Optical recording/reproducing apparatus for multi-layer recording media that alleviates adverse effect of spherical aberration beyond compensation by changing the numerical aperture of combined lenses

摘要

An optical recording/reproducing apparatus is intended for a recording medium having at least two information recording layers. The apparatus has at least two lenses, a first lens and a second lens, for condensing a light beam to irradiate an information recording layer. The at least two lenses are designed such that a light beam condensed by these lenses upon an information recording layer closest to these lenses has a minimum spherical aberration.