Patent ID: 6650612
Filing Date: 2003-11-18
Classification: G11B

Abstract:
An optical head, comprising:a first light source for emitting light with a first wavelength; a second light source for emitting light with a second wavelength longer than the first wavelength; a third light source for emitting light with a third wavelength longer than the second wavelength; and an objective lens for focusing the respective lights with the first, second, and third wavelengths on information recording surfaces of information recording media corresponding to the lights with the respective wavelengths, wherein the objective lens is designed so as to reduce aberration with respect to the light with the first wavelength, and optical-path lengths from the respective second and third light sources to the objective lens are shorter than an optical-path length from the first light source to the objective lens so that aberration caused by the objective lens due to chromatic dispersion caused by a material of the objective lens is reduced with respect to the respective lights with the second and third wavelengths.