A FILTER

摘要

The present invention relates to a controlled interference polarization spectrometer for determining the concentration of a substance within a sample. The spectrometer includes first and second filters for filtering first and second portions of radiation transmitted by the sample. The filters having a number of pass bands at wavelengths corresponding to absorption peaks in the absorption spectrum of the substance to be detected, and are responsive to an applied signal to modulate the wavelengths of the pass bands in respective first and second directions. A detector detects the filtered radiation and determines the difference in the maximum and the minimum intensities of the radiation transmitted by the sample to thereby determine the concentration of the substance.