| 摘要 |
PURPOSE:To read a return laser beam from an optical disk, to output only an information reproduced signal by a nonseparated type photodetector and to output only an error signal by a separated type photodetector. CONSTITUTION:A laser beam outgoing from a semiconductor laser 21 is converged on the reflection film surface 3 of the optical disk 1 and the return beam reflected by the reflection film surface 3 passes through an objective lens 25 and is made incident to a beam splitter 23 having a first, a second beam splitters 23a, 23b. The incident return beam is reflected by the first beam splitter 23a and further the advancing direction is bi-sected by the second beam splitter 23b. At this time, one side of the bi-seated return beam is read by the nonseparated type photodetector 26 and only the information reproduced signal is outputted. Further, the other side of the bi-sected return beam is read by a quadripartite photodetector 29 and only the error signal consisting of the out-of-focus signal and the out-of-track signal of a light spot is outputted. |
