Patent ID: 7848209

Claim:
An optical pickup which performs at least one of recording, reproduction and deletion of information onto an optical recording medium, comprising: three light sources which are configured to emit lights of three wavelengths of λ 1 , λ 2 and λ 3 , respectively, where λ 1 <λ 2 <λ 3 ; an object lens which is configured to condense a light coming from each of the three light sources onto the optical recording medium; an aperture switching device which is configured to switch a numerical aperture applied among NA 1 , NA 2 and NA 3 , where NA 1 ≧NA 2 ≧NA 3 ; a phase correction device which is configured to change a phase distribution of a beam which passes therethrough; a wavelength plate, configured to transform light of the wavelength λ 1 from a linear polarization into a circular polarization, or from a circular polarization into a linear polarization, and transform lights of the wavelengths λ 2 and λ 3 from a linear polarization into an ellipse polarization; and at least one of a polarization separation optical system for the wavelength λ 1 , a polarization separation optical system for the wavelength λ 2 , and a polarization separation optical system for the wavelength λ 3 , wherein: said phase correction device is configured to change the phase of an incident beam only within an area in a range approximately between NA 2 and NA 3 , and is configured to provide a phase shift of an integer multiple of 2π to a light of the wavelength of λ 1 ; and said aperture switching device switches a beam diameter according to a wavelength zone using an optical characteristic of any one of reflection, diffraction, and absorption.