| 摘要 |
<p>An optical pickup according to the present invention includes a plurality of light sources for emitting a plurality of light beams including first and second light beams of respectively different wavelengths, an objective lens for converging the plurality of light beams, and a grating structure shaped axisymmetrically with respect to the optical axis of the objective lens. P th -order diffracted light (where p is a non-zero integer) which is formed from the first light beam (e.g. blue) by the grating structure is converged on an information layer of an optical disk (e.g. a BD) corresponding to the first light beam, owing to the converging actions of the objective lens and grating structure. Moreover, q th -order diffracted light (where q is a non-zero integer such that q‰ p) which is formed from the second light beam (e.g. red or infrared) by the grating structure is converged on an information layer of an optical disk (e.g. a DVD or CD) corresponding to the second light beam, owing to the converging actions of the objective lens and the grating structure. Thus, by appropriately using diffracted light of different orders, it becomes possible to perform convergence on optical disks of different wavelengths and base thicknesses, with reduced spherical aberration.</p> |
