Research on rapid concentration field reconstruction method for two-dimensional geometric paths based on laser absorption spectroscopy

The combination of laser absorption spectroscopy and computed tomography (CT) has been extensively applied to two-dimensional concentration field reconstruction. Additional optical paths are required to fulfill inversion requirements to ensure measurement accuracy, and the traditional two-dimensional (2D) measurement space range is approximately 1 square meter (m²) or even smaller. However, the traditional two-dimensional measurement method is no longer suitable for accurately reconstructing large-scale open spaces. In this paper we proposed a fast concentration field reconstruction method for two-dimensional geometric paths. Firstly, a two-dimensional geometric path with six optical paths is designed. After obtaining the spectral signals from these paths and before beginning iterations, the integral absorbance is used to predict if there is a gas leakage in the grids the light paths traverse, further simplifying the overall path. Then, the remaining spectral signals were iterated, and the bi-cubic interpolation operation is applied to optimize the two-dimensional array, enhancing the resolution of the reconstructed two-dimensional distribution image. Finally, the location of the gas leakage source is determined. Subsequently, a system is developed to reconstruct the concentration field under the two-dimensional geometric path. Simulation experiments under three ammonia simulation reconstruction models were designed, and the errors r were calculated as 1.49, 1.99, and 1.63, with iterations of 128, 179, and 102, respectively. It can be observed that the number of iterations is significantly reduced without compromising the detection accuracy. Furthermore, the ammonia leakage two-dimensional detection experiments have been conducted to confirmed the reliability and validity of the proposed method for two-dimensional detection of open optical paths.