If you own a top-notch DSLR, your shutter might be as fast as 1/8,000 s. Some mirrorless cameras top out at 1/32,000 s. So, what do you do when you need to photograph action using a shutter speed 3,000 times faster than even those blazing mirrorless cameras? You use an entirely different kind of shutter.
At the dawn of the nuclear age, the technology to study the explosions had to evolve as quickly as that which produced them. One particularly tricky issue was photographing the bombs: scientists wanted to measure the temporal evolution of the diameter of the fireball, as this gave insight into the efficiency of the bombs. However, no camera with a traditional mechanical shutter could keep up with the incredibly rapidly expanding explosions; any image was overexposed and blurred beyond recognition. Enter MIT Professor of Electrical Engineering Doc Edgerton.
Edgerton invented the "rapatronic camera" (rapid action electronic camera), a device that did away with a mechanical shutter entirely. Instead, he took advantage of the polarization of light. If you're ever taken two pieces of linearly polarized glass and held them so their axes of polarization were perpendicular, you've probably noticed that no light passes through them. This is because the first filter blocks all light not parallel to its polarization axis, but then, the only light leftover is perpendicular to the polarization axis of the second filter, so it too is blocked. Edgerton came up with a clever scheme to take advantage of this: he sandwiched a Kerr cell between the two polarizers. A Kerr cell is a device that rotates light's plane of polarization when voltage is applied to it; in other words, one could create a very fast shutter simply by applying the correct voltage for the desired time — no moving parts to deal with. When a voltage was applied to it, the Kerr cell took all the light that passed through the first polarizer and rotated it to pass through the second filter, allowing for insanely fast shutter speeds of 10 nanoseconds. The results were eerie and stunning.
[via Damn Interesting]