Holographic storage of binary-coded information - uses phase modulation of object wave for recording

摘要

The process is such that the mean intensity of radiation, during the recording of a hologram with binary-coded information, is independent of the frequency of occurrence of 1's in the information. The latter is superimposed during recording on the constant amplitude object wave in the form of a spatial phase modulation, by means of a transparent plate arranged between the coherent light source and the hologram carrier plate. Separate binary bits, whether 0 or 1, are expressed by different discrete phase values of the wave. When the hologram is read, the phase differences are first converted into amplitude stages.