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Environmental changes or deterioration of the photosensitive drums and toner can cause variations in
the image density. The image-stabilization control reduces these fluctuations.
Table 1-11 Image-stabilization controls
Image density control (DMAX) This control corrects variations in image density related to deterioration of the
photosensitive drum or the toner. The DC controller adjusts the high-voltage biases
to correct the problem under the following conditions:
The image-stabilization control calibrates each high-voltage bias to stabilize the
fluctuations in image density caused by deterioration of the photosensitive drums or
toner or because of environmental changes. The DC controller determines the
product's environment based on the surrounding temperature and humidity data
from the environment sensor. The DC controller calibrates the biases according to
the detected environment and usage condition of the print cartridge to obtain an
appropriate image. The DC controller determines an environment sensor failure and
notifies the formatter when it detects environmental data from the environment
sensor with out of specified value. The DC controller commands the formatter to
control the image density under the following conditions
●
The temperature of the main thermistor is too low when the product is turned
on.
●
A print cartridge or the ITB is replaced.
●
A specified number of pages have printed.
●
After a specific period of the completion of a previous DMAX
●
The environment changes for a specified condition after a previous DMAX.
Image halftone control (DHALF) The formatter performs this control to calibrate the halftone, based on the halftone-
density measurements, under the following conditions:
●
The formatter sends a command.
●
DMAX is completed.
The DC controller determines an RD sensor failure and notifies the formatter if it
detects data from the RD sensor out of a specified range.
The DC controller determines a RD sensor failure and notifies the formatter if it detects an out-of-
specified-data value from the RD sensor when the product is turned on or when the color misregistration
control starts.
36 Chapter 1 Theory of operation ENWW