Patent ID: 8094313
Filing Date: 2012-01-10
Classification: G01J,G01N

Abstract:
1. A wavelength modulation spectroscopy method comprising: periodically sweeping a wavelength of a beam of light from a light source according to a sweep function; directing the beam of light through a single optical path to pass through a sample of gas being analyzed to determine a concentration of at least one component of the gas; alternating between a first modulating and a second modulating of the beam of light passing through the sample of gas, wherein the first modulating comprises modulating the wavelength of the beam of light with a modulation signal having a modulation frequency at a first frequency value, and wherein the second modulating comprises modulating an intensity of the beam of light with a burst signal having a burst frequency at a frequency value different than the first frequency value, wherein an N-th harmonic of the burst frequency has a frequency value equal to a frequency value of an M-th harmonic of the modulation frequency, wherein N and M are respective positive integer numbers; disposing in the single optical path a detector to receive the beam of light having passed through the sample of gas and generating a detector output in response to the received beam of light, wherein the detector output comprises a first signal formed in response to the modulating of the wavelength of the beam of light with the modulation signal and further comprises a second signal formed in response to the modulating of the intensity of the beam of light with the burst signal; and processing the first and second signals and calculating a ratio of the first and second signals, the ratio being indicative of a concentration of said at least one component of the gas.