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Trillion frames per second

Sun, 18th Dec 2011

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You may have tried slowing down a film you made of a mobile phone, eventually the playback become jerkey, because the camera only records about 15 or 30 images or frames a second, and there is no information about what is going on between the frames. Better cameras can takes more frames per second, Kitchen Science has various videos taken with a camera that can takeCamera up to 1000 frames per second, and others can take hundreds of thousands of frames per second. But Professor Ramesh Raskar at the media lab have created a camera that can produce a film at a trillion frames per second!

They have done it using a streak camera, which only looks at one line of the image at a time, which is projected onto a screen. This converts the light signal into a signal of free electrons. These are accelerated along a vacuum tube towards a detector at the other end of the tube. The beam of electrons is scanned across the detector very quickly, so as time passes they hit different parts of the sensor, and you end up with a 2D image which consists of how theline changes with time.

The camera isn't quite true 1 trillion frames per second as to build a proper video, you have to repeat the process for each line in the image, which limit
s its use, to things which exactly repeat again and again. Despite this the results are still increadable. They have illuminated various scenes using an extremely short pulse of light, and in their videos you can actually see the pulse of light moving at 300 000 km/s moving across a scene about 300mm across.



This is very pretty, but they have some more useful applications in mind, if they shine a very short pulse of light a scene where you can see an object and its reflection you see the reflection slightly after you see the object itself, which suddenly becomes very useful if you wanted to understand a scene whi
ch includes reflections of reflections, like you would see in you looked into a translucent object like many engineering devices or human flesh. So it may
be possible to reconstruct what is happening deep within your body using normal visible light.

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