Patent ID: 7684305

Claim:
An optical pickup comprising: an optical system in which light from a light source is introduced through an objective lens into an optical recording medium and in which light reflected from said optical recording medium is introduced into a light-receiving unit; and an objective lens driving unit for driving said objective lens based on a light output detected at said light-receiving unit, wherein a diffraction element is provided between said light source and said objective lens, and wherein said diffraction element is provided with at least first and second diffraction areas and said first and second diffraction areas have such grating shapes that ± first-order diffracted lights diffracted are received by said light-receiving unit at the position in which 0-th order light and ± first-order diffracted lights diffracted by guide grooves of said optical recording medium do not overlap with each other, wherein said diffraction element has said first and second diffraction areas in which an area in which ± first-order diffracted lights diffracted by said guide grooves and 0-th order light are offset from each other by a space expressed as: d={λ /( p×NA )}× R, where λ represents the wavelength of light emitted from said light source, NA represents the numerical aperture of said objective lens, R represents the pupil radius, and p represents the track pitch of said optical recording medium.