| 摘要 |
PURPOSE:To obtain an optical pickup device capable of detecting focus with small-size and compactness by arranging a lambda/4 plate in front of a track detection photodetector and a flat concaved lens where a half of the flat side is subject to reflection increasing processing and adding a focus detection photodetector in front of the lens via a polarized beam splitter. CONSTITUTION:The P polarized light from a semiconductor laser 11 passes through a polarized beam splitter (PBS), goes to circularly polarized light via lambda/4 plate 14 to form a spot on an optical information recording medium 12 via a coupling lens 15 and an objective lens 16. The reflected light goes reversely and is made incident in the PBS13 as an S polarized light. The light is reflected in the reflecting film 13a and made incident in the track detection photodetector 19 through the lambda/4 plate 17 and other parts than the reflected part 18a of the flat concaved lens 18. On the other hand, the light made incident in the reflecting part 18a of the lens 18 is reflected and passes again through the lambda/4 plate 17 to be a polarized light and made incident in the focus detection photodetector 20 through the PBS13. |
