Patent ID: 6507009
Filing Date: 2003-01-14
Classification: G11B

Abstract:
An optical information reproducing apparatus comprising:a semiconductor laser; an optical dividing element that divides an optical beam that is emitted from the semiconductor laser into at least three optical beams; an optical system that converges each of the three optical beams and irradiates optical spots of the three optical beams at a prescribed position on an optical information recording medium; an optical detector which receives three optical beams that are reflected by said optical information recording medium and outputs electric signals representative thereof; a control circuit judging a kind of said optical information recording medium; and a signal processing circuit producing and outputting a focus error signal and a tracking error signal the optical information recording medium by changing selectively a prescribed focus error signal detecting method and tracking error signal detecting method according to the kind of optical information recording method which is judged by said control circuit, and reproducing a data signal recorded in said optical information recording medium; wherein plural semiconductor lasers are provided including a semiconductor laser for reproducing information from a DVD disk and a semiconductor laser for reproducing information from a CD; wherein said control circuit changes selectively said plural semiconductor lasers according to the kind of said optical information recording method which is judged; and wherein said signal processing circuit operates to select an astigmatic detection method using three detected signals representing three optical beams for detecting a focus error signal and differential push-pull detection method for detecting a tracking error signal when said control circuit judges that the kind of said optical information recording medium is a DVD-RAM disk, an astigmatic detection method using one of the detected signals of the three optical beams for detecting a focus error signal and differential phase detection method for detecting a tracking error signal when said control circuit judges that the kind of said optical information recording medium is a DVD-ROM disk, an astigmatic detection method using one of the detected signals of the three optical beams for detecting a focus error signal and a three spot detection method for detecting a tracking error signal when said control circuit judges that the kind of said optical information recording medium is a CD, CD-ROM or CD-R disk.