Micron-Accurate Laser Fresnel-Diffraction Ranging System

The figure schematically depicts two versions of an opto-electronic system, undergoing development at the time of reporting the information for this article, that is expected to be capable of measuring a distance between 2 and 10 m with an error of no more than 1 μm. The system would be designed to exploit Fresnel diffraction of a laser beam. In particular, it would be designed to take advantage of the fact that a Fresnel diffraction pattern is ultrasensitive to distance.