Image fusion is of great importance in object detection. A PCA based image fusion method was proposed. A pixel-level average method and a wavelet-based methods have been implemented for a comparison study. Different performance metrics without reference image are implemented to evaluate the performance of image fusion algorithms. It has been concluded that image fusion using PCA based method showed better performance.
A novel fiber Bragg grating(FBG) with three reflection wavelengths is proposed and demonstrated experimentally by simply phase-mask-based grating inscription over the splice interface between a thin-core fiber (TCF) and a standard single-mode fiber (SMF). The key to the success of this device lies in the refractive index differences between SMF, TCF and splice interface, and the precisely localized grating inscription over the three regions. The reflection wavelengths present different sensitivities to temperature and strain, making it as a good candidate for the measurements of two parameters simultaneously.
Three compact and static birefringent Fourier transform imaging spectropolarimeters are presented. They based on the different combinations of birefringent elements, including Savart polariscope, Wollaston prism, achromatic half-wave plate and quarter-wave plate. After acquiring several interferograms simultaneously for different polarization states with a single CCD, the spectral dependence of polarization states are recovered with Fourier transformation. The interference models are described theoretically, and the performances are demonstrated through numerical simulations and experiments. In contrast to the well-known channeled spectropolarimetry, the most important advantages are that the sampling interferograms have no channel aliasing and directly correspond to the maximum optical path difference of birefringent interferometer. That is say, they can recover the spectral variation of polarization state with the interferometer’s maximum spectral resolution.
A Static Polarizing Atmospheric Michelson Interferometer (SPAMI) system for multiple emission lines is reviewed. It changes the Optical Path Difference (OPD) by Polarization Array (PA) at one time, instead of rotating the polarizer by four times in traditional polarizing Michelson interferometer. This allows the NPAMI system to make simultaneous measurements. PA is a key element cemented by four polarizers with different polarization orientations in the SPAMI system. In practice, assembly error is brought to the polarization array unexpected. It is proved that the temperature and wind velocity measurements are highly depended on the polarization orientations of polarizers in PA. In this paper, the effect of deflection of polarization orientation on temperature and wind velocity are analyzed and discussed. Moreover, a proper approach is proposed to improve the accuracy of alignment.
A novel polarization atmosphere Michelson interferometer (NPAMI) based on PAMI was designed. We explain the method of NPAMI for atmosphere detecting and then analyze the NPAMI by Jones matrix; the equations of retrieval atmospheric wind velocity and temperature are also derived. In contrast to PAMI, the NPAMI decreases the number of times for the polarizer's rotation and processing data size, thus, highly increasing the speed of detection. This work has great significance on theoretical research, capability improvement, and would be useful for the application on the passive measurement of the wind field of the upper atmosphere.
Several novel designs of wide-field-of-view polarization imaging spectrometers based on combined Savart polariscopes are presented. By numerical modeling and analysis, we show that the field of view can be extended when the polariscopes are made of the same uniaxial crystal or positive and negative uniaxial crystals are combined. The designs with increased fields of view enable the acquisition of undistorted interferogram and high étendue for the spectrometer systems.