Gordon M. Brown

Bio: Gordon M. Brown is an academic researcher. The author has contributed to research in topics: Noise, vibration, and harshness & Noise. The author has an hindex of 5, co-authored 5 publications receiving 1505 citations.

Overview of three-dimensional shape measurement using optical methods

Abstract: We first provide an overview of 3-D shape measurement us- ing various optical methods. Then we focus on structured light tech- niques where various optical configurations, image acquisition tech- niques, data postprocessing and analysis methods and advantages and limitations are presented. Several industrial application examples are presented. Important areas requiring further R&D are discussed. Finally, a comprehensive bibliography on 3-D shape measurement is included, although it is not intended to be exhaustive. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)00101-X)

Guest Editorial: Special Section on Optical Methods for Shape Measurement

Abstract: In industry, there is a need for accurately measuring the 3-D shape of objects to speed up and ensure product development and manufacturing quality. There are a variety of applications of 3-D shape measurement, such as: control for intelligent robots, obstacle detection for vehicle guidance, dimension measurement for die development, stamping panel geometry checking, and accurate stress/ strain and vibration measurement. Moreover, automatic online inspection and recognition issues can be reduced to the 3-D shape measurement of, for example, body panel paint defects and dent inspection. The principles of triangulation, structured light, and interferometry have been in existence for decades. However, it is only with the recent availability of advanced and low cost computers, electro-optical elements, and lasers that such techniques have reached the breakthrough point to be commercialized, and ever increasingly be applied in industry. To make it even more acceptable in industry and to strive to achieve 10 to 10 accuracy, there are still some challenges that need to be addressed, such as: the shading issue, the specular surface headache, accurate data patching from different view directions, geometric parameter determination and calibration, absolute phase measurement, local and global coordinates tracking and transforming, real-time computing, sensor planing, and optimization. This special section is designed to promote research activity and to serve as a forum both for academia and industry. This special section includes a variety of development and application examples such as: optimization of an optical system which results in one part in 20,000 accuracy, new techniques using a diffraction grating or defocus to overcome the shading issue, direct digital wavefront reconstruction combined with wavelength scanning to attack the absolute phase measurement issue, and develop-

Minimizing vehicle noise and weight using panel acoustic contribution analysis

Abstract: Panel acoustic contribution analysis (PACA) is an advanced engineering tool to improve noise, vibration, and harshness quality and minimize weight of vehicles. It is a technique to categorize areas of ve- hicle body panels as positive (sound level increases as vibration ampli- tude increases), negative or neutral according to their contribution to the total sound. PACA is a hybrid of computer aided engineering and experi- mental methods. Computer aided holometry (CAH), scanning laser ve- locimetry (SLV), or an accelerometer net is used to experimentally mea- sure structure vibration complex velocities. These velocities are the boundary conditions for a boundary element model of the acoustic cav- ity. Boundary element analysis is then used to predict the vehicle interior sound and calculate panel acoustic contributions. Experimental results for a welded steel box (validation) and vehicle application are presented.

Recent advances in brake noise and vibration engineering using laser metrology

Abstract: Noise, vibration, and harshness (NVH) can be predominate brake noise described as roughness/judder, brake creep groan, and brake squeal, all of which are important issues and concerns for customer satisfaction in the automotive industry. Brake roughness and groan are low-frequency vibration and noise, while brake squeal is a high-frequency noise. These have been the challenging issues for engineers and researchers for many years due to their complex nature that involves multiple disciplines such as nonlinear dynamics, contact mechanics, and tribology or nanotribology. As in the body/chassis and power-train arena, laser metrology can be uniquely applied in brake NVH to shed light on this complex issue. Engineers can gain insight on NVH fundamental root causes and provide guidance for optimal design resolution. We provide some examples that illustrate the recent progress and novel applications of holographic interferometry, pulsed laser holographic interferometry, pulsed laser electronic speckle pattern interferometry, and laser Doppler vibrometry methodology to identify the root causes of brake concerns and verify engineering solutions.

Nonlinear structured-illumination microscopy: Wide-field fluorescence imaging with theoretically unlimited resolution

Abstract: Contrary to the well known diffraction limit, the fluorescence microscope is in principle capable of unlimited resolution. The necessary elements are spatially structured illumination light and a nonlinear dependence of the fluorescence emission rate on the illumination intensity. As an example of this concept, this article experimentally demonstrates saturated structured-illumination microscopy, a recently proposed method in which the nonlinearity arisesfromsaturationoftheexcitedstate.Thismethodcanbeused in a simple, wide-field (nonscanning) microscope, uses only a single, inexpensive laser, and requires no unusual photophysical properties of the fluorophore. The practical resolving power is determined by the signal-to-noise ratio, which in turn is limited by photobleaching. Experimental results show that a 2D point resolution of <50 nm is possible on sufficiently bright and photostable samples.

Review of 20 years of range sensor development

Abstract: We review 20 years of development in the field of 3-D laser imaging. An overview of 3-D digitizing techniques is presented with an emphasis on commercial techniques and systems currently available. It covers some of the most important methods that have been developed, both at the National Research Council of Canada (NRC) and elsewhere, with a focus on commercial systems that are considered good representations of the key technologies that have survived the test of years. © 2004 SPIE and IS&T.

Analysis of the Accuracy and Robustness of the Leap Motion Controller

Abstract: The Leap Motion Controller is a new device for hand gesture controlled user interfaces with declared sub-millimeter accuracy However, up to this point its capabilities in real environments have not been analyzed Therefore, this paper presents a first study of a Leap Motion Controller The main focus of attention is on the evaluation of the accuracy and repeatability For an appropriate evaluation, a novel experimental setup was developed making use of an industrial robot with a reference pen allowing a position accuracy of 02 mm Thereby, a deviation between a desired 3D position and the average measured positions below 02mmhas been obtained for static setups and of 12mmfor dynamic setups Using the conclusion of this analysis can improve the development of applications for the Leap Motion controller in the field of Human-Computer Interaction