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Lecture

Lens Aberrations: Spherical, Chromatic, Astigmatism

In course

MSE-450: Electron microscopy: advanced methods

With this course, the student will learn about advanced methods in transmission electron microscopy, especially what is the electron optical setup involved in the acquisition, and how to interpret the data. After the course, students will be able to unders ...

Description

This lecture covers the main relevant aberrations found in lenses, including spherical aberration characterized by its coefficient Cs, chromatic aberration characterized by its coefficient Cc, and astigmatism affecting the focal length in two perpendicular directions of the lens. Historical notes on lens aberrations are also discussed.

In MOOC

Transmission Electron Microscopy for Materials Sciences

Instructors (2)

Duncan Thomas Lindsay Alexander

Duncan Alexander graduated with a PhD in Materials Science and Metallurgy at the University of Cambridge in 2003 for a thesis on the kinetics of metallurgical phase transformations under the direction of Lindsay Greer. From 2003 to 2007 he held a Royal Society Overseas Research Fellowship at the University of Sydney, and then post-doctoral positions at the University of Cambridge and Arizona State University, working first on materials electrochemistry with Carsten Schwandt and Derek Fray, and then the characterization of atmospheric aerosol particles with Peter Crozier and Jim Anderson. In 2007 he came to EPFL as a scientific collaborator in the group of László Forró, and from 2008 to 2017 he was a staff scientist at EPFL’s Interdisciplinary Centre for Electron Microscopy (CIME), specializing in the application of advanced transmission electron microscopy techniques and enabling electron microscopy research activities for groups across EPFL through teaching, training and support. In 2018 he joined the Electron Spectrometry and Microscopy Laboratory (LSME) as a full-time research scientist dedicated to advancing transmission electron microscopy techniques, and was promoted to the status of Research and Teaching Associate. In 2019, together with LSME director Cécile Hébert, he launched the first MOOC on transmission electron microscopy for materials science: https://www.coursera.org/learn/microscopy/For a complete list of peer-reviewed publications, see:https://orcid.org/0000-0003-4350-8587

Cécile Hébert

Cécile Hébert was born in France in 1970. She obtained her Ingeneer degree (physics) and her PhD degree (design of a new energy filter for transmission electron microscopy, under the direction of Prof. B. Jouffrey) at the Ecole Centrale in Paris. As a post doc with Prof. P. Schattschneider, she was working on the calculation of the fine structure of ionisation edges in EELS. As a research assistant at the Vienna University of Technology, she was one of the main participant to the CHIRALTEM project dealing with the measurement of magnetic circular dichroism in the electron microscope.

Official source

Ontological neighbourhood

Physics

Optics: Geometrical optics

Related concepts (27)

Optical aberration

In optics, aberration is a property of optical systems, such as lenses, that causes light to be spread out over some region of space rather than focused to a point. Aberrations cause the image formed by a lens to be blurred or distorted, with the nature of the distortion depending on the type of aberration. Aberration can be defined as a departure of the performance of an optical system from the predictions of paraxial optics.

Lens

A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. Lenses are made from materials such as glass or plastic and are ground, polished, or molded to the required shape. A lens can focus light to form an , unlike a prism, which refracts light without focusing.

Spherical aberration

In optics, spherical aberration (SA) is a type of aberration found in optical systems that have elements with spherical surfaces. Lenses and curved mirrors are prime examples, because this shape is easier to manufacture. Light rays that strike a spherical surface off-centre are refracted or reflected more or less than those that strike close to the centre. This deviation reduces the quality of images produced by optical systems. The effect of spherical aberration was first identified by Ibn al-Haytham who discussed it in his work Kitāb al-Manāẓir.

Cryogenic electron microscopy

Cryogenic electron microscopy (cryo-EM) is a cryomicroscopy technique applied on samples cooled to cryogenic temperatures. For biological specimens, the structure is preserved by embedding in an environment of vitreous ice. An aqueous sample solution is applied to a grid-mesh and plunge-frozen in liquid ethane or a mixture of liquid ethane and propane. While development of the technique began in the 1970s, recent advances in detector technology and software algorithms have allowed for the determination of biomolecular structures at near-atomic resolution.

Transmission electron microscopy

Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a sensor such as a scintillator attached to a charge-coupled device.

Related lectures (34)

Electron Microscopy: Techniques, Components, and Applications

Covers electron microscopy techniques, components, and applications, including historical development, lens aberrations correction, and electron interaction with matter.

Aberration Correction in HRTEM

Explains the principles of HRTEM, including contrast transfer, lenses, and aberration correction.

Microscopic Analyses & Electron Sources

Covers microscopic analyses using optical and electron microscopy, as well as electron sources.

TEM Components and Operation

Explores the components and operation of a Transmission Electron Microscope (TEM), including vacuum systems, electron sources, lenses, aberrations, and detectors.

Transmission electron microscopy: History and Aberration Correction