Abstract: An instrument for determining the vergence of a beam in the infrared spectrum, particularly a laser beam, includes a wedged shear plate of suitable infrared transmissive material; a flat plate detector; parallel, spaced bars or strips of bolometric material, such as bismuth, applied to the plate in a pattern so as to match the "null" interferometric modulation from the wedged shear plate and alternately electrically connected to provide a pair of parallel electrical circuits providing signals for comparison; means for rotating and tilting the detector to provide "null" readout from the compared signals and means for directly measuring the vergence of the beam by a measure of the amount of rotation and tilt required to achieve a "null" readout.

Abstract: A bolometer for the detection of radiation includes a thin film of bismuth having electrical contacts formed at its outer boundary edge whereby electrical signals, as a function of the X and Y positions of input radiation, appear as output signals at the contacts. A measure of the radiant energy striking the detector is used to ratio X and Y to make the instrument insensitive to changes in power input.