| 摘要 |
<p>The objective of an optical pickup is elevated at a constant speed from a position far from the disc to a position near the disc, and a peak-bottom sensor measures the levels (peak/bottom levels) between the peak to the bottom of a focus error signal generated by the movement of the focus. A servo processing microcomputer counts the focus error signals having peak/bottom levels equal to and above a predetermined minimum level among the peak/bottom levels while the focus is moving crossing recording layers of the disc, and the count is judged to be the number of recording layers of the disc. Thus, the recording layers of a storage medium can be correctly counted without being affected by a false pulse generated by factors such as the difference in characteristic between apparatuses, the variation of the reflectance of the storage medium, the variation of the environment temperature, and the waviness of the reproduction output.</p> |
