Fig. 1.

Principle of fast confocalized single-molecule tracking. (A) Optical arrangement. Fluorescence excited in the focal region is imaged onto a quasi-confocal detection area of three densely packed fibers. Signals from the connected three avalanche photodiodes (APDs) are recorded in a single-photon counting mode. (B) Reference map encoding the relative distribution of photon counts on the three detectors for a fluorescent object as a function of position (x,y). This map was obtained by scanning a 40 nm fluorescent bead over a 500 nm × 500 nm observation region and combining the count information on all three channels. Colors denote detector affiliations.