My new range finder says that it works but bouncing a laser off the target and seeing how long it takes to return. Using round numbers, a laser should travel about 330,000,000 yards per second. How can any device under $100 accurately measure the time it takes for a laser to travel 5 yards? What manner of witchcraft is this?
Light travels at 11.8028527 inches per nanosecond. To measure distance with a resolution of around 1 inch requires 100pS timing.
Turns out, there’s a chip that does just that: http://www.lightware.co.za/download/doc/DS00VQ100%20-%20Laser%20Range%20Finder%20controller%20data%20sheet_Rev_01.pdf
It uses “down conversion” (mixing two high frequencies to obtain a third, lower, frequency) to be able to time the laser pulse round-trip with pretty good accuracy.
Fascinating. Thanks for the link beowulff. It still amazes me that it can be done so cheaply.