Patent ID: 7903529

Claim:
An optical head, comprising: a first light source for emitting a laser beam having a first wavelength; a transmitting/reflecting member for transmitting the laser beam of the first wavelength emitted from the first light source; and an objective lens for focusing the laser beam of the first wavelength having passed through the transmitting/reflecting member on a first information recording medium with a numerical aperture NA ≧0.60, wherein: the transmitting/reflecting member includes a first surface on which the laser beam of the first wavelength emitted from the first light source is incident and a second surface which faces the first surface and from which the laser beam of the first wavelength emerges; an angle α defined between the first and second surfaces satisfies a condition of α≠0; a third-order astigmatism and a third-order coma aberration occurring when the laser beam of the first wavelength passes through the transmitting/reflecting member are both 5 mλ or smaller; and a trefoil aberration occurring when the laser beam of the first wavelength passes through the transmitting/reflecting member is 20 mλ or smaller.