Phase-sensitive imaging techniques, suitable for investigating structures in the micron range, are discussed in this book with a focus on optical coherence tomography (OCT). The probed samples are mostly of technical nature, but the methods in general are not restricted to technical applications. Moreover, several imaging aspects, originating from biological applications, recently have been transferred to technical material sciences. OCT imaging is presented here mainly by its phase-sensitive modifications: polarization-sensitive OCT (PS-OCT) and differential phase contrast OCT (DPC-OCT). The comparison to quantitative imaging in phase contrast microscopy techniques has been drawn to illustrate the similarities, differences, and limitations of both techniques. The potential for appropriate image processing is demonstrated in this context to obtain improved quantitative and localized information about specimens and material behavior. The book connects the field of optics, mathematics, and image processing from an interdisciplinary point of view.