Four Stage E.M. for Phase Contrast and Strioscopic Microscopy

Abstract

Phase contrast electron microscopy should allow visualization of unstained biological structures. In an attempt to achieve this, we have modified a Siemens Elmiskop la microscope, in a way similar to that described by Faget, et al. (Proc. Fifth Int. Congr. Electron Microscopy, Philad., 1962, Abstract A-7). A number of phase contrast and strioscopic arrangements can be tested. A section consisting of phase plate chamber and additional intermediate lens (I2) was added to the column between the standard intermediate lens (I1) and the projector lens (Fig. 1). I1 was set, so as to project the back focal plane of the objective to the level of the phase plate holder (Fig. 2). I2 supplied final magnifications from 1,000 x to 80,000 x. Resolution was better than 15 Å. Two stigmators were used, one in the objective back focal plane and one in the plane of the phase plate. The source consisted of either a hairpin- or point- filament to allow variable coherence of illumination.