Optical disk apparatus compatible with different types of mediums and comprising optical path separating means

An optical disk apparatus comprising:

• two laser beam sources emitting respective laser beams of different wavelength commensurate with respective base thickness of two information recording mediums having different base thickness, said two laser beam sources being arranged close to each other so that the laser beams respectively emitted from said two laser beams sources travel in an identical direction;
• an objective lens for converging the laser beams from said two laser beam sources so as to form respective beam spots on said two information recording mediums;
• polarizing optical path separating means which, provided between said two laser beam sources and said objective lens, separates an optical path for an upstream laser beam from an optical path for a downstream laser beam depending on polarization of laser beams incident on said polarizing optical path separating means;
• a first phase plate which, provided between said two laser beam sources and said polarizing optical path separating means, provides a predetermined phase difference to laser beams incident from said two laser beam sources incident on said polarizing optical path separating means;
• and
• photosensitive means for receiving the downstream laser beam exiting said polarizing optical path separating means.