Digital imaging for high-resolution electron holography

Abstract

It is a goal of electron microscopy to eliminate film as the recording medium for electron microscope images in favor of direct digital recording. At present, there are commercially available digital TV systems (e.g. ref. [2]) based on CCD slow scan technology that provide 1M pixel images (i.e. 1k × 1k arrays). Such systems have proven useful for recording standard high resolution images and are sufficient to replace film for most standard electron microscopy. However, the newly developing technique of electron holography requires an advanced digital imaging capability, because the process of reconstruction of amplitude and phase images from a hologram necessarily gives final images that are only one-quarter the size of the original image. For a minimum desired 512 × 512 pixel reconstructed image, the original image should be 2k × 2k, requiring a CCD array with 4M pixels. Electron holograms which are recorded for reconstruction of aberration-corrected images with improved resolution (approaching 0.1 nm) require hologram fringes spaced on the order of 0.3 nm.