Patent ID: 8144562
Filing Date: 2012-03-27
Classification: G11B

Abstract:
1. An optical disc apparatus for reading information recorded on an optical disc medium including a plurality of signal surfaces, comprising: an optical pickup including an objective lens, for outputting an output signal according to reflected light from the optical disc medium; a drive unit for relatively moving the objective lens included in the optical pickup with respect to a surface of the optical disc medium in a direction of changing a distance to the surface of the optical disc medium; a comparison signal output unit for outputting a comparison signal indicating whether or not a level of the output signal output from the optical pickup is equal to or higher than a given threshold value; maximum signal level measurement means for causing the drive unit to move the objective lens within a predetermined range to measure a maximum level of the output signal output from the optical pickup within the predetermined range; threshold value setting means for setting a value determined according to the measured maximum level as a threshold value used by the comparison signal output unit; and signal surface reflection measurement means for measuring a level of a reflected signal corresponding to reflected light from each of the plurality of signal surfaces based on a maximum value of the output signal in each of a plurality of time periods in which the comparison signal indicates that the level of the output signal is equal to or higher than the set threshold value, while moving the objective lens again by the drive unit within the predetermined range after the measurement of the maximum level of the output signal by the maximum signal level measurement means.