Optical interferometry

The field of optical and infrared (IR) interferometry has seen rapid techni cal and scientific progress over the past few years. A number of instrument s capable of precise visibility measurements have been built, and closure-p hase imaging with multitelescope arrays has been demonstrated. Astronomical results from these instruments include measurements of stellar diameters a nd their wavelength dependence, limb darkening, stellar surface structure, and distances of Cepheids and of Nova Cygni 1992. Precise stellar masses ha ve been obtained from interferometric observations of spectroscopic binarie s, and circumstellar disks and shells have been resolved. Searches for subs tellar companions and extrasolar planets with interferometric astrometry wi ll begin soon. Nulling interferometry will enable studies of exozodiacal di sks from the ground and the detection and characterization of terrestrial e xtrasolar planets from space. These developments are reviewed, as well as p rogress in some key technological areas.