Physicists hack the human visual system to create “ghost images”

Desk Report: Ghost imaging is one of the more extraordinary advances in optics in recent years. It produces high-resolution images using single-pixel cameras and light that has never interacted with the object in question.
The technique relies on clever algorithms to crunch the seemingly random data that a single pixel appears to gather. More on that below.Because of this, it’s easy to imagine that ghost imaging has little relevance for human perception, since the human visual system must be incapable of processing this kind of data.
Not so. Today, Alessandro Boccolini at Heriot-Watt University in Edinburgh, Scotland, and a couple of colleagues demonstrate that humans can see ghost images and suggest how the technique can be used to study and exploit the visual system in entirely new ways.
First some background. Ghost imaging works by projecting a random pattern of light onto an object and recording the reflected light with a single pixel. Repeating this process with differnet random patterns of light produces a sequence of data points about how the light intensity varies over time.It’s easy to think these data points must vary at random. But they are actually correlated, because the light reflects off the same object. So crunching the data in the right kind of way can reveal this correlation: an image of the object.Not all this processing need be done in a computer. One shortcut is to use the signal from the single pixel to modulate the light output from another LED. This is then projected onto the same random pattern, and the process repeated for the next pattern, and so on.
The image of the object—the ghost image—can then be reconstructed by integrating the reflected light from a long sequence of random patterns illuminated. Interestingly, the resulting image is formed from light that has never interacted with the original object.