1 August 1990 Experimental recovery of 2-D spatial-coherence modulus and phase using fourth-order correlation interferometry
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We present the first experimental results of recovery of the 2-D spatial coherence modulus and phase using fourth order correlation interferometry (FOCI). The technique, a generalization of intensity interferometry and laser speckle correlography, measures the correlation (I(x)A*(x+A)A(x+A+c)), where 1(x) and A*(x+E)A(x+A+e) are measured with separate, unconnected apertures. The result of the measurement is t*(A)i(+c), a cross-product of the spatial coherence factor that is analogous to the Knox-Thompson cross-spectrum in astronomical speckle imaging. The technique has applicability when the coherence function must be measured over distances A which are larger than the diameter D >> XE of the largest diffraction limited optic or amplitude interferometer and the field is a circular complex Gaussian random variable. An experiment is described which makes the correlation measurement on a series of laser speckle patterns. 1(x) and A*(x+A)A(x+A+e) are obtained from the focal spots of an array of lenslets. The measured coherence function is shown to agree with the expected value. The intensity image, given by the Fourier transform of the coherence function, is calculated and gives good agreement with the experiment target. The usefulness of the technique is discussed.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Steven M. Ebstein, Steven M. Ebstein, } "Experimental recovery of 2-D spatial-coherence modulus and phase using fourth-order correlation interferometry", Proc. SPIE 1237, Amplitude and Intensity Spatial Interferometry, (1 August 1990); doi: 10.1117/12.19325; https://doi.org/10.1117/12.19325

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