Optical pickup having a plurality of photodetectors divided into four regions used to obtain both focus and tracking error signals

Abstract

An optical pickup comprises: first and second semiconductor lasers (); a hologram element () for diffracting light reflected by an optical information recording medium (or); and a plurality of photodetectors (-). The hologram element () has two or more different diffraction regions. The plurality of photodetectors (-) are provided away from the first and second semiconductor lasers () at both sides thereof along an extended line of a line between light emission positions of the first and second semiconductor lasers (). The diffracted light generated from the light beam of the first wavelength () by the hologram element () and the diffracted light generated from the light beam of the second wavelength () by the hologram element () are collected at substantially the same position at one side, and part () of the plurality of photodetectors (-) are provided at the position. Signals obtained from the photodetectors (-) at the both sides are used to obtain a focus error signal and a tracking error signal.