| 摘要 |
PURPOSE:To eliminate the need for adjusting operation by forming an optical path for allowing a photodetecting element for monitoring to photodetect only light from a light emitting element directly in a container which contains the light emitting element and photodetecting element for monitoring closely. CONSTITUTION:The optical path 7B for the photodetecting element 8 to be formed in a housing 7A so that the photodetecting element 8 for monitoring detects only the light from the light emitting element 4 is set at such a position and in such a direction that reflected light from the reverse surface of a disk 1 and an external light noise are cut off. Then when the disk 1 rotates, the light from the light emitting element 4 is passed through a slit 1A and photodetected by a photodetecting element group 5 through slits 3A, 3B and 3C of a fixed slit plate 3. At the same time, part of the light emission output of the light emitting element 4 is photodetected by the photodetecting element 8 for monitoring directly to detect the intensity of the light emission output of the light emitting element 4. |
