Analysis of light source

Sensor Review

ISSN: 0260-2288

Article publication date: 1 March 2000



(2000), "Analysis of light source", Sensor Review, Vol. 20 No. 1.



Emerald Group Publishing Limited

Copyright © 2000, MCB UP Limited

Analysis of light source

Keywords Spectral analysis, Image processing, Dispersions

Inventor: Peter Lindblom (SE)

Patent Number: US5859702

Publication date: 12 January 1999

Title: Apparatus for carrying out spectral analysis of an optical light source using image detection and separation of spectral orders

Diffraction gratings are very effective optical elements for carrying out wavelength dispersion. However, they have the disadvantage that spectra from several spectral orders result in ambiguities in the analysis of a spectrum. The purpose of this invention is to eliminate this and other drawbacks. It comprises an apparatus for carrying out spectral analysis of optical radiation emitted from a light source, comprising a spectral detector with an entrance aperture for the radiation from a light source, a first means for optical imaging, a diffraction grating for wavelength dispersion of the radiation, an order sorting means for separation of the spectral orders from the diffraction grating, and for dispersion of the radiation in a direction orthogonal to the direction of the diffraction grating, a second means for optical imaging, and detecting means for recording the spectrum of the light source, the spectrum being divided into spectral orders by the order sorting means. Among other things, the invention makes the order sorter able to separate the different order spectra unambiguously and with a substantially uniform distribution on the detector, and simultaneously to eliminate or reduce the astigmatic optical aberration. Another optical aberration, which causes a broadening of the spectral image of the entrance aperture and consequently a reduction of the spectral resolution, namely coma, is eliminated or reduced through the present invention. Furthermore, the invention makes it possible to optimize the use of the surface of the detector unit.