Auto Density Adjustment (Ae) - Canon ImageRunner iR8500 Series Service Manual

d. Edge Gain Correction (ADF in use)
In stream reading with the ADF in use, the No. 1 mirror base is fixed in position. To check for changes in the intensity of the scanning lamp, the edge gain
correction plate (gray; mounted at the edge of read position) is read, and a gain that enables the attainment of a specific intensity is computed.
The result is used to correct the data which otherwise would be affected by changes in the intensity of light (Not executed if AE is selected).

6.3.5 Auto Density Adjustment (AE)

/ iR8070
a. Outline
As in the case of a newspaper, some originals have a dark background. Auto density correction is executed to reproduce the information (text, graphics)
of such originals by removing the background.
This adjustment is enabled in density auto mode or when text mode is selected and data is processed by the ABC circuit.
b. ABC Circuit
A colored background is identified as being white by changing the height of the dynamic range according to the chromatic level of the background as
shown in the following figure for the CCD output level (8bit) of digital image signals (A/D converted).
Service Mode:
- COPIER > FUNCTION > CCD > CCD-ADJ (shading auto adjustment)
Execute the mode after replacing the CCD unit, scanning lamp, reader controller PCB, or standard white plate.
- COPIER > FUNCTION > CCD > EGGN-POS (Auto adjustment of the end gain correction position)
Execute the mode after replacing the CCD unit, Mirror plate 1 or 2.
Service Mode:
- COPIER>ADJUST>CCD>PPR (density data of standard white paper)
- COPIER>ADJUST>CCD>PLT (density data of standard white plate)
- COPIER>AJDUST>CCD>GAIN-E/O (gain adjustment input of CCD output)
- COPIER>ADJUST>CCD>OFST-E/O (offset adjustment input of CCD output)
- COPIER>ADJUST>CCD>SH_RATIO (white level ratio data of standard white plate and standard white paper during shading correction)
If a faulty image is generated after executing shading auto adjustment, enter the parameter values indicated on the service label.
CCD output
Target value
Results of
measurement
Reading
glass
White Background Original
Surface of original
FFh (white)
Output level
00h (black)
Characteristics
after correction
Characteristics
before correction
White
Standard white plate
F-6-11
Edge gain correction plate
0 pixel
Copyboard glass
Main scanning
direction
7450 pixels
Standard white plate (for shading)
F-6-12
Colored Original
A
B
A : dynamic range of white-background original.
B : dynamic range of colored-background original.
F-6-13
Original density
FFh (white)
00h (black)
Chapter 6
0008-9650
6-7