Patent ID: 6985293

Claim:
An optical unit to form beam spots on first and second optical recording media having different thicknesses using corresponding first and second light beams of respectively different wavelengths, comprising: an inner portion having a first optical property by which the first and second light beams are directed to the corresponding first and second optical recording media so as to be useable in recording and/or reproduction data with respect to the first and second optical recording media; a first diffractive portion having a second optical property which selectively diffracts the first and second light beams according to the different wavelengths; and a second diffractive portion having a third optical property which selectively diffracts the first and second light beams according to the different wavelengths, wherein: the second diffractive portion selectively diffracts the first and second light beams so as to change a numerical aperture of the optical unit and to selectively reduce a spherical aberration with respect to recording and/or reproducing the data with respect to the first and second optical recording media, and the second optical property is different from the third optical property.