Design of Three-dimensional Isotropic Microprobe Based on Three-Flexible-Hinge Suspension for Measurement of Microstructures

To enhance the precision manufacturing of microstructures, a 3-D isotropic microprobe based on three-flexible-hinge suspension and orthogonal microball collimation was developed. First, the sensing principle of the microprobe was investigated by analyzing its displacement transfer principle and the displacement measurement principle of the orthogonal microball collimation optical paths. Second, the stiffness model of the microprobe at the tip was established by considering the influence of the measuring stylus stiffness. Subsequently, the isotropic design of the microprobe was developed in terms of the 3-D isotropic stiffness and sensitivity. Utilizing the rotation and translation of the three-flexible-hinge suspension, the 3-D tip displacements were transformed into the 3-D displacements of the microball of the transfer stylus which was fixed in the reverse coaxial direction to the measuring stylus, then the 3-D displacements of the microball were transformed into centroid position shifts of the light spots by the orthogonal microball collimation optical paths. Finally, a 3-D isotropic microprobe was fabricated, and experiments to verify its performance for measurements pertaining to microholes and microsteps were conducted. A method for the effective measurement of microholes was established, which could improve the measurement efficiency, and the tilt angle of the countertop was considered for the measurement of the microsteps. The experimental results indicated that the proposed microprobe could help realize low measurement force, 3-D isotropic measurement of microstructures, and improvement of the measurement accuracy.