Gas passive infrared imaging technology with high dynamic range (HDR) offers numerous advantages in monitoring harmful gases, including high sensitivity, large detection range, ability to detect multiple hazardous gas types, and strong long-range detection capabilities. However, HDR images cannot be directly displayed on standard devices and need to be compressed to an 8-bit data width for visualization. Improper compression may lead to loss of detail and reduced contrast. Additionally, gas passive infrared imaging often suffers from poor detail, blurred edges, low signal-to-noise ratio, and limited contrast with the background, resulting in overall visual blurring. To address these challenges, this paper proposes an adaptive enhancement and dynamic compression method specifically designed for 14-bit gas infrared images. This method effectively compresses the background information while preserving and enhancing the texture details of weak gas cloud targets. The proposed methodology involves a hierarchical decomposition of the input image into detail and background layers. Subsequently, each layer undergoes separate processing: the detail layer is subjected to enhancement, while the background layer undergoes dynamic range compression. Finally, the enhanced detail layer and compressed background layer are fused to produce an 8-bit image. A comprehensive evaluation is conducted comparing the proposed algorithm with histogram equalization using both subjective visual assessment and objective evaluation metrics. The results demonstrate that the proposed algorithm successfully enhances the clarity of gas cloud targets, improves overall contrast, and effectively suppresses halo artifacts and image noise.
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.
It is aimed at environment pollution gases remote sensing in wide infrared spectrum, using the technique of long wavelength infrared Fourier transform spectrometer, by extended the detector responsive spectral range, to detect the spectral ‘fingerprint’ characteristic under the certain condition. The paper specifically described experiments in the spectral range 7.0 cm-1~14.5μm (700-1450 cm-1). The application example by used instrument PARES100 is showed, with both the spectral radiance difference and brightness temperature, the 11 kinds industry common chemical and toxic vapors gas were successfully detected, and the approximate concentration that could been measured in terms of concentration and path length times.
The principle of Gas Identification Method for Long-Wave Infrared Hyperspectral Imaging based FTIR was described in detail. The method of spectral data preprocessing and calibration,radiation transfer mode, algorithm of identifying and concentration retrieving of chemical gas,the detection limit and detection distance were analyzed. The development situation of passive IR remote sensing for chemical gas cloud detection technique was investigated,as well as the key parameters of them.
Infrared radiomentric calibration is of critical importance for information quantification of remote sensing of environment at infrared spectrum. In the quantitative analysis, the calibration of the measured spectra is very important. LWIR Interferometric Hyperspectral Imager Spectrometer Prototype (CHIPED-1) is developed for studying Radiation Calibration. Two-point linear calibration method is carried out for the spectrometer by using blackbody respectively. Firstly, relative intensity is converted to the absolute radiation lightness of the object. Then, radiation intensity of the object is converted the brightness temperature spectrum by the method of brightness temperature. The result indicated that this method of Radiation Calibration calibration was very good. This calibration method is of significance to the further analysis of atmospheric transmission and the retrieval of the concentration of infrared chemical gas in atmosphere.
With the advantages of fluorescence excitation and environmental adaptability simultaneously, Ultraviolet Image Spectroscopy has shown irreplaceable features in the field of latent target detection and become a current research focus. A design of Large Aperture Ultraviolet Spatially Modulated Imaging Spectrometer (LAUV-SMIS) based on image plane interferometer and offner system was first proposed in this paper. The data processing technology of time-spatial modulation FTIS in UV band has been studied. The latent fingerprint could be recognized clearly from the image since which is capable to meet the need of latent target detection. The spectral curve of the target could distinguish the emission peak at 253.7nm and 365nm when the low pressure and high pressure mercury lamp were used as the illuminator. Accurate spectral data of the target can be collected on the short and long wave ends of the working band.
The new progress of ground-based long-wave infrared remote sensing is presented, which describes the windowing spatial and temporal modulation Fourier spectroscopy imaging in details. The prototype forms the interference fringes based on the corner-cube of spatial modulation of Michelson interferometer, using cooled long-wave infrared photovoltaic staring FPA (focal plane array) detector. The LWIR hyperspectral imaging is achieved by the process of collection, reorganization, correction, apodization, FFT etc. from data cube. Noise equivalent sensor response (NESR), which is the sensitivity index of CHIPED-1 LWIR hyperspectral imaging prototype, can reach 5.6×10-8W/(cm-1.sr.cm2) at single sampling. Hyperspectral imaging is used in the field of organic gas VOC infrared detection. Relative to wide band infrared imaging, it has some advantages. Such as, it has high sensitivity, the strong anti-interference ability, identify the variety, and so on.
The radiometric calibration of LWIR Hyperspectral imager Spectrometer is presented. The lab has been developed to LWIR Interferometric Hyperspectral imager Spectrometer Prototype(CHIPED-Ⅰ) to study Lab Radiation Calibration, Two-point linear calibration is carried out for the spectrometer by using blackbody respectively. Firstly, calibration measured relative intensity is converted to the absolute radiation lightness of the object. Then, radiation lightness of the object is is converted the brightness temperature spectrum by the method of brightness temperature. The result indicated †that this method of Radiation Calibration calibration was very good.
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