Patent ID: 8165004
Filing Date: 2012-04-24
Classification: G11B

Abstract:
1. An optical pickup device comprising: a laser source; an irradiating beam condensing optical system which focuses the laser beam from the laser source on one of the recording layers for the multilayered optical information recording medium; and a detecting optical system which detects the reflected light, coming from the recording layer of the multilayered optical information recording medium, wherein the detecting optical system includes: a dividing optical system which divides in parallel the reflected beam coming from the recording layer in such a way that the light flux after division does not travel along the optical axis; a reflected beam condenser lens which focuses the reflected beams divided by the dividing optical system; a reflecting region limited reflection plane which is placed at the position for the minimum spot of the reflected beam coming from one of the recording layers, the reflected beam being one of the reflected beams focused by the reflected beam condenser lens; and an optical detector which detects the beam reflected by the reflecting region limited reflection plane, and wherein the reflecting region limited reflection plane reflects the reflected beam coming from one of the recording layers but not to reflect the reflected beams coming from other recording layers.