Color Conversion; Main Scan Magnification - Ricoh U-C1 B051 Service Manual

26 July 2002

Color Conversion

Transparency for each color toner is not ideal. Color conversion compensates for
the differences between the ideal and actual characteristics. A matrix converts the
RGB video signals into CMYK video signals while the original is scanned once.
Conversion Matrix
The following color conversion table is an example of the results from the matrix
operation.
• Simple color copying.
• No special modes applied.
• To represent green, the yellow and cyan toners are used in a 1:1 ratio.
Original Color
Toner
Y
M
C
K

Main Scan Magnification

While the machine changes the scanner speed to reduce or enlarge the original in
the sub-scan direction, the ASIC2 chip on the BICU board handles reduction and
enlargement in the main scan direction.
• Scanning and laser writing are done at a fixed pitch (CCD elements cannot be
squeezed or expanded).
• Imaginary points are calculated, corresponding to a physical enlargement or
reduction.
• Image density is then calculated for each of the imaginary points based on the
image data for the nearest two true points.
• The calculated data then becomes the new (reduced or enlarged) image data.
NOTE: The actual calculations for main scan magnification use the polynomial
convolution method. This mathematical process is beyond the scope of a
service manual and will not be covered here.
Color Conversion Table
K R Y
1 1 1
1 1 0
1 0 0
1 0 0
6-29
IMAGE PROCESSING
G C B
1 0 0
0 0 1
1 1 1
0 0 0
M W
0 0
1 0
0 0
0 0