Optical pickup apparatus and optical grating assembly therefor

摘要

An optical pickup apparatus for optically reading the data stored in a flat information carrier disc in the form of tiny pits. The pickup apparatus directs a beam of light from a light source to the disc surface. The impinging beam is modulated by the data pits and reflected back to a photodetector. A novel optical grating assembly is disposed between the light source and the information disc, and includes a diffraction grating for the light beam from the source and a holographic grating for directing part of the light beam reflected by the disc to the photodetector. The diffraction and holographic gratings are formed integral with each other into the grating assembly.