Patent ID: 7924684
Filing Date: 2011-04-12
Classification: G11B

Abstract:
1. An optical pickup comprising: a first emitting unit configured to emit an optical beam of a first wavelength corresponding to a first optical disc; a second emitting unit configured to emit an optical beam of a second wavelength which is longer than said first wavelength, corresponding to a second optical disc which is different from said first optical disc; a third emitting unit configured to emit an optical beam of a third wavelength which is longer than said second wavelength, corresponding to a third optical disc which is different from said first and second optical discs; an object lens configured to condense optical beams emitted from said first through third emitting units onto a signal recording face of an optical disc; and a diffraction unit provided on one face of an optical element or said object lens positioned on the optical path of said optical beams of said first through third wavelengths; wherein said diffraction unit includes wherein said first diffraction region has a first diffraction structure formed in a ring zone shape and having a predetermined depth, which emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens, emits diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and emits diffracted light of an order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens; and wherein said second diffraction region has a second diffraction structure which is different from said first diffraction structure formed in a ring zone shape and having a predetermined depth, which emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens, emits diffracted light of an order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens, and emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant; and wherein said third diffraction region has a third diffraction structure which is different from said first and second diffraction structures formed in a ring zone shape and having a predetermined depth, which emits diffracted light of an order of said optical beam of the first wavelength which passes therethrough and is condensed on the signal recording face of said first optical disc via said object lens, emits diffracted light such that diffracted light of an order other than the order of said optical beam of the second wavelength which passes therethrough and is condensed on the signal recording face of said second optical disc via said object lens is dominant, and emits diffracted light such that diffracted light of an order other than the order of said optical beam of the third wavelength which passes therethrough and is condensed on the signal recording face of said third optical disc via said object lens is dominant.