Human Eye Can See Ghost Images

Scientists have discovered that the human eye has a spooky ability. It can detect "ghost images."

These are images that are encoded in random patterns, previously thought only detectable by computer. But in a new paper posted online on the preprint server arXiv, scientists in Scotland at Heriot-Watt University in Edinburgh and the University of Glasgow have found that the human eye itself can do the required computations.

"Although the brain can't individually see them, the eye is somehow detecting all of the patterns, and then keeping the information there and summing everything together," said study co-author Daniele Faccio, a physics professor at Heriot-Watt University. [The Most Amazing Optical Illusions (and How They Work)]

Making ghost images
In a regular camera, multiple pixels take in the light from one source, like the sun, to create an image. Ghost images are basically the opposite: They start with multiple light sources in a predictable array, Faccio told Live Science, with the light being collected by a single-point detector, usually called a "bucket."

An easy way to envision how this works is to think about lidar, which uses a single-point laser to scan a scene. The detector captures how the light from the laser bounces back from each spot in the scene, which can then be reconstructed into an image.