Tilt servo system for correcting tilt angle of light beam in information read/write apparatus

A tilt servo system for correcting a tilt angle between an objective lens provided in an optical pickup and an information storage medium, said system comprising:

• a phase correction device for adjusting a phase of a light beam emitted from a light source and incident on the information storage medium through the objective lens;
• a moving device for moving the pickup in the radial direction of the information storage medium;
• and
• a control device for calculating a reference position of the pickup on the information storage medium as well as a reference tilt angle in a region through which the pickup has moved from the reference position, in accordance with a separation value which comprises a distance between the information storage medium and the objective lens in focusing, and based on a distance through which the pickup has moved,
• wherein the control device further detects a relative tilt angle of the information storage medium which is a difference between the reference tilt angle and an actual tilt angle in an optical region through which the pickup has moved from the reference position, and drives the phase correction device in accordance with tilt correction quantities corresponding to relative tilt angles,
• wherein the servo system further comprises:
• a first storage device for storing reference correction data which comprises drive data corresponding to said reference tilt angle;
• and
• a second storage device storing drive data corresponding to a plurality of pre-estimated respective tilt angles,
• wherein the control device searches the second storage device for drive data being associated with an angle closest to a relative tilt angle, and drives said phase correction device in accordance with the sum of the drive data and the reference correction data.