Validation of a nonlinear reactive control law for three-dimensional particle tracking in confocal microscopy

A nonlinear control law for reactively tracking a diffusing fluorescent particle in three dimensions is reviewed and preliminary experimental results are presented. The control law, originally derived in the context of exploring scalar potential fields, converges to a volume around the maximum of the point spread function of a confocal microscope using very little information of the underlying structure of the field. Experimental results show the control law can track particles with diffusion coefficients over 3 μm²/s with moderate excitation intensities.