| 摘要 |
PURPOSE:To facilitate the control of an optical system by providing photodetecting elements of >=2 divisions having divided lines which are parallel to the divided line of each optical path on the optical axis of each branched optical path. CONSTITUTION:The linear polarized beams given from a light source 1 are converted into parallel beams through a collimator lens 2 and then converted into circular polarized beams by a 1/4 wavelength plate 4 via a polarized beam splitter 10. The circular polarized beams are made incident to a disk 6 serving as a recording medium via an objective lens 5. The reflected circular polarized beams given from the disk 6 are converted into linear polarized beams having the polarizing direction orthogonal to the going path after passing through the lens 5 and then the plate 4 and then made incident on the splitter 10. Here the reflected luminous flux of one side and that of the other side are branched in the direction orthogonal to the incident luminous flux and also in the directions different by 180 deg. from each other centering on the divided lines which are opposite to the track direction and pass through the optical axis. These branched luminous fluxes are made incident on 2-split photodetecting elements 11 and 12 respectively. |
