Scientists from the Cornell University, the University of Rochester and the Argonne and Brookhaven national laboratories have described that wavefront aberrations generated by defective hard X-ray optics can be measured by phase retrieval methods.
In the report titled “Measurement of hard x-ray lens wavefront aberrations using phase retrieval”, the scientists showed a precise technique that can guide in enhancing the development process for future optics through quantitative feedback and optimal positioning of current optics.
Experimental setup to measure aberrations using the new phase retrieval method
Accurate measurement of wavefront is essential for determining the alignment, overall performance and quality of surfaces of complex imaging systems. It offers a quantitative map of the aberrations incurred due to misalignments or manufacturing errors in an imaging system. Current method does not provide direct data about the aberrations and is time-consuming. In the new phase retrieval method called transverse translational diversity (TTD), the resulting data provides a clearer picture of the ambiguities. It helps in measuring the aberrations of the x-ray optics and has been utilized successfully in x-ray imaging applications. A computer algorithm can be used to process the measured data to obtain an x-ray of the wavefront aberrations.
In order to test the new technique, an aberration was introduced by the researchers by turning a one-dimensional optical kinoform X-ray from its favorable position. Accurate and fast prediction of the aberration caused by the rotation provided the scientists a tool to examine the precision of the wavefront measurement.
The advantages of the new measurement method include ease of sample alignment, which can be achieved through remote phase measurement, the aberration causing object can be determined in spite of its distance from the focus and finally, it allows the measuring of the optics performance directly instead of the extrapolated performance obtained from other measurement methods.