Patent ID: 8315130

Claim:
An objective lens comprising a resin material to focus incident rays, which have a wavelength of 410 nm or less and are emitted from a light source, on an optical disc at a numerical aperture of 0.8 or more, wherein when a lens tilt sensitivity is defined as an amount of a 3rd-order coma aberration caused per a lens tilt of 1 degree, the lens tilt being an angle formed between an optical axis of the objective lens and a system optical axis of an optical system including the objective lens at 0° C., the lens tilt sensitivity is 130 mλrms/degree or less, and wherein a refractive index n of the resin material satisfies 1.50≦n≦1.60 at a wavelength of 405 nm, and a refractive index gradient dn/dT of the resin material relative to a temperature thereof satisfies −1.3×10 −4 ≦dn/dT≦−1.0×10 −4 .