A precision goniometer stage for the electron microscope

A goniometer stage of entirely new design has been built for the electron microscope. It has a number of features not hitherto applied to the construction of goniometer stages which make it particularly valuable in quantitative work. In the Siemens Elmiskop I microscope, the goniometer stage permits a tilt of ±12½° about any predetermined axis, whilst still retaining the full traverse of ±0.8 mm. The axis of tilting and the magnitude of the rotation may be set precisely without recourse to calculation. The stage also allows any number of accurate tilting operations to be employed consecutively without calculation, provided the vector sum of the tilts does not exceed 12½°. It is possible to extend the maximum angle of tilting, but the semi-immersion objective pole piece of the Elmiskop I and the type of translation movement used limit the maximum tilt to about ±20°. The area of the bearing surfaces employed is not restricted by the size of the pole piece. This allows large surfaces to be used giving a robust, precise instrument which will retain its accuracy and smoothness of motion for long periods.