Beam-analyzer for optical storage device.

摘要

An optical analyzer for determining changes of the polarization plane in a light beam (4) comprises a substrate (20) supporting a photo-detector array (21) and a system of imaging mirrors (22 - 24) underneath a parallel plate (25) of high quality optical glass. The lower surface of the glass plate is covered by a system (26) of dielectric multilayers which acts as a polarizing beam splitter over a large range of angles of incidence. The optical beam (4) enters the analyzer through the glass plate to impinge under an oblique angle of incidence on a first mirror (24) which rotates the plane of polarization in the beam by 45 DEG with respect to the polarizing beam splitter, which then generates two beams partial (202,203) to be eventually directed to photo-detector array (21). The beam analyzer is used in magneto-optical storage system to extract an information signal and to generate servo control signals for the focus and track positions of the beam. The tilted first mirror may have circular or stripe geometry and be integrally formed within the substrate (20). The multilayer polarizing beam splitter system comprises two stacks of layers separated by an intermediate layer and covered by a thick dielectric layer.