Abstract
A non-local patch regression (NLPR) denoising-enhanced differential broadband photoacoustic (PA) sensor was developed for the high-sensitive detection of multiple trace gases. Using the edge preservation index (EPI) and signal-to-noise ratio (SNR) as a dual-criterion, the fluctuation was dramatically suppressed while the spectral absorption peaks were maintained by the introduction of a NLPR algorithm. The feasibility of the broadband framework was verified by measuring the C2H2 in the background of ambient air. A normalized noise equivalent absorption (NNEA) coefficient of 6.13 × 10−11 cm−1·W·Hz−1/2 was obtained with a 30-mW globar source and a SNR improvement factor of 23. Furthermore, the simultaneous multiple-trace-gas detection capability was determined by measuring C2H2, H2O, and CO2. Following the guidance of single-component processing, the NLPR processed results showed higher EPI and SNR compared to the spectra denoised by the wavelet method and the non-local means algorithm. The experimentally determined SNRs of the C2H2, H2O, and CO2 spectra were improved by a factor of 20. The NNEA coefficient reached a value of 7.02 × 10−11 cm−1·W·Hz−1/2 for C2H2. The NLPR algorithm presented good performance in noise suppression and absorption peak fidelity, which offered a higher dynamic range and was demonstrated to be an effective approach for trace gas analysis.
Highlights
There is an ever-increasing need for non-destructive and rapid monitoring technologies for multiple trace gas species and their concentrations in the fields of environmental protection, medical diagnosis, industrial production, and food safety [1,2]
Photoacoustic spectroscopy (PAS) based technologies [3,4,5,6] feature the advantages of fast response, high sensitivity, high selectivity, and a large dynamic detection range and have played an important role in multi-component gas sensing
In order to verify the spectral quality and signal-to-noise ratio (SNR) improvement of the non-local patch regression (NLPR) algorithmenhanced DFTIR-PAS gas sensor, 100 ppm C2 H2 was used as the target gas due to its simple spectral structure and absorption profile
Summary
There is an ever-increasing need for non-destructive and rapid monitoring technologies for multiple trace gas species and their concentrations in the fields of environmental protection, medical diagnosis, industrial production, and food safety [1,2]. The basic principle of PAS is that the gas molecules absorb the light energy at specific wavelengths and cause the local temperature to increase. Combined with the periodic modulation of the light source, the gas temperature thermally diffuses to generate pressure oscillations and acoustic signals [7]. Various PAS-based sensor modalities have been developed for multi-gas analysis, such as the use of multi-lasers combined time-division multiplexing methods [8,9,10], multi-resonators with various frequency demodulation schemes [11], and broadband detection-based thermal emitters or blackbody radiators using several bandpass filters [12]. Use of multiple lasers yields narrowband wavelength selection for specific gas absorption, limiting the capability to simultaneously detect multiple gases
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