The present invention provides a technique capable of suppressing variations in the height of each solder ball where an NSMD is used as a structure for each land. The method further includes exposing L sets of N tracks onto the medium with an offset of M pixels in a slow scan direction substantially perpendicular to the fast scan direction, according to a second corresponding part of imaging data. Improved measurements near the edge of the sample can be obtained by rotating the wafer with respect to the measurement spot to ensure that the short axis of the ellipse is perpendicular to the wafer edge. A master processor manages the generation of the plaintextcyphertext pairs. In addition, more than one membrane may be provided between each indicia, wherein each membrane may respond to a different environment.