Magneto-optical data recording and reproducing device

Abstract

A magneto-optical data recording and reproducing device for storing data in a data memory medium which applies modulation to a plane of polarization, erasing data therefrom and reproducing data stored therein, comprises a light source for emitting a light beam with linear polarization, a light spot forming means for condensing the light beam emitted from the light source and forming a light spot on the data memory medium, a beam splitting means, located between the light source and the light spot forming means, to which reflected light beams from the data memory medium are applied and splitted, a beam detecting prism, to which light beams splitted by the beam splitting means are applied, providing the polarizing function that a predetermined first pencil of light beam with linear polarization is reflected while a second pencil of light beam with linear polarization crossing the first pencil at right angles is transmitted, a beam splitting prism, being located near or adhered to the beam detecting prism, for splitting the second pencil of light beam with linear polarization transmitted through the beam detecting prism into two subpencils with approximately the same quantity of light, reflecting the splitted subpencils and then re-allying them to the beam detecting prism to form two optical axes extending along approximately the same direction as that of the first pencil of light beam with linear polarization, at least one or more photo detector to which a plurality of light beams having passed through the beam detecting prism and the beam splitting prism are applied, a data retrieval unit for retrieving data in the data memory medium according to output of the photo detector, a tracking servo unit to which a tracking error signal picked up by the output of the beam detector is applied, and a driving means for driving at least the light spot forming means in response to an output signal from the tracking servo unit.