Optical disk apparatus

An optical disk apparatus for recording/reproducing information on an optical disk including a single recording layer or a plurality of stacked recording layers, the optical disk apparatus comprising:

• an objective lens that collects laser light to form an optical spot on the optical disk;
• a light amount signal detection section that converts reflected light from a surface and the plurality of recording layers of the optical disk into electrical signals and generates a light amount signal, the light amount signal being a sum of the electrical signals;
• a focus error signal detection section that generates a focus error signal, the focus error signal varying depending on a status of collection of the laser light on a recording layer from among the single recording layer or the plurality of stacked recording layers;
• a focus drive section that drives a focus actuator for moving the objective lens in a direction perpendicular to the optical disk;
• a focus drive generation section that generates a drive signal for moving the objective lens up/down;
• a focus filter that generates a drive signal for causing the objective lens to settle at a height position where the focus error signal falls on a zero-crossing in an S-shaped waveform thereof;
• a drive selector that switches between a setting for sending the drive signal generated by the focus drive generation section to the focus drive section, and a setting for sending the drive signal generated by the focus filter to the focus drive section;
• and
• a lock-in timing detection section that, upon the light amount signal detected by the light amount signal detection section exceeding a predetermined light amount level, determines that the optical spot reaches a vicinity of any of the single recording layer or the plurality of stacked recording layers recording layers, and sends to the drive selector a focus lock-in timing instruction for switching to the setting for sending the drive signal generated by the focus filter to the focus drive section.