An objective lens that satisfies conditions:
-0.02f1M10.02 (1)
-0.02f2M20.02 (2)
-0.29f3M3-0.19. (3)
At least one of lens surfaces of the objective lens includes a diffracting structure
having a first region for converging the third light beam on a data recording layer
of the third optical disc. The diffracting structure within the first region is
configured such that a diffraction order at which diffraction efficiency of the
first light beam is maximized is a sixth order, a diffraction order at which the
diffraction efficiency of the second light beam is maximized is a fourth order,
and a diffraction order at which the diffraction efficiency of the third light
beam is maximized is a third order.