To stabilize an adjacent track servo(ATS) for preventing a problem that recording mark strings overlap with each other caused from displacement of spots accompanying with lens shift and the like while recording on an optical disk recording medium which includes a reference plane having positional guide elements formed thereon and a recording layer formed at a depth position different from the reference plane.
The recording apparatus employs a configuration in which a tracking servo loop is formed as a minor loop for controlling objective lens based on the positional guide elements on the reference plane and a servo control signal is provided to the loop by an ATS control system. The ATS control system is configured to perform phase compensation so as not to generate a peak in a transmission characteristic gain of an ATS loop such as whole integration, a primary LPF or the like. Also, the control band of the minor loop is set in a band which is sufficiently higher than the control band of the ATS loop. With this, a peak is prevented being generated in the loop transmission characteristic gain, which conventionally occurs when only the ATS is used; thus the dispersion of tracking error is prevented resulting in a stabilization of the servo.
Nobuo Suzuki
Hiroto Nakagawa
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