Sparse ellipsometry: portable acquisition of polarimetric SVBRDF and shape with unstructured flash photography

Ellipsometry techniques allow to measure polarization information of materials, requiring precise rotations of optical components with different configurations of lights and sensors. This results in cumbersome capture devices, carefully calibrated in lab conditions, and in very long acquisition times, usually in the order of a few days per object. Recent techniques allow to capture polarimetric spatially-varying reflectance information, but limited to a single view, or to cover all view directions, but limited to spherical objects made of a single homogeneous material. We present sparse ellipsometry, a portable polarimetric acquisition method that captures both polarimetric SVBRDF and 3D shape simultaneously. Our handheld device consists of off-the-shelf, fixed optical components. Instead of days, the total acquisition time varies between twenty and thirty minutes per object. We develop a complete polarimetric SVBRDF model that includes diffuse and specular components, as well as single scattering, and devise a novel polarimetric inverse rendering algorithm with data augmentation of specular reflection samples via generative modeling. Our results show a strong agreement with a recent ground-truth dataset of captured polarimetric BRDFs of real-world objects

Electromagnetic Waves

This book is dedicated to various aspects of electromagnetic wave theory and its applications in science and technology. The covered topics include the fundamental physics of electromagnetic waves, theory of electromagnetic wave propagation and scattering, methods of computational analysis, material characterization, electromagnetic properties of plasma, analysis and applications of periodic structures and waveguide components, and finally, the biological effects and medical applications of electromagnetic fields

Advances in the Physics of Stars - in Memory of Prof. Yuri N. Gnedin

This reprint, which was edited by Prof. Dr. Nazar R. Ikhsanov, Prof. Dr. Galina L. Klimchitskaya, and Prof. Dr. Vladimir M. Mostepanenko, contains research and review articles published in a Special Issue of the journal Universe in memory of outstanding astrophysicist Prof. Dr. Yuri N. Gnedin, who organized and led the Department of Astrophysics at the famous Pulkovo Observatory of the Russian Academy of Sciences for several decades. In these articles, the reader will find new and intriguing ideas in several topical problems of astrophysics as well as comprehensive and readily accessible sketches of a few recently performed investigations

Single Pixel Polarimetric Imaging through Scattering Media

Compared to pure intensity-based imaging techniques, polarimetric imaging can provide additional information, particularly about an imaged object's compositional, morphological and microstructural properties. The value of polarimetric imaging has already been demonstrated in various applications, such as early glaucoma detection and cancer discrimination. Its applicability, however, to practical in vivo imaging situations is limited as the object of interest is often located behind a scattering layer, such as biological tissue, which scrambles both the spatial and polarimetric information about the object that is contained in the propagating light. As such, this work set out to find a means of conducting polarimetric imaging through scattering media. Under the assumption that it is possible to illuminate the object plane with the required spatial patterns, single pixel cameras can enable imaging in scattering environments and were hence thoroughly investigated in this thesis as a route to polarimetric imaging through scattering media. A theoretical model for single pixel polarimetric imaging was first developed, and conditions under which the proposed method was feasible were identified and verified using 2D coupled line dipole simulations. The proposed method was further tested through experiments conducted using an in-house custom-built setup, composed of off-the-shelf components. To mitigate noise and to ensure that the obtained polarimetric image was physical, a constrained least squares algorithm was proposed and implemented. Experiments with various test objects hidden behind scattering phantoms showed that single pixel polarimetric imaging was able to successfully reconstruct the polarimetric images of the hidden object, whereas a spatially resolved detector in the same configuration resulted in an image that bore no resemblance to the test object. Further experiments that were conducted with the same test objects hidden behind chicken breast slices were, unfortunately, unable to recover an accurate polarimetric image of the hidden object. Additional investigations identified two factors that had likely affected the image reconstruction - spatial inhomogeneity and temporally varying transmittance of the chicken breast, both of which were unaccounted for in the data processing. On the basis of the experiments and simulations conducted in this work, single pixel polarimetric imaging was found to be a feasible approach for polarimetric imaging through scattering media. Finally, further improvements to establish single pixel polarimetric imaging as a practical technique are discussed.Open Acces

Interferometric observations to analyze circumstellar environments and planetary formation

Protoplanetary disks have a rich structure, with different physics playing a role in different regions of the disk. They are under constant evolution, due to a combination of various physical and chemical processes, e.g., accretion, photo-evaporation, gas-dust interactions, grain growth, and the interaction with protoplanets. The dynamic ranges involved span orders of magnitudes on spatial scales, orbital times, temperatures, and dust- or gas-densities. The extreme dynamic ranges involved in the structure and composition of these objects mean that very different observational techniques have to be combined together to probe their various regions. This work makes use of new interferometric and spectroscopic measurements in the infrared, together with published mid-infrared images and spectral energy distribution fluxes from UV to mm-wavelength, to instruct a new comprehension of the well-known IRS48 object, and uncover part of the delicate balance of physical processes at stake. This PhD reports the first direct imaging of the full extents of a polycyclic aromatic hydrocarbon and very small grains ring in a young circumstellar disk, presents a revised model for the IRS48 object to explain the rich and complex dust- and gas-environment observed from near-infrared to centimeter wavelengths. Also, the spectral type of the spectroscopic binary MWC361 is determined. This will lead to a precise characterization of the stellar parameters of this binary, opening a new window on the studying of the disappearance of the circumsecondary disk of the binary, while the circumprimary disk is still present. The leitmotif throughout this thesis is the understanding of the last moments of circumstellar disks, and the search for the processes which dissipate them. This particular step of the disk-evolution is one the most mysterious to date, yet it sets critical constraints on the by-product of circumstellar disks, exoplanets

The Twenty-Fifth Lunar and Planetary Science Conference. Part 3: P-Z

Various papers on lunar and planetary science are presented, covering such topics as: impact craters, tektites, lunar geology, lava flow, geodynamics, chondrites, planetary geology, planetary surfaces, volcanology, tectonics, topography, regolith, metamorphic rock, geomorphology, lunar soil, geochemistry, petrology, cometary collisions, geochronology, weathering, and meteoritic composition