Patent ID: 8233371

Claim:
An objective lens to be incorporated into an optical head, wherein: the objective lens includes a first lens and a second lens substantially in close contact with each other such that optical axes thereof match each other, and acts as a convex lens as a whole; the first lens and the second lens each include a central portion including the optical axis and a peripheral portion located in a periphery of the central portion; the central portion of the first lens acts as a convex lens; the central portion of the second lens acts as a concave lens; and where the refractive index of the first lens at d line (wavelength: 587.56 nm) is nd1, the Abbe constant of the first lens represented using the refractive indices at d line, F line (wavelength: 486.13 nm) and C line (wavelength: 656.27 nm) is νd1, the refractive index of the second lens at d line is nd2, and the Abbe constant of the second lens represented using the refractive indices at d line, F line and C line is νd2, the objective lens fulfills nd1>nd2 and νd1>νd2; and the objective lens has three lens faces crossing the optical axis of: a first lens face which is a lens face of the first lens which is not in contact with the second lens, a second lens face which is a border between the first lens and the second lens substantially in close contact with each other, and a third lens face which is a lens face of the second lens which is not in contact with the first lens; and among effective areas of at least one of the first lens face, the second lens face and the third lens face, a central effective area including the optical axis and a peripheral effective area located in a periphery of the central effective area are formed in different aspheric shapes; wherein in each of the first lens face, the second lens face and the third lens face, the central effective area and the peripheral effective area are formed in different aspheric shapes, and light from a light source of the optical head is incident on the peripheral effective area.