| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup capable of preventing deterioration in prepit detecting performance due to astigmatism accompanying a light beam, and providing high prepit detecting accuracy by a simple structure. SOLUTION: In an optical pickup composed of a semiconductor laser 1, a collimator lens 2, a grating 3, a reshaping prism 4, a 1/4 wavelength plate 5, a reflection prism 6, an objective lens 7, a converging lens 8, a half mirror 9, a multilens 10, a first light receiving element 11 and a second light receiving element 12, the reflected light of a light beam emitted to an optical disk 13 is guided to the half mirror 9. Then, one part of the reflected light is transmitted through the half mirror 9, provided with astigmatism by the multilens 10 and, after its reaching the first light receiving element 11, reproducing of recorded information, tracking error detection and focus error detection are performed. The other part is reflected by the half mirror 9 and, after it reaches the second light receiving element 12, prepit detection is performed. Thus, since the prepit detection is carried out while there are no effects of astigmatism, good prepit detecting performance is assured. |
