Spatial light modulator (SLM)-based tunable sources synthesize any specified spectral power distribution. However, their complexity makes a simpler version desirable. A prism before an SLM-projector is shown to synthe...
详细信息
Spatial light modulator (SLM)-based tunable sources synthesize any specified spectral power distribution. However, their complexity makes a simpler version desirable. A prism before an SLM-projector is shown to synthesize spectra at least as effectively. Moreover, this simple setup projects two-dimensional (2-D) videos onto a one-dimensional (1-D) screen. Viewed through a prism (or grating), rainbow-colored renderings of grayscale videos emerge. The semitransparent, 2-D virtual images face each viewer all around the 1-D screen. Uncannily, mirrors around the 1-D screen cannot flip the images. In hindsight, SLM-based spectral synthesis is essentially a form of spectral encoding that is applicable to video projection, and beyond. (C) 2014 Optical Society of America
Information retrieval is critical in security technologies such as those for status identification and documentation authentication. Ideally, coding materials should be difficult to locate, impossible to counterfeit, ...
详细信息
ISBN:
(纸本)9780819468994
Information retrieval is critical in security technologies such as those for status identification and documentation authentication. Ideally, coding materials should be difficult to locate, impossible to counterfeit, and easy to process. This presentation addresses a novel information retrieval technology with these ideal features of its coding materials: the photo-luminescent (PL) quantum-dots (QD) synthesized via wet-chemistry approaches. As compared to traditional PL materials, they exhibit emission with narrower full width at half maximum, greater brightness, and higher photostability;also, their PL wavelength can be easily and accurately tuned via their size, structure, and composition. Due to such a feasible tune-ability, mainly, QDs have demonstrated enormous potential applications in security and defense. When QDs are excited, they can provide coded information with their PL wavelength and intensity. If the coding wavelengths from the QD PL are designed as the Fraunhofer lines, i.e. black lines in solar spectrum, the retrieval system can extract the useful information even under sunshine covering areas. Multi-photon excitation (MPE) technologies can further extend applications of QDs to multi-layer information extraction. For an info-label of 2-millimeter in depth, a MPE system with the depth resolution less than one micro-meter can thus achieve 2 GB resolutions, when a coding material exhibiting 6 PL wavelengths with 10 intensity levels. In general, transparent thin-film coating of QDs can be applied to various substrates, such as documents, fingernails, and military helmets and vehicles. Moreover, QD based security information can be easily destroyed by preset expiration in the presence of timing agents.
In cognitive radio systems, cooperative spectrum sensing among cognitive users is necessary in order to increase the reliability of detection. However,when the number of cognitive users tends to be very large, the sys...
详细信息
ISBN:
(纸本)9781849192064
In cognitive radio systems, cooperative spectrum sensing among cognitive users is necessary in order to increase the reliability of detection. However,when the number of cognitive users tends to be very large, the system overhead for reporting their sensing results to the common receiver will be huge. In this paper, we present a novel efficient cooperative spectrum sensing scheme based on orthogonal waveforms design. By designing mutual orthogonal waveforms for different sensing bits, all the users are allowed to transmit their sensing information simultaneously on the same available band. Analytical results demonstrate that it can significantly outperform TDMA and FDMA schemes on the improvement of the transmission efficiency, especially for large-scale CR networks.
In cognitive radio systems, cooperative spectrum sensing among cognitive users is necessary in order to increase the reliability of detection. However, when the number of cognitive users tends to be very large, the sy...
详细信息
ISBN:
(纸本)9781849192064
In cognitive radio systems, cooperative spectrum sensing among cognitive users is necessary in order to increase the reliability of detection. However, when the number of cognitive users tends to be very large, the system overhead for reporting their sensing results to the common receiver will be huge. In this paper, we present a novel efficient cooperative spectrum sensing scheme based on orthogonal waveforms design. By designing mutual orthogonal waveforms for different sensing bits, all the users are allowed to transmit their sensing information simultaneously on the same available band. Analytical results demonstrate that it can significantly outperform TDMA and FDMA schemes on the improvement of the transmission efficiency, especially for large-scale CR networks.
暂无评论