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

An optical disc recording and/or reproducing apparatus comprising::

• an optical pickup device;
• said optical pickup device including
• a first light source for radiating a first light beam;
• a second light source for radiating a second light beam having a wavelength different from that of said first light beam;
• an objective lens for converging the light beam radiated by said first light source or the light beam radiated by said second light source on a signal recording surface of said first optical disc or the second optical disc having different substrate thicknesses via said substrates of the first optical disc or the second optical disc;
• a beam splitter having substantially the same transmittance to the light beam radiated by said first light source and to the light beam radiated by said second light source and adapted for separating the light beam radiated by said first light source or the light beam radiated by said second light source from the first light beam or the second light beam incident via said objective lens;
• a hologram element arranged between said objective lens and said beam splitter for limiting the aperture of said first light beam or the second light beam and for correcting the spherical aberration due to the difference in substrate thickness between the first and second optical discs;
• and
• a photodetector for receiving the first light beam or the second light beam reflected by the signal recording surface of the first optical disc or that of the second optical disc to fall on said objective lens so as to be separated by said beam splitter;
• focussing error signal generating means for generating focussing error signals based on an output signal from said photodetector;
• and
• tracking error signals generating means for generating tracking error signals based on an output signal from said photodetector.