US Patent 7764587 Optical pickup apparatus

An optical pickup apparatus includes a plurality of laser light sources, a single objective lens, and a beam shaping mirror. The beam shaping mirror causes each of the laser beams to be incident on a transmission surface, reflects the beam from a reflection surface being unparallel to the transmission surface and causes the beam to emerge from the transmission surface, thereby to convert a light intensity distribution of the beam of each of the wavelengths from an elliptic shape into a circular shape. The beam shaping mirror is made of a liquid crystal, which forms the transmission surface and the reflection surface, and is electrically driven so that a refractive index of the liquid crystal may be held constant irrespective of the wavelengths of the beams each of which enters the beam shaping mirror.