Equiangular-spiral bent lightpipes with arbitrary bent angle

摘要

A recent study proposed the concept of a leakage-free bent lightpipe with an equiangular-spiral shape [S.-C Chu, J.-L Chern, Opt. Lett. 30 (2005) 3006]. This paper extends the design of a leakage-free equiangularspiral bent lightpipe with arbitrary-bend-angle and addresses in detail the mathematical formalism required to build such an equiangular-spiral bent lightpipe. Furthermore, a comparison of the proposed equiangular-spiral bent lightpipe and a conventional circular bent lightpipe is provided. Numerical verifications are discussed, and experimental explorations with different bent shapes and angles are carried out for comparison. Results show that equiangular-spiral bent lightpipes with different bent angles exhibit a theoretical 100percent transmission with more than 76percent efficiency when practically propagating, which is much better than conventional circular bent lightpipes. The output irradiance distributions of bent light-pipes with different bent shapes are also investigated.