OPTICAL PICKUP

摘要

An optical sensor (6) detects focus offset. To reduce the focus offset, a substrate (7) is rotated in the XY plane (in the plane perpendicular to the optical axis (J)), and the light beam (11) is moved. A hologram (5) adds an aberration to the light beam (12) to spread the light beam (12) along the movement direction. As a result, the focus offset detected by the optical sensor (6) is reduced. With respect to a light beam (12), the variation of the focus offset is small even if the substrate (7) is rotated. Consequently, a two-wavelength optical pickup exhibiting an excellent focus servo characteristic even for any of two light beams having different wavelengths can be provided.