US Patent 7180844 Holographic disc recording system

A holographic disc recording system for recording, in the form of holograms, information stored on a source disc onto a target disc includes a conical beam shaper which transforms a reference beam into a conical beam having a substantially cylindrically symmetrical shape and including light rays which travel along lines which intersect a beam axis of the conical beam at substantially the same angle with respect to the beam axis. The conical beam is incident on the target disc while the beam axis of the conical beam substantially coincides with a central axis of the target disc, so that substantially all of the light rays of the conical beam are incident on the target disc at substantially the same angle.