Optical head and recording/reproducing device

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 aberration-correcting lens group corrects spherical aberration occurring at each optical surface of an optical system, 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, wherein
• the light source is a semiconductor laser having an emission wavelength of at most 440 nm, the objection 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 the aberration-correcting lens group is composed of a positive lens having an Abbe number of at least 55 and a negative lens having an Abbe number of at most 35.

A recording/reproducing apparatus 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:
• an actuator for changing a space between the positive lens group and negative lens group which constitute the aberration-correcting lens group, in an axial direction;
• and
• a photosensor for detecting a light beam emitted from the light source, focused by the objective lens on an optical recording medium and reflected by the optical recording medium,
• 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.

A recording/reproducing apparatus 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;
• an actuator for changing a space between the positive lens group and negative lens group which constitute the aberration-correcting lens group, in an axial direction;
• and
• a photosensor for detecting a light beam emitted from the light source, focused by the objective lens on an optical recording medium and reflected by the optical recording medium, wherein
• the aberration-correcting lens group corrects spherical aberration occurring at each optical surface of an optical system, 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 wherein
• the light source is a semiconductor laser having an emission wavelength of at most 440 nm, the objective lens is made of virtreous 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 the aberration-correcting lens group is composed of a positive lens having an Abbe number of at least 55 and a negative lens having an Abbe number of at most 35.