OBJECTIVE LENS FOR OPTICAL INFORMATION RECORDING AND REPRODUCING DEVICE, AND OPTICAL INFORMATION RECORDING AND REPRODUCING DEVICE

摘要

PROBLEM TO BE SOLVED: To provide an objective lens for an optical information recording and reproducing device suitably constituted for performing recording and reproducing information to a plurality of optical disks having different specifications such as a BD and a DVD.SOLUTION: The objective lens for the optical information recording and reproducing device has, at least on one surface: a first region contributing to the converging of luminous flux having wavelengths λ1 and λ2 on recording surfaces of first and second optical disks and having diffraction structures where both diffraction orders where diffraction efficiencies are maximized upon the usage of the luminous flux having wavelengths λ1 and λ2 are first orders; and a second region converging the luminous flux having the wavelength λ1 on the recording surface of the first optical disk and not contributing to the converging of the luminous flux having the second wavelength λ2 and disposed at the outer side of the first region where a secondary coefficient of an optical path difference function regulating the diffraction structure of the first region and a focal distance in the luminous flux of the diffraction order where the diffraction efficiency of the wavelength λ2 is maximized satisfy a prescribed condition.