| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a compatibility among three types of optical discs different in wavelength by using one common objective lens without complicating the configuration thereof, and also to provide a favorable recording and reproducing characteristics regardless of variation in temperature and wavelength. <P>SOLUTION: An optical pickup is equipped with: an objective lens 34 that receives light beams having at least three wavelengths λ1, λ2 and λ3 satisfying λ1<λ2<λ3; and a diffraction unit 50 converging the light beams having the three wavelengths λ1, λ2 and λ3 on a signal recording surface of the corresponding optical disc by the objective lens 34. The diffraction unit 50 has a first region 51 that is provided in an innermost peripheral part so as to diffract the light beams, a second region 52 that is provided outside the first region so as to diffract the light beams, and a third region 53 that is provided outside the second region. The diffraction structure of the first region 51 comprises a step structure having: a predetermined order having the maximum diffraction efficiency; and a predetermined level. The optical path difference phase amount of each level has a specific relation. <P>COPYRIGHT: (C)2011,JPO&INPIT |
