Optical scanning device having dichroic mirror for separating reading and recording light beams

摘要

An optical scanning device includes an image reading station and a printing station wherein image reading and recording operations are accomplished using an optical system common to both the image reading station and the laser printing station. Recording and reading light beams having different wavelengths are separately emitted from two semiconductor lasers and are combined by a first dichroic mirror. The combined laser beams are deflected by a polygon mirror to scan a predetermined range and then focused by a focusing lens. The laser beams emerging from the focusing lens are applied to a second dichroic mirror where the recording and reading light beams are separated. The recording light beams are directed toward a photosensitive drum to irradiate thereonto. The reading light beam is directed toward an original document placed face down on a glass plate. The scattering light from the original document is detected by photo-detectors to produce an image signal indicative of the image on the original document. To print the original document, the recording light beam is modulated according to the image signal output from the photo-detectors.