Color Change of Commercial Resin Composited with Different Photoinitiators

Camphorquinone (CQ) is the most commonly used photoinitiator in light-cured dental resin composites. However CQ is associated with a yellowing effect, which has led manufacturers to add alternative initiators into resin composites to reduce the amount of CQ used. The color change upon polymerization by light and aging in artificial saliva and room air of 8 commercial traditional or bulk-fill resin composites with or without additional photoinitiator(s) beside CQ was studied. The three traditional resin composites with CQ and additional photoinitiator(s) tested were Tetric EvoCeram (Ivoclar Vivadent), AELITE LS Posterior (Bisco), and Vit-l-escence (Ultradent). The two bulk-fill resin composites with CQ and additional photoinitiator(s) tested were Tetric EvoCeram Bulk Fill (Ivoclar Vivadent) and HyperFIL (Parkell, dual cure). The control resin composites with CQ only were Heliomolar (Ivoclar Vivadent, traditional), BEAUTIFIL-Bulk (Shofu, bulk-fill) and SonicFill 2 (Kerr, bulk-fill). Sixteen specimens for each material were prepared with Teflon disc molds (7 mm diameter x 2 mm thickness) and light cured for 40 seconds with a quartz-tungsten-halogen light-curing unit. Samples were aged at 37°C in room air or artificial saliva (n=8). Color measurements were obtained with a spectrophotometer before and after polymerization and after aging for up to three months. Color change was calculated using CIELab and CIEDE2000 formulae. One way and two way ANOVA and a post-hoc SNK test was conducted for statistical analysis. Commercial light-cured resin composites with additional photoinitiators beside CQ had greater color change upon polymerization than those with CQ only. Color changes with aging tended to be greatest within the first hour after light curing, but was not considered clinically perceptible on any resin composites tested except HyperFIL. Tetric EvoCeram Bulk Fill showed good color stability that was comparable to the traditional resin composites upon aging

Segmentation of Melanoma Skin Lesion Using Perceptual Color Difference Saliency with Morphological Analysis

The prevalence of melanoma skin cancer disease is rapidly increasing as recorded death cases of its patients continue to annually escalate. Reliable segmentation of skin lesion is one essential requirement of an efficient noninvasive computer aided diagnosis tool for accelerating the identification process of melanoma. This paper presents a new algorithm based on perceptual color difference saliency along with binary morphological analysis for segmentation of melanoma skin lesion in dermoscopic images. The new algorithm is compared with existing image segmentation algorithms on benchmark dermoscopic images acquired from public corpora. Results of both qualitative and quantitative evaluations of the new algorithm are encouraging as the algorithm performs excellently in comparison with the existing image segmentation algorithms

Benchmarking of objective quality metrics for HDR image quality assessment

Recent advances in high dynamic range (HDR) capture and display technologies have attracted a lot of interest from scientific, professional, and artistic communities. As any technology, the evaluation of HDR systems in terms of quality of experience is essential. Subjective evaluations are time consuming and expensive, and thus objective quality assessment tools are needed as well. In this paper, we report and analyze the results of an extensive benchmarking of objective quality metrics for HDR image quality assessment. In total, 35 objective metrics were benchmarked on a database of 20 HDR contents encoded with 3 compression algorithms at 4 bit rates, leading to a total of 240 compressed HDR images, using subjective quality scores as ground truth. Performance indexes were computed to assess the accuracy, monotonicity, and consistency of the metrics estimation of subjective scores. Statistical analysis was performed on the performance indexes to discriminate small differences between two metrics. Results demonstrated that HDR-VDP-2 is the most reliable predictor of perceived quality. Finally, our findings suggested that the performance of most full-reference metrics can be improved by considering non-linearities of the human visual system, while further efforts are necessary to improve performance of no-reference quality metrics for HDR content

Development of a reflective optoelectronic method for determining the colorimetricvalues of the color of printed samples

