A gloss sensor for optically measuring the gloss of a moving surface
includes a housing having an exterior surface which is generally parallel
with the moving surface. A light source is carried by the housing and
configured for emitting a source beam of light. At least one light
detector is carried by the housing. An optical prism is mounted to the
housing at the exterior surface. The prism is configured to split the
source beam into a reference beam which is reflected by the prism
internally within the housing to the one or more light detectors, and a
measurement beam which passes through the prism and is reflected by the
moving surface to the one or more light detectors.