  This book chapter reviews progress in crystallographic image processing (CIP)
for scanning probe microscopy (SPM) that has occurred since our description of
the technique was first put into open access in this book series in the year
2010. The signal to noise ratio in all kinds of experimental images of more or
less regular 2D periodic arrays is significantly enhanced by CIP and the
technique is independent of the type of recording device. In the SPM imaging
context, CIP can be understood as an a posteriori sharpening of the effective
experimental scanning probe tip by computational means. It is now possible to
remove multiple scanning probe mini-tip effects in images from 2D periodic
arrays of physical objects that either self-assembled or were created
artificially. Accepted within the scientific community is by now also the fact
that SPM tips can change their shape and fine structure during the operation of
a microscope and, thereby, obfuscate the recorded images in systematic ways.
CIP restores much of the smeared out information in such images. The adaptation
of a geometric Akaike Information Criterion from the robotics and computer
vision community to the unambiguous detection of 2D translation symmetries
enabled much of our recent progress. In the main body of this book chapter, we
discuss this adaptation and briefly illustrate its utility on an example.
