| 摘要 |
PURPOSE:To use both writing and reading systems in common with each other and at the same time to attain the additional writing by using two lasers having the same polarizing direction and forming the same beam form and the same optical path with an optical means (polarized beam splitter) which secures the coincidence among optical paths of output beams and a 1/2 wavelength plate which secures the coincidence among beam shapes. CONSTITUTION:A 1/2 wavelength 33 is inserted only to an optical system of one side, and the polarizing direction is set vertical. At the same time, a polarized beam splitter 34 is used for connection of the plate 33 to obtain the same optical path and the same beam form. At the time of writing, only the semiconductor laser 31 of one side is oscillated intensively so that the temperature at the position of a beam spot on a disk 7 is set higher than the Curie point. Then the information is written on the disk 7. While at the time of reading, only the semiconductor laser 11 of the other side is oscillated with reduced intensity to read the information written on the disk 7. Then both lasers 11 and 31 are simultaneously oscillated at the time of additional writing. Then the additional writing is carried out with the beam of the writing laser 31 while the tracking control is performed with the beam of the reading laser 11. |
