A spatial coherence analysis of the light scattering in turbid media, illuminated by a laser source, is presented. Classical degree of coherence modulus measurements require the determination of a fringe pattern visibility. This measurement needs complex algorithms for detecting the fringes minima and maxima on the digitized image. We describe here an easy method to extract the average visibility from the digitized fringe pattern histogram. In the first part, we present the mathematical basis of the method which is obtained from the classical intensity distribution of an interference pattern. This method requires slow spatial variations fringes size compared with the spatial carried frequency. Furthermore, the intensity of the two arms of the interferometer must be equal. If these conditions are assumed, we can easily extract the degree of spatial coherence modulus directly from the histogram of the fringe pattern. The efficiency of the method has been proved using computed interference fringes. In the second part, we apply the histogram analysis on real fringe interference measured in turbid media (seawater). The estimated spatial coherence magnitude is compared with results obtained by classical method. This comparison shows the validity of the histogram method. In conclusion a discussion is made about the advantages and the limits of the proposed method.
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