| 摘要 |
PURPOSE:To improve both mechanical and optical performances and also to attain a thin and small structure for an optical head by reflecting the light upward at a place right under an objective lens and leading the reflected light to a recording medium from a light source set in parallel to an objective lens arm provided to an actuator. CONSTITUTION:The light given from a semiconductor laser 21 is made incident on a polarizing prism 23 in the form of parallel luminous fluxes through a lens 22 to transmit through a polarizing film 24 and then reflected totally and rectangularly by a prism 25. This reflected light is led to an objective lens 27 through a lambda/4 plate 26 and formed into a light spot on an optical disk. The light reflected by the optical disk travels along the same optical path as a going path up to the prism 23 to be reflected by the film 24 and is reflected again on an optical surface 28a of a critical angle prism 28 to be made incident on a photodetector 29. The detector 29 contains four photodetecting areas 29a-29d which are divided half in radial and tangential directions of the optical disk respectively. Then a data signal, a focus error signal and a radial error signal are obtained from these outputs of areas 29a-29d. |
