Dresden 2011 – scientific programme

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BP: Fachverband Biologische Physik

BP 12: Posters: New Technologies

BP 12.17: Poster

Monday, March 14, 2011, 17:15–20:00, P3

Real-time 3-dimensional particle tracking with sub-nanometer accuracy at 5,000 frames per second — •Alexander Huhle, Sihwa Joo, Daniel Klaue, and Ralf Seidel — Biotechnologisches Zentrum, TU Dresden, Tatzberg 47/49, 01307 Dresden

Tracking the position of single spherical micrometer-sized particles in all 3 dimensions is crucial for modern force sensing techniques, such as optical and magnetic tweezers. It can be realized using either position sensitive devices in combination with focused laser illumination or a camera and wide-field illumination. While camera-based detection is very simple to implement and offers the attractive possibility to determine the positions of many particles in parallel, real-time tracking rates have so far been limited to several tens of frames per second due to the high computational effort of the employed software routines. Here we demonstrate 3 dimensional real-time tracking at 5,000 frames per second with sub-nanometer accuracy using a fast CMOS camera for image acquisition and employing GPU based computing. Computationally demanding parts of the tracking algorithm are carried out in the GPU that is specialized for highly parallelized execution. Tracking of the lateral particle positions is obtained by cross-correlating the image with its mirror image. The axial position is obtained from the radial intensity profile of the particles diffraction pattern when imaged in overfocus. High tracking rates are crucial to overcome the shot-noise limitations of camera-based detection at the second time scale and to resolve fast, dynamic processes.