A laser pointer at 2B FPS [video]

Tl:dw for how this works:

He scans one line at a time with a mirror into a photomultiplier tube which can detect single photon events. This is captured continually at 2MSample/s (2 billion times per second: 2B FPS) with an oscilloscope and a clever hack.

The laser is actually pulsing at 30KHz, and the oscilloscope capture is synchronized to the laser pulse.

So we consider each 30KHz pulse a single event in a single pixel (even though the mirror is rotating continuously). So he runs the experiment 30,000 times per second, each one recording a single pixel at 2B FPS for a few microseconds. Each pixel-sized video is then tiled into a cohesive image

Good explanation. One detail though: it is one pixel at a time, not one line at a time. Basically does the whole sequence for one pixel, adjusts mirror to next one, and does it again. The explanation is around the 8 minutes mark.

Just want to make it clear that in any one instant, only one pixel is being recorded. The mirror moves continuously across a horizontal sweep and a certain arc of the mirror's sweep is localized to a pixel in the video encoding sequence. A new laser pulse is triggered when one pixel of arc has been swept, recording a whole new complete mirror bounce sequence for each pixel sequentially. He has an additional video explaining the timing / triggering / synchronization circuit in more depth: https://youtu.be/WLJuC0q84IQ

And the reason it matters that this is a single pixel at two billion times per second is that we can hypothetically stack many of these assemblies on top of each other and get video of a single event that is not repeatable.