| 摘要 |
PURPOSE:To prevent defocusing by arranging an objective glass, which is brought into contact with a recording medium, in a beam emitting part. CONSTITUTION:A beam 3 emitted from a laser diode 2 is corrected to a parallel beam by a collimator lens 4 and is made incident on a polarizing beam splitter 5. This beam is transmitted through the polarizing beam splitter 5 and is converted from the linearly polarized beam to a circularly polarized beam by a quarter-wave plate 6 and is converged by a converging lens 7 and is led to a objective glass 8. This objective glass 8 has a spherical front face, and positions of the objective glass 8 and the converging lens 7 are so adjusted that the beam converged by the converging lens 7 is converged on the apex of this spherical face. Thus, defocusing is prevented. |
