  Imaging-based detection of the motion of the levitated nanoparticles
complements a widely-used interferometric detection method, providing a precise
and robust way to estimate the position of the particle. Here, we show the
camera-based feedback cooling of a charged nanoparticle levitated in a linear
Paul trap. A charged nanoparticle levitated in a vacuum was observed by CMOS
camera systems. The nanoparticle images were processed in realtime with a
microcontroller integrated with a CMOS image sensor. The phase-delayed position
signal was fed-back to one of the trap electrodes resulting in the velocity
damping cooling. Our study provides a simple and versatile approach applicable
for control of low-frequency mechanical oscillators.
