Autofocus methods for 3D shape measurement with digital fringe projection techniques

摘要

This paper presents two autofocusing methods for 3D shape measurement. We tried two systems: 1) for a single camera and dual projector system, we only used two projectors for 3D reconstruction, and thus camera calibration is not necessary; 2) for a single camera and single projector system. Because the projector depth of field is large for high-quality fringe pattern generation for 3D shape measurement, we attached an electrically tunable lens (ETL) to the camera. For the first system, we determined the focal plane from the rough measurement with an initial input signal to ETL, and 3D reconstruction was realized through the matching points on two projectors. For the second system, we modeled camera parameters as continuous function of the input signal to ETL that is pre-calibrated; and implemented a traditional passive autofocusing algorithm. Experimental results demonstrated the success for both methods to potentially achieve autofocusing capability for 3D shape measurement systems.