Changes in the image contrast during recording of holograms in nonlinear media with local response

It is shown that the zero frequency of the spatial spectrum of an image can be filtered off by transient pumping of the intensity of this frequency to the reference wave and simultaneous amplification of the high-frequency components in the course of recording of a dynamic hologram in a nonlinear medium with local response. Experimental results are reported showing that the contrast of amplitude transparencies can be improved by recording holograms in iron-activated lithium niobate crystals.