title: Real-time detection and single-pass minimization of TEM objective lens astigmatism.
abstract: Minimization of the astigmatism of the objective lens is a critical daily instrument alignment task essential for high resolution TEM imaging. Fast and sensitive detection of astigmatism is needed to provide real-time feedback and adjust the stigmators to efficiently reduce astigmatism. Currently the method used by many microscopists is to visually examine the roundness of a diffractogram (Thon rings) and iteratively adjust the stigmators to make the Thon rings circular. This subjective method is limited by poor sensitivity and potentially biased by the astigmatism of human eyes. In this study, an s2power spectra based method, s2stigmator, was developed to allow fast and sensitive detection of the astigmatism in TEM live images. The "radar"-style display provides real-time feedback to guide the adjustment of the objective lens stigmators. Such unique capability allowed us to discover the mapping of the two stigmators to the astigmatism amplitude and angle, which led us to develop a single-pass tuning strategy capable of significantly quicker minimization of the objective lens astigmatism.
authors.affiliation: Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Rui
authors.initials: R
authors.lastname: Yan
authors.affiliation: Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: Kunpeng
authors.initials: K
authors.lastname: Li
authors.affiliation: Markey Center for Structural Biology, Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA. Electronic address: jiang12@purdue.edu.
authors.forename: Wen
authors.initials: W
authors.lastname: Jiang
mesh_terms: D000465:Algorithms; D020285:Cryoelectron Microscopy / Q000379:methods*; D006801:Humans; D046529:Microscopy, Electron, Transmission / Q000295:instrumentation* / Q000379:methods*; D008962:Models, Theoretical; D059629:Signal-To-Noise Ratio
keywords: Astigmatism correction; Objective lens stigmators; Real-time feedback; Single-pass tuning strategy; cryo-EM; “Radar”-style display