Laser rangefinders don't switch the light source at 10GHz. They "chop" the laser on-off at (say) 10kHz. The measure the difference between the reference (onbo

Laser rangefinders don't switch the light source at 10GHz. They "chop" the laser on-off at (say) 10kHz. The measure the difference between the reference (onboard) and the return using (typically) a PLL that can measure time differences down to picoseconds (these are usually used in high-frequency RF equipment). Using a microcontroller counter would be too slow. Cheaper LRF's can use triangulation with a known baseline. That's how Neato robotic managed their $10 spinning version for the vacuum: http://www.hizook.com/blog/2009/12/20/ultra-low-cost-laser-rangefinders-actualized-neato-robotics http://www.hizook.com/blog/2009/12/20/ultra-low-cost-laser-r... To wit... I like to disassemble laser rangefinders! http://www.hizook.com/blog/2009/01/04/velodyne-hdl-64e-laser-rangefinder-lidar-pseudo-disassembled http://www.hizook.com/blog/2009/01/04/velodyne-hdl-64e-laser... http://www.hizook.com/blog/2009/02/14/omron-sti-optoshield-os3100-laser-rangefinder-lidar-disassembled http://www.hizook.com/blog/2009/02/14/omron-sti-optoshield-o... http://www.hizook.com/blog/2008/12/15/sick-laser-rangefinder-lidar-disassembled http://www.hizook.com/blog/2008/12/15/sick-laser-rangefinder...