LIGHT BEAM FOCUS POSITIONING MECHANISM OF OPTICAL RECORDING/REPRODUCING APPARATUS, AND METHOD THEREOF

摘要

PROBLEM TO BE SOLVED: To provide a light beam focus positioning mechanism of an optical recording/reproducing apparatus and a method thereof, which even when a light beam is spatially phase-modulated at random, can accurately position a focal position of the light beam on a reference surface.SOLUTION: The light beam focus positioning mechanism of the optical recording/reproducing apparatus includes: a light emitting device; a light converging optical system for converging a light beam on a reference surface of an optical recording medium; an optical phase modulator for phase-modulating a partial beam of a light beam passed through a predetermined cell; a light transmission control element capable of blocking a partial beam of the light beam in an optical cell; a light guide optical system for guiding diffraction light from a one-dimensional periodic structure and reference surface reflected light or the diffraction light and transmitted reference light into a far field in which both the light components are overlapped to each other; an optical detector installed in the far field; a signal generation part for generating a focal error signal of the light beam; and a focal position control part for controlling a position of a focus of the light beam in a depth direction to the reference surface on the basis of the focal error signal.