Objective lens for optical pickup apparatus, optical pickup apparatus and optical information recording reproducing apparatus

摘要

An objective lens (OBJ1,OBJ2), comprises a first diffractive structure having plural concentric ring-shaped zones. A n1-th order diffracted ray is converged on an information recording surface (RL1) of first optical information recording medium (BD) through first protective substrate (PL1) in such a way that when a wavefront aberration is measured within a first numerical aperture NA1, the RMS value of the wavefront aberration becomes 0.07 lambda 1 or less, and a n2-th order diffracted ray (n2 < n1) is converged on a information recording surface (RL2) of second optical information recording medium (DVD) through second protective substrate (PL2) in such a way that when a wavefront aberration is measured within a second numerical aperture NA2 (NA2 < NA1), the RMS value of the wavefront aberration becomes 0.07 lambda 2 or less.