多翼离心风机的气动噪声预测

针对目前不同型号的多翼离心风机采用降噪方法的不确定性,提出了一种基于非定常流场的多翼离心风机气动噪声分析方法,不需要直接求解声场却能为多翼离心风机降噪提供有用信息.对风机内部非定常流场进行计算,结合时域和频域方法对流场内静压脉动的强度和频率进行分析,根据声学基本理论,判定主要气动噪声源的位置及噪声类型.用该方法对某多翼离心风机进行计算,实验与理论分析的结果吻合良好.     

A method of image plane multiplex holography

A method for making image plane multiplex holograms is described. These exhibit the full 3-D imagery of conventional multiplex holograms, but can be made without the use of coherent light. A similarity to lenticular photography is noted; this similarity is then utilized in devising methods for constructing image plane multiplex holograms.     

旋转光楔多重全息术

本文提出一种新颖的多重全息术,它是利用旋转光楔调制平面参考波的传播方向,实现编码参考光记录获得多重全息图.该全息图经球面波再现,获得位于同一平面内的再现多重象.文中给出了这种方法的理论分析和实验结果,两者是吻合的.     

A simple extended source for high resolution holography

As a simple realization of an extended source in high resolution holography spheres made of homogeneous glass are treated experimentally and theoretically. A matrix of such glass balls has been used for producing point holograms for multiple imaging systems. Using spatially incoherent light in the imaging process, the squared absolute value of the autocorrelation function of the wave front in the focus of the spheres determines the image resolution. The measured resolution of about 1.5 μm agrees with the value expected from the measured and calculated autocorrelation width.     

漫反射全息摄影的一种简便方法

介绍了一种优化的全息摄影方法,实验中只用一块毛玻璃分光,光路简单,效果很好.     

Dynamic and multiplex holography with scanning Fabry-Pérot fringes

Suitably scanned Fabry-Pérot fringes were used to record and reconstruct a dynamic object. The technique can be used to increase the useful amplitude range of time averaged holography of moving objects and also as a convenient tool for multiplex holography.     

一种新的消色像全息术

本文从全息再现像的物像关系出发,对准像面情况下,像点随波长及参考光源扩展的变化进行了研究.阐明了利用散射线光源作参考光使全可见光范围内的像叠加在一起,产生消色像全息图的基本思想,并引入了消色像域的概念.考虑到点基元全息图尺寸及人眼瞳孔对成像光束的限制,白光再现时,可以获得清晰、明亮、具有一定景深和相当视场范围的消色再现像.     

一种新的真彩色彩虹全息术

本文提出了一种新的真彩色彩虹全息术称为三维物体的色编码重现技术,其特点是:利用单波长激光对三原色激光所记录的三维漫反射物体的菲涅耳全息图进行编码,从而可用单波长激光器在同一种记录介质上一次曝光记录三维物体的真彩色彩虹全息图。     

A simplified holography based superresolution system

In this paper we are proposing a simple idea based on holography to achieve superresolution. The object is illuminated by three fibers which maintain the mutual coherence between the light waves. The object in-plane rotation along with fiber-based illumination is used to achieve superresolution. The object in a 4f optical system is illuminated by an on-axis fiber to make the central part of the object׳s spectrum to the pass through the limiting square-aperture placed at the Fourier plane and the corresponding hologram of the image is recorded at the image plane. The on-axis fiber is switched off and the two off axis fibers (one positioned on the vertical axis and the other positioned on diagonal) are switched on one by one for each orientation of the object position. Four orientations of object in-plane rotation are used differing in angle by 90°. This will allow the recording of eight holographic images in addition to the one recorded with on-axis fiber. The three fibers are at the vertices of a right angled isosceles triangle and are aligned toward the centre of the lens following the fiber plane to generate plane waves for object illumination. The nine holographic images are processed for construction of object׳s original spectrum, the inverse of which gives the super-resolved image of the original object. Mathematical modeling and simulations are reported.     

A one-step patch near-field acoustical holography procedure

When performing holography measurements over a limited area of a source, the hologram pressure typically remains finite at the edge of the measurement aperture. Patch near-field acoustical holography (NAH) has been developed specifically to mitigate the effects related to that windowing. In iterative patch NAH, the source distribution is reconstructed in two steps: first, the partially measured sound field is extended iteratively, and then the extended pressure is projected onto the source surface by using conventional NAH procedures. In the present work, a one-step procedure for performing that combined task is described. In this approach, the acoustical property to be reconstructed on a surface of interest is related to the partially measured pressure on the hologram surface in terms of sampling and bandlimiting matrices, and the reconstructed result is obtained by finding the regularized least squares solution of the latter relation; a procedure for determining the cutoff wave number of the bandlimiting matrix without a priori knowledge of the signal bandwidth is suggested. The proposed procedure was validated by using a synthetic sound field created by a point-driven, simply supported plated.     

Stokes holography

A new technique, referred to as Stokes holography, is proposed and experimentally demonstrated for controlled synthesis of generalized Stokes parameters in 3D space using Stokes fringes. Stokes fringes are polarization fringes which permit to record and reconstruct complete wavefront. Full use of Stokes fringes in a single step is realized by scattering complex field and subsequently reconstructing using spatial averaging of the randomly scattered field. Mathematical formulations are derived and supported by experimental results of 3D object reconstruction in generalized Stokes parameters.