Trillion Frames Per Second Shutter Speed
A team from the MIT media lab has created a camera with a “shutter speed” of one trillion exposures per second, enabling it to record light itself traveling from one point to another.
The project began as an effort to see around corners. Ramesh Raskar, an associate professor of media arts and sciences at the Media Lab, said he wanted to do this by capturing reflected light and then computing the paths of the returning light, thereby building images coming from rooms that would otherwise not be directly visible.
From the project web site.
The new technique, which we call Femto Photography, consists of femtosecond laser illumination, picosecond-accurate detectors and mathematical reconstruction techniques. 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 horizontal direction but 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. Through a system of mirrors, we orient the view of the camera towards different parts of the object and capture a movie for each view. We maintain a fixed delay between the laser pulse and our movie starttime. Finally, our algorithm uses this captured data to compose a single 2D movie of roughly 480 frames each with an effective exposure time of 1.71 picoseconds.
Even though the camera itself is bulky and takes a long time to process the frames, Dr. Raskar says the technology has a variety of interesting commercial applications. One of his graduate students, Jaewon Kim, published a thesis last year envisioning portable CAT-scanning devices.
(source)
