Abstract: Preferably a sensor receives a print image from an authorized person to form a template, and from a candidate to form test data. Power spectral density (PSD) data for the template and candidate are compared, to read out rotation & dilation; these are used to adjust the template or candidate preparatory to a correlation to find translation. After applying the translation, and refinement of the rotation and dilation, normalized spatial correlation values (NSCVs) are used as a measure of quality of the match—and thresholded to make an early rejection or acceptance decision in very clear cases. Where the question is closer, isomorphic adjustment is applied to the entire template or candidate for a fairer comparison in their overlap area. Such comparison proceeds by the same type of PSD analysis—but for multiple subregions in the overlap area. Resulting NSCVs are averaged to obtain a measure of quality of the match, which again is thresholded for a final decision in the closer cases.

Abstract: Preferably a sensor receives a print image from an authorized person to form a template, and from a candidate to form test data. Power spectral density (PSD) data for the template and candidate are compared, to read out rotation & dilation; these are used to adjust the template or candidate preparatory to a correlation to find translation. After applying the translation, and refinement of the rotation and dilation, normalized spatial correlation values (NSCVs) are used as a measure of quality of the match—and thresholded to make an early rejection or acceptance decision in very clear cases. Where the question is closer, isomorphic adjustment is applied to the entire template or candidate for a fairer comparison in their overlap area. Such comparison proceeds by the same type of PSD analysis—but for multiple subregions in the overlap area. Resulting NSCVs are averaged to obtain a measure of quality of the match, which again is thresholded for a final decision in the closer cases.

Abstract: An electron beam lithography machine comprises a movable support for a substrate, an electron beam column for providing an electron beam to scan the substrate, an optoelectronic monitoring system for monitoring the position of the substrate relative to the column axis, and a rigid mounting body for mounting the support and the column. Laser interferometers of the monitoring system are mounted in mutually fixed relationship on a rigid carriage which is supported relative to the body by rollable members. The rollable members rotatably bear against the walls of grooves in the body and in the carriage in such a manner that the carriage is secured against tilt relative to the body and limited deformation of the body, especially thermally induced expansion and contraction, is accommodated without alteration in the position of the interferometers relative to the axis.

Abstract: Electron microscope apparatus for electron beam microfabrication. A mounting is described for supporting at least the final lens assembly of an electron microscope column above the vacuum chamber which also provides a rigid mounting for a stage on which a substrate is located together with reflecting mirrors which co-operate with a laser interferometer system for measuring the distances moved by the stage and therefore the substrate in two orthogonal directions.To avoid unwanted movement between the mirrors and the interferometer heads, the latter are also carried by rigid support means on the underside of the mounting.The mounting may comprise a solid ring located in an aperture in the lid of the vacuum chamber.Alternatively, the mounting may comprise a rigid and reinforced plate forming the lid of the chamber, from the underside of which extend the rigid support means for the stage and interferometer heads.