| 摘要 |
PURPOSE:To miniaturize an optical head as well as to increase the tracking range by dividing the reflected light in terms of space by a split prism which is brought close to or adhered to the output surface of the reflected light traveled straight forward by a beam splitter and giving one of the two divided beams to a tracking detector to detect a tracking error signal. CONSTITUTION:The reflected light (b) of a disk 9 passes through a diaphragm lens 7, a lambda/4 plate 5 and then a polarized beam splitter 4 and is made incident to a split prism 20. The prism 20 has a trapezoidal section with theta=45 deg., for example, and the light (b) passed through the splitter 4 is divided into two beams in terms of space when a split line (k) is set at the center of the optical axis. The left half of a beam (b) is totally reflected to the right side and turned into a beam (c). This beam (c) is converted into convergent light through a single lens 11 and made incident to a focus detector 14. While the right half of the beam (b) passes through the prism 20 and is turned into a beam (d). This beam (d) is made incident to a tracking detector 13. Then the variation of a diffraction pattern due to an information track 10 of a light spot X is detected to detect a tracking error signal. |
