Patent ID: 7072114

Claim:
An optical system for use with first and second optical recording media having different thicknesses, comprising: at least one light source to generate first and second light beams of respectively different wavelengths corresponding to the first and second optical recording media; an optical unit to form beam spots on the first and second optical recording media having the different thicknesses using the corresponding first and second light beams; and at least one light detector to detect the first and second light beams reflected from the first and second optical recording media after being formed into the beam spots by the optical unit, wherein: the optical unit comprises: 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, 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.