Showing papers in "Optics and Lasers in Engineering in 2007"

TL;DR: Two algorithms, one based on filtering and the other based on similarity measure, are developed and some applications based on these two algorithms are explored, including strain determination, phase unwrapping, phase-shifter calibration, fault detection, edge detection and fringe segmentation.

TL;DR: In this paper, the authors investigated the effect of subset size, associated with image pattern quality and subset displacement functions, on the accuracy of deformation measurements by digital image correlation (DIC).

TL;DR: In this article, a 3D transient numerical approach for modeling the multilayer laser solid free-form fabrication (LSFF) process is presented, where coupled thermal and stress domains are numerically obtained assuming a decoupled interaction between the laser beam and powder stream.

TL;DR: This paper provides algorithms for 3D surface reconstruction to process the raw data and deliver detail preserving 3D models that possess accurate depth information for characterization and visualization of cracks as a significant improvement over contemporary commercial video-based vision systems.

TL;DR: In this paper, the influence of the laser beam position, with respect to the joint, on weld characteristics was investigated, and the results of various tests and examinations enabled definition of the best position for the incident laser beam with respect on the joint for welding together the two stainless steels.

TL;DR: In this paper, a multi-pulse laser ablation of silver in deionized water was studied, where the laser beams were arranged in a cross-beam configuration, and two levels of the laser fluences were used for the ablating beam: 0.09 and 0.265.

TL;DR: A detailed investigation of the effect of ambient pressure in the range of 0.1 to 1.0 atm on the size, temperature, electron number density, and fraction of laser energy absorbed in a laser-induced plasma in air has been conducted in this paper.

TL;DR: In this article, a whole-field method for automatic determination of the isoclinic parameter φ in photoelasticity is presented. And the results show that the method permits the reliable isochromic parameter to be determined in the true phase interval with almost no defects of the wasochromatic parameter.

TL;DR: In this article, the authors reviewed the recent progress in surface measurement methods using active vision and light-scattering techniques and proposed an integrative method to measure surface waviness and form, roughness.

TL;DR: An improved method for measuring displacement in digital speckle correlation technology, which is based on an iterative and spatial-gradient algorithm, is developed in this paper, where both finite element method and 2D generalized cross-validation (GCV) algorithm are adopted for smoothing the displacement field, and then the strain field can be obtained from the smoothed displacement field.

TL;DR: In this article, the authors evaluated the suitability of PDIA for quantitative measurements in moderately dense spray and in particular the potential capability for the characterisation of small diameter, high-speed two-phase flows by employing high intensity pulsed lasers for illumination.

TL;DR: It was observed that WFD performs better than FD and GFD technique, and the effect of the noise on the retrieval and classification of shapes of different objects, additive and multiplicative noise of various variances were applied.

TL;DR: This work determined 3D strain distributions using a mouse femur in response to a knee loading modality as a model system and built an advanced DSPI system and integrated local contour information to deformation data.

TL;DR: A classification system for the steps in the measurement process is proposed and allows the development of a unified approach to diagnostic testing of components or sub-systems in an optical system for strain measurement based on any optical technique.

TL;DR: Using active and programmable focal-spot shaping, the authors demonstrate direct femtosecond laser micro-structuring of materials, and perform surface marking as well as drilling with user-defined geometrical shapes of small dimensions.

TL;DR: In this article, the fundamental concept of the advanced iterative algorithm is reviewed and a detailed procedure for implementation is presented, and computer simulations are conducted to evaluate its performance for truly random phase-shifted interferograms with intra-and inter-frame intensity variations.

TL;DR: A novel segmental calibration approach, i.e., dividing the whole work range into two parts and calibrating, respectively, with corresponding system parameters, is proposed to effectively improve the measurement accuracy of the large depth-of-view 3D laser scanner.

TL;DR: In this paper, an optical measurement system based on laser spectroscopy has been applied to measure not only the basic components of the product gas (H2, CH4, CO, CO2, H2O), but also gives information concerning the content of high hydrocarbons, the so-called tars, in product gas.

TL;DR: It is shown that a path which follows the maximum modulus of the CWT (the wavelet ridge) gives the instantaneous fringe frequency as a function of spatial displacement.

TL;DR: In this article, a comparison between continuous (CW) and time-shared (TS) multiple optical tweezers applied to the study of the interaction between a single motor protein (myosin) with its track (an actin filament) is presented.

TL;DR: A new method of iris localization based on intensity value analysis is proposed in this paper and experimental results show that proposed method is very efficient and accurate.

TL;DR: In this article, an analysis of the time history of speckle patterns (THSPs) is presented, which is one of the most used procedures to evaluate the biological activity by biospeckle images.

TL;DR: In this article, the state of the art on full-field kinematic measurements at the micron scale is presented, and the shape of the gratings has been characterized using an atomic force microscope and compared with the theoretical profiles.

TL;DR: In this paper, a multi-spectral imaging system for paintings in the 380-800nm spectral region is presented, specifically developed to overcome most of the problems related to traditional detection systems based on CCD or Vidicon camera.

TL;DR: In this paper, the characteristics and abilities of excimer lasers for micromachining of a wide range of glass materials are reviewed and studied, and the procedures to machine single, arrayed, curved microstructures are described.

TL;DR: In this article, a new colour difference formula is proposed with an additional term, which ensures continuity of fringe order data over the domain, and the new method is termed as refined TFP.

TL;DR: A new technique of fiber-break detecting and monitoring in optical communication network systems is proposed and experimentally demonstrated that gives a minimal insertion loss and measurement accuracy to the distance break in place of the optical time domain reflectometer.

TL;DR: In this article, the general characteristics of phase shifting photoelasticity in the colour domain were investigated, focusing on the influence of spectral content of the light source, the spectral response of the colour camera filters, the dispersion of the birefringence and the error of quarter wave plates.

TL;DR: In this paper, an innovative real-time laser welding monitoring technique employing the correlation analysis of the plasma plume optical spectra generated during the process is presented, in order to look for a relationship between optical signals and welds quality, the influence of the experimental conditions on the correlation plots are also investigated.

TL;DR: In this article, an efficient iterative least-squares algorithm for phase-shifting interferometry is presented, where the phase shifts contain errors, and the residuals (i.e., the differences between the recorded intensities and their recalculated values) of least squares algorithm are dependent on these errors.