Projection-type see-through near-to-eye display with a passively enlarged eye-box by combining a holographic lens and diffuser

We propose a projection-type sec-through near-to-eye display by combining two holographic optical elements (HOEs), a holographic lens with the on-axis projection configuration and a holographic diffuser. The proposed method provides an enlarged eye-box by virtue of diffusing properties of an HOE diffuser (HOED) without any temporal multiplexing methods. In this paper, a thorough analysis on imaging characteristics of an HOE lens (HOEL) according to the projection configuration is provided, so that we optimize the recording geometry of the HOEL with the passively enlarged eye-box. The theoretical analysis is validated by simulation results using a volume hologram model in OpticStudio. As experimental verifications, we realize a prototype of the proposed method using the photopolymer-based HOEs in a single color. The fabricated HOEL and HOED show high transmittance of 84.9% and 62.2%, respectively. By using the fabricated HOED with a diffusing angle over 20 degrees and an angular selectivity of 8.7 degrees, the prototype successfully provides see-through images with the eye-box larger than 5 mm in width. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement