Objective lens for optical recording media and optical pickup apparatus using the same

摘要

One surface of an objective lens (8) is provided with a zonal part which acts such that the quantity of light having a wavelength of λ1 is apparently canceled in the outer peripheral portion of the luminous flux due to an interference effect, whereas the quantity of light having a wavelength of λ2 in the outer peripheral part is kept as it is. The zonal part (14) has such a step that light supposed to pass a position corresponding to the zonal part if the zonal part does not exist and light passing a position at which the zonal part is formed if the zonal part exists generate therebetween a phase difference satisfying a predetermined conditional expression. The numerical aperture at a boundary position of the step has a value between two numerical apertures for the respective wavelengths λ1 and λ2.