| 摘要 |
PURPOSE:To enable interchange with lower rank reading and writing by one optical head and to enable recording and reproducing with an optical desk for high densities. CONSTITUTION:The optical head includes a light source 1 which emits a first light beam of a first wavelength, a light source 2 which emits a second light beam of a second wavelength longer than the first wavelength and an optical system which introduces the first and second light beams to the optical disk 9 and introduces the reflected light from the optical disk to a photodetector 11. The optical disk described above includes an objective lens 8, a beam splitter 5 which has the characteristics of a reflection mirror to the first wavelength and has the characteristic to allow the transmission of a p polarized component for the second wavelength and to reflect an s polarized light component and a quarter-wave plate 7. Recording is executed by the second light beam and reproducing by the first light beam, respectively, when the disk for high densities is set. The recording and reproducing are executed by the second light beam when the disk for low densities is set. |
