Coherent integration results from the NPOI

In this paper we will discuss the current status of coherent integration with the Navy Prototype Optical Interferometer (NPOI). Coherent integration relies on being able to phase reference interferometric measurements, which in turn relies on making measurements at multiple wavelengths. We first discuss the generalized group-delay approach, then the meaning of the resulting complex visibilities and then demonstrate how coherent integration can be used to perform very precision measurement of stellar diameters. The phase of the complex visibility is particularly attractive as a data product because it is not biased in the same way as visibility amplitudes. We discuss the relative SNR of triple-product phases and single-baseline phases. We then demonstrate how singlebaseline phases can be used to make accurate measurements of magnitude differences and separations of binary stars.