Bart Ribbens

University of Antwerp | UA · Faculty of Applied Engineering

This paper provides a comprehensive investigation into characterizing viscoelastic properties in soft materials, focusing on silicone. Conventional measurement techniques such as tensile testing and dynamic mechanical analysis prove inadequate for soft materials. The proposed method utilizes Rayleigh surface wave propagation, employing a laser Dopp...

Cycling witnesses an increasing number of women breaking barriers and inspiring change. Despite these advancements, there remains significant work to achieve full equality and recognition for women cyclists. Key gender gaps persist in: ̵ Ergonomics and performance optimization: The cycling industry largely focuses on tacit and explicit knowledge on...

In non-destructive inspections today, the size of the sample being examined is often limited to fit within the field of view of the camera being used. When examining larger specimens, multiple image sequences need to be stitched together into one image. Due to uneven illumination, the combined image may have artificial defects. This manuscript prov...

When studying paintings with active infrared thermography (IRT), minimizing the temperature fluctuations and thermal shock during a measurement becomes important. Under these conditions, it might be beneficial to use lock-in thermography instead of the conventionally used pulse thermography (PT). This study compared the observations made with lock-...

Spot welds have a significant part in the creation of automotive vehicles. Since the integrity of, for example, a car, is dependent on the performance of multiple welds, it is important to ensure the quality of each spot weld. Several attempts have been made in order to determine the quality of spot welds, but most of them do not focus on the appli...

Melanoma remains a deadly cancer despite significant advances in immune checkpoint blockade and targeted therapies. The incidence of melanoma is also growing worldwide, which highlights the need for novel treatment options and strategic combination of therapies. Here, we investigate non‐thermal plasma (NTP), an ionized gas, as a promising, therapeu...

To automatically evaluate the ergonomics of workers, 3D skeletons are needed. Most ergonomic assessment methods, like REBA, are based on the different 3D joint angles. Thanks to the huge amount of training data, 2D skeleton detectors have become very accurate. In this work, we test three methods to calculate 3D skeletons from 2D detections: using t...

The aim of this research topic and paper is to investigate the application possibilities of vision technology in the textile industry. These include RGB, active thermography and hyperspectral imaging techniques. In the future, this approach will be supplemented by a machine learning algorithm (e.g., in Matlab or Python) to enable the detection of d...

Nowadays, performing dynamic line scan thermography (DLST) is very challenging, and therefore an expert is needed in order to predict the optimal set-up parameters. The parameters are mostly dependent on the material properties of the object to be inspected, but there are also correlations between the parameters themselves. The interrelationship is...

Bayesian inference using Gaussian processes on large datasets have been studied extensively over the past few years. However, little attention has been given on how to apply these on a high resolution input space. By approximating the set of test points (where we want to make predictions, not the set of training points in the dataset) by a kd-tree,...

Quantitive infrared thermography like active thermography is a non-destructive testing technique that is used to inspect surfaces of components for defects. A problem with infrared-based defect detection is that misclassifications based on geometrically dependent measurement characteristics can occur. This problem becomes more problematic with the...

Using an optimised heating source in active thermography can facilitate the processing of measurement results. By designing a custom heat source for dynamic line scan thermography, we reduced the excitation power needed to heat the sample and decreased the unwanted side effects originating of a wide-range heating source. The design started from a r...

In order to identify the exact location of a useful perforator for DIEP flap breast reconstruction, CT images are made in the pre-operative phase. The aim of this research is to evaluate if dynamic infrared thermography is a helpful tool to check and visualize the blood flow in the flap during the pre- and peroperative phase. The results will be us...

Dynamic infrared thermography (DIRT) has been used to locate perforating vessels and to assist in reconstructive breast surgery. Qualitative information on the perforating vessels is obtained by analysing the rate and pattern of rewarming of hot spots which are easily registered with an infrared camera. Thermal measurements are made before and duri...

Breast reconstruction with an autologous free Deep Inferior Epigastric Perforator (DIEP) flap is one of the preferred options following mastectomy. A challenging step in this procedure is the selection of a suitable perforator that provides sufficient blood supply for the flap. The current golden standard for perforator mapping is computed tomograp...

In this article we provide a very robust algorithm to compute the position of the center of a sphere with known radius from one image by a calibrated camera. To our knowledge it is the first time that an exact sphere localization formula is published that only uses the (pixel) area and the ellipse center of the sphere image. Other authors either de...

