Canon iR C3380 series, Руководство по обслуживанию

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Chapter 5
5-16
F-5-31
5.3.7.3 Gain Correction and Offset Correction for the CCD Output
0013-8595
/ / / / iR C3380i / iR C3380 / iR C2880i / iR C2880
The analog video signal from the CCD is subjected to gain correction (in which the rate of amplification is corrected to a specific level) and offset correction (in
which the output voltage in the absence of incident light is also corrected to a specific level).
5.3.7.4 A/D Conversion of the CCD Output
0013-8597
/ / / / iR C3380i / iR C3380 / iR C2880i / iR C2880
The analog signal after correction is then converted into 8-bit digital signals that comply with the individual levels of pixel voltage by the A/D converter.
5.3.7.5 Shading Correction (outline)
0013-8598
/ / / / iR C3380i / iR C3380 / iR C2880i / iR C2880
An original of even density does not necessarily mean uniform CCD output because of the following factors:
(1) variation in the sensitivity of each pixel of the CCD
(2) uneven intensity across the rod lens array
(3) difference in intensity of light between the center and ends of the scanning lamp
(4) deterioration of the scanning lamp
The machine performs shading correction to correct any discrepancy in the output of the CCD. It performs shading correction at power-on and or for each job.
5.3.7.6 Shading Adjustment
0013-8599
/ / / / iR C3380i / iR C3380 / iR C2880i / iR C2880
The machine measures the density of the standard while plate, and uses the result as density data. The data is then subjected to computation to obtain the target
value for use during shading correction.
5.3.7.7 Shading Correction
0013-8600
/ / / / iR C3380i / iR C3380 / iR C2880i / iR C2880
The machine executes shading correction for each scan of the original. It measures the density of the standard white plate, and compares the measurement against
the target value stored in the shading correction circuit; the machine then sets up the difference as the shading correction value, and uses it to correct any variation
among CCD pixel when scanning the originals, thus evening out the image density levels.
F-5-32
CCD15 CCD13
R
G
B
R
G
B
R
G
B
R
G
B
R
G
B
R
G
B
R
G
B
R
G
B
R
G
B
R
G
B
R
G
B
CCD1 CCD2 CCD16 CCD14
R
G
B
R G B R G B R G B G B ......
output
Single analog
shift register
CCD output
Original density
Standard while plate
Characteristics
before correction
Target value
Measurement
Characteristics
after correction
White