| 摘要 |
PROBLEM TO BE SOLVED: To correct the variation of a servo gain even when disk reflectance, the optimum recording laser power, or the like is greatly different, in a recording/reproducing operation using a light source having different wavelengths for an optical recording medium, and to make circuitry therefor simple and common. SOLUTION: Either a photo-detecting signal from a quadripartite photodetector 1 or a photo-detecting signal from a quadripartite photodetector 2 is selected according to a light source selection signal at selectors 3a-3d. Variable gain amplifiers 4a-4d amplify each photo-detecting signal, from which a photo- detecting total sum signal at a total sum signal operational circuit 5, a FE(focus error) signal at a FE signal operational circuit 6, and a TE(tracking error) signal at a TE signal operational circuit 7 are generated. A set gain calculation part 12 calculates and sets the gain of the variable gain amplifiers 4a-4d from the photo-detecting total sum signal. A gain control part 11 automatically controls the gain of the FE signal and the TE signal (servo error signals) on the basis of the photo-detecting total sum signal. |
