Showing papers in "Optics and Lasers in Engineering in 2012"

TL;DR: The single-shot 3D shape measurement techniques by projecting and capturing one fringe pattern image on the object surface, the wrapped phase demodulation algorithms from one captured image are reviewed.

TL;DR: In this article, the influence of laser power, scanning speed and powder feed rate on the shape factor and the cladding-bead geometry (layer width, layer height and molten depth) with regard to injecting Ti6Al4V powder on TC4 substrate was investigated.

TL;DR: Three quantitative schlieren techniques applied to the measurement and visualization of a two-dimensional laminar free-convection boundary layer are compared, with good results and requires less expensive apparatus than the other methods, but lacks the simplification of parallel light that they feature.

TL;DR: The results show that iterative learning control including 3D scanning is a suitable method for automatic deposition of fully dense metal structures in the manufacture of jet engine components.

TL;DR: In this paper, the authors present analytical relationships between the laser tracks geometrical characteristics (width, height, area, penetration depth) and the processing parameters (laser power P, scanning speed V and powder mass flow Qm).

TL;DR: A new complementary Gray-code method is proposed in this paper as well as the corresponding phase-unwrapping method, which can reliably reconstruct the nature phase distribution of the tested object with only one extra fringe pattern.

TL;DR: The effectiveness of the proposed incremental reliability-guided digital image correlation (RG-DIC) technique is demonstrated by retrieving the full-field deformation of a foam sample subjected to large compressive deformation.

TL;DR: Wang et al. as mentioned in this paper presented a novel 3D scanning technique for high-reflective surfaces based on phase-shifting fringe projection method, which is developed to process the fringe images reflected from the shiny surfaces, and generates a synthetic fringe image by fusing the raw fringe patterns, acquired with different camera exposure time and the illumination fringe intensity from the projector.

TL;DR: Keywords: fringe analysis Reference EPFL-ARTICLE-176959doi:10.1016/j.optlaseng.2012.04.006View record in Web of Science URL: http://www.sciencedirect.com/science/article/pii/S0143816612001182

TL;DR: In this paper, a hybrid approach, obtained by combining robust parameter design methodology and fuzzy logic theory has been applied to compute the fuzzy multi-response performance index, which is further used for multi-objective optimization.

TL;DR: Results on some grayscale and color images show that the proposed image encryption method satisfies the properties of confusion and diffusion, execution speed and has perfect information concealing.

TL;DR: The system parameters of Arnold transform and gyrator transform in each channel serve as additional keys in color image encryption and decryption, and hence enhances the security of the system.

TL;DR: Based on Arnold transform and discrete fractional angular transform, a double image encryption algorithm is designed and the parameters of the two transforms serve as the additional keys for enhancing the security.

TL;DR: An improved coarse search method is developed to calculate the initial correlation parameters for the seed point, which guarantees that the correlation calculation can be carried out successfully even in large deformation situation.

TL;DR: In this article, the transition from conduction to keyhole welding was investigated by increasing power density and using different beam diameters and interaction times, and it was shown that the transition has a range of power densities that depend on the beam diameter and on the interaction time.

TL;DR: In this paper, the results of laser peening without coating on low carbon austenitic stainless steel 316L were discussed, and the dependence of laser pulse density on properties such as surface roughness, surface residual stress, microhardness, and corrosion behavior of LPwC specimen were investigated.

TL;DR: In this article, the authors evaluated the effects of laser glazing on the microstructure and thermal shock resistance of the topcoats of Inconel 738 LC superalloy coupons and found that the life times of the CYSZ thermal barrier coatings were enhanced by the formation of a continuous network of segmented cracks perpendicular to the surface and the increase in strain accommodation.

TL;DR: In this article, a removal technique based on the ablation of superimposed layers of composite material is proposed and analyzed in detail as a function of energy density delivered to the surface, hatch strategy and thickness of the laminate to be drilled.

TL;DR: In this paper, the full-field displacements around the crack-tip region of the test sample were calculated using DIC and the SIF associated with unavoidable rigid-body displacement motion was calculated simultaneously from the experimental data.

TL;DR: A new method for estimating the 3D gaze position based on the illuminative reflections (Purkinje images) on the surface of the cornea and lens by considering the3D optical structure of the human eye model is proposed.

TL;DR: In this article, a simple model for channel width and depth as a function of processing parameters and threshold fluence is presented, and it is shown that the channel depth is a linear function of the number of laser pulses per channel width.

TL;DR: In this article, the authors discuss the pros and cons of the three phase demodulation techniques on phase calculation at discontinuities and/or slopes, and compare the performance of Fourier transform, Windowed Fourier Transform (WFT), and Wavelet Transform (WT).

TL;DR: In this paper, laser welding of dissimilar combination of Titanium and stainless steel (304) has been carried out by varying the laser power, welding speed and position of the laser beam with respect to the joint centre.

TL;DR: In this article, a laser shot peening on precipitation hardened aluminum alloy 6061-T6 with low energy (300mJ, 1064nm) Nd:YAG laser using different pulse densities of 22 and 32 pulses/mm2 and 32pulses /mm2, respectively.

TL;DR: The phase or instantaneous frequency of fringe patterns with spatial or temporal carriers can be recovered from the wavelet ridge, a path that follows the maximum modulus of the CWT.

TL;DR: A method to recover absolute phase by using only four images: three phase-shifted patterns and one stair pattern, which has the merit of measurement speed and is suitable for measuring step-height objects.

TL;DR: The effects of CPU and GPU parallel computing specifically in EM & OM applications in a broad scope, which include digital image/volume correlation, fringe pattern analysis, tomography, hyperspectral imaging, computer-generated holograms, and integral imaging are reviewed.

TL;DR: In this paper, an experimental laser shock peening study on SAE 9260 spring steel, performed with an in-house developed 2.5-J/7-ns pulsed Nd:YAG laser, aimed to evaluate laser shock Peening process as a possible alternative to existing shot peening practice for enhancing fatigue life of leaf springs.

TL;DR: A new approach for image encryption based on the real-valuedness of the reality-preserving multiple-parameter fractional Fourier transform and the decorrelation property of chaotic maps is proposed in order to meet the requirements of the secure image transmission.

TL;DR: In this article, different velocities and different laser shift-distances between two successive layers are used to build walls, and a relationship between the process parameters and the wall height is obtained with a good correlation.