| 摘要 |
PURPOSE:To prevent the erroneous detection of a tracking slippage and the focus slippage in track jumping by comparing the focus slippage of a reading beam by comparing each light receiving amt. by two light receiving elements. CONSTITUTION:The optical beam emitted from a laser diode 1 is converged by an objective lens 4 via a splitter 3, projected on the signal face of a disk 2 and its reflection light is made incident on an optical part 5 via the lens 4 and splitter 3. The respective reflection beam from the surface 5a and inner face 5b of the part 5 is made incident on an optical detector 6. The difference in the light receiving amt. of the light receiving element 7 of the detector 6 and that of a light receiving element 8 is varied according to the state of the reading beam for the disk 2. The focusing control is then performed by driving the lens 4 by the difference obtd. by subtracting the signal level of the element 7 from that of the element 8. |
