On the limits of digital video microscopy

Abstract

We explore the limits of digital video microscopy which is established as a standard method in physics, chemistry and biology. At particle distances close to contact we observe small but systematic deviations between the optically measured and the real particle distances. This difference is caused by the overlap of the optical images between neighboring particles. Exemplarily we discuss the consequences of this effect on pair potential measurements of charge stabilized colloids in confined geometries.