Laser-based fluorescence techniques for measuring thin liquid films

Abstract Laser-based systems for measuring the thickness of thin lubricant films by fluorescence assay are described. The laser illumination systems are simpler in design than earlier versions based on a mercury lamp; they also have a longer working distance and enable the technique to be applied to a wider range of practical situations. A variant using blue laser light had many advantages over an equivalent UV system. The behaviour of oil films in the laser light was studied, and blended fluids were developed to enable the fluorescence activity to be tailored to requirements.