Real-Time Holographic Tracking and Control of Microrobots

Digital holography is used to track the three-dimensional position of a magnetic microrobot maneuvered in real time by means of an electromagnetic manipulation system. The method presented is able to process holograms at 40 Hz with a position accuracy in the imaging plane and in depth of
$\pm$
23 and
$\pm$
180 
$\mu$
m, respectively. As this method does not require magnification, microrobots can be tracked in significantly larger working volumes than conventional optical methods. The performance of this tracking method is demonstrated by visually servoing a magnetic bead around a cubic trajectory.