Double phase-image encryption using gyrator transforms,and structured phase mask in the frequency plane

Fully-phase image encryption is considered more secure as compared to an amplitude image encryption. In the present paper, an encryption scheme is proposed for double phase-images. The phase-images are bonded with random phase masks and then gyrator transformed. The two resulting images are then added and subtracted to give intermediate images which are bonded with a structured phase mask (SPM) based on devil’s vortex Fresnel lens (DVFL) in the frequency plane. Thereafter, the images are once again transformed using a gyrator transform (GT) to give the corresponding encrypted images. The use of a structured phase mask enhances the key space for encryption and also overcomes the problem of axis alignment associated with an optical set-up. The decryption process is the reverse of encryption. The validity of the proposed scheme is established from the computer simulation results using MATLAB 7.1 platform. The performance of the scheme is evaluated in terms of mean-squared-error (MSE) between the input-, and the decrypted images. In addition, the sensitivity to encryption keys such as SPM parameters, and transform angles of GT is investigated. The technique is likely to provide enhanced security in view of the increased number of encryption parameters. Robustness of the system against occlusion and noise attacks has also been investigated.     

Characterization of some convergent bivariate subdivision schemes with nonnegative masks

Knowing that the convergence of a multivariate subdivision scheme with a nonnegative mask can be characterized by whether or not some finite products of row-stochastic matrices induced by this mask have a positive column. However, the number of those products is exponential with respect to the size of matrices. For nonnegative univariate subdivision, this problem is completely solved. Thus, the convergence in this case can be checked in linear time with respect to the size of a square matrix. This paper will demonstrate the necessary and sufficient conditions for the convergence of some nonnegative bivariate subdivision schemes by means of the so-called connectivity of a square matrix, which is derived by a given mask. Moreover, the connectivity can be examined in linear time with respect to the size of this matrix.     

Preparation of Self-Organized Porous Polymer Masks for Si Dry Etching

Summary: Self-organized honeycomb-patterned polymer films were prepared by using condensed water droplet arrays as templates. Porous polymer masks for dry etching were easily prepared on Si substrates by peeling off the honeycomb-patterned films. After dry etching, hexagonally-arranged micro-pores were formed on the surface of Si substrates.     

Algebraic Properties of Subdivision Operators with Matrix Mask and Their Applications

Subdivision operators play an important role in wavelet analysis. This paper studies the algebraic properties of subdivision operators with matrix mask, especially their action on polynomial sequences and on some of their invariant subspaces. As an application, we characterize, under a mild condition, the approximation order provided by refinable vectors in terms of the eigenvalues and eigenvectors of polynomial sequences of the associated subdivision operator. Moreover, some necessary conditions, in terms of nondegeneracy and simplicity of eigenvalues of a matrix related to the subdivision operator for the refinable vector to be smooth are given. The main results are new even in the scalar case     

A novel method of high resolution imaging through random perturbation wave front

A novel method is proposed for eliminating the effect of the traditional optical aberration on high resolution imaging by random perturbation wave front and digital image processing. A random phase mask, whose phase spectrum fluctuation is accordant with Kolmogorov distribution, is positioned near the aperture stop of optical system, making the optical aberration image become random perturbation image, that is, the intermediate image. The blind deconvolution algorithm based on maximum-likelihood estimation technique is used to restore the intermediate image acquired by a digital detector. The effects of optical aberrations and the noise on the restoration image are explored. To demonstrate the validity of the method proposed, the computer simulation and laboratory experiments are carried out for the imaging of the optical system with primary aberration. The results have shown that the present method is well suited for effectively improving the imaging quality of the optical system with certain aberration, thus making the optical system resolution close to or reach the diffraction-limit of the optical system.     

组合化学在功能材料合成方面的应用

组合化学方法是当今材料科学和化学领域的研究热点。组合化学方法首先在新药的合成领域得到应用, 很快就以其合成周期短、合成的样品数量大、节约经费等诸多优点而拓展到功能材料的合成等其它领域。组合化学的方法有许多种, 按照反应相的不同可以分为液相中的组合合成法和固相中的组合合成法, 固相组合合成又可以根据所选用的掩模方式的不同而分为二分阴影掩模法、四分阴影掩模法、可移动百叶窗式掩模法等几种, 可以根据材料合成的实际需求加以选择。     

基于快速傅里叶变换的实时相移校正算法

在相移测量剖面术（ＰＭＰ）中,提出了一种基于快速傅里叶变换的相移校正算法,利用最初多采的一幅条纹图的信息和傅里叶变换调制度模板,快速地计算出当前的相移值。采用该算法,能实时准确地控制投影光栅的移动,大大提高了测量系统的工和自动化程度,具有极大的实用价值。     

一种新颖的取样光纤光栅振幅版的研制

提出了一种新颖的用于制作取样光纤光栅的取样振幅版的设计方案，其特点是具有渐变的取样周期和不变的占空比，利用这种振幅版可以简单灵活地制作出反射峰波长间隔不同的取样光栅梳状滤波器，有利于提高取样光栅的制作灵活性并降低成本.对这种方法可能存在的不足也进行了分析.利用制作出的取样光栅，基于全光纤结构实现了具有游标尺式波长调谐机理的可选波长光纤激光器.     

Fabrication of GaAs hole array as a 2D-photonic crystal and their application to photonic bandgap waveguide

A two dimensional (2D) GaAs hole array with a high aspect ratio was successfully fabricated by dry etching techniques using a highly ordered alumina membrane as a mask. The reflection spectra of the GaAs hole array shows characteristics of the photonic bandgap (PBG) calculated by using the 2D triangular lattice structure. Various defect lines were formed etching in the GaAs hole array using focused ion beam. The defect-type PBG waveguide was experimentally demonstrated.