Xerox 7750DXF - Phaser Color Laser Printer - ROS and Regicon Technology Overview; Write Black Process

Theory of Operation 2-15
ROS and Regicon Technology Overview
The locations of the ROS and the ROS shutter solenoid are shown in the following
figure.
■ There are four ROS shutters (not shown).
■ The ROS module is field replaceable and contains four laser diodes, one
polygon motor/mirror, and several lenses and mirrors.
■ The ROS module “reflects” the four laser beams so that they strike the
Imaging Units correctly.
■ The ROS module contains four mirrors that can be adjusted for skew using
RegiCon. This adjustment MUST be made when the ROS is replaced.
■ NEVER remove the cover from a ROS module for ANY reason -
contamination will result.
Write Black Process
The Phaser 7750 Printer uses a “black writing” process for exposing the imaging
units.
In the write black process, the image areas are discharged, or exposed. Because the
image area is normally much smaller than the background area, the Write Black
approach extends the life of the laser diode.
In the Write Black process, the negative toner particles are attracted to the more
positive image areas on the photoreceptor and repelled by the higher negatively
charged background areas. A negative developer bias voltage assures good
development of the image areas.