Limbach & Limbach, LLP
Optical pickup device and optical disc reproducing apparatus
 An optical pickup device which assures interchangeability between plural types of optical discs with different layered structures, such as CD, CD-R or DVD, which is reduced in size and which realizes reproduction of high reliability information signals. The pickup device includes a light source for radiating laser light beams of different wavelengths in association with the plural types of the optical discs with different layered structures, an objective lens for converging the laser light beam radiated from the light source on the signal recording layer of the optical disc, an objective lens switching mechanism for switching and moving the objective lens to the recording/reproducing position, light splitting means for splitting the incident laser light beam from the light source from the reflected laser light beam reflected from the optical disc, plural photodetectors for receiving the reflected laser light split by the light splitting means, and an optical system correction means for correcting the objective lens. 
Sony Corporation
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Hiroyuki Junichi Takeharu Hidekazu Shoji
Ito Suzuki Takasawa Seto Sato