Faulty human eyesight can be corrected with glasses, but it's a different matter to fix vision problems that afflict instruments used by scientists who explore the microcosmos. Two Oregon scientists conducting research with National Science Foundation (NSF)-support, however, have found a way to do it. As with many problems in human eyesight, the culprit in the world of microscopes is the lens.
In devices such as electron microscopes that display highly magnified images of specimens, a beam of electrons passes through a focusing lens. In doing so, the beam suffers two kinds of distortions: chromatic and spherical. These aberrations limit the devices' resolving power.
"But now we have developed a new tool to correct the aberrations," says O. Hayes Griffith, a University of Oregon scientist who collaborated on the investigation with Portland State University physicist Gertrude Rempfer. It was supported by NSF's division of biological infrastructure. Griffith, Rempfer and an interdisciplinary team of Oregon scientists used an electron mirror to cancel the unwanted aberrations caused by the lens.
The improvement, described in the January/February issue of Microscopy and Microanalysis, will lead to practical applications such as reduced size for miniature electron probes and greater resolving power for instruments designed for use in the world of the very small.
"The most immediate application will be to emission electron microscopes, particularly those that will be built to equip new synchrotron light source facilities such as the Advanced Light Source in Berkeley and the Photon Factory in Japan," Griffith says. "These multimillion-dollar ring-shaped particle accelerators produce high intensity light. This light is used to study properties of surfaces. Improved electron optics are necessary to realize the full potential of the synchrotron facilities."
Scientists believe the increased intensity of a synchrotron light source provides new opportunities to study silicon, polymer, biological and catalytic surfaces.