4 November 2010 Identification of ores and gems using THz polarization information
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Abstract
The polarization information of various ores and gems in the terahertz (THz) frequency region has been investigated. The images of the samples for different polarization are captured by a balanced polarization imaging system. The system employs a balanced electro-optic (EO) detection method for two-dimensional THz real-time imaging, which systemically integrates the THz balanced EO sampling technique and the dynamic subtraction technique. The proposed method can effectively improve the signal to noise ratio and the spectrum measurement accuracy of the imaging system. The imaging speed is dramatically reduced by using two high speed CCDs which are used to detect two orthogonal polarization components of probe beam. The subtraction of two corresponding images presents the balanced image of the sample. By rotating the polarization of the probe beam by 45 degree, another polarization component which is orthogonal to the present one can be measured. The experiment results demonstrate the advantage of the method. The spectra of the samples on each point can be extracted from a series of images, thus the refractive indices, absorption coefficients, and polarization rotation coefficient can be drawn. The information can be used to identify samples.
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Zhi Yu, Ye Cui, Xinke Wang, Yan Zhang, "Identification of ores and gems using THz polarization information", Proc. SPIE 7854, Infrared, Millimeter Wave, and Terahertz Technologies, 78541U (4 November 2010); doi: 10.1117/12.870541; https://doi.org/10.1117/12.870541
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