The fatigue performance and healing ability of asphalt pavements are important for mixture design, rehabilitation, and maintenance of the roads. By analyzing these parameters in an asphalt mixture, it is possible to predict the crack formation and propagation in asphalt pavements and healing of these cracks during the rest periods. The healing effe...

For some applications it can be preferable to use images of spheres in order to calibrate a 2D camera. All published sphere-based algorithms need the complete knowledge of the elliptic sphere image, i.e. 5 geometric parameters, in particular the ellipse orientation. Because sphere images tend to be close to circular shapes, this orientation is ofte...

Quality control of complex components using thermographic cameras remains a challenging task in industry because it is difficult to quantify the defect size and locations. This research describes a new automated methodology with minimal user input which uses a 3D pose estimation technique to map infrared thermographic images directly on a CAD file...

In order to determine camera parameters, a calibration procedure involving the camera recordings of a checkerboard is usually performed. In this paper, we propose an alternative approach that uses Gray-code patterns displayed on an LCD screen. Gray-code patterns allow us to decode 3D location information of points of the LCD screen at every pixel i...

In-line inspection of advanced components remains a challenging task in industry. The authors will describe an automated methodology that uses numerical simulations to automatically determine the best set of experimental parameters to inspect the structure on defects using active thermography. The inspection is performed using a robotic arm and adv...

Carbon fiber bicycle frames are complex-shaped structures and are prone to delaminations and difficult to inspect. The use of finite element model updating is common in structural dynamics but not so common in active thermography inspection. However, there are many advantages to using thermography when inspecting bicycle frames. These include the f...

In-line inspection of advanced components, for example a composite bicycle frame, remains a challenging task in industry. We describe a methodology which uses numerical simulations to automatically determine the best set of experimental parameters to inspect the structure on defects using active thermography. The inspection is performed using a rob...

Finite element analysis of complex geometries such as honeycomb composites, brings forth several difficulties. These problems are expressed primarily as high calculation times but also memory issues when solving these models. In order to bypass these issues, the main goal of this research paper is to define an appropriate equivalent model in order...

Range cameras suffer from both systematic and random errors. We present a procedure to evaluate both types of error separately in one test. To quantify the systematic errors, we use an industrial robot to provide a ground truth motion of the range sensor. We present an error metric that compares this ground truth motion with the calculated motion,...

In this paper, a new fully automated scanning laser Doppler vibrometer (LDV) measurement technique is presented. In contrast to existing scanning LDV techniques which use a 2D camera for the manual selection of sample points, we use a 3D Time-of-Flight camera in combination with a CAD file of the test object to automatically obtain measurements at...

Despite the fact that most thermography research is still based on 2D imaging techniques, researchers are investigating the true power and calibration of thermal imaging in three dimensions [1, 2]. In our research multi-camera systems are built up around time-of-flight sensors [3–5], used to capture the geometric shape of the test object. The measu...

There are many advantages of using thermography for updating numerical models. These include the fact that it can be performed in-situ, it can cover large areas and it is a quantitative method. In this paper, a numerical model of a bicycle frame will be updated and optimized by the surface temperature distribution captured with pulsed thermography....

Little research has examined that inaccurate estimations of directional emissivity form a major challenge during both passive and active thermographic measurements. Especially with the increasing use of complex curved shapes and the growing precision of thermal cameras, these errors limit the accuracy of the thermal measurements. In this work we de...

Scanning laser Doppler vibrometers (LDV) are used to measure full-field vibration shapes of products and structures. In most commercially available scanning laser Doppler vibrometer systems the user manually draws a grid of measurement locations on a 2D camera image of the product. The determination of the correct physical measurement locations can...

In non-destructive evaluation the use of finite element models to evaluate structural behavior and experimental setup optimization can complement with the inspector׳s experience. A new adaptive response surface methodology, especially adapted for thermal problems, is used to update the experimental setup parameters in a finite element model to the...

We reanimate the (sometimes forgotten) Belgian Theorems, and show how the balls of Dandelin can give us elegant proofs for geometric properties of perspective ball projections. As a consequence, we derive a new formula for computing the focal length by means of 1 image of 1 ball. By means of simulations we show the sensitivity of our formula in fun...

