Importance

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Abstract

The present invention is directed to a system and method for radiometric calibration of spectroscopy equipment utilized in fault detection and process monitoring. Initially, a reference spectrograph is calibrated to a local primary standard (a calibrated light source with known spectral intensities and traceable to a reference standard). Other spectrographs are then calibrated from the reference spectrograph rather than the local primary calibration standard. This is accomplished by viewing a light source with both the reference spectrograph and the spectrograph to be calibrated. The output from the spectrograph to be calibrated is compared to the output of the reference spectrograph and then adjusted to match that output. The present calibration process can be performed in two stages, the first with the spectrographs calibrated to the reference spectrograph and then are fine tuned to a narrow band light source at the plasma chamber. Alternatively, the reference spectrograph can be calibrated to the local primary standard while optically coupled to the plasma chamber. There, the local primary standard calibration light source is temporarily positioned within the plasma chamber, or in a light chamber disposed along the interior of the chamber for calibrating the reference spectrograph. Other spectrographs can be calibrated to the reference spectrograph while coupled to the plasma chamber with the local primary standard calibration light source, thereby calibrating every component in the entire optical path to the reference spectrograph.

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First Claim