US Patent 11650368 Electronic device with an optical coupling layer and diffractive layer

An electronic device may have a display that displays an image. The image may be viewed through a display cover layer that overlaps the display. The display cover layer may include an optical coupling layer such as a coherent fiber bundle. A pixel expansion layer such as a diffractive layer may be incorporated between the optical coupling layer and a protective layer. The diffractive layer may create duplicate pixels to occupy otherwise non-light-emitting areas on the output surface of the display cover layer. The diffractive layer may also create duplicate pixels that overlap adjacent pixels to allow for brightness averaging. An adhesive layer or the protective layer may be used to form diffractive elements for the diffractive layer. An adhesive layer having a high index of refraction may be interposed between the optical coupling layer and the display panel to mitigate undesired reflections of ambient light.