The Navy Prototype Optical Interferometer contains two major subarrays: one for imaging the surface of stars, the other for measuring the precise positions of bright stars. In order to image the surface of stars, six 50 cm elements which can be reconfigured to sample many spatial frequencies using 32 spectral channels equally spaced in wavenumber between 450 and 850 nanometers. The imaging array elements are distributed on a 'Y' with a maximum spacing for imaging of 437 m, yielding a spatial resolution of 0.2 mas. The positions of stars will be measured using four fixed 50 cm siderostats with element spacings from 19 to 38 meters. The delay line compensation and beam paths are in vacuum to eliminate the effects of atmospheric dispersion. The astrometric goal is an accuracy of 2 mas over wide angles.