Abstract: The optical head device includes a laser light source, a beam splitter for reflecting light emitted from the laser light source, a converging lens for converging light reflected from the beam splitter as a minute beam spot on a recording surface of an optical disk medium, a photo-detector for receiving modulated reflected light from the recording surface of the optical disk medium through the converging lens and the beam splitter, and a diffraction grating disposed between the laser light source and the beam splitter. The device is featured by the provision of a variable aperture element which is disposed between the converging lens and the beam splitter and which is capable of controlling the transmission and blocking of the light depending on the polarization directions. The arrangement enables the reproduction of the data recorded in optical disk media having different thicknesses by a single objective lens.