| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent diffraction efficiency from being reduced in recording and reproduction light that is generated from a plurality of light sources and has a different wavelength, and to simultaneously optimize the diffraction efficiency and a diffraction angle. <P>SOLUTION: An optical pickup 1 comprises a basic optical system; an objective lens 14 for condensing light beams onto the recording surface of an optical disk; and a set of diffraction elements 15, 16 arranged immediately before the objective lens 14. The first diffraction element 15 is a braze type diffraction element and has groove depth, where transmission efficiency in primary diffracted light or negative primary diffracted light when light beams 41, 42, 43 are transmitted becomes the maximum as compared with diffracted light having other orders. And the second diffraction element 16 is a step type diffraction element and has groove depth, where transmission efficiency in zero-order diffracted light when the light beams 41, 43 are transmitted becomes the maximum as compared with diffracted light having other orders and that in the primary or negative primary diffracted light becomes the maximum as compared with diffracted light having other orders in the light beam 42. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
