| 摘要 |
PROBLEM TO BE SOLVED: To stabilize a servo characteristics, write-in operation and erase the operation by preventing a phase shift of a tracking error signal. SOLUTION: A photodetector 150 is divided into detection areas 201-208 by division lines 301-304. An overlapped area 200 is provided on first and +1st diffracted light diffracted by a groove on an optical disk. Then, an adder 405 receives outputs of the adders 401-404, and outputs an information regenerative signal RF of total sum of signals s1-s8 answering to light received light quantities from the area 201-208. Further, a differential operation circuit 406 receives the outputs of the adders 401, 404 to output their differential signal TE. When a tilt occurs on the disk 111 the direction orthogonally intersecting with the tangent of the optical disk groove, an offtrack amount for a track center when the tilt occurs is suppressed by taking the signal TE from the signals s1, s2, s5, s8 of the outside of the area 200 of +1st, -1st diffracted light, and by correcting this to zero, the shift in the symmetry of the tracking error signal is suppressed to 2/3 of usual. |
