1.9. Laser Scan Unit ( Exposure )1.9.1. Operation Theory
The light beam from the laser diode ( light source ) is modulated by the digital signal (nVIDEO) and converted to parallel light waves
by the collimator lens. The beam is then sent to the rotating polygon mirror (polygo n scanner), where it is reflectedthrough the
lens and then focused onto the OPC drum surface. The diameter of the beam is about 80 µm, and the light moves across the
surface of the OPC drum in the scanning directionof right to left. As the drum rotates ( sub-scans ), a static image is formed where
the laser beam touches the drum surface.
The laser beam is also deflected to the timing sensor. This sensor controls the start timing of scanning on the drum, providing a
consistent left margin. The CPU uses the timing sensor to detect abnormal signals.
1.9.2. Laser Beam
The laser beam is pulsed on and off by the digital signal (nVIDEO) to form a latent image of two different voltage potentials on the
drum, as shown below.
Laser Diode Specification
Item Minimum Standard Maximum
Oscillation Wavelength 770 785 800 nm
Output Light Power
(OPC Drum Surface) 0.315 0.350 0.385 mW
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KX-P7100