= AFM tip-convolution artefact
{c}
A distortion caused by the finite shape or multiple contact points of a scanning tip. For a single-valued sample height $h$ and a tip profile $t$ measured upward from its apex, nonpenetration requires the indicated apex height to satisfy $z(x)\geq h(u)-t(u-x)$ for every $u$. The ideal accessible envelope is consequently $z(x)=\max_u[h(u)-t(u-x)]$. This geometric operation is distinct from an ordinary linear convolution and from feedback lag.
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