If wearing a virtual reality or augmented reality headset is ever to become commonplace, hardware manufacturers will need to figure out how to make the devices small and lightweight while ensuring their images are sharp and clear. Unfortunately, this task faces a key limitation in optics: Conventional lenses are curved glass objects that focus different wavelengths of light in different locations, which would show viewers blurry images. As a result, pretty much anything with a lens – from tiny smartphone cameras to large-scale projectors – uses multiple lenses, which add weight, thickness and complexity, increasing cost.