Optical pickup using optically variable iris

Abstract

An optical pickup includes a variable iris having a numerical aperture is adjusted according to wavelength of light and can be compatibly used for discs having respectively different specifications. The optical pickup includes a plurality of laser sources respectively emitting light of different wavelengths, an objective lens for focusing the light emitted from the laser sources into an optical spot optimized to each information recording surface of the plurality of discs, at least one photo detector for detecting the light reflected from the information recording surfaces of the corresponding discs where the optical spot is focused and passed through the objective lens, an optical element for adjusting an optical path so that the light emitted from the laser sources is directed toward the objective lens and the light emitted from the objective lens is directed toward the at least one photo detector, and a variable iris coupled between the laser sources and the objective lens, selectively operating according to the wavelength. The optical pickup can be compatibly used for discs having respectively different specifications irrespective of the thicknesses of the discs. The variable iris selectively operates in the case that light of two or more wavelengths is used, to thereby provide an effect of accomplishing an optimal optical spot on the discs.