Patent ID: 7313074

Claim:
An optical pickup comprising: a first optical source producing a first optical beam having a first wavelength λ 1 ; a second optical source producing a second optical beam having a second wavelength λ 2 ; and an objective lens focusing any of said first and second optical beams on a corresponding optical recording medium, said objective lens focusing any of said first optical beam and said second optical beam incident to an incident side of said objective lens, to an optical recording medium provided at an exit side of said objective lens, said objective lens having a single-lens construction and defined by a non-spherical convex surface at an incident side and an exit side, wherein there is satisfied a condition: νd>35 (1) 1.58>nd (2) 0.58nd−0.29≦R1/ f≦ 0.62 nd −0.31 (3) where nd and νd represent respectively the refractive index and Abbe number for a D-line, R 1 represents the paraxial radius of curvature and f represents the focal distance, said objective lens having a first effective numerical aperture value NA(λ 1 ) for said first optical beam and a second effective numerical aperture value NA(λ 2 ) for said second optical beam, said first optical beam incident to said objective lens having a first beam diameter φ 1 , said second optical beam incident to said objective lens having a second beam diameter φ 2 , said first and second effective numerical aperture values NA(λ 1 ), and NA(λ 2 ) and said first and second beam diameters satisfying a relationship NA(λ1)>NA(λ2) (4) φ2=φ1. (5)