In modern warfare, environmental monitoring, national defense and social security monitoring, it is important to detect toxic and hazardous chemical contaminants on the surface of materials in target areas. Finding a rapid and non-contact technique for detecting these contaminants is urgently needed. To meet these application requirements, this article proposes a short-wave infrared (SWIR) spectral imaging detection technique based on a liquid crystal tunable filter(LCTF), and an imaging spectrometer was developed. Toxic and hazardous chemical contaminants can be accurately identified by the spectrometer, and their spatial distribution information can be intuitively displayed in images. This article analyzed various toxic and hazardous chemical liquids under different conditions, such as DMMP and dichloromethane. The results show that these chemical contaminants have obvious absorption characteristic spectrum within the spectral range of 0.95μm-1.70μm. The identified analysis results and their spatial distribution information were obtained by analyzing their characteristic spectrum. Since this detection technique does not rely on the morphological features of the target, and can achieve non-contact, long-distance detection, making it a potential and effective technique for detecting and monitoring toxic and hazardous chemical contaminants.
Fourier Transform Infrared(FTIR) spectroscopy has many advantages, such as high light flux, high resolution, high sensitivity and so on, and has been widely used in the field of industrial gas monitoring. Unit detector is used by traditional Fourier transform infrared spectrometer, which needs scanning platform to assist imaging, and the structure of spectrometer is complex. In order to satisfy the application of small area array detector spectrometer, this paper is based on the small area array HgCdTe photoconductive long wave infrared detector and double pendulum interferometer. The working principle and signal characteristics of the spectrometer are analyzed, and a method of multi-channel weak interference signal detection circuit for 4×4 small area array detector is proposed, and the method is simulated and verified by experiments. Using Multisim software to simulate the circuit, the results show that the circuit has good band-pass characteristics and can achieve distortion-free signal amplification. The collected interference data are analyzed by using MATLAB software, and the interference data are subjected to spectral restoration and spectral calibration. The results show that the amplitude consistency and phase consistency of the interference data are good, and the spectral waveforms of each channel are close to each other, which can well distinguish and measure the long wave characteristic peaks in the region.
KEYWORDS: Mirrors, Interferometers, Signal detection, Spectroscopy, FT-IR spectroscopy, Control systems, Michelson interferometers, Infrared spectroscopy, Control systems design, Computer programming
Michelson interferometer is one of the core technologies of time-modulated Fourier transform infrared spectrometer. And the control effect of the interferometer moving mirror has a very important influence on the instrument performance. In this paper, based on the double pendulum interferometer, the control technology of its moving mirror is studied. According to the basic principle of double pendulum interferometer, the general scheme of hardware system design is proposed. And under the guidance of the overall scheme, the modular design of the control system is carried out. There are mainly laser detection modules, main control module, motor drive module, etc. The moving mirror control algorithm is designed in the lower computer software, and the speed of the moving mirror is controlled using the compound control algorithm formed by the combination of incremental PID control and feed-forward control. The control effect of the moving mirror is improved. The upper computer software uses LabVIEW to design and test the control effect of the control system. The test results show that the relative speed error of the moving mirror based on the double pendulum interferometer is better than ±0.35%, and the stability is high, which can meet the requirements of the interference system index.
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