Ricoh Di-C1 Manual page 124

Automatic Line Position Adjustment
The spaces between the lines are measured by
the front, center, and rear ID sensors. The
controller takes the average of the spaces. Then
it adjusts the following positions and
magnification.
Sub scan line position for CMY
Main scan line position for CMY
Magnification ratio for CMY
Skew for CMY
This process prevents:
Colour registration errors
Skew
Slide 124
Colour registration errors: These are when the four colour toner images
(CMYK) are not written exactly on top of each other)
Sometimes, this type of error is called 'colour shift'. This is not the
correct term. Colour shift is a change in the actual colour.
In this model, the improved mechanisms have reduced colour
registration errors a lot. This means that the default setting for 'black
overprint' is changed to 'off'.
When black overprint is on, if there is black superimposed on a colour
image, the black toner is superimposed on the colour toner image. This
means that a lot of toner is deposited on the paper and scattering can
occur.
When black overprint is off, if there is black superimposed on a colour
image, colour toner is not deposited on the places where black toner will
be. This reduces the quantity of toner. But, if colour registration is not
good, a white gap could appear at the border between the colour toner
area and the black toner area.
Skew: The main scans of the four laser beams across the OPCs must be
parallel. If not, the four colour toner images will be skewed in relation to each
other.
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Di-C1 Training