Patent ID: 7079464

Claim:
A focusing method for use in an optical storage device, for moving a focus from a first data layer to a second data layer of a multiple-layer optical disc, wherein a reference signal linearly determines the position of the focus when the focus moves within a linear region with respect to a corresponding data layer of the multiple-layer optical disc, the focusing method comprising the steps of: if the focus, after a focus compensation, cannot be set on the second data layer and stops at an unknown position outside any linear region with respect to any data layer of the multiple-layer optical disc, providing an auxiliary force to let the focus move in a layer-jump direction and essentially exceed the second data layer, the layer-jump direction being from the first data layer to the second data layer; and after the focus exceeds the second data layer, providing an external force making the focus essentially move, in a direction opposite to the layer-jump direction, toward the second data layer and letting the focus set on the second data layer according to the reference signal.