The sliding contact between the finger and the surface of an object generates vibrations that propagate into the skin and activate the mechanoreceptors. The characteristics of the vibrating signals ...give information about the texture features, affecting the tactile perception. Previous studies have focused on the relation between the physical characteristics of the surfaces and the detected signals. This study investigates the direct correlation between contact-induced vibrations and tactile perception of textures. Two sets of samples were investigated: periodic samples and isotropic samples. Within the same set, each sample exhibits a clearly distinct surface roughness relative to one another. Sensory tests were conducted with blind people to evaluate the tactile discrimination of the samples as a function of roughness. The analysis of the Root Mean Square of the acceleration and the acceleration spectra obtained for the different samples, allowed explaining the mismatch between the actual roughness of the samples and the roughness perceived by the subjects, which is directly related to the induced vibrations.
•Tribological and sensory tests developed on periodic and isotropic surfaces.•Sensory tests on blind people to evaluate the tactile discrimination of textures.•The perceived roughness differs from the effective surface roughness of textures.•Friction-induced vibrations influence the individual perception of roughness.•Friction-induced vibrations allows objective indexes for perception of textures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The paper presents a method to estimate the Statistically Equivalent Periodic Unit Cell (SEPUC) corresponding to a masonry with quasi-periodic texture. The identification of the texture and the ...constituent phases (unit blocks and mortar joints) is achieved by means of digital image processing techniques applied to color image of the masonry wall. A statistical analysis of geometrical parameters (width and height of blocks, thickness and length of mortar joints) allows to estimate their probability distribution and to identify the typology of the texture. Subsequently a Monte Carlo analysis is performed using several tentative SEPUCs generated with different dimensions of blocks and joints according to the estimated distributions. A criterion was eventually proposed to identify, among the numerically generated ones, the SEPUC which is more suitable to model the behavior of masonry wall. The SEPUC is analyzed with techniques available for periodic texture, applying periodic boundary conditions, in order to estimate the equivalent elastic stiffness. The proposed method is validated comparing the results in the elastic range obtained with SEPUC and those obtained imposing essential and natural boundary conditions on the original texture.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ
•Optical properties of an inverted pyramidal texture on a Si solar cell are simulated as a function of periodicity.•A optimal front grating period of 1000nm is identified that works for a wide range ...of solar cell thicknesses.•Results of the simulation are compared with experiment.
A periodically structured surface or grating has been used to demonstrate state-of-the-art high efficiency crystalline silicon photovoltaic cells. However, until now the understanding of the complete relationship between the grating periodicity, silicon thickness, and absorption enhancement in silicon solar cell with an inverted pyramidal texture is still unclear. In this paper, we simulate front surface inverted pyramidal grating texture on 2–400-μm thick silicon and optimize it to derive maximum photocurrent density from the cell. We identify a “one-size-fits-all” front grating period of 1000nm that leads to maximum photo-absorption of normally incident AM1.5g solar spectrum in silicon (configured with a back surface reflector) irrespective of the thickness of the crystalline silicon absorbing layer. With the identification of such universally optimized periodicity for the case of an inverted pyramidal grating texture, a common fabrication process can be designed to manufacture high-efficiency devices on crystalline silicon regardless of the wafer thickness. The measured reflectance from submicron and wavelength scale periodic textures also verifies simulation results.
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Direct Laser Interference Patterning (DLIP) using ultrashort pulsed laser sources is a single-step process to produce micro- and nanostructured surfaces by ablation. Spatial periods of a few ...micrometers are patterned using a laser scanner system with two interfering beams. In this study, the field of DLIP processing is expanded by handling spatial periods in the range of 1 mum and below. Precise periodic ablation is achieved with an optical setup tailored for a homogenous topography of spatial periods in the micro and sub-micrometer range. The lateral intensity distribution of the interference area used for ablation is shaped using beam shapers in order to achieve a homogenous intensity distribution and hence increase the homogeneity of the periodic texture in the ablated area. The shape of the interference area is formed into a square profile for the purpose of seamless stitching plenty of to be processed areas. This creates large area periodic textures with high homogeneity. Two beams with ultrashort laser pulses of 10 ps duration and a wavelength of 532 nm are used to structure line-like periodic surface textures with spatial periods of 650 nm. The beam shaping elements modify the lateral intensity distribution in the interference area and the affiliated profile. This enables precise patterning of tool steels with spatial periods in sub-micrometer range for applications in the field of life science surfaces. Keywords: Direct Laser Interference Pattering DLIP, beam shaping, homogenous topography, large area periodic textures, increase of throughput
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The importance of an automated defect inspection system has been increasing in the manufacturing industries. Various products to be examined have periodic textures. Among image-based inspection ...systems, it is common that supervised defect segmentation requires a great number of defect images with their own region-level labels; however, it is difficult to prepare sufficient training data. Because most products are of normal quality, it is difficult to obtain images of product defects. Pixel-wise annotation for semantic segmentation tasks is an exhausting and time-consuming process. To solve these problems, we propose a weakly-supervised defect segmentation framework for defect images with periodic textures and a data augmentation process using generative adversarial networks. With only image-level labeling, the proposed segmentation framework translates a defect image into its defect-free version, called a golden template, using CycleGAN and then segments the defects by comparing the two images. The proposed augmentation process creates whole new synthetic defect images from real defect images to obtain sufficient data. Furthermore, synthetic non-defect images are generated even from real defect images through the augmentation process. The experimental results demonstrate that the proposed framework with data augmentation outperforms an existing weakly-supervised method and shows remarkable results comparable to those of supervised segmentation methods.
