| 摘要 |
PURPOSE:To improve S/N and to miniaturize and reduce weight by incorporating a hologram diffraction grating which divides an optical path of returning light reflected on a recording media and gives astigmatism to + or - primary light. CONSTITUTION:The light reflected on an optical disk 13 passes through a condenser lens 14 again and is diffracted by a hologram diffraction grating 15, and then the light guided by a light guiding pathes 17 and 18 of a photodetector 12 is respectively detected by photodetectors 19 and 20 placed opposing each other at the ends of respective outgoing sides. The condenser lens 14 is controlled in focusing in the direction of distance so that distance R to the optical disk 13 is always maintained at focused condition by a lens actuator, resulting in forming a micro spot on the optical disk 13 so as to record or reproduce information with high density. |
