Fractional Fourier plane image encryption technique using radial hilbert-, and Jigsaw transform

A new method for image encryption using integral order radial Hilbert transform (RHT) filter in the fractional Fourier transform (FRT) domain has been proposed. The technique is implemented using the popular double random phase encoding method in the fractional Fourier domain. The random phase masks (RPMs), integral orders of the RHT, fractional orders of FRT, and indices of the Jigsaw transform (JT) have been used as keys for encryption and decryption. Simulation results have been presented and the schematic representation for optical implementation has been proposed. The mean-square-error and signal-to-noise ratio between the decrypted image and the input image have been calculated for the correct as well as incorrect orders of the RHT. Effect of occlusion and noise on the performance of the proposed scheme has also been studied. The robustness of the technique has been verified against attack using partial windows of the correct random phase masks. Similar investigations have also been carried out for the chosen-, and the known-plain-text attacks.     

Binary phase only filters for rotation and scale invariant pattern recognition with the joint transform correlator

The joint transform correlator (JTC) is one of the two main optical image processing architecture which provides a highly effective way of comparing images in a wide range of applications. Traditionally, an optical correlator is used to compare an unknown input scene with a pre-captured reference image library, to detect if the reference occurs within the input. Strength of the correlation signal decreases rapidly as the input object rotates or varies in scale relative to the reference object. The aim of this paper is to overcome the intolerance of the JTC to rotation and scale changes in the target image. Many JTC systems are constructed with the use of ferroelectric liquid crystal (FLC) spatial light modulators (SLMs) as they provide fast two-dimensional binary modulation of coherent light. Due to the binary nature of the FLC SLMs used in the JTC systems, any image addressed to the device need to have some form of thresholding. Carefully thresholding the grey scale input plane and the joint power spectrum (JPS) has significant effect on the quality of correlation peaks and zero order (DC) noise. A new thresholding technique to binarise the JPS has been developed and implemented optically. This algorithm selectively enhances the desirable fringes in the JPS which provide correlation peaks of higher intensity. Zero order noise is further reduced when compared to existing thresholding techniques.Keeping in mind the architecture of the JTC and limitations of FLC SLMs, a new technique to design rotation and scale invariant binary phase only filters for the JTC architecture is presented. Filers design with this technique have limited dynamic range, higher discriminability among target and non-target objects, and convenience for implementation on FLC SLMs. Simulation and experiments shows excellent results of various rotation and scale invariant filters designed with this technique. A rotation invariant filter is needed for various machine vision applications of the JTC. By fixing the distance between camera and input object, the scale sensitivity of the correlator can be avoided. In contrast to the industrial machine vision applications, scale factor is very important factor for the applications of the JTC systems in defence and security. A security system using a scale invariant JTC will be able to detect a target object well in advance and will provide more time to take a decision.     

Polarization and image rotation induced by a rotating dielectric rod: an optical angular momentum interpretation

When light is transmitted along the axis of a rotating glass rod, the polarization of the light is rotated through a small angle [Proc. R. Soc. London, Ser. A349, 423 (1976)]. Under the same conditions, we predict a rotation of the transmitted image by exactly the same angle. The treatment of the two effects in terms of light's spin and orbital angular momentum suggests that they share a common origin.     

Rapid and robust medical image elastic registration using mean shift algorithm

In landmark-based image registration, estimating the landmark correspondence plays an important role. In this letter, a novel landmark correspondence estimation technique using mean shift algorithm is proposed. Image corner points are detected as landmarks and mean shift iterations are adopted to find the most probable corresponding point positions in two images. Mutual information between intensity of two local regions is computed to eliminate mis-matching points. Multi-level estimation (MLE) technique is proposed to improve the stability of corresponding estimation. Experiments show that the precision in location of correspondence landmarks is exact. The proposed technique is shown to be feasible and rapid in the experiments of various mono-modal medical images.     

Double image encryption by using Arnold transform and discrete fractional angular transform

Based on Arnold transform and discrete fractional angular transform, a double image encryption algorithm is designed. Two original images are regarded as the amplitude and phase of a complex function. Arnold transform is introduced for scrambling the pixels at a local area of the complex function. Subsequently the changed complex function is converted by discrete fractional angular transform. The operations mentioned will be performed many times. The amplitude of final output complex function is the encrypted image and its phase is regarded as the key of encryption algorithm. The parameters of the two transforms serve as the additional keys for enhancing the security. Some numerical simulations have been done to validate the performance of this encryption scheme.     

