Apparatus for spectral analysis of a broad beam of radiation using a dispersive element interposed between two modulators

摘要

The present spectrometer features two modulators 11, 11' disposed one on either side of a dispersive member 19 which produces wavelength dependent deflections &agr; of the various spectral components in the radiation. In other words the precise angle of deflection &agr; is a function of wavelength. The dispersive element 19 is conveniently positioned between two lenses 26 which form a telecentric system with a magnification of one. The lens system is used to produce an image of the first modulator on the second modulator. Each of the modulators is preferably a grating with a linearly varying grating constant so that the modulators, which move in opposite directions f,f' at constant speed subject the incident radiation to a position dependent modulation. The radiation emerging from the second modulator 11' falls onto a photodetector 13. The arrangement is such that the output signal from the detector 13 contains a number of different frequencies each of which is characteristic of one of the particular spectral components. These frequencies, and thus the information on the individual spectral components can be readily separated using respective band pass filters 17. sub.I, 17.sub.II, 17.sub.III.