HETERODYNED HOLOGRAPHIC SPECTROSCOPY

In holographic spectroscopy an image of an interference pattern is pro jected onto a detector and transformed back to the input spectrum. The general characteristics are similar to those of Fourier transform spe ctroscopy, but the spectrum is obtained without scanning. In the heter odyned arrangement one or more diffraction gratings are used so that h igh-resolution spectra can be recorded without a corresponding increas e in the recording density. The technique offers interesting possibili ties, 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 coh erence losses, and to discuss the extent to which these can be solved in practical instrumentation.