Experimental measurement of coherence by a single-pixel detector

We report a non-interferometric technique for experimentally measuring the complex coherence function. This is implemented using a reference-free, in-line configuration with structured illumination and measuring a temporally averaged intensity by a single-pixel detector (SPD). The two-dimensional (2D) distribution of the complex coherence is measured by evaluating intensity correlations for three-step phase-shifted structured patterns with varying spatial frequencies. This technique provides a robust and stable means to quantitatively measure the complex coherence function. Experimental demonstrations are performed by measuring the complex coherence function of three different incoherent sources in the far field.