Patent ID: 7417937

Claim:
An optical pickup apparatus comprising: a first laser diode that emits a first laser beam having a first wave length; a second laser diode that emits a second laser beam having a second wave length that is different from the first wave length; a first parallel flat plate half mirror arranged on an optical axis of the first laser beam for refracting and transmitting the first laser beam therethrough, the first parallel flat plate half mirror being rotated by an angle of 45° around a first axis orthogonal to the optical axis of the first laser beam and having a first refractive index; a second parallel flat plate half mirror arranged on the optical axis of the first laser beam that is transmitted through the first optical element for refracting and transmitting the first laser beam therethrough, and arranged on an optical axis of the second laser beam for refracting the second laser beam to coincide the optical axis of the second laser beam with the optical axis of the first laser beam, the second parallel flat plate half mirror being arranged at a position separated from the first parallel flat plate half mirror by a predetermined distance on the optical axis of the first laser beam, being rotated by an angle of 45° around a second axis orthogonal to the optical axis of the first laser beam and the first axis, and having a second refractive index; and a tilt angle correcting unit that corrects a tilt angle of an optical system including the first and the second parallel flat plate half mirror and cancels a comma aberration generated in a radial direction of an optical disk, wherein: the first and the second parallel flat plate half mirrors are made of a same optical material; and the first parallel flat plate half mirror is thinner than the second parallel flat plate half mirror so as to cancel an astigmatism of the first laser beam.