The transmittance and irradiance distribution at the exit aperture of a cylindrical mirror light pipe (MLP) have been measured and calculated for the cases of collimated and diffuse inputs. MLPs are an example of a nonimaging optical system that can concentrate light, which may give rise to problematic hotspots and glare either on any diffuser used at the exit aperture or in the illuminated room. It is shown in this work that use of a diffuser at the entrance aperture overcomes these problems without a marked reduction in transmission of a typical MLP.
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