Background: The high-resolution X-ray imaging system employing synchrotron\nradiation source, thin scintillator, optical lens and advanced CCD camera can achieve\na resolution in the range of tens of nanometers to sub-micrometer. Based on this\nadvantage, it can effectively image tissues, cells and many other small samples,\nespecially the calcification in the vascular or in the glomerulus. In general, the\nthickness of the scintillator should be several micrometers or even within\nnanometers because it has a big relationship with the resolution. However, it is\ndifficult to make the scintillator so thin, and additionally thin scintillator may greatly\nreduce the efficiency of collecting photons.\nMethods: In this paper, we propose an approach to extend the depth of focus\n(DOF) to solve these problems. We develop equation sets by deducing the\nrelationship between the high-resolution image generated by the scintillator and the\ndegraded blur image due to defect of focus first, and then we adopt projection onto\nconvex sets (POCS) and total variation algorithm to get the solution of the equation\nsets and to recover the blur image.\nResults: By using a 20 �¼m thick un matching scintillator to replace the 1 �¼m thick\nmatching one, we simulated a high-resolution X-ray imaging system and got a\ndegraded blur image. Based on the algorithm proposed, we recovered the blur\nimage and the result in the experiment showed that the proposed algorithm has\ngood performance on the recovery of image blur caused by un matching thickness\nof scintillator.\nConclusions: The method proposed is testified to be able to efficiently recover the\ndegraded image due to defect of focus. But, the quality of the recovery image\nespecially of the low contrast image depends on the noise level of the degraded\nblur image, so there is room for improving and the corresponding denoising\nalgorithm is worthy for further study and discussion.
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