News on Nature tells of intriguing photographic technique - not that it's at all remotely useful for paparazzi and otehrs wishing to take shots of objects that are around corners but not in direct view. Includes:
They fire a pulse of laser light at a wall on the far side of the hidden scene, and record the time at which the scattered light reaches a camera. Photons bounce off the wall onto the hidden object and back to the wall, scattering each time, before a small fraction eventually reaches the camera, each at a slightly different time. It's this time resolution that provides the key to revealing the hidden geometry. The position of the 50-femtosecond (that’s 50 quadrillionths of a second) laser pulse is also changed 60 times, to gain multiple perspectives on the hidden scene.
Whereas photons that have hit different parts of the hidden scene from one laser position may be the same, they will have a different total distance for another laser spot. "The overall mathematical technique," explains Raskar, "is similar to the computational tomography that is used in X-ray CAT-scans."
At present, the whole process takes several minutes, but researchers hope that in the future, it will be reduced to less than 10 seconds.