Coherent image fringe contrast measurement with sensing arrays

Two methods are described for measuring interferometric fringe contrast with sensing arrays. The absence of air turbulence allows contrast to be determined quickly by measuring the intensity of the fringe pattern at phases 90° apart. The presence of turbulence requires that the peak-to-peak fringe intensity be found by sampling the fringes as they are scanned across the array. An analysis is presented showing the relation between maximum error in fringe contrast measurement and the number of samples taken. Experimental results are presented which show the effect of turbulence on fringe contrast measurement.