| 摘要 |
A laser printing system including a main body having a photosensitive member and an optical unit for forming an image on the photosensitive member by projecting a laser beam thereon. The optical unit is detachably provided in said main body and has a laser beam source, a laser beam source drive circuit, a laser beam shaping member, and a polygonal mirror for scanning the surface of the photosensitive member with the laser beam. The optical unit gives to the main body an instruction as to the dot density especially assigned thereto. The main body forms the image at the dot density assigned to the optical unit which is selected from a plurality of optical units having different dot densities. Accordingly, the optical units having different dot densities are prepared so as to be selectively used to obtain the desired one of the dot densities.
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