WAVELENGTH SELECTIVE ELEMENT FOR LIMITING OPENING, WAVELENGTH SELECTIVE BEAM SPLITTER, AND OPTICAL PICKUP APPARATUS EQUIPPED THEREWITH

摘要

An optical pickup apparatus includes a wavelength selecting numeral aperture limiting element and a wavelength selecting beam splitter to record data on and reproduce data from three different optical discs, such as CD, DVD, and HD-DVD, each having different thickness of a protective layer and information recording density. The wavelength selecting numeral aperture limiting element of the optical pickup apparatus includes a first filter and a second filter disposed on respective sides of a transparent element to change a numeral aperture of an objective lens into three different numeral apertures in response to three different beams. The first filter disposed on an optical path to receive first, second, and third beams includes a first region transmitting the first laser beam and a second region disposed within the first region to transmit the first, second, and third laser beams. The second filter disposed on the optical path includes a third region transmitting the first and second laser beams and a fourth region disposed within the third region to transmit the first, second, and third laser beams.