Oocytes vitrified using CPS, OPS or grids could lessen spindle injuries and expedite recuperation. The survival using OPS or grids is lower. Sufficient culture time for recovery of meiotic spindle would be imperative for fertilization events of vitrified oocytes. CPS has the advantages of achieving a high survival and preserving good spindles.
Passive millimeter and terahertz wave imaging has become a significant potential technique for human security check and scene monitoring. Due to the small difference of the brightness temperatures between human body and concealed objects, the temperature sensitivity and spatial resolution of radiometers are always the key performance indexes which are difficult to improve. Therefore, when the hardware performance is given, improving detectivity becomes a pressing need. In this paper, a physically-based concealed object enhancement method using multi-polarization information is presented. The polarization model and polarization property of human body and concealed objects have been analyzed. By fusing multiple polarization images, we can obtain a complete polarization image in which the contrast between human body and concealed objects is enhanced and stable. The experimental results of simulation and measurement demonstrate the enhancement performance, and Differential Signal Noise Ratio (DSNR) is obviously improved by using the proposed method.
Passive millimeter and terahertz wave imaging is a powerful way for personnel security inspection and scene monitoring. The existing systems usually have a single polarization mode. To obtain more information, polarimetric imaging has been preliminarily explored recently. However, there is no work exhibiting high-performance polarimetric imaging to analyze and interpret polarization characteristics. In this Letter, we report on the development of a W-band passive polarimetric imaging system for human body screening and present the polarization characteristics analysis of several typical scenarios. The experimental system has a spatial resolution of better than 2 cm at 2.5 m distance and has a thermal sensitivity of better than 0.3 K. The system can display polarization properties of human bodies and concealed objects. The experimental results demonstrate that passive polarimetric imaging has a great potential for object contrast enhancement, detection, segmentation, and recognition.
The polarization properties of thermal millimeter-wave emission capture inherent information of objects, e.g., material composition, shape, and surface features. In this paper, a polarization-based material-classification technique using passive millimeter-wave polarimetric imagery is presented. Linear polarization ratio (LPR) is created to be a new feature discriminator that is sensitive to material type and to remove the reflected ambient radiation effect. The LPR characteristics of several common natural and artificial materials are investigated by theoretical and experimental analysis. Based on a priori information about LPR characteristics, the optimal range of incident angle and the classification criterion are discussed. Simulation and measurement results indicate that the presented classification technique is effective for distinguishing between metals and dielectrics. This technique suggests possible applications for outdoor metal target detection in open scenes.
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