Heterodyned holographic spectroscopy

In holographic spectroscopy an image of an interference pattern is projected onto a detector and transformed back to the input spectrum. The general characteristics are similar to those of Fourier transform spectroscopy, but the spectrum is obtained without scanning. In the heterodyned arrangement one or more diffraction gratings are used so that high-resolution spectra can be recorded without a corresponding increase in the recording density. The technique offers interesting possibilities, but is not without difficulties. The purpose of this paper is to review recent developments, especially in astronomical applications, to describe the theoretical background to typical problems such as coherence losses, and to discuss the extent to which these can be solved in practical instrumentation.