Defocus correction and noise reduction using a hybrid ptychography and Centre‐of‐Mass algorithm

Integrated Centre-of-Mass (iCOM) is a widely used phase-contrast imaging method based on Centre-of-Mass (COM), which makes use of a 4D Scanning Transmission Electron Microscopy (STEM) dataset using an in-focus probe. In this paper, we introduce a novel approach that combines Single-Side Band (SSB) ptychography with COM and iCOM, termed Side Band masked Centre-of-Mass (SBm-COM) and integrated Centre-of-Mass (SBm-iCOM) which is applicable to weak-phase objects. This method compensates for residual aberrations in 4DSTEM datasets while also reducing the noise contribution up to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mn>2</mml:mn> <mml:mi>α</mml:mi></mml:mrow> <mml:annotation>$2\alpha $</mml:annotation></mml:semantics> </mml:math> resolution limit. The aberration compensation and noise filtering features make the SBm-(i)COM suitable for samples that are difficult to focus or those that require minimal electron fluence. SBm-iCOM transfers the same information as SSB ptychography but results in an intrinsic transfer function that enhances low-frequency information.