Optical pickup system

An optical pickup system with which emerging light from a source illuminate a recording medium and reflected light from the recording medium is used to read the information of the recording medium comprising:

• a beam splitter reflecting the emerging light from the source toward the recording medium and passing the reflected light from the recording medium;
• an objective lens disposed between said beam splitter and the recording medium;
• a photodetector receiving the reflected light passing through said said beam splitter;
• a hologram device for splitting the emerging light from the source into a plurality of beams, said hologram device being provided in the optical path between the source and said beam splitter, and having a first dividing line generally orthogonal to the tracks on the recording medium and a pair of diffraction gratings that border on said first dividing line, said diffraction gratings having different conditions of diffraction from each other, at least one of said diffraction gratings having a capability for diffraction in the direction generally parallel to the tracks;
• and
• a photodetector having a plurality of light receiving elements, said light-receiving elements having second dividing lines, said second dividing lines being formed over the lines along which the positions of the centers of gravity of beam spots on said photodetector move when said objective lens moves in the tracking mode.