Abstract: A focusing interferometer, wherein the focusing and orientation of the different mirrors of the interferometer have been successfully facilitated by combining the focusing mirror and the collimating mirror to provide a single spherical mirror surface and by reversing the paths of light that start from the beam splitter by assembly of mirrors which are arranged back-to-back to reflect to opposite directions such that their optical axes join, each of the mirrors including three flat mirror surfaces that are perpendicular to one another and are arranged to reflect to the direction of the point where the normals of the mirror surfaces intersect.

Abstract: A scanning interferometer includes an optical arrangement. The optical arrangement therein includes two mirrors diverting the travel direction of light, arranged back-to-back such that they reflect to opposite directions and that their optical axes join. The mirrors are arranged in a mounting, which is arranged to move back and forth by a moving mechanism. The mounting includes a base element supported by the body of the interferometer, at least two support arms connected with the base element at their first ends via first bending points and a mounting element connected with the second ends of the support arms via second bending points, the mirrors being fastened to the mounting element. The mechanism moving the mounting includes a assembly generating a linear back-and-forth movement and a transmission mechanism for converting the back-and-forth movement to a back-and-forth movement of the mounting element.

Abstract: A procedure for enhancing the resolution of spectral data, in which the Fourier self-deconvolution method FSD is used to produce from the input spectrum a data set in an interval 0-L.sub.t, the maximum entropy method MEM is used to compute prediction error filter coefficients {a.sub.k } from this data, and by the linear prediction method LP, using coefficients {a.sub.k } and data points 0 to M. Data are predicted in the interferogram I(x) beyond L.sub.t, whereby output spectrum maximum line narrowing with minimum distortion is achieved.

Abstract: Procedures are provided for analyzing multicomponent FT-IR spectra for unknown mixtures of gases. In the analysis, the FT-IR spectrum is measured for the particular unknown mixture of gases to be analyzed. The operations of the multicomponent analysis are divided into three different levels so that the most laborious operations, which have to be performed very seldom or only once, are on the highest level. Rapid calculation operations to be performed in connection with each spectrum analysis are on the lowest level. The levels are as follows: 1) Forming a spectrum library; 2) Introducing a new basis and adding a new vector to the old basis; and 3) Individual analysis. Variances, error limits, and residual spectrums are calculated in the analysis. A windowing procedure is followed to reject spectrum portions where the transmittance approaches zero or which do not contain real information for some other reason.