| 摘要 |
PURPOSE:To provide a wobble information reader for an optical disk capable of improving the error rate of the wobble information. CONSTITUTION:A wobble information reader for an optical disk takes out wobble information by detecting a reflected diffraction light beam 14 from the wobble guide groove 15 of an optical disk 5 by means of a photodetector 16 having light receiving surfaces 17 divided into plural sections and obtaining the difference signal S2 of the outputs from the respective light receiving surfaces. An unused area 18 having a prescribed width is formed on the central part of the light receiving surface along the tracking direction. An output from the unused area 18 is not generated or used only for the alignment of optical axis at the time of manufacturing/assembling even if it is generated and not used at the time of normal operation. Consequently, when the deviation of the optical axis occurs due to a secular change in normal operation, by eliminating the mutual interference of the respective signals entered in the respective light receiving surfaces at the time of the deviation of optical axis, the error rate of wobble information is maintained. |
