Tong Jj

Remote sensing of chemical gas cloud emission by passive infrared scanning imaging system

Passive Fourier-transform infrared (Passive-FTIR) spectroscopy allows rapidly identification of the air pollution. However, for the localization of a leak and a complete assessment of the situation in the case of the release of a hazardous chemical gas or biological cloud, information about the position and the spatial distribution of a cloud is very important. In this work, a scanning imaging passive FTIR system, which composed of an interferometer, a data acquisition and processing software, a scanning system, a video system, and a laptop has been developed. The concentration retrieval algorithm for the passive FTIR remote measurement of gas cloud is presented, which involves the infrared radiative transfer model, radiometric calibration and absorption coefficient calculation. The concentration of the object gas is retrieved by using the nonlinear least squares method. And no background spectra are required. The remote sensing experiment of SF6 was carried out. The measuring result shows that, the column densities of all directions in which a target compound has been identified may be retrieved by a nonlinear least squares fitting algorithm and algorithm of radiation transfer, a false color image is displayed. The results are visualized by a video image, overlaid by false color concentration distribution image. The system has a high selectivity, and it allows visualization and quantification of pollutant clouds. The system allows mobile, real-time and fast measurements of chemical gas and biological clouds.

A Fast Infrared Interferogram Reconstruction Method of FTS Based on Improved Brault Algorithm

The spectrum SNR in Fourier transform interferometer(FTS) are effected by sampling error caused by the vibrate and temperature variation. The Brault algorithm overcomes these problems but needs huge sample data and complex data processing, which make the method not practical.This paper designed a new fast optical difference information reconstruction method based on quadrature phase demodulator, which also deducecd sample data number.And also designed a fast interpolation method based on variable-length truncated sinc function which can deduced the data number and control output precision.Then it realized the fast high precision interferogram reconstruction method based on equal-time sampling.With this method, the FTS can be used in field application condations with high preformance and stability, and improves the development of spectrum analysis in many areas.

A Moving Mirror Driving System of FT-IR Spectrometer for Atmospheric Analysis

A moving mirror driving system of FT-IR spectrometer for atmospheric analysis was developed. It uses a tilt-compensated interferometer, a He-Ne laser reference interference system, and a driving system based on microcontroller with the control mechanism of adaptive adjustment Fuzzy-PI. The structure is simple and easy alignment. The controller is robust and high precision. It can be used in many applications of atmospheric analysis, such as open path or solar occultation flux FT-IR methods.

Measurement and study of partial VOCs based on open path FTIR

This paper describes a long path Fourier transform infrared spectroscopy system which is used to analyze ambient gas. Some VOCs (C2H2, C2H4) are measured with this system in laboratory. As different VOCs has unique infrared absorbing spectrum, we retrieve VOCs concentration based on the nonlinear least square algorithm. The result shows that the system is stable and rapid. The retrieved concentrations are very close to real value. The system can used to monitor and research VOCs in ambient gas.