The spectral signatures in most hyperspectral classification approaches are generally treated as random vectors, which is inappropriate in denoting their typical physical characteristics, such as central wavelengths, widths, and depths of absorption bands. In this paper, we present a new classification approach by enhancing the absorption bands of spectral signatures to boost their physical information. Firstly, an analysis is made of the characteristics of absorption bands of spectral signatures. Next, an absorption bands enhancing approach is proposed based on the discussion of the approach of fusing spectral signatures and their derivative. Finally, the proposed approach is applied on two real hyperspectral subimages. The experimental results show that our proposed approach can significantly enhance the differences of spectral signatures of a hyperspectral images. And thus can improve the classification performance of hyperspectral images.
A novel micro-mechanical temperature sensor is presented theoretically and experimentally. The working principle of this sensor is based on Optical interference theory of Fabry-Perot cavity that is formed between a polished optical fiber end and micro-mechanical Bi-layered membranes. When ambient temperature is changing, Bi-layered membranes will be deflected based on 'Bi-coating effect', and then the length of Fabry-Perot cavity will be changed correspondingly. By detecting the optical output of Fabry-Perot cavity resulted from the change of Fabry-Perot cavity length, the ambient temperature can be measured. First, using finite element software ANSYS, the structures of this sensor was designed and corresponding theoretical model was set up based on theoretical analysis; Second, the sensor structure was optimized based on Fabry-Perot optical Interference theory and Bi-layered membranes dimensions selection, and theoretical characteristics was given by simulation; Third, using optical fiber 2×2 coupler and photo-electrical detector, the fabricated sample sensor was tested successfully by experiment that demonstrating above theoretical analysis and simulation results. This sensor has some favorable features, such as: micro size owing to its micro-mechanical structure, high sensitivity owing to its working Fabry-Perot interference cavity structure, and optical integration character by using optical fiber techniques.
Silicon micro-cantilever resonators are typical elements in micro-electro-mechanical systems. Basing on the photothermally excited micro-cantilever resonators, many optical microsystems can be realized, such as micro-swichtes,mciro-modulators and microsensors etc. In this paper, mechanism and experiment study is given on photo-thermally excited bi-layered silicon micro-cantilever resonators, and relative results can be served as the basis of further applications. When coating is put on the surface of micro-cantilever to increase the optically exciting efficiency, the whole resonator becomes bi-layered structure, and the mechanism of this bi-layered resonator is very different from those of single material resonators. In this paper, photo-thermally excited mechanism of bi-layered silicon micro-cantilever was presented and a corresponding photo-thermal theoretical model was set up based on the photo-thermal effect. The first three resonant modes of the silicon micro-cantilever were detected successfully by using piezoelectric resistors fabricated as a Wheat-stone sensing bridge on the micro-cantilever. A novel method was presented to excite and detect the microresonator at the same time by using only one optical source , and this novel method was demonstrated by detecting the first resonant mode of the micro-cantilever.