Christophe Stolz

• PhD
• Professor (Associate) at Université Bourgogne Europe

Recent RGB-D semantic segmentation has motivated research interest thanks to the accessibility of complementary modalities from the input side. Existing works often adopt a two-stream architecture that processes photometric and geometric information in parallel, with few methods explicitly leveraging the contribution of depth cues to adjust the sam...

Recent RGBD-based models for saliency detection have attracted research attention. The depth clues such as boundary clues, surface normal, shape attribute, etc., contribute to the identification of salient objects with complicated scenarios. However, most RGBD networks require multi-modalities from the input side and feed them separately through a...

The most prominent type of artifact contaminating electroencephalogram (EEG) signals are the eye blink (EB) artifacts, which could potentially lead to misinterpretation of the EEG signal. Online identification and elimination of eye blink artifacts are crucial in applications such a Brain-Computer Interfaces (BCI), neurofeedback, and epilepsy diagn...

Conventional 2D Convolutional Neural Networks (CNN) extract features from an input image by applying linear filters. These filters compute the spatial coherence by weighting the photometric information on a fixed neighborhood without taking into account the geometric information. We tackle the problem of improving the classical RGB CNN methods by u...

Conventional 2D Convolutional Neural Networks (CNN) extract features from an input image by applying linear filters. These filters compute the spatial coherence by weighting the photometric information on a fixed neighborhood without taking into account the geometric information. We tackle the problem of improving the classical RGB CNN methods by u...

Online detection and removal of eye blink (EB) artifacts from electroencephalogram (EEG) would be very useful in medical diagnosis and brain computer interface (BCI). In this work, approaches that combine unsupervised eyeblink artifact detection with empirical mode decomposition (EMD), and canonical correlation analysis (CCA), are proposed to autom...

This paper describes the use of polarization information to estimate the shape of emissive objects in the field of nonconventional imaging techniques for 3D digitization. Using “Shape from Polarization” method which is applied in the far infrared for transparent object and in the near infrared for the molten metal. Our study shows that by studying...

The EU imposes standards for the use of wood in structural applications. Local singularities such as knots affect the wood mechanical properties. They can be revealed by looking at the wood fiber orientation. For this reason, many methods were proposed to estimate the orientation of wood fiber using optical means, X-rays, or scattering measurement...

In recent years, NonDestructive Testing (NDT) systems have been upgraded with three-dimensional information. Indeed, combine the three-dimensional and thermal information allows a more meaningful analysis. In the literature, the data for NDT and three-dimensional (3D) reconstruction analysis are commonly acquired from independent systems. However,...

In the domain of 3D measurement for inspection purposes, standard systems based on triangulation approaches, can be limited by the nature of the observed surface. When the surface is not lambertian, i.e. highly reflective or transparent, other strategies to ease the measurement need to be developed. The idea of using the polarization property of th...

This paper presents a passive polarimetry method using a division of aperture optical device in order to measure the temperature distribution at the weld pool surface. Thermal emission from a hot liquid metal was investigated at a near-infrared wavelength corresponding to a blind spectral window of a helium plasma generated during gas tungsten arc...

This paper presents an application of “shape from polarization” method in the far Infrared range with applications for three-dimensional reconstruction of transparent objects. Shape from polarization is a recent application of more general polarization imaging technique having the aim to digitize the shape of the observed object. The principle i...

Nowadays, industries ensure the quality of their manufactured products through computer vision techniques and non-conventional imaging. 3D scanners and Non-Destructive Testing (NDT) systems are commonly used independently for such applications. Furthermore, these approaches combined together constitute a hybrid systems providing a 3D reconstruction...

The search for an efficient on-line monitoring system focused on the real-time analysis of arc welding quality is an active area of research. The topography and the superficial temperature field of the weld pool can provide important information which can be used to regulate the welding parameters for depositing consistent welds. One difficulty rel...

A nondestructive inspection method using an infrared detection system is presented in this paper; the system uses a YAG laser as excitation point. The material thermal response to this excitation is processed for the detection of volume defects, this technique integrated into a 3D scanning system allows us to get a 3D scan of the object as well as...

We present a method to recover the 3D shape of both front and back surfaces of smooth transparent objects, such as glass windows or containers. We use a combination of two methods known for the 3D reconstruction of specular surfaces: shape from distortion and shape from polarization. As each transparent surface reflects and transmits incident light...

This paper presents a passive polarimetry method using a wavefront division optical device in order to measure the temperature distribution at the weld pool surface. We studied thermal emission from a hot liquid metal at a near-infrared wavelength corresponding to a blind spectral window of the helium plasma generated during Gas Tungsten Arc Weldin...

