This Innovative Camera System Seemingly Freezes Rotation in Real Time

Excessive Overkill designed a camera system that seemingly freezes quickly moving parts in mid-air during video capture, allowing you to observe a spinning fan blade hanging motionless in mid-air. Put simply, that’s stroboscopy applied to video, a technique for examining moving objects by flashing a light at the appropriate time. However, this technique has now been enhanced so that it can handle entire video sequences.

Stroboscopy is a relatively old technique for observing moving objects that includes flashing a light at precisely the appropriate moment. To make it work, Overkill used a variety of hardware and custom circuitry. He used an industrial camera with a global shutter, which most conventional cameras struggle with because they only expose the sensor in bits. However, a global shutter exposes the entire scene at once, which is really useful. The light source came next, with Overkill designing and building a high power LED strobe board, which is essentially a highly strong flash of light compressed into a very brief burst. This is powered by 24 volts and can detect a signal to flash in sync with the camera, with some safety circuits to prevent the LEDs from being out of control.

Getting the timing right is critical, so Overkill employed a laser sensor to detect the rotating object each time it spun around, then sent a signal to the strobe and camera to ensure that each frame was caught at the same moment. This is critical since the object may move quicker in some locations than others, and the timing must be perfect.

Overkill had some difficulties along the way, so it wasn’t all smooth sailing. For starters, those really rapid flashes don’t provide much light, so he ended up utilizing some extremely powerful LEDs to compensate. Then he encountered a difficulty with the laser sensor taking up stray light from the strobe, which was resolved by adding a high frequency modulation to the strobe output to balance things out. Finally, he built some Python code to control everything, so if you want to attempt and recreate the system, the design files for the PCB and mechanical parts are available on GitHub.