1.4.2 V
L
Pattern Correction
Dirty optics or deterioration of the exposure lamp decreases the intensity of
the light that reaches the drum via the optics cavity. As more copies are
made during the drum’s life, the photoconductive layer gets worn and the
response of the drum to the exposure lamp weakens.
V
L
pattern correction counteracts dirty background caused by the factors
mentioned above.
The V
L
pattern is a light gray sensor pattern on the operator side of the
bottom of the left scale bracket. The ID sensor output at V
SG
detection in
memory is used again as V
LG
(the reflectivity of the bare area of the drum).
When V
L
pattern detection starts, the exposure lamp turns on and the main
motor stays on to rotate the drum. The drum charge roller, all the blocks of
the erase lamp, the pre-transfer lamp, and the quenching lamp turn on.
Then, the appropriate blocks of the erase lamp turn off and on to make a V
L
pattern on the drum surface.
In V
L
detection, V
LP
is compared with V
LG
.
•
V
LG
is the reflectivity of the bare area of the drum, measured by the ID
sensor. It has the same value as V
SG
(see Image Density Control - V
SG
and V
SP
Detection).
•
V
LP
is the output from the ID sensor reflected from the V
L
pattern.
ID Sensor
V
L
Pattern
Exposure lamp voltage
(V)
(V)
Drum
Potential
Initial
Conditions
Deteriorated
Conditions
Detailed
Descriptions
STM 2-21 A156/A160/A162
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