U okviru ove doktorske disertacije je razvijena refleksiona optoelektronska metoda za određivanje kolorimetrijskih vrednosti boje štampanih uzoraka. Predložena metoda bazirana je na estimaciji reflektovanog spektra elektromagnetnog zračenja u vidljivom opsegu talasnih dužina. Na bazi metode dizajniran je senzorski sistem koji se sastoji od svetlosnih LED izvora na predajnoj i širokopojasnog silicijumskog fotodetektora na prijemnoj strani. Rezolucija A/D konvertora pri merenju intenziteta reflektovanih signala određena je sa 12 bita, dok je pokrivenost spektra LED izvorima ograničena na 6 tačaka, između kojih se vrši interpolacija. Ponovljivost sistema je ±0.27%. Razlike u boji ΔE00 koje predstavljaju grešku merenja, računate su u odnosu na referentnu spektrofotometrijsku metodu i nalaze se unutar granica tolerancije (0-5) za sve testirane uzorke. U tezi je takođe data i korekciona metoda bazirana na mašinskom učenju, koja je znatno redukovala ovu grešku ΔE00 na vrednost 3.As part of this doctoral thesis a reflection-based optoelectronical method for determening colorimetric values of the color of printed samples was developed. The proposed method is based on the estimation of the reflected spectrum of electromagnetic radiation in the visible spectrum (of vawelenghts). On the basis of this method a sensing sustem was designed, consisting of LED sources on the emitting side and a wide range silicium photodetector on the recevieng side. Resolution of the spectral sensitivity of the sensing system is defined with 11 bits, while the coverage of the spectrum by the LED sources is limited to 6 points, between which interpolation was preformed. The repeatability of the system is +-27%. Diferences in color ΔEoo, which represent the measurement error, were calculated with the respect to the referent spectrophotometric method and are within the boundary of tolerance (0-5) for all tested samples. Furthermore in the thesis a corrective method, based on ANN, was presented, which significantly reduced the error to 3

Quality of Experience in Immersive Video Technologies

Over the last decades, several technological revolutions have impacted the television industry, such as the shifts from black & white to color and from standard to high-definition. Nevertheless, further considerable improvements can still be achieved to provide a better multimedia experience, for example with ultra-high-definition, high dynamic range & wide color gamut, or 3D. These so-called immersive technologies aim at providing better, more realistic, and emotionally stronger experiences. To measure quality of experience (QoE), subjective evaluation is the ultimate means since it relies on a pool of human subjects. However, reliable and meaningful results can only be obtained if experiments are properly designed and conducted following a strict methodology. In this thesis, we build a rigorous framework for subjective evaluation of new types of image and video content. We propose different procedures and analysis tools for measuring QoE in immersive technologies. As immersive technologies capture more information than conventional technologies, they have the ability to provide more details, enhanced depth perception, as well as better color, contrast, and brightness. To measure the impact of immersive technologies on the viewersâ QoE, we apply the proposed framework for designing experiments and analyzing collected subjectsâ ratings. We also analyze eye movements to study human visual attention during immersive content playback. Since immersive content carries more information than conventional content, efficient compression algorithms are needed for storage and transmission using existing infrastructures. To determine the required bandwidth for high-quality transmission of immersive content, we use the proposed framework to conduct meticulous evaluations of recent image and video codecs in the context of immersive technologies. Subjective evaluation is time consuming, expensive, and is not always feasible. Consequently, researchers have developed objective metrics to automatically predict quality. To measure the performance of objective metrics in assessing immersive content quality, we perform several in-depth benchmarks of state-of-the-art and commonly used objective metrics. For this aim, we use ground truth quality scores, which are collected under our subjective evaluation framework. To improve QoE, we propose different systems for stereoscopic and autostereoscopic 3D displays in particular. The proposed systems can help reducing the artifacts generated at the visualization stage, which impact picture quality, depth quality, and visual comfort. To demonstrate the effectiveness of these systems, we use the proposed framework to measure viewersâ preference between these systems and standard 2D & 3D modes. In summary, this thesis tackles the problems of measuring, predicting, and improving QoE in immersive technologies. To address these problems, we build a rigorous framework and we apply it through several in-depth investigations. We put essential concepts of multimedia QoE under this framework. These concepts not only are of fundamental nature, but also have shown their impact in very practical applications. In particular, the JPEG, MPEG, and VCEG standardization bodies have adopted these concepts to select technologies that were proposed for standardization and to validate the resulting standards in terms of compression efficiency