Abstract:
When a beam of light is incident on a translucent sample, a significant fraction of the light is scattered at
high angles. Some of this scattered light may be trapped inside the substrate through multiple reflections and
total internal reflection, similar to light coupling into an optical fiber. The trapping depends on factors such
as the surface roughness of the external surfaces and/or the size and distribution of scattering particles inside
the sample. The scattered light may thus escape out of the sample at a shifted position relative to the incident
beam. This leads to port losses in an integrating sphere. The detected signal from the light entering the sphere
then underestimates the hemispherical transmittance. In this paper the signal versus lateral position has been
measured in an attempt to estimate the error and to find an extrapolation procedure for the correct transmittance
value. The lateral measurements were carried out by moving a detector behind the sample, a procedure carried
out at several angles of incidence. Different illumination methods have also been studied both theoretically and
experimentally to further investigate what effect light trapping can have when characterising scattering samples.
