| 摘要 |
PURPOSE:To obtain one-beam system at recording and three-beam system at reproduction by arranging a diffraction grating outside the light path from the top of the light path of a light path system at recording, and providing the changing-over means arranged on an optical path from the outside of the light path at reproduction. CONSTITUTION:The optical system of an optical head is composed by using a semiconductor laser 10 and providing a diffraction grating 13. At recording, the grating 13 is arranged outside the light path from the top of the light path of a light path system by a diffraction grating changing-over device 30. At reproduction, the grating 13 is arranged on the light path from the outside of the light path of the light path system by the device 30. Thus, at recording, the one-beam system can be obtained, at reproduction, the three-beam system can be obtained and the optical head of both systems can be composed of the single optical head. |
