Optical pickup apparatus having a quadrant hologram and a quadrant photo detector

摘要

An optical pickup system using a holographic optical element for achieving miniaturization and lightness. This optical pickup system comprises a semiconductor laser for generating a laser beam, an objective lens for focusing the laser beam emitted from the semiconductor laser on an optical disk, a quadrant hologram for diffracting and condensing the laser beam, reflected by the optical disc and transmitted through the objective lens, to a quadrant photo detector, and the quadrant photo detector detecting the laser beam, diffracted and condensed by the quadrant hologram, and reading data recorded on the optical disc. The quadrant hologram and the quadrant photo detector are arranged in such a manner that the optical paths of the first to fourth hologram members of the quadrant hologram pass through the centers of the first, third, second and fourth photo detecting members of the quadrant photo detector, respectively. The laser beam is condensed by the first hologram member after passing through the first photo detecting member, condensed by the second hologram member before passing through the third photo detecting member, condensed by the third hologram member before passing through the second photo detecting member, and condensed by the fourth hologram member after passing through the fourth photo detecting member.