| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical element, an objective optical element and an optical pickup device, which are used for reproducing and/or recording the information with respect to two kinds of optical information recording media having different substrate thicknesses and are able to obtain a sufficient diffraction efficiency regarding two kinds of wavelengths. <P>SOLUTION: This optical element 10 has a diffractive structure 20 comprising a diffraction ring zone 21, and an optical path difference imparting structure 30 on an optical surface of the diffraction ring zone 21 for imparting the optical path difference to passing luminous flux of this ring zone. The optical surface of the diffractive structure has a structure 22 having such a diffracting operation that an L-th diffracted light of the luminous flux of wavelength λ1 and an M-th diffracted light of the luminous flux of wavelength λ2 become respectively the maximum diffraction efficiency when the optical path difference applying structure is not prepared. Also, by giving the change of phase to at least one out of the L-th diffracted light or the M-th diffracted light by the optical path difference imparting structure, the absolute value of a phase difference between the L-th diffracted light and the M-th diffracted light is made smaller as compared with the case of assuming that the optical path difference imparting structure is not prepared. <P>COPYRIGHT: (C)2009,JPO&INPIT |
