Patent ID: 6069857
Filing Date: 2000-05-30
Classification: G11B

Abstract:
An optical disc system of the type having a focusing mechanism and a tracking mechanism, a lens, and a readable disc, the mechanisms being controlled by a feedback loop, said optical disc system comprising:amplifier means for evaluating a predetermined sector of said disc to determine whether said sector is blank;means for inhibiting said amplifier means from operating at maximum gain while said sector is being evaluated;a servo loop having servo loop transfer function and an error signal, said servo loop suitable for positioning applications, said error signal being sampled at a predetermined sampling frequency;an actuator having a mechanical resonance frequency being less than said predetermined sampling frequency, said actuator being controlled by said servo loop; anda digital lead/lag compensation circuit for stabilizing the servo loop, said compensation circuit having a compensation transfer function including a single lead and a complex lag for producing a notch filter with a notch, said compensation transfer function formulated so that said notch of said notch filter occurs at approximately one half said predetermined sampling frequency thereby reducing amplitude of said mechanical resonance frequency in the servo loop transfer function so that the blank sector check is thereby performed in an environment having the reduced amplitude of said mechanical resonance frequency.