Axial nano-displacement measurement with high resolution and wide range based on asymmetrical illumination.

We propose a novel axial nano-displacement measuring approach. Based on asymmetrical illumination, the axial drifts of the sample plane can be measured by detecting the position of the centroid of the focal spot. Both CCD and QD are used as the detector in the system and two data processing models are designed. With a relatively simple and applicable configuration, the proposed system can realize a wide measuring range of >4λand a high axial resolution of 2nm. Moreover, the presented approach is immune to the influence caused by the energy fluctuation of the laser source. Possessing these advantages, this measuring method has big potential to be applied in modern engineering and scientific researches.