Patent ID: 7898919
Filing Date: 2011-03-01
Classification: G11B

Abstract:
1. An optical pickup apparatus for reading out a signal recorded on a signal recording layer of a first and a second optical discs that are different in distance from an incident surface of a laser light to the signal recording layer, comprising: an objective lens configured to be changed in numerical aperture thereof for reading out a signal from the first and the second optical discs; a focus coil configured to displace the objective lens in a direction toward a surface of the first and the second optical discs; a tracking coil configured to displace the objective lens in a radial direction of the first and the second optical discs; a tilt coil configured to correct an angle of an optical axis of the objective lens relative to the surface of the first and the second optical discs; a numerical aperture changing element configured to change numerical aperture of the objective lens so that the laser light is focused on the signal recording layer of the first and the second optical discs; an incident angle changing element configured to change an incident angle of the laser light relative to the objective lens so that the laser light is focused on the signal recording layer of the first and the second optical discs; and a tilt control unit configured to control driving of the tilt coil so as to correct coma aberration, the tilt control unit including