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Figure 3
(a) A clean diffraction pattern (right) is obtained by subtracting the background pattern (middle) from the raw diffraction pattern (left). The rectangular regions are used to determine the scaling factor. (b) LROI (left) and HROI (right) diffraction patterns are measured to enhance the dynamic range of the diffraction intensity. The size of the LROI pattern is typically around 200 × 200 pixels, and the acquisition time is ∼0.5 s per exposure with a few thousand exposures. The short exposure time is to reduce the missing intensity at the centre of the diffraction pattern which is critical in phase retrieval (Miao et al., 2005BB24). To measure the HROI pattern (1340 × 1300 pixels) the beamstop is further moved in to block the low-resolution intensity, allowing us to increase the exposure time up to minutes. To enhance the high-resolution signal, we usually accumulate tens of exposures to obtain a final HROI pattern.

Journal logoJOURNAL OF
SYNCHROTRON
RADIATION
ISSN: 1600-5775
Volume 18| Part 2| March 2011| Pages 293-298
https://doi.org/10.1107/S0909049510051733
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