Quantitative modeling of laser speckle imaging

We have analyzed the image formation and dynamic properties in laser speckle imaging (LSI) both experimentally and with Monte-Carlo simulation. We show for the case of a liquid inclusion that the spatial resolution and the signal itself are both significantly affected by scattering from the turbid environment. Multiple scattering leads to blurring of the dynamic inhomogeneity as detected by LSI. The presence of a non-fluctuating component of scattered light results in the significant increase in the measured image contrast and complicates the estimation of the relaxation time. We present a refined processing scheme that allows a correct estimation of the relaxation time from LSI data.Comment: submitted to Optics Letter

Optical coherence tomography of the epidermal sulfakrilate surface strippings

Method of the epidermal surface biopsy (ESB) with the adhesive compositions is the alter-native to the classic his-tological examination. Materials and Methods. In this study medical adhesive "Sulfacrylate" was used, small portions of which had been spread on an object glass, and then on different skin areas. To study the structural organization of the samples ESB the technique of optical coherence tomography (ОСТ) was used. Results. We obtained the pictures that visualize the structural organization of the different layers of the epidermis in lichen planus, hyperkeratosis, scabies and other skin diseases. Conclusion. This technique allows non-invasive measurement of high-precision structure of different layers of the epidermis, which can be useful both for research and for the practical dermatology

Оптическая когерентная томография и поляриметрический анализ поверхностных биопсий кожи

The goal. Of this study was to develop and assess the efficacy of polarization probing of biotissues in vitro. The method is based on the determination of polarization parameters of scattered radiation. Materials and methods. The well-known superficial epidermis stripping method was applied using the Sulfacrylate self-sterile medical adhesive. Small portions of thin layers of the adhesive were applied to slide plates and then to different skin sites. The corneous layer in the normal condition and in case of skin diseases (psoriasis, lichen acuminatus, discoid lupus erythematosus, alopecia, itching and demodectic mange) was examined based on the optical coherence tomography (OCT) method using the 0CS1300SS device (Thorlabs Inc, USA). Results. The authors obtained pictures visualizing the structural organization of different layers of the epidermis using the superficial epidermis biopsy method in case of lichen acuminatus, hyperkeratosis, itching and other skin diseases. Conclusion. This method ensures non-invasive high-precision measurement of the structure of different layers of the epidermis, which may be useful both for research purposes and practical dermatology.Цель исследования. Разработка и оценка эффективности поляризационного зондирования биотканей in vitro. Метод основан на определении параметров поляризации рассеянного излучения. Материал и методы. Использовали общепризнанный метод поверхностных отрывов эпидермиса с помощью медицинского аутостерильного клея «Сульфакрилат», небольшие порции которого тонким слоем наносились на предметное стекло, а затем на различные участки кожного покрова. Роговой слой в норме и при кожных заболеваниях (псориаз, красный плоский лишай, дискоидная красная волчанка, алопеция, чесотка, демодекоз) изучали с помощью методики оптической когерентной томографии на аппарате ОСТ OCS1300SS (производство Thorlabs Inc, США). Результаты. Приведены картины, визуализирующие структурную организацию различных слоев эпидермиса, полученных с помощью методики поверхностной биопсии эпидермиса при красном плоском лишае, гиперкератозе, чесотке и других кожных заболеваниях. Заключение. Данная методика позволяет проводить неинвазивные высокоточные измерения структуры различных слоев эпидермиса, что может оказаться полезным как для научных исследований, так и для практической дерматологии

