Image Number 3 for United States Patent #4633085.
An electron microscope having plural stages of focusing lenses between an objective lens and an electron gun. The magnetic pole piece of the focusing lens of the final stage which is on the side of the objective lens takes a conic form which tapers toward the objective lens. The yoke of the objective lens on the side of the focusing lenses is centrally provided with a conic recess. This structure makes it possible to shorten the distance between the position of the magnetic field produced by an auxiliary lens and the front focal point defined by a front objective lens without introducing interference between the focusing lens of the final stage and the object lens proper. Thus, the observation of an electron micrograph covering a wide field of view facilitates accurate analysis of the physical properties of a designated microscopic region on a specimen.