Canon Vizcam 1000, Service Manual

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3. OPERATION AND TIMING
COPYRIGHT © 2001 CANON INC. CANON CLC1000/1000S/3100 REV.2 MAY 2001 PRINTED IN JAPAN (IMPRIME AU JAPON)
3-52
The degree of light transmitted by each of the
filters of the CCD (B, G, R) and the density (Y, M,
C) of an original are in a complementary
relationship; level conversion is executed as in
Figure 3-329 to generate Y, M, and C signals.
k. Removing Moire
When originals consisting of dots (printed
material, for example) are read, moire can occur in
the output. This block removes moire from image
inputs.
Images consist of patterns of various
densities. Areas where dark and light patterns
repeat in high density are called high frequency
components; on the other hand, areas where dark
and light patterns repeat in low density are called
low frequency components.
Within image data, the frequency components
of dotted areas fall between 5.0 and 7.0 lines/mm;
the output gain is lowered for such components,
thereby evening out the dotted components and
preventing moire (Figure 3-330).
This processing is executed for the dotted
areas extracted by the previously discussed text
extraction block if the original type is set as “text/
printed photo” or “printed photo.”
Figure 3-329
Figure 3-330
255
(B, G, R)
0
Thick
Thin
0 255
(Y, M, C)
BGR
→
YMC
(line/mm)
2.0 1.0
The sight characteristics of
human beings are high in this
areas.
The area contains dots.
3.0
4.0 5.0 6.0
7.0
1