FOCUS ERROR SIGNAL GENERATION USING CONFOCALLY FILTERED DETECTION

摘要

A focus error signal generator device including first and second optical lenses (136 and 142) disposed in the respective paths of first and second light beams (122 and 124) derived from the return read beam (130) wherein the first and second optical lens (136 and 142) have corresponding points of focus (150), and first and second detectors (140 and 146) disposed in the corresponding paths of the first and second light beams (122 and 124) located after the points of focus (150). First and second pinholes (126 and 128) are disposed in the corresponding paths of the first and second light beams (122 and 124) after the corresponding optical lens (136 and 142) and before the corresponding detector (140 and 146), and an electrical differencing circuit (148) having inputs to the first and second detectors (140 and 146) and an output to an optical head servo system.