Optical pick-up apparatus, optical element, and objective lens having diffracting section

摘要

An optical pickup apparatus for a first optical medium including a first transparent base plate having a thickness of t1 and a second optical medium including a second transparent base plate having a thickness of t2 (t2>t1), comprises a first light source to emit a first light flux having a wavelength of lambda1; a second light source to emit a second light flux having a wavelength of lambda2 (lambda1<LAMBDA2); a converging optical system having an objective lens and a diffracting section and to converge the first light flux or the second light flux onto the first optical medium or the second optical medium; and an optical detector. When the converging optical system converges the second light flux onto the second information recording surface so as to conduct reproducing and/or recording the information of the second optical information recording medium, a spherical aberration has at least one discontinuous portion or at least one substantially discontinuous portion.