Patent ID: 7369480

Claim:
An optical pickup device comprising a first light source emitting a first light beam having a wavelength λ 1 within a range of from 390 nm to 420 nm and at least one optical element, the optical pickup device being capable of performing recording and/or reproducing of information of a first optical disk having a protective substrate thickness d 1 mm using the first light beam from the first light source, wherein the optical element is made of a mixed material produced by dispersing particles into a resin, a sign of a refractive index change Δn 2 /Δt of the particles owing to a temperature change is opposite to a sign of a refractive index change Δn 1 /Δt of the resin owing to a temperature change, or an absolute value of the refractive index change Δn 2 /Δt is smaller than an absolute value of the refractive index change Δn 1 /Δt, and a spherical aberration SA 1 [λ rms] produced when an operating temperature of the optical pickup device rises by 30° C. satisfies a following relation, |( SA 1 /λ 1 2 )·(Δ n 3 /Δt )· NA 4 ·2 d 1 ·10 9 |≦9.9 where SA 1 denotes a sum of squares of a third order spherical aberration, a fifth order spherical aberration and a seventh order spherical aberration, Δn 3 /Δt denotes the refractive index change owing to the temperature change of the mixed material, and NA denotes a numerical aperture on an exit side of an optical element located nearest to an optical disk side among optical elements which the optical pickup device contains.