As an effective super-resolution reconstruction technique, the original iterative back-projection (IBP) suffers from jaggy artifacts around the edge caused by the initial estimation of high-resolution image obtained with traditional interpolation methods like bilinear interpolation. In this paper, we present an edge-preserving iterative back-projection method for image super-resolution, which employs an effective edge-preserving interpolation method called iterative curvature based interpolation (ICBI) method for up-sampling to get the initial estimation of high-resolution image. The proposed method combines the IBP algorithm with the ICBI method which is a two-step grid filling and an iterative correction of the interpolated pixels obtained by minimizing an objective function depending on the second-order directional derivatives of the image intensity. Experiment results increases the PSNR compared to other existing algorithms and also improves edge quality of the image considerably.
Several kinds of disperse-dye polymer films of the guest-host system were prepared by spin-coating method. Disperse orange 25 (DO25), disperse orange 3, disperse red 73, and disperse yellow 9 were chosen as nonlinear optical (NLO) active chromophores and polymethylmethacrylate (PMMA), polycarbonate (PC), and polyetherimide (PI) as polymer matrixes. Polymer films were poled by all optical poling or electric corona poling. The glass transition temperature (Tg), absorption spectra, rigidity, NLO properties of polymer films were characterized by means of DSC, UV-IR spectra, microhardness analyses, and NLO measurements. The all-optical poling characteristic of four kinds of NLO chromophores in PMMA matrixes systems has been investigated. DO25/PMMA has largest NLO effect. The possible explanation has been proposed. The relaxation and rigidity characteristics of DO25 doped polymer matrixes with various Tg have been studied by means of corona poling method. It is found that DO25/PI polymer films show best thermal and temporal stability and DO25/PMMA has largest NLO property. Generally, DO25/PC system has optimal tradeoff properties of NLO and stability. In addition, the second-order NLO coefficient and average electro-optic coefficient of 10wt% DO25/PMMA poled by optical poling and corona poling is determined to be around 60 and 34 pm/V, respectively.
BaTiO<sub>3</sub> (BT) nanocrystals doped polycarbonate polymer composite thin films (BT/PC) with different BT concentrations were prepared by spin coating method. Ultra-fine BT (~40-50 nm) nanocrystals with pure perovskite tetragonal phase were synthesized by hydrothermal method. The structure of BT nanocrystals and composite films were studied by means of XRD and TEM. The composite films were poled with a high electric field at a suitable temperature to yield a non-centrosymmetric arrangement and get better electro-optic properties. The Electro-optic (E-O) coefficients of composite films with various BT concentration were also evaluated. The average effective linear E-O coefficient and figure of merit of 20 wt% BT doped composite films were estimated to be 63.1 pm/V and 103.1 pm/V, respectively. The E-O properties of BT/PC composite films were further enhanced by increasing the concentration of the doped BT nanocrystals when the concentration of BT nanocrystals in composite films was low. The orientation degree of BT nanocrystals in PC polymer was detected by measuring the transparency spectra of unpoled and poled composite thin films.