Laser Exposure; Figure 5-5 Laser Exposure Of The Photoconductive Belt - Tektronix Phaser 550 Service Manual

5
Theory of Operation

Laser exposure

5-8 Phaser 550 Color Printer
As the photoconductive belt rotates, the uniformly charged portion of the belt is
exposed by the modulated laser beam. As the belt passes vertically in front of
the horizontally scanning laser beam, negative charges on the belt surface are
neutralized where exposed by the beam. This forms a latent image on the belt.
The laser beam is turned off for "non-written" portions of the image.
The power of the laser beam is varied from 0.3 mW to 0.5 mW depending on
whether the printer is printing in 1200 dots per inch (dpi) mode or 600 dpi mode.
Following laser exposure, the negative potential of the belt varies from -500 volts
or -550 volts (unexposed) to -10 or -20 volts (fully exposed).

Figure 5-5 Laser exposure of the photoconductive belt

Laser scanner
The laser beam
selectively neutralizes
some of the negative
charges on the belt
surface.
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