| 摘要 |
PROBLEM TO BE SOLVED: To make a tracking servo highly accurate by performing a tracking servo only by the tracking detection output obtained from pits whose signal-to- noise ratios are relatively satisfactory in a high-density disk DVD. SOLUTION: The phase comparision signal obtained by a phase comparating means 6 from values which are outputs of adders 2, 3, in which output signals of cells A, C and B, D being in diagonal positions on a photoelectric detector 1 consisting of quadripartite light receiving elements A, B, C, D are respectively added, is inputted to a holding means 9 via delaying means 8. Besides, after the added signal RF of (A+B+C+D) is shaped into a pulse shape to be inputted to a pit part detecting means 11 and then a 3T pit and a 4T pit are detected by using a master clock (f) to be inputted to the holding means 9. The holding means 9 does not output a tracking detection signal by annuling it when 3T and 4T pits whose signal-to-noise are relatively low are detected and output it when 5T∼14T pits, whose signal-to-noise are satisfactory are detected. |
