A coded-aperture based method allowing non-interferometric phase contrast imaging with incoherent X-ray sources

Abstract X-ray phase contrast imaging is a method whereby conventional X-ray absorption is replaced by refraction/interference effects taking place inside the imaged object. Approximately 15 years of experimentation, primarily carried out at synchrotron radiation facilities, has demonstrated that such an approach can solve the basic problem of conventional X-ray imaging, i.e., low image contrast due to small absorption differences. The impact that phase approaches could have on the most diverse fields of application of X-ray imaging (medicine, biology, non-destructive testing, etc. ) is therefore substantial. The problem so far has been that phase approaches have been restricted to synchrotron radiation facilities, the only notable exceptions being experiments based on microfocal sources. These however produce a low X-ray output, which translates into excessively long exposure times, practically preventing most real-world applications. Recently, interferometric X-ray phase contrast images have been obtained with extended sources by switching from Talbot to the Talbot/Lau configuration, i.e., adding an extra grating in contact with the source to increase its spatial coherence. This extra grating reduces the source output, and the set-up in itself presents some difficulties as multiple gratings with very small pitches have to be kept aligned and scanned during image acquisition. We present an alternative approach based on arrays of appropriately designed coded apertures carved into a thin absorbing mask. These apertures have a much larger (1–2 orders of magnitude) pitch than gratings used in Talbot interferometers making their handling, alignment, fabrication and scaling much easier. Only two masks are employed with no extra source mask required, which allows for a more efficient use of the radiation source and therefore for a reduction in the exposure time.