Convertible scanning electron microscope

Claim 1

A convertible scanning electron microscope comprising an evacuated chamber surrounding an electron optical axis, an electron beam generating source at one end of the optical axis, a focusing lens along the axis, an objective lens following the focusing lens along the axis, a first specimen holder stage arranged to hold a transmission specimen within the objective lens, a second specimen holder stage Arranged to hold a specimen spaced beyond the objective lens along the axis, a deflection system comprising a deflection means disposed along the axis between the focusing and objective lenses and a means for detecting and displaying signals detected and converting them into a scanning electron image of either the transmitted electrons from the transmission specimen or the emitted electrons from the secondary electron specimen, the said objective lens having an excitation power supply adjustable to provide an adjustable focal length such that the electron beam can be focused on the transmission specimen or alternately on the secondary electron specimen such that in a transmission scanning mode, the focusing lens and objective lens focus the electron beam upon the specimen, and the objective lens also serves as a first image forming lens, and such that in a secondary electron scanning mode, the focusing lens and objective lens serve to focus the electron beam upon the sample.