Hacker News new | ask | show | jobs
by abthomson 4702 days ago
For shorter distances, time-of-flight is not typically used. There's surprisingly little documentation about how these things work online though.

From http://ptd.leica-geosystems.com/en/Measuring-Techniques_4939...

"The laser diode emits light pulses with a defined wavelength and pulse repetition frequency. Due to the runtime difference between the internal reference path and the external measurement path, the light pulses, reflected on a target and received from the Leica DISTOâ„¢, have experienced a phase shift in relation to the light pulses received through the internal reference path. That phase difference between those two signals is proportional to the distance between instrument and target."