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RECORDING SECTION
The LASER beam scans one line of the image at a time to form the image
on the photosensitive drum. If the scanning start position in the Horizontal
scanning direction is different for each line of the image during scanning,
then the image will not be able to be drawn correctly on the photosensitive
drum.
For this reason, the nBD signal is required for making the scanning start
position in the Horizontal scanning direction the same for each line of the
image.
The nBD signal is the signal generated by irradiating the LASER beam on
a small mirror (BD mirror) at the end of the photosensitive drum and
detecting it.
4–30
Scanning direction
Normal
Fig. 4-31 Scanning Start Position
BD mirror
LASER unit
Drum
BD detection
circuit
When the start position
has shifted partially
Fixed period
nBD signal
As the scanning mirror rotates at a
fixed speed, this nBD signal is output
at each fixed time period.
Scanning
mirror
Control
nBD signal
section
Fig. 4-32 nBD Signal
When the start position
of the entire image
has shifted
of time
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