Figure 2
Exemplary illustration of the data processing procedure. As described, in the last step of the SP-DRI method two diffuse reflectance data sets are divided one by another pixel by pixel. The result of this division is shown for one set of optical properties and one capillary diameter value (here: \(\emptyset_{{{\text{cap}}}} = 14\;\upmu{\text{m}}\) in (a). For the remaining capillary diameter values, such a data set is also existing. These data sets are then intersected parallelly to the y axis at x = 610, resulting in the graph shown in (b). Per capillary diameter, the three capillary loops (each located at the inflection point between a local maximum and the subsequent local minimum of the SP-DRI signal curve) at this x position are visible. A \(K_{{{\text{norm}}}}\) value can be calculated per capillary diameter and loop; these are finally plotted (solid lines and markers) in (c) together with the fitting curves of the linear regressions (dashed lines). For each regression, there is one parameter set β0β0 (intercept) and β1β1 (slope). The data set belonging to the third capillary loop exhibits two missing values. In (d), a flowchart of this data handling is provided together with the hypothesis resulting from this.
