Patent ID: 7215422

Claim:
A spectrometer assembly comprising a light source emitting light with a continuous wavelength spectrum, pre-monochromator means comprising an entrance slit, means for directing a light beam from said continuous spectrum light source onto said entrance slit of said pre-monochromator means, echelle spectrometer means comprising a blazed diffraction grating with grooves and defining an exit plane, in which said echelle spectrometer means in operation generates overlapping echelle spectra of different orders, each of said spectra having a free spectral range with a bandwidth, said blazed diffraction grating defining an order of an echelle spectrum, the center wavelength of which has a maximum blaze effectiveness, said pre-monochromator means further comprising means for spectrally dispersing light from said light beam from said continuous spectrum light source with a degree of linear dispersion and means for selecting, from said dispersed light, a spectral interval having a bandwidth, which is not larger than said bandwidth of said free spectral range of said maximum effectiveness spectrum order and has an intensity versus wavelength profile, said profile defining a wavelength characteristic of said profile, an intermediate slit assembly between said pre-monochromator means and said echelle spectrometer means, said intermediate slit means having a slit width and being arranged to form an exit slit of said pre-monochromator means and an entrance slit of said echelle spectrometer means, said pre-monochromator being adapted to generate a monochromatic image of said pre-monochromator entrance slit on said intermediate slit, said slit width of said intermediate slit assembly being larger than said monochromatic image of said pre-monochromator entrance slit, and spatially resolving detector means located in said exit plane for detecting said spectrum generated by said echelle spectrometer means and defining a reference position thereon, calibrating means for calibrating said pre-monochromator to bring said profile characteristic wavelength to coincidence with said reference position.