OPTICAL HEAD, RECORDING AND/OR REPRODUCING APPARATUS, FOCUS SERVO METHOD

摘要

PROBLEM TO BE SOLVED: To speedily focus an objective lens by moving on the basis of a signal generated from a returning light of sub beams the objective lens into a range on a signal record face of a recording medium where a predetermined significant signal output is obtained. SOLUTION: When an objective lens 15 is present at an insensitive region of a focus state detect signal, the objective lens 15 is near a focusing position to a signal record face 2a of an optical disk 2. Leading-in is carried out on the basis of a first focus lead-in signal and a first focus error signal. In other words, the objective lens 15 is moved on the basis of the first focus lead-in signal into a range where a significant signal output of the first focus error signal is obtained. Focus servo to make zero signal outputs of the first focus error signal is executed in the range where the significant signal output of the first focus error signal is obtained, whereby a focal point of the objective lens 15 is met on the signal record face 2a of the optical disk 2.