Ultraprecise Three-Axis Visual Motion Tracking of Microscopic Objects

Abstract

Real-time image processing algorithms and associated mathematical formulas that render ultraprecise three-axis visual motion tracking are presented. The principle of three-axis motion tracking is based on lateral sampled white light interferometry (LSWLI) and real-time unbiased image registration. Two distinct regions of interest (ROIs), i.e., in-plane ROI and out-of-plane ROI, in a single 2-D image, taken at a single time instant, are processed in real time. Real-time continuous image registration (CIR) is realized and applied to 2-D shadow projection image content of the object to locate the object’s in-plane position, whereas adaptive 1-D CIR (A1-CIR) is proposed and applied to an LSWLI fringe pattern on the object to determine its out-of-plane position. Processing of images is synchronized with real-time image acquisition to realize three-axis motion tracking. Computer simulations are used to demonstrate bias caused by image registration and to examine its effect on measurement precision. The ability of the proposed approach to eliminate measurement bias is validated. Experimental results are presented and used to examine measurement resolution for positioning and to illustrate measurement precision for long-range motion tracking.