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edfas.org ELECTRONIC DEVICE FAILURE ANALYSIS | VOLUME 22 NO. 3 20 refractive indices and is particularly useful for low-absorb- ingmaterials such as polymer blends or organicmultilay- ers. Dark field (scattering) contrast on the other hand is particularly sensitive to features such as micro-cracks or voids that are sub-micron in size, delamination, porous interfaces, and sub-resolution morphological features. Through the acquisition of multiple radiographs during each sample rotation, 3D tomography for all three contrast mechanisms can also be obtained, but with simultaneous acquisition of images containing all three contrastmecha- nisms, this step may be unnecessary for many samples. Until now, such tri-contrast imaging has not been widely available because implementation of such features limits the field of view and throughput. One major problem has been the requirement of a G 0 grating, also known as a source grating. This grating is required to provide a structured beamwith sufficient spatial coherence for the interferometer to work (see Fig. 3). To overcome the low throughput and limited field of view issues, a new patented x-ray source in which microstructures of targetmaterials are embedded in a diamond substrate in the pattern of the G 0 gratingwas designed. In this way, a G 0 grating coupled to a conventional extended x-ray source is no longer needed. Moreover, the x-ray flux reaching the detector will be orders of mag- nitude higher, making this technique practi- cal for commercial applications. In a Talbot Fig. 2 Talbot interferometry of shower hose showing three radiographs with different contrast mechanisms acquired simultaneously—absorption, phase, and scattering/dark field contrast. Phase contrast shows the sharp boundary of the polymer-air interface while in dark field, the fine threads that reinforce the polymer are apparent. Courtesy of Prof. Momose, Tohoku Univ., Japan. Fig. 3 Grating-based Talbot-Lau interferometry uses three gratings [3,4] . The source grating (G 0 ) and modulation grating (G 1 ) create interference fringes, which are then sampled by an analyzer grating (G 2 ) placed before the detector. Fringe profiles will change because of absorption (red), phase shifts (blue), and scattering (green). (a) (b)