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. Author manuscript; available in PMC: 2010 Jan 22.
Published in final edited form as: Opt Express. 2009 Apr 13;17(8):6209–6217. doi: 10.1364/oe.17.006209

Fig. 3.

Fig. 3

Position clamp efficiency (a) (Media 2) A sinusoidal drag force is applied to 10 trapped beads with holographic optical tweezers. Nine beads are position-clamped (Gp = 0.3) and one is in a stationary trap (Gp = 0) (bottom center). The arrows represent the error, xbead(t) − xset point(t). Movie: sped up 5 times, 39 × 22 μm. (b) Bead displacements (green), trap positions (red) and setpoint positions (blue). (c) Power spectral density of the position-clamped beads relative to the power spectral density of the reference bead (different color points for different beads, solid line: model for our experiment, dashed line: model for a 30 Hz feedback loop).