| 摘要 |
PURPOSE:To make a titled optical head low in its cost and compact, and to process a reproducing signal at a high speed by constituting so that a part of a light which has passed through an objective lens passes through a spherical lens or a non-spherical lens, and a part of the remaining light passes through a cut and lacking part. CONSTITUTION:A divergent laser beam reflected from a recording layer 28 is converted to a parallel luminous flux by an objective lens 26 at the time of focusing, passes through a lambda/4 plate 25 again and is returned to a polarized beam splitter 24. As for the laser beam, its plane of polarization is rotated by 90 deg. comparing with the case when it has passed through the splitter 24 by executing a reciprocating motion to the lambda/4 plate 25, and it is reflected by this polarized beam splitter 24. The laser bean which has passed through the first projecting lens 30 is irradiated to the first photodetector 31, and a tracking shift is detected and a signal is read. On the other hand, the laser beam which has passed through the part lacked by cutting the first projecting lens 30 is irradiated to the second photodetector 33 by the second projecting lens 32, and an out-of-focus is detected. |
