NONCONTACT SINGLE-FIBER-OPTIC PROXIMITY SENSOR USING A LASER-FABRICATED TAP

We have developed a simple, noncontact, fiber-optic proximity sensor, using a laser micromachined tap on a single multimode optical fiber. T he fiber end is placed near a target surface, and a beam of light is i ncident from the fiber onto the target. Some fraction of this light is reflected or scattered by the target and coupled back into the fiber. The amount recoupled into the fiber is dependent on the distance betw een the fiber end and the target surface as well as on other parameter s such as the target's surface roughness. The fiber-optic tap allows u s to monitor both the initial amount of light launched down the fiber toward the target and the amount of backreflected light from the targe t. For a known environment and target surface, variations in source in tensity can be compensated for by monitoring the ratio of the two coun terpropagating beams. (C) 1997 Optical Society of America.