Near, far, wherever you are: simulations on the dose efficiency of holographic and ptychographic coherent imaging. Issue 3 (27th May 2020)

• Record Type: Journal Article
• Authors: Du, Ming; Gürsoy, Dogˇa; Jacobsen, Chris
• Is Part Of: Journal of applied crystallography. Volume 53:Issue 3(2020)
• Page Start: 748
• Page End: 759
• Publication Date: 2020-05-27
• Subjects: X‐ray microscopy -- radiation dose -- ptychography -- holography; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576720005816
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : Different studies in X‐ray microscopy have arrived at conflicting conclusions about the dose efficiency of near‐ and far‐field imaging approaches. X‐ray far‐field ptychography is compared with near‐field holography and near‐field ptychography in computer simulations. All three methods are highly dose efficient, with far‐field ptychography offering slightly better low‐dose imaging characteristics. Abstract : Different studies in X‐ray microscopy have arrived at conflicting conclusions about the dose efficiency of imaging modes involving the recording of intensity distributions in the near (Fresnel regime) or far (Fraunhofer regime) field downstream of a specimen. A numerical study is presented on the dose efficiency of near‐field holography, near‐field ptychography and far‐field ptychography, where ptychography involves multiple overlapping finite‐sized illumination positions. Unlike what has been reported for coherent diffraction imaging, which involves recording a single far‐field diffraction pattern, it is found that all three methods offer similar image quality when using the same fluence on the specimen, with far‐field ptychography offering slightly better spatial resolution and a lower mean error. These results support the concept that (if the experiment and image reconstruction are done properly) the sample can be near or far; wherever you are, photon fluence on the specimen sets one limit to spatial resolution.