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 μm, a triggering repeatability better than 0.06 μm, and a static state stability up to 0.41 μm in 30 min. A micro-hole with a nominal diameter of Φ200 μm and thickness of 2 mm has been measured, the measurement result of diameter at a depth of 1 mm is 206.03 μm, with a standard deviation of 0.067 μm, and an aspect ratio of 5:1.

► The spatial resolution of the probe is up to 0.04 μm.
► The triggering repeatability of the probe is better than 0.06 μm.
► The probe has a static stability up to 0.41 μm in 30 min.
► A measurement result with a standard deviation of 0.067 μm has been achieved.
► Several probes with coupler diameter from 70 μm to 300 μm have been fabricated.