Optical pickup device using an intermediate lens which slightly converges the light beam

Abstract

An optical pickup device comprises a light beam source, an objective lens system for causing a light beam emitted from the light beam source to impinge upon a record medium and for receiving a reflected light beam from the record medium, and intermediate lens system composed of a single lens element for causing the light beam emitted from the light beam source to be slightly converged and to enter into the objective lens system and for receiving the reflected light beam transmitted through the objective lens system. A beam splitter separates the reflected light beam transmitted through the objective lens system and the intermediate lens system from the light beam emitted from the light beam source, and a photodetector detects the reflected light beam separated by the beam splitter. Spherical aberration induced by the intermediate lens system in the light beam passing through the intermediate lens system and the objective lens system to the record medium is cancelled at the objective lens system.

Dependencies are inferred from the claim text.