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“Derived Spectra” Software Tools for Detecting Spatial and Spectral Features in Spectrum Images

Dale E. Newbury and David S. Bright

National Institute of Standards and Technology, Gaithersburg, Maryland, USA

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Summary: A spectrum image is recorded as an x-y array of beam locations at each of which a spectrum of radiation is recorded as stimulated by the beam. The large database or “datacube” that results from a single image presents a significant challenge to the analyst to recover information efficiently, especially in the case where a true unknown is examined. This paper describes a class of “derived spectra” software tools that can aid the analyst in recognizing both common and rare features within the datacube. A derived spectrum tool creates a spectrum-like display (intensity vs. channel number) in which the intensity (e.g., x-ray counts) at a particular channel (e.g., x-ray photon energy) is calculated from all of or a subset of the pixel intensities measured for that channel. Derived spectra tools considered include the SUM, MAXIMUM PIXEL, RUNNING SUM, and RUNNING MAXIMUM. The SUM-derived spectrum is useful for recognizing common features of the datacube, while the MAXIMUM PIXEL-and RUNNING MAXIMUM-derived spectra can locate rare, unanticipated features, which may occur as infrequently as being present at a single pixel in the original datacube.

Key words: datacube, derived spectrum, microbeam analysis, scanned probe imaging, spectrum image, x-ray mapping

PACS: 07.79.-v