We propose to represent a time-of-flight (TOF) camera by the map of «internal radial distances» (IRD), associating an intrinsic distance to each pixel, as an alternative for the classic pinhole model. This representation is more general than the perspective model and appears to be a natural concept for 3D reconstruction and other applications of TO...

In non-destructive evaluation the use of finite element models to evaluate structural behavior and experimental setup optimization can complement experience of the inspector. A new adaptive response surface methodology, especially adapted for thermal problems, is used to update the experimental setup parameters in a finite element model to the stat...

In non-destructive evaluation the use of finite element models to evaluate structural behavior and experimental setup optimization can complement experience of the inspector. A new adaptive response surface methodology, especially adapted for thermal problems, is used to update the experimental setup parameters in a finite element model to the stat...

In non-destructive measurements, the estimation of quantitative results from thermographic data remains difficult and time-consuming. Present non-destructive evaluation techniques use relative measurements between a possible defective and a predefined healthy area. With the use of a finite element model, the assumption of a predefined sound area is...

In 2012 SABCA Limburg N.V., a Belgian aerospace company, started with the production of the Flap Support Fairings for the A350-800 commercial aircraft. These parts are manufactured using a combination of honeycomb and carbon fiber pre-preg laminates. After part curing all fairings are inspected for defects. The most straightforward and common inspe...

In the 20th century optical measurement techniques became a valid alternative for many conventional measurement techniques. They have the advantage over non-optical techniques that there is no contact with the test specimen required, but a large disadvantage is that the surface needs to be visible and within working distance of the measurement sens...

We present a simple and accurate procedure to calibrate the pinhole parameters of a Time-of-Flight camera: the principal point c = (u0, v0), the focal length f and, if needed, the aspect ratio τ . Only one image of a flat surface is needed. Using the radial distances as provided by the Time-of-Flight principle, we reconstruct the pixel rows (or pix...

A finite element (FE) model is updated and optimized by making use of the surface temperature distribution captured with pulsed thermography (PT) on a PVC plate. The temperature distribution across the surface can be measured. As the amount of experimental data to be used in this case is very high, an accurate, time-efficient adaptive response surf...

To determine the topography of an object, spatial- and temporal profilometry techniques have been developed with their corresponding strengths as and weaknesses. The main weakness of phase-unwrapping techniques is the possible error in the unwrapped phase due to large discontinuities in the model and sudden color changes. To eliminate the phase-unw...

This article presents a new feature for detecting planarity when using range images on the principle of Time of Flight (ToF). We derive homogeneous linear conditions for Time-of-Flight images of 3 or 4 points to be the projection of collinear or coplanar points respectively. The crucial part in our equations is played by the D/d-ratios of the ToF-d...

Surgical luminaires are an important tool for the surgeon, yet highlighting the wound of a patient is not trivial and surgical luminaires must meet stringent regulatory requirements. Optical requirements and performance indicators are described in the European Standard for surgical luminaires and they must be measured after construction. Surgeons a...

In an operating room, various measures are taken to prevent post-operative wound infection. A ceiling-mounted laminar downflow ventilation system provides clean air to the surgical site and instrument table to reduce the number of pathogenic particles. However, this flow is disrupted by the surgical luminaire, which may cause pathogenic particles t...

Moiré profilometry is a technique that can be used to scan a 3D object to obtain the corresponding CAD model. This has proven its importance in reverse engineering and quality control. However, the accuracy of projection Moiré profilometry depends strongly on the setup and the used processing algorithms. This article presents custommade freeware so...

Red Green Blue cameras (RGB) have yet a long history and a lot of industrial applications work at an accepted accuracy level. Based on photogrammetric principals, random image shots of the 3D-world can be combined to provide high resolution and more or less real-time 3D information from the scene. Industrial vision packages (like Halcon, OpenCV, Ma...

The accuracy of fringe projection profilometry strongly depends on the setup. In this article different setups are discussed, and compared using custom-made freeware simulation software. The best suited geometry for aberration-free measurements on small objects is implemented in a practical setup. By using specific telecentric lenses and different...

Profilometry is widely used as a control method in automation systems or for scanning and converting real objects into 3 dimensional models. Different techniques using grids and lasers can be found in literature. The available techniques can be divided into two main categories: temporal and spatial profilometry [1,2,3]. Most setups are based on the...