| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent transmission diffraction efficiency of recording reproducing light beams of different wavelengths which are radiated from a plurality of light sources from lowering and to optimize both the diffraction efficiency and angle of diffraction. <P>SOLUTION: The optical pickup is provided with a light source, a light detection element, a spectral element for branching an emitted light and return light, an objective lens 14, and a pair of diffraction element 15 and a diffraction element 16 placed just in front of the objective lens 14. The first diffraction element 15, which is a blazed grating, has a groove depth in which transmission diffraction efficiency of a primary diffracted light or minus primary diffracted light when transmitting each light beam becomes maximum compared with other orders of diffracted lights. The second diffraction element 16, which is a stepped grating, has a groove depth in which the transmission diffraction efficiency of a zero-order diffracted light with respect to a light beam 51 and light beam 53 becomes maximum and the transmission diffraction efficiency of the primary diffracted light or minus primary diffracted light with respect to a light beam 52, becomes maximum compared with other order diffracted lights. <P>COPYRIGHT: (C)2007,JPO&INPIT |
