Holographic combiners for augmented reality applications fabricated by wave front recording

Abstract

Recently, holographic optics such as volume holographic optical elements (vHOEs) receive increasing attention as optical combiners in augmented reality (AR) applications. Especially vHOEs fabricated by means of wave front printing have the potential to realize complex optical functions with high diffraction efficiency while maintaining excellent transmittance. We present the recording of a holographic combiner for AR applications fabricated by means of individually modulated recording wave fronts in our extended immersion-based holographic wave front printer setup. Holographic elements from our setup are made up of individual sub-holograms, so called Hogels. The implementation of two phase-only reflective spatial light modulators (SLMs) allows for the recording of Hogels and consequently vHOEs in a wide range of different configurations. Large-area vHOEs are achieved by adjacent recording of multiple Hogels in a step-wise fashion. Our immersion-based printer setup ensures a high numerical aperture for the recording configuration, which is directly linked to a wide angular range of possible replay configurations for wave front propagation in air. We present a reflective vHOE realizing a large off-axis to on-axis wave front transformation suitable as holographic combiner for retinal scanning displays. The vHOE is characterized by evaluating the diffractive properties of the hologram’s volume gratings, as well as investigating the vHOE’s combiner characteristics by means of field of view (FoV) and eye box size evaluation.