Patent ID: 8072870
Filing Date: 2011-12-06
Classification: G11B

Abstract:
1. An optical pickup for reproducing information from a first high-density recording medium having a first substrate thickness, a second high-density recording medium having a second substrate thickness, and a low-density recording medium, the optical pickup comprising: a light source; an optical path changeover unit for changing a laser beam emitted from the light source between a first optical path for the first high-density recording medium and a second optical path for the second high-density recording medium and the low-density recording medium; a first focusing lens system for focusing the laser beam of the first optical path onto an information recording surface of the first high-density recording medium, the first focusing lens system including a first objective lens; a second focusing lens system having a diffraction grating for focusing the laser beam of the second optical path onto an information recording surface of the second high-density recording medium or the low-density recording medium, the second focusing lens system including a second objective lens having a smaller total transmission efficiency for the laser beam emitted from the light source than a total transmission efficiency of the first objective lens, the first focusing lens system and the second focusing lens system being configured such that quantities of lights of laser beams entering the first objective lens and the second objective lens are nearly equal when a same quantity of light of a laser beam is emitted from the light source; and a light quantity adjusting unit for controlling the light source so that a quantity of light of the laser beam emitted from the light source when reproducing the information from the first high-density recording medium is smaller than a quantity of light of the laser beam emitted from the light source when reproducing the information from the second high-density recording medium.