User interaction with a display is detected substantially simultaneously using at least two cameras whose intersecting FOVs define a three-dimensional hover zone within which user interactions can be imaged. The formulation comprises comprising an effective amount of component I selected from the group consisting of alpha acids and beta acids and an effective amount of at least one component II selected from the group consisting of alpha acids, beta acids, essential oils, fats and waxes, with the proviso that component I and II are not the same compound. In an alternate embodiment, the ESC voltage is at least partially applied before striking of the plasma for processing the wafer. As a result, the shrinkage that may be caused by the bonding agent to destabilize the aligned optical parts is minimized and the alignments among the optical parts are preserved and can sustain under very high environmental stresses. Preferably, the histogram includes a first peak corresponding to a generally planar portion of the sample surface, and a second peak corresponding to the surface anomaly.