We describe here the application of capacitance micrometry to the control of piezo scanned Fabry-Perot etalons using a closed loop feedback system. This system removes the problem of the non-linear response and hysteresis associated with piezo-electric transducers and allows precise control of both etalon gap and parallelism.
N K Reay,
T R Hicks,
P D Atherton,
"Servo-Control Of Fabry-Perot Interferometers I-Technique", Proc. SPIE 0445, Instrumentation in Astronomy V, (9 January 1984); doi: 10.1117/12.966119; https://doi.org/10.1117/12.966119