Fiber probe for micro-hole measurement based on detection of returning light energy

In order to solve the problem of ultraprecision measurements of micro-holes with high aspect ratios, a tactile fiber probe based on the detection of the returning light energy center is proposed. With an incident fiber, a coupler, and an effluent fiber guiding the emission light, sufficient light energy can be provided for a photodetector, thus the shadowing effect of sidewall in a micro-hole can be eliminated. By converting the displacement of a probe tip to changes of the returning light energy center, measurement of the micro-holes with high aspect ratios can be realized. Experimental results indicate that the fiber probe has a spatial resolution of up to 0.04 mu m, a triggering repeatability better than 0.06 mu m, and a static state stability up to 0.41 mu m in 30 min. A micro-hole with a nominal diameter of Phi 200 mu m and thickness of 2 mm has been measured, the measurement result of diameter at a depth of 1 mm is 206.03 mu m, with a standard deviation of 0.067 mu m, and an aspect ratio of 5:1. (C) 2012 Elsevier B.V. All rights reserved.