[Study on the Design of Explosive (HNS) Content Analysis System Based on THz Spectrum Monomer].

HNS quantitative spectral analysis can not be achieved with the existing infrared Fourier transform spectrometer. As a common monomer explosive concerned, quick identification and quantitative analysis of the substance is important, so it is necessary to research and design a HNS detection system based on THz spectroscopy. Transmissive mode was used in the system to calculate the content of HNS. Electro-optic modulator module was introduced in the system, in order to achieve steady and rapid static scanning optical path. In the experiments HNS characteristic absorption peak positions were acquired. With this basis, combined air absorption characteristics of the wavelength band and spectrum data correlation expression was obtained, thus more characteristic wavelengths selected were determined. According to Beer-Lambert law, the function expression of HNS content and coefficient formula were presented. In the experiment different content of HNS sample powder was obtained with chemical configuration method with the content at the standard level. It made HNS sample powder into HNS Sample slice for all HNS samples, and it carried out HNS content testing with MINI-Z Terahertz spectroscopy and the system. Experimental results show that the results of the two methods are similar in the range of 0.10% to 50.00% for HNS content. Their error is less than 5.0% compared to the standard value, and the system has better linearity.

[Research on Anti-Camouflaged Target System Based on Spectral Detection and Image Recognition].

To be able to quickly and efficiently identify Enemy camouflaged maneuvering targets in the wild environment, target recognition system was designed based on spectral detection technology and video target recognition method. System was composed of the visible light image acquisition module and static interferometer module. The system used image recognition technology to obtain two dimensional video images of measurement region, and through spectrum detection technology to identify targets. Ultimately, measured target was rebuilt on the corresponding position in the image, so the visual target recognition was realized. After the theoretical derivation, identifiable target function formula of the system was obtained, and based on the functional relationship to complete the quantitative experiments for target recognition. In the experiments, maneuvering target in the battlefield environment was simulated by a car. At different distances, the background was respectively selected to detect a flat wasteland, bushes and abandoned buildings. Obvious target, coated camouflage target and covered disguises target was respectively spectrum detection. Experimental results show that spectrum detection technology can overcome the shortcomings of unrecognized the camouflaged target by traditional image target recognition method. Testing background had some influence on spectrum detection results, and the continuity of the background was conducive to target recognition. Covered disguises target was the hardest to identify in various camouflage mode. As the distance between the target and the system increases, signal to noise ratio of the system was reduced. In summary, the system can achieve effective recognition of camouflaged targets to meet the design requirements.

[Portable High-Precision System for CH4 Concentration Detection in Mines based on the Laser Mode-Hopping].

In order to detect rapid, portable concentration of methane in the mine, meanwhile, the system included a high sensitivity and a long working period, designed differential optical absorption spectroscopy method based on mode-hopping of semiconductor laser, and established wireless detection system for concentration of methane in the mine. Output wavelengths of the semiconductor laser occurred mode-hopping by modulation current of the system, so it obtained the two wavelengths close to the laser, and one is on the characteristic absorption peak of methane, while the other is not substantially absorbed. When the two beams of light were illuminated test chamber, methane concentration of the gas chamber was solved by Bill Lambert law with the difference of the light intensity between the two beams. Light source used DFB single mode semiconductor laser from Japan Anritsu company. Experimental results show that, when the modulation current increased from 20.0 to 60.0 mA, output wavelength occurred mode-hopping when the modulation current reached 48.3 mA, and output wavelength changed to 1 651.020 nm from 1 650.888 nm. By HITRAN spectrum database, it showed that the position of the wavelength 1 650.888 nm can be used for characteristic absorption peaks, while the wavelength 1 651.020 nm was suitable for reference wavelength. On this basis, the standard concentrations of methane gas was tested in the sealed container, test data of the system was compared to the H-BD5GD410-HC portable methane detector. Test results of the system and the H-BD5GD410-HC portable methane detector were similar, but with the constant concentration increased, the detection error of the system is relatively stable, slightly better than the portable methane detector. Detection error of system were less than 0.050%, under the conditions that there were without the use of expensive phase lock or inspection phase circuit, to achieve the accuracy of better than 0.10% concentration of methane detected in the mine.

[Remote system of natural gas leakage based on multi-wavelength characteristics spectrum analysis].

In order to be able to quickly, to a wide range of natural gas pipeline leakage monitoring, the remote detection system for concentration of methane gas was designed based on static Fourier transform interferometer. The system used infrared light, which the center wavelength was calibrated to absorption peaks of methane molecules, to irradiated tested area, and then got the interference fringes by converging collimation system and interference module. Finally, the system calculated the concentration-path-length product in tested area by multi-wavelength characteristics spectrum analysis algorithm, furthermore the inversion of the corresponding concentration of methane. By HITRAN spectrum database, Selected wavelength position of 1. 65 microm as the main characteristic absorption peaks, thereby using 1. 65 pm DFB laser as the light source. In order to improve the detection accuracy and stability without increasing the hardware configuration of the system, solved absorbance ratio by the auxiliary wave-length, and then get concentration-path-length product of measured gas by the method of the calculation proportion of multi-wavelength characteristics. The measurement error from external disturbance is caused by this innovative approach, and it is more similar to a differential measurement. It will eliminate errors in the process of solving the ratio of multi-wavelength characteristics, and can improve accuracy and stability of the system. The infrared absorption spectrum of methane is constant, the ratio of absorbance of any two wavelengths by methane is also constant. The error coefficients produced by the system is the same when it received the same external interference, so the measured noise of the system can be effectively reduced by the ratio method. Experimental tested standards methane gas tank with leaking rate constant. Using the tested data of PN1000 type portable methane detector as the standard data, and were compared to the tested data of the system, while tested distance of the system were 100, 200 and 500 m. Experimental results show that the methane concentration detected value was stable after a certain time leakage, the concentration-path-length product value of the system was stable. For detection distance of 100 m, the detection error of the concentration-path-length product was less than 1. 0%. With increasing distance from tested area, the detection error is increased correspondingly. When the distance was 500 m, the detection error was less than 4. 5%. In short, the detected error of the system is less than 5. 0% after the gas leakage stable, to meet the requirements of the field of natural gas leakage remote sensing.

[Research on improving sensitivity of the characteristic spectrum in micro-gas monitor].

In order to realize the indoor micro noxious gas real-time monitor, and enhance measuring accuracy based on the characteristic spectrum examination method, a characteristic wavelengths filtration window was designed, in which the container is full with the highly concentrated testing gas. The container with the highly concentrated testing gas was used as the filtration window, the standard air as the reference window, the air chamber sufficient testing gas for testing density. The experiment demonstrated that using the WQF-520-FTIR infrared spectroscope to obtain the infrared absorption spectrum of dipropyl sebacate, there were mainly four characteristic wavelength lines: 3.385 26, 3.417.64, 5.797 11, and 8.561 65 microm, and the corresponding extinction was 1.520 0, 1.542 1, 2.431 8 and 1.352 6 respectively. The smallest content examined was 50 ppb, but using the characteristic wavelengths filtration window, the method could realize the 10(-4) nm magnitude alignment. The sensitivity was enhanced nearly 10 times, and the characteristic wavelengths filtration window method has the merits of high sensitivity, no discontinuity, real-time examination, and so on.