A research team from the University of Singapore has developed a device that can make objects invisible by bathing them in a beam of darkness.
The system takes the conventional approach to optics -- which generally aims to make images as sharp and clear as possible -- and turns it completely on its head. Usually imaging systems focus light into a pattern known as a point spreading function, which consists of a spiked central region of high intensity (the main lobe) surrounded by a concentric region of lower intensity light and a higher intensity lobe after this. In order to achieve the best resolution, the central region should be narrowed and intensified, while the outer lobe is supressed. This makes sure that the image is very bright and sharp with well-defined edges.
The researchers' beam can hide macroscopic objects by taking the opposite approach: intensifying the outer lobes suppressing the central region. This means that the central region has a field intensity of light that is pretty much zero. They did this using special lenses that could smear out the central spike while increasing the intensity of the concentric lobes. Objects in this 3D region cannot be resolved and so are hidden from sight. The effect has been named "anti-resolution".
The research team managed to hide a three-dimensional object (the letter N) that was 40-micrometers in size from a single frequency of light (red laser light). "This new scheme of manoeuvring light creates a plethora of possibilities for optical imaging systems, superb surveillance by seeing things behind for the military use, or cloaking the object surrounded by high field intensity," explains lead author Chao Wan, from the Department of Electrical and Computer Engineering at the National University of Singapore.
The technology could one day pave the way for a sort of "invisibility gun" that could be aimed at an object. In order to do this, the researchers would have to extend the effect to the wider spectrum of light.
You can read the full study online.