holography in which an array of overlapping holograms is recorded or reconstructed in a recording medium , holograms being produced by interference of a reference beam and a signal beam , in which the reference beam is a phase beam which consists essentially of a multitude of rays of varying angle of incidence and non - uniform phase , in which the process comprises changing the orientation of the phase beam for recording or reconstructing different holograms , wherein phase beam orientation is changed relative to the medium while maintaining the medium stationary in order to enable recording or reconstruction of individual holograms at a given location of the medium .