Real-time noncontacting distance measurement systems are constructed using photogrammetric principles. The system is used to measure a distance between two points specified by sharp visible contrast change under optical illumination. Tests of the system indicate that it can measure the distance with a repeatability of better than one part in 104.
T. Sawatari, "Real-time noncontacting distance measurement using optical triangulation," Appl. Opt. 15, 2821-2824 (1976)