51 research outputs found

    Three-dimensional reconstruction of wafer solder bumps using binary pattern projection

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    As the electronic industry advances rapidly, the shrunk dimension of the device leads to more stringent requirement on process control and quality assurance. For instance, the tiny size of the solder bumps grown on wafers for direct die-to-die bonding pose great challenge to the inspection of the bumps' 3D quality. Traditional pattern projection method of recovering 3D is about projecting a light pattern to the inspected surface and imaging the illuminated surface from one or more points of view. However, image saturation and the specular nature of the bump surface are issues. This paper proposes a new 3D reconstruction mechanism for inspecting the surface of such wafer bumps. It is still based upon the light pattern projection framework, but uses the Ronchi pattern - a pattern that contrasts with the traditionally used gray level one. With the use of a parallel or point light source in combination with a binary grating, it allows a discrete pattern to be projected onto the inspected surface. As the projected pattern is binary, the image information is binary as well. With such a bright-or-dark world for each image position, the above-mentioned difficult issues are avoided. Preliminary study shows that the mechanism holds promises that existing approaches do not. © 2005 SPIE and IS&T.published_or_final_versio

    An illumination-invariant phase-shifting algorithm for three-dimensional profilometry

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    Image Processing: Machine Vision Applications V, Burlingame, California, USA, 22 January, 2012Uneven illumination is a common problem in real optical systems for machine vision applications, and it contributes significant errors when using phase-shifting algorithms (PSA) to reconstruct the surface of a moving object. Here, we propose an illumination-reflectivity-focus (IRF) model to characterize this uneven illumination effect on phase-measuring profilometry. With this model, we separate the illumination factor effectively, and then formulate the phase reconstruction as an optimization problem. To simplify the optimization process, we calibrate the uneven illumination distribution beforehand, and then use the calibrated illumination information during surface profilometry. After calibration, the degrees of freedom are reduced. Accordingly, we develop a novel illumination-invariant phase-shifting algorithm (II-PSA) to reconstruct the surface of a moving object under an uneven illumination environment. Experimental results show that the proposed algorithm can improve the reconstruction quality both visually and numerically. Therefore, using this IRF model and the corresponding II-PSA, not only can we handle uneven illumination in a real optical system with a large field of view (FOV), but we also develop a robust and efficient method for reconstructing the surface of a moving object. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).link_to_subscribed_fulltextpublished_or_final_versio

    Regularized multiframe phase-shifting algorithm for three-dimensional profilometry

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    In many industrial inspection systems, it is required to have a high-precision three-dimensional measurement of an object under test. A popular technique is phase-measuring profilometry. In this paper, we develop some phase-shifting algorithms (PSAs). We propose a novel smoothness constraint in a regularization framework; we call this the R-PSA method and show how to obtain the desired phase measure with an iterative procedure. Both the simulation and experimental results verify the efficacy of our algorithm compared with current multiframe PSAs for interferometric measurements.published_or_final_versio

    Height inspection of wafer bumps without explicit 3D reconstruction.

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    by Dong, Mei.Thesis (M.Phil.)--Chinese University of Hong Kong, 2007.Includes bibliographical references (leaves 83-90).Abstracts in English and Chinese.INTRODUCTION --- p.1Chapter 1.1 --- Bump Height Inspection --- p.1Chapter 1.2 --- Our Height Inspection System --- p.2Chapter 1.3 --- Thesis Outline --- p.3BACKGROUND --- p.5Chapter 2.1 --- Wafer Bumps --- p.5Chapter 2.2 --- Common Defects of Wafer Bumps --- p.7Chapter 2.3 --- Traditional Methods for Bump Inspection --- p.11BIPLANAR DISPARITY METHOD --- p.22Chapter 3.1 --- Problem Nature --- p.22Chapter 3.2 --- System Overview --- p.25Chapter 3.3 --- Biplanar Disparity Matrix D --- p.30Chapter 3.4 --- Planar Homography --- p.36Chapter 3.4.1 --- Planar Homography --- p.36Chapter 3.4.2 --- Homography Estimation --- p.39Chapter 3.5 --- Harris Corner Detector --- p.45Chapter 3.6 --- Experiments --- p.47Chapter 3.6.1 --- Synthetic Experiments --- p.47Chapter 3.6.2 --- Real image experiment --- p.52Chapter 3.7 --- Conclusion and problems --- p.61PARAPLANAR DISPARITY METHOD --- p.62Chapter 4.1 --- The Parallel Constraint --- p.63Chapter 4.2 --- Homography estimation --- p.66Chapter 4.3. --- Experiment: --- p.69Chapter 4.3.1 --- Synthetic Experiment: --- p.69Chapter 4.3.2 --- Real Image Experiment: --- p.74CONCLUSION AND FUTURE WORK --- p.80Chapter 5.1 --- Summary of the contributions --- p.80Chapter 5.2 --- Future Work --- p.81Publication related to this work: --- p.83BIBLIOGRAPHY --- p.8

