Conditions of pressure scanning of a Fabry-Perot interferometer over a wide spectrum range.

The association of a Michelson interferometer and a Fabry-Perot etalon enables the control of the displacement of the peaks of Fabry-Perot transmittance by pressure scanning through Michelson fringes counting. Assuming the variations of the refractive index of gas as a function of wavenumber, pressure, and temperature are known, we show that it is perfectly possible to compute the number of fringes to shift in order to position a chosen peak of Fabry-Perot transmittance for any point in the spectrum. These possibilities enable us to build a real spectrometer whose accuracy is better than 0.05 cm(-1) in the whole visible range.