Ping Sun

Bio: Ping Sun is an academic researcher from Shandong Normal University. The author has contributed to research in topics: Speckle pattern & Interferometry. The author has an hindex of 3, co-authored 3 publications receiving 27 citations.

Spatial phase-shifting technique in large image-shearing electronic speckle pattern interferometry

Abstract: A technique for deformation measurement by carrier is pre- sented, which is based on large image-shearing shearography. A refer- ence object is fixed on the side of a test object. They are all illuminated by one expanded laser beam. When a large image-shearing Wollaston crystal is used in front of a charge-coupled device CCD camera, one image of the object is superposed by one image of the reference surface. The carrier can be introduced by tilting the reference surface at a small angle. When Fourier transform is used to demodulate the modulated fringe pattern, the phase of deformation can be calculated and the de- formation can be measured accurately. The principle of spatial carrier frequency modulation in large-shearing electronic speckle pattern inter- ferometry ESPI is discussed. A typical experiment using a centrally loaded clamped circular plate is completed. Some experimental results are presented. The experimental results prove that the method can modulate a speckle pattern very well and the displacement fields can be measured effectively. © 2007 Society of Photo-Optical Instrumentation

Three-dimensional displacement measurement by using reversed phase-shifting electronic speckle pattern interferometry

Abstract: A method for three-dimensional (3D) displacement measurement by separating out-of-plane displacement from in-plane displacement is presented. A reference beam is added to a dual-beam symmetric illumination electronic speckle pattern interferometry (ESPI) system and shared by the two illuminations. The test object is illuminated by the two object beams, respectively. Two phase maps, which include out-of-plane and in-plane displacement, can be obtained by phase-shifting techniques. In order to decrease electronic noises in the phase maps, one of the phase maps is calculated by the reversed phase-shifting method presented. By using inverse phase distribution, out-of-plane displacement can be easily separated from in-plane displacement by subtraction and can greatly decrease electronic noises. The principle of the method is presented and proved by a typical three-point bending experiment. Experimental results are offered.

Digital phase-shifting shearography for strain measurement by using a rotating platform system

Abstract: A phase-shifting technique for full-field measurement of the strain of an object in electronic speckle-shearing interferometry is pre- sented. The object under study is placed on a rotating platform and illuminated by an expanded laser beam. Its images are recorded at short intervals by a shearing CCD camera and stored directly into a computer. By subtracting the series of images from the first one, fringe patterns that represent the object surface strain can be obtained and shown on a computer monitor if the object is loaded. When the object is given a small angle of rotation, an additional phase will be introduced into the fringe patterns. Theoretical analysis shows that this additional phase is linear. Therefore, the electronic speckle shearing phase-shifting technique can be realized by rotating the test object. The small angle can be obtained exactly by a rotating platform controlled by a computer. The theory of the method and system as well as some experimental results is presented. © 2005 Society of Photo-Optical Instrumentation Engineers.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Tomographic phase microscopy

Abstract: The present invention relates to systems and methods for quantitative three-dimensional mapping of refractive index in living or non-living cells, tissues, or organisms using a phase-shifting laser interferometric microscope with variable illumination angle. A preferred embodiment provides tomographic imaging of cells and multicellular organisms, and time-dependent changes in cell structure and the quantitative characterization of specimen-induced aberrations in high-resolution microscopy with multiple applications in tissue light scattering.

Multichannel phase-stepped holographic interferometry

Abstract: A modified holographic interferometer is described which enables automatic fringe pattern analysis to be achieved when recording transient events. The introduction of a phase grating enables the method of phase-stepping fringe analysis to be applied to a wide range of measurement problems. The theory is developed, and an analysis of the sources of error is presented with the aid of computer simulations. Initial experimental results confirm the utility of the method and its potential application in pulsed laser holography. The method can in principle be applied to electronic speckle pattern interferometry.

Simple educational tool for digital speckle shearography

Abstract: In this study, an educational tool has been prepared for obtaining short-term and more economic training on digital speckle shearography (DSS). Shearography non-destructive testing (NDT) has gained wide acceptance over the last decade, providing a number of important and exciting inspection solutions in aerospace, electronics and medical device manufacturing. For exploring these motivations, it is important to develop didactic tools to understand the potential of digital shearography through training and didactic courses in the field of NDT. In this paper we describe a simple tool for making one familiar with the potential of DSS in the area of education and training. The system is realized with a simple and economic optical setup and a virtual instrument based on the LabVIEW™ and DAQ.