Low coherence interferometry-based meter-distance range finder

Abstract

White light interferometry, also known as low-coherence interferometry, is a mature technique used in metrology to measure 3D surface morphology at sub-micrometric scale. This technique is used in many fields of applications, such as optical qualification tests, surface metrology, medicine and others. We present here a new set-up able to measure the distance of an object with sub-micrometric accuracy and a depth of field (depth range) of some millimeters. The instrument is useful to measure thermo-mechanical deformations as well as longitudinal optical alignments. The set-up does not present any moving part inside and then it may be fruitfully exploited, avoiding a possible point of failure, for space instrumentation. It may be useful, for example, to measure mechanical mounting or truss deformations or to control in-situ optical alignment.