Boris Clément Karamata

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Optical Coherence Tomography (OCT), a well-established imaging method based on low-coherence interferometry, provides cross-sectional images of the internal structure of biological samples with a resolution in the micrometer range. OCT was successfully applied on various tissues such as for instance the retina, the skin or a tooth. In highly scattering tissues like the skin, probing depth is limited to approximately 2mm, mainly due to insufficient rejection of multiply scattered light. Presently, the contri

The design of systems for solar light collection, modulation and/or distribution requires a thorough knowledge of their optical properties. The angular distribution of the scattered incident light flux, described by the Bidirectional Scattering Distribution Function (BSDF), can be measured with a step-by-step scanning goniophotometer but requires considerable time, especially when aiming at high angular resolution over a wide range and numerous incidence angles like in typical solar applications. Considerab

Optical concentration obtained by light confinement bears unique features that can increase the efficiency of a photochemical reactor. A suitable implementation of this method for a solar reactor is a series of parallel tubular receivers sealed in a slab-s ...

We briefly categorize and compare parallel goniophotometers, which are instruments capable of simultaneously measuring the far-field distribution of light scattered by a surface or emitted by a source over a large solid angle. Little is known about the acc ...

Two pairs of identical experimentation modules are being developed within the framework of a collaborative initiative named NOMAD – Network of Optimization Modalities in Architectural Design - between the Interdisciplinary Laboratory of Performance-Integrated Design (LIPID) and the Laboratory of Architecture and Sustainable Technologies (LAST), both at EPFL. NOMAD relates to a series of projects related to the optimization of the building envelope in a sustainability context. Based on comparative evaluation

We present a new model of optical coherence tomography (OCT) taking into account multiple scattering. A theoretical analysis and experimental investigation reveals that in OCT, despite multiple scattering, the field backscattered from the sample is general ...

A thorough knowledge of the angular distribution of light scattered by an illuminated surface under different angles is essential in numerous industrial and research applications. Traditionally, the angular distribution of a reflected or transmitted light ...

Dispersive samples introduce a wavelength dependent phase distortion to the probe beam. This leads to a noticeable loss of depth resolution in high resolution OCT using broadband light sources. The standard technique to avoid this consequence is to balance the dispersion of the sample by arranging a dispersive material in the reference arm. However, the impact of dispersion is depth dependent. A corresponding depth dependent dispersion balancing technique is diffcult to implement. Here we present a numerica

The design of a solar protection system that can minimize solar gains while maximizing daylight and view to the outside is particularly challenging in arid climates, such as in the Middle-East, where sand, wind and corrosion impose specific constraints. We ...

The two previously reported calculations of the amplitude distribution of speckles in optical coherence tomography, each based on a different mathematical formulation, yield different results. We show that a modification of an initial assumption in one of ...

Current spectroscopic optical coherence tomography (OCT) methods rely on a posteriori numerical calculation. We present an experimental alternative for accessing spectroscopic information in OCT without post-processing based on wavelength de-multiplexing and parallel detection using a diffraction grating and a smart pixel detector array. Both a conventional A-scan with high axial resolution and the spectrally resolved measurement are acquired simultaneously. A proof-of-principle demonstration is given on a

We describe a concept for a novel stationary solar concentrator that relies on a new self-adaptive optical valve, non-imaging optics and the integrating sphere principle. Our analytical model reveals that this unique combination theoretically allows reachi ...

A reliable computer simulation of natural and artificial lighting of an indoor environment requires the thorough knowledge of the angular intensity distribution of light scattered or emitted by the various objects involved such as the illuminated surfaces, the trans-illuminated windows or fenestration systems, as well as the luminaires. The angular intensity distribution of light flux reflected, transmitted or emitted as a function of the illumination angle can be measured with an instrument called goniopho

A simple method for the calibration of optical path difference modulation in low-coherence interferometry is presented. Spectrally filtering a part of the detected interference signal results in a high-coherence signal that encodes the scan imperfections and permits their correction. The method is self-referenced in the sense that no secondary high-coherence light source is necessary. Using a spectrometer setup for spectral filtering allows for flexibility in both the choice of calibration wavelength and th

