As Ramesh Raskar introduced his recent TED talk (see below), he did so with one of the most famous photographs of the modern era. His backdrop was Harold Edgertonʼs seemingly impossible image of a bullet piercing an apple. A photograph as awe-inspiring today as it was in 1964. However, Raskar fancied his chances at going even further with his photography. He reckoned that he could shorten Edgerton’s exposure time of just a few nanoseconds, and produce a camera that could capture up to 1 trillion frames per seconds. Needless to say he succeeded. Femto-photography was born.
To offer a little perspective: a bullet, such as Edgerton’s, travels at approximately 850 metres per second, whereas a ʻlight bulletʼ, created by emitting a pulse of light energy from a sharply-aimed laser, travels at around 300 million metres per second. Raskarʼs camera works at such a phenomenal rate that he could actually photograph light itself. This was demonstrated with an incredible stop motion video of a light bullet being shot through a Coca-cola bottle. He and his team had managed to photograph the light at such a rapid rate, that the awestruck audience were able to see how light disperses as it hits objects in its path.
On the surface, this research may seem a little unnecessary. We can appreciate the feat, but is there really any practical application of such work? Actually, yes. Seeing light in such a manner for the first time has opened many avenues of exploration with regards to the behaviour of photons, the elementary particles of light. As a light pulse hits an object, photons scatter in what has been poetically dubbed ʻechoes of lightʼ. These photons hit other near-by objects, such as those, which may be “hidden” around a corner. The photons then return to the camera at different times. Given the incredible time resolution of only two picoseconds, the distance of the objects from the camera can be calculated with sub millimeter accuracy.
Essentially Raskar and his team’s new technology could allow for the development of cameras, which can look around corners. This is simply one mind-blowing opportunity in a sea of possibilities for the use of such technology. Not content with what they’ve already achieved, Raskar’s team are now using this technology to develop a new generation of CAT-scan machines, which, if successful, could eventually do away with the need for invasive X-ray imaging techniques in health care. Truly work to be applauded.