Measuring the accuracy of particle position and force in optical tweezers using high-speed video microscopy

Opt Express. 2008 Sep 15;16(19):14561-70. doi: 10.1364/oe.16.014561.


We assess the performance of a CMOS camera for the measurement of particle position within optical tweezers and the associated autocorrelation function and power spectrum. Measurement of the displacement of the particle from the trap center can also be related to the applied force. By considering the Allan variance of these measurements, we show that such cameras are capable of reaching the thermal limits of nanometer and femtonewton accuracies, and hence are suitable for many of the applications that traditionally use quadrant photodiodes. As an example of a multi-particle measurement we show the hydrodynamic coupling between two particles.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Equipment Failure Analysis / instrumentation*
  • Equipment Failure Analysis / methods
  • Image Interpretation, Computer-Assisted / instrumentation*
  • Image Interpretation, Computer-Assisted / methods*
  • Microscopy, Video / instrumentation*
  • Microscopy, Video / methods*
  • Motion
  • Optical Tweezers*
  • Particle Size
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Stress, Mechanical