| 摘要 |
PURPOSE:To record and reproduce the information with high density and high reliability by detecting the difference of the luminous intensity before and after a recording medium in its advancing direction in a far-field of a reflected light or a transmitted light and extracting the difference of output from each part. CONSTITUTION:A 1/4 wavelength plate 5 changes a linearly polarized light passing through a polarized beam splitter 4 into a circularly polarized light. The phase of the circularly polarized light reflected from an information recording region on a medium 7 is led and that of the circularly polarized light reflected from the non-recording region is lagged. The photodetecting face of a photodetector 11 is split into two before and after the medium in its advancing direction, then the far field pattern is detected while being divided into the forward/backward direction and the difference in the output currents from each part is amplified by a differential amplifier 12. In radiating a light to the front ridge or the tail ridge of a pit, a readout signal 101 causing a positive or negative peak is processed by a readout signal processing circuit 13 to reproduce the information recorded on the recording medium 7. Thus, the recorded information is reproduced accurately without being affected by the luminous intensity fluctuation or the fluctuation of the medium reflectance.
|
