Before revision: Theory The general setup for collimated transmission is as follows: 1) A collimated light source travels through the sample 2) Transmitted light is filtered by two pinholes 3) A photodetector collects the transmitted (mainly ballistic) photons center| upright=1.8|Illustration of collimated transmission method A clear medium, whose refractive index closely matches that of the sample to be tested, must be measured to provide a reference ballistic-light signal Io.
After revision: Theory The general setup for collimated transmission is as follows: 1) A collimated light source travels through the sample 2) Transmitted light is filtered by two pinholes 3) A photodetector collects the transmitted (mainly ballistic) photons upright=1.8|Illustration of collimated transmission method A clear medium, whose refractive index closely matches that of the sample to be tested, must be measured to provide a reference ballistic-light signal Io.