Others; Original Size Detection; Outline Of Detection - Canon NP6251 Service Manual

CHAPTER 3 EXPOSURE SYSTEM
IV. OTHERS
A. Original Size Detection

1. Outline of Detection

The machine is equipped with auto paper selection and auto ratio selection
functions, which necessitate the identification of the size of originals.
As many as four original detection circuits are mounted under the copyboard glass
(Figure 3-401). The outputs of these circuits are checked by the DC controller when the
copyboard cover is closed so as to identify the original as being A3, B4, A4, or B5.
An original detecting circuit consists of an LED which emits light against the original
and a phototransistor which checks the light reflected by the original for output to the DC
controller.
B5R
A4R
B5
A4
A3
Original detection
signal 3
Original detection signal 2
DC controller PCB
3-20
COPYRIGHT © 1997 CANON INC.
Phototransistor
B5
Original detection
circuit 2
Original detection circuit 3
Original detection
signal 0
Figure 3-401
LED
A4 B5R A4R
Original Original
detection detection
circuit 0 circuit 1
Original detection signal 1
Copyboard cover detection signal 1
CANON NP6350/NP6251 REV. 0 JULY 1997 PRINTED IN JAPAN (IMPRIME AU JAPON)
Copyboard cover
open/closed
sensor
PS5
B4 A3