Pattern average

Quality metric that is computed from the average 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.

\[Q = \frac{1}{W\cdot H} \sum\limits_{i=0}^{W}{\sum\limits_{j=0}^{H}{I_{ij}}}\]

where W is the width of the pattern, H is the height of the pattern and \(I_{ij}\) the pixel value at position (i, j).

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

• a measure of the overall backscatter yield
• related to surface topography
• show scratches, microtwins and small strain levels
• affected by contamination, gain, contrast settings and current drift

Example on NiCoCrAlY sample