WORMALD, S.A. and COUPLAND, J.M., 2010. On measuring 3D flow within inkjet droplet streams using a digital holographic microscope. Journal of Modern Optics, 57 (9), pp.700-708.
With a view to measuring the internal and external flow fields in an inkjet droplet stream,
this paper discusses the problem of imaging through droplet surfaces and more generally
interfaces in two-phase flows. First the propagation of optical fields through interfaces
between media of different refractive index is discussed with reference to scalar
diffraction theory. Some approximations suitable for droplet imaging are then discussed
and the use of a-priori information is then explained. The imaging technique is applied to
holograms recorded using a digital holographic microscope and is illustrated in the
synthesis of a 3D image that is reconstructed through a cylindrical telecommunication
fibre. Subsequently we demonstrate for the first time, high resolution imaging throughout
an inkjet droplet. The practical implementation and improvement of these imaging
methods for the measurement of two-phase flows is then discussed.
This article was accepted for publication in the Journal of Modern Optics and the definitive version is available at: http://dx.doi.org/10.1080/09500340903580781