| 摘要 |
PURPOSE:To obtain a tracking error of high quality with a 1-beam type optical pickup device by limiting the output opening diameter of the beam smaller than the reflected light receiving opening diameter. CONSTITUTION:The light emitted from a laser 21 passes through an aperture 22 to limit the output opening diameter of the light beam substantially smaller than the reflected light opening diameter, i.e., the diameter of an objective lens 24. Thus the reflected light of a disk 25 is not deflected on the surface of the lens 24 even if the focus position is close, distant or tilted. As a result, the reflected light of the disk 25 reaches a photodetector 26 via the lens 24 and a beam splitter 23. Then the information quantity needed for generation of the tracking error signal is led to the detector 26 with no shortage nor leakage due to the variation of the focus state. |
