Interferometric Spectral Imaging in the Visible and Near-Infrared Regions

We present experimental results of an interferometric method called the Fourier transform spectral imaging[1], The method is based on the alterations[2] of coherence function during propagation in free space. We assume that an incoherent light source (object) illuminates an observing site and that the optical wave field around this site consists of an ensemble of plane waves with uncorrelated amplitudes. This is a reasonable assumption when the observation volume is small or an appropriate transform lens is placed between the object and observation area. The theory predicts that three-dimensional (3-D) Fourier transformation of the 3-D spatial coherence function of the optical wave field gives the 3-D energy density function, a function of a 3-D spatial frequency or a wave vector, associated with the object[1]. Under the assumption stated above, the wave vectors assign particular directions of propagation and wavelengths of the plane waves that emanate from the particular positions in the object. Thus, the density function fully specifies the spectral image information of the object, i.e. the spatial distribution of radiation and the spectral contents comprising the radiation. Since the present method is an extension of Fourier spectroscopy to imaging spectroscopy[1], it inherits the desirable properties of the multiplex and throughput advantages.