Optical information-reproducing apparatus using separately located photo detector assemblies

摘要

A light beam emitted from a light source is split into three light beams by diffracting the light beam by using a diffraction grating. The three light beams are reflected by the first side of a plane-parallel plate. The reflected light beams are projected onto an optical disk. The three signal light beams are reflected on the optical disk and returned to the plane-parallel plate in the form of three signal light beams. The plane-parallel plate allows part of the signal light beams to transmit therethrough and to reach a first photo detector. Further, the plane-parallel plate reflects the signal light beams on the second side and allows the reflected light beams to pass therethrough before reaching a second photo detector. The first photo detector receives the central light beam. The second photo detector receives the side light beams.