Canon Color imageRUNNER C4580 Service Manual - page 180
Chapter 6
6-13
Specifically, the following takes place:
1) External Light Search (main scanning direction only)
While keeping the scanning lamp off, the machine measures the level of the CCD at specific points in main
scanning direction.
2) Sensor Output Level Detection
The machine turns on the scanning lamp, and measures the sensor output at specific points. It then checks
combinations of these measurement to find the size of the original.
6.3.4.2 Points of Measurement Used for Original Size Identification
For main scanning direction, the machine moves the No. 1 mirror base to the following points in relation to the
location of the original to measure the levels of the CCD. For sub scanning direction, the machine checks the
states of the sensors arranged as follows:
F-6-17
To raise the accuracy of original size identification (as when the original is displaced while the ADF is closed),
the machine makes use of the following 2 types of mechanisms:
1. Presence/Absence of an Original at 2 Points (for each point of measurement)
For each point of measurement in main scanning direction, the machine checks the presence/absence of an
original with reference to the CCD output at 2 points near the point of measurement.
F-6-18
Point of original
detection 3
Point of original
detection 4
Point of original
detection 1
Print of original
detection 2
B5
B6
A5
A4
B5R
A4R
B4
A3
CCD original detection position
Point of original
detection 2
Point of original
detection 1
Point of original
detection 3
LTRR
STMT
LTR
LGL
279.4×431.8mm
(11"×17")
CCD original detection position
Original
sensor 3
AB-Configuration
Inch-configuration
STMTR
Original
sensor 1
Near 4 mm
Near 13 mm
1A:additional point
of detection
Original size
border line
Original size
border line
1B:conventional point
if detection