| 摘要 |
PURPOSE:To constitute a small-sized, simplified optical pickup device and to perform differential detection with a good SN ratio by detecting diffracted light from a light splitter which has a diffraction structure divided into plural parts through polarizing elements which have angles of mutual symmetry. CONSTITUTION:Luminous flux emitted by an LD 53 is collimated by a collimator lens 54 into parallel luminous flux, which is transmitted through the light splitter 55 and converted on a recording medium 57 in a fine spot through an objective 56. Reflected light from the medium 57 passes through the lens 57 again and is diffracted by the diffraction grating structure of the splitter 55 to enter a photosensor 59 through a polarizing element 58. Then, the light entering the sensor 59 is processed by a differential detecting method. |
