Canon iR5055, Service Manual

Page: 152 / 646

Chapter 5
5-14
F-5-28
2. Particulars of Control
- White Plate Dust Detection
The machine compares the data on the light reflected by the white plate at time of fixed shading and shift shading to check for dust on the white plate while at the
same time identifying the coordinates and width of the area of dust.
- White Plate Dust Correction
If the machine detects the presence of dust, it corrects the shading correction coefficient of the area of dust by means of a correction coefficient used for both sides
of the area with dust, thus limiting the effects of the dust.
F-5-29
5.3.6 Image Processing
5.3.6.1 Overview
0015-4411
iR5065 / iR 5055 / iR5075 / iR5075N / iR5065N / iR5055N
The PCBs used in the image processing system have the following functions:
CDD/AP PCB: CCD drive, analog image processing, A/D conversion
Reader controller PCB: shading correction
F-5-30
1. Analog Image processing
- CCD drive
- CCD output gain correction, offset correction
- CCD output A/D conversion
Dust detection control
Dust detection control
Start key
ON
1st
SCAN 2nd
SCAN
Correction Algorithm
Data on light reflected
by the white plate
(shift shading))
Data on light reflected
by the white plate
(fixed shading)
Identifies the coordinates
of the start of dust and width
The machine corrects the correction
coefficient of the area of dust using data
for areas on both sides
Point of white plate data
measurement at time of fixed shading
White plate data correction
area at time of shift shading
White plate
Dust
Comparison
CCD/AP PCB
Reader controller
PCB
CCD
A/D
conversion
Shading processing
Analog image
processing
Analog image processing block
Controller
block
Digital image processing block