Elimination of ghost image in expanded viewing angle head-up display systems

We present an optical set up that significantly reduces the ghost images appearing due to multiple reflections on both surfaces of the combiner (typically the windshield) of head-up display (HUD) systems. The method is based on an optimized polarization correcting optics attached to the HUD projector. For the quantitative investigation of the ghost images, we calculate the ghost image suppression ratio as a function of viewing direction using a custom algorithm based on ray tracing and Jones-vector formalism. We also present experimental results on the proposed configurations exhibiting very good agreement with calculation results. As a result, the ghost image free viewing area of polarization-type HUDs can be increased more than fourfold.