Manufacture of optical data storage discs

A method of manufacturing an optical data storage disk is disclosed in which two similar disk members are secured in back-to-back relationship, which comprises the steps of: (a) positioning the disk members in the desired back-to-back relationship and concentric with one another; (b) effecting a first bond between the disk members close to their centres; and (c) effecting a second bond between the disk members at or close to their periphery, at least one of said first and second bonds being effected by means of a resilient bonding arrangement, whereby the tendency of the edges of the disk to vibrate is reduced. Preferably, the disks are located concentrically prior to effecting said first bond by a method comprising: holding the disks mutually parallel in opposed relationship and spaced apart by a distance in the range 0.2 to 1.5 millimeters; directing a coherent or non-coherent beam of light uniformly over a predermined area of the disks where each of the disks carries regularly arranged grooves the pitch (period) of which is in the range 15 to 50 microns; and observing the intensity of light transmitted through both disks at three or more locations which are equidistant from the axis of location of the disks; and adjusting the relative position of the disks about said axis of location until the measured intensities at each of the observing stations are the same.