 The theory of the triple correlation was first investigated by statisticians examining the cumulant structure of non-Gaussian random processes.It was also independently studied by physicists as a tool for spectroscopy of laser beams.Hideya Gamo in 1963 described an apparatus for measuring the triple correlation of a laser beam, and also showed how phase information can be recovered from the real part of the bispectrum—up to sign reversal and linear offset.