A Twin Fiber Bragg Grating Probe for the Dimensional Measurement of Microholes

A fiber probe with a novel structure of twin fiber Bragg grating sensitive to both contacts along x-axis and z-axis is proposed for measurement of microholes with high aspect ratio. The main conundrums during the dimensional measurement of microholes with high aspect ratio, such as shadowing effect, limited probing space, and requirement of multidimensional tactile sense are well solved using the proposed probe. Sensing principle and decoupling algorithm has been verified through experiments. Experimental results indicate that the influence of manufacture defects and the misalignment between probe and measurement coordinates can be reduced through rotation and tilt calibration. The contact displacement sensitivity is 12.91 pm/μm and 49.75 pm/μm along x-axis and z-axis, respectively. A microhole with an aspect ratio of 10:1 can be measured using the proposed twin fiber Bragg grating probe.