DIFFRACTION TYPE OPTICAL PICKUP LENS AND OPTICAL PICKUP DEVICE USING THE SAME

摘要

PROBLEM TO BE SOLVED: To determine the grating pitch of a diffraction grating so that processing is easy even at a lens peripheral part distant from an optical axis by making the shape of a converging lens bear refracting power, using an aspheric shape for excellently converging luminous flux of wavelength λ1 for recording and reproducing a 1st optical recording medium, and using a zone plate for excellently converging luminous flux of wavelength λ2 for recording and reproducing a 2nd optical recording medium. SOLUTION: The laser 2 of 650 nm (λ1 ) in wavelength is excellently converged on a recording surface 36A of a DVD 36 by the convex shape of a lens 8 and aspheric surfaces formed on both the surfaces of the lens. The laser light 2 of 780 nm (λ2 ) in wavelength is also converged on a recording surface 26A of a CD-R 26 by a lens 8 having an spherical surface while having aberrations corrected by the zone plate 12 with wavelength selectivity formed on the light-source side surface of the lens 8.