Patent ID: 8593922
Filing Date: 2013-11-26
Classification: G11B

Abstract:
1. An optical disc apparatus comprising: an optical pickup device configured to detect a value of a return beam reflected by an optical disc and to output the detected value; a controller configured to focus control based on the detected value; and a discriminator configured, when the optical disc has at least a first data layer and a second data layer on which data is recorded or from which data is reproduced, the first data layer being located closer than the second data layer to a beam-incident surface of the optical disc, to obtain a first positive maximum level in a positive side and a first negative maximum level in a negative side of a characteristic curve of a focus error signal obtained from the optical disc, for the first data layer and a second positive maximum level in the positive side and a second negative maximum level in the negative side of the characteristic curve for the second data layer, to obtain a first focus balance value based on the first positive maximum level and the first negative maximum level for the first data layer and a second focus balance value based on the second positive maximum level and the second negative maximum level for the second data layer, and to determine whether a difference between the first and second focus balance values satisfies at least either a first requirement or a second requirement, the first requirement requiring that the difference exceed a predetermined threshold value and the second requirement requiring that the second focus balance value be smaller than a predetermined threshold value, wherein the controller selects a focus balance value depending on a result of the determination concerning the difference between the first and second focus balance values, for focus control.