Abstract: The pixel position-to-wavelength calibration function of film measurement devices such as spectroscopic ellipsometers and spectroreflectometers may shift due to temperature and humidity changes and mechanical factors. One or more wavelength markers provided by the light source or reference sample may be used to correct the calibration function. The pixel positions of one or more persistent wavelength markers are noted during the calibration process and the current positions of such markers are again noted to account for shifts due to various factors to correct the calibration function.

Abstract: A method for calibrating an ellipsometer, and an ellipsometer including a processor programmed to control the analyzer, polarizer, and other ellipsometer components, and to process the data measured by the ellipsometer to perform the calibration method automatically. Where the ellipsometer's polarizer rotates and the analyzer remains fixed during measurement, the method determines coarse approximations of values A.sub.0 and P.sub.0, and then processes reflectivity data obtained at two or more analyzer angles to determine refined approximations of the values A.sub.0 and P.sub.0, where P.sub.0 is the angle of the polarizer's optical axis at an initial time, and A.sub.0 is the offset of the actual orientation angle of the analyzer from a nominal analyzer angle. Preferably the ellipsometer is a spectroscopic ellipsometer, the reflectivity data determine a tan.psi. spectrum and a cos.DELTA. spectrum for each of the analyzer angles, and the coarse approximations of A.sub.0 and P.sub.