Optical fiber probe based on spherical coupling of light energy for inner-dimension measurement of microstructures with high aspect ratios

An optical fiber probe, based on spherical coupling of light energy, is proposed to transform the lateral displacement of a spherical coupler into the deflection of a light energy center, while the light energy is transmitted in the reverse direction. Therefore, the shadowing effect of a microcavity can be eliminated. The probe has a high displacement sensitivity, allowing precision inner-dimension measurements of microstructures with high aspect ratios. Measurements of microholes and fuel injection nozzles indicate that, for a microstructure with an aspect ratio of up to 15:1, a probing force <1 μN, a resolution of up to 0.05 μm can be achieved using the proposed probe, which is easy to exchange and low cost.