POEM: A fast defocus estimation method for scanning transmission electron microscopy

The defocus polar rose estimation method (POEM) is introduced here as an alternative method for defocus estimation in scanning transmission electron microscopy. Its principle of operation is discussed in detail along with the results of initial simulation-based performance tests. The results show that POEM can attain a precision similar to that of equivalent methods in the literature but using significantly less data, thus increasing the defocus estimation speed significantly.