Light Flashes With Rapid Eye Movement

Visualizing tutorial at the speed of light one trillion frames per second

We have built a virtual, slowmotion camera, where we can see photons, or light particles, moving through space. Now you have seen Doc Edgerton's pictures of a bullet through an apple. But photons travel about a million times faster than bullets. So our camera can see these photons, or bullets of light, traveling through space. We use a very regular pulsed light source

and a camera, that is not one camera, but an array of five hundred sensors, each triggered at a trillionthofa seconddelay. So, even though each of our sensors is slow, we can still capture fast movie. I'm standing next to our laboratory setup here. This is our camera, objectives in the front here. The body of the camera is much larger than what

you would expect from a regular camera, like the one over here. Our light source is a titaniumsapphire laser that's over here, and emits a beam of very, very short pulses, and those pulses are then directed to the seam pause with these mirrors. Now, our camera only sees one dimension so it makes a fast movie, but it makes a fast movie

of one line of the scene only And in order to fix that, we have these two mirrors here. We look at the scene via these two mirrors, and when we rotate this upper mirror here we actually see different lines of the scene. So, what's happening is, the camera keeps taking images and we very slowly rotate this mirror to scan our field of view across the entire scene.

And because all of our pulses look the same, we can, in the end, go and combine all of these images that we took to get one complete movie of the scene. Such a camera may be useful in medical imaging in industrial or scientific use, and in the future even for consumer photography. In medical imaging, now we can do ultrasound with

light, because we can analyze how light will scatter onedimentionally inside the body. In industrial imaging, one can use the scattered light to analyze defects in materials. And in consumer photography, we are always fascinated with creating lighting effects that appear to come from very sophisticated light sources. But, because we can watch photons seemingly

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