Patent ID: 6822771
Filing Date: 2004-11-23
Classification: G11B

Abstract:
An optical pickup unit for performing at least one of information recording, reproduction, and erasure, the optical pickup unit comprising:a light source of a plurality of semiconductor laser chips of different light-emission wavelengths; a plurality of holograms provided to respective substrates, the holograms being placed between said light source and an optical recording medium, the holograms including at least one non-polarization hologram having a substantially uniform diffraction efficiency irrespective of a direction of polarization of incident light and at least one polarization hologram having a diffraction efficiency varying depending on a direction of polarization of incident light; and a wave plate provided closer to the optical recording medium than the polarization hologram is, wherein: a light beam emitted from a selected one of the semiconductor laser chips passes through said holograms to be focused onto a recording surface of the optical recording medium and reflected therefrom as a returning beam; the returning beam is diffracted by a corresponding one of said holograms so that a diffracted light of the returning beam is received by a light-receiving element; and said wave plate turns a direction of polarization of the returning beam to a different direction from that of the light beam emitted from the selected one of the semiconductor laser chips.