Canon Color Image Reader - L1 Service Manual page 22

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Technology
3) Close DADF (The angle of DADF is from 5 to 25 degree).
3-1) The external light detection operation is performed. Since the area covered by an
original will be blocked from external light, the machine will assume the absence of an
original at points that detect external light. After the DADF sensor 2 detects [Close],
the external light detection operation is started.
In case of the described original size, A3/B4/A4/B5 are excluded from the list of pos-
sible sizes at this point.
25 degrees
original
: external light
3-2) After the external light detection operation, the machine turns ON the LED in the
main scanning direction and the refl ected light is detected by the CMOS line sensor
(5 points). After the fi rst detection, it continues detection by the specifi ed interval (it
completes after 3 sec). The original size sensor 1 starts detection in the sub scanning
direction.
25 degrees
: LED light
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Technology
4) DADF fully closed (the angle of DADF is 5 degree or less).
The machine monitors the changes of output level of each sensor for 3 sec from when the
DADF open sensor 1 detects the [Close] status. The machine determines the original pres-
ence in the point where the output level has no change.
The machine identifi es the original size from the combination of the level change at 5
points (priority on the front original presence).
5 degrees
5) Wait status (wait for start key)
Scanner unit: shading position
LED lamp unit: OFF
Original size sensor: OFF
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