Multiple optical path refractive cavity calibration method based on variable angle optical density

Abstract

The invention discloses a multiple optical path refractive cavity calibration method based on the variable angle optical density. Basic parameters of a refractive cavity are analyzed and calculated to get all optical density values arising from the interaction of a refracting beam of the refractive cavity and a standard optical density sheet; and a total optical density value Ds(lambda) is obtained. The standard optical density sheet is placed in the refractive cavity whose optical density value Dc(lambda) is measured; measuring deviation of the refractive cavity is calculated according to the formula sigma(D lambda) = Dc(lambda) - Ds(lambda), a standard uncertainty of the refractive cavity and a calibrated expanded uncertainty are calculated according to the measuring deviation, and the obtained calibrated expanded uncertainty is the detection limit of the multiple optical path refractive cavity. The calibration method is entirely based on optical measurement without any need of standard air assessment, eliminates the complex influence of uncertainties of introduced gas, achieves calibration of the refractive cavity at a low-uncertainty level, and improves the calibration accuracy of the detection limit.

Description

technical field [0001] The invention belongs to the technical field of folding cavity calibration, and relates to a multi-optical-path folding cavity calibration method based on variable-angle optical density. Background technique [0002] The multi-path folded cavity is an optical instrument that uses the spectral absorption characteristics of the gas to measure the gas concentration. For the calibration of this multi-path folded cavity for gas concentration measurement, at present, the standard gas with known concentration is mainly used for cavity calibration, and then the least square method is used to fit the differential absorption spectrum to calculate the concentration of trace gas. The detection limit of the system was estimated from the fitting residuals. This detection limit estimation is an estimation based on experimental data rather than a direct experimental calibration detection limit. The detection limit of the experimental calibration is to pass the gas t...

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Problems solved by technology

In fact, it is very difficult to calibrate the detection limit of ppb level by direct experiment: firstly, it requires accurate generation of ppb level standard gas; secondly, due to the existence of material adsorption and other problems, it is actually difficult to accurately control the ppb level in the absorption cell Trace gas concentrations on the order of

Therefore, domestic and foreign researchers always estimate the detection limit of the system rather than the detection limit of the experimental calibration when analyzing the performance of the multi-path folded cavity system. The detection limit obtained by this method has certain errors, and the accuracy cannot be effectively obtained. ensure

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