IMAGE PROCESSING30 March, 1999
Magnification Processing
Main Scan Magnification
A269D088.WMF
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.
400 dpi to 600 dpi Conversion
The copier converts image data that is scanned at 400 dpi to 600 dpi by performing
the same processing that is explained above in ?Main Scan Magnification? by
applying 150% magnification processing on the image data for both main and sub
scans.
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