Method and apparatus for generating focus error signals in a multi-beam optical disk drive

摘要

A focus detection system for use in a multi-beam optical pickup assembly is provided that uses an optical element, either a holographic element or diffractive element, to split beams reflected off of a data-bearing surface of an optical disk into a plurality of data beams and a plurality of focus beams. The optical element also introduces astigmatism into the focus beams. The focus beams are projected onto focus detectors configured to account for overlap between adjacent focus beams to produce an accurate focus error signal.