Eur. Phys. J. E (2016) 39: 14
https://doi.org/10.1140/epje/i2016-16014-9

Regular Article

Local determination of thin liquid film profiles using colour interferometry

¹ School of Chemistry, Monash University, 3800, Clayton, Australia
² School of Physics, Monash University, 3800, Clayton, Australia

^* e-mail: rico.tabor@monash.edu

Received: 22 June 2015
Revised: 4 November 2015
Accepted: 4 November 2015
Published online: 25 February 2016

Abstract

We explore theoretically the interference of white light between two interfaces as a function of the optical conditions, using separately: a) idealised conditions where the light is composed of three discrete wavelengths; b) a more typically experimentally realisable case where light comprises a sum of three Gaussian wavelength distributions; and c) unfiltered white light from a broadband source comprising a broad distribution of wavelengths. It is demonstrated that the latter case is not only optically simple to arrange, but also provides unambiguous absolute separation information over the range 0-1μm --a useful range in studies of cell adhesion, thin liquid films and lubrication-- when coupled to detection using a typical colour camera. The utility of this technique is verified experimentally by exploring the air film between a cylinder and surface, as well as arbitrary liquid films beneath air bubbles that are interacting with solid surfaces.