Quantitative Near Field Imaging with Multi-Detector Waveguide

Near field imaging with open ended waveguides has found increasing interest [1–3]. The basic idea is to scan across samples with a waveguide transducer as a reflection near field probe in order to characterize material properties and image defects that are much smaller than the wavelength. The reflection will form in the waveguide a standing wave where amplitude and phase depend on local intensity and phase of reflection. These effects can be demonstrated with slotted line measurements of the standing wave pattern. For example the investigations in figure 1 show the standing wave patterns for homogenous material and for a hidden hole. Depending on the material properties there is a change in phase and magnitude of the standing wave.