Phase Interferometry

Abstract

In the preceding chapter, we have discussed the astrometric information that can be derived from the measurement of the intensity of fringes as a func-tion either of time or of the distance between the optical axes of the two telescopes. We have seen that the analysis of these measurements provides parameters that pertain to the light distribution within a few seconds of arc in the sky. The optical layout was used to maintain the central fringe in front of a photomultiplier but the actual variations of the optical path to a fixed point were not considered. In this chapter, we shall describe what additional information can be deduced from this parameter and see that interferometry is a remarkable tool for global astrometry. It is called phase interferometry because the phase and not only the amplitude of the fringe pattern is observed.