Aberration correcting apparatus and optical apparatus using the same

An optical pickup apparatus which writes or reads out a signal to/from an optical disc and has a light source for emitting a laser beam, an objective lens for converging the laser beam toward an information recording surface of said optical disc, an irradiating optical system for leading said laser beam to said objective lens, and a detection optical system which includes photodetecting means and leads reflection light from said information recording surface to said photodetecting means through said objective lens,

• wherein said optical pickup apparatus comprises:
• an aberration correcting apparatus which is arranged on an optical axis of an optical path of said irradiating optical system and comprises a pair of light transmitting substrates that face each other, whrein at least one of said light transmitting substrates is held rotatably around said optical axis, the light transmitting substrates have distributions of optical path lengths which mutually complementarily and gradually decrease or increase on a circumference of a same radius in which said optical axis is set to a center, and a distribution of the total optical path length of said pair of light transmitting substrates is changed uniformly within a predetermined range on the concentric circle in which said optical axis is set to the center in accordance with the rotation of said light transmitting substrate, thereby applying a phase difference to the transmitted laser beam;
• and
• aberration correction driving means which includes optical disc thickness detecting means for generating an output corresponding to a thickness change amount of said optical disc, rotates said light transmitting substrate in accordance with said output, and minimizes a spherical aberration that is given to the transmitted laser beam by the transparent substrate of said optical disc.