Focus servo circuit for a magneto-optical disk recording and reproducing apparatus

摘要

An apparatus for optically recording/reproducing data to/from a disc including a focus servo circuit which initially sets an objective lens of an optical head to a predetermined setting. This predetermined setting is such that a laser beam passing through the lens is focused on the disc at a point inside of the disc in the thickness direction. Then, the focus servo circuit fine tunes the objective lens position until the laser beam is focused onto a recording film located inside of the disc.