Patent ID: 6339564
Filing Date: 2002-01-15
Classification: G11B

Abstract:
An optical information recording/reproducing apparatus which records information on and/or reproduces information from an optical recording medium based on a reflected light beam from the optical recording medium, comprising:a light splitting part having a plurality of light splitting stages which split the reflected light beam from the optical recording medium into a plurality of light beams; a photodetector unit including n photodetectors which receive m light beams output from a final stage of said light splitting part, where m=6 and n=5, said n photodetectors of said photodetector unit including a plurality of photodetectors which are arranged to receive light beams used to detect a focal error and include two two-part photodetectors respectively having photodetector parts A and B and photodetector parts C and D, at least one photodetector which is arranged to receive a light beam used to detect a tracking error, and a plurality of photodetectors which are arranged to receive light beams used to detect optical information recorded on the optical recording medium; and first calculating means for calculating a focal error signal FES based on outputs of the photodetector parts A, B, C and D by a formula FEC=(A+C)âˆ’(B+D), where the outputs of the photodetector parts A, B, C and D are designated by the same designations as the photodetector parts A, B, C and D.