Precise measurement of surface topography with microstructures based on differential confocal and spiral scanning

Abstract

This paper proposes a new topography measurement method combining laser differential confocal and spiral-scanning measurements together (TM-DCSS), which can realize large-area, fast and high-accuracy measurement of microstructure topography. Firstly, the mapping relationship between probe centering deviation and reconstructed topography distortion is analyzed, and a wedge rotation alignment method is proposed to make the probe precisely aligned with the rotating stage. Secondly, a sampling strategy of spiral trajectory is designed to eliminate the sawtooth distortion. Thirdly, a threshold-tunable wavelet denoising algorithm based on translation-invariant and particle swarm optimization is proposed in order to effectively eliminate the noise disturbance. Finally, an experimental platform based on TM-DCSS principle is constructed. The measurement results show that the centralization deviation of the proposed system is within 1.94 μm, and the maximum relative error is less than 0.78% when compared with the commercial microscope. The proposed method shows great potentials in various non-contact precision measurement applications.