| 摘要 |
PROBLEM TO BE SOLVED: To enable stable tracking control by removing the influence on a track error signal by an offset component included in the track error signal by using the light of the part all of the zero order diffracted light, first order diffracted light and minus first order diffracted light of reflected light overlap on each other. SOLUTION: The offset component included in the track misalignment signal outputted from the photodetecting regions 25a and 25b of a photodetector 25 is removed by a track misalignment and offset control circuit 64 using the outputs of the photodetecting regions 25a and 25b of the photodetector 25, by which the central value of the track misalignment signal inputted to a track control circuit 65 is approximated to zero. The track error signal is computed in the track misalignment and offset control circuit 64 from the track misalignment quantity and the offset quantity, by which the influence of the offset quantity behaved as if as a track error, in consequence of the lens shift of an objective lens 36, i.e., the offset component included in the track misalignment signal may be compensated. |
