensor (3-beam type) and 2 – 3 reflecting
photosensors (3 for A4 series, 2 for LT series). Each
photosensor consists of an infrared light emitting
diode (light-emitting side LED) 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 ab-
sence of an original is detected by whether reflected
light exists or not.
7.6.2 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 original cover is opened and each sensor receives
the reflecting light and the conditions of the matrix shown in (4) are satisfied.
(3) Original size detection is performed when the output signals from each sensor are input to the gate
array (IC21) and the main CPU (IC35). IC21 and IC35 are on the logic PC board.
APS-F
APS-C
APS-0~2
APS-R
Original
Original glass
Original size detection circuit
(Reflecting photosensor)
(Reflecting photosensor)
(Reflecting photosensor (3-beam
type))
(Reflecting photosensor)
This sensor does not exist in the
LT series.
Reflecting photosensor
Reflecting multi-beam
sensor
APS-R
APS-C
APS-F
APS-2
APS-0
APS-1
197
196
195
128
130
129
IN32
IN31
IN30 IC21
PD3
PD1
PD2 IC35
Main CPU
Gate array
GND
V
DD
PWA-LGC