Endoscopic displacement measurement based on fiber optic bundles

Abstract

In-line monitoring and routine inspection are essential for using and maintaining complex equipment. The simultaneous implementation of visual positioning and displacement measurement allows the accurate acquisition of characteristics, including object dimensions and mechanical vibrations, while rapidly locking the target position. However, the internal structure of equipment is frequently obscured, making direct visual inspection challenging; therefore, flexible and bendable fiber optic–based endoscopes are extremely valuable in harsh conditions. This study enables all-fiber visual displacement measurement using a single-mode fiber and an imaging fiber bundle. Based on optical triangulation and spot centers extraction method from fiber bundle images, 0.07 mm precision at a measurement distance of 40.12 mm is achieved vertically for rough objects. We demonstrate its surface reconstruction and vibration measurement functions. Factors that affect measurement accuracy, such as light source and object roughness, are also discussed.