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A compressive fusion of remote sensing images is presented based on the block compressed sensing (BCS) and non-subsampled contourlet transform (NSCT). Since the BCS requires small memory space and enables fast computation, firstly, the images with large amounts of data can be compressively sampled into block images with structured random matrix. Further, the compressive measurements are decomposed with NSCT and their coefficients are fused by a rule of linear weighting. And finally, the fused image is reconstructed by the gradient projection sparse reconstruction algorithm, together with consideration of blocking artifacts. The field test of remote sensing images fusion shows the validity of the proposed method.

A new strategy for images fusion is developed on the basis of block compressed sensing (BCS) and multiwavelet transform (MWT). Since the BCS with structured random matrix requires small memory space and enables fast computation, firstly, the images with large amounts of data can be compressively sampled into block images for fusion. Secondly, taking full advantages of multiwavelet such as symmetry, orthogonality, short support, and a higher number of vanishing moments, the compressive sampling of block images can be better described by MWT transform. Then the compressive measurements are fused with a linear weighting strategy based on MWT decomposition. And finally, the fused compressive samplings are reconstructed by the smoothed projection Landweber algorithm, with consideration of blocking artifacts. Experiment result shows that the validity of proposed method. Simultaneously, field test indicates that the compressive fusion can give similar resolution with traditional MWT fusion.

We derive and calculate numerically laser linewidth by means of the laser rate equation in an extending diode laser cavity provided by an end reflector. We found that narrow linewidth is closely connected with phase modulation and frequency modulation. The numerical simulation shows the dominance of effect over another depends on inherent factors such as the α coefficient, bandwidth of laser, length of external cavity, reflective coefficient etc.

Images are often significantly degraded by fog and their values are greatly reduced. According to retinex theory and the properties of fogged images, fog degradation can be eliminated by modifying illumination variation. The multi-scale retinex (MSR) algorithm was analyzed and an enhancement method directing to fogged images was proposed. Firstly, a preliminary global luminance was adjusted by linear stretching and screen algorithm to increase the luminance of darker pixels and compress the dynamic range as well. Then the local contrast was increased by an improved algorithm based on MSR. Finally, the output of local contrast enhancement was processed by the normal clipping stretching to realize color correction. Experiments show that the algorithm can effectively remove fog degradation from color images.

In this article, we have investigated energy upconversion process in erbium doped oxyfuoride tellurite glasses exciated with 980 nm diode laser. The glasses used in measurements are with a mol% composition of 70TeO2-9PbF2-190AlF3-10BaF2-1Er2O3. The Ωs intensity parameters, the radiative rates, the branching ratios and the fluorescence lifetimes were calculated based upon the Judd-Ofelt theory and the experimental absorption spectrum. Under 980 nm excitation, efficient 530, 544, and 665 nm upconversion emission are due to two-photon absorption processes.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The solution precipitation is used to synthesize the Tb doped yttrium phosphates. The as-synthesized is the monoclinic phased YPO4×2H2O with churchite-type structure, which is transformed to the tetragonal phased YPO4 with xenotime-type structure as the temperature approaches 200°C during the thermal treatment process. This phase transformation process can not be observed in some routes that need a higher synthetic temperature, in which, only a high-temperature phase is obtained. The luminescent efficiency dependence on the heat-treatment temperature is investigated. The luminescent efficiency presents a two-step increase respectively around 300 and 700°C. Results indicate that the significant increase of luminescent efficiency at 300°C is not related to the phase structure transformation, but to the decrease of OH- ions content, and that the significant increase of luminescent efficiency at 700°C is related to the increase of crystallinity, which may increase the absorption to VUV light.

Ce-, Tb-doped and co-doped YBO 3 were prepared by solid-state reaction. The structure of the powder is identified as vaterite-type structure. The photoluminescence of the samples under UV/ VUV excitation were investigated. The results indicate that the energy is transferred between Ce 3+ and Tb 3+ under UV excitation while Ce 3+ is not beneficial to the emission of Tb 3+ under VUV excitation due to the different luminescence mechanism. The blue emission of Tb 3+ was observed at low Tb 3+ concentration and disappeared at high activator concentration due to the relaxation.

Bulk Y 2 O 3 : Eu (1% in molar ratio) powders and nanocrystals with different particle size were prepared by chemical self-combustion, all of them exhibits cubic structure. Fluorescent decay curves at room temperature and 10k, excitation and emission spectra were measured. The dependence of fluorescence lifetime on the particle size and temperature were discussed. Meanwhile, the quantum efficiency of 5 D 0 level of europium ion occupying C 2 site was estimated.