4-10
FS-1900
Drum surface potential
The laser beam is continually switched on and off depending on the print data. It is on for a black
(exposed) dot and off for a white (blank) dot. Since the drum surface is evenly charged, whenever
it is illuminated by the laser beam, the electrical resistance of the photoconductor is reduced and the
potential on the photoconductor is also lowered. Resulted on the drum surface is an electrostatic
image which represents the data to print. Note that the area to be printed black has the low potential,
constituting a “positively exposed” image.
Figure 4-1-8 Drum surface potential
Aluminum base
a-Si layer
Laser beam
Charged surface potential
approx. +240 V
Exposed surface potential
approx. 0 to +20 V
Drum
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