DOUBLE RESOLUTION IMAGING OF WEAK PHASE SPECIMENS WITH QUADRANT DETECTORS IN THE STEM

A scheme is presented as an extension of the work by Burge and van Too rn [Scanning Electron Microsc. I (1980) 81-91] that call reconstruct t he phase of the specimen function to double the conventional bright fi eld resolution. The technique uses images obtained from quadrant detec tors in a scanning transmission electron microscope (STEM), for a thin weak phase object with coherent illumination. The reconstruction meth od assumes no knowledge of the state of the probe-forming lens. It is shown that the reconstruction is not critically sensitive to noise or to defocus and astigmatism in the probe forming lens, and that the val idity of the assumptions made for the purposes of the reconstruction c an be independently verified from the collected data.