Tunable diode laser absorption signal time-frequency conversion method

Abstract

The invention discloses a tunable diode laser absorption signal time-frequency conversion method, which comprises the following steps: constructing a wavelength scanning-direct absorption spectrum measurement system, and collecting a wavelength etalon transmission signal and an actually measured absorption signal of a measured gas, the absorption signal having only one absorption peak; comparing the actually measured absorption signal with a database theoretical spectrum, and extracting feature points of the actually measured absorption signal and the database theoretical spectrum; obtaining a sampling point-wave number corresponding graph according to the extracted feature points, and establishing a time-frequency conversion model of a time domain and a frequency domain in the TDLAS; and comparing the time-frequency conversion model with a wavenumber calibration result, and verifying the accuracy of the time-frequency conversion model. The method provided by the invention has the characteristics of high precision, simplicity in operation and the like, has great application potential in low-cost TDLAS (tunable diode laser absorption spectroscopy) application, and plays an important role in deeply knowing the dynamic wavelength tuning characteristic of a laser.

Description

technical field [0001] The invention relates to the technical field of laser diagnosis and measurement, in particular to a time-frequency conversion method for a tunable diode laser absorption signal. Background technique [0002] Tunable Laser Absorption Spectroscopy (TDLAS) is an optical method for rapid gas detection by detecting an isolated absorption line of absorbing molecules by utilizing the narrow linewidth and fast tuning characteristics of semiconductor lasers. In practical applications, the abscissa of the detection signal obtained by the TDLAS system is generally the number of sampling points at equal time intervals, corresponding to the time series. The normalization of the line area is only valid in the frequency domain, and the abscissa of the spectrum needs to be converted into wavenumber (cm). -1 ) can be used to solve the integrated absorbance value, and the accuracy of time-frequency conversion plays an important role in the inversion accuracy of flow fi...

AI Technical Summary

Problems solved by technology

However, the traditional laser frequency measurement method has the following shortcomings: (1) The high-precision etalon will be affected by environmental disturbances and system noise during the measurement process, and the accuracy of the peak-finding algorithm is one of the reasons that affect the accuracy of time-frequency conversion; (2) The refractive index of the etalon is different for different frequency lasers, so the refractive index needs to be recalculated every time the calibration frequency is changed, and different wave bands require different material etalons

However, existing experimental methods are not applicable when only one molecular absorption peak exists within the laser scanning range

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