Lexmark MS81x Service Manual page 617

4063
Exposure
The Printhead generates a beam of laser light. Image data received from the controller board assembly modulates this
beam, turning it on and off according to image information that is received from the host computer and software.
Through the use of a series of rotating and stationary mirrors within the Printhead, the beam scans the negative charged
drum surface. Whenever the print controller sends a command to print a black pixel, the laser switches on long enough
to shine onto the drum at a single pixel point. That point is now discharged and slightly less negative than the surrounding
negative charge. The less negative areas are considered positive. This discharge/no discharge process creates an
invisible, electrostatic image on the surface of the drum. This image is called a latent image.
Appendix C: Theory of operation
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