]> 2026-04-04T16:36:54+02:00 Publications:Fast tracking of point-symmetric objects 500 en <p>A point-symmetry function based on autoconvolution is described which makes it possible to track the position of point-symmetric objects with sub-pixel accuracy. The method is insensitive to grey level and was developed in order to have a fast and robust algorithm for real-time tracking of small magnetic particles in a light microscopc. The phase contrast microscope image of the 4.5 mu m diameter spherical particle consisted of concentric light and dark fringes where the shape of the fringes were dependent on the focus. The position of the particle could be monitored in real-time at 25 Hz with a lateral accuracy of +/- 20 nm corresponding to less than +/- 0.1 pixel. To determine the vertical or z-position a new parameter was defined representing a measure of the second derivative of the intensity function. The vertical position could thus be determined with an accuracy of +/-50 nm. The magnetic particle could be tracked acid guided by applied magnetic fields to remain in a fixed position or programmed to scan either horizontal or vertical surfaces. Forces down to 10(-14) N could be measured by monitoring the applied magnetic forces. One and two-dimensional Brownian motion could be studied by regulating the particle to a fixed z-position and monitoring the lateral position.</p> 2nd IS&T/SPIE Conference on Real-Time Imaging, San Jose, CA, USA, 10 February 1997 http://dx.doi.org/10.1117/12.270349 http://hh.diva-portal.org/smash/record.jsf?searchId=1&pid=diva2:544796 47 Real-time imaging II : 10 February, 1997, San Jose, California Conference Paper Proceedings of SPIE - The International Society for Optical Engineering ; 3028 38 Fast tracking of point-symmetric objects 3028 1997 2016-09-30T20:41:25Z 2457662.3620949 Fast tracking of point-symmetric objects 500 0 plainlist list 1 [[:Publications:Fast tracking of point-symmetric objects]] Fast tracking of point-symmetric objects# QUERYc3134407de65059b559e24e164dfa747 500 [2,"smw-datavalue-property-restricted-annotation-use","Publisher"] Fast tracking of point-symmetric objects# ERR6c155b5d70b69ddb590b4f2e73389c2a 500 [2,"smw-datavalue-property-restricted-annotation-use","Author"] Fast tracking of point-symmetric objects# ERRe24f17e090c98448f3de99d03182b7b6