Laser diode self-mixing: Range-finding and sub-micron vibration measurement on HackerTube: recommended by 1 Hacker News commenter across 1 month, 2019–2025.
demo · intermediate · evergreen
Ben Krasnow of Applied Science shows that a plain laser diode can measure sub-micron vibrations from centimeters away using self-mixing interferometry, and can also be used for range-finding.
HN points to it as a cool demonstration of cheap precision laser measurement and the origin of hacks based on self-mixing.
“a pretty cool video where he demonstrates how a single laser diode can be used to measure miniscule vibrations”
3 Hacker News comments link this video. Each one links back to its thread.
Related to this Applied Science on YouTube has a pretty cool video where he demonstrates how a single laser diode can be used to measure miniscule vibrations. I wonder if this would be sufficient for a laser microphone? ▶ this video
in “Open source laser microphone picks up laptop keystrokes” · View on HN
Slightly offtopic, why is it so difficult to find a cheap and compact laser interferometer that can do sub-micron measurements? This guy gets close: ▶ this video But why isn't something cheap and small like this commercially available as an integrated system?
in “Lidar, optical distance and time of flight sensors” · View on HN
There is a cool effect where a laser reflecting back into itself will cause interference inside the laser diode and affect the power required to drive it in a measurable way and with it you can extract a surprising amount of information (distance, rotation, angle, speed, etc.) I was ... hasty ... with my first laser diode and burned it out in about 30 seconds. I like to tell myself the money wasted was spent on learning lessons. The second is coming in the mail. The upshot with this method is that it can be extremely low cost and give you access to write code that interfaces directly with physics instead of somebody else's device. The idea for hacking on these things comes from Ben Krasnow ▶ this video and several research papers.
in “Kern Microtechnik: Accurate CNC Machines [video]” · View on HN