AN INFORMATION MEDIUM

摘要

An information medium consists of an essentially circular or polygonal disk having at least two pairs of sides parallel to one another which have the same distance to one another in each pair. To reliably read stored data from such an information medium at high speed, a hologram is disposed on at least one side of the disk at its centre or at the intersection of two crossing symmetry lines which may be reconstructed with a reference beam incident to the side at a right angle to a pattern consisting of essentially concentric circles, with the reference beam forming the axis of said pattern.