US Patent 7319642 Method for adjusting focus bias in optical disk device

Disclosed is a method for adjusting focus bias in an optical disk device. When a focus bias adjustment operation for an optical disk such as a DVD-RAM is performed, a focus bias offset value at which the smallest jitter value of a high frequency signal is detected is set as an optimum focus bias offset value. A physical information data area, which has an embossed form and is recorded in a data area of the disk in a dispersed manner, is detected so that the jitter value of the high frequency signal is measured only for areas other than the detected physical information data area. This achieves a focus bias adjustment operation optimal for an optical disk such as a DVD-RAM, thereby enabling a secure focusing servo operation thereof.