    Automated optical inspection of solder paste based on 2.5D visual images

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    In this paper, a special technique for the inspection of solder paste using directional LED lighting is presented. Conventional optical inspection method would depend on an image acquired from a camera mounted from the top. This 2D inspection of solder paste based on images is fast but is limited to defect such as bridge or no solder. Defects related to the volume of the printed solder paste or unevenness of the paste cannot be treated from a top image. The developed technique of this paper would involve the use of special directional side lighting to acquire two-and-a-half dimensional (2.5D) images from above the solder paste block. A sequence of three images is acquired and image processing is carried out for defect detection of the printed solder paste. The acquired images would highlight the geometrical features of the solder paste block. Solder paste inspection is then carried out based on the highlighted features. The proposed method can handle other types of defects that cannot be treated by conventional top light images. ©2009 IEEE.published_or_final_versio

    3D inspection of wafer bump quality without explicit 3D reconstruction.

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    Zhao Yang.Thesis (M.Phil.)--Chinese University of Hong Kong, 2004.Includes bibliographical references (leaves 87-95).Abstracts in English and Chinese.Chapter 1 --- Introduction --- p.1Chapter 1.1 --- Objectives of the Thesis --- p.1Chapter 1.2 --- Wafer bumping inspection by using Biplanar Disparity approach --- p.2Chapter 1.3 --- Thesis Outline --- p.4Chapter 2 --- Background --- p.5Chapter 2.1 --- What is wafer bump? --- p.5Chapter 2.1.1 --- Common defects of wafer bump --- p.6Chapter 2.1.2 --- Literature review on exist wafer bump inspection method --- p.11Chapter 3 --- Model 1: the one camera model-Homography approach --- p.21Chapter 3.1 --- The introduction of the theoretical base of model 1 --- p.21Chapter 3.1.1 --- The objective of model 1 --- p.21Chapter 3.1.2 --- Desires --- p.22Chapter 3.1.3 --- Some background knowledge on Homography --- p.22Chapter 3.2 --- "Model 1- ""Pseudo Homography"" Approach" --- p.24Chapter 3.2.1 --- The description of the configuration of model 1 --- p.24Chapter 3.2.2 --- The condition of pseudo Homography --- p.25Chapter 3.2.3 --- The formation of pseudo Homgraphy H --- p.26Chapter 3.3 --- Methodology of treatment of the answer set --- p.32Chapter 3.3.1 --- Singular Value Decomposition-SVD --- p.32Chapter 3.3.2 --- The Robust Estimation --- p.33Chapter 3.3.3 --- Some experimental results by using manmade Ping Pang balls to test SVD[31] and Robust Estimation [24] --- p.35Chapter 3.3.4 --- the measurement of the Homography matrix answer set --- p.37Chapter 3.4 --- Preliminary experiment about model 1 --- p.43Chapter 3.5 --- Problems unsolved --- p.47Chapter 4 --- Model 2: the two camera model-Biplanar Disparity approach --- p.48Chapter 4.1 --- Theoretical Background --- p.48Chapter 4.1.1 --- the linearization of Homography matrix changes --- p.49Chapter 4.1.2 --- Problem Nature --- p.51Chapter 4.1.3 --- Imaging system setup --- p.52Chapter 4.1.4 --- Camera Calibration[13] --- p.52Chapter 4.2 --- Methodology --- p.54Chapter 4.2.1 --- Invariance measure --- p.54Chapter 4.2.2 --- The Geometric meaning of the Biplanar Disparity matrix --- p.58Chapter 4.3 --- RANSAC-Random Sample Consensus --- p.64Chapter 4.3.1 --- finding Homography matrix by using RANSAC[72] [35] --- p.64Chapter 4.3.2 --- finding Fundamental matrix by using RANSAC[73] [34] --- p.65Chapter 4.4 --- Harris Corner detection --- p.65Chapter 5 --- Simulation and experimental results --- p.67Chapter 5.1 --- Simulation experiments --- p.67Chapter 5.1.1 --- Preliminary experiments --- p.67Chapter 5.1.2 --- Specification for the synthetic data system --- p.71Chapter 5.1.3 --- Allowed error in the experiment --- p.71Chapter 5.2 --- Real images experiments --- p.72Chapter 5.2.1 --- Experiment instrument --- p.72Chapter 5.2.2 --- The Inspection Procedure --- p.74Chapter 5.2.3 --- Images grabbed under above system --- p.75Chapter 5.2.4 --- Experimental Results --- p.81Chapter 6 --- CONCLUSION AND FUTURE WORKS --- p.83Chapter 6.1 --- Summary on the contribution of my work --- p.83Chapter 6.2 --- Some Weakness of The Method --- p.84Chapter 6.3 --- Future Works and Further Development --- p.84Chapter 6.3.1 --- About the synthetic experiment --- p.84Chapter 6.3.2 --- About the real image experiment --- p.85Bibliography --- p.8

