Use of extended and prepared reference objects in experimental Fourier transform x-ray holography

The use of one or more gold nanoballs as reference objects for Fourier transform holography (FTH) is analyzed using experimental soft x-ray diffraction from objects consisting of separated clusters of these balls. The holograms are deconvoluted against ball reference objects to invert to images, in combination with a Wiener filter to control noise. A resolution of ∼30nm, smaller than one ball, is obtained even if a large cluster of balls is used as the reference, giving the best resolution yet obtained by x-ray FTH. Methods of dealing with missing data due to a beamstop are discussed. Practical prepared objects which satisfy the FTH condition are suggested, and methods of forming them described.