title: A method for producing hollow cone illumination electronically in the conventional transmission microscope.
abstract: An electronic device manipulates the primary beam in the conventional transmission microscope to produce a hollow cone of illumination with its apex located at the specimen. The device uses the existing tilt coils of the microscope, and modulates the D.C. signals to both x and y tilt directions simultaneously with various waveforms to produce Lissajous figures in the back-focal plane of the objective lens. Electron diffraction patterns can be recorded which reflect the manner in which the direct beam is tilted during exposure of a micrograph. In the bright-field imaging mode the device provides a microscope transfer function without zeros in all spatial directions and has been used to obtain high resolution images which are also free from the effect of chromatic aberration. A standard second condenser aperture is employed and the width of the cone annulus is readily controlled by defocusing the second condenser lens. The cone azimuthal angle is also controlled electronically; hence the device can also be used in the dark-field imaging mode. This device has been applied to imaging both amorphous and crystalline materials including biomolecular specimens.
mesh_terms: D002244:Carbon; D004279:DNA, Viral; D005857:Germanium; D006046:Gold; D008029:Lighting / Q000379:methods*; D008854:Microscopy, Electron; D008968:Molecular Conformation; D009690:Nucleic Acid Conformation; D013539:Simian virus 40
chemical_list: D004279:DNA, Viral; D005857:Germanium; D002244:Carbon; D006046:Gold