Optical head, optical disc drive, computer, optical discplayer and optical disc recorder

Abstract

When performing a read or write operation on an optical disc with information storage layers, this compatible optical head with a two-focus lens can reduce interference caused by an unnecessary diffracted light reflected from a non-target layer and not contributing to reading or writing. The head reads and/or writes information from/on storage media, including first and second media with different protective substrate thicknesses, by irradiating a given one with a laser beam and includes: a diffraction element that diffracts the beam to produce diffracted light of multiple orders; an objective lens for converging nand morder ones of the light on the respective storage layers of the first and second media; a photodetector that receives the beam reflected from the medium and condensed; and a light shielding portion for preventing a portion of the beam reflected from the storage layer of the second medium and including its optical axis from reaching the photodetector. The light shielding portion is arranged so as to reduce loss to be caused by cutting off the portion of the beam to a predetermined value or less.