| 摘要 |
<P>PROBLEM TO BE SOLVED: To enhance an improvement of quality of a reproduction signal by reducing an inter-layer stray light without increasing a scale of a focus control mechanism and the like in an optical head apparatus to be used for a recording and reproducing operation of a multi-layer optical recording medium. <P>SOLUTION: The optical head apparatus (optical head) 14 for the multi-layer optical recording medium includes the focus control mechanism utilizing an astigmatism, and this focus control mechanism includes a sensor lens 80 including a cylindrical lens 80B, and by a light beam passing through the sensor lens 80, the astigmatism is generated, which linearly focuses in the Y-direction at a position of front side focal line 84A located close to the sensor lens and linearly focusing in the X-direction at a position of rear side focal line 84B located far from the sensor lens, and a photodetector 25 is prepared at the position between the front side focal line 84A and the rear side focal line 84B for detecting the focus position from a shape of the light beam, and a shield plate 82 is arranged at the position of front side focal line 84A, having a window section 83 through which the focal line is passed, with the size such as shutting down the stray light reflected from a recording layer of the outside of the focal point. <P>COPYRIGHT: (C)2010,JPO&INPIT |
