One- and two-dimensional, differential, reflective fiber displacement sensors.

A family of differentially connected, multimode fiber reflectometers is described, which detects absolute position of a specularly or diffusely reflecting linear or point target. Low noise-equivalent displacement (0.026 nm/square root(Hz)) and bipolar output make this sensor type ideal for use with feedback controlled mechanical stages with submicron precision. Several algorithms for estimating the location of the target point from reflected intensities are investigated and compared through high-resolution error surface plotting.