Watermarks encrypted in the cascaded Fresnel digital hologram

A cascaded Fresnel digital hologram (CFDH) is proposed, together with its mathematical derivation. Its application to watermarking has been demonstrated by a simulation procedure, in which the watermark image to be hidden is encoded into the phase of the host image. The watermark image can be deciphered by the CFDH setup, the reconstructed image shows good quality and the error is almost closed to zeros. Compared with previous technique, this is a lensless architecture, which minimizes the hardware requirement.     

Automatic fringe analysis of two-beam interference patterns for measurement of refractive index and birefringence profiles of fibres

Automatic fringe pattern analysis is a powerful and inexpensive digital image-processing technique. Two-beam polarizing interference Pluta microscope [Pluta M. Opt Acta 1971;18:661, Pluta M. J Microsc 1972;96:309] is automated by the computer-aid via CCD camera and digital frame grabber. Software program is prepared to deal with the duplicated (separated and overlapped) Microinterferograms produced by two-beam polarizing microscope. It also gives an accurate and fast automatic measurement of refractive index and birefringence profiles for fibres. In this paper, the refractive index and birefringence profiles of two different types of fibres, basalt and polypropylene (PP) fibres are presented. A new method to determine the birefringence profile of fibres from non-duplicated microinterferogram is suggested. The cold drawing process for PP fibres is studied.     

宽视场长焦距离轴三反射镜光学系统的设计

分析了离轴三反射镜系统成像特性．根据共轴三反射镜光学系统像差理论，确定结构参数的基本计算公式．设计了长焦宽视场的离轴三反射镜光学系统，分析了系统结构参量对像差的影响．结果表明，该系统视角较大，地面复益范围较宽，成像质量接近衍射极限．     

基于微分算子的边缘检测法在基因芯片图像识别中的应用

一种基于梯度算子和拉普拉斯算子检测医学基因芯片荧光数字图像边缘的方法．数字图像经过图像增强等预处理以后，突出了我们感兴趣的数字图像特征，根据数字图像灰度变化的趋势，用灰度变化的一阶导数(梯度算子)检测图象中的边缘区域；用灰度变化的二阶导数确定图像边缘的中心位置．最后根据某些预定的准则把满足这些准则的象素组成一条边缘．     

A modification for the mask-filtering approach by superposing anisotropic derivatives in an image

We demonstrate a novel method to modify the mask-filtering approach by enlarging the gray-level difference of any two nearby pixels in an image. Derivatives are calculated in different directions respectively instead of isotropically. Some higher spatial frequencies are then selectively magnified. The final image has better sharpened fine characteristics than that enhanced by the conventional technique.     

Non-coherent noise reduction in digital holography based on root mean square technique

In this paper, the root mean square (rms) technique is applied in order to reduce the non-coherent noise in phase-contrast image. The proposed technique is applied to a sample of 200 μm step height nominally. The recorded off-axis interferograms generated from two different wavelengths are processed to obtain an object wave (amplitude and phase) for each wavelength separately. The independent phase maps are subtracted and a phase map for the beat-wavelength is obtained and converted to height map. The rms values of 10 pixels profiles from the obtained height map are calculated automatically to show the three-dimensional (3D) profile. The experimental results show that the non-coherent noise is reduced by the order of 90% when the rms technique is applied and the uncertainty in measurement has been found to be of the order of 1.5 μm. The proposed technique can provide a simple and real solution for measuring 3D objects having high abrupt height difference.     

射线成像检测中射线源焦点的影响及修正

本文分析了在工业无损检测中射线源焦点对成像质量的影响，讨论了射线源焦点对成像影响的数学模型，以此为基础，设计了相应的焦点修正算法，并给出了处理结果     

Closed-form solutions for a mode III radial matrix crack penetrating a circular inhomogeneity

In this research we address in detail a mode III radial matrix crack penetrating a circular inhomogeneity. One tip of the radial crack lies in the matrix, while the other tip of the radial crack lies in the circular inhomogeneity. In addition the two tips of the crack are mutually image points (or inverse points) with respect to the circular inhomogeneity-matrix interface. First we conformally map the crack onto a unit circle C_a in the new ζ-plane. Meanwhile the inhomogeneity-matrix interface is mapped onto C_b, a part of another circle in the ζ-plane. In addition C_a and C_b intersect at a vertex angle π/2. By using the method of image in the ζ-plane, closed-form solutions in terms of elementary functions are derived for three loading cases: (1) remote uniform antiplane shearing; (2) a screw dislocation located in the unbounded matrix; and (3) a radial Zener–Stroh crack.     

A.第十九届国际高速摄影和光子学会议概况

本文对第19届国际高速摄影与光子学会议做了简介,主要谈到了光机式相机、高速视频技术、全息和干涉计量。     

磁场渗透导体壳的实验研究

本文叙述了测量阶跃脉冲垂直磁场和水平磁场渗透HL-1装置各种比例导体壳时间常数的方法。对空芯和铁芯变压器情况分别做了实验。给出了相应结果。