Fabry-Perot interferometers with electronic determination of Doppler line widths.

It is shown that, if Fabry-Perot interferometers are to be used for the measurement of doppler widths of emission lines, exact knowledge of the plate reflectivity is required so that synthetic profiles may be calculated. If hyperfine structure or isotope structure is present, the data reduction may be tedious. It is shown that electronic analysis of the signal generated by a scanning interferometer will lead directly to a displayed measurement of the doppler temperature, and that the effects of hyperfine structure, isotope structure, Lorentz broadening, nonflatness of the plates and the finite size of the scanning aperture may all be compensated exactly. The performance in marginal circumstances has been calculated using the derived equations, and the system is shown to be capable of high accuracy.