Optical system of optical information recording/ reproducing apparatus

Claim 1

An optical system of an optical information recording/reproducing apparatus, said system comprising: a light source for emitting divergent luminous flux; a collimator lens for collimating luminous flux emitted from said light source; an objective lens for converging luminous flux emitted from said collimator lens onto a medium, both surfaces of said objective lens comprising convex aspherical surfaces and each having a radius of curvature which increases towards a periphery from a center of said objective lens, said objective lens being disposed such that a surface of said objective lens having a smaller radius of curvature faces towards said light source; a beam splitter for splitting luminous flux reflected by the medium from a light path directed to the light source and guiding the luminous flux to a light receiving system, said beam splitter positioned between said collimator lens and said objective lens; a chromatic aberration correcting element having almost no power disposed between said objective lens and said beam splitter to correct a chromatic aberration of said objective lens; and means for moving said objective lens independently of said chromatic aberrating correcting element at least in an optical axis direction of said objective lens.