Patent ID: 9460748
Filing Date: 2016-10-04
CPC Classification: G11B

Claim Text:
1. An optical disc apparatus capable of reading out information stored in an optical disc medium, said optical disc apparatus comprising: a light emitting device radiating light along an optical axis at an optical-axis position toward said optical disc medium, a radiation strength of the light being greatest at a central vicinity of the optical-axis position; an object lens converging the light radiated by said light emitting device on said optical disc medium; a signal processing section carrying out tracking control, to move a focal point position of said object lens with respect to a track position of said optical disc medium, during an operation to read out information from said optical disc medium; and a control section, during the operation to read out information from said optical disc medium with the focal point position of said object lens aligned with the track position of said optical disc medium and a center position of said object lens aligned with the optical-axis position, detecting an increase in signal quality deterioration in the central vicinity of the optical-axis position and in response, carrying out shifting control, to shift the center position of said object lens with respect to the optical-axis position in a direction normal to the optical-axis until the signal quality deterioration decreases; wherein a movement distance of said object lens due to the shifting control has a large value in comparison with a distance range in which said object lens is moved during the tracking control; and wherein during the operation to read out information from said optical disc medium, a tracking error signal is modified to cancel an effect of the shifting of the center position of said object lens.