Micromachined optical tunable filter for domestic gas sensors

After a review of the different existing optical gas sensors using broadband emitters, we present a new component (tunable optical filter) that can provide autocalibration of gas sensors and thus improve their long term stability. This device is a micromachined Silicon differential pressure sensor made of three wafers separated by two air gaps. We show that it can be applied as an electrically tunable Fabry-Perot filter and used for the detection of gases having spectral absorption bands in the infrared domain of wavelengths between 2 and 8 mu m, Its high temperature stability over 160 degrees C is reported. The suitability of this filter and related Silicon micromachined components (microphones, accelerometers...) for hydrocarbons and carbon monoxide domestic gas sensors is discussed. (C) 1997 Elsevier Science S.A.