Optical storage device, optical device and servo controlling method therefor having first and second focus error signal detectors with different detection ranges and target trajectory generator
The present invention realizes stable focus entry control even in the case where a wideband focus error signal is used with which the focus error signal sensitivity and the level in the vicinity of a focus point vary depending on a light path length. A second focus error signal having a wide range is used, causing an objective lens to approach a disk while maintaining a predetermined rate of change with respect to time, and, during approach, a transition to focus servo is performed by detecting the focus position according to the first focus error signal.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a U.S. continuation application, filed under 35 USC 111(a) and claiming the benefit under 35 USC 120 and 365(c), of PCT application PCT/JP02/08273, filed Aug. 14, 2002. The foregoing application is hereby incorporated herein by reference.
