Spectral resolution improvement technique for a spectrograph mounting a discrete array detector

Abstract

A new technique has been developed for improving the spectral resolution of spectrographs mounting discrete array detectors. The basic idea is to acquire various spectroscopic images each spectrally displaced on the detector by a fraction of the pixel and to apply suitable numerical procedures in order to extract a spectral profile with subpixel resolution. This technique has been applied to a vacuum spectrograph adopting the Johnson-Onaka configuration. The dispersion element is a concave toroidal grating which can rotate around a pivot axis displaced from its vertex, in order to keep always a good spectral focus on the detector. The latter is a multi-anode microchannel-plate array (MAMA), operating in photon counting mode. Several stigmatic images of the HI Ly(alpha) line at 1216 angstrom emitted by a D2 lamp have been acquired for various rotation of the grating. The results of the application of this new technique and the numerical algorithm are presented and discussed in terms of potentialities and limitations due to signal to noise (S/N) ratio and intrinsic spectral broadening of the signals.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.