Imaging system to monitor the pendulum mode of a vibrationally driven torsion balance

A digital-imaging system based on a personal computer was tested for its ability to track in real time periodic motion with a frequency near 1 Hz. When imaging a vibrationally isolated stationary target, the system displayed a limitation in positional measurement of 0.3 x 10(-6) m. Further tests indicate that this limitation arises from environmental vibrations driving the target, even though it is mounted on a vibration-isolation table. This work demonstrates the feasibility of using digital imaging to measure motions other than the (usually very low frequency) torsion motion of a torsion balance, where the ultimate goal is to remove the effects of these motions from the torsion signal of interest. (C) 1997 American Institute of Physics. [S0034-6748(97)01011-3].