Improved chromatic confocal displacement-sensor based on a spatial-bandpass-filter and an X-shaped fiber-coupler Bai, Jiao ; Li, Xinghui ; Zhou, Qian ; Ni, Kai ; Wang, Xiaohao Abstract Publication: Optics Express Pub Date: April 2019 DOI: 10.1364/OE.27.010961 Bibcode: 2019OExpr..2710961B