Patent ID: 8154979
Filing Date: 2012-04-10
Classification: G02B,G11B

Abstract:
1. An objective lens used for an optical pickup apparatus to perform writing and/or reading of an optical information recording medium by light from a light source, comprising an antireflective film on a surface of a light source side, wherein a light flux of a plurality of wavelengths including a wavelength λ1 which is within a range of 380 nm≦λ1≦420 nm and a wavelength λ2 which is within a range of 630≦λ2≦810 nm, is condensed on the optical information recording medium by the objective lens, a numerical aperture on the light source side with respect to the wavelength λ1 is within a range from 0.8 to 0.9, the numerical aperture on the light source side with respect to the wavelength λ2 is 0.7 or less, the number of layers of the antireflective film is 7 or more, and a band of the antireflective film is within a range from 700 nm to 800 nm in a state where a reflectance of a light flux perpendicularly entering a central portion of the surface in a wavelength region from 400 nm to 1200 nm is continuously 3.0% or less, wherein the band of the antireflective film is a difference between an upper limit and a lower limit of wavelengths that satisfy the reflectance of 3.0% or less among the wavelength region from 400 nm to 1200 nm.