Patent ID: 6700854
Filing Date: 2004-03-02
Classification: G11B

Abstract:
An optical storage apparatus in which by radiating light to a storage medium with information stored therein and receiving the light subjected to a polarized state change by reflection in the storage medium, the information stored in the storage medium is read based on the polarized state change, the optical storage apparatus comprising:a light source for emitting the light to be radiated to said storage medium; a light receiving element for receiving the light reflected by said storage medium; a forward path optical system for guiding the light emitted from said light source to said storage medium via a predetermined forward path; a backward path optical system for guiding the light reflected by said storage medium to the light receiving element via a backward path which traces said forward path in a reverse direction midway after reflection by the storage medium, leaves said forward path midway and reaches said light receiving element, wherein an optical system formed by combining said forward path optical system and said backward path optical system is separately constituted of a fixed optical section fixed to a predetermined base and including said light source and said light receiving element, and a movable optical section moving with respect to said base in accordance with the access position of said storage medium and including only the optical path common to said forward path and said backward path, and a phase plate, disposed on an optical path common to said forward path and said backward path, for compensating for a phase deviation between both P, S polarized components of the light tracing said backward path, said phase plate is disposed on the portion of fixed optical section via which the light is emitted to said movable optical section from the fixed optical section and upon which the light emitted to the fixed optical section from said movable optical section is incident.