Patent ID: 7193718
Filing Date: 2007-03-20
Classification: G01J,G01N

Abstract:
1. A wavelength modulation spectroscopy method, comprising: modulating the wavelength of a light source with a frequency; passing a portion of the light of the light source to a sample for interacting and thereafter to a measuring detector; demodulating the measuring detector output at a higher harmonic of the frequency; passing another portion of the light of the light source to a monitor detector; demodulating the monitor detector output at the higher harmonic of the frequency; and further modulating the light source with the higher harmonic, wherein the modulation intensity is dependent on the demodulated monitor detector output, and the dependence comprises an integration of the demodulated monitor detector output, and further wherein the step of further modulating the light source with the higher harmonic in dependence on said monitor detector output comprises: adding the demodulated monitor detector output or a fraction thereof to a value stored in a storage mechanism; and multiplying said higher harmonic with said updated value; and storing the updated value in a wavelength modulation spectroscopy system in order to measure a sample.