Noncontact method of point-to-point absolute distance measurement using tandem low-coherence interferometry

We propose a novel absolute measurement method for precisely measuring the internal distance between two points, using a tandem low-coherence interferometer. In this method, a beam splitter is positioned between two plane mirrors, the locations of which are accurately determined at the nanometre level using tandem low-coherence interferometry. Using a He–Ne laser interferometer as a reference length standard, an internal distance of up to 100 mm was measured remotely, with a measurement uncertainty of 178 nm (k = 2).