Citation:
Charrett TOH, Bledowski IA, James SW, Tatam RP. (2014) Frequency division multiplexing for interferometric planar Doppler velocimetry. Applied Optics, Volume 53, Issue 20, July 2014, pp. 4363-4374
Abstract:
A new method of acquiring simultaneously the signal and reference channels used for interferometric
planar Doppler velocimetry is proposed and demonstrated. The technique uses frequency division multiplexing
(FDM) to facilitate the capture of the requisite images on a single camera, and is suitable for
time-averaged flow measurements. Furthermore, the approach has the potential to be expanded to allow
the multiplexing of additional measurement channels for multicomponent velocity measurement. The
use of FDM for interferometric referencing is demonstrated experimentally with measurements
of a single velocity component of a seeded axisymmetric air jet. The expansion of the technique to
include multiple velocity components was then investigated theoretically and experimentally to
account for bandwidth, crosstalk, and dynamic range limitations. The technique offers reduced
camera noise, automatic background light suppression, and crosstalk levels of typically <10%.
Furthermore, as this crosstalk is dependent upon the channel modulations applied, it can be corrected for in postprocessing.