| 摘要 |
PURPOSE:To accurately detect the signals by forming a light shielding film in an area except an effective area where the light emitted from a light source and the regular reflected light received from a recording medium pass through on a single side surface of a diffraction element. CONSTITUTION:A light shielding film 16 is formed in an area except an effective area where the light emitted from a light source 11 and the regular reflected light received from a recording medium 12 pass through on a signal side surface 14a of a diffraction element 14. Therefore the beams dispersed by the scratches, the foreign matters, etc., on the surface of the medium 12 are prevented by the film 16 from passing through the areas except the effective area. Thus the dispersed beams never reach a photodetector 15. As a result, the photodetector 15 can accurately detect the signals. |
