CanvasFormat.cv5 Motion sensors obviously cannot read DC, and loose sensitivity as Frequency squared below their resonance frequency. For a 1cm displacement, this corresponds to 5Hz. It may be possible to design spring systems with mechanical advantages that do not require a very long spring to obtain a low resonant frequency. For a properly designed system, the mechanical noise will be dominated by thermal effects. This corresponds to 0.1nm for 1Kg with a 1Hz resonant frequency.
Capacitive sensors are probably the easiest of implement.
It is believed that substantial noise improvements are possible with some electronics modifications. It is designed with a resonant frequency of 5Hz, with the assumption that the electron beam can provide position information at lower frequencies. An electrostatic fine adjust with a 100 micron range is provided for fine offset adjust. The most serious limitation to the measurement will be the excitation of higher order modes in the sensor. A full dynamic analysis will be required to evaluate this effect.