Multidetector intensity interferometers

The intensity fluctuations of incoherent radiation are used to determine the position of sources with respect to a detector system. For electromagnetic radiation the system uses square‐law detectors and for acoustic waves the detector output is squared before being processed. The theory is developed for n detectors and the results are applied to two‐, three‐, and four‐detector arrangements. The two‐detector intensity inteferometer measures the square of the first‐order correlation function and can determine the angular size of a source. The three‐detector intensity interferometer yields two coordinates of the location of a source, and a modified version involving only one detector functions as a Fourier transform spectrometer. It measures the first‐order correlation function and thus can be used to obtain the spectrum of the source. The four‐detector intensity interferometer can simultaneously determine the three‐dimensional coordinates of several sources. The operation of several acoustic multidetector i...