Patent ID: 7260033
Filing Date: 2007-08-21
Classification: G11B

Abstract:
1. An optical reproducing apparatus for reproducing information recorded on a medium having periodic concentric grooves, the apparatus comprising: a light source for generating light flux; a lens for focusing said light flux on said medium; an apparatus to form five spots from the light flux on said medium, which is provided between said light source and said lens, wherein said five spots comprise a main spot and two pairs of sub spots, a first pair of said two pairs of sub spots are symmetrically located with respect to said main spot, each at substantially one-half pitch of the periodic grooves of said medium from said main spot in the radial direction of said medium, and a second pair of said sub spots are located substantially one-half pitch of the periodic grooves of said medium from each other in the radial direction of said medium; a photodetector for detecting reflected light fluxes of said five spots from said medium; and a circuit for generating a tracking signal by adding push-pull signals of said sub spots, and then obtaining a difference between a push-pull signal of said main spot and the added push-pull signals of said sub spots.