Canon ImageRunner iR8500 Series, Service Manual, Page: 267 / 1122

Chapter 5
5-15
The machine scans originals faster to support its higher speed of printing. Under specific conditions, it uses a digital method for enlargement/reduction in
combination to enable a higher scanning speed, while keeping the speed of the scanner motor to more or less the same as that of the GP605 (iR600).
Normally, copying with the ADF in use is in stream reading; however, fixed reading is used for reduction between 25 % and 49.9 % and for all ratios in
double-sided mode and in book mode.
The digital method of enlargement/reduction is used for the following:
- for fixed reading, if between 25 % and 49.9 %
- for stream reading, if between 25 % and 84.9 %
5.3.2.3 Changing the Reproduction Ratio in Sub Scanning Direction
0006-9416
iR105i/iR105+ / iR9070
To execute scaling, the moving speed of the mirror 1 mount is changed.
Also, digital scaling is concurrently used under the following conditions:
- Fixed reading: scaling is from 25 to 49.9%
- Stream reading: scaling is from 25 to 84.9%
Memo:
Stream reading is basically executed when a copy is made with the ADF. However,
fixed reading is executed instead if scaling is from 25 to 49.9% or a 2-sided copy is made at any scaling factor. Fixed reading is executed whenever a copy
is made in book mode.
5.3.2.4 Changing the Reproduction Ratio in Main Scanning Direction
0008-7403
/ iR8070
For main scanning direction, the original is read at 100 % (for both copyboard and ADF); the size is changed by processing data in the main controller unit.
[1] To reduce, data units are skipped when writing image data to the line memory.
[2] To enlarge, data units are read multiple times when reading image data from the line memory.
5.3.2.5 Changing the Reproduction Ratio in Sub Scanning Direction
0008-7404
/ iR8070
The reproduction ratio in sub scanning direction is changed by controlling the speed of the scanner and the speed at which originals are moved.
[1] When the copyboard cover is used, the ratio may be between 25 % and 400 % and the speed of the scanner is controlled.
[2] When the ADF is used, the ratio may be between 25 % and 200 % and the speed of moving the originals is controlled.
For a reduction between 25 % and 49 %, however, the main controller unit also functions to change the ratio by processing data.
[1] To enlarge, the speeds at which the mirror base is moved and the originals are moved are reduced (i.e., slower than in Direct).
For instance, to enlarge at 200 %, the originals are read at 1/2 the speed used for Direct.
[2] To reduce to between 50 % and 99 %, the speeds at which the mirror base is moved and the originals are moved are increased (i.e., faster than in Direct).
For instance, to reduce to 50 %, the originals are read twice the speed used in Direct.
F-5-22
[3] To reduce to between 25 % and 49 %, the image data read at 50 % and 98 % is subjected to skipping (1/2) in the main controller unit.
5.3.3 Controlling the Scanning Lamp
5.3.3.1 Outline
0006-9424
iR105i/iR105+ / iR9070
The scanning lamp is controlled for the following:
[1] Temperature by a fluorescent lamp heater
[2] Pre-heat voltage
[3] Initial activation
[4] Intensity by a light intensity sensor
Figure shows the construction of the mechanisms used to control the scanning lamp.
400% 200% 100% 50%
2
1
1/2
1/4
(speed ratio)
(image ratio)