Cascaded displays: spatiotemporal superresolution using offset pixel layers

We demonstrate that layered spatial light modulators (SLMs), subject to fixed lateral displacements and refreshed at staggered intervals, can synthesize images with greater spatiotemporal resolution than that afforded by any single SLM used in their construction. Dubbed cascaded displays, such architectures enable superresolution flat panel displays (e.g., using stacks of liquid crystal displays (LCDs)) and digital projectors (e.g., relaying the image of one SLM onto another). We introduce a comprehensive optimization framework, leveraging non-negative matrix and tensor factorization, that decomposes target images and videos into multi-layered, time-multiplexed attenuation patterns---offering a trade-off between image brightness, spatial resolution, and refresh rate. We develop a real-time dual-layer factorization method that quadruples spatial resolution and doubles refresh rate. Compared to prior superresolution displays, cascaded displays place fewer restrictions on the hardware, offering thin designs without moving parts or the need for temporal multiplexing. We validate these concepts using three prototypes: printed multi-layer films, a dual-modulation liquid crystal on silicon (LCoS) projector, and a dual-layer LCD, with the latter emphasizing head-mounted display (HMD) applications.