Improving the spatial resolution of real-time radiography images using the maximum entropy method

The authors have evaluated the maximum-entropy method (MEM) as a technique to improve the spatial resolution of real-time radiography images. The point spread function (PSF) of the image intensifier was estimated by differentiating a high-resolution scan made by translating the edge of a lead plate in subpixel increments relative to a single pixel of the CCD (charge coupled device) video camera. The 1D PSF was rotated to form the 2D PSF, which was used as the system function for the MEM algorithm. Improvement in the restored image was evaluated quantitatively using a resolution gauge. MEM was found to increase the contrast of the resolution gauge over the visible range of the digitized image by as much as 8 dB. Furthermore, the MEM smoothed the image noise, restored the square-wave pattern, and did not generate significant artifacts