A laser induced breakdown spectroscopy (LIBS) system has many experimental key parameter factors. Focusing position in laser induced breakdown spectroscopy (LIBS) system is an experimental key parameter factor. The optimization of spectral intensity has been studied, but the results are often inaccurate. In this Letter, A quantitative analysis internal standard method was proposed to optimize the parameter of LIBS experimental system. One 100mm focusing lens and eight standard alloy steels with rich element content were employed as samples. By employing internal standard method, the minority elements (Mn, Cr, Cu) in steels were quantitatively analyzed and the element detection sensitivity was obtained. The limit of detection (LOD) of the minority elements under different focusing states was calculated, and finally the optimal focus position was obtained. The result which indirectly shows that the best laser focusing position of LIBS system with 100mm focusing lens is 6mm below the surface of samples, and the limit of detection (LOD) of the minority elements maintain the minimum value at this position (0.00159 wt.%), which indicates that the quantitative analysis method is effective and reliable for optimizing the parameters of LIBS system.
With the development of technology, research on solar flares has been gradually developed, and the corresponding detection band also involves hard X-ray. Due to the particularity of hard X-ray, the collimator is generally used to observe it. When observing the sun, the load is required to point at the sun accurately. This paper mainly introduces an optical system for precise pointing to the sun of the solar hard X-ray imager. By optimizing the design, the measurement requirements are satisfied. In addition, the design results, system ghost images and measurement accuracy are analyzed and evaluated.
For the demand of inland water quality monitoring, a ground-based multi-spectral imaging method has been developed. By means of developing an instrument which can gather the multi-spectral data of the waterbody, the method can be used for real-time monitoring the contamination of inland waters, such as cyanobacteria bloom and phytoplankton. The research is focused on the technology of high-resolution multi-spectral data extraction and the theory of contaminant inversion model. Four branches of light beams of simple spectrum are obtained with spectral filters and are recorded by four groups of lens and detectors respectively. The four interested wavelength is chosen as 565 nm, 620 nm, 660 nm, 750 nm, according to the typical reflection peaks and dips of the contamination with a spectral resolution of 15 nm. The optical design features a field of view of 25.2×19.3 degree with a 16mm focal lens. The camera’s resolution is 1628×1236 with the pixel size of 4.4 microns that reaches the spatial resolution of 0.945 arc min. The multi-spectral image is obtained through out-door experiments by monitoring the inland lake—Dianchi at a distance of 5 kilometers. After data revision, we can identify the constituent of the underwater contaminant and explain the pollution situation of cyanobacteria bloom in a certain period quantitatively. The inversion and extraction accuracy can reach at least 85%. And the long-term observation can explore the seasonal pattern of cyanobacteria bloom outbreak.
In order to reduce the optical intensity of backscattering lights of the Cassegrainian optical antenna in the optical system of the laser communication terminal and improve the optical isolation of laser communication system, this paper proposes a method for designing high isolation level Cassegrainian optical antenna by increasing the characteristic value of the optical intensity of backscattering lights E/N. The method aims to improve the optical antenna isolation through reducing the optical intensity of backscattering lights along the incident optical path based on analyzing the theoretical model of the optical intensity of backscattering lights BRDF. A Cassegrainian optical antenna for laser communication is designed in this paper, and the method is used to optimize the isolation of this optical antenna by custom operands in ZEMAX. Then using TracePro software builds the optical structure model of this optical antenna before and after optimization, simulate the optical intensity of backscattering lights of each model, calculate and analyze the isolation of each model by using simulation data respectively. It is show that the backscattering rate of the system decreases from 0.0011956 to 0.00007515, and the isolation decreases from -29.224dB to -41.24dB. Optimization has improved the isolation 12.017dB of the optical system through use the method.
The explosives detection has been a hot and difficult issue in the field of security,it is particularly important to detect explosives quickly and reliably. There are many methods to detect explosives currently, stand-off Raman spectroscopy is one of the most promising and practical technologies, this technique can be used for non-contact and nondestructive detection, ensure the safety of attendants, at the same time the precision and speed of detection are also very high and be characterized by rapid response. This paper mainly gives an account of the fundamental principle of Raman spectroscopy, as well as recount major challenges of Standoff Laser Raman Spectroscopy applied in explosives detection and corresponding solutions. From the perspective of the system, this paper sums up related theories and techniques of the excitation laser and telescopic system etc.. Ultimately, a brief analysis and summary of the development trend of this technology is given.
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