| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical head device for preventing offset from being caused by a reflected light at other information recording layers, on a focus error detecting signal of an information recording layer whereon the recording/ reproducing operation is being performed, when the recording or reproducing operation is carried out with respect to a multi-layer optical disk. <P>SOLUTION: The device is furnished with a 1st optical path for converging laser beams emitted from a laser beam source 16 on the specified information recording layer of the multi-layer optical disk 11 through an objective lens 20 and a 2nd optical path for converging the laser beams which are run backward through the objective lens 20 by being reflected at the specified information recording layer of the optical disk 11, by a detection lens 21 to guide them to a photodetector 23 through a diffraction element 22, then the laser beams converged by the detection lens 21 are set so as not to focus at this side of the diffraction element 22 independently of the position of the objective lens 20 in the focusing direction. <P>COPYRIGHT: (C)2003,JPO |
