Patent ID: 6552984
Filing Date: 2003-04-22
Classification: G11B

Abstract:
A liquid-crystal tilt servo apparatus comprising:a photodetector for detecting a reflection light beam of a laser beam irradiated to an optical recording medium; a liquid crystal device for correcting a tilt error caused by a tilt angle between an optical axis of said laser beam and a direction normal to said optical recording medium at a laser beam irradiating position; a control apparatus for generating a control signal for controlling said liquid crystal device on the basis of the detected signal intensity of said photodetector; and a driving circuit for generating a driving signal to drive said liquid crystal device on the basis of said control signal, wherein said driving circuit has a DC removing filter for removing a DC component in said driving signal and supplying a resultant signal to said liquid crystal device, and wherein said control signal includes a bias signal, a tilt signal and a clock signal, said bias signal representing a bias point at which said liquid crystal device is operated, said tilt signal corresponding to a tilt correction amount of said liquid crystal device, and said driving signal has a voltage amplitude of the sum of a bias voltage and a tilt correction voltage around a predetermined equilibrium voltage, and a frequency of the clock signal, the bias voltage being generated based on said bias signal, the correction voltage corresponding to the tilt correction amount.