Pyrometry for substrate processing

The substrate processing system includes a processing chamber, in order to measure a pedestal for supporting a substrate disposed within the processing chamber, the radiation resulting from the portion of the substantially pedestal or substrate, coupled to the processing chamber and including and optical pyrometry assembly. Optical pyrometry assembly further includes a photodetector and the photodetector. Optical pyrometry assembly receives a portion of the emitted light, the temperature of the substrate is determined from the intensity in the vicinity of at least one wavelength of a portion of the emitted light. Method of measuring the temperature of the substrate during processing, by disposing the light guide near the part of the pedestal for supporting a substrate or pedestal, so that the end of the light conductor receives light from a portion of the pedestal or substrate to, to shield the end of the optical conductor from stray light to reduce the contamination of the end of the optical conductor, purging the end of the optical conductor with a gas, emitted from the pedestal, received by the light conductor detecting the a part of the light, and the portion of the light emitted from the pedestal or substrate, includes determining the temperature of the substrate from the intensity in the vicinity of at least one wavelength.