FOCUSING ERROR DETECTION METHOD, INTEGRATED OPTICAL UNIT, OPTICAL PICKUP DEVICE, AND OPTICAL DISK DEVICE

摘要

PROBLEM TO BE SOLVED: To suppress the change of defocus tolerance due to influence by astigmatism. SOLUTION: In the focusing error detection method, return light from an optical disk that is substantially focused on a recording track T is received and the change in the spot of the return light is detected, thus obtaining a focusing error signal. The change of the spot of the return light in the direction inclined at an inclination angle within the range of 45-135 deg. to a direction in parallel with the recording track T of the optical disk.