Evaluation of light scattering properties and chromophore concentrations in skin tissue based on diffuse reflectance signals at isosbestic wavelengths of hemoglobin

Optical Review - We investigate a method to evaluate light-scattering properties and chromophore concentrations in human skin tissue through diffuse reflectance spectroscopy using the reflectance...     

Color adjustment algorithm adapted to the spectral reflectance estimation method

We are developing a daily health monitoring system that uses mobile phones with cameras and analyzes physiological conditions from R, G, and B intensity levels. However, since it is affected by various imaging conditions of the image input, color correction is required for accurate health monitoring. Therefore, we developed and validated a colorcorrection algorithm to derive reliable color information by correcting the spectral reflectance using the Wiener estimation and a color chart.     

In vivo estimation of optical properties of rat liver using single-reflectance fiber probe during ischemia and reperfusion

Optical Review - To quantify the changes in optical properties of in vivo rat liver tissue, we applied diffuse reflectance spectroscopy (DRS) system using single-reflectance fiber probe during...     

In vivo multispectral imaging of the absorption and scattering properties of exposed brain using a digital red–green–blue camera

Optical Review - To evaluate multi-spectral images of the absorption and scattering properties in the cerebral cortex of rat brain, we investigated spectral reflectance images estimated by the...     

Decay Time of 2.09 eV Luminescence of S2--Vacancy Centers and Their Optical and Thermal Stability in NaCl:S2 Crystals

An investigation was carried out on decay time of the 2.09 eV emission of S²–vacancy pair centers in NaCl crystals. When the crystal was excited by a pulsed 337 nm light from an N₂ laser, the 2.09 eV yellow luminescence principally decayed with the lifetime of 14.2 μs at low temperatures, and exhibited a weak thermal quenching with an activation energy of 51.3 meV above about 150 K. Such S^2--vacancy pair centers responsible for the 2.09 eV luminescence were thermally stable at room temperature, and not bleached even when exposed to ultraviolet lights below about 5 eV. Thus, the 2.09 eV emission center possibly can be used as a solid-state laser active center working at room temperature.     

Adaptive exponential approximation of optical density ratio using third-order regression equations for depth profiling of a blood inclusion in a skin tissue model

We propose the use of the third-order multiple regression equations in approximating an optical density ratio with an adaptive exponential function for measuring depth and thickness of a blood inclusion embedded in a skin tissue model. To ensure accuracy of the exponential approximation, we investigated numerically various relations of optical density ratios versus depth and thickness, on the basis of Monte Carlo simulations for a layered skin tissue model. The third-order multiple regression analysis based on the relations above was used to derive regression equations for the determination of depth and thickness. Experiments with skin tissue phantoms were used to assess this approach.     

Simulated reflectance spectra and point spread functions in database constructed by moderate grouping of nine layers in skin model

Optical Review - This paper presents a numerical study on simulated spectra and point spread functions in the database that we constructed by moderate grouping of nine layers in a skin model. The...     

Depth visualization of a local blood region in skin tissue by use of diffuse reflectance images

A simple method is proposed for visualizing the depth distribution of a local blood region in skin tissue by using diffuse reflectance images at two isosbestic wavelengths of hemoglobin, 420 and 585 nm. Monte Carlo simulation of light transport specifies a relation between optical densities and the depth of the region under given concentrations of melanin in the epidermis and blood in the dermis. Phantom and in vivo experiments were performed to show the usefulness of the method.