A visit to the TRW demo just happened to have a 100mW laser and he beamed the laser into the fan blades during the demo. This had the unexpected effect of showing the amplitude of fan blade deflection as the beam would go from a spot to a line the length of roughly maximum blade deflection. If we could take that beam length and clock it out against a time axis, we’d reproduce the input signal perfectly.
now for a couple of YouTube videos made during the same AES demo. Notice the laser modulating it’s reflection against the moving fan blades.