DIRECT, UNAMBIGUOUS DISPLAY OF PHASE-DIFFERENCE USING OPTICAL FEEDBACK TO A PHASE-ONLY SPATIAL LIGHT-MODULATOR

Unambiguous mapping of two-dimensional path-difference distributions i n two-beam interferometers has heretofore required the application of techniques such as phase-shifting or heterodyning, because of the cosi nusoidal fringe intensity profile. These techniques require considerab le data processing, and sometimes the detector must also be scanned po int-by-point over the fringe field making it difficult to obtain realt ime display of the phase distribution. We describe a novel technique, in which the output intensity distribution of a two-beam interferomete r is fed back to an optically addressable phase-only spatial light mod ulator in one arm of the interferometer, which gives real-time unambig uous display of the path-difference distribution in the interferometer . The interference fringes have a ''sawtooth'' intensity profile with a nearly linear relationship between output intensity and phase.