Transmittance of skew rays through metal light pipes

The transmittance of skew rays through metal light pipes is examined with ray tracing. The transmittance with respect to pipe length is compared with analytical approximations and with experimental data. The effects of pipe material, pipe shape, wavelength of the incident light, distribution of the incident light, and maximum angle of incidence on transmittance are examined. The transmittance is shown, in general, not to be exponential with respect to pipe length. Additionally, the effect on transmittance of elbows and gaps in a pipe is investigated.