The imaging solution produces a frame every two trillionths of a second, and the result shows the movement of light at roughly half a trillion frames per second. (Image credit: MIT)
Light travels at 186,000 miles per second, 671,000,000 miles per hour or 173 astronomical units per day. It's theoretically as fast as energy or matter can travel through space, and scientists at MIT have managed to capture light as it travels using a novel imaging system that uses a technique known as Femto-Photography. The technique uses femtosecond lasers to produce brief pulses of light that last one quadrillionth of a second, like taking a super-speed snapshot of something traveling faster than we can see with the naked eye.
To that end, the scientists didn't take a few million snapshots of a laser bouncing back from a target; they took trillions of them, or instead, they used over 500 camera sensors, mirrors, and streak tubes to document the laser's movement through objects and liquids. The imaging system works by using femtosecond lasers to fire a pulse of light at a specific target. When that pulse hits, some of the light scatters, which is picked up by those sensors, capturing the image in a femtosecond timeframe. The data collected by the sensors is then spliced together to reconstruct an image of that scene.
The scientists explain, "Our light source is a Titanium Sapphire laser that emits pulses at regular intervals every ~13 nanoseconds. These pulses illuminate the scene and also trigger our picosecond accurate streak tube, which captures the light returned from the scene. The streak camera has a reasonable field of view in a horizontal direction but is very narrow (roughly equivalent to one scan line) in vertical dimension. At every recording, we can only record a '1D movie' of this narrow field of view. In the movie, we record roughly 480 frames, and each frame has a roughly 1.71 picosecond exposure time."
To capture video, a series of mirrors were used to orient the view of the camera to different parts of the object as the light hits. An algorithm is then used to produce a single 2D movie using spliced images comprised of 480 frames, each with a 1.71 picosecond exposure time. The scientists state that their imaging system has potential outside capturing light as it travels, including applications in artistic and educational visualization, medical imaging to reconstruct surface elements and analyzing faults and material properties.
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