Parallel optical coherence tomography in scattering samples is demonstrated using a 58 x 58 smart-pixel detector array. A femtosecond mode-locked Ti:Sapphire laser in combination with a free space Michelson interferometer was employed to achieve 4 mum longitudinal resolution and 9 mum transverse resolution on a 260 x 260 mum field of view. We imaged a resolution target covered by an intralipid solution with different scattering coefficients as well as onion cells. (C) 2002 Published by Elsevier Science B.V.

A new numerical a posteriori dispersion compensation technique for partial coherence interferometry and optical coherence tomography depth-scan signals is presented. This technique is based on numerical correlation of the depth-scan interferometer signal with a depth-variant kernel. Examples of dispersion compensated depth-scan signals obtained from microscope cover glasses are presented. (C) 2002 Elsevier Science B.V. All rights reserved.

A device for the preventative photodynamic therapy of secondary cataract has been developed. Disturbance of the epithelial cells of the crystalline lens during the primary cataract surgery and/or their migration thereafter can frequently generate secondary cataract. This can generally be prevented by destroying these epithelial cells. One approach is to expose them to a phototoxic dye which is then activated by selective exposure to light. For this purpose we designed a light distributor furnishing a torus-

Comparison of two illumination modes for wide-field optical coherence tomography has revealed that spatially coherent illumination generates coherent cross talk, causing significant image degradation, and that spatially incoherent illumination, with an adequate interferometer design, provides an efficient mechanism for suppression of coherent cross talk. This is shown by comparison of a pulsed laser with a thermal light source for a U.S. Air Force resolution target covered with a scattering solution made fr

Most current optical coherence tomography systems provide two-dimensional cross-sectional or en face images. Successive adjacent images have to be acquired to reconstruct three-dimensional objects, which can be time consuming. Here we demonstrate three-dimensional optical coherence tomography (3D OCT) at video rate. A 58 by 58 smart-pixel detector array was employed. A sample volume of 210x210x80 mum(3) (corresponding to 58x58x58 voxels) was imaged at 25 Hz. The longitudinal and transverse resolutions are 3

We present a comprehensive study of multiple-scattering effects in wide-field optical coherence tomography (OCT) realized with spatially coherent illumination. Imaging a sample made of a cleaved mirror embedded in an aqueous suspension of microspheres reve ...

Boris Clément Karamata

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Multiple scattering in wide-field optical coherence tomography

Limits and artefacts of reflective imaging goniophotometers for complex solar façade systems

Design of a light confining concentrator for a solar photochemical reactor and upper bound to the method

Origin and nature of measurement bias in catadioptric parallel goniophotometers

NOMAD - Network of Optimization Modalities in Architectural Design

Multiple scattering in optical coherence tomography. I. Investigation and modeling

Revisiting parallel catadioptric goniophotometers

Numerical dispersion compensation for Partial Coherence Interferometry and Optical Coherence Tomography

Concept, Design and Performance of a Shape Variable Mashrabiya as a Shading and Daylighting System for Arid Climates

Speckle statistics in optical coherence tomography

Spectroscopic optical coherence tomography based on wavelength de-multiplexing and smart pixel array detection

Stationary solar concentrator delivering beyond the étendue law with homogeneous illumination

A review and analysis of parallel goniophotometry

Self-referenced method for optical path difference calibration in low-coherence interferometry

Parallel optical coherence tomography in scattering samples using a two-dimensional smart-pixel detector array

Dispersion compensation for optical coherence tomography depth-scan signals by a numerical technique

A fibreoptic light distributor for the preventative photodynamic therapy of secondary cataract

Spatially incoherent illumination as a mechanism for cross-talk suppression in wide-field optical coherence tomography

Video-rate three-dimensional optical coherence tomography

Multiple scattering in optical coherence tomography. II. Experimental and theoretical investigation of cross talk in wide-field optical coherence tomography