Patent ID: 7277372

Claim:
An optical disc drive for accessing at least three types of optical discs, which are associated with multiple different numerical apertures and multiple different wavelengths, the optical disc drive comprising: light source means for selectively emitting one of a plurality of light beams with multiple different wavelengths; and focusing means for focusing a light beam on a data storage layer of a given optical disc at a changeable numerical aperture; detecting means for detecting light that has been reflected from the given optical disc, on which the light beam was focused by the focusing means; setting means for setting the numerical aperture of the focusing means equal to a first one of the multiple different numerical apertures, and for setting the wavelength of the light beam equal to a first one of the multiple different wavelengths, the first numerical aperture being smaller than any of the other numerical apertures, the first wavelength being longer than any of the other wavelengths; and recognizing means for recognizing the type of the given optical disc by a signal representing a reflected and detected portion of the light from the optical disc on which the light beam of the first wavelength was focused at the first numerical aperture that had been selected by the setting means, wherein the at least three types of optical discs include light beam passage layers with multiple different thicknesses to pass the light beam, and wherein the optical disc drive further comprises: spherical aberration correcting means for correcting a spherical aberration produced on the spot of the light beam that has been focused on the data storage layer of the given optical disc; and spherical aberration regulating means for setting the magnitude of correction to be made by the spherical aberration correcting means equal to a fixed predetermined value when the setting means sets the numerical aperture of the focusing means equal to the first numerical aperture.