X-ray phase-contrast imaging is extremely powerful for visualizing internal structures with low-Z matrices, which are most likely in bio-medical specimens. The use of an X-ray interferometer is one of the most promising ways forward for this imaging technology, but resolution has been limited to the micrometer scale so far. A research group led by Dr. A. Snigirev (European Synchrotron Radiation Facility, Grenoble, France) has recently developed a novel type of X-ray interferometer employing a bilens system with two parallel arrays of compound refractive lenses, each of which creates a diffraction limited beam under coherent illumination. The energy of the X-rays is 10-20 keV and the material used in the refractive lenses is silicon. When the two beams overlap, they produce an interference pattern with fringe spacing ranging from tens of nanometers to tens of micrometers. Readers may notice that the system is similar to the model of a Billet split lens in classical optics (See Fig.7.8, page 263 in "Principle of Optics", M. Born and E. Wolf, 6th Ed, Pergamon Press (1988)). The use of a modern synchrotron source and this novel optical device thus opens up a new field and could revive old theorems. Coherent moiré imaging or radiography are promising straightforward applications. For more information, see the paper, "X-Ray Nanointerferometer Based on Si Refractive Bilenses", A. Snigirev et al., Phys. Rev. Lett., 103, 064801 (2009).
