High-risk liquid chemicals inadvertently enter the surrounding environment during production, storage, transportation, and use, posing a serious threat to ecosystems and human health. How to quickly detect chemical contaminants has become an urgent problem to be solved. In this paper, a new method of short-wave infrared 0.9-1.7 μm hyperspectral imaging telemetry based on liquid crystal tunable filter (LCTF) is proposed to replace the traditional contact non-imaging sampling analysis method. The dichloromethane liquid is characterized and combined with the envelope method and correlation coefficient algorithm for identification imaging. It can achieve remote sensing identification and distribution of four toxic liquids within a short distance of 0.5-1.5 meters, with a spectral resolution of up to 30 nm and a recognition accuracy of 99%. It is a fast and accurate method for detecting surface chemical agents and toxic and hazardous substances on contaminated surfaces. Shorten the time of chemical reconnaissance and improve the efficiency of environmental perception.
Infrared hyperspectral imaging passive telemetry system is applied to chemical gas monitoring. Noise equivalent radiation brightness (NESR) is an important index to characterize the sensitivity of the system. Firstly, the theory of Noise Equivalent Spectral Radiance (NESR) of passive infrared telemetry system is introduced. Based on infrared radiation transmission theory and simple three-layer model, the noise equivalent radiation brightness (NESR) of infrared hyperspectral imaging system under area array detector is deduced. Three calculation methods of NESR are introduced. The principle experimental device of long-wave infrared hyperspectral imaging spectrometer (CHIPED-1) developed by ourselves is used to validate the method. The NESR distribution at 10μm is obtained by calculating the measured data, which is helpful to the photoelectric sensitivity study of infrared hyperspectral imaging system under area array detection.
Raman lidar is an active remote sensing technology that has been widely applied in fields such as laser atmospheric transmission, global climate prediction, aerosol radiation effects, and atmospheric environment. Raman lidar has the ability to measure target distances and provide spatial depth resolution. It offers high sensitivity and a long detection range without the need for cooperative targets. In this study, a pulsed laser with a wavelength of 355 nm and a single-pulse energy of 350mJ was used as the light source. The spectrometer system employed a blazed grating and a narrowband filter. Signal acquisition was performed using a 450 mm diameter Cassgrain telescope, and a single-photon detector was utilized to enhance the extraction and detection of Raman signals. Outdoor telemetric measurements of dimethyl methylphosphonate (DMMP) gas were conducted. In the vehicle moving mode, target gases could be detected up to a distance of 1.8 km. In the stationary mode, target gases could be detected up to a distance of 5 km.
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.
The fields of safety production, environmental monitoring, public safety, and other areas all benefit greatly from the use of gas detection technologies. The infrared image can represent the spatial distribution of the gas cloud and the background, allowing for long-distance and non-contact detection during hazardous chemical accident rescue. One of the major challenges in gas detection based on infrared imaging is how to choose and gather the spectral information of the gas. It determines the properties of the complete imaging system, including its complexity, the kinds of gases that may be detected, and the sensitivity of the detection. In this paper, a gas detection system based on multispectral infrared imaging was designed, which used short pass and long pass filters to separate light. It was composed of imaging optical system, uncooled focal plane detector, filter wheel and data acquisition and processing system. The rotating filter wheel was used to separate the radiation of the object to obtaining images with different spectral information. Using image processing techniques like image subtraction and spectral angle mapping, the diffusion zone of a gas was estimated. The identified gas cloud was color-mapped in the infrared image. The infrared image had a resolution of 640 × 512, and the time from gas leakage to warning was less than two seconds. The working band of the system was 6.5-14.5 μm, and the real time detection of NH3, SF6, CH4, SO2 was realized.
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