Servo apparatus for compensating for warp and deflection deviations on

Abstract

Apparatus for compensating for physical deviations due to warp and surface deflections in optical discs during optical recording and reproducing operations. Focus error signals are developed corresponding to the individual addresses of the physical deviations and the extent of deviation from the in-focus position of the focusing lens by moving a light pickup under control of a microcomputer radially of the disc so that N given radial pitch intervals are defined relative to the record surface of the optical discs and M circumferential address positions of each rotation of the disc. The detector detects the focus error signal values at M.sub.x N.sub.x address locations which are memorized in a memory storing M.times.N values and these are used for developing control signals for moving a focusing lens vertically with an actuator activated by the control signals so that the position of the focusing lens vertically is positioned relative to the record surface so that the focus distance to the record surface is compensated for the physical deviations and an in-focus condition obtained. An arithmetic unit develops light intensity correction values from the memorized data and from this power correction values signals are applied to the source of light beam so that the light beam is applied to the record surface as a spot of proper area dimensions and intensity compensated for the physical deviations.