A vision-based method is proposed to measure the 3D shape of external and internal surfaces (not accessible) of smooth transparent objects. Looking at the reflections of point sources on a specular surface with a polarimetric camera, we combine the measurements of two techniques: shape from distortion and shape from polarization. It permits us to r...

The polarimetric state of the thermal radiations emitted by the weld metal contains geometric information about the emitting surface. Even though the analysed thermal radiation has a wavelength corresponding to a blind spectral window of the arc plasma, the physical presence of the arc plasma itself interferes with the rays radiated by the weld poo...

The aim of the work presented in this paper is to develop a method for the automatic identification of tree species using Terrestrial Light Detection and Ranging (T-LiDAR) data. The approach that we propose analyses depth images built from 3D point clouds corresponding to a 30 cm segment of the tree trunk in order to extract characteristic shape fe...

En raison de l'utilisation croissante des scanners LiDAR terrestre (T-LiDAR) dans le domaine forestier, le développement d'outils logiciels pour la mesure automatique d'attributs d'inventaire forestier est devenu un domaine de recherche important. De nombreux travaux portant sur la localisation des arbres dans un nuage de points, la mesure du diamè...

In this Letter, a vision-based remote sensing methodology is proposed to measure the topography of weld pool surfaces from one single view. Thermal radiations emitted by the hot liquid metal at a wavelength within the arc plasma blind spectral window are acquired by a wavefront division polarimetric system. The refractive index of the liquid metal...

3D scanning has been investigated for several years and most of the proposed approaches assume a diffuse or near diffuse reflectance of the object’s surface, also called cooperative surfaces. For the case of “non cooperative surfaces”, such as transparent objects or mirror-like surfaces, usually, a thin layer of powder is sprayed onto the object su...

This paper presents a comparison between recent advances made in the field of non-conventional imaging techniques for 3D digitization of transparent object. After a survey, this paper focuses on two recent techniques later called: shape from Visible Fluorescence UV-induced and shape from polarization in the IR which recently emerged. Results obtain...

Due to the increasing use of Terrestrial Laser Scanning (TLS) systems in the forestry domain for forest inventory, the development of software tools for the automatic measurement of forest inventory attributes from TLS data has become a major research field. Numerous research work on the measurement of attributes such as the localization of the tre...

We report a multispectral based method that permits the evolution of shape from polarization setup applied to 3D shape estimation of transparent objects. The setup is based on a polarization imaging technique which is a recent imaging method based on the analysis of the polarization state of the light in the observed scene. The technique has rapidl...

Fashion and design greatly influence the conception of manufactured products which now exhibit complex forms and shapes. Two-dimensional quality control procedures (e.g., shape, textures, colors, and 2D geometry) are progressively being replaced by 3D inspection methods (e.g., 3D geometry, colors, and texture on the 3D shape) therefore requiring a...

A novel reconstruction scheme using ultraviolet (UV) structured point for transparent objects three-dimensional (3D) measurement was reported in our previous works. We address two main approaches behind a low-cost system within two suggested configurations (according to the structured light generation source: UV spot and UV line) in order to improv...

Automatic industrial surface inspection methodology based on Magnetic Particle Inspection is developed from image acquisition to defect classification. First the acquisition system is optimized, then tubular material images are acquired, reconstructed then stored. The characteristics of the crack-like defects with respect to its geometric model and...

Forest inventory automation has become a major issue in forestry. The complexity of the segmentation of 3D point cloud is due to mutual occlusion between trees, other vegetation, or branches. That is why, the applications done until now are limited to the estimation of the DBH (Diameter at Breast Height), the tree height and density estimation. Fur...

During the past decade, computer vision methods for inline inspection became an important tool in a lot of industrial processes. During the same time polarization imaging techniques rapidly evolved with the development of electro-optic components, as e.g. the polarization cameras, now available on the market. This paper is dedicated to the applicat...

3D surface acquisition is a subject which has been studied to a large extent. A significant number of techniques for acquiring shape have been proposed, and a wide range of commercial solutions are available. Nevertheless, today's systems still have difficulties when digitizing objects with non-Lambertian surfaces in the visible light spectrum, as...

In this paper, we present a novel approach exploiting fluorescence imaging to estimate the shape of transparent objects. Classical inspection systems require users to coat transparent objects with some powder before measurement. Methods suggested in literature through non contact measurement do not effectively deal with the refraction problem, thus...

This paper introduces a novel D measurement scheme based on UV laser triangulation to ascertain the shape of transparent objects. Transparent objects are extremely difficult to scan with traditional 3D scanners because of the refraction problem observed in the visible range. Therefore, the object surface needs to be preliminary powdered before bein...

