Main Scan Magnification - Gestetner B147 Service Manual

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 IPU 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.
SM 6-33
IMAGE PROCESSING
B147/B149/B190