Examining aberrations due to depth of field in holographic pupil replication waveguide systems

Pupil expansion using waveguide propagation and pupil replication has been a popular method of developing head-up displays and near-to-eye displays. This paper examines one of the limits of pupil replication, which involves projecting images at a finite distance through a single waveguide by holographic optical elements and seeing the image doubling artifact. A Zemax model and a demonstrator were developed to determine the cause of image doubling. A relationship between the designed outcoupled image distance of a waveguide, pupil size, optical path length, and angle of image doubling is established. In waveguide pupil replication, the internally propagating light should be close to collimated to mitigate image doubling. We also provide a solution to project the image at different distances, which is an important factor for some applications, such as automotive head-up display and the seamless integration of augmented reality information with the natural environment.