Optical pickup apparatus

An optical pickup apparatus for conducting at least recording or reproducing of information on two types of optical information recording media having protective substrates with different thicknesses, comprising:

• a first light source for emitting a first light flux with a wavelength λ1;
• a first objective lens for converging the first light flux from the first light source on an information recording surface of a first optical information recording medium having a protective substrate with a thickness t1 when the optical pickup apparatus reproduces or records information for the first optical information medium;
• and
• a second objective lens for converging the first light flux from the first light source on an information recording surface of a second optical information recording medium having a protective substrate with a thickness t2 (t2≠t1) when the optical pickup apparatus reproduces or records information for the second optical information medium,
• wherein the optical pickup apparatus satisfies:
• 0.8≦(f1×NA1)/(f2×NA2)≦1.2,
• where NA1 is a numerical aperture of the first objective lens when the optical pickup apparatus reproduces information on the first optical information recording medium,
• f1 is a focal length of the first objective lens when the optical pickup apparatus reproduces information on the first optical information recording medium,
• NA2 is a numerical aperture of the second objective lens when the optical pickup apparatus reproduces information on the second optical information recording medium, and
• f2 is a focal length of the second objective lens when the optical pickup apparatus reproduces information on the second optical information recording medium.