Patent ID: 7843775

Claim:
An optical disc apparatus, comprising: an optical pickup which emits a laser beam through an objective lens to an optical disc, wherein the optical pickup reads the laser beam reflected from the optical disc and then outputs a plurality of signals based on the reflected laser beam along a signal path; a focusing start time detector which generates a gate or digital window signal based on the plurality of signals output by the optical pickup; a focus error signal processor to generate a focus error signal corresponding to a magnitude of the amplitudes of the plurality of signals output by the optical pickup; a focusing controller which uses the focus error signal to begin a focusing operation at a time indicated by the gate or window signal; and an actuator controlled by the focusing controller to adjust the objective lens to focus the laser beam onto a recording layer of the optical disc, wherein the focusing start time detector comprises: a comparator to output a digital signal based on the plurality of signals from the optical pickup, a counter to begin a count at each rising edge of the digital signal output by the comparator, and a digital signal synchronization circuit to output a digital signal having an asserted level while the counter is counting arid having a non-asserted level when the counter is not counting.