Low-coherent light-source angular interferometer using a square prism and the angular-scanning technique

An interferometer based on using low-coherent light source, a square prism, and the angular-scanning technique is proposed for absolute angular-displacement determinations. An angular displacement of the square prism shifts the correlogram, which is modulated by an envelope function, of the interference signal of the beams passing through the prism. This angle can thus be discovered by detecting the shifting of the envelope peak. A setup constructed to validate the interferometer is used. The results of using this setup are then presented.     

Broadband light source shearing interferometer using Savart plate and angular scanning technique

A shearing interferometer based on using broadband light source, Savart plate, and angular scanning technique is proposed for slope contour measurements in this Letter. Of which, the Savart plate divides the wavefront reflected from the detected surface into two laterally displaced ones, the interference pattern generated by the interference of the divided wavefronts is modulated by an envelope function, and the slope contour of the detected surface is determined by examining the shifting of the darkest fringe as the shear plate is angularly scanned. A setup for realizing the interferometer is constructed. The experimental results of using this setup agree the validity and feasibility of the proposed interferometer.     

Color image edge detection method using VTV denoising and color difference

The traditional Canny edge uses Gaussian filter to suppress the noise, it also smoothes out the image edges. An improved Canny edge detection method for color image is proposed in this paper, the improved method uses fast vectorial total variation (VTV) minimization model to remove noise in color image, and then calculates the color difference and direction in CIELAB color space, which is used for non-maximal suppression. Finally, the improved method extracts the edges by the double-threshold method. The experimental results show that the proposed method achieves better performance than the traditional Canny edge detector. It can remove noise while preserving the image edges, and effectively detect the image edges.     

聚氨酯结构与径向分布的分子动力学模拟

采用分子动力学方法计算得到DHI-乙烯醇聚合体系统的结构和径向分布函数。讨论了系统结构和径向分布函数与温度和压力之间的关系。结果表明粘合系统的空间分布一般地随着温度和压力的增加而收窄,对增加聚氨酯系统的粘合性具有积极的意义。     

聚氨酯结构与径向分布的分子动力学模拟

采用分子动力学方法计算得到DHI-乙烯醇聚合体系统的结构和径向分布函数.讨论了系统结构和径向分布函数与温度和压力之间的关系.结果表明粘合系统的空间分布一般地随着温度和压力的增加而收窄,对增加聚氨酯系统的粘合性具有积极的意义.     

Optical torque wrench: angular trapping, rotation, and torque detection of quartz microparticles

We describe an apparatus that can measure the instantaneous angular displacement and torque applied to a quartz particle which is angularly trapped. Torque is measured by detecting the change in angular momentum of the transmitted trap beam. The rotational Brownian motion of the trapped particle and its power spectral density are used to determine the angular trap stiffness. The apparatus features a feedback control that clamps torque or other rotational quantities. The torque sensitivity demonstrated is ideal for the study of known biological molecular motors.     

Rotation, scaling, and translation invariant local watermarking technique with Krawtchouk moments

A rotation, scaling, and translation invariant local watermarking is proposed with one or two Krawtchouk moment(s) of the original to estimate the geometric distortion parameters including rotation angle, scaling factor, and translation parameter. Krawtchouk moments can be used as private key of watermark extractor.Watermark is inserted into perceptually significant Krawtchouk moments of original, and watermark based on Krawtchouk moments is local. Independent component analysis (ICA) is utilized to extract watermark blindly. Experimental results show that this method has a good robustness against distortions preformed by watermark benchmark Stirmark.     

Rheology of polymer suspensions: II. Translation,rotation and viscosity

The theory of average local velocity fields developed in the preceding article is applied to a suspension of spherically symmetric polymers. Three transport properties of the suspension are analyzed, namely the concentration dependence of the translational and rotational friction coefficient of a polymer, and the concentration dependence of the viscosity of the solution.     

