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

An optical pickup apparatus having a quadrant hologram, comprising:

• a semiconductor laser for generating a laser beam;
• an objective lens for focusing the laser beam, generated from said semiconductor laser, on an optical disk;
• and
• a hologram for condensing the laser beam, reflected by said optical disk and transmitted through said objective lens, to a photo detector, wherein said hologram is a quadrant hologram having first to fourth hologram members,
• said photo detector detecting the laser beam, condensed thereto by said hologram, and reading data recorded on said optical disk, wherein said photo detector is a quadrant photo detector having first to fourth photo detecting members,
• said quadrant hologram and said quadrant photo detector being arranged such that an optical path of said first hologram member passed through a center of said first photo detecting member, an optical path of said second hologram member passes through a center of said third photo detecting member, an optical path of said third hologram member passes through a center of said second photo detecting member, and an optical path of said fourth hologram passes through a center of said fourth photo detecting member, so that a tracking error of said optical pickup apparatus is compensated by a difference between a summed signal of said first and second photo detecting members and a summed signal of said third and fourth photo detecting members, and a summed signal of said first to fourth photo detecting members is used for reading the data recorded on said optical disc.