| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem in which quantitative guide lines capable of reducing a symbol error rate have been demanded. <P>SOLUTION: There is provided an objective lens comprising a diffraction section that focuses first laser beams corresponding to a first optical disk into a data recording section of the first optical disk having a first transmission layer, focuses second laser beams corresponding to a second optical disk into a data recording section of the second optical disk having a second transmission layer having a thickness greater than that of the first transmission layer and focuses third laser beams corresponding to a third optical disk into a data recording section of the third optical disk having a third transmission layer having a thickness greater than that of the second transmission layer. In the objective lens, a ratio of the first laser beams focused into the data recording section of the first optical disk to the first laser beams made incident to the objective lens is calculated on the basis of an in-plane efficiency distribution function indicating the ratio by corresponding the ratio to a distance from an optical axis of an incident side surface in a radial direction. Further, an evaluation parameter having correlation with a symbol error rate corresponding to the first optical disk has a value corresponding to the symbol error rate less than a predetermined value. <P>COPYRIGHT: (C)2013,JPO&INPIT |
