The paint test system consists of a circular light source (transparent) sending a parallel beam towards the air-resin interface (rectangular, 2 mm * 2 mm). Below this interface there is another one representing the resin-substrate transition. A view of this configuration is given below:
Here is a side view of the arrangement:
The space between top and bottom interface is filled with a composite scatterer (the TiO2 and CdS particles). The distance between the interfaces, i.e. the thickness of the paint, is 100 microns. The concentration of the TiO2 and CdS particles can be varied in the model, like all other parameters and dimensions.
Four perfect mirrors enclose the scattering volume in order to avoid radiation leaving the test volume (reflecting boundary conditions). The next picture shows the four mirrors which are about to be moved to their final positions:
Finally we show the complete system with some test rays:
Above the light source there is a huge rectangular detector (10 m * 10 m) collecting all rays that leave the top surface in the upward direction. Since in the views shown above the observer looks downwards the detector is not visible.