High bandwidth force estimation for optical tweezers

Sehgal, Hullas; Aggarwal, Tanuj; Salapaka, Murti V.
April 2009
Applied Physics Letters;4/13/2009, Vol. 94 Issue 15, p153114
Academic Journal
A prevalent mode of optical tweezers involves position clamping that regulates a constant position of a trapped bead. Traditional schemes employ the measured bead position in the open loop or the control signal in the position-clamp mode as an estimate of external force on the trapped bead. This article shows that traditional methods introduce fundamental limitations on bandwidth of the external force estimation. A method is presented that leads to an order of magnitude increase in the bandwidth of the external force estimation. Furthermore, a comprehensive modeling paradigm is introduced that facilitates estimation of forces on the bead.


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