Optical pickup with a hologram to limit the aperture of two light beams with different wavelengths

Abstract

An optical pickup device that is able to record/reproduce information signals for first and second optical discs with different recording capacities. The optical pickup device includes an objective lens for converging first and second light beams of different wavelengths on the signal recording layers of first and second optical discs having different substrate thicknesses, a beam splitter having the same transmittance to the first and second light beams and configured for separating the first and second light beams radiated by first and second light sources to fall on the beam splitter via a first objective lens or a second objective lens, and a hologram element arranged between the objective lens and the beam splitter for limiting the aperture of one of the first light beam and the second light beam and for correcting the spherical aberration caused by difference in the disc substrate thickness of the first and second optical discs. This configuration enables various optical elements, such as objective lens or beam splitter, to be used in common for the optical disc of different recording capacities.