Patent ID: RE40371

Claim:
An optical disc recording/reproduction apparatus for recording and/or reproducing data by applying a beam from an optical head unit through a substrate of an optical disc onto/from a recording layer of the optical disc, wherein said substrate of said optical disc has a thickness of 0.3 mm or below, and said optical head unit comprises: an objective lens for converging an incident beam and emitting the beam toward said optical disc; a forward lens for converging the beam introduced through said objective lens and applying the beam to said optical disc; a lens holder in which said objective lens and said forward lens are fixed; and an actuator for driving said objective lens and said forward lens as a unitary block and controlling at least focusing, said objective lens and said forward lens having (1) a total numerical aperture of 0.8 or above, (2) a center position shift tolerance of ±80 μm, (3) an assembly accuracy of a distance between the objective lens and the forward lens of ± 25 μm or less , and (4) inclination angles less than 0.4°.