Recording and reproducing device and objective lens for recording and reproducing optical information on recording media

摘要

A device of recording and reproducing on an optical information recording media, includes a light source composed of a semiconductor laser to emit a divergent luminous flux; an objective lens to receive the divergent luminous flux and to converge the diverging luminous flux onto the optical information recording media; and a tracker for tracking a converged luminous flux on the optical information recording media by moving the objective lens in a direction perpendicular to an optical axis. The objective lens has an astigmatism so that a quantity of the astigmatism of a wave-front emitted from the objective lens shows a minimum value at a position where the objective lens is moved away from the optical axis by a tracking operation of the tracker. <IMAGE>