Wavelength modulation spectroscopy with multiple harmonic detection
U. S. Patent 6,356,350, issued March 12, 2002
Wavelength modulation spectroscopy using tunable diode lasers is a fast and accurate way to measure trace gas concentrations. When the wavelength of a laser is modulated at a frequency F, and an absorbing gas is present in the light path, the transmitted light varies in amplitude. Fourier analysis of the power of the transmitted light shows signal components at F, 2F, 3F.... Typically, though, only a single component of the output signal is detected, such as the signal at 2F.
The invention by David Bomse and Joel Silver of Southwest Sciences simultaneously demodulates and detects two or more of the components of the output signal. This can result in better precision in the measurement of gas concentrations from their absorption spectra.
Contact Information
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