Coupled waves of linear velocity,angular velocity,and temperature in a liquid with internal rotation

Equations of motion for a locally nonequilibrium liquid with internal rotation are derived, and the thermospin effect is considered. It is demonstrated that high-frequency transverse coupled waves of linear velocity, angular velocity of internal rotation, and temperature may propagate a liquid with internal rotation. A dispersion relation and a frequency dependence of the damping ratio are deduced. Comparison between theoretical and experimental values of the transverse sound velocity dispersion shows their satisfactory agreement. Low-frequency transverse waves do not penetrate into the liquid: they decay over a distance on the order of the wavelength. It is shown that frequencies and their corresponding wavenumbers exist in a liquid with internal rotation at which either waves do not decay or a phase shift in the skin layer is absent. It is found that the excitation spectrum may contain a cutoff frequency or an energy gap due to interaction between the linear and angular velocity fields. The dispersion and damping ratio for the coupled waves near synchronism points, where uncoupled waves resonantly interact with each other, are determined.     

Digital image correlation in experimental mechanics and image registration in computer vision: Similarities,differences and complements

Digital image correlation and image registration or matching are among the most widely used techniques in the fields of experimental mechanics and computer vision, respectively. Despite their applications in separate fields, both techniques primarily involve detecting the same physical points in two or more images. In this paper, a brief technical comparison of the two techniques is reviewed, and their similarities and differences as well as complements are presented. It is shown that some concepts from the image registration or matching technique can be applied to the digital image correlation technique to substantially enhance its performance, which can help broaden the applications of digital image correlation in scientific research and engineering practice.     

Poloidal rotation dynamics, radial electric field, and neoclassical theory in the jet internal-transport-barrier region

Results from the first measurements of a core plasma poloidal rotation velocity (upsilontheta) across internal transport barriers (ITB) on JET are presented. The spatial and temporal evolution of the ITB can be followed along with the upsilontheta radial profiles, providing a very clear link between the location of the steepest region of the ion temperature gradient and localized spin-up of upsilontheta. The upsilontheta measurements are an order of magnitude higher than the neoclassical predictions for thermal particles in the ITB region, contrary to the close agreement found between the determined and predicted particle and heat transport coefficients [K.-D. Zastrow, Plasma Phys. Controlled Fusion 46, B255 (2004)]. These results have significant implications for the understanding of transport barrier dynamics due to their large impact on the measured radial electric field profile.     

Dissipative chaotic quantum maps: Expectation values, correlation functions and the invariant state

I investigate the propagator of the Wigner function for a dissipative chaotic quantum map. I show that a small amount of dissipation reduces the propagator of sufficiently smooth Wigner functions to its classical counterpart, the Frobenius-Perron operator, if . Several consequences arise: the Wigner transform of the invariant density matrix is a smeared out version of the classical strange attractor; time dependent expectation values and correlation functions of observables can be evaluated via hybrid quantum-classical formulae in which the quantum character enters only via the initial Wigner function. If a classical phase-space distribution is chosen for the latter or if the map is iterated sufficiently many times the formulae become entirely classical, and powerful classical trace formulae apply. Received 7 October 1999     

Quantized Knizhnik-Zamolodchikov equations,quantum Yang-Baxter equation,and difference equations forq-hypergeometric functions

Thes₂ quantized Knizhnik-Zamolodchikov equations are solved inq-hypergeometric functions. New difference equations are derived for generalq-hypergeometric functions. The equations are given in terms of quantum Yang-Baxter matrices and have the form similar to quantum Knizhnik-Zamolodchikov equations for quantum affine algebras introduced by Frenkel and Reshetikhin.This work was supported by NSF grant DMS-9203929.     

Coherent optical methods of pattern recognition and scene analysis using the correlation function of invariant image description

An approach is described to the development of a hybrid optodigital system of pattern recognition and scene analysis, based on a correlation procedure of comparing the initial image (object, scene) with the result of its geometric transformation. It is shown that the correlation function obtained through this procedure for describing the objects of a scene makes it possible to distinguish attributes (tags) that are invariant to the scale and orientation of the objects, and contains information on their location in the analyzed scene. Algorithms are developed for the determination of the coordinates of objects when a scene is segmented, for formation of a set of attributes by using an instructive group of images, and also for distinguishing these attributes for all objects contained in the scene. The possibility of determining the coordinates of objects (outlines of parts of instruments, printed letters, particle tracks in dielectric detectors) and their identification by means of a correlation procedure is demonstrated by computer simulation and in experimental systems of coherent-optics correlators with liquid-crystal space and time modulators of light in the Fourier plane.