We describe a new electron-optical configuration for transmission
electron microscopy (TEM). In this novel mode, the objective
mini-lens is strongly excited so that the back focal plane of
the objective lens is imaged onto the plane of the selected-area
aperture with a magnification of 3.2. Thus, the selected-area
aperture can function as an objective aperture either in place
of or in addition to the conventional objective aperture. This
new configuration, which has been implemented on a JEOL 4000EX
high voltage electron microscope, provides improved resolution
and contrast in images of thick biological specimens and also
facilitates the use of beam tilt for stereo image acquisition.