Use laser on /off image to eliminate background image and detect distance. This program converted from python project here: https://github.com/chrisspen/laser-range-finder, in order to run real time at embeded Linux system, convert the code to C++ and opencv with multi-thread programming, the program can run on Raspberry 3 which has 4 1.2G ARM core with real time image processing at 15 HZ with 640X480 image resolution.