Aplanatic imaging systems for the transmission electron microscope

During the last decade aberration correctors have become a well-accepted tool in high-resolution transmission electron microscopy. The available correctors compensate for the spherical aberration Cs of the imaging system. Recently, for instruments with considerably improved information limit also the off-axial aberrations have attracted more attention since these aberrations limit the high-resolution field of view. We have proposed a novel hexapole-type Cs/B3-corrector which corrects for the spherical aberration and the off-axial coma of the imaging system. We discuss the assessment and correction of off-axial aberrations and report about the optical performance of the first prototype instrument.