This paper presents a multispectral imaging system for 3D reconstruction of transparent objects based on “shape from polarization” technique. The originality of this work relies on a multispectral active lighting system which enables to cope with the two ambiguities on the zenith angle and azimuth angle. A calibration step allows optimising the pol...

Classical 3D inspection systems require users to coat transparent objects before measurement. Experimental techniques via non contact measurement, suggested in literature, do not treat inter reflections. The aim of our work is to develop a non contact D measurement system for transparent objects by using a polarimetric imaging method in far infrare...

This paper focuses a method to acquire thesurface of transparent objects for 3D measurement.The technique relies on the so called “Shape fromPolarization” technique. The principle of thispolarization imaging technique is as follows: afterbeing reflected, an unpolarized light becomespartially linearly polarized. The surface normals canbe evaluated b...

This paper deals with a D measurement system based on the "Shape from Polarization" method applied for transparent objects. The method is an application of polarization imaging techniques and its principle is as follows: after being reflected, an unpolarized light becomes partially linearly polarized. By analyzing its polarization parameters and by...

This paper aims at reviewing the recent published works dealing with industrial applications which rely on polarization imaging. A general introduction presents the basics of polarimetry and then 2D and 3D machine vision application are presented as well as the latest evolution in term of high speed polarimetric imaging.

In order to achieve better quality on their products, manufacturers now use more and more artificial vision systems during their process. Concerning transparent objects the task is not trivial and requires controlling the whole lighting of the scene. This paper deals with a polarization imaging method and its application to shape measurement of tra...

We present a new way of solving the ambiguity that appears in the shape from polarization method. This ambiguity, concerning the normals orientation of the surface, was previously solved thanks to a propagation algorithm. In this paper, the ambiguity is solved thanks to a special active lighting. This method is less time computing and is more robus...

In the field of industrial vision, the three-dimensional inspection of highly reflective metallic objects is still a delicate task. We deal with a new automated three-dimensional inspection system based on polarization analysis. We first present an extension of the shape-from-polarization method for dielectric surfaces to metallic surfaces. Then, w...

In the field of industrial vision, the three-dimensional inspection of highly reflective metallic objects is still a delicate task. We deal with a new automated three-dimensional inspection system based on polarization analysis. We first present an extension of the shape-from-polarization method for dielectric surfaces to metallic surfaces. Then, w...

This paper deals with the analysis and conservation of ancient wooden stamps from museum or library collections. The aim is to provide historians with tools that ease the process of handling and observation of very fragile and unique objects. By performing a three-dimensional imaging of stamps, data are processed in three different ways: (1) adapti...

This paper presents a new application of "Shape from Polarization" method to specular metallic surfaces. It demonstrates how to extend the commonly used method for dielectric to metallic surfaces. Studying the state of polarization of the reflected light is very useful to get information on the normals of the surface. After computing the surface no...

In the field of industrial vision, extracting the 3D shape information of highly reflective metallic objects is still a delicate task. This paper presents a new application of "Shape from Polarization" method to specular metallic surfaces. Studying the state of polarization of the reflected light is very useful to get information on the normals of...

In the field of industrial vision, extracting the 3D shape information of highly reflective metallic objects is still a delicate task. This paper presents a new application of "Shape from Polarization" method to specular metallic surfaces. Studying the state of polarization of the reflected light is very useful to get information on the normals of...

We propose in this paper an application of multiresolution analysis techniques to extract information contained in the growth increments of a bivalve mollusk called: Calyptogena. The first stage consists in extracting a range image of the mollusk"s shell using a 3-D scanner. Applying a multiresolution analysis enables us to localize precisely those...

We propose the optical implementation of diffractive optical elements onto electrically addressed liquid-crystal spatial light modulators. We compare the classic implementations onto amplitude-only or phase-only domains with the implementations onto coupled phase and amplitude (spiral) domains. We demonstrate that the coupling between amplitude and...

Many implementations of computer generated holograms (CGH’s) or diffractive optical elements (DOE’s) onto spatial light modulators (SLM’s) have already been considered. In this paper, we first review the various types of SLM’s available for DOE’s and the implementations of DOE’s onto SLM’s already reported in the literature. Then we investigate the...

Different computer generated hologram (CGH) encoding techniques are compared. It is shown that the iterative methods such as iterative Fourier transform algorithm (IFTA) or direct binary search (DBS) can satisfy the requirements of information processing systems. Phase CGHs with four or more quantization levels show the highest diffraction efficien...

Résumé : Nous proposons ici l'application des techniques d'analyse multirésolution pour l'extraction des stries de croissance d'un mollusque bivalve vivant en grande profondeur près de sources hydrothermales: Calyptogena. La première étape consiste à extraire, à l'aide d'un scanner 3D, une image de profondeur de la coquille à étudier. Nous effectuo...