Ricoh Aficio Color 4006, Service Manual

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24 February, 1999 IMAGE PROCESSING
2-51
Detailed
Descriptions
Main Scan Magnification
The machine changes the scanner speed to reduce or enlarge the original in the
sub-scan direction. However, an LSI on the IPU Board handles reduction and
enlargement in the main scan direction.
Scanning and laser writing are done at a fixed pitch (the CCD elements cannot be
squeezed or expanded). So, to reduce or enlarge an image, imaginary points are
calculated that would correspond to a physical enlargement or reduction of the
image. The correct image density is then calculated for each of the imaginary
points based on the image data for the nearest two true points. The calculated
image 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.
Mirror Image
Each line of video data is transferred to the laser unit in reverse (the end of the line
is written on the OPC first).
A259D527.WMF
û
Main scan Main scan
Start E n d E n d Start
Sub scan
Sub scan
A259D808.WMF