Interferometric analyzer for multiple substance detection

Interferometric analyzer for the detection of substances having a structured absorption spectrum such as a periodic or quasiperiodic absorption line pattern, within a gas blend, and comprising a source of radiation for directing radiation into a radiation path that includes a container, cell or the like which contains the substances to be detected, the path further including a Fabry Perot element the thickness of which is determinative for the transmission interference lines, and a detector downstream from the Fabry Perot element, the improvement comprising:

• means for controlling the thickness of the Fabry Perot element such that the spacing between the transmission lines of the interference corresponds to spacing of absorption line of different substances for different absorption bands of these substances;
• and
• a disperging element positioned in the radiation path for selecting a respective spectral region as far as a particular substance is concerned by means of the controlled disperging element.