© Nature Photonics
The letter A with no scattering (top), behind scattering plastic (centre) and re-imaged with the new technique
A camera that can see through skin and even frosted glass has been revealed. The scientists behind the breakthrough say their research could even lead to cameras with the ability to see around corners. The Israel team have found a novel trick to make their camera work. Reported in Nature Photonics
, it uses natural light rather than lasers.
The technique uses what is called a spatial light modulator to 'undo' the scattering that makes objects opaque or non-reflecting.
'If you want to look to see an embryo developing inside an egg but the eggshell scatters everything, or you want to look through the skin, scattering is the main enemy there, and time-of-flight is not a good solution,' said Professor Yaron Silberberg of the Weizmann Institute of Science in Israel, who led the research.
His solution uses a phenomenon known as spatial light modulators (SLMs).
SLMs modify what is known as the phase of an incoming light beam. They can corrected the 'scattering' of light caused when it hits as object such as skin of frosted glass.
They are made up of an array of pixels that can correct for this by selectively slowing down some parts of the beam and allowing others to pass untouched - when an electric field is applied to a pixel, it changes the speed at which light passes through it.
'Our results bring wavefront-shaping closer to practical applications and realize the vision of looking through walls and around corners,' the researchers said.
Professor Silberberg and his team 'trained' by shining light from a normal lamp through a highly scattering plastic film and allowing a computer to tune the image until they could see the lamp clearly.
'What we have shown is that you don't need lasers - everybody else was doing this with lasers, and we showed you can do it with incoherent light from a lamp or the Sun - natural light,' Prof Silberberg told BBC News.
But the team then realised that the same approach can work in reflection - such as bouncing light off a wall at a corner.
They then showed the procedure works just as well when the light from an object bounces off a piece of paper; the SLM could "learn" how to undo the paper's scattering effect, making it a nearly perfect reflector.
'You can take a piece of wall and effectively turn it into a mirror, and this is the part that makes everybody raise an eyebrow,' said Professor Silberberg.
The technique is likely to be first used for medical scanning.
A camera that can "see around corners" garnered much attention in 2010, using a series of timed laser pulses to illuminate a scene and working out what is around a corner from the timing of the reflections.