| 摘要 |
PURPOSE:To make good separation and reproduction of information possible by reading the guide track information consisting of two information areas given by a phase change mode and an amplitude change mode, by means of differential outputs of the plural photodetectors disposed in a remote visual field area. CONSTITUTION:The light beam 100 from a semiconductor laser is condensed as a spot 103 on the guide track of a disc-shaped information carrier 1 via a condenser lens 4, anamorphic lenses 4, 5, a polarizing beam splitter 11, and a 1/4 wavelength plate 10 then via a tracking mirror 7 and a stop lens 8. The reflected light is polarized via the plate 10 and the splitter 11 and is separated to two beams 106a, b by a double prism 12. These beams condense at photodetectors 13, 14, by which a converging error signal is obtained. On the other hand, the remote visual field pattern 4 of the microspot 103 is formed via a beam splitter 10 at a quadrisected light detector 17, according to the output signal thereof the information on the phase change mode and the amplitude change mode is well separated and reproduced. |
