Patent ID: 6721259
Filing Date: 2004-04-13
Classification: B82Y,G11B

Abstract:
An optical head characterized by comprising:a light source; an objective lens composed of at least two lenses and having a numerical aperture of at least 0.80; an aberration-correcting lens group arranged between the light source and the objective lens and composed of a positive lens group and a negative lens group; wherein the light source is a semiconductor laser having an emission wavelength of at most 440 nm: wherein the objective lens is made of vitreous material having an Abbe number of at most 95.0 at d line and has a focal distance of at least 1.4 mm; and wherein the aberration-correcting lens group corrects spherical aberration occurring at each optical surface of an optical system and chromatic aberration resulting from the wavelength of the light source, as a space between the positive lens group and negative lens group which constitute the aberration-correcting lens group is changed in an axial direction.