The present invention relates to a coupling optical system, an optical
element, and an optical pickup apparatus. A coupling optical system is
provided for use in an optical pickup apparatus and is arranged between a
light source and an objective lens of the optical pickup apparatus. The
coupling optical system includes: a first optical element with a power;
and a second optical element with a positive power. The first optical
element includes an optical surface, an out-effective-aperture section
surrounding the optical surface, and a light-reduction structure arranged
on the out-effective-aperture section. When a non-parallel light flux
emitted from the light source enters into the out-effective-aperture
section, the light-reduction structure reduces a light flux to be emitted
from the second optical element in a direction getting closer to an
optical axis of the second optical element.