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

Area of Science:

• Electron microscopy
• Materials science
• Imaging techniques

Background:

• Integrated Centre-of-Mass (iCOM) is a standard phase-contrast imaging method using 4D Scanning Transmission Electron Microscopy (STEM).
• Existing methods face limitations with residual aberrations and noise in STEM datasets.

Purpose of the Study:

• Introduce Side Band masked Centre-of-Mass (SBm-COM) and integrated Centre-of-Mass (SBm-iCOM) for weak-phase object imaging.
• Improve aberration compensation and noise reduction in 4DSTEM.
• Enhance low-frequency information transfer in phase-contrast imaging.

Main Methods:

• Combine Single-Side Band (SSB) ptychography with Centre-of-Mass (COM) and iCOM principles.
• Develop SBm-COM and SBm-iCOM for analyzing 4DSTEM datasets.
• Implement aberration compensation and noise filtering up to the 2α resolution limit.

Main Results:

• SBm-(i)COM effectively compensates for residual aberrations in 4DSTEM data.
• Noise contribution is significantly reduced, improving image quality.
• The method is suitable for samples difficult to focus or requiring low electron dose.
• SBm-iCOM provides an intrinsic transfer function that boosts low-frequency information.

Conclusions:

• SBm-(i)COM offers a novel and effective approach for phase-contrast imaging in 4DSTEM.
• This method enhances imaging capabilities for challenging samples and low-dose conditions.
• SBm-iCOM presents advantages in low-frequency information retrieval compared to standard SSB ptychography.