| 摘要 |
PURPOSE:To make it possible to record/reproduce data to/from an optical disk for long wavelength by means of a light source for short wavelength by increasing/decreasing an output from the light source in accordance with the stop diameter of an aperture stop to be changed in accordance with pit size and approximately fixing the quantity of light arriving at a photodetector. CONSTITUTION:A laser beam 2 projected from the short wavelength light source 1 arrives at a collimeter lens 4 through a beam splitter 3 and an auxiliary optical system lens 9 and converged by an objective lens 6 through the aperture stop 5 to read out a pit on an optical disk 7. Light reflected by the disk 7 is returned to the splitter 3 and converted into an electric signal, which is processed. The stop 5 increases/decreases aperture stop in accordance with the pit size, the light source 1 is controlled by a driver 30 in accordance with the diameter of the stop and the quantity of light to be reached to the photodetector 8 is approximately fixed. Consequently, an information pit recorded by the light source having different wavelength can be reproduced. |
