Tunable Fabry-Perot filter for determining gas concentration

摘要

The invention provides a filter of the Fabry-Perot interferometer type for electromagnetic radiation having spectral density that is modified by a gas. The filter comprises a body which is transparent to said electromagnetic radiation, at least in its part through which the radiation passes. Said part comprises at least two portions possessing two facing surfaces that are mutually parallel and substantially plane. A "first" one of said portions is movable in a direction that is substantially perpendicular to the pair of facing surfaces. The filter further comprises: means for moving said facing surfaces between two extreme positions under the action of an electromagnetic field, and means for limiting adhesion between said surfaces in at least one of said positions in which said surfaces are at a distance apart which is small compared with the mean wavelength of the radiation passing through them.