The influence of a light pipe on the coherence properties in laser projectors

Light pipes are key optical components used in projection systems to transport and homogenize light from the source towards the light valve. They can provide a uniform light distribution at their output as a result of multiple internal reflections. In laser projection systems, such light pipes are useful in combination with a laser-light module consisting of one or more single-mode lasers and a rotating diffuser. The partially coherent light emanating from the rotating diffuser is transported and homogenized towards the end of the light pipe. Consequently, propagation through the light pipe will also modify the coherence properties of the laser light. In this paper, a computationally efficient simulation model is presented to propagate partially coherent light through a homogenizing rectangular light pipe. The resulting coherence function clearly differs from that of free-space propagation over the same optical path length. The implications of these results on, for example, the appearance of speckle are discussed in further detail. The simulation results are experimentally verified using a reversing wavefront Michelson interferometer. The approach described in this paper can be extended further to investigate other types of light pipes, such as tapered light pipes or even more complex ones.

ISBN:Optical Modelling and Design III

Jaar van publicatie:2014

Trefwoorden:photonics, lasers