Characterization of creases in polymers for adaptive origami engineering
In this work digital holography is utilized to perform three dimensional tomographic and topographic measurements. Digital holography is combined with multiple projection tomography to solve the ill-posed problem of three dimensional object reconstruction with high axial accuracy. Reconstruction methods based upon both traditional and compressive sensing methodologies are applied to tomographic reconstruction, including three dimensional reconstructions utilizing digital holographic microscopy. Various multiple-projection recording architectures are explored, including multiple-projection/single-exposure and multiple-projection/multiple-exposure methods. Additionally, multi-wavelength digital holography is applied to calculate the three dimensional surface profile and volume displacement of various topographic features. To accurately measure the volume displacement of macroscopic features, long synthetic wavelengths up to several millimeters are employed, while nano-scale features are measured using very short synthetic wavelengths combined with digital holographic microscopy. Practical methods of implementation are considered, including both multiple-exposure and single-exposure/spatial heterodyne techniques and an analysis of geometric effects due to both Michelson and Mach-Zehnder recording configurations.