[en] The application of double exposure fractional fringe holographic interferometry to measurements of electron density in a plasma generated by irradiation of a freely falling pellet of solid deuterium with a focused CO₂ laser pulse is discussed. A particularly simple technique is used for processing and reconstructing the holograms and this is described in detail. A summary and discussion of the results is included with the emphasis on the observed evolution of the deuterium plasma over the duration of the laser irradiation. (author)