Two-flux Kubelka-Munk Research Articles

An Optical Algorithm for Relative Thickness of Each Monochrome Component in Multilayer Transparent Mixed Films

A modification of the two-flux Kubelka-Munk (K-M) model was proposed to describe the energy conservation of scattered light in colored mixed material with a defined scattered photometric, which is applied for the relative quantity distribution of each colored monochrome component in mixed material. A series of systematical experiments demonstrated a higher consistency with the reference quantity distribution than the common Lambert-Beer (L-B) law. Its application in the fibrogram of each component for measuring the cotton fiber’s length was demonstrated to be good, extending its applicability to white and dark colored blended fibers, the length of which is harder to measure using L-B law.

Optimization of Band Selection in Multispectral and Narrow-Band Imaging: An Analytical Approach.

The contrast ratio has been proposed for quantification of image quality of subsurface inhomogeneities in the skin. Based on the two-flux Kubelka-Munk model, we developed an analytical approach which links the contrast ratio with optical tissue parameters. We obtained an explicit analytical solution for the dependence of maximal contrast ratio on optical tissue parameters. Then, we linked the minimally observable contrast ratio (cmin) with the bit depth of the camera, d: cmin=1/(2d-1). Based on this analysis we were able to derive an explicit expression, which links camera properties with the minimally detectable changes in optical tissue parameters (both scattering and absorption). The proposed analytical model can be used for rapid assessment and optimization of multispectral and narrow band imaging techniques and for estimation of the accuracy of imaging techniques. The developed model confirms the utility of the contrast ratio for tissue imaging.

Effect of scattering nanoparticles on the curing behavior and conversion gradient of UV-curable turbid systems: two-flux Kubelka-Munk approach

Abstract UV-curable systems based on polyethylene glycol diacrylate (PEG-DA) containing various amounts of scattering silicon nitride nanoparticles were studied by real-time Fourier transform infrared (RT FTIR) and real-time UV–visible (RT UV–visible) spectroscopies. Increasing the percentage of nanoparticles into the UV-curable systems caused the photopolymerization rate and final double-bond conversion to increase. Principal component analysis (PCA) was applied to transmission spectra of samples with various amounts of nanoparticles. Results showed a significant correlation between the two most important principal components and the absorption and scattering phenomena. Absorption and scattering coefficients were evaluated from the reconstructed data using a two-flux Kubelka-Munk theory and radiative flux behavior was calculated. Conversion gradients inside a thick layer were simulated using the radiative flux and curing kinetics experimental values. Finally, the effect of scattering particles on the curing depth was studied.

Nonlinear Behavior of the Autofluorescence Intensity on the Surface of Light-Scattering Biotissues and its Theoretical Proof.

In the up-to-date medical laser fluorescence spectroscopy (LFS) in vivo, there is a problem of quantification of fluorophores concentrations in optically-turbid biotissues by measurements of the laser induced autofluorescence flux on the surface of these tissues. One of the main problems is: whether the flux depends linearly or non-linearly on the concentration of fluorophores in tissues? The purpose of this work was both experimental and theoretical study of the character of dependencies between measured fluorescence intensities and fluorophores concentrations in optically-turbid media. In the experimental part of our study, measurements of the superficial fluorescence on phantoms at various known concentrations of fluorophores in them were carried out. As a result, experimental dependencies of registered intensities of the laser-induced autofluorescence emission were plotted against fluorophore concentrations. In the theoretical part of the study, the analytical solution for the fluorescence emission by Kokhanovsky's method based on the well-known two-flux Kubelka-Munk approach (KMA) was used. In addition, in our study the Kokhanovsky's method was modified by its association with our improved KMA, allowing us to receive exact analytical solutions for boundary intensities collected by optical probes. As a result, a set of theoretical curves describing the influence of fluorophore concentrations on the registered autofluorescence intensities was obtained, as well. Both experimental and theoretical results show a good qualitative agreement with each other. Also, these results demonstrate that the dependence of the fluorescence intensity on tissues' optical properties and on the concentration of fluorophores in light-scattering tissues can be both nonlinear and non-monotonic.

Investigation of the optical characteristics of composite materials based on cadmium sulfide nanoparticles stabilized in a high-pressure polyethylene matrix

Composite materials based on cadmium sulfide nanoparticles in an inert dielectric matrix of high-pressure (low-density) polyethylene are experimentally studied. It is shown how the size and weight concentration of nanoparticles in the bulk of the stabilizing matrix affect the nanocomposite absorption. The experimental results are interpreted based on the two-flux Kubelka-Munk model.