Objective lens device for correcting chromatic aberration and optical pickup employing the same

An optical pickup comprising:

• a light source which emits light;
• an objective lens device which focuses the light emitted from the light source into a light spot formed on a recording medium, the objective lens device comprising three lenses, wherein:
• a first of the three lenses has a negative power and is formed of a material having an Abbe number which is 45 or less in line d,
• at least one surface of surfaces of the three lenses is aspherical,
• the objective lens device has a numerical aperture of 0.70 or more, and
• where a focal length of the first lens is ƒn and an overall focal length of the objective lens device is ƒ, the objective lens device satisfies the equation:
• - 2.4 < fn f < - 1.4 ;
• an optical path changer which changes a proceeding path of incident light, the optical path changer arranged on an optical path between the light source and the objective lens device;
• and
• a photodetector which receives light reflected by the recording medium and via the objective lens device and the optical path changer.

An optical pickup for recording information to and/or reproducing information from a recording medium, the optical pickup comprising:

• a light source which emits light;
• a photodetector;
• and
• an optical system which communicates the emitted light to the recording medium and communicates light reflected by the recording medium to the photodetector, the optical system comprising:
• an objective lens device which forms the emitted light into a light spot on the recording medium, the objective lens device comprising first, second and third lenses, wherein:
• the first lens has a negative power and is formed of a material having an Abbe number which is 45 or less in line d,
• the second and third lenses have a positive power,
• one of the second and third lenses is aspherical,
• the first lens is disposed between the second and third lenses on an optical path between the light source and the recording medium,
• the objective lens device has a numerical aperture of 0.70 or more, and
• where a focal length of the first lens is ƒn and an overall focal length of the objective lens device is ƒ, the objective lens device satisfies the equation:
• - 2.4 < fn f < - 1.4 .

An optical pickup for recording information to and/or reproducing information from a recording medium, the optical pickup comprising:

• a light source which emits light having a wavelength (λ) in a range of 400 nm≦λ≦420 nm;
• a photodetector;
• and
• an objective lens device which forms the emitted light as a spot on the recording medium and communicates light reflected by the recording medium toward the photodetector, the objective lens device comprising:
• a first lens having a negative power and formed of a material having an Abbe number which is 45 or less in line d,
• a second lens having a positive power and forming a doublet with the first lens, and
• a third lens having a positive power, wherein:
• one of the second and third lenses is aspherical, the objective lens device has a numerical aperture of 0.70 or more;
• and where a focal length of the first lens is ƒn and an overall focal length of the objective lens device is ƒ, the objective lens device satisfies the equation:
• - 2.4 < fn f < - 1.4 .