    MEMS Technology for Biomedical Imaging Applications

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    Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

    MME2010 21st Micromechanics and Micro systems Europe Workshop : Abstracts

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    Gratings: Theory and Numeric Applications

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    International audienceThe book containes 11 chapters written by an international team of specialist in electromagnetic theory, numerical methods for modelling of light diffraction by periodic structures having one-, two-, or three-dimensional periodicity, and aiming numerous applications in many classical domains like optical engineering, spectroscopy, and optical telecommunications, together with newly born fields such as photonics, plasmonics, photovoltaics, metamaterials studies, cloaking, negative refraction, and super-lensing. Each chapter presents in detail a specific theoretical method aiming to a direct numerical application by university and industrial researchers and engineers

    Tactile sensing of shape : biomechanics of contact investigated using imaging and modeling

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    Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2006.Includes bibliographical references (leaves 123-131).The overall goal of this research effort is to improve the understanding of the biomechanics of skin as it pertains to human tactile sense. During touch, mechanoreceptors beneath the skin surface are mechanically loaded due to physical contact of the skin with an object and respond with a series of neural impulses. This neural population response is decoded by the central nervous system to result in tactile perception of properties such as the shape, surface texture and softness of the object. The particular approach taken in this research is to develop a realistic model of the human fingertip based on empirical measurements of in vivo geometric and material properties of skin layers, so that the mechanical response of the fingertip skin to different shapes of objects in contact can be investigated, to help identify the relevant mechanism that triggers the mechanoreceptors in tactile encoding of object shape. To obtain geometric data on the ridged skin surface and the layers underneath together with their deformation patterns, optical coherence tomography (OCT) was used to image human fingertips in vivo, free of load as well as when loaded with rigid indenters of different shapes.(cont.) The images of undeformed and deformed finger pads were obtained, processed, and used for biomechanically validating the fingertip model. To obtain material properties of skin layers, axial strain imaging using high frequency ultrasound backscatter microscopy (UBM) was utilized in experiments on human fingertips in vivo to estimate the ratio of stiffnesses of the epidermis and dermis. By utilizing the data from OCT and UBM experiments, a multilayered three dimensional finite element model of the human fingertip composed of the ridged fingerpad skin surface as well as the papillary interface between the epidermis and dermis was developed. The model was used to simulate static indentation of the fingertip by rigid objects of different shapes and to compute stress and strain measures, such as strain energy density (SED), and maximum compressive or tensile strain (MCS, MTS), which have been previously proposed as the relevant stimuli that trigger mechanoreceptor response.(cont.) The results showed that the intricate geometry of skin layers and inhomogeneous material properties around the locations of the SA-I and RA mechanoreceptors caused significant differences in the spatial distribution of candidate relevant stimuli, compared with other locations at the same depths or the predictions from previous homogeneous models of the fingertip. The distribution of the SED at the locations of SA-I mechanoreceptors and the distribution of MCS/MTS at the locations of RA mechanoreceptors under indentation of different object shapes were obtained to serve as predictions to be tested in future biomechanical and neurophysiological experiments.by Wan-Chen Wu.Ph.D
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