Search results for "reflectance"
showing 10 items of 161 documents
In-Situ DRIFT Spectroscopic Investigation on the Chemical Evolution of Zinc Phosphate Acid−Base Cement
2000
Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy has been used to follow the chemical evolution of zinc phosphate acid−base cement (ZPC), which has been prepared from unmodified, as well as from aluminum- and zinc-modified orthophosphoric acid. For the first time, amorphous dizinc cyclotetraphosphate octahydrate, Zn2P4O12·8H2O, although hydrolytically instable, has been observed as precursor phase prior to crystallization of α-hopeite, α-Zn3(PO4)2·4H2O, in both systems. Within minutes from onset of mixing the infrared spectrum of unmodified ZPC is dominated by the characteristic vibrations of α-hopeite, due to matrix crystallization. Setting of modified ZPC is strongly af…
3D shape extraction of internal and external surfaces of glass objects
2013
Three-dimensional (3D) digitization of manufactured objects has been investigated for several years and consequently, many techniques have been proposed. Even if some techniques have been successfully commercialized, most of them assume a diffuse or near diffuse reflectance of the object’s surface, and difficulties remain for the acquisition of “optically non cooperative” surfaces, such as transparent or specular ones. To address such surfaces, we propose a non conventional technique, called “Scanning from Heating” (SfH). In contrast to classical active triangulation techniques that acquire the reflection of visible light, we measure the thermal emission of the heated surface. The aim of th…
Surface Reflectance: An Optical Method for Multiscale Curvature Characterization of Wear on Ceramic–Metal Composites
2020
Surface gradient characterization by light reflectance (SGCLR) is used for the first time for multiscale curvature calculations and discrimination of worn surfaces on six damaged ceramic&ndash
Classification par méthodes d’apprentissage supervisé et faiblement superviséd’images multimodales pour l’aide au diagnostic du lentigo malin en derm…
2021
Carried out in collaboration with the Saint-Étienne University Hospital, this work provides additional information to help the skin diagnosis by providing new decision methods on Lentigo Maligna and Lentigo Maligna Melanoma pathologies. To this end, the modalities regularly used in clinical conditions are made available to this work and are orchestrated within a multimodal process. Among image modalities, may be mentioned the clinical photography, the dermatoscopy, and the confocal reflectance microscopy. Initially, the first steps of this manuscript focus on reflectance confocal microscopy as the work in computer diagnostic assistance is relatively underdeveloped, in particular on the dete…
Sun-induced chlorophyll fluorescence II: Review of passive measurement setups, protocols, and their application at the leaf to canopy level
2019
Imaging and non-imaging spectroscopy employed in the field and from aircraft is frequently used to assess biochemical, structural, and functional plant traits, as well as their dynamics in an environmental matrix. With the increasing availability of high-resolution spectroradiometers, it has become feasible to measure fine spectral features, such as those needed to estimate sun-induced chlorophyll fluorescence (F), which is a signal related to the photosynthetic process of plants. The measurement of F requires highly accurate and precise radiance measurements in combination with very sophisticated measurement protocols. Additionally, because F has a highly dynamic nature (compared with othe…
Digitization and characterization of local reflectance of complex surfaces for visual inspection
2022
Mastering the visual perception of the surfaces of manufactured products is a central issue for industry. However, in industry, the quality of surfaces is often assessed by human inspectors. Only a few specific cases use an instrumental or photometric approach. Among the photometric approaches, one of them is experiencing significant growth: Reflectance Transformation Imaging (RTI). The RTI makes it possible to obtain a reduced and simplified estimate of the Bidirectional Reflectance Distribution Function (BRDF) and an estimate of the geometry of the surface. However, this technique has limitations in terms of data acquisition and processing. The objective is therefore to correct some of th…
On-line database of voltammetric data of immobilized particles for identifying pigments and minerals in archaeometry, conservation and restoration (E…
2016
[EN] A web-based database of voltammograms is presented for characterizing artists' pigments and corrosion products of ceramic, stone and metal objects by means of the voltammetry of immobilized particles methodology. Description of the website and the database is provided. Voltammograms are, in most cases, accompanied by scanning electron microphotographs, X-ray spectra, infrared spectra acquired in attenuated total reflectance Fourier transform infrared spectroscopy mode (ATR-FTIR) and diffuse reflectance spectra in the UV-Vis-region. For illustrating the usefulness of the database two case studies involving identification of pigments and a case study describing deterioration of an archae…
An optical classification tool for global lake waters
2017
Shallow and deep lakes receive and recycle organic and inorganic substances from within the confines of these lakes, their watershed and beyond. Hence, a large range in absorption and scattering and extreme differences in optical variability can be found between and within global lakes. This poses a challenge for atmospheric correction and bio-optical algorithms applied to optical remote sensing for water quality monitoring applications. To optimize these applications for the wide variety of lake optical conditions, we adapted a spectral classification scheme based on the concept of optical water types. The optical water types were defined through a cluster analysis of in situ hyperspectral…
Multispectral Imaging using a Stereo Camera: Concept, Design and Assessment
2011
This paper proposes a one-shot six-channel multispectral color image acquisition system using a stereo camera and a pair of optical filters. The two filters from the best pair selected from among readily available filters such that they modify the sensitivities of the two cameras in such a way that they produce optimal estimation of spectral reflectance and/or color are placed in front of the two lenses of the stereo camera. The two images acquired from the stereo camera are then registered for pixel-to-pixel correspondence. The spectral reflectance and/or color at each pixel on the scene are estimated from the corresponding camera outputs in the two images. Both simulations and experiments…
Validation of a 2D multispectral camera: application to dermatology/cosmetology on a population covering five skin phototypes
2011
International audience; This paper presents the validation of a new multispectral camera specifically developed for dermatological application based on healthy participants from five different Skin PhotoTypes (SPT). The multispectral system provides images of the skin reflectance at different spectral bands, coupled with a neural network-based algorithm that reconstructs a hyperspectral cube of cutaneous data from a multispectral image. The flexibility of neural network based algorithm allows reconstruction at different wave ranges. The hyperspectral cube provides both high spectral and spatial information. The study population involves 150 healthy participants. The participants are classif…