Patent ID: 7142497

Claim:
An optical pickup which performs at least one of recording, reproduction and deletion of information onto an optical recording medium, said pickup comprising: a light source of a wavelength λ 1 ; a light source of a wavelength λ 2 ; a light source of a wavelength λ 3 , wherein λ 1 <λ 2 <λ 3 ; an object lens which condenses a light from the light source onto the optical recording medium, wherein: said object lens is configured such that the following requirements be satisfied: NA (λ1)≧ NA (λ2)> NA (λ3), where: NA(λ 1 ) denotes an effective numerical aperture for the wavelength λ 1 ; NA(λ 2 ) denotes an effective numerical aperture for the wavelength λ 2 ; and NA(λ 3 ) denotes an effective numerical aperture for the wavelength λ 3 ; and said optical pickup is configured such that the following requirements be satisfied: φ1=φ2>φ3 where: φ 1 denotes a diameter of a beam applied to the object lens in the wavelength of λ 1 ; φ 2 denotes a diameter of a beam applied to the object lens in the wavelength of λ 2 ; and φ 3 denote a diameter of a beam applied to the object lens in the wavelength of λ 3 ; and a phase plate which transforms a light in each of a blue wavelength zone and a red wavelength zone into a light in an approximately circular polarization state, wherein at least two of an aperture switching device, a phase correction device and the phase plate are formed integrally, wherein an electro-optic device is employed to form integrally said phase plate with the phase correction device, and the aperture switching device is formed on a surface of the phase correction device or a surface of the phase plate.