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...http://www.google.ca/patents/US6016301?utm_source=gb-gplus-sharePatent US6016301 - Optical pickup device and optical disc reproducing apparatus
