Measurement of concentration or concentration ratios of gas components, for potential use in breath analysis of a patient's digestion/metabolism, uses a structured laser beam where sound waves are detected and evaluated

摘要

The technique is for measurement of the concentration or concentration ratios of gas components for potential use in breath test analysis. The sample is held in a measurement cell (16), where a single-mode spectral modulated laser beam (14) is provided using an operating current (32,34). The technique is for measurement of the concentration or concentration ratios of gas components for potential use in breath test analysis. The sample is held in a measurement cell (16), where a single-mode spectral modulated laser beam (14) is provided using an operating current (32,34). The radiation is passed through the measurement cell by a temperature-controlled laser diode (10) with an optical system (12), working with a temperature sensor (24), a thermo-electric cooler (22) and a control circuit (26). The sound waves generated by the absorbed laser energy are detected by a microphone (38), with a phase-sensitive amplifier (40) for the microphone signals. The laser diode emission wavelength is set to be mode jump-free, controlled spectrally on an absorption line of the gas component for detection using the operating temperature or current, for the resulting photo-acoustic signals to be evaluated.