Verfahren und Anordnung zur Bestimmung und Normierung der Intensitaet eines Messsignals, insbesondere bei der Modulations-Laser-Absorptionsspektroskopie

The invention relates to a process and an arrangement which helps to perform a determination and normalization of the intensity of a measuring signal, in particular for modulation absorption spectroscopy or interferometry, whereby only a single measuring detector is required and no otherwise necessary reference channel is required. By means of on-line normalization and the use of a frequency modulation method, a diode laser is modulated in such a way that at least one discrete frequency is superimposed on the former. The frequency-modulated laser radiation at its original intensity is then subjected to an intensity attenuation in an absorption measuring cell, said attenuation being determined by means of a phase-sensitive detector. According to the invention, a residual amplitude of the modulation signal is determined at the output of a single detector, whereby said residual amplitude represents a measure of the original intensity. The residual amplitude value can then be used for know n intensity normalization methods.