Pattern standard deviation

Quality metric that is computed from the standard deviation of all the pixels in the diffraction pattern. The pixels with a value of zero are ignored, so that the pixels removed from the Mask disc operation are ignored.

\[Q = \sqrt{\frac{1}{WH-1}\sum\limits_{i=1}^W{\sum\limits_{j=1}^{H}{\left( I_{ij}-\bar{I} \right)^2}}}\]

where W and H are respectively the width and the height of the diffraction pattern, \(I_{ij}\) the intensity at pixel (i,*j*) and \(\bar{I})\) the average intensity of all the pixels.

This quality index was used by Wright and Nowell [Wright2006] and Tao and Eades [Tao2005]. They summarized this quality index as:

• Measure of the image contrast
• Affected by contamination, gain, contrast settings and noise

Example on NiCoCrAlY sample