Canon imagePRESS C1, Service Manual

Page: 292 / 1265

Chapter 5
5-13
(a) white plate dust detection
(b) white plate dust correction
(2) After a Job
(a) white plate dust detection
(b) white plate dust correction
F-5-29
2. Particulars of Control
(1) White Plate Dust Detection
The machine compares the shading coefficient obtained from shift shading and the shading coefficient obtained from fixed shading to identify the presence/
absence of dust and, if any, coordinates and width of the area.
(2) White Plate Dust Correction
If the machine detects dust as a result of white plate dust detection, it corrects the shading coefficient of the area using the shading coefficient of both sides
so as to decrease the effects of the presence of dust. It executes shading correction using the coefficient it obtains after correction.
If the result of white plate dust detection indicates the presence of dust, the shading coefficient of the area in question will be corrected by the coefficients
of its adjacent areas during shading correction with the aim of reducing the effects of the presence of dust. Thereafter, shading correction will be executed
using the corrected coefficient.
F-5-30
5.3.6 Image Processing
5.3.6.1 Overview
0012-9684
imagePRESS C1 / Color Image Reader-H1 / imagePRESS C1+ (Printer) / imagePRESS C1+
The following shows the major functions of the machine' s image processing system:
- CCD (image sensor)
number of lines: 3 (RGB, 1 line each)
number of pixels: 7350
size of pixel: 9.3 x 9.3 ym
- Shading Correction shading adjustment: in service mode
shading correction: performed for every copy
Dust detection Dust detection
Start key
ON
1st
SCAN 2nd
SCAN
Detection Algorithm
Correction Algorithm
Computation of shading
coefficient
(shift shading to
reference area)
Computation of shading
coefficient
(from fixed shading to
shading correction position)
Detection of coordinates of
start of dust and width
Correction of dust area
coefficient using data of both sides
Fixing shading position
Shading correction position
Reference area
(Shading coefficient
computation area)
White plate
Area
of dust
Comparison