Optical pick-up device

摘要

There is provided an optical pick-up device capable of eliminating a spherical aberration due to a thickness error of an optical disc. The optical pick-up device includes a convex lens having a flat surface opposed to a surface of an optical recording medium, and having a predetermined refractive index, and an objective lens disposed such that the convex lens is interposed between said optical recording medium and the objective lens. A position-detecting means detects a position relation between the light-incident surface of the optical recording medium and the flat surface of the convex lens, based on first and second detection signals. A drive means drives the convex lens along an optical axis thereof such that the convex lens is caused to move in the opposite directions toward the optical recording medium or the objective lens, whereby a distance between the light-incident surface of the optical recording medium and the flat surface of the convex lens is controlled based on the first and second detection signals.