Characterization of the Microshell Surface Using Holographic Measurements

To characterize the shape, the quality, and the roughness of microshells, typically used technologies are scanning electron microscopy, scanning interferometric microscopy, or atomic force microscopy. One of the drawbacks of these techniques is that they are generally slow because of their scanning process. Digital holographic microscopy technology is an innovation that can offer ability adapted to these studies. It captures holograms instead of intensity images, as done by conventional microscopes. The holograms are then digitally interpreted (10 per second) to reconstruct a double image, one for the intensity and another one for the phase. Using a rotation axis, the bump counting for the complete microshell surface is possible with a very high speed. Using an image stitching software, mapping can be done in a few minutes. Wavelets such as "Mexican hat" are used to model the bumps. Each bump can then be characterized on the map by its position, diameter, and height.