Image Processing; Overview - Canon iR5055 Series Service Manual

Chapter 5
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.
White plate data correction
area at time of shift shading

5.3.6 Image Processing

5.3.6.1 Overview

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
Analog image processing block
1. Analog Image processing
- CCD drive
- CCD output gain correction, offset correction
- CCD output A/D conversion
5-14
Start key
ON
1st
SCAN
Dust detection control
White plate
Data on light reflected
Dust
by the white plate
(shift shading))
Point of white plate data
measurement at time of fixed shading
CCD
A/D
Analog image
conversion
processing
CCD/AP PCB
2nd
SCAN
Dust detection control
F-5-28
Comparison
Identifies the coordinates
of the start of dust and width
Correction Algorithm
The machine corrects the correction
coefficient of the area of dust using data
for areas on both sides
F-5-29
Digital image processing block
Reader controller
PCB
Shading processing
F-5-30
Data on light reflected
by the white plate
(fixed shading)
Controller
block
0015-4411