Lightweight spatial-multiplexed dual focal-plane head-mounted display using two freeform prisms

Accommodation and convergence play critical roles in the natural viewing of three-dimensional (3D) scenes, and these must be accurately matched to avoid visual fatigue. However, conventional stereoscopic headmounted displays lack the ability to adjust accommodation cues. This is because they only have a single, fixed image plane, but the 3D virtual objects generated by a pair of stereoscopic images are displayed at different depths, either in front or behind the focal plane. Therefore, in order to view objects clearly, the eyes are forced to converge on those objects while maintaining accommodation fixed on the image plane. By employing freeform optical surfaces, we design a lightweight and wearable spatial-multiplexed dual focal-plane head-mounted display. This display can adjust the accommodation cue in accordance with the convergence cue as well as generate the retinal blur cue. The system has great potential applications in both scientific research and commercial market.