Patent ID: 6778475
Filing Date: 2004-08-17
Classification: G11B

Abstract:
An optical detector for detecting at least three light beams separated from a light beam emitted from a first laser source, a second laser source or both, applied to a first or second optical information recording medium and reflected from the optical information recording medium, the optical detector comprising:a first light reception area having four divided light reception planes where a light beam reflected from the first optical information recording medium is applied; a second light reception area having four divided light reception planes where a light beam reflected from the second optical information recording medium is applied; and a third light reception area and a fourth light reception area each having four divided light reception planes where a light beam reflected from the first optical information recording medium is applied, wherein a signal is output which can generate a focus error signal by an astigmatism method by using the first light reception area, second light reception area or both; or a signal is output which can generate a tracking error signal by a push-pull method by independently using the first light reception area, second light reception area or both; or a signal is output which can generate a tracking error signal by a differential phase detection method by using the first light reception area, second light reception area or both; or a signal is output which can generate a focus error signal by the astigmatism method by independently using the third light reception area, fourth light reception area or both; or a signal is output which can generate a tracking error signal by the push-pull method by independently using the third light reception area, fourth light reception area or both, further comprising: a fifth light reception area and a sixth light reception area each having two divided light reception planes where a light beam reflected from the second optical information recording medium is applied, wherein a signal is output which can generate a tracking error signal by the push-pull method by independently using the fifth light reception area, sixth light reception area or both.