Hitachi, Ltd.

Hitachi Naka Seiki, Ltd.

Junichiro Tomizawa

Susumu Ozasa

A focusing apparatus of electron microscope for focusing an electron beam through a focusing lens onto a sample, having a deflecting means for making the electron beam scan on the sample, an astigmatism correcting means of the electron beam, a detecting means for detecting the 2nd electrons from the sample when the sample is scanned by the electron beam, and an optimum exciting current determining means of the focusing lens. The optimum exciting current is obtained by determining the position of the centroid of an area surrounded by a curve Y=f (I) and a fixed straight line. The curve Y shows the relationship between the exciting current for the focusing lens and an electron beam radius corresponding signal which is obtained on the basis of a signal from the detecting means and inversely corresponds to a radius of the electron beam on the surface of the sample. The focusing apparatus enable the exact and simple determination of the optimum exciting current for the focusing lens corresponding to the circle of least confusion.

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Katsuta, Japan

Junichiro Tomizawa