Measurement of surface form of Johannesteijsmania altifrons leaf using phase-shift fringe projection

The design of thin-walled structures based on naturally occurring folded structures, such as the Johannesteijsmania altifrons leaf, is relatively unexplored. The main advantage of this particular type of folded leaf is that it is supported by a single main stem, which can be exploited in structural designs if the 3-D surface form is known. Since the leaf can deform if the surface form is measured using conventional contact methods, the non-contact phase-shifting fringe projection method was applied to determine the 3-D surface form of the leaf. The potential of the phase-shifting fringe projection method for reconstructing the 3-D surface of naturally occurring folded structures such as J. altifrons leaf has not been attempted in the past. The objective of this work is to investigate the potential of using this technique to measure the 3-D surface of the life folded leaf in its natural environment. Three fringe patterns were projected onto the leaf with phase-shifts of 0, 2π/3 and 4π/3, captured using a CCD camera and processed to obtain a phase map. The 3-D data of the leaf surface were successfully reconstructed from the phase map using a phase-unwrapping algorithm.