492K views · Dec 10, 2018 · 27:46 · 1 HN recommender · 3 mentions · discussed 2019–2025
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.
Why Hacker News points people here: 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”HN comment, 2024
“a pretty cool video where he demonstrates how a single laser diode can be used to measure miniscule vibrations”
A single laser diode measuring miniscule vibrations
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
“The idea for hacking on these things comes from Ben Krasnow”
Source of the idea for hacking laser self-mixing sensing
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.
“This guy gets close”
Near-example of cheap sub-micron laser measurement
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?