PHOTON MIGRATION IN PULP AND PAPER

Abstract The thesis clearly demonstrates that photon migration measurements allow characterization of pulp and paper properties, especially the fines and filler content of pulp, and the basis weight, thickness and porosity of paper. Pulp and paper are materials with a worldwide significance. Their properties strongly depend on the manufacturing process used. For efficient process control, the employed monitoring and measuring has to be fast. Therefore it is worthwhile to try to develop new approaches and techniques for such measurements. Recent advancements in optics offer new possibilities for such development. If two samples have different optical properties their photon migration distributions are different. The measurement of a photon migration distribution allows some features between two optically slightly dissimilar samples to be distinguished. Some simple measurements, which only yielded the photons' average time of flight, were made with an oscilloscope and a time-of-flight lidar. More precise measurements yielding photon pathway distribution or some selected characteristics like light pulse rise time, broadening, or fall time were measured with a streak camera. Two methods to assess photon path length distribution were introduced: particle determination with simulation, and streak camera with deconvolution. The basic properties for pulp are consistency and fines content and for paper the basic properties are thickness, basis weight and porosity. The influence on photon migration caused by changes in these basic properties was determined. As pulp and paper are rarely very basic, an additional property was demonstrated for both materials. For pulp it was the content of filler talc, and for paper it was the use of beaten pulp as a raw material. These additional properties were also distinguishable

The effect of radiation losses in localized fluorescence upon laser pumping of fluorescent random media

Background and Objectives: Excitation of fluorescence upon laser pumping of fluorescent multiple scattering media is a complex process that plays a key role in many applications of modern optics and laser physics, from optical biomedical diagnostics to controlling the parameters of functional materials for photonics and optoelectronics. The effect of radiation losses in local fluorescence emitters, which are associated with laser speckles in pumped random media, on the fluorescence output is considered. Materials and Methods: Within the framework of the concept of an ensemble of statistically independent local fluorescence emitters in a laser-pumped random medium, a model of radiation losses in an arbitrarily chosen local emitter is considered. The model takes into account both an extreme value of the cross section of radiation losses for a single emitter, which depends on its characteristic size and the concentration of fluorophore molecules in the medium, and the effect of radiation exchange with other emitters. The scattering properties of a laser-pumped fluorescent medium are considered as a suppressing factor for the ballistic radiation transfer between the local emitters. The modeled results are compared to the previously obtained empirical data on the effective cross section of radiation losses for Rhodamine-6G-saturated layers of close-packed anatase nanoparticles under pulsed laser pumping at the wavelength of 532 nm. Results: The relationship between the effective cross section of radiation losses and the characteristic size of the emitters, the concentration of fluorophore molecules, and the mean scattering free path of fluorescent radiation was obtained. It was found within the framework of the considered model that both the characteristic size of local emitters and the reduction factor to the cross section of radiation losses due to light transfer from other emitters are practically independent of the pump intensity, with the exception of a narrow interval of low intensities. On the other hand, the scattering length significantly affects these characteristics due to the “screening” effect in the case of expressed multiple scattering. Conclusion: Radiation exchange between local stochastic emitters of fluorescence radiation in laser-pumped random media is one of the key factors controlling the fluorescence response of the medium with increasing pump intensity. The considered phenomenological model makes it possible to adequately interpret the experimentally observed features of the behavior of the effective cross section of radiation losses for these systems. The obtained results can be used as a physical basis for the development of new approaches to laser probing of random media in terms of the interpretation of the experimental data

Biophotonics methods for functional monitoring of complications of diabetes mellitus

The prevalence of diabetes complications is a significant public health problem with a considerable economic cost. Thus, the timely diagnosis of complications and prevention of their development will contribute to increasing the length and quality of patient life, and reducing the economic costs of their treatment. This article aims to review the current state-of-the-art biophotonics technologies used to identify the complications of diabetes mellitus and assess the quality of their treatment. Additionally, these technologies assess the structural and functional properties of biological tissues, and they include capillaroscopy, laser Doppler flowmetry and hyperspectral imaging, laser speckle contrast imaging, diffuse reflectance spectroscopy and imaging, fluorescence spectroscopy and imaging, optical coherence tomography, optoacoustic imaging and confocal microscopy. Recent advances in the field of optical noninvasive diagnosis suggest a wider introduction of biophotonics technologies into clinical practice and, in particular, in diabetes care units