Long depth-range measurement for fringe projection photogrammetry using calibration method with two reference planes

Abstract

Using a calibration method with two reference planes, this study proposes a simple method to extend a measurement range in an optical direction for a fringe projection technique. The proposed method only inserts a baseline to the conventional fringe pattern projected onto an object surface and computes an exact phase alignment in the extended area concerning the baseline. The correction coefficient for the fundamental equation calculating 3D position coordinates of the object surface is developed to prevent accuracy degradation caused by extending the measurement range. Regardless of the extension of the measurement range, the accuracy verification test demonstrates that the proposed fringe projection method provides a measurement result with the same accuracy as the conventional method. Furthermore, through the surface shape measurement of the stationary parabola antenna reflector having a diameter of 1.5 m, a pendulum motion of the flat plate with a large amplitude, and a complicated deployment behavior of the flexible membrane structure, effectiveness and applicability of the proposed method for actual structures are demonstrated. This study offers a fringe projection photogrammetry applicable to capture dynamic responses of the object surface with a large amplitude and the large-sized stationary object surface with high spatial resolution.