| 摘要 |
PURPOSE:To prevent dust or the like from penetrating an optical head without raising the cost, by arranging a 1/4 wavelength plate between an objective lens and a recording medium. CONSTITUTION:A 1/4 wavelength plate 1 arranged normally between a polarizing beam splitter 5 and a disc 3 is arranged between an objective lens 2 and the disc 3 to prevent sticking of dust or the like to the lens 2. In this case, though the 1/4 wavelength plate 1 is exposed to dust or the like, the surface of the plate 1 is washed easily because the surface of the plate 1 is plane and wide. Thus, the number of parts is not increased but only the position is changed, and dust or the like is prevented from penetrating the optical head without raising the cost. |
