A novel approach for precise interferometric measurements of small transient phase shift of any speckled wave is discussed. The technique is based on a recently discovered polarization self-modulation effect in photorefractive crystals. The essence of this effect is that any intensity pattern is recorded in the form of the space-charge field inside the crystal. Then the same pattern propagates in the self-induced spatially-non-uniform electric field. As a result, the polarization state of the transmitted pattern becomes spatially modulated. Any pattern displacement results in change of the transmitted polarization distribution due to the linear electrooptic effect. Polarization modulation is readily converted into amplitude modulation by installation of a polarization analyzer after the crystal. In the proposed method, the crystal operates as a self-induced electrooptic modulator. The model of the polarization self-modulation effect is presented. It is shown that the signal-to-noise ratio of the proposed technique approaches to that of the ideal homodyne interferometer. Comparison of the proposed method with two- wave mixing technique is given.