En fait, le concept de texture n’est pas facile à définir, mais il est clair qu’il est fortement lié au Système Visuel Humain. Sachant que le Modèle LIP est compatible avec la vision humaine, il nous ...a semblé intéressant de créer des outils logarithmiques dédiés à l’évaluation de la texture. Nous nous sommes concentrés sur la notion de covariogramme, qui peut être pilotée par diverses métriques logarithmiques. Ces métriques jouent le rôle d’outils de “corrélation”, avec l’avantage de prendre en compte la vision humaine. De plus, les outils LIP sont peu dépendants des conditions d’éclairement et fournissent donc des résultats robustes si celles-ci varient. Les deux derniers Chapitres proposent une nouvelle approche consistant à considérer les niveaux de gris d’une image comme les phases d’un milieu. Chaque phase permet de simuler la percolation d’un liquide dans le milieu, définissant ainsi des trajectoires de percolation. Chaque propagation d’un pixel à un autre est considérée comme facile ou non, en fonction des niveaux de gris traversés. Une « fonction de coût » est créée, qui modifie le « temps » de propagation d’un point à l’autre. De plus, la fonction de coût peut être calculée dans le contexte LIP, pour prendre en compte la vision humaine
This thesis looks at the evaluation of textures in two different perspectives using logarithmic image processing (LIP) framework. The first case after introducing the concept of textures and giving some classical approaches of textures evaluation, it gives an original approach of textures evaluation called covariogram which is derived from similarity metrics like distances or correlations etc. The classical covariogram which is derived from the classical similarity metrics and LIP covariogram are then applied over several images and the efficiency of the LIP one is clearly shown for darkened images. The last two chapters offer a new approach by considering the gray levels of an image as the phases of a medium. Each phase simulates like a percolation of a liquid in a medium defining the percolation trajectories. The propagation from one pixel to another is taken as easy or difficult determined by the difference of the gray level intensities. Finally different parameters like fractality from fractal dimensions, mean histogram etc associated to these trajectories are derived, based on which the primary experiment for the classification of random texture is carried out determining the relevance of this idea. Obviously, our study is only first approach and requires additional workout to obtain a reliable method of classification
In this letter, AlGaInP-GaP-based light-emitting diodes (LEDs) were fabricated with an Si substrate and an SiO 2 -ITO-Ag omni-directional reflector using a metal-to-metal bonding technique. To ...enhance light extraction efficiency, a periodic texture was applied to the (Al 0.5 Ga 0.5 ) 0.5 In 0.5 P surface layer of AlGaInP-Si LEDs by photolithography and a wet etching process. The exterior of the etched texture consists of a series of bowl-shaped recesses. With a 350-mA current injection, the typical output power of the AlGaInP-Si LEDs with and without the textured surface (LED-I and LED-II, respectively) were measured at approximately 118 and 81 mW, respectively, when the LED chips were bonded on the TO 46 without resin encapsulation. The enhancement of output power in LED-I can be attributed to a multitude of bowl-shaped notches on the surface, which resulted in a reduction of the reabsorption probability of the photons due to the fact that the photon path length in LED-I is shorter than in LED-II before the photons escape into the free space.
Extraction of a representative tile from a near-periodic texture Djado, Khalid; Egli, Richard; Deschênes, François
Computer graphics and interactive techniques in Australasia and South East Asia: Proceedings of the 3rd international conference on Computer graphics and interactive techniques in Australasia and South East Asia; 29 Nov.-02 Dec. 2005,
11/2005
Conference Proceeding
Near-periodic textures are all around us, in brick walls, fabrics, mosaics, and many other manifestations. They are made up of a basic motif, which can be extracted, yielding a small image known as a ...tile. In particular, such textures are used in 3D scenes in virtual environments like games. However, the memory allocated for textures on a video card is limited. Generating texture by tiling allows scenes to be rendered in a realistic manner while using very little memory. This paper presents a simple method for extracting a representative tile from a near-periodic texture, working from a photo. The period of the texture is calculated to determine the size of the tile. Then the representative tile is chosen based on two criteria: avoiding color discontinuities at the junction of tiles, and recreating a texture that is as faithful as possible to the original.
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