Nano position sensing based on laser trapping technique for flat surfaces

The main purpose of this study is to develop a nano-CMM (coordinate measuring machine) that can measure three-dimensional shapes of a micro component. An improved probe is the key for achieving the nano-CMM. Subsequently, we propose a laser trapping probe, which is an optically controlled glass micro-sphere based on the laser trapping technique. In the coordinate measurement of a flat surface using the laser trapping probe, the measurement uncertainty is increased due to the influence of a standing wave. In this paper, the position sensing properties and accuracy of the laser trapping probe along the direction of the laser axis are experimentally investigated for measuring flat surfaces with low uncertainty. The influence of the standing wave results in a positional fluctuation and resonance frequency shift of the probe. However, this positional fluctuation of the probe is highly repeatable. It is found that the laser trapping probe can sense the specimen surface by adjusting to an appropriate oscillation frequency. Consequently, the laser trapping probe could determine a surface position with a